LocostUSA.com

Well I guess it's finally time to start sharing. I purchased the donor '90 Miata two years ago, and sold the shell one year ago. Lot's of thinking and building up the "race car fund" resulting in finally starting the frame in June of this year. Check back to this post as I'll upate with the cars specs as they evolve.

'90 Miata 5-speed donor (using all of the usual items)
Frame is a combination of what I feel are the best attributes of the Haynes, Book, the collective LocostUSA forum, and ultimately what I think is best. The big difference that I'm trying to incorporate is to build the frame around the component locations instead of building a frame and then hanging everything on it; load paths from suspension pickup points and driveline components are all tied together.
Kinetic Book Nose, and Haynes Scuttle
90" Wheelbase, 22.5" Dia. Tire, 5" Ground Clearance
Rear: IRS suspension is modified stock Miata dimensions (Track Width=56.6, RC=2.5")
Front: My design with aid of Wishbone (Track Width=55.5, RC=1.725")

More to come.

Titles speak for themselves.........

Nice looking start to your build.

Any closer pics of the diff mount? It looks very clever.

Looks like a good start, JAF!

Is that a rubber tranny mount? I considered using those holes for my mount, but ended up using PPF mounts. Doesn't look you're short for space, but by using that rear mount, a fella could cut off the PPF mount area and cheat almost an inch in clearance.

Keep the pix coming,
-dave

Cheers on the vertical front bulkhead, it's a good idea - I hope you get it to work out well. Should be doable with different shape wishbones. My Formula Ford is like that.

Dhempy: Yes on the rubber mount......I have the 9.4102, came with two so I have one left over that I could sell. I like it because it keeps the trans. mount symmetrical, and makes the engine mounts do the work. http://www.energysuspension.com/universal-products/link-flange-type-bushings-universal-mounts-isolators.html

A.moore: As requested......My rear axle center line is in-line with the top of the rear bulkhead so the stock 1.6 diff. mount intersects that plane. I cut a 12ga 2x2 tube up to make the upr/lwr brackets and used all of the stock hardware. The tubes are positioned and brackets slightly angled so that I can rivet/bond a shear panel on the passenger side of the trans. tunnel. I'll continue the diagonals fwd along passenger trans. tunnel to eventually join R-Tube..........my interpretation of incorporating the PPF into the chassis.

Lookin' good. Are you going to solid mount the "ears" on the diff? I think driveline parts should be individually solid mounted or rubber mounted, but not both...but that's a gut feel opinion rather than a voice-of-experience opinion.

I'd like to see more detail of how you mounted the back of the trans. It looks pretty slick, but leaves me with an urge to peel off the blue painters' tape so I can grok in fullness.

Jack: Here's your naked trans. mount pic.....grok till your hearts content. I still need to fully weld it up, grind down the sides, and put a gusset underneath it. And yes.......the diff ears will be solidly mounted, rear suspension mounts are first though. I agree with the solid or bushing mount theory, pick one or the other. If you combine the two you are just asking the solid mounted end to do all of the work.

If you make the lower forward diff flange removable (by flipping and adding a flange on the frame to bolt to), it will be much easier to remove the diff later. Also, the space between the forward flanges won't be as critical with an adjustable lower.

Rear suspension chassis mounts and diff mount complete. Front suspension chassis mounts complete minus second upper fwd bracket so I can integrate the upper shock mount into it. Front/Rear control arms are next.

Are you sure you'll get enough droop out of those lower, rear chassis mounts for the front suspension?

-dave

Dhempy......Good eye.......preliminary measurements say it will be close, I'll find out for sure when suspension is cycled through full droop. The backup plan is to cut/splice (see black sharpie lines) in new 1" square tube just inboard of the current tube to provide clearance for the lower control arm. This is a trade off to get the side panels on the chassis to run the full length (scuttle to nose) and make for a nice clean gap with the nose, while at the same time providing a nice flat shear panel to help stiffen the chassis.

Front suspension is almost complete less upper shock mount and some gussets. Lower arms are 1"DOM w/0.5" rod ends and AN bolts, upper arms are 7/8"DOM w/0.375" rod ends and AN bolts. Track width is stock Miata (55.5"), camber is set currently at zero for simplicity, and caster is set at 7 degrees. Enjoy............

it may be just the pics, but it looks like you're going to have no droop travel up front?

The pics are deceptive, and yes droop will be limited by the aft lower control arm mount. All of the pics are shown with the suspension set with a 5" ride height. You can see I mocked everything up with a 1" spacer (square tube piece) to give me what I hope is enough clearance. As it stands right now I have 3.75" of suspension droop before the lower arm hits the chassis.
Look at above post for my contingency plan.