Alex's Big Block Chevy Locost

[Shevalev]

so just to fully confirm. The tube and the lower collar ring will be replaced with this tube. http://www.speedwaymotors.com/AFCO-2002 ... 24526.html Is this part ok to use with the current mounts? the new tube will have an angle of around 12 degrees.

[KB58]

That upper inboard rod end looks like it may be near its limit of travel for misalignment.

[Bent Wrench]

I have never seen those arms used at an angle always at 90° to centerline.

If you angle the arm it will travel in a compound arc and it will not be possible to keep the shock square to the arm.

[Bent Wrench]

If you want to keep the same mounts I would consider a fabricated lower arm.

As shown here http://www.gwellwood.com/project-cars/the-lethal-locost/lethal-suspension/

[horizenjob]

Bent Wrench, thanks for taking so much time to give answers and provide links etc. It's a big help. I was stumped when Alex said he saw the setup on many oval track cars, it seemed like it wouldn't work. The devil is in the details.

If you angle the arm it will travel in a compound arc and it will not be possible to keep the shock square to the arm.

In most of the arms that Bent Wrench linked to, they work because the coilover, ball joint and inner joint are all in a line. You can use either a bush or a spherical joint in the coilover and the clevis on the tab does not need to provide much effort to keep the entire setup stable. If it's at an angle at some point you are again putting a lot of force into trying to pry open the clevis.

What I like about those parts is it's relatively easy to figure out their strength and the tabs holding the coilover strengthen the tube and are welded to the sides of the tube so if you weld carefully the metal in the tube does not have HAZ on the top and bottom where it is using it's strength to carry the load to the coilover.

The more traditional Locost style also has advantages, but there are pitfalls and we see that with the occasional failures...

[turbo_bird]

Failure? Sounds like me. Yup that's no fun. I had an arm break last summer on my car. Here's what the one that broke looked like, and the other side that was pretty close to following.
These were store bought suspension arms, from a company that's long out of business now. And here's compared to the replacements I made.
A very good lesson in how not to build stuff, as well as take a look at things once in a while to make sure it's still holding together. Also a good lesson in listening to others, I built the replacements from 3/4" x .065" tube instead of the more common 1" that was also recommended while I was making the new ones. The new ones now have a very slight bend in the tubes, and I will be making another set this winter. I used poly bushings in mine because that's what I had on hand, but it would be easier to weld in some threaded bungs and use him joints, which I will probably do on the next version.
Kristian

[Shevalev]

Wow, thank you so much guys. I am officially sold on the idea of this http://www.speedwaymotors.com/AFCO-2002 ... 24526.html I called speedway motors today and got some dimensions: overall length is 16.25, from the swaged end to the center of the sleeve is 15 inches, the threads are 5/8 - 18 and there is around 1.5 inches of thread so if it is too long i can just trim it down. The length of the imaginary arm that is perpendicular to the chassis from center of the pivot to the center of the joint is 16.8 inches. I am going to order all of this tomorrow and i shall start looking into shock options. Today i remade my lower mount to for the new lower arm. I still need to grind off the old one, and then began to make the jig and mounts for the rear control arms. Thank you so much Bent Wrench and horizenjob for the advice. Now i would like to ask you guys the question about the upper heim joints. The two joints for the upper and the lower control arm will require high misalignment spacers. here is the link http://www.qa1.net/rod-ends-and-related ... nt-spacers what do you think of this? How will they take the force? The joints are made for 32 degrees of angle both ways and have a static load for 40000lbs. Thanks in advance.

[Shevalev]

So today i called AFCO to get some more dimensions and i have attached them below in some of the pictures for the lower control arms because apparently they use a strut bar and i cant attach a clevis and would have to redo my mounts again. So then i thought again and did some more looking around and was wanting to get some more ideas about a setup like this one. http://www.enigmaracing.co.uk/august-2008-update/ The only difference that i see with my rookie eyes compared to my original design is that the tube is welded that attaches to the sleeve. Would it work if i just weld the tube to the threaded rod on the lower control arm of my original design and call it a day?

[horizenjob]

What's a strut bar and why can't you attach a clevis?

You can buy the rings that a balljoint screws into just by themselves. That's what's on the end of the AFCO piece you show there. Then you cold weld up the whole arm, tubes directly to the ball joint cup.

You can buy tubes that are like the one in AFCO picture and cut them in half if you like the nice "swedged" ends...

[Shevalev]

Okay that is what i thought. I don't particularly like to weld any control arms since the jig may be inaccurate or the welding could be off. The other option I thought of was to bolt a 3/8 inch plate underneath the flat plate with the 2 bolt holes and just attach a clevis to that, but then the main arm would be under an angle... should i just grind off the bottom piece and weld on a tab for the clevis? any ideas what to do with the current part instead of going and making it all from scratch?

[Shevalev]

so, i just did some more observations and i tried to incorporate all of the forces in the front suspension and i don't believe i explained my idea quite clearly. Below are 2 pictures attached of the setup that i want to use. The first picture is the setup overall and the second picture is the way that the shock will be mounting on to the control arm/balljoint sleeve.
Going by the first image:
Lower Control Arm

1. there will be a vertical force applied to the lower control arm when going over a bump
-When going over a bump the shock will absorb the initial stroke of the knuckle going up and down which is attached to the balljoint sleeve which is attached to the ball joint itself
-the clevis is not designed to take a load like this (vertical force in the position that it is pictured), however, the shock is the part that will be taking 100% of the impact when the clevis will be there to only stabilize the knuckle laterally due to the shock being directly attached to the ball joint
2. there will be a horizontal force on the lower control arm when the car will have its brakes being applied
-under braking the clevis and the rod ends are designed to take a lateral load

Upper Control Arm

1. there will be a vertical force applied to the upper control arm when going over a bump
-this upper control arm setup is found on many aftermarket applications
2. there will be a horizontal force on the upper control arm when the car will have its brakes being applied
-this upper control arm setup is found on many aftermarket applications

The second picture shows the way that i will be intending to mount the shock to the ball joint sleeve. The shock will be the part that mainly prevents this setup from rotating that will alter that caster of the wheel.

Could you guys explain to me what is wrong in this scenario?

[a.moore]

I think you're over thinking the arm design. As long as you can weld you can build arms using the pieces Marcus mentioned. Pretty much everyone on here has gone that route.

Jack at Kinetic also offers an arm kit for Miata spindles: http://www.kineticvehicles.com/ControlArms.html

If you're really apprehensive about doing a more traditional arm design, you can probably build something similar to his using a sleeve available for your balljoint of choice.

[esp42089]

You can try it this way, but it is straying away from the tribal knowledge, putting you in uncharted territory. That balljoint/clevis mount was meant for an upper control arm that takes significantly less load than the lower arm and no bending moments. Where you've got the shock is still cantilevered, just less-so.

You've got a big block sitting in the front of your chassis, putting you hundreds of pounds over the weight of the traditional light-weight locosts built on this site where this tribal knowledge evolved from. Most guys go bigger and beefier if they go faster or heavier in some way to try and compensate for how they've changed it.

There is a thread on here with video of a guy on the track in his locost. The front lower control arm broke off the frame, that corner went down and he slid straight off the track, across the grass, and over a small 3 foot hill becoming airborne. The landing crushed his spine. I haven't seen him around here and don't know if he ever recovered enough to drive again. Out on the streets, there are more things than a grassy hill to hit when your front corner drops. These are not safe vehicles.

If you go with it, please check it frequently and report back. I'd recommend painting it a light color, like grey or white, to make spotting cracks easier. It would be valuable for the community to learn if this is a durable construction method for these cars.

[Bent Wrench]

so, i just did some more observations and i tried to incorporate all of the forces in the front suspension and i don't believe i explained my idea quite clearly. Below are 2 pictures attached of the setup that i want to use. The first picture is the setup overall and the second picture is the way that the shock will be mounting on to the control arm/balljoint sleeve.
Going by the first image:
Lower Control Arm

1. there will be a vertical force applied to the lower control arm when going over a bump
-When going over a bump the shock will absorb the initial stroke of the knuckle going up and down which is attached to the balljoint sleeve which is attached to the ball joint itself
-the clevis is not designed to take a load like this (vertical force in the position that it is pictured), however, the shock is the part that will be taking 100% of the impact when the clevis will be there to only stabilize the knuckle laterally due to the shock being directly attached to the ball joint
2. there will be a horizontal force on the lower control arm when the car will have its brakes being applied
-under braking the clevis and the rod ends are designed to take a lateral load

Upper Control Arm

1. there will be a vertical force applied to the upper control arm when going over a bump
-this upper control arm setup is found on many aftermarket applications
2. there will be a horizontal force on the upper control arm when the car will have its brakes being applied
-this upper control arm setup is found on many aftermarket applications

The second picture shows the way that i will be intending to mount the shock to the ball joint sleeve. The shock will be the part that mainly prevents this setup from rotating that will alter that caster of the wheel.

Could you guys explain to me what is wrong in this scenario?

There are no vertical forces applied to the upper joint other than the inertia of the arm and joint.
All loads controlled by the upper joint are lateral or roughly at right angles to the joint axis.

The lower joint has huge vertical loads from the weight of the vehicle and the shock controlling wheel motion.
This is why I am concerned about using a joint that is not designed for the lower position.
A lower joint must be able to withstand the vehicle weight & impacts trying to rip the ball out of the joint.

Your upper arms are fine as long as you use an inboard shock, I'm not sure you can get the shock stood up enough for maximum effectiveness.
The joint holder you are using on the bottom will give more room for an outboard shock in the upper position.

For your lower arm, that ball joint mount will not work
It is going to apply a bending force to the threaded portion of the joint holder.
It is going to apply similar forces to the clevis that it is not designed to take.
There will be a moment of uncontrolled suspension movement as the joint tips, that tipping will "work" on the clevis and threaded joints likely causing failure.

Jack's arms control the tipping forces of the joint by solidly attaching the joint to the arm.
His arm is the same concept as the Afco arm,

the joint is solidly affixed to the arm and the shock loading is in line with both the inner and outer pivot axis so there is no tipping.
The Afco arm does not appear as strong as Jack's,
His arms look heavy compared to this, unsprung weight is to be avoided when practical.



Not the black arm, that is the breakable one, the same forces that break those arms will cause yours to fail
This arm can be made adjustable by welding threaded spuds onto them at right angles to the motion and using rod ends to make the joints instead of the bushing setup as shown.
Note that the arm ends at the bolts which are centered on the axis of the joint, the gussets of the shock mount tie closely to the 3rd joint bolt and the flat plate ties it all together.
There is also a third gusset to the inside of the shock mount to triangulates between the shock mount and the plate and tubes.

[Shevalev]

Okay. I am sold on not using my original setup. So just to clarify if I use the afco arm and it will be in a perpendicular orientation to the lower suspension pivot line that should hold or will not hold? The arm is made out of .110 DOM tubing and my intention is to have the front end weigh at most 1000 lbs.

For the lower balljoint that i currently have, it is a k727 with a k772 stud inside it from QA1. This balljoint is designed to be in the lower position. Thank you very much for the enlightenment. I had to draw myself a diagram to understand some of the forces. Maybe i will go around to animate this even for newbies like me to understand this better in the future.

The other question i have is, since i am going with the afco control arm, cant i just use the shock in the outboard position? The shock will be positioned at around a 34 degree angle. I know that i have to compensate with the spring rate for this angle. If i do manage to make room for it to fit, i dont see why to complicate this suspension and limit the space even more when i have them inboard mounted. After all i will have a big block in there.

Here is another picture of the progress that i have so far. Got the upper mounts done for the rear. Waiting to restock on Monday with some metal to finish off the lower mounts and then to reinforce the diff and rear end area. The front suspension parts should arrive on Wednesday so hopefully everything will hold and fit for me.