Start Your Go-Fast Build-Front Suspension

[philofab]

Hmm, I had more issues with my five speed at 60+ in 4lo than the front axle did.

[baja-chris]

More progress on the front suspension today. Set the wheel base, 1.5" over stock measured from the rear axle which is in stock location. Welded a temporary spacer in at ride height (7" down from full bump) and another to lock in the caster which we set to 9 degrees at ride height.

[baja-chris]

With the front end finally located, we designed and built the radius arm brackets. The radius arm heims will go on the outside of these brackets (below the frame) and in some of the pics you can see a long fe-fe which will have a tube that runs up to the cross member which runs over the tranny.

[baja-chris]

A few more pics of the front radius arm brackets.

[baja-chris]

Here's a pic of the front diff vent tank on Ole Yellar. You can't see the top of the tank but it just has a hose to atmosphere (with a small air filter on it).

[Andy Jones]

What dual rate spring length's are you guy's putting on a 14" shock.??

[baja-chris]

So what is go fast front suspension without go faster steering? Next up is dual relay arm steering with ram assist and a 4 bolt, inside the frame Saginaw race box. We will use a 2:1 doubler on the steering column in addition to the speed up we get from the ratios on the relay arms. The packaging is tight.

At the upright, we are using the stock tie rod locations but with steel plate added to put the tie rod end bolts in double shear and of course the taper drilled out over sized with a machined 4130 steel insert put into the casting to keep the hole from ovaling out. All the steering heims are 7/8" with 5/8" bolts. Trophy truck sized stuff to reduce maintenance costs between races.

My thought on the location of the relay arms was that the inboard tie rod ends should be exactly in line with an imaginary line drawn through the middle of the suspension pivots. So we dropped a plum bob from the bearing center of the radius arm heim and another from the uniball in the TTB beam. Then drew a line on the floor that went through these two points and projected out under where the steering relay arms might be. But that only covers two dimensions X & Y. To pick up the third dimension, Z, we measured the height of each of the suspension pivots (radius arm and beam bearings), did some math on ratios and figured out how high from the floor the inner tie rod bearing should be to fall exactly on this imaginary line is space. The idea is that as the suspension moves, if the tie rod pivots on exactly the same plane then there should be no bump steer.

Anyway it's hard to get this exact. The result is that we needed the inner tie rod ends to be where they are shown in the photos and inboard swingers worked best for this. Note that the relay arms are asymetrical because we are using stock asymetrical beam pivots (which make for symetrical motion arcs as opposed to equal length beams which make asymetrical motion arcs since one beam must be ahead of the other.)

With the inner tie rod ends located we mocked up relay arms and tie rods and cycled everything (again). Over 20" of front travel we have about 1/4" of bump steer but almost all of it is at full droop and does not matter as much. We probably missed the imaginary ideal location by a little bit. Close enough.

So then we started fabricating real parts and swapping them in place of the mock up parts. For the relay arms, we used a 2.5" dia 4130 tube and milled out the inside on the lathe to accept a uniball. Then we machined a crush sleve to go between these. The relay arm then sits between two plates and is torqued to the max of the thought bolt. This design is simple, low maintenance and can handle high side loads.

[baja-chris]

More steering mock up photos.

[baja-chris]

Two more.

[Mojo]

that steering setup looks awesome, good work......

[SteveG]

How much caster are you going to run, Chris?

[ESHALLBETTER]

I believe he said 9 degress.

Also, this truck needs a build thread!

[ChaseTruck754]

I believe he said 9 degress.

Also, this truck needs a build thread!

Yup & yup!

Funny thing is I was looking at the post that had that caster # just now before I scrolled down & saw Steve ask....

More progress on the front suspension today. Set the wheel base, 1.5" over stock measured from the rear axle which is in stock location. Welded a temporary spacer in at ride height (7" down from full bump) and another to lock in the caster which we set to 9 degrees at ride height.

[Kel Fab Creations]

How much material are u guys machining off the uniball cups to allow for enough rocking of the beam. Right now I have the cup at 1.350 total width. (took off .075 on each side) not sure if I should go too much more. Don't wanna make the snap ring wall too thin.

[baja-chris]

None. 1" uniball and did not have to machine anything from the cup for it to cycle. Maybe it rocks less because the radius arm is longer? It cycles 20" and is 3" over width (1.5" per side).

[philofab]

My cups get really close but do not bind. Did you start with a narrow cup?

[Kel Fab Creations]

How wide is a narrow cup lol. It was the narrowest one they had at tabzone.com

[ESHALLBETTER]

I believe the narrowest cups I've used are are 1.5" wide.

[Kel Fab Creations]

K. I'll have plenty of clearance now. Thanks guys.

[Frontrunner54]

Build thread for sure... Seeing a build without the body is a whole new experience.

Those steering mockup pics are like gold. Ive been looking for some good swinger, dual swinger, and swinger mount pics for a while.... Especially at bump, droop, and ride height, and with all the angles...

Thanks for posting em!