Building a-arms soon.. need pro advice on design.

Hey guys, just signed up here but should have done it long ago...

well im building a 4 door 85 silverado and this is what i have so far

the lower arms and uppers i want to use Delrin bushings (should i use heims for uppers??)

for the spindle attachment on the lower arm , from what i have came up with is

1.5" uniball cups welded to the end of LCA
1.5 uniball with snap ring

spindle...

Misalignemet spacers and am going to see about modding my stock spindle to mount the uniball and misalignment spacer on like a clevis setup..


spindle to UCA

sideway 1.5 uniball( should i use the uniball cup and snap ring on top too?)

UCA bolts on to that sideway uniball with misalignment spacers in both sides .

and 7/8 heims (outer tie rod) and 1 1/4 heim (inner tie rod)

thats what i have so far... this is my first build of this kind so please excuse the "noobish" nature of my post...

so please any advice or better setup on a budget that you know is better i would appreciate it very much!

thanks guys
 
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TauMau

Well-Known Member
Be careful mounting uniballs sideways...it causes steering to be extremely limited. If I were in your position I'd do:

UCA: Heim Inner/Vertical uniball outer (Bolt passes through the uniball vertically)
LCA: Bushing Inner/Vertical uniball outer

IMO that'd give you the best combination of steering/travel/adjustability
 
great advice.. thanks for that.. i honestly thought mounting the uni sideways on the spindle would be the better design.. but now that you mention it it makes sence.


on the outer uniball on the LCA should i use the same size misalignment spacers on top and bottom of the uniball?

im thinking about modding the spindles off a 1 ton chevy.. but it is a cast piece.. whats your thought?? i dont have the money to buy a pricey spindle right at the moment.
 

TauMau

Well-Known Member
You ought to hit up "scottm" from this thread with your questions:

http://www.race-dezert.com/forum/showthread.php?t=62194

His truck is running vertical UCA uniballs so maybe it isn't such a big deal? For your spindles have you thought about making your own? Scroll down to post #9 in that thread and you can see how simple they can be to make.
 

dirtdudeaz

Well-Known Member
So when you say UCA vertical uniballs, the bolt goes horizontal?

That's what it's looking like in those pics
 

TauMau

Well-Known Member
His truck is running vertical UCA uniballs so maybe it isn't such a big deal? For your spindles have you thought about making your own? Scroll down to post #9 in that thread and you can see how simple they can be to make.
So when you say UCA vertical uniballs, the bolt goes horizontal?

That's what it's looking like in those pics
Yeah I meant his truck is running "horizontal" UCA uniballs meaning the bolts are running horizontally on the arm...thought one thing and typed another
 

Scott_F

Well-Known Member
The conventional definition is:

Vertical Uniball = horizontal bolt
Horizontal Uniball = vertical bolt
 

TauMau

Well-Known Member
Thanks for the clarification Scott. I suppose I've caused enough confusion in this thread for one day. :(
 

motorhead

Well-Known Member
7/8 heims (outer tie rod) and 1 1/4 heim (inner tie rod)
1.25 shank heim is pointless, unless you plan to make your tie rods from 1.75 tube. I consider 7/8 big as well, but would agree its not too big if you want your steering to be the last thing to break or the vehicle is over 4000lbs.

Also, I don't see a reason a stronger heim would be needed at either end. When the suspension is drooped and encounters a side load causing the wheel to want to turn, very little vehicle weight is actually straining the heim shank or bolt. When the tie rod is parrallel to the ground, usually near ride height, the heim shank see only compression on the outside tire, making the only weak link the bolt shearing. From ride height up to bump is where I consider the heim shank to be most vulnerable to failure. The more bump travel the more strain on the heim shank, but not necessarily on the bolt. I don't really know why I typed all of that, I guess to try and sound smart and remind myself where the loads need to be anticipated and calculated.
 

atomicjoe23

Well-Known Member
From personal experience I would run the largest strongest rod ends in you can. . .and run equal sizes. . .

. . .if you run unequal sizes you are designing a weak point into the system. . .something to be avoided unless you are trying to have a preferential breaking point to keep from damaging a really expensive part or multiple parts. . .

on a 650 lb. (without driver) single seat buggy we are using 1/2" rod ends for everything because we bent everything smaller than that. . .if you are any sort of vehicle weighing over 1000 lbs. I would not use anything smaller than 3/4" (so 7/8" is fine, but why the mismatch???) just because I've seen them bend (almost 90*. . .they didn't break but they sure did bend!!!). . .
 
thanks for that advice... I suppose i will run 7/8s inners and outers...

now about they uniballs and misalignment spacers... what sizes should i run? Im leaning more towards fabbing up my own spindles but not sure yet...

as far as the arms... i want to make boxed lowers and a custom subframe, removing the stock subframe and making my own. what thickness sheetmetal will be the best to use on the arms?

as far as upper arms... what thickness tube should i use? will have to tap the ends for heims to screw on?
 

TauMau

Well-Known Member
as far as upper arms... what thickness tube should i use? will have to tap the ends for heims to screw on?
Negative on the tapping, that's what these are for:

http://www.racereadyproducts.com/fk-rod-ends-and-bearings/fk-weldable-tube-ends/

and these:
http://www.racereadyproducts.com/light-racing-chassis-components/

Tubing is subjective based on vehicle weight, intent of use, etc. Use chromolly and I'd suggest 1.75x.120 minimum.

My baja is super light weight and the uppers are 1.5x.120 chromo but I'm still planning on heavily gusseting them.
 

CRAIG_HALL

Well-Known Member
The outer TRE (tie rod end) see more use than the inner, the reason most truck use a larger heim there (it has more surface area).
Usually the inner just pivot up & down similiar to the arms and swings for & aft just a few degrees. The outer swings both degrees 25-35° depend ing on travel and steering angle.
 
ya I see what you mean.

as far as arm lengths.. know that there has to be certain lenghts corresponding to each other..

is there a formula or a basic rule of thumb on UCA and LCA lenghts?
 

atomicjoe23

Well-Known Member
ya I see what you mean.

as far as arm lengths.. know that there has to be certain lenghts corresponding to each other..

is there a formula or a basic rule of thumb on UCA and LCA lenghts?
the UCA's should be between 50%-80% of the length of the LCA's, that is a rough thumbrule and there are variations. . .the shorter UCA pulls the top of the upright in as the suspension compresses causing you to gain negative camber. . .this will cause the camber relationship between the tire and the ground to change less during cornering (due to body roll) than if you ran equal length upper and lower control arms. . .what you want to shoot for is as little change in roll center location in bump and roll so you will have to play with your numbers some to see what the optimum ratio will be for your particular set-up. . .and I only touched on basically one variable of suspension design. . .

what gauge steel should I use? both sheet metal and Tubing? Im not exactly sure what to go with ..
for the plate/sheet for the LCA's use 0.120" for the main structure and if you are gonna do any additional bracing in high stress areas (i.e. shock mounting area) then use 0.090" on top of the 0.120". . .that's what the pro's use that you pay mucho dinero for. . .

. . .for the tubing I'm assuming that you are talking about the UCA's and that would depend upon the vehicle weight. . .
 
thanks a lot man.. yes i think im going to do boxed uppers and lowers.. but im thinking on using bushings for the LCA inners..
 

atomicjoe23

Well-Known Member
On the front A-arm suspension that I just built we used bushings for the chassis side pivots on both the upper and lower control arms. . .that was a small single seat buggy though. . .

. . .I'm currently planning a two-seat V-8 powered budget play buggy and I will be using rod ends for the inner pivots (UCA & LCA) and will be using uniballs on the upright. . .
 
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