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Got the rear suspension mounting points installed this week. I'm fairly pleased with how they came out.

The stub from the passenger side of transmission tunnel is where the front diff mount will go; more on that later........

<N>

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

I haven't posted an update in several weeks. I was starting to feel claustrophobic having 4 cars parked in my 3-car garage so I've been focusing on dismantling the Miata. Last night I removed the final piece from the tub. - Man what a chore this has been!

My biggest dilemma was how to get rid of the tub. I didn't want the hassle of cutting it up in pieces, and I didn't want to pay for a tow truck to come haul it off, so... I decided to ring the bell that everyone on earth loves to hear "Something for nothing, come and get it!" I posted an add on Craigslist: "1994 Mazda miata body, free to a good home." I had 3 people within 48 hours wanting to come take it away. Yee-Ha. Hopefully now I can get back to the real task at hand, working on the Lotus!

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

Man how life can disrupt the flow of a perfectly good locost build!!!
Between the holidays, family vacations and multi-week travel for work I've hardly had a second to make any headway.
It's been colder than a well diggers heel, but last night I fired up the propane heater and finally got back in the garage for some much needed progress.
The front suspension mounts are tacked in place except for the lower rear driver because I ran out of 2" sq tube - yet another trip to MetalSupermarkets on the to-do list. I'm fairly pleased with how they came out. In retrospect I probably would have designed the front main chassis tubes to be in slightly different places, but this is decent workable solution.

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

The chassis still is not complete, but I just couldn't resist mounting the wilwood pedals and master cylinders I got last month. I went with 2" angle at the floor to firewall and 1" angle at the heel.
I've decided mounting mechanicals is a lot more fun than chopping and welding tubes into the chassis.
- For now I'm leaving the miata throttle pedal as-is with the cruise control lever. If I can fit in all under the hood, cruise is one luxury I'd like to have.

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

Your master cylinder reservoirs looks awfully low. Without residual pressure valves, even if you manage to get the system bled by lifting the front to bleed the rear and lifting the rear to bleed the front, With no pressure on the pedal, the compensation port will be open, allowing air bubbles in the master reservoir to migrate the calipers.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

The Master Cylinders are physically installed (ok they're each hanging by one bolt a piece because I didn't have enough hardware...), but I haven't done any plumbing yet. The residual pressure valves have not yet been installed. I have seen many many racers with pedal/master cylinder set-ups like this, and they all work quite well. I'm not worried about air bubbles and flow-back. Thanks for the concern though...

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

Got the motor mounts tacked in last weekend.
They are probably OK the way they are, but I don't want things flopping around in there so I will probably add gussets as outlined in yellow.
Clearance in front of the master cylinders isn't quite as bad as it looks from the angle of this picture. I'll be able to work around it.

Don't you just love my rubber motor mounts? They had fatigue cracked clean through when I pulled the mill from the miata. Replacements are not cheap so I'm holding them together with bailing wire until I I'm ready to do the final install. At this point that's going to be years away!

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

I also got the lower diff mount tacked in place. Here is a bottom-view of the lower mount.
I know this is the most highly stressed mount on the whole car. I've seen several diffs pull right through this mount because of the enormous loads under acceleration. I'm really hoping my approach will work!

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

Here is a side view of the rear diff mount tacked in place.
Bolts will go in from the bottom.
I will also have a mount come down from the trans tunnel stub I left sticking out. (as outlined in yellow.)

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

I know I'm going to get an ear-full on the clearance between the CV joint and my rear suspension structure, but it actually does fit. Even at full bump (and well beyond full bump) the CV, CV boot or anything else that spins stays clear of the fixed members.

I'm actually still thinking about mounting the outer diff arms from the bottom like this photo I found on the net. (Sorry I don't remember the source.) Granted it's an RX-7 diff, but the principle holds.

(http://locost.voodoobox.net ...maybe???)

<N>

_________________
In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

Finally got the diff mounted this week. I spent a lot time stewing over how to do it, then on my drive home from work one day it just came to me. "Why make it more complicated than it needs to be?" I went straight home and finished it in only an hour or two.
- I like it!

The sections are removable so I can get the diff out and there will be tubes from the 2" channels up to the shock mounting point too, ala Westfield.

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

I then test fit the axle/CV/upright with the rear fender. It actually looks like everything will be in the right spot. 5.5" ground clearance at ride height and a horizontal drive shaft. Perfect.

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

I made yet another a trip to MetalSupermarkets. - The prices are SCARY but man, it's so convenient! They'll chop it, slice it, dice it anyway you want, it's hard to resist. It's also nice for guys like me that have the solution dreamed up in their heads. You can walk in and browse through shelf after shelf of anything and everything metal. I just wander till my solution jumps off the shelf and into my hand.
I'm afraid to add up all my receipts for the steel I've purchased there. $16 here, $25 there, Brackets, angle, sheet you name it, all adds up pretty quick.
I bought the last piece of 2" square I needed for the front suspension mounts. They are finally DONE!

_________________
In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

And last but not least, I added the front triangulation braces. - Most people stick with just one long brace as the book shows. I went with a full "V" to gain a little more longitudinal rigidity. I didn't run numbers on it but my gut tells me a member that long and slender in compression would likely be subject to buckling.

Also the lower front mount actually angles inward to the LCA rear mount. That way I pick up a little more torsional rigidity as well as giving all those braking loads a place to go.

(Sorry the front upright is in the way. Not a great picture, but you get the point.)

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In God We Trust... All Others, Bring Data.

Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

I had considered that, but I was concerned it would complicate the body panels. More importantly, will you have good triangularization at the top of FU1 and FU2, above the UCA rear suspension pickups?

I haven't mocked it up yet, but I'm currently considering making an X brace in that bay. They wouldn't meet in the middle (I think), and the added tube would be inboard of the stock tube, so no bodywork issues, I think. This would seem to add a lot of rigidity to the engine bay, which seems to get a lot of attention regarding its flexibility.



I figure the LCA pickup already had 5 tubes meeting there (now 6), plus maybe some sheet. The UCA pickup is mid-tube, and the nearest cluster had 5 tubes (now 4). Not sure where I was going with that.

BTW, I'm not saying your design isn't a good one. Just spouting ideas, mostly so I can learn from people pointing out holes in my logic.


d-ave

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
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