LocostUSA.com

Hi all,

Been designing the LCA. Looks like this design is by far the easiest to make.

A few points here:
1. Two round tubes + steel plates ; just cut tubes, tap tubes , cut and drill steel plates, and weld them together. It can't get easier than that.
2. This design is for miata LBJ. It can also be used for other bolt-up type of ball joints. Just drill mounting holes on the steel plate
3. I do have to watch out for the angle of heim joints. If needs adjustment, I can change the angle of the two tubes to reduce the heim joint working angle. But will have to see if the LCA can fit inside rim.

Any foreseeable issues? or suggestions?

that is a common design similar to mine. where will you have the shock pickup point? I don't see it on your drawing. As you said you need to keep an eye on the heim joint angles, but also make sure they don't bind against the frame in droop.

_________________
Build on

Chris
Build: NA Miata based +221 Se7en

It should be easy to build, but heavier for it. The rod end angles do add some adjustment complexity. Is there any non-visible bracing spanning between the two tubes on the underside of the plate?

_________________
-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

The front LCA on my MG midget using Miata ball joints is similar, but a little smaller overall.

I had the tubes in plane with the cross bolt and ended them right before the cross bolt. I cut the tube at an angle and bent a piece on each side to pick up the cross bolt. Then I have a horizontal web plate that I have the vertical bolt running into. I did not run pieces along the sides of the cross bolt back to the web.
I unfortunately don't have pictures of making them I converted from the original design which used RX7 LBJ's. The LBJ is at an angle to restore caster since I was lazy and re-used the A-arms without redoing most of it.
You can see them in the background of the following pictures.

Here is one recent from when I was adding tow hooks to the car. The car has survived ~10 Trackdays, ~200 Autox Runs, and probably 500 street miles with no issues with the lower A-arms.

_________________
MG midget bodied Locostish car in progress

To the OP, it'll work fine, but know that the geometry will only be as designed in one position of the rod ends. Because they're canted outward, the spacing between them changes as they're screwed in or out. Yes, some adjustment is available, but will require different spacers or washer after each adjustment (so that the brackets aren't crushed when the bolts are tightened). Any wheel alignment changes will probably be easier and faster by changing the upper A-arm instead (assuming that it has more freedom of adjustment).

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/