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Onan heat shield prototype [message #262180]

Wed, 17 September 2014 20:44

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

The whole impetus behind the heat shield has been Ken Burton's conversation with me back in Branson last fall. After sending him an email with some photos of prototype #1, he sent me the following.

Ken Burton

The primary goal is to reflect back the radiant heat off of the cabinet. Look up above your Onan at the cabinet and you will see the primary heat damaged area we are trying to prevent. It is not that large.

Some of the heat is also absorbed by the aluminum itself and the aluminum conducts it away. Also the rest of reflected heat has to go somewhere and that is why I wanted to keep as much airflow as possible under and over the heat shield.

So this is prototype #2. The manifold is completely covered but there is max air flow to reduce heat build up under the shield. What are your thoughts on this version Ken? A production version probably would not have the swoopy curves but would still have the same basic design.

http://www.gmcmhphotos.com/photos/onan-heat-shield/p55950-prototype-heat-shield.html

http://www.gmcmhphotos.com/photos/data/6679/IMG_20140917_170051_679.jpg

http://www.gmcmhphotos.com/photos/onan-heat-shield/p55951-prototype-heat-shield-for-possible-production.html

http://www.gmcmhphotos.com/photos/data/6679/IMG_20140917_170057_788.jpg

I was going to completely open up the forward side except for the mounting area but after looking at the manifold, it is RIGHT BEHIND the aluminum. I could easily remove it if yall don't think it is necessary.

http://www.gmcmhphotos.com/photos/onan-heat-shield/p55952-prototype-heat-shield-for-possible-production.html

http://www.gmcmhphotos.com/photos/data/6679/IMG_20140917_170113_740.jpg

Thoughts? It would probably be about $25. Because of the flanges it would have to go in a larger box so shipping would not be as cheap as the KISS shelves.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: [GMCnet] Onan heat shield prototype [message #262189 is a reply to message #262180]

Wed, 17 September 2014 23:29

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

Kerry,

At Chippewa Falls we'll get your Onan running and we can see how it works. I think I have a digital multi-meter that has a
thermocouple function. We can attach the thermocouple to the inside top of the Onan cabinet and do a test with the heat shield
installed and removed.

Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428

-----Original Message-----
From: Kerry Pinkerton

The whole impetus behind the heat shield has been Ken Burton's conversation with me back in Branson last fall. After sending him an
email with some photos of prototype #1, he sent me the following.

So this is prototype #2. The manifold is completely covered but there is max air flow to reduce heat build up under the shield.
What are your thoughts on this version Ken? A production version probably would not have the swoopy curves but would still have the
same basic design.

http://www.gmcmhphotos.com/photos/onan-heat-shield/p55950-prototype-heat-shield.html

http://www.gmcmhphotos.com/photos/onan-heat-shield/p55951-prototype-heat-shield-for-possible-production.html

I was going to completely open up the forward side except for the mounting area but after looking at the manifold, it is RIGHT
BEHIND the aluminum. I could easily remove it if yall don't think it is necessary.

http://www.gmcmhphotos.com/photos/onan-heat-shield/p55952-prototype-heat-shield-for-possible-production.html

Thoughts? It would probably be about $25. Because of the flanges it would have to go in a larger box so shipping would not be as
cheap as the KISS shelves.
--
Kerry

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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: Onan heat shield prototype [message #262194 is a reply to message #262180]

Thu, 18 September 2014 02:21

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Well, it is not what I envisioned when we started but it ought to do the job.

It is only attached at two points. I'm suggesting that we attach it at three to keep the possible vibration down. How about on the left front have it fold down over the front cover an inch or two. Then drill one hole into the folded part where we can insert a sheet metal screw through it to the front Onan cover. It does not need to be folded absolutely tight against the front cover. It could be out 1/4 inch or so and we would draw it up tight against the front Onan cover with the sheet metal screw.

If shipping box size is an issue how about making it two piece with the leg going down to the head on the left side being a second piece that bolts on to the top with sheet metal screws.

I just brought my coach home tonight and ran the Onan during the 1/2 hour trip. When I got here it was blowing oil all over the place. I did not look to see why it is leaking, but I'm imagining a leaking crank shaft seal. That thing has never leaked before so I'm hoping it is something like a leaking oil pressure sending unit or oil filter. I ran the Onan about 3 weeks ago and parked it inside. There was no oil on the hangar floor from that trip so what ever happened, did it in a big way on my way home tonight.

My point is we do not, at this time, have my coach available to test it on.

How is the access to the choke with the cover installed? Do we need to worry about that? Probably not.

What are the two pop rivets on the left vertical piece? Is that a doubler of some kind?

I like it!

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: Onan heat shield prototype [message #262197 is a reply to message #262194]

Thu, 18 September 2014 06:04

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

Ken Burton wrote on Thu, 18 September 2014 02:21

...It is only attached at two points. I'm suggesting that we attach it at three to keep the possible vibration down. ...

How is the access to the choke with the cover installed? Do we need to worry about that? Probably not.

What are the two pop rivets on the left vertical piece? Is that a doubler of some kind?

I agree with the three point mounting. The little extra metal on the left front as your standing in front of the Onan, is supposed to fold down and be attached by a screw.

Choke access? I did not think about that other than be sure none of the linkage is hindered. I can easily have an access plate over the choke

Pop rivets. Huh, I'd have thought a sharp guy like you would recognize an aluminum stretcher.... Laughing

Laughing

Laughing

Laughing

Laughing

Seriously, that was the only piece of aluminum that was close to the right size on hand when I made it. The weld on the front right was because it broke when I cut out the swoops. This particular piece of aluminum is 5052 and 5052 does not like being bent, straightened, and re-bent.

Since this seems to address the main points, I'll make a cleaner version and we can test it at the rally. Between Robs thermocouple and my IR heat thermometer, we should be able to determine if what impact it has on heat both inside the cabinet AND under the heat shield itself.

Btw Ken, the insulation on my coach is not heat damaged. The hour meter shows some 700 hours so it's been run a bit. Mine is a 77. Was the cabinet and insulation the same for all years?

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: Onan heat shield prototype [message #262208 is a reply to message #262197]

Thu, 18 September 2014 08:19

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

The heat damage was first shown to me by Larry Dilk at the work rally we had at Blaine Merrell's a few year ago. We checked 3 other coaches and they all had some signs of it.

I do not know what is OEM as far a insulation goes in that cabinet because it seems everyone has reworked theirs in some fashion. Mine is some kind of foam that all melted away in the center. One guy had some Reflectix. That bothered me because that stuff will burn quickly if it ever gets started.

I just asked about choke. It is not a big deal. If they want to work on the choke, they can always remove the 3 screws and the whole cover in less than 1 minute.

Aluminum stretcher Huh? Sounds something like the cable stretchers we had in the electrical business.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: Onan heat shield prototype [message #262215 is a reply to message #262208]

Thu, 18 September 2014 08:57

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Hey, look at this. It looks like Wally already built his own heat shield.

http://www.gmcmhphotos.com/photos/onan-with-variable-reluctor-spark-timing/p46834-sensor-in-place.html

Are we reinventing the wheel here?

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Updated on: Thu, 18 September 2014 08:58]

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Re: [GMCnet] Onan heat shield prototype [message #262223 is a reply to message #262215]

Thu, 18 September 2014 10:34

sgltrac

Messages: 2797
Registered: April 2011

Karma: 1

Senior Member

Fwiw the Onan and opposite storage boxes in The Pig were plywood boxes lined with tin.

Todd Sullivan

Sully
77 royale
Seattle

> On Sep 18, 2014, at 6:57 AM, Ken Burton wrote:
>
> Hey, look at this. It looks like Wally already built his own heat shield.
>
> http://www.gmcmhphotos.com/photos/onan-with-variable-reluctor-spark-timing/p46834-sensor-in-place.html
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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Re: Onan heat shield prototype [message #262225 is a reply to message #262180]

Thu, 18 September 2014 10:41

midlf

Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)

Karma: 1

Senior Member

Yours and Wally's both look good. I did mine a bit different using a 12"x24" piece of polished SS mounted to the coach and not the genny. Yours is more cost effective as my metal was $36. However it required no metal cutting and no fab skills but was a PITA to get mounted.

Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

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Re: Onan heat shield prototype [message #262235 is a reply to message #262180]

Thu, 18 September 2014 12:49

djeffers

Messages: 219
Registered: June 2004

Karma: 2

Senior Member

The point on the Onan EXHAUST MANIFOLD WHERE THE TWO CYLINDER RUNNERS JOIN is the DANGEROUSLY HOT SPOT on our '78 Eleganza II, when running under heavy load.

We had the Onan running in the box, supporting both air conditioners on high while parked under the trees on a hot Florida night.

We detected the smell of burning wood; checked the Onan and the exhaust manifold juncture of the two cylinders had become very hot and scorched the factory insulation above and the wood above that. Our Onan has 225 hours on it. We never ran the Onan in the box after that.

We've been wanting a heat shield since that time and our 1,001 other projects have kept us from making one. Wrapping the exhaust manifold in insulation would help, but the juncture of the two manifold runners with the bolts located there make for a complex and inefficient wrap. Running the Onan only out of the box has been a work-around.

Blocking the exhaust manifold radiant heat is our main concern.

The transfer of radiant heat goes up with the fourth power of the temperature. The exhaust manifold is transferring roughly 100-150 times the heat of that from the cylinder heads and even more so of the heat from the rest of the generator set. A stainless steel heat shield covering just the manifold would be a great improvement.

Agree that three point mounting is needed to stabilize the sheet. We would prefer Stainless Steel to aluminum due to stainless steel's lower heat transfer and higher reflectivity; besides, it's just pretty. Looking forward to the availability of a heat shield of either material.

Don and Susan Jeffers
78 Eleganza II

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Re: Onan heat shield prototype [message #262238 is a reply to message #262180]

Thu, 18 September 2014 12:59

jknezek

Messages: 1057
Registered: December 2007

Karma: 5

Senior Member

My cheap Harbour Freight infrared temp gauge routinely comes back at 600+ degrees for the exhaust manifold in a few spots. It quickly dissipates to 150 degrees at the tailpipe and less at the exhaust, and I can hold my hand an inch or two above the manifold with no problem, but I was shocked at the heat where those cylinders join. Still, it's been this way since new presumably and after 35+ years haven't had much of a problem. Are we assuming the problem will get bigger as the compartment insulation fails or is it just a case of adding a piece of metal because we can?

Thanks,
Jeremy Knezek
1976 Glenbrook
Birmingham, AL

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Re: Onan heat shield prototype [message #262243 is a reply to message #262180]

Thu, 18 September 2014 13:37

djeffers

Messages: 219
Registered: June 2004

Karma: 2

Senior Member

The radiant heat from where the two cylinders of the exhaust manifold join can get hot enough to be an ignition source.

The entire manifold runs much hotter than the rest of the engine, the juncture of the two cylinders much more so.

A larger, wider shield between the manifold and the top of the gen set box would block the direct path of radiant heat, yielding a lower temperature of the shield relative to the manifold allowing the heat to be radiated onward at a much safer temperature level.

Heat shields are not uncommon for engine exhaust manifolds.

The dangerously high manifold temperature we experienced was achieved with a nearly full electrical load from both air conditioners running at high for several hours, the gen set in the box and a nearly wind still hot Florida night; apparently operating at the edge of the envelope. We would like improved heat shielding of the exhaust manifold.

Don and Susan Jeffers
78 Eleganza II

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Re: Onan heat shield prototype [message #262258 is a reply to message #262180]

Thu, 18 September 2014 16:30

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Well Kerry, I got my coach home last night and it is leaking oil when running. I pulled it out today to take a picture so you can see what I did. Now I can not find my digital camera. When (if) I find the digital camera I'll take a picture of mine.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: Onan heat shield prototype [message #262264 is a reply to message #262180]

Thu, 18 September 2014 17:54

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

Maybe the carb is on the lean edge of optimal?? Wouldn't slightly richening really drop the EGT and save the engine some grief?

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: Onan heat shield prototype [message #262351 is a reply to message #262180]

Fri, 19 September 2014 21:37

midlf

Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)

Karma: 1

Senior Member

Kerry Pinkerton wrote on Wed, 17 September 2014 20:44

http://www.gmcmhphotos.com/photos/onan-heat-shield/p55952-prototype-heat-shield-for-possible-production.html

Thoughts? It would probably be about $25. Because of the flanges it would have to go in a larger box so shipping would not be as cheap as the KISS shelves.

Kerry I suggest the shield extend down on the left side far enogh to cover the manifold to pipe connections. If these develop an exhaust leak it can send a very hot jet of exhaust into the side wall of the Onan compartment. Mine had such a leak and sustanined damage to the wiring and some charing on the side wall.

Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

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Re: Onan heat shield prototype [message #262392 is a reply to message #262180]

Sat, 20 September 2014 13:16

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

Well, I bit the bullet and invested some of my aluminum in a half dozen of these. Slightly different in construction from the photos show above but functionally the same. I'll have them with me at the rally, first come. One is spoken for so there are 5 available.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: Onan heat shield prototype [message #262421 is a reply to message #262392]

Sat, 20 September 2014 20:07

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

I want one Kerry

Ken B.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: Onan heat shield prototype [message #262422 is a reply to message #262180]

Sat, 20 September 2014 20:11

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

It's a fine line between coverage and ventilation. Adding a flap to cover than is a snap but it will REALLY cut down on air flow under the shield. Don't know which way is the best trade off but ventilation seems pretty important vs a rare failure of the pipe.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: Onan heat shield prototype [message #262426 is a reply to message #262180]

Sat, 20 September 2014 21:11

kerry pinkerton

Messages: 2565
Registered: July 2012
Location: Harvest, Al

Karma: 15

Senior Member

That said, I may have a solution. The new design uses pop rivets to hold the three mounting flanges. That makes is much simpler to make and the pop rivets are perfectly suited for this application. Adding another flange that covers the forward exhaust junction can be offset and inch or so toward the front of the coach. This will allow for ventilation and still shield the box from the heat of that area of the exhaust system. I cut some pieces to carry with us up to Wisconsin.

We're heading out with Ken Henderson in the morning. Three days on the road.

Kerry Pinkerton - North Alabama Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L

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Re: Onan heat shield prototype [message #262444 is a reply to message #262392]

Sun, 21 September 2014 03:34

djeffers

Messages: 219
Registered: June 2004

Karma: 2

Senior Member

Kerry Pinkerton wrote on Sat, 20 September 2014 14:16

Well, I bit the bullet and invested some of my aluminum in a half dozen of these. Slightly different in construction from the photos show above but functionally the same. I'll have them with me at the rally, first come. One is spoken for so there are 5 available.

We really need and want one, Kerry.

PM sent.

Don & Susan Jeffers
78 Eleganza II

[Updated on: Sun, 21 September 2014 03:39]

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Re: [GMCnet] Onan heat shield prototype [message #262475 is a reply to message #262392]

Sun, 21 September 2014 12:44

k2gkk

Messages: 4452
Registered: November 2009

Karma: -8

Senior Member

Somebody mentioned that the "shield" has some effect as a heat sink. Realizing that space above the Onan is limited, I wonder if finned heat sinks could be attached to any heat shield to help speed cooling of the shield. Silicon heat sink compound at the interface would, of course, be required.

Just a random idea worth no more than what you have paid for it.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~~ k2gkk + hotmail dot com ~~
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~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
______________
*[ ]~~~[][ ][|\
*--OO--[]---O-*

> Date: Sat, 20 Sep 2014 12:16:59 -0600
> To: gmclist@temp.gmcnet.org
> From: Pinkertonk@MCHSI.com
> Subject: Re: [GMCnet] Onan heat shield prototype
>
> Well, I bit the bullet and invested some of my aluminum in a half dozen of these. Slightly different in construction from the photos show above but
> functionally the same. I'll have them with me at the rally, first come. One is spoken for so there are 5 available.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, Manny Brakes, 1 ton, tranny also a 76 Eleganza to be re-bodied as an Art Deco car hauler

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