Home » Public Forums » GMCnet » Rear control arm material
| Rear control arm material [message #353597] |
Wed, 08 April 2020 14:56  |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
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Does anyone know what our rear control arms are made of? Cast steel? Nodular Iron?
Thanks, Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Rear control arm material [message #353598 is a reply to message #353597] |
Wed, 08 April 2020 16:00  |
James Hupy
Messages: 6806
Registered: May 2010
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Hal, I believe that they are a forging or "impact extrusion". The material
I believe is high tensile steel. Not a casting. The material is elastic by
nature, and requires an enormous amount of hydraulic pressure to effect any
bending. Good stuff at any rate.
Jim Hupy
Salem, Oregon
On Wed, Apr 8, 2020, 12:57 PM Hal StClair via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Does anyone know what our rear control arms are made of? Cast steel?
> Nodular Iron?
> Thanks, Hal
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: Rear control arm material [message #353602 is a reply to message #353597] |
Wed, 08 April 2020 17:17 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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Built by GM Central Forging, so guessing forged. There was a magazine add for Central Forging and used a pic of GMC rear suspension.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Rear control arm material [message #353603 is a reply to message #353598] |
Wed, 08 April 2020 17:10 |
sgltrac
Messages: 2797
Registered: April 2011
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It is cast steel
Sully
Bellevue wa
On Wed, Apr 8, 2020 at 1:56 PM James Hupy via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Hal, I believe that they are a forging or "impact extrusion". The material
> I believe is high tensile steel. Not a casting. The material is elastic by
> nature, and requires an enormous amount of hydraulic pressure to effect any
> bending. Good stuff at any rate.
> Jim Hupy
> Salem, Oregon
>
> On Wed, Apr 8, 2020, 12:57 PM Hal StClair via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Does anyone know what our rear control arms are made of? Cast steel?
>> Nodular Iron?
>> Thanks, Hal
>> --
>> 1977 Royale 101348,
>>
>> 1977 Royale 101586, Diesel powered,
>>
>> 1975 Eleganza II, 101230,
>>
>> 1974 Eagle Bus 45',w/slideout,
>>
>> Rio Rancho, NM
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: Rear control arm material [message #353656 is a reply to message #353605] |
Thu, 09 April 2020 23:21 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
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Thank you, that's what I needed but didn't really want to hear.
Hal
Richard RV wrote on Wed, 08 April 2020 17:18Hal,
They're nodular iron aka ductile cast iron.
https://www.sciencedirect.com/topics/engineering/nodular-iron
From Bill Bryant's article
http://www.bdub.net/publications/GMC_Motorhome_-_The_Story_of_a_Classic.pdf
Second page, first column, halfway down:
"The first chassis built to demonstrate the unique vehicle design was assembled with the now familiar tandem-rear wheel assembly incorporating leading-trailing cast nodular iron arms at the rear, supported with a hydro-air spring from the Saginaw Division of GM."
Richard
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: Rear control arm material [message #353657 is a reply to message #353656] |
Fri, 10 April 2020 00:03 |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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Hal StClair wrote on Thu, 09 April 2020 21:21Thank you, that's what I needed but didn't really want to hear.
Hal
Richard RV wrote on Wed, 08 April 2020 17:18Hal,
They're nodular iron aka ductile cast iron.
https://www.sciencedirect.com/topics/engineering/nodular-iron
What were you planning - modifying the bogey control arms...? Don't leave us hanging - spill!
Richard
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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| Re: Rear control arm material [message #353661 is a reply to message #353597] |
Fri, 10 April 2020 07:42 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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Bill's article mentioning "cast nodular iron" and Saginaw hydro-pneumatic spring is in reference to to first prototype coach. As we know that spring type was abandoned for Firestone equipment isolators (air springs). So perhaps that was not the final version of the production arms??!
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Rear control arm material [message #353664 is a reply to message #353597] |
Fri, 10 April 2020 08:01 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Hal, are you going to modify the rear suspension to hold up a rear engine?
--johnny
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: Rear control arm material [message #353667 is a reply to message #353661] |
Fri, 10 April 2020 10:19 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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I noted that it mentioned being on the prototype and wondered the same thing (hoped it was different) and I've contacted Wes Caughlin thinking he would know. He thought it was a forging but wasn't sure and replied he'd have to contact his supplier or find the stock drawings. I'm still waiting.
And yes Johnny the rear seems to be a better way to drive the coach than the front and all the drawbacks involved. Modding the arm would have been the simple way to accommodate the changes but it seems that probably won't be in the cards.
And Richard, I hate to talk about the project until I get a little further along. Lots and lots of interesting challenges involved.
Hal
JohnL455 wrote on Fri, 10 April 2020 06:42Bill's article mentioning "cast nodular iron" and Saginaw hydro-pneumatic spring is in reference to to first prototype coach. As we know that spring type was abandoned for Firestone equipment isolators (air springs). So perhaps that was not the final version of the production arms??!
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Rear control arm material [message #353668 is a reply to message #353667] |
Fri, 10 April 2020 10:55 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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When I was learning about suspensions, strengths of various materials,
castings vs forgings, etc. At GM training service schools in the late 70's
and early 80's, GM had already had a fair number of lawsuits centered
around suspension system material failures.
Long story, but results from those lawsuits altered GM's thinking
about testing strengths of materials used, etc. Even after researching
metallurgy and construction methods, they embarked on a stepped up program
of actual vehicle crash testing and evaluation. They changed spindles, etc.
from castings to forgings, and impact extruding control arms instead of
just fabricating them from standard steel shapes.
Those steel stamped control arms on our GMCs are crude looking, but
they are very strong, without breaking the bank in production costs.
It costs a whole bunch to forge those bogie arms. But they are
several times stronger than anything else. They are strong for a very long
time, and do not embrittle and stress crack like castings are prone to do.
But, you cannot re-heat them for straightening them.
GM says, if they are bent from collision or other damage, they need to
be replaced, not repaired. (Corporate butt covering, 101)
Just telling you what GM taught me.
I will tell you this. It takes all the grunt my 10 ton porta-power has
to bend one cold. And precision application of a 5# machinist hammer helps
a good deal.
But, I would never, never subject those bogies to welding heat.
Jim Hupy
Salem, Oregon
On Fri, Apr 10, 2020, 8:20 AM Hal StClair via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I noted that it mentioned being on the prototype and wondered the same
> thing (hoped it was different) and I've contacted Wes Caughlin thinking he
> would know. He thought it was a forging but wasn't sure and replied he'd
> have to contact his supplier or find the stock drawings. I'm still waiting.
> And yes Johnny the rear seems to be a better way to drive the coach than
> the front and all the drawbacks involved. Modding the arm would have been
> the
> simple way to accommodate the changes but it seems that probably won't be
> in the cards.
> And Richard, I hate to talk about the project until I get a little further
> along. Lots and lots of interesting challenges involved.
> Hal
>
> JohnL455 wrote on Fri, 10 April 2020 06:42
>> Bill's article mentioning "cast nodular iron" and Saginaw
> hydro-pneumatic spring is in reference to to first prototype coach. As we
> know that
>> spring type was abandoned for Firestone equipment isolators (air
> springs). So perhaps that was not the final version of the production
> arms??!
>
>
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Rear control arm material [message #353676 is a reply to message #353673] |
Fri, 10 April 2020 16:15 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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Richard RV wrote on Fri, 10 April 2020 14:44Hal,
You're killing me buddy! I wonder if your hating to talk about your upcoming project is greater than my hating not knowing! 
I just reviewed Bill Bryant's GMC Historical photos from his DVDs and spoke with him about the bogey arms. The photos of the hydro-pneumatic prototype suspension on the "pie wagon" test vehicle show a much different rear suspension configuration. The leading control arm looks to be steel plates in a wishbone configuration.
Bill said the production bogey control arms are all cast nodular iron with the only differences being the increased spindle diameter and bushings that came about due to an early recall.
Richard
Thank you Richard, that makes sense.
I was hoping to maintain as much of the rear suspension configuration as possible but the original spindle boss is too small for the new proposed design. I'd have liked to modify the arm but your information puts a pin in that idea. Back to the drawing board I guess.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: Rear control arm material [message #353677 is a reply to message #353675] |
Fri, 10 April 2020 16:28 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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Johnny Bridges wrote on Fri, 10 April 2020 15:04Hal, I think 'interesting challenges' is the understatement of the week.
I look forward to how this might be done. Looks like some of the floor in back would be raised for the new motor, which should give room for a drive axle to the rear wheels. Maybe set it up like the old 'torque tube' designs where the whole power train tilts a bit on the front mount and the transmission-driveshaft-differential are rigid and supported by the axle. Anyway, pictures when you have a design and a start?
--johnny
Johnny, how about a 9.75" Ford IRS pumpkin flipped, coupled with a short drive shaft. The bed would be raised slightly but should be fine.
FWD was seriously considered but the 15' drive shaft along with tankage and weight considerations with 800 lb ft motor, rear drive seems to offer the best compromise. Still in the very early stages here-may never come to completion. If people thought me nuts before, here's a little more ammunition.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: Rear control arm material [message #353679 is a reply to message #353597] |
Fri, 10 April 2020 16:36 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Fab a replacement?
--johnny
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: Rear control arm material [message #353681 is a reply to message #353679] |
Fri, 10 April 2020 16:48 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Johnny Bridges wrote on Fri, 10 April 2020 15:36Fab a replacement?
--johnny
Yea. 2 1/2" x .50 wall D.O.M. tube for the spindle end of the arm should be the start. Not sure on the rest of the arm, round or square tube I'd guess. We'll see.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
[Updated on: Fri, 10 April 2020 16:51] Report message to a moderator |
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| Re: [GMCnet] Rear control arm material [message #353737 is a reply to message #353681] |
Sun, 12 April 2020 14:22 |
GMC.LES
Messages: 505
Registered: April 2014
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Hal,
I’ve been thinking hard for some time about how to make a rear drive TZE. The rear suspension arms appear to be the biggest obstacle.
Rear diffs are an easier obstacle to overcome. Have you seen the 9” pass-thru Diffs produced by Differential Engineering? They make an IRS version that might be interesting for driving all 4 rear wheels.
https://images.app.goo.gl/aL6osQQHZeQDwB829
https://images.app.goo.gl/jjitTwd82T1BawQs5
www.differentialengineering.com
Les Burt
Montreal
'75 Eleganza 26'
> On Apr 10, 2020, at 5:48 PM, Hal StClair via Gmclist wrote:
>
> Johnny Bridges wrote on Fri, 10 April 2020 15:36
>> Fab a replacement?
>>
>> --johnny
>
> Yea. 2 1/2" x .50 D.O.M. tube for the spindle should be the start.
> Hal
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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