GRM Formula Car

These are some pictures of the formula car I built. I started from scratch with an Autocad design, a pile of steel, a 2008 Suzuki GSXR 750 engine, and Miata uprights. I began the build at Christmas time 2010 and ran it down the street last Christmas. It doesn't fit into any SCCA class. I built it to include features that I thought would be fun to play with at autocrosses and track days.

I am working with a very tight budget and will be making future additions/changes as I go. Any bodywork, wings, etc. are yet to come. Sorry for the poor quality phone pics. I will answer any questions you may have.

Very cool!

What diff are you using?

Looks like you're running with just a hand clutch for getting started, shifter-kart style?

Badass! Looks a lot like a larger FSAE car, I like what you did with the jackshaft off the transmission to keep the diff centered.

I love it! Nice work.

Very nice...

Looks like you dual purposed the handlebar with the clutch and gear selector?

Very cool. My son raced superbike powered Sprint Cars. Wicked fast. I'm sure that your car is as well.

Thanks for the comments. The diff is a LSD out of a 96 RX-7 non-turbo. I used it because the stub axles match the Miata main axle bolt pattern.

The shifter is a simple push-pull with the clutch handle attached. I only use the clutch to start rolling and when I stop. I originally had a paddle shifter setup that worked pretty well but I couldn't get the HD Dewalt cordless drill to reliably down shift. The wiring and relays are still on the car, in case I can find a reliable and cheap actuator.

The steering wheel is made with an aluminum plate cut to shape, with balsa wood glued to it. Once the wood was shaped the way I wanted, I used thin CA glue to harden it and covered everything with gaffer's tape. Gaffer's tape is great stuff but it's not cheap.

today you are on top of my cool guy list!! Awesome car!!!

Great work Ric. I love seeing projects like this show up on the forum.

Is it built close enough to SCCA A-Mod to run in that class? How have you been able to test drive it so far?

Did you bend your own tubing? If so, what type of bender did you use?

What design program did you use?

I'm looking forward to seeing it with your body design.

Great build !!!!

Please tell me that you may, possibly, remotely, kind of, are thinking of, finishing the car to look like this

Looks like some great fab work.
Where do you plan to run it? Fab some fenders and run CSR?

I don't suppose you want to share that CAD file do you?

I have a Yamaha 1-liter drivetrain in need of a home.

With regards to the paddle shifter - a coworker has a Locost with a bike engine, and it's got a mechanical paddle shifter setup. Pretty nicely done, although the linkage with the engine behind you might be a bit harder to package.

What exactly makes it not AMod legal? Looks like it could be made to be BM as well.

Thanks man, I need to clean my keyboard now after drooling all over it

Need more pics.

plus isn't A-Mod no rules except for some minimum length/width?

Incredible build! I'd love to see more pictures. Any video of it running? Thanks!

In reply to BBsGarage:

I'm pretty sure there are other limitations. Displacement limits(based on weight), wing area limits at the very least.

Thanks for all the comments. More info:

The only bent tubing is the main roll bar and the front roll hoop at the dash. I had someone bend those for me.

I took the car to an autocross practice at Calif. Speedway two weeks ago to see what would fall off or break. It is quicker than stink in a straight line but the very old NT-01 tires made aggressive cornering real entertaining. I got several runs in before the cheap cast brake pedal arm cracked. I have since made a new pedal using 3/16" steel plate. I also have ordered some lightly used, super soft Hoosier tires.

I used Autocad 2000 to design the car but it is a VERY rudimentary drawing. Just enough that I could tell what I needed to make the individual tubes. One of the top priorities was to not have to bend any tubing. That's why all of the sides are flat and use 1" square tubing.

The free Wishbone suspension program was used to design the a-arm geometry. I used some formulas I found on line to calculate the pushrod/shock geometry. My objective was to be able to use the GSXR shocks without changing the springs. So far, it looks like it might work.

I believe the car is legal for A-mod. I'll find out when I take it to an SCCA autocross.

I am torn about putting a body on the car. I really, really hate the hassle and mess involved in making a fiberglass/composite body. I've thought about finding an appropriately sized formula car nose for it, fitting side pods, and adding small fenders. I've also played with the idea of just building some big wings for the front and back. Eventually, I would like to be able to take the car to some track days and the side pods and fenders open up a lot of options with who I can run with.

Photos to follow.

dean1484 wrote: Great build !!!! Please tell me that you may, possibly, remotely, kind of, are thinking of, finishing the car to look like this

This is what race cars are supposed to look like.

Now that is some kind of cool! Question: how did you seal the half shafts to the diff housing? Another question: how much does it weigh without the driver?

SCCA A Mod rules: 72" minimum wheelbase, 900 pounds with driver. http://scca.cdn.racersites.com/prod/Documents/2011%20Tech/2011%20SCCA%20Solo%20Rules.pdf see page 227.

Otherwise, must be deemed safe at tech inspection and meet noise regulations etc. Roll bar tubing minimum 1.00 OD .060 wall. I'm going to say your creation will probably pass the A Mod sniff test.

More pics.

FORMULA KLUDGE PROTOTYPE!!!!!! That's almost exactly what I had in mind---See how cool it is???

Herber, you are a living God!!!! I bow to your greatness!

In reply to Curmudgeon: I had a machine shop turn the inside of the diff to fit a shaft seal in each end. The stub shafts that insert into the diff have an oiling groove that would have extended past the seals, so I welded them up to a location back before the seal. The machine shop turned them back down to the OD of the axle.

I have no idea how much it weighs but I'm pretty sure it is legal in A-mod. The wheelbase is 78" and track is 58".

Just FYI, the steering box is a sand buggy unit. It was cheap but it weighs a lot. I used a jack-shaft to get the chain in line with the sprocket on the LSD. That way I could use stock Miata main axles and save a ton of money on custom axles..

After experiencing the fun of putting a 65" wide car on a borrowed 60" wide trailer, I'm looking for an inexpensive (cheap) box van with a 10 or 12 ft. box. If anyone has any ideas, please let me know.

If anyone would like specific pictures, let me know.

Yeow. That looks like some pretty nasty loadings with that front rocker pivot in single shear like that. Have any more pictures of that joint?

In reply to unevolved: That is a long 3/8" grade 8 bolt inserted through a 1"x2"x1/8" boxed tube. Based on my research, it should work just fine.