Home » Public Forums » GMCnet » Upgrades are paying off
| Upgrades are paying off [message #210764] |
Wed, 12 June 2013 01:52  |
jtblank
Messages: 237
Registered: June 2007
Location: Tulare, CA
Karma: 1
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Senior Member |
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Just got back from my 300 mile round trip to Pismo Beach, CA and really am excited with the following last year's upgrades and maintenance items.
Re-insulated the ceiling with R-max sheet insulation, left last Friday temperature was 105, after cooling down the back with the roof a/c turned it off after 45 minutes, the rest of the journey was with dash only a/c and was very comfortable. Really could notice that the radiation of the heat was almost eliminated. Not till I got to Atascadero (120 miles) was the outside temp below 100, but the wife and I were cool.
Front and rear brake upgrades, used Jim K yellow sticky http://www.appliedgmc.com/prod.itml/icOid/598 and rear carbon metallic shoes http://www.appliedgmc.com/prod.itml/icOid/607. The front grab really well and no more squeaking coming to a stop. The rears were relined with the shoes and new spring kit, I also repacked both inner and outer bearing with Valvoline synthetic grease and new seals and new wheel cylinders. Upgraded the intermediate with 1 1/16", with all these changes I could really notice a BIG difference, the rear now seems to somewhat squat when braking and blend well with the increase stopping power of the sticky yellow front disc pads. I now know how bad the brakes were before..... Always had that feeling in traffic "hope it stops" but now if you hit the brakes hard if it ain't tied down its coming up front fast. I highly recommend both the sticky yellow disc pad and CM shoes Jim K has, I know that everyone is talking about the reaction arm system for the rear for both drum and disc conversions but with these excellent parts and proper adjustment you'll find a vast improvement over your "I hope" brakes.
Plug wires and K&N filter service, installed new Accel 8mm plug wires and serviced the K&N filter, since I travel the road twice annually I know what the max speed up certain grades, I noticed about 2-3 miles per hour faster climb, as a side note I averaged close to 9 miles per gallon which was an improvement of about 1 mpg.
PS hats off to Chuck Boyd for the brake shoe adjustment "ding" tip, no hot or sloppy brakes.
Never had a better trip can't wait for the next!
John Blankenship
'76 Palm Beach
Tulare, CA
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| Re: [GMCnet] Upgrades are paying off [message #211092 is a reply to message #210764] |
Fri, 14 June 2013 09:04  |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
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Senior Member |
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John, Thanks for the lowdown on non-disc rear brakes. If the proportioning valve limits pressure to the rear brakes then the larger intermediate wheel cylinder only redistributes the hydraulic force to the rear brakes. Kind of mimics the reaction arm at significantly lower cost.
JP
>________________________________
> From: John Blankenship <jtblank@yahoo.com>
>To: gmclist@temp.gmcnet.org
>Sent: Wednesday, June 12, 2013 2:52 AM
>Subject: [GMCnet] Upgrades are paying off
>
>
>
>
>Just got back from my 300 mile round trip to Pismo Beach, CA and really am excited with the following last year's upgrades and maintenance items.
>
>Re-insulated the ceiling with R-max sheet insulation, left last Friday temperature was 105, after cooling down the back with the roof a/c turned it off after 45 minutes, the rest of the journey was with dash only a/c and was very comfortable. Really could notice that the radiation of the heat was almost eliminated. Not till I got to Atascadero (120 miles) was the outside temp below 100, but the wife and I were cool.
>
>Front and rear brake upgrades, used Jim K yellow sticky http://www.appliedgmc.com/prod.itml/icOid/598 and rear carbon metallic shoes http://www.appliedgmc.com/prod.itml/icOid/607. The front grab really well and no more squeaking coming to a stop. The rears were relined with the shoes and new spring kit, I also repacked both inner and outer bearing with Valvoline synthetic grease and new seals and new wheel cylinders. Upgraded the intermediate with 1 1/16", with all these changes I could really notice a BIG difference, the rear now seems to somewhat squat when braking and blend well with the increase stopping power of the sticky yellow front disc pads. I now know how bad the brakes were before..... Always had that feeling in traffic "hope it stops" but now if you hit the brakes hard if it ain't tied down its coming up front fast. I highly recommend both the sticky yellow disc pad and CM shoes Jim K has, I know that everyone is talking about the
reaction arm system for the
> rear for both drum and disc conversions but with these excellent parts and proper adjustment you'll find a vast improvement over your "I hope" brakes.
>
>Plug wires and K&N filter service, installed new Accel 8mm plug wires and serviced the K&N filter, since I travel the road twice annually I know what the max speed up certain grades, I noticed about 2-3 miles per hour faster climb, as a side note I averaged close to 9 miles per gallon which was an improvement of about 1 mpg.
>
>
>PS hats off to Chuck Boyd for the brake shoe adjustment "ding" tip, no hot or sloppy brakes.
>
>Never had a better trip can't wait for the next!
>
>--
>John Blankenship
>'76 Palm Beach
>Tulare, CA
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| Re: [GMCnet] Upgrades are paying off [message #211112 is a reply to message #211092] |
Fri, 14 June 2013 23:34 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Jp,
Here's a link to a cross section of the combination valve which explains how it works. It not a proportioning valve, it does not
limit pressure to the rear brakes.
http://www.gmcmhphotos.com/photos/member-galleries/p37696-combination-valve-cros.html
Regards,
Rob M.
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Jp Benson
Sent: Friday, June 14, 2013 9:05 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Upgrades are paying off
John, Thanks for the lowdown on non-disc rear brakes. If the proportioning valve limits pressure to the rear brakes then the
larger intermediate wheel cylinder only redistributes the hydraulic force to the rear brakes. Kind of mimics the reaction arm at
significantly lower cost.
JP
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Upgrades are paying off [message #211195 is a reply to message #211112] |
Sat, 15 June 2013 20:44 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
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Senior Member |
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Rob,
Your right. It is a combination valve. I read the manual after you pointed out my error. I'm surprised that no one has pointed out what appears to be my other error.
Using different size wheel cylinders is an attempt to "tune" the braking force applied to each wheel to match the friction between the wheel and road. So larger intermediate wheel cylinder allocates greate force to the intermediate brake shoes. I would expect the forces to be proportional to the respective areas of the wheel cylinders.
The reaction arm on the other hand attempts to equalize tire friction by balancing the downward forces on all four wheels. So one would want wheel cylinders that were all the same.
These are two very different methods for preventing early lockup of the rear wheels during braking. Thus my other error about mimicking the reaction arm.
Still, using different wheel cylinders appears to be a simpler/cheaper way to solve the problem. It would lead to faster wear on the intermediate brakes and tires. At least ires can be rotated.
Thanks for your help,
JP
>________________________________
> From: Rob Mueller <robmueller@iinet.net.au>
>To: gmclist@temp.gmcnet.org
>Sent: Saturday, June 15, 2013 12:34 AM
>Subject: Re: [GMCnet] Upgrades are paying off
>
>
>Jp,
>
>Here's a link to a cross section of the combination valve which explains how it works. It not a proportioning valve, it does not
>limit pressure to the rear brakes.
>
>http://www.gmcmhphotos.com/photos/member-galleries/p37696-combination-valve-cros.html
>
>Regards,
>Rob M.
>
>
>-----Original Message-----
>From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Jp Benson
>Sent: Friday, June 14, 2013 9:05 AM
>To: gmclist@temp.gmcnet.org
>Subject: Re: [GMCnet] Upgrades are paying off
>
>John, Thanks for the lowdown on non-disc rear brakes. If the proportioning valve limits pressure to the rear brakes then the
>larger intermediate wheel cylinder only redistributes the hydraulic force to the rear brakes. Kind of mimics the reaction arm at
>significantly lower cost.
>
>JP
>
>_______________________________________________
>GMCnet mailing list
>Unsubscribe or Change List Options:
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| Re: [GMCnet] Upgrades are paying off [message #211197 is a reply to message #211195] |
Sat, 15 June 2013 20:52 |
Ronald Pottol
Messages: 505
Registered: September 2012
Location: Redwood City, California
Karma: -2
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Senior Member |
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The problem being is, stock, the ideal distribution of force per axle
varies with how much deceleration is happening. So for max dry braking, you
will lock one axle far sooner than the other in the rain. Reaction arm is
far better than any given fixed choice of slave cylinders.
On Jun 15, 2013 6:44 PM, "Jp Benson" <chocomo99@yahoo.com> wrote:
> Rob,
>
> Your right. It is a combination valve. I read the manual after you
> pointed out my error. I'm surprised that no one has pointed out what
> appears to be my other error.
>
> Using different size wheel cylinders is an attempt to "tune" the braking
> force applied to each wheel to match the friction between the wheel and
> road. So larger intermediate wheel cylinder allocates greate force to the
> intermediate brake shoes. I would expect the forces to be proportional to
> the respective areas of the wheel cylinders.
>
> The reaction arm on the other hand attempts to equalize tire friction by
> balancing the downward forces on all four wheels. So one would want wheel
> cylinders that were all the same.
>
> These are two very different methods for preventing early lockup of the
> rear wheels during braking. Thus my other error about mimicking the
> reaction arm.
>
> Still, using different wheel cylinders appears to be a simpler/cheaper way
> to solve the problem. It would lead to faster wear on the intermediate
> brakes and tires. At least ires can be rotated.
>
>
> Thanks for your help,
> JP
>
>
>
>
> >________________________________
> > From: Rob Mueller <robmueller@iinet.net.au>
> >To: gmclist@temp.gmcnet.org
> >Sent: Saturday, June 15, 2013 12:34 AM
> >Subject: Re: [GMCnet] Upgrades are paying off
> >
> >
> >Jp,
> >
> >Here's a link to a cross section of the combination valve which explains
> how it works. It not a proportioning valve, it does not
> >limit pressure to the rear brakes.
> >
> >
> http://www.gmcmhphotos.com/photos/member-galleries/p37696-combination-valve-cros.html
> >
> >Regards,
> >Rob M.
> >
> >
> >-----Original Message-----
> >From: gmclist-bounces@temp.gmcnet.org [mailto:
> gmclist-bounces@temp.gmcnet.org] On Behalf Of Jp Benson
> >Sent: Friday, June 14, 2013 9:05 AM
> >To: gmclist@temp.gmcnet.org
> >Subject: Re: [GMCnet] Upgrades are paying off
> >
> >John, Thanks for the lowdown on non-disc rear brakes. If the
> proportioning valve limits pressure to the rear brakes then the
> >larger intermediate wheel cylinder only redistributes the hydraulic force
> to the rear brakes. Kind of mimics the reaction arm at
> >significantly lower cost.
> >
> >JP
> >
> >_______________________________________________
> >GMCnet mailing list
> >Unsubscribe or Change List Options:
> >http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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1973 26' GM outfitted
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| Re: [GMCnet] Upgrades are paying off [message #211198 is a reply to message #211197] |
Sat, 15 June 2013 21:06 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
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Senior Member |
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Ron,
It makes sense that the reaction arm reacts in proportion to the rate of deceleration. Good point.
Would be nice to see a curve(s) showing down forces for different speeds and deceleration rates.
I don't quite get the second sentence...
Thanks,
JP
>________________________________
> From: Ronald Pottol <ronaldpottol@gmail.com>
>To: gmclist@temp.gmcnet.org
>Sent: Saturday, June 15, 2013 9:52 PM
>Subject: Re: [GMCnet] Upgrades are paying off
>
>
>The problem being is, stock, the ideal distribution of force per axle
>varies with how much deceleration is happening. So for max dry braking, you
>will lock one axle far sooner than the other in the rain. Reaction arm is
>far better than any given fixed choice of slave cylinders.
>On Jun 15, 2013 6:44 PM, "Jp Benson" <chocomo99@yahoo.com> wrote:
>
>> Rob,
>>
>> Your right. It is a combination valve. I read the manual after you
>> pointed out my error. I'm surprised that no one has pointed out what
>> appears to be my other error.
>>
>> Using different size wheel cylinders is an attempt to "tune" the braking
>> force applied to each wheel to match the friction between the wheel and
>> road. So larger intermediate wheel cylinder allocates greate force to the
>> intermediate brake shoes. I would expect the forces to be proportional to
>> the respective areas of the wheel cylinders.
>>
>> The reaction arm on the other hand attempts to equalize tire friction by
>> balancing the downward forces on all four wheels. So one would want wheel
>> cylinders that were all the same.
>>
>> These are two very different methods for preventing early lockup of the
>> rear wheels during braking. Thus my other error about mimicking the
>> reaction arm.
>>
>> Still, using different wheel cylinders appears to be a simpler/cheaper way
>> to solve the problem. It would lead to faster wear on the intermediate
>> brakes and tires. At least ires can be rotated.
>>
>>
>> Thanks for your help,
>> JP
>>
>>
>>
>>
>> >________________________________
>> > From: Rob Mueller <robmueller@iinet.net.au>
>> >To: gmclist@temp.gmcnet.org
>> >Sent: Saturday, June 15, 2013 12:34 AM
>> >Subject: Re: [GMCnet] Upgrades are paying off
>> >
>> >
>> >Jp,
>> >
>> >Here's a link to a cross section of the combination valve which explains
>> how it works. It not a proportioning valve, it does not
>> >limit pressure to the rear brakes.
>> >
>> >
>> http://www.gmcmhphotos.com/photos/member-galleries/p37696-combination-valve-cros.html
>> >
>> >Regards,
>> >Rob M.
>> >
>> >
>> >-----Original Message-----
>> >From: gmclist-bounces@temp.gmcnet.org [mailto:
>> gmclist-bounces@temp.gmcnet.org] On Behalf Of Jp Benson
>> >Sent: Friday, June 14, 2013 9:05 AM
>> >To: gmclist@temp.gmcnet.org
>> >Subject: Re: [GMCnet] Upgrades are paying off
>> >
>> >John, Thanks for the lowdown on non-disc rear brakes. If the
>> proportioning valve limits pressure to the rear brakes then the
>> >larger intermediate wheel cylinder only redistributes the hydraulic force
>> to the rear brakes. Kind of mimics the reaction arm at
>> >significantly lower cost.
>> >
>> >JP
>> >
>> >_______________________________________________
>> >GMCnet mailing list
>> >Unsubscribe or Change List Options:
>> >http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>> >
>> >
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>_______________________________________________
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| Re: [GMCnet] Upgrades are paying off [message #211202 is a reply to message #211198] |
Sat, 15 June 2013 21:25 |
Ronald Pottol
Messages: 505
Registered: September 2012
Location: Redwood City, California
Karma: -2
|
Senior Member |
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|
My perspective is from years of riding BMW motorcycles with shaft drives
where engine effects are similar to braking effects on a GMC bogie. So when
you apply the brakes, one axle is pushed down by the breaking torque while
the other axle is lifted, as a result, before the brakes are applied, the
weight potential braking force is the same for both axles. As you apply the
brakes, and one axle is pushed up and the other pushed down, the available
braking on each axle changes. So the ideal proportioning of braking force
between the axles depends on the available traction, in the dry, you have a
lot of braking force, and need a fairly large difference, but in the rain,
you want a relatively equal amount of force, so any given fixed ratio (such
as via different sized slave cylinders on each axles) is only idea for one
level of braking, you will lock one axle before the other in any other
circumstances. The reaction arm eliminates brake torque effects, so the
ideal force stays equal no matter what the braking level.
BMW calls this setup paralever, it showed up on the GS models in the mid
1980s.
On Sat, Jun 15, 2013 at 7:06 PM, Jp Benson <chocomo99@yahoo.com> wrote:
> Ron,
>
> It makes sense that the reaction arm reacts in proportion to the rate of
> deceleration. Good point.
> Would be nice to see a curve(s) showing down forces for different speeds
> and deceleration rates.
>
> I don't quite get the second sentence...
>
>
> Thanks,
> JP
>
>
>
>
> >________________________________
> > From: Ronald Pottol <ronaldpottol@gmail.com>
> >To: gmclist@temp.gmcnet.org
> >Sent: Saturday, June 15, 2013 9:52 PM
> >Subject: Re: [GMCnet] Upgrades are paying off
> >
> >
> >The problem being is, stock, the ideal distribution of force per axle
> >varies with how much deceleration is happening. So for max dry braking,
> you
> >will lock one axle far sooner than the other in the rain. Reaction arm is
> >far better than any given fixed choice of slave cylinders.
> >On Jun 15, 2013 6:44 PM, "Jp Benson" <chocomo99@yahoo.com> wrote:
> >
> >> Rob,
> >>
> >> Your right. It is a combination valve. I read the manual after you
> >> pointed out my error. I'm surprised that no one has pointed out what
> >> appears to be my other error.
> >>
> >> Using different size wheel cylinders is an attempt to "tune" the braking
> >> force applied to each wheel to match the friction between the wheel and
> >> road. So larger intermediate wheel cylinder allocates greate force to
> the
> >> intermediate brake shoes. I would expect the forces to be
> proportional to
> >> the respective areas of the wheel cylinders.
> >>
> >> The reaction arm on the other hand attempts to equalize tire friction by
> >> balancing the downward forces on all four wheels. So one would want
> wheel
> >> cylinders that were all the same.
> >>
> >> These are two very different methods for preventing early lockup of the
> >> rear wheels during braking. Thus my other error about mimicking the
> >> reaction arm.
> >>
> >> Still, using different wheel cylinders appears to be a simpler/cheaper
> way
> >> to solve the problem. It would lead to faster wear on the intermediate
> >> brakes and tires. At least ires can be rotated.
> >>
> >>
> >> Thanks for your help,
> >> JP
> >>
> >>
> >>
> >>
> >> >________________________________
> >> > From: Rob Mueller <robmueller@iinet.net.au>
> >> >To: gmclist@temp.gmcnet.org
> >> >Sent: Saturday, June 15, 2013 12:34 AM
> >> >Subject: Re: [GMCnet] Upgrades are paying off
> >> >
> >> >
> >> >Jp,
> >> >
> >> >Here's a link to a cross section of the combination valve which
> explains
> >> how it works. It not a proportioning valve, it does not
> >> >limit pressure to the rear brakes.
> >> >
> >> >
> >>
> http://www.gmcmhphotos.com/photos/member-galleries/p37696-combination-valve-cros.html
> >> >
> >> >Regards,
> >> >Rob M.
> >> >
> >> >
> >> >-----Original Message-----
> >> >From: gmclist-bounces@temp.gmcnet.org [mailto:
> >> gmclist-bounces@temp.gmcnet.org] On Behalf Of Jp Benson
> >> >Sent: Friday, June 14, 2013 9:05 AM
> >> >To: gmclist@temp.gmcnet.org
> >> >Subject: Re: [GMCnet] Upgrades are paying off
> >> >
> >> >John, Thanks for the lowdown on non-disc rear brakes. If the
> >> proportioning valve limits pressure to the rear brakes then the
> >> >larger intermediate wheel cylinder only redistributes the hydraulic
> force
> >> to the rear brakes. Kind of mimics the reaction arm at
> >> >significantly lower cost.
> >> >
> >> >JP
> >> >
> >> >_______________________________________________
> >> >GMCnet mailing list
> >> >Unsubscribe or Change List Options:
> >> >http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >> >
> >> >
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >>
> >_______________________________________________
> >GMCnet mailing list
> >Unsubscribe or Change List Options:
> >http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> >
> >
> _______________________________________________
> GMCnet mailing list
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>
--
Plato seems wrong to me today.
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1973 26' GM outfitted
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| Re: [GMCnet] Upgrades are paying off [message #211236 is a reply to message #211202] |
Sun, 16 June 2013 09:03 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
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Senior Member |
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OK, I get it. Road conditions have an effect as well. One size fits all solutions cannot adapt.
An ideal solution will react to the torque shift in a dynamic manner. Either by mechanical, hydraulic or pneumatic means.
The
reaction arm is a mechanical solution. It's reliable and effective but
adds hardware and weight. Dynamic proportioning of hydraulic pressures
would requires adding components to the hydraulic system. This creates
potential for system failure so reliability is a big issue. It might
be doable pneumatically via dual air bags although there are a lot of
unanswered engineering questions.
Here's an idea for thought.
Attach accelerometers to the end of each bogie arm. Vertical
acceleration will be proportional to the change in
torque. Since angular travel of the bogie arm is limited to reasonably
small angles, only vertical acceleration would need to be measured. At
the very least one could record data for various braking systems and
make comparisons. This data could also be used in a "real-time"
feedback loop to control a hydraulic or pneumatic reaction system.
JP
>________________________________
> From: Ronald Pottol <ronaldpottol@gmail.com>
>To: gmclist@temp.gmcnet.org
>Sent: Saturday, June 15, 2013 10:25 PM
>Subject: Re: [GMCnet] Upgrades are paying off
>
>
>My perspective is from years of riding BMW motorcycles with shaft drives
>where engine effects are similar to braking effects on a GMC bogie. So when
>you apply the brakes, one axle is pushed down by the breaking torque while
>the other axle is lifted, as a result, before the brakes are applied, the
>weight potential braking force is the same for both axles. As you apply the
>brakes, and one axle is pushed up and the other pushed down, the available
>braking on each axle changes. So the ideal proportioning of braking force
>between the axles depends on the available traction, in the dry, you have a
>lot of braking force, and need a fairly large difference, but in the rain,
>you want a relatively equal amount of force, so any given fixed ratio (such
>as via different sized slave cylinders on each axles) is only idea for one
>level of braking, you will lock one axle before the other in any other
>circumstances. The reaction arm eliminates brake torque effects, so the
>ideal force stays equal no matter what the braking level.
>
>BMW calls this setup paralever, it showed up on the GS models in the mid
>1980s.
>
>
>
>
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| Re: [GMCnet] Upgrades are paying off [message #211253 is a reply to message #211236] |
Sun, 16 June 2013 10:27 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Jp Benson wrote on Sun, 16 June 2013 10:03 |
OK, I get it. Road conditions have an effect as well. One size fits all solutions cannot adapt.
|
The floating rear brake (here called reaction arm) has been known solution in motorcycles for a very long time. It is as close as you are going to find to a one fix for everything wrong on the rear brakes.
| Quote: |
An ideal solution will react to the torque shift in a dynamic manner. Either by mechanical, hydraulic or pneumatic means.
|
The nearest you could get by hydraulics would be six wheel anti-lock, and while hardware to do this does exist, the adaptation to our relic vehicles would be a very serious undertaking.
| Quote: |
The reaction arm is a mechanical solution. It's reliable and effective but adds hardware and weight.
|
The added unsprung weight is not high enough to cause any handling issues on roads that one could expect to drive a GMC. The difference it made to braking on my coach is remarkable. My coach brakes are otherwise completely stock. A very stupid Jeep driver has the modification to thank for my not remounting his spare tire in the back seat.
| Quote: |
Dynamic proportioning of hydraulic pressures would requires adding components to the hydraulic system. This creates potential for system failure so reliability is a big issue. It might be doable pneumatically via dual air bags although there are a lot of unanswered engineering questions.
|
My study indicated that moving air for this purpose would require very high pressures and/or high compressor horsepower to be effective with the low pressure air springs that inhabit our suspension.
| Quote: |
Here's an idea for thought. Attach accelerometers to the end of each bogie arm. Vertical acceleration will be proportional to the change in torque. Since angular travel of the bogie arm is limited to reasonably small angles, only vertical acceleration would need to be measured. At the very least one could record data for various braking systems and make comparisons. This data could also be used in a "real-time" feedback loop to control a hydraulic or pneumatic reaction system.
JP
|
That last could be done, but it would require separating the road condition from the retarding activity. I have done this, but the vehicle was code-named "The Spaghetti Monster" by my techs. I didn't keep that job long. I make things go, not stop.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Upgrades are paying off [message #211279 is a reply to message #211253] |
Sun, 16 June 2013 14:39 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
|
Senior Member |
|
|
Matt,
I haven't read all the GMC info on reaction arm systems but have heard a lot of superlatives on performance. However, I do wonder how they compare quanitatively to other systems. I wouldn't be surprised if there were reasonably priced turnkey systems for measuring the accelerations involved. Road effects could be minimized by choosing an appropriate location for test. I like the Spaghetti GMC idea.
Any technique that controls hydraulic pressure (anti-lock or otherwise) will have a similar effect as using different size wheel cylinders. That is (at best) it tunes the brake pressure to match the road friction and forward brakes will wear sooner. I like the wheel cylinder idea because of simplicity. Good bang for the bucks. There are a lot of good reasons not to do anything more sophisticated than that.
A pneumatic solution is attractive in that it mimics the reaction arm effect. That is balances the downward force on the rear wheels. I've done some preliminary calculations but not enough to reach the conclusion that you have.
Well what goes up comes down and everything that goes forward must stop. At least in a gravity environment. Always more fun to be on the go team.
Thanks for your input,
JP
>________________________________
> From: Matt Colie <matt7323tze@gmail.com>
>To: gmclist@temp.gmcnet.org
>Sent: Sunday, June 16, 2013 11:27 AM
>Subject: Re: [GMCnet] Upgrades are paying off
>
>
>
>
>Jp Benson wrote on Sun, 16 June 2013 10:03
>> OK, I get it. Road conditions have an effect as well. One size fits all solutions cannot adapt.
>
>The floating rear brake (here called reaction arm) has been known solution in motorcycles for a very long time. It is as close as you are going to find to a one fix for everything wrong on the rear brakes.
>Quote:
>> An ideal solution will react to the torque shift in a dynamic manner. Either by mechanical, hydraulic or pneumatic means.
>
>The nearest you could get by hydraulics would be six wheel anti-lock, and while hardware to do this does exist, the adaptation to our relic vehicles would be a very serious undertaking.
>Quote:
>> The reaction arm is a mechanical solution. It's reliable and effective but adds hardware and weight.
>
>The added unsprung weight is not high enough to cause any handling issues on roads that one could expect to drive a GMC. The difference it made to braking on my coach is remarkable. My coach brakes are otherwise completely stock. A very stupid Jeep driver has the modification to thank for my not remounting his spare tire in the back seat.
>Quote:
>> Dynamic proportioning of hydraulic pressures would requires adding components to the hydraulic system. This creates potential for system failure so reliability is a big issue. It might be doable pneumatically via dual air bags although there are a lot of unanswered engineering questions.
>
>My study indicated that moving air for this purpose would require very high pressures and/or high compressor horsepower to be effective with the low pressure air springs that inhabit our suspension.
>Quote:
>> Here's an idea for thought. Attach accelerometers to the end of each bogie arm. Vertical acceleration will be proportional to the change in torque. Since angular travel of the bogie arm is limited to reasonably small angles, only vertical acceleration would need to be measured. At the very least one could record data for various braking systems and make comparisons. This data could also be used in a "real-time" feedback loop to control a hydraulic or pneumatic reaction system.
>>
>> JP
>
>That last could be done, but it would require separating the road condition from the retarding activity. I have done this, but the vehicle was code-named "The Spaghetti Monster" by my techs. I didn't keep that job long. I make things go, not stop.
>
>Matt
>
>
>
>--
>Matt & Mary Colie
>'73 Glacier 23 Chaumière (say show-me-air)
>Now with 4 working Rear Brakes
>SE Michigan - Twixt A2 and Detroit
>_______________________________________________
>GMCnet mailing list
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| Re: [GMCnet] Upgrades are paying off [message #211296 is a reply to message #211279] |
Sun, 16 June 2013 18:28 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Well, I got two heavy boxes from someplace in California friday. Bushed bent rods, welded up pieces, and about eight pages of instructions. Now I need a small can of cutting oil and I'm happenin'. Based on iser reports, this is the cost effective way to get the dam' thing to stop a bit quicker without all the histrionics from the tail end of it. I'll report back. I washed the pine tree spooge off it this evening, the old beast doesn't look all that bad cleaned up.
-=-johnny
'76 23' transmode norris
'76 palm beach
From: Jp Benson <chocomo99@yahoo.com>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Sent: Sunday, June 16, 2013 3:39 PM
Subject: Re: [GMCnet] Upgrades are paying off
Matt,
I haven't read all the GMC info on reaction arm systems but have heard a lot of superlatives on performance. However, I do wonder how they compare quanitatively to other systems. I wouldn't be surprised if there were reasonably priced turnkey systems for measuring the accelerations involved. Road effects could be minimized by choosing an appropriate location for test. I like the Spaghetti GMC idea.
Any technique that controls hydraulic pressure (anti-lock or otherwise) will have a similar effect as using different size wheel cylinders. That is (at best) it tunes the brake pressure to match the road friction and forward brakes will wear sooner. I like the wheel cylinder idea because of simplicity. Good bang for the bucks. There are a lot of good reasons not to do anything more sophisticated than that.
A pneumatic solution is attractive in that it mimics the reaction arm effect. That is balances the downward force on the rear wheels. I've done some preliminary calculations but not enough to reach the conclusion that you have.
Well what goes up comes down and everything that goes forward must stop. At least in a gravity environment. Always more fun to be on the go team.
Thanks for your input,
JP
>________________________________
> From: Matt Colie <matt7323tze@gmail.com>
>To: gmclist@temp.gmcnet.org
>Sent: Sunday, June 16, 2013 11:27 AM
>Subject: Re: [GMCnet] Upgrades are paying off
>
>
>
>
>Jp Benson wrote on Sun, 16 June 2013 10:03
>> OK, I get it. Road conditions have an effect as well. One size fits all solutions cannot adapt.
>
>The floating rear brake (here called reaction arm) has been known solution in motorcycles for a very long time. It is as close as you are going to find to a one fix for everything wrong on the rear brakes.
>Quote:
>> An ideal solution will react to the torque shift in a dynamic manner. Either by mechanical, hydraulic or pneumatic means.
>
>The nearest you could get by hydraulics would be six wheel anti-lock, and while hardware to do this does exist, the adaptation to our relic vehicles would be a very serious undertaking.
>Quote:
>> The reaction arm is a mechanical solution. It's reliable and effective but adds hardware and weight.
>
>The added unsprung weight is not high enough to cause any handling issues on roads that one could expect to drive a GMC. The difference it made to braking on my coach is remarkable. My coach brakes are otherwise completely stock. A very stupid Jeep driver has the modification to thank for my not remounting his spare tire in the back seat.
>Quote:
>> Dynamic proportioning of hydraulic pressures would requires adding components to the hydraulic system. This creates potential for system failure so reliability is a big issue. It might be doable pneumatically via dual air bags although there are a lot of unanswered engineering questions.
>
>My study indicated that moving air for this purpose would require very high pressures and/or high compressor horsepower to be effective with the low pressure air springs that inhabit our suspension.
>Quote:
>> Here's an idea for thought. Attach accelerometers to the end of each bogie arm. Vertical acceleration will be proportional to the change in torque. Since angular travel of the bogie arm is limited to reasonably small angles, only vertical acceleration would need to be measured. At the very least one could record data for various braking systems and make comparisons. This data could also be used in a "real-time" feedback loop to control a hydraulic or pneumatic reaction system.
>>
>> JP
>
>That last could be done, but it would require separating the road condition from the retarding activity. I have done this, but the vehicle was code-named "The Spaghetti Monster" by my techs. I didn't keep that job long. I make things go, not stop.
>
>Matt
>
>
>
>--
>Matt & Mary Colie
>'73 Glacier 23 Chaumière (say show-me-air)
>Now with 4 working Rear Brakes
>SE Michigan - Twixt A2 and Detroit
>_______________________________________________
>GMCnet mailing list
>Unsubscribe or Change List Options:
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Upgrades are paying off [message #211298 is a reply to message #211279] |
Sun, 16 June 2013 18:55 |
|
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
| Jp Benson wrote on Sun, 16 June 2013 15:39 |
Matt,
I haven't read all the GMC info on reaction arm systems but have heard a lot of superlatives on performance. However, I do wonder how they compare quantitatively to other systems. I wouldn't be surprised if there were reasonably priced turnkey systems for measuring the accelerations involved. Road effects could be minimized by choosing an appropriate location for test. I like the Spaghetti GMC idea.
Any technique that controls hydraulic pressure (anti-lock or otherwise) will have a similar effect as using different size wheel cylinders. That is (at best) it tunes the brake pressure to match the road friction and forward brakes will wear sooner. I like the wheel cylinder idea because of simplicity. Good bang for the bucks. There are a lot of good reasons not to do anything more sophisticated than that.
A pneumatic solution is attractive in that it mimics the reaction arm effect. That is balances the downward force on the rear wheels. I've done some preliminary calculations but not enough to reach the conclusion that you have.
Well what goes up comes down and everything that goes forward must stop. At least in a gravity environment. Always more fun to be on the go team.
Thanks for your input,
JP
|
JP,
An awful lot of owners have done the pick a cylinder fix and many are happy with it. The downfall is that you still don't get six tires working when you are in a hard-stable retard.
Any of the "Reaction Arm" systems will. You just have to pick the one that best fits your needs, wants and desires. I like have stock disk/drum and real good brakes. I still have a parking brake and I can buy new parts by the GM numbers in the book.
I did try to gather some data with the accelerometers in my smart phone, but there was just too much other QRM to separate and get a set of signals that made clear sense.
If someone else would cover the tab, I'd be glad to instrument a coach as I did a diesel pickup back then. I do believe that the instrument package would be smaller now, but the price is probably not much better than the 33+K$ that I had to work with at the time. That was just the Multichannel DACs, cables, accelerometers, speed pickups, and travel sensors. There were twelve channels of data per wheel and a bunch (about a dozen) more from the chassis.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Upgrades are paying off [message #211368 is a reply to message #211298] |
Mon, 17 June 2013 11:21 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
|
Senior Member |
|
|
Matt,
$33K for that hardware? Obviously you were instrumenting the hell out of the system but it does seem high at today's price points. Given that you were buying the components and assembling the system I suspect it was a few years back. Or perhaps you had to do a custom fit job to get all the various data that you needed.
For rear braking system characterization we only need to measure Z-axis acceleration at two (maybe 4) locations. In a quick search I found a standalone 3-axis accelerometer and data logger (under $200) that looks like it would do the job nicely. On the cheap, one could even do the arms one at a time. I have plenty enough experience to know it's never that simple but it looks doable using current COTS parts.
When my coach is finally running, I will likely do it. Then we can make quantitative comparisons about the various braking systems.
I like that cell phone try. Too bad it didn't produce.
JP
BTW in that other thread, you got me on the "remote operated" valve. That makes it a lot harder.
>________________________________
> From: Matt Colie <matt7323tze@gmail.com>
>To: gmclist@temp.gmcnet.org
>Sent: Sunday, June 16, 2013 7:55 PM
>Subject: Re: [GMCnet] Upgrades are paying off
>
>
>
>
>Jp Benson wrote on Sun, 16 June 2013 15:39
>> Matt,
>>
>> I haven't read all the GMC info on reaction arm systems but have heard a lot of superlatives on performance. However, I do wonder how they compare quantitatively to other systems. I wouldn't be surprised if there were reasonably priced turnkey systems for measuring the accelerations involved. Road effects could be minimized by choosing an appropriate location for test. I like the Spaghetti GMC idea.
>>
>> Any technique that controls hydraulic pressure (anti-lock or otherwise) will have a similar effect as using different size wheel cylinders. That is (at best) it tunes the brake pressure to match the road friction and forward brakes will wear sooner. I like the wheel cylinder idea because of simplicity. Good bang for the bucks. There are a lot of good reasons not to do anything more sophisticated than that.
>>
>> A pneumatic solution is attractive in that it mimics the reaction arm effect. That is balances the downward force on the rear wheels. I've done some preliminary calculations but not enough to reach the conclusion that you have.
>>
>> Well what goes up comes down and everything that goes forward must stop. At least in a gravity environment. Always more fun to be on the go team.
>>
>> Thanks for your input,
>> JP
>
>JP,
>
>An awful lot of owners have done the pick a cylinder fix and many are happy with it. The downfall is that you still don't get six tires working when you are in a hard-stable retard.
>
>Any of the "Reaction Arm" systems will. You just have to pick the one that best fits your needs, wants and desires. I like have stock disk/drum and real good brakes. I still have a parking brake and I can buy new parts by the GM numbers in the book.
>
>I did try to gather some data with the accelerometers in my smart phone, but there was just too much other QRM to separate and get a set of signals that made clear sense.
>
>If someone else would cover the tab, I'd be glad to instrument a coach as I did a diesel pickup back then. I do believe that the instrument package would be smaller now, but the price is probably not much better than the 33+K$ that I had to work with at the time. That was just the Multichannel DACs, cables, accelerometers, speed pickups, and travel sensors. There were twelve channels of data per wheel and a bunch (about a dozen) more from the chassis.
>
>Matt
>--
>Matt & Mary Colie
>'73 Glacier 23 Chaumière (say show-me-air)
>Now with 4 working Rear Brakes
>SE Michigan - Twixt A2 and Detroit
>_______________________________________________
>GMCnet mailing list
>Unsubscribe or Change List Options:
>http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
>
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| Re: [GMCnet] Upgrades are paying off [message #211381 is a reply to message #211195] |
Mon, 17 June 2013 13:20 |
 |
Tangerine
Messages: 192
Registered: February 2004
Location: Livonia, MI
Karma: 0
|
Senior Member |
|
|
On 6/15/2013 9:44 PM, Jp Benson wrote:
> Rob,
>
> Your right. It is a combination valve. I read the manual after you pointed out my error. I'm surprised that no one has pointed out what appears to be my other error.
>
> Using different size wheel cylinders is an attempt to "tune" the braking force applied to each wheel to match the friction between the wheel and road. So larger intermediate wheel cylinder allocates greate force to the intermediate brake shoes. I would expect the forces to be proportional to the respective areas of the wheel cylinders.
>
> The reaction arm on the other hand attempts to equalize tire friction by balancing the downward forces on all four wheels. So one would want wheel cylinders that were all the same.
>
> These are two very different methods for preventing early lockup of the rear wheels during braking. Thus my other error about mimicking the reaction arm.
>
> Still, using different wheel cylinders appears to be a simpler/cheaper way to solve the problem. It would lead to faster wear on the intermediate brakes and tires. At least ires can be rotated.
>
>
> Thanks for your help,
> JP
>
>
>
>
>> ________________________________
>> From: Rob Mueller<robmueller@iinet.net.au>
>> To: gmclist@temp.gmcnet.org
>> Sent: Saturday, June 15, 2013 12:34 AM
>> Subject: Re: [GMCnet] Upgrades are paying off
>>
>>
>> Jp,
>>
>> Here's a link to a cross section of the combination valve which explains how it works. It not a proportioning valve, it does not
>> limit pressure to the rear brakes.
>>
>> http://www.gmcmhphotos.com/photos/member-galleries/p37696-combination-valve-cros.html
>>
>> Regards,
>> Rob M.
>>
>>
>> -----Original Message-----
>> From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Jp Benson
>> Sent: Friday, June 14, 2013 9:05 AM
>> To: gmclist@temp.gmcnet.org
>> Subject: Re: [GMCnet] Upgrades are paying off
>>
>> John, Thanks for the lowdown on non-disc rear brakes. If the proportioning valve limits pressure to the rear brakes then the
>> larger intermediate wheel cylinder only redistributes the hydraulic force to the rear brakes. Kind of mimics the reaction arm at
>> significantly lower cost.
>>
>> JP
Hi Guys
I have all new parts in my brakes. Replaced everything with stainless
steel lines. New rubber hoses and a new combination valve (brass). I
did put in larger wheel cylinders on the middle wheels. Original size
on the rear wheels. All brand new, including the master cylinder. I
have very good brakes compared to before. But I have still locked up
the very rear wheels and slid them for at least 20 feet. Flat spots. I
would want the reaction arms if for not other reason than to save my tires.
Gary W. Mills (Livonia MI)
. ___________
./_][__][] []| 1974 GMC M/H
.*O-------OO-* Painted Desert
"Tangerine Dream" W/New Frame
./___\.
(o\_!_/o) '74 Love Bug
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1974 GMC 260
Tangerine Dream
Livonia Michigan
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| Re: [GMCnet] Upgrades are paying off [message #211412 is a reply to message #211376] |
Mon, 17 June 2013 16:14 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
|
Senior Member |
|
|
A,
I do mean an active pneumatic(applies to air suspension) system. I also stated that any active hydraulic (applies to brake fluid) system would have a similar effect as using different wheel cylinders sizes. As Matt pointed out the ideal hydraulic system is anti-lock brakes which still does not address the problem of force re-distribution while braking.
An inactive pneumatic system to improve braking potential would isolate front and rear air bags and maintain higher pressure in the rear bag. An active pneumatic system would mimic the reaction arms by modulating pressure to the airbags. It may or may not be feasible.
We're in agreement that the reaction arm system maximizes braking potential. It's very reliable, very effective and obvious why lots of people use them. The downsides of reaction arms are increased weight and hardware that is very close to road level. I'm kind of weight conscious so 70 lbs is a lot to me. Having hard metal below frame level increases risk of damage from road debris. So, I'm curious, what is the next best thing and what else can be done?
As long as the rear wheels don't skid you still have six wheel brakes. Doesn't "reducing the probability of skidding the trailing wheel" really mean that the onset of trailing wheel skid is delayed? Thereby maintaining the braking contribution of the trailing wheel during hard braking. Similar to the effect of anti-lock brakes. I agree that the tires are saved but don't understand how braking capacity is sacrificed. I'm a little confused. It seems almost like you're suggesting that there is no value to using different size wheel cylinders other than saving the rear tire. If that's true, then it might make sense to disconnect the rear-most brakes and install heavier duty forward brakes.
Thanks,
JP
>________________________________
> From: A. <markbb1@netzero.com>
>To: gmclist@temp.gmcnet.org
>Sent: Monday, June 17, 2013 1:06 PM
>Subject: Re: [GMCnet] Upgrades are paying off
>
>
>
>
>Jp Benson wrote on Sun, 16 June 2013 14:39
>> ...A pneumatic solution is attractive in that it mimics the reaction arm effect. That is balances the downward force on the rear wheels. ...
>Unless you are talking about an active suspension system, a pneumaitc solution (as applies to brake fluid pressure) will NOT mimic the reaction arm effect.
>
>The reaction arm keeps the front swing arm from trying to rotate down, and the trailing swing arm from trying to rotate up. The result is that the weight of that side is equally distributed on both wheels even when braking. Both wheels on that side will have the same friction with the road, allowing the cylinders in both wheels to be the same size and the shoes in each drum to dissipate the same amount of energy - roughly twice as much braking as either wheel could do alone. If you allow the swing arms to rotate, all you can do is reduce the probability of skidding the trailing wheel, saving the tire, but sacrificing braking capacity.
>
>Fiddling with the wheel cylinder size or pressure on the shoes just moves the system closer to being a six wheel vehicle with four wheel brakes. The harder the stop, the less contribution from the trailing wheel. No way that is going to stop as short as using all six wheels for braking.
>--
>'73 23' Sequoia For Camping
>'73 23' CanyonLands For Sale
>UA (Upper Alabama)
>"Time is money. If you use YOUR time, you get to keep YOUR money."
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| Re: [GMCnet] Upgrades are paying off [message #211433 is a reply to message #211412] |
Mon, 17 June 2013 18:18 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
|
Senior Member |
|
|
| Jp Benson wrote on Mon, 17 June 2013 16:14 |
A,
I do mean an active pneumatic(applies to air suspension) system. I also stated that any active hydraulic (applies to brake fluid) system would have a similar effect as using different wheel cylinders sizes. As Matt pointed out the ideal hydraulic system is anti-lock brakes which still does not address the problem of force re-distribution while braking.
An inactive pneumatic system to improve braking potential would isolate front and rear air bags and maintain higher pressure in the rear bag. An active pneumatic system would mimic the reaction arms by modulating pressure to the airbags. It may or may not be feasible.
|
You would need to pump air in and out of the bags a lot quicker than the OEM system to adjust pressure on the wheels fast enough to "emulate" the reaction arm system. And there would be a weight penalty comparable to the 70 pounds of the reaction arm system.| Quote: |
We're in agreement that the reaction arm system maximizes braking potential. It's very reliable, very effective and obvious why lots of people use them. The downsides of reaction arms are increased weight and hardware that is very close to road level. I'm kind of weight conscious so 70 lbs is a lot to me. Having hard metal below frame level increases risk of damage from road debris. So, I'm curious, what is the next best thing and what else can be done?
|
I never thought about it. That reaction arm hardware will survive a pretty massive hit. You hit something hard enough to damage the reaction arm stuff, and you better be looking at your holding tanks and everything else under there for damage.| Quote: |
As long as the rear wheels don't skid you still have six wheel brakes. Doesn't "reducing the probability of skidding the trailing wheel" really mean that the onset of trailing wheel skid is delayed? Thereby maintaining the braking contribution of the trailing wheel during hard braking. Similar to the effect of anti-lock brakes.
|
No. When the leading wheel starts to rotate down, it takes more and more weight off the trailing wheel. Taken to the limit, the rear wheel will have no pressure against the pavement, and if you have reduced the pressure on the shoes to keep the wheel from skidding, you have reduced the energy dissipation of that brake to zero. The other brake is not only burning up, the wheel is carrying the entire load of that side of the vehicle, overloading the tire and the swing arm.| Quote: |
I agree that the tires are saved but don't understand how braking capacity is sacrificed.
|
Less friction with the road means less friction the shoes can apply to the drum. That friction is how the kinetic energy of the vehicle is dissipated to bring it to a stop.| Quote: |
I'm a little confused. It seems almost like you're suggesting that there is no value to using different size wheel cylinders other than saving the rear tire.
|
It makes a little sense to increase the intermediate wheel cylinder size to help reduce the rear wheel skidding if you don't want to spring for the reaction arm. It is a bandaid and not a real solution. | Quote: |
If that's true, then it might make sense to disconnect the rear-most brakes and install heavier duty forward brakes.
|
Disabling the rear wheel brake is the direction you are headed when you choose to reduce the pressure on the rear wheel cylinder. To me it makes sense to spread the braking requirement over all the wheels instead of trying to get twice as much braking out of half the wheels.
Keeping the weight the same on both leading and trailing wheels is the ONLY way you are going to get full braking contribution from all four wheels. The reaction arm is a couple orders of magnitude easier to implement than active suspension, and will be less trouble prone in the long run.
|
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| Re: [GMCnet] Upgrades are paying off [message #211454 is a reply to message #211433] |
Mon, 17 June 2013 23:29 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
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Mark,
I can see that you understand the reaction arm system on
our coach.
Chuck Aulgar, the founder of our system got angry at one of our people on
the net as he thought he understood how the system worked.
I just found out why the drum /drum rear reaction arm was giving me fits
during the tests by skidding different wheels.
All this will be discussed at the International convention.
We tried one test by inflating the rear bags at 135psi and the front at
60psi.
Result was that the rear tires skidded.
Amazing how much power is being controlled during stopping.
On Mon, Jun 17, 2013 at 4:18 PM, A. <markbb1@netzero.com> wrote:
>
>
> Jp Benson wrote on Mon, 17 June 2013 16:14
> > A,
> >
> > I do mean an active pneumatic(applies to air suspension) system. I also
> stated that any active hydraulic (applies to brake fluid) system would
> have a similar effect as using different wheel cylinders sizes. As Matt
> pointed out the ideal hydraulic system is anti-lock brakes which still
> does not address the problem of force re-distribution while braking.
> >
> >
> > An inactive pneumatic system to improve braking potential would isolate
> front and rear air bags and maintain higher pressure in the rear bag. An
> active pneumatic system would mimic the reaction arms by modulating
> pressure to the airbags. It may or may not be feasible.
> You would need to pump air in and out of the bags a lot quicker than the
> OEM system to adjust pressure on the wheels fast enough to "emulate" the
> reaction arm system. And there would be a weight penalty comparable to the
> 70 pounds of the reaction arm system.Quote:
> > We're in agreement that the reaction arm system maximizes braking
> potential. It's very reliable, very effective and obvious why lots of
> people use them. The downsides of reaction arms are increased weight and
> hardware that is very close to road level. I'm kind of weight conscious
> so 70 lbs is a lot to me. Having hard metal below frame level increases
> risk of damage from road debris. So, I'm curious, what is the next best
> thing and what else can be done?
> I never thought about it. That reaction arm hardware will survive a
> pretty massive hit. You hit something hard enough to damage the reaction
> arm stuff, and you better be looking at your holding tanks and everything
> else under there for damage.Quote:
> > As long as the rear wheels don't skid you still have six wheel brakes.
> Doesn't "reducing the probability of skidding the trailing wheel" really
> mean that the onset of trailing wheel skid is delayed? Thereby maintaining
> the braking contribution of the trailing wheel during hard braking.
> Similar to the effect of anti-lock brakes.
> No. When the leading wheel starts to rotate down, it takes more and more
> weight off the trailing wheel. Taken to the limit, the rear wheel will
> have no pressure against the pavement, and if you have reduced the pressure
> on the shoes to keep the wheel from skidding, you have reduced the energy
> dissipation of that brake to zero. The other brake is not only burning up,
> the wheel is carrying the entire load of that side of the vehicle,
> overloading the tire and the swing arm.Quote:
> > I agree that the tires are saved but don't understand how braking
> capacity is sacrificed.
> Less friction with the road means less friction the shoes can apply to the
> drum. That friction is how the kinetic energy of the vehicle is dissipated
> to bring it to a stop.Quote:
> > I'm a little confused. It seems almost like you're suggesting that
> there is no value to using different size wheel cylinders other than saving
> the rear tire.
> It makes a little sense to increase the intermediate wheel cylinder size
> to help reduce the rear wheel skidding if you don't want to spring for the
> reaction arm. It is a bandaid and not a real solution. Quote:
> > If that's true, then it might make sense to disconnect the rear-most
> brakes and install heavier duty forward brakes.
> Disabling the rear wheel brake is the direction you are headed when you
> choose to reduce the pressure on the rear wheel cylinder. To me it makes
> sense to spread the braking requirement over all the wheels instead of
> trying to get twice as much braking out of half the wheels.
>
> Keeping the weight the same on both leading and trailing wheels is the
> ONLY way you are going to get full braking contribution from all four
> wheels. The reaction arm is a couple orders of magnitude easier to
> implement than active suspension, and will be less trouble prone in the
> long run.
> --
> '73 23' Sequoia For Camping
> '73 23' CanyonLands For Sale
> UA (Upper Alabama)
> "Time is money. If you use YOUR time, you get to keep YOUR money."
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Upgrades are paying off [message #211456 is a reply to message #211454] |
Mon, 17 June 2013 23:54 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
|
The late Ken Rose that sold us the Q Bag basic design was playing with
controlling the bag pressures. It worked to a certain extent, but we
decided after few tests that we would leave it off our unit.
When Chuck A,sent me the prilimanary design on the reaction arm, I
immidiatly knew it was going to work well.
I immidiatly got Rick Fanagan to assist Chuck in developing the unit.
Tom Prior asked me why we did not do the Drum/Drum Reaction system. I
laughed at him and told him it would be too much work to do and if done, it
would be lot o work to make ti happen.
I sent him several parts for him to mock up a unit, then he pulled it off
after few articals failed after our tests.
Now it is working very well and now selling several units.
We will be having a Disc/drum system for the HARRISON System and for others.
On Mon, Jun 17, 2013 at 9:29 PM, Jim Kanomata <jimkanomata@gmail.com> wrote:
> Mark,
> I can see that you understand the reaction arm system on
> our coach.
> Chuck Aulgar, the founder of our system got angry at one of our people on
> the net as he thought he understood how the system worked.
> I just found out why the drum /drum rear reaction arm was giving me fits
> during the tests by skidding different wheels.
> All this will be discussed at the International convention.
> We tried one test by inflating the rear bags at 135psi and the front at
> 60psi.
> Result was that the rear tires skidded.
> Amazing how much power is being controlled during stopping.
>
>
>
> On Mon, Jun 17, 2013 at 4:18 PM, A. <markbb1@netzero.com> wrote:
>
>>
>>
>> Jp Benson wrote on Mon, 17 June 2013 16:14
>> > A,
>> >
>> > I do mean an active pneumatic(applies to air suspension) system. I
>> also stated that any active hydraulic (applies to brake fluid) system
>> would have a similar effect as using different wheel cylinders sizes. As
>> Matt pointed out the ideal hydraulic system is anti-lock brakes which
>> still does not address the problem of force re-distribution while braking.
>> >
>> >
>> > An inactive pneumatic system to improve braking potential would isolate
>> front and rear air bags and maintain higher pressure in the rear bag. An
>> active pneumatic system would mimic the reaction arms by modulating
>> pressure to the airbags. It may or may not be feasible.
>> You would need to pump air in and out of the bags a lot quicker than the
>> OEM system to adjust pressure on the wheels fast enough to "emulate" the
>> reaction arm system. And there would be a weight penalty comparable to the
>> 70 pounds of the reaction arm system.Quote:
>> > We're in agreement that the reaction arm system maximizes braking
>> potential. It's very reliable, very effective and obvious why lots of
>> people use them. The downsides of reaction arms are increased weight and
>> hardware that is very close to road level. I'm kind of weight conscious
>> so 70 lbs is a lot to me. Having hard metal below frame level increases
>> risk of damage from road debris. So, I'm curious, what is the next best
>> thing and what else can be done?
>> I never thought about it. That reaction arm hardware will survive a
>> pretty massive hit. You hit something hard enough to damage the reaction
>> arm stuff, and you better be looking at your holding tanks and everything
>> else under there for damage.Quote:
>> > As long as the rear wheels don't skid you still have six wheel brakes.
>> Doesn't "reducing the probability of skidding the trailing wheel" really
>> mean that the onset of trailing wheel skid is delayed? Thereby maintaining
>> the braking contribution of the trailing wheel during hard braking.
>> Similar to the effect of anti-lock brakes.
>> No. When the leading wheel starts to rotate down, it takes more and more
>> weight off the trailing wheel. Taken to the limit, the rear wheel will
>> have no pressure against the pavement, and if you have reduced the pressure
>> on the shoes to keep the wheel from skidding, you have reduced the energy
>> dissipation of that brake to zero. The other brake is not only burning up,
>> the wheel is carrying the entire load of that side of the vehicle,
>> overloading the tire and the swing arm.Quote:
>> > I agree that the tires are saved but don't understand how braking
>> capacity is sacrificed.
>> Less friction with the road means less friction the shoes can apply to
>> the drum. That friction is how the kinetic energy of the vehicle is
>> dissipated to bring it to a stop.Quote:
>> > I'm a little confused. It seems almost like you're suggesting that
>> there is no value to using different size wheel cylinders other than saving
>> the rear tire.
>> It makes a little sense to increase the intermediate wheel cylinder size
>> to help reduce the rear wheel skidding if you don't want to spring for the
>> reaction arm. It is a bandaid and not a real solution. Quote:
>> > If that's true, then it might make sense to disconnect the rear-most
>> brakes and install heavier duty forward brakes.
>> Disabling the rear wheel brake is the direction you are headed when you
>> choose to reduce the pressure on the rear wheel cylinder. To me it makes
>> sense to spread the braking requirement over all the wheels instead of
>> trying to get twice as much braking out of half the wheels.
>>
>> Keeping the weight the same on both leading and trailing wheels is the
>> ONLY way you are going to get full braking contribution from all four
>> wheels. The reaction arm is a couple orders of magnitude easier to
>> implement than active suspension, and will be less trouble prone in the
>> long run.
>> --
>> '73 23' Sequoia For Camping
>> '73 23' CanyonLands For Sale
>> UA (Upper Alabama)
>> "Time is money. If you use YOUR time, you get to keep YOUR money."
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Fremont,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
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Unsubscribe or Change List Options:
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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|
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| Re: [GMCnet] Upgrades are paying off [message #211488 is a reply to message #211433] |
Tue, 18 June 2013 09:54 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
|
Senior Member |
|
|
A,
It's
funny, this whole thread was started by a guy who went to JimK's, paid
for a drum brake refresh, got larger wheel cylinders on the intermediate
wheels and gave a glowing testimonial about improved braking. Nobody
responded for two days but it got me to thinking...
Your painting
me into a corner by suggesting that I would attempt to reduce pressure
to the rear wheel cylinders. I read through all my previous posts and
couldn't find where I ever advocated that. I definitely wouldn't
choose to reduce pressure on the rear wheel cylinder as you suggest. If
a larger mid-wheel cylinder is used then it is imperative to insure
that the master cylinder is still capable of maintaining the same
pressures as before. Thus total braking force is increased. At least at
the wheel cylinders and hopefully to the drums as well. (Otherwise
larger forward shoes would be needed.) The objective is to allow the
forward wheels to do more work (since they have increased road friction)
not to reduce the work load on the rear wheels.
I don't think
the weight penalty of an air suspension reaction system would be
anywhere near 70 lbs. But then I don't have a system to weigh so it's
fair to debate. It's just a thought experiment right now and your
analysis is appreciated. As opposed to pumping air into the rear bag
one could also release air from the forward bag. As you suggest,
latency due to air flow rate is a question mark. It does take several
seconds for the OEM system just to raise/lower the coach. Seems like
that's in the ballpark compared to braking intervals. More importantly
though what pressure differential is needed between the two bags to
balance the down force on the wheels? Or, equivalently, what are the
down forces on the wheels during hard braking. Even when a tire skids
there is still significant down force on the wheel. Otherwise no flat
spot. How much angular
travel is there in the swing arm when the brakes are applied on an OEM
system? etc, etc
JimK has shared some of his insight. It's not
surprising at all that others have looked at this idea before and found
some merit. Also interesting that JimK was amused by the idea of a
drum-drum reaction arm until someone made it work. Now he makes money
from it. That's a smart businessman. I like his experimental nature in
using different pressures in the air bags in conjunction with a
reaction arm. On the surface it doesn't make sense but I think that's
what he was saying. An interesting experiment to try just to see what
happens.
I wouldn't be so worried about road debris damaging the
reaction arms as I would worry about damage to plastic body parts
and/or air bags from debris that could be thrown upward after tangling
with the reaction arm. Not a common occurrence but a definite
possibility of real
damage.
The swing arm rotates freely so force on the arm is
transmitted through the bag to the mount. Unless the air bag flattens
the swing arm shouldn't be overloaded. I have seen pictures of some of
the early Harrison air bag systems where the mount was visibly
deformed. There was no mention of swing arm damage. Later dual bag
systems have heavier duty mounts which in theory could overload the
swing arms.
As long as the rear wheel has traction it carries
part of the braking load. When the rear wheel skids the forward wheel
carries all the load. (Except for the friction that causes flat
spots.) So the real question is what happens during the interval
between applying the brakes and when traction is lost. How do the
various systems compare in this respect? It's nice to hear things like
30% shorter stopping distance. It's a great marketing tool but a top
down view
doesn't tell the whole story. I've suggested one cost effective way to
get hard data on this and will probably do so unless some else does so
first and publishes results. Any myths can then be busted.
We do agree that designing and implementing an active air suspension/reaction system is a non-trivial exercise.
I have some questions about the reaction arm that you may be able to answer:
1.
Do the reaction arms attempt to balance the downward forces on the
tires? Or does they just resist
rotation of the swing arm when the brakes are engaged? If the former is
the case then wouldn't they just maintain whatever state of
balance/imbalance already exists? The answer to this question gives
insight as to what would happen when reaction arms are used with
unbalanced air bags. Also what would happen with different diameter wheel cylinders.
2. What kind of latency is there in the reaction arm? That is how long does it take to react when the brakes are applied?
3.
How much braking force is required to trigger a reaction? If the
brakes were applied softly would the reaction arm do anything?
All of these questions could be addressed with some instrumentation and data collection.
Thanks,
JP
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