1961 American front suspension rebuild

yeah, i'm too much of an engineer to weld  a kludge together like that! but i understand the impulse -- it's a PITA to get this stuff done right.

tomorrow i should get all four wheels back on the ground for the "last" time. it's coming out quite nicely -- camber and caster independently settable. camber easily adjusts with a twist to 3 degrees negative (much too much, i'll be running -1 degree).  of course no real caster available with the lower trunnion, but i can at least set it neatly to 0! then the later balljoint will let me fix that.


the upper arms are simple tubes with heims. by themselves, the trunnion can shift back and forth (actually it swings in a funny shallow complex arc), the four heims make a parallelogram. this conveniently allows adjusting caster nearly independently of camber (over a few degrees).  a plate (not shown here) bolts across the top, onto the two two-hole tabs welded to the arms, and holds "caster" fixed, preventing the parallelgram from shifting.  it also holds a bumper for the trunnion casting to hit when the suspension is at full drop (saving the air springs).

tomorrow i'll install it and take the rest of the pictures.

farna wrote: IIRC the trunnion studs are 5/8" standard threads. I'm pretty sure they aren't long enough to get a heim joint and a nut on though, and they are pretty hard.

they're not 5/8, i just checked one. it's about 3/4", but it looks like it's "semi-acme" threaded, i dont think it (or the upper, actually) is UNC threaded, though that is 5/8", 11 TPI.  but of course most used ones are worn to razor sharp peaks. and the length is short.

but i get what you're saying -- that is an approach to look at.

i now have a large pile of clean but used suspension parts. my experience this year will decided what i do with them...

just another couple pics. i have some wiring to do before i can start and drive it. hopefully in a week.

here are the arm halves attached to the '70 Mustang cross shaft bar that has the 1 inch "shelby drop" included. since the photo was taken square-on perspective and depth is ruined but it shows some of the relationships.




the arm ends hanging down in the photo above swing up and bolt to the existing cast trunnion via the (sloppy) threaded hole through the casting, using a length of (quality, low carbon, US made steel) threaded rod, 7.5" long. the heims are sitting on high-error spacers to accommodate the rather broad angle. at the cross shaft end the spacers are 1/4", here at the trunnion 3/4". this is far more than necessary to avoid contact, it was fine when all were the more common .33", but this lowers the overall angle and there's plenty of room; this stack of hardware clears tire and rim by a couple inches.




the funny thing about this is that what i think was one of the worst design features of this suspension, this difficult trunnion casting, is now the strongest. the knuckle pivot (needle roller and thrust bearing) are great, and the sloppy threaded pivot is no longer a moving part.

if there was more room at the chassis -- or if you were willing to chop out sheet metal -- a "ford" rubber bushed rod end would work just fine and restore some compliance. the outer end too, there's enough room for rubber bushings there (ford type) but in fact i'd prefer the rigid heims there, they're not doing a lot of work and they're more compact. (the lower control arm will be rubber bushed, as there's plenty of room on bottom.)

last, here's the "back" side of the upper arm.

OK i updated the project website to include all this stuff. many pics and procedures on how to may poly bushings for stock replacement too.

http://sr-ix.com/AMC/1961-Rambler-Roadster/front-suspension/index.html

farna wrote: That last pic shows why there isn't enough room for rubber bushed rod ends.

exactly. the bolts and heims and spacer stack *just* clears, sheet of paper thin one side, so i tapped the pocket out so i had 1/8" clearance. but the upper should be less noise sensitive than the lowers -- also most noise transmission is i think via the steel spring, hence all the pads etc, and the airbag solved that one.

Looks like there would be enough if using the stock mounting bar though.

dont think so. the AMC bushings are not only 9/16" ID (unique) but short. the Ford type are 1.5" plus hardware, so no-go, or not worth, to me, the extra engineering effort.

RideTech rubber bushed rod ends (not poly!) with a bend in the rod at the inner end would work well. Or use a piece of tubing that a bushing (RideTech or Ford stock style) would fit and weld the rods at the correct angle.

a huge improvement of the "ford" type over AMC is that the pivot is a bolt, not a stud. most of the aftermarket welded U-shaped arms are one piece, and assume a bolt pivot you couldn't install it on the AMC stud type. also the AMC stud is utterly unique, 9/16". IMPOSSIBLE to find any bushing or joint that ID.

I think I'd go with the thinner spacers on both sides and use a thinner jam nut instead of a standard thickness nut. Would be just for aesthetics... not that anyone would see it unless changing a tire though.

engineering won over aesthetic. the set of spacers chosen makes the arms substantially more parallel, the joint loading is much more square. the long trunnion stud more easily prevents rotational forced with less energy (longer lever). it only looks a little funny :-)

I'm sure you don't take my comments as anything more than CONSTRUCTIVE criticism at the most... really just adding my thoughts.

oh of course! never worry about that! it's a conversation, your ideas usually have affected some aspect of what i'm building or thinking.

time will tell but in the upper arm i think the heims will be fine. the QA1 Endura series are one piece injection seats, no lube, and are already dust tight. motion is only in one plane (up/down). forces are quite low. they're 90-degrees from all of the impulse forces (curbs and even turns) so noise/vibration and therefore wear should be relatively low.

we;ll see though of course. and they're $15 each, 50K miles, even, would be fine. changing ther heims would take a half hour, all i gotta do is take the wheel off, let the air out of the spring, unbolt the cross shaft thingie. adjust for the identical lengths and it wouldn't even affect camber.

but materials in motion have their own rules, we can only be patient and discover them as we go :-) hopefully ive ainticipated the big chunks.