Re: [Amc-list] truck arms

[Wrambler242@xxxxxxxxxxx]

I know you've stressed out about this from all the thinking you've done on it, But I wonder, so what? If the axle tries to stay flat on the ground, ok by me. The original truck arms are two I beams and will flex as far as I can tell. Rubber bushings in the front will help this too.
Nascar doesn't care too much about this as long as they get thru a race.
 I know ladder bars suffer the same conditions. It's not a perfect world. I'm putting it under frikkin' Rambler. Not a Benz or a Beemer! 
  You do a lot of DD duty with yours, back here in the "rustbelt" us peeps don't get to drive our old stuff for long if we try to do it year round!  It has been 40 degree highs with rain for several weeks now. Snow before that, Crap a gunk everywhere. Hey, I had 29 hours of work time in when I got to work this morning. A non rolling rear axle will only bother me as much as the non synchro 1st in that Anerican does you! Then I can get in my American or Dakota or Altima or Cherokee!
   This was written in good humour! No flames or hard feelings are intended!
I apologize in advance if it seems too flippant! :] LOL!
--
Mark Price
Morgantown, WV
1969 AMC Rambler, 4.0L, EFI, T-5

 -------------- Original message ----------------------
From: Tom Jennings <tomj@xxxxxxx>
> Mark, one thing I don't see in a lot of these truck-arm schemes
> is explicitly allowing for roll. They all go up and down fine. I
> realize also that the angled arms helps, but a flat pivot that
> flexes in only one plane simply can't work.
> 
> They might "get away with it" due to combined tolerances, flex
> and the give of rubber bushings, but it is at least stressful
> on critical parts.
> 
> (By roll I mean, hold the car level, raise the left rear wheel
> and lower the right rear wheel.)
> 
> Torque tube AMCs behave perfectly here.
> 
> Open Hitchkiss style with rear leafs throws the pinion angle
> off very slightly in two planes but obviously not enough to
> worry about (it's worked for 80 years).
> 
> 
> 
> When I was contemplating such a thing for a torque tube car,
> the simplest fittable scheme I came up with was two very long
> (6 foot) "arms".
> 
> At the trans crossmember end, they have threaded ends like an AMC
> front suspension strut. They connect at the trans crossmember
> with ordinary AMC front strut bushings into a suitable (1/4"
> thick) bracket on either side of, and as close as possible to,
> the driveshaft.
> 
> At the axle end, the arm end fits into a tubular socket (say
> 6" long for ease of construction) affixed to the axle tube.
> This socket would be angled on the axle tube, looking down from
> the top.
> 
> With 6 foot arms there would be little motion at the strut
> bushings.  Threaded ends would allow rear alignment. Axle
> wrap-up would be easily held by the long arms. The motion at
> the bushing end would be no more than in the front suspension.
> 
> It STILL doesn't properly handle the distortion of the
> axle-arm-arm triangle. If you look at old Model-T type rear
> wishbones, they have an actual ball and socket at the x-member
> end; this lets the axle-arm-arm triangle rotate without
> distortion.
> 
> 
> (I think copying the Model-T geometry, with a "V" of rigid arms
> attached to the rear axle tube, the apex of the "V" connecting
> to the trans x-member with a single ball joint, would actually
> be best.  To keep the ball joint off the ground it would need
> some U-shaped up-and-over the driveshaft or something.)
> 
> 
> 
> For body roll: the force on the arms is somewhat complex.
> The triangle of the axle+arm+arm wants to rotate against it's
> virtual apex, which would be a foot or more in front of where
> the bushings mount into the x-member.  So it distorts in two
> planes (this is the critical part) causing stress on the arms
> and joints. This translates to the arms *rotating in place*,
> twisting lengthwise, but not simply. A pivot in the rear
> and rubber in front will relieve nearly all of this, but not
> all. There is non-fore-aft force on the strut bushings during
> this time, but with the arm length no more than on the front
> suspension strut.
> 
> Even doing the whole thing with heims at both ends of the arms
> does NOT eliminate the torquing of the axle-arm-arm triangle.
> _______________________________________________
> Amc-list mailing list
> Amc-list@xxxxxxxxxxxx
> http://www.amc-list.com/mailman/listinfo/amc-list

_______________________________________________
Amc-list mailing list
Amc-list@xxxxxxxxxxxx
http://www.amc-list.com/mailman/listinfo/amc-list