| Pie wagon suspension [message #192838] |
Wed, 12 December 2012 21:54 |
bryant374
Messages: 563
Registered: May 2004
Location: Pleasant Valley, NY 12569
Karma: 1
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Senior Member |
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Re: [GMCnet] Pie wagon suspension [message #192819 is a reply to message #192813 ]
Wed, 12 December 2012 19:24
James Hupy
Messages: 1829
Registered: May 2010
Senior Member
Thanks Matt. I have seen videos of the pie wagon on the test track running
over what looked like 4 x 4's, and in panic braking tests. I figures that
they must have had instrumentation on board when they did that. Sorry to
break the thread.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Wed, Dec 12, 2012 at 4:59 PM, Matt Colie <matt7323tze@gmail.com> wrote:
>
>
> James Hupy wrote on Wed, 12 December 2012 10:38
> > Matt,
> > I know this is a hijack of your thread, but, is there anywhere in
> existence the data from the "pie wagon" suspension testing? It would be
> interesting to find out what was learned, and how that shook down to final
> suspension design as far as placement of frame tabs for mounting the front
> control arms and torsion bar choices.
> > Jim Hupy
> > Salem, Or
> > 78 Gmc Royale 403
>
> Jim,
>
> I was not close to the development of the vehicle, I have lost track of
> those that I knew who were. While they were neat, I never had expectations
> of actually owning one at the time.
>
> Matt
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will
> find
> SE Michigan - Twixt A2 and Detroit
>
>
>
I have moved the "pie wagon suspension" to a new thread since there are a number of corrections, definitions and explainations that need to be made.
References are from the GMC Motorhome History CD and other documents as noted.
1. The pie wagon was built as a feasability vehicle by Ralph Merkle (Product Development Engineer for the Motorhome) to demonstrate the hydropneumatic suspension to GMC management. It used a body from Union City Body Co. and did not look anything like a GMC Motorhome (see pg. 36 of history CD).
The Motorhome going over the "4X4s" was an early production motorhome, NOT the pie wagon.
2. Hydropneumatic spring testing probably had little to no actual testing since it was replaced during the build of the prototypes used in the testing program. The "square sides" (first of the prototypes) can be seen for only a few seconds in one of the Mini Theatre showroom films and was likely the only GMC Motorhome to see any testing of the early suspension.
3. The air bag had lab tests simulating 3,500 Belgin Block miles as well as road tests to the Upper Peninsula and Florida. Many miles were also accumulated at the test track, we have pictures of instrumented GMC Motorhomes.
4. I have a thesis entitled, "Directional Control Analysis of the GMC Motorhome, by K. Gross dated june 1972 which identifies a number of tests for the air bag. I provided this to others at the DuQuoin convention thinking it might be of interest to other GMC techies, but got no comments back.
5. Air bags:
Goodyear submitted a design using a long cylinderical spring, having one piston and one bag convolution (12-30-70). Interference between the piston and rubber sleeve caused the double piston design to be developed and used in production with only minor modifications.
6. The front suspension was pretty much fixed from usage of Toronado and 4 other motorhomes that predated the GMC. Torsion bars were likely easily defined by load requirements, etc. I know the shocks were changed during production at least twice.
7. Other references of interest:
History CD
#38 photo of hydropneumatic suspension (pie wagon)
#39 first sketch of air bag
#55 Preproduction "strait sides" w/ hydro spring
#62 first airbag
#63 preproduction
Bill Bryant
PO 1976~PB (owned 34 years)
1914 Ford (owned 70 years)
1965 Corvette (owned 39 years)
GMC Motorhome History
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