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 <
> 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
>
> > 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
>
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