build diary

May 3, 2004:
Busy weekend!
I spent some time finishing the wiring in the rear of the car and working on routing. It's all looking nice and tidy although I still have to work out the connectors for the taillights. This will be easier to do when the tails are mounted - I learned the hard way on my Land Rover rewire that just adding in extra wire "because I might need it" makes for a very messy harness.

I've also started on the instruments. I'm not completely happy with how they look right now, but there's always the chance to change them later. I really don't want the car to look as if I simply stuck a factory gauge panel into the dash, so I'm taking pains to hide the "Miataness" of the donor panel. It meant a lot of grinding and careful shaping to get as far as I did. If I paint the dash black it'll look more integrated but I was rather hoping to stick with body colour. We'll see.

Typically the way you build a car like this is to install the engine and transmission very early on. Because I'm still waiting for my engine, I'm having to work in a bit of an unusual order. The logic of when to install what body panel is a little complex, but the good thing is that I'm working with a mind towards how the engine will be installed and removed easily.
entry 262

The wiring at the rear is coming together.
I'd rather not have the axle chew into this, so I'm being careful to keep it all well tied down.
entry 263
Not a bad measurement - the steering column hole has been drilled in the scuttle.
entry 264
Working out the placement of the instruments.
They're not centered on the dash because the tach would be covered by the wheel and the offset transmission tunnel would look a little strange.
entry 265
I'm taking care of Turbodog for the week.
He seemed to think that I had better things to do than cutting holes in fibreglass.
entry 266
Holes are cut for the instruments.
I had to enlarge the holes freehand and I screwed up on the speedometer. Nuts. I'll try to patch that up with some bondo.
entry 267
The modified instrument cluster.
I even wound the odometer back to 0.
entry 268
This is interesting.
The Japanese "Miata" (the Eunos Roadster) comes with a 180 kmh speed limiter. It can easily be disabled by removing a screw. Looks like the US instrument cluster is the same part. What do you think would happen if I put a screw in there on a stock car?
entry 269
A closeup of the instruments.
I was thinking about mounting the chrome ring to the dash itself - that might have looked better, but it would have been difficult to add glass later. The mounting bolt is just a temporary one as I will find something that looks a little better.
entry 270
Hmm, it's starting to look like something.
entry 271

May 4, 2004:
Nothing exciting, just a little more time spent reworking the holes for the gauges.
They've got a beveled edge now so the gauges look like they belong. I need is some plastic to cover them and I'll move on.

CMC did another 2-day build at the Walter Mitty vintage event and even managed to drive the car on the autox course as well as partway home. Impressive. A conversation with CMC did reveal some new information, though. If the front of the diff is not hard mounted to the frame, it'll cause problems with a loss of drive as the diff moves around. I can't think of how this works and Steve didn't really seem to know either. The only theory that I and my coworkers have come up with is that the driveshaft is pulling free of the splines in the transmission but that doesn't seem plausible. A diff will work at any angle. He described a clicking when trying to go uphill. Strange....The existing mounting technique works for a while but eventually loosens. I may try using a locking nut on that long bolt on the diff if I can't easily work out a mount on the frame itself - after all, if it works when it's first put together, it should continue to work. But the new frames are being shipped with a hard mount for the nose of the diff instead of the rubber one I have now. Time for some mulling-over in the garage.

In further news, the remaining bits and pieces of my setup should be shipping tomorrow. I'm moving towards the point where I can paint the body panels - that will be exciting!
entry 272

After a bit of reworking of the holes, the instruments look more integrated.
It's hard to photograph this!
entry 273

May 5, 2004:
I've polled the Grassroots Motorsports forum about the differential mounting.
One good suggestion was to build a PPF out of tube - or at least a skeletal version of one. This isn't going to work without changing the shape of the transmission tunnel, however. The real question is whether it makes any significant difference to have the diff mounted to the frame - and thus put the torque loads through it - or have a PPF substitute. The former is obviously easier. Steve has informed me that he'll be sending the new bracket to me to weld into place. I guess it's time to wire the garage for 220v!

There is 4" of splined shaft at the end of the driveshaft so I doubt the CMC-built cars are pulling the shaft free. Puzzling.
entry 274

For those who are helping me work out the various questions about bracing the diff - here is the rear mount for the transmission.
The vertical tube on the transmission tunnel is directly behind it.
entry 275
The current diff mounting.
entry 276

May 6, 2004:
Lots of differential design going on!
This is fun stuff. Lester Seal reports that he built an E Production Miata that didn't have a PPF. His solution was to run a short piece of tube forward from the top of the diff and anchor that. It was triangulated with a tube coming up from the bottom of the diff. This reportedly worked quite well, and an upside-down version could certainly be adapted to the Seven. It's also something that could be retrofitted so I'm going to try simply putting in a hard mount in place of the rubber bushings I have at the moment. Combined with a proper locking nut that should prevent any movement. It's also very light (I have some aluminum spacers to replace the rubber) and easy. I figure I'd rather put the existing mount into compression than try to hook something up to the bottom of the frame and have it in tension.

This is interesting. They're basically intended to bypass the bushings in the diff mounting arms to give a more solid mount. A shiny version of my Shoe Goo and the plastic inserts I'm using now. I can't see how it benefits a Miata but I was actually considering exactly the same thing for the Seven yesterday before these were brought to my attention!

I've also been looking at the driveshaft angle. I've got the nose of the diff too high at the moment - it really should be parallel with the output shaft. It's a good thing I was looking at the diff and caught that.
entry 277

May 7, 2004:
I didn't have a chance to do any measuring of driveline angles last night.
However, I did order my brake and clutch pedals and hydraulics as I figured it would be easiest to run the lines before the engine goes in. I'm pretty excited about this!
entry 278

May 10, 2004:
Lots of work this weekend.
First, driveline angles. I suspect all of CMC's engineering has been done with the smaller 1.6 diff, but even then a mounting point that is about 1" higher would make a big difference. The bottom of the bigger 1.8 differential hits the frame before the diff gets level, and the longer nose of the 1.8 also means the driveshaft is shorter. Thus the driveline angles in my car are now are as good as they can be but still not ideal. The driveshaft angle is a touch under 4 degrees and the diff and transmission output shaft are about 3 degrees out of alignment. I'll see how this works - if there are vibration problems I'll remount the diff higher up in the frame.

I've talked to a couple of engineers about the rear diff mounting as well. They are unanimous in condemming the existing mount for the nose of the diff. I'll have to make a stumpy version of a PPF to fit inside the frame. This could be a bit of a challenge, but it should be worth it in the long run. Lester Seal has the correct idea with his plan to use the PPF.

In other news, I've cut out the bottom of the dash for more legroom. The dash is looking good although my first attempt at some glass to cover the gauges was pretty hideous. I also riveted the rear bulkhead body panel into place - I've been looking forward to doing that for some time! It's the best fitting body panel so far. It needs one small bend at the bottom and two notches needed to be cut out of it, but all the angles appear to be square and it looks good in place.
entry 279

There's a limit to how low I can drop the big 1.8 diff.
You're looking at the bottom of the diff meeting the frame. I'd shaved this down a little since the photo was taken but there's only so much meat that can be removed.
entry 280
In order to level out the differential as much as possible, I shaved down the steel inserts inside the diff bushings.
It helped.
entry 281
A great way to measure the output angle of the transmission.
entry 282
The dash has been reshaped for leg clearance.
entry 283
I'll call this panel the rear bulkhead for lack of a better name.
It's the best fitting panel of the lot so far. I needed to cut two notches to allow access to the front bolts for the lower control arms, otherwise adjusting the alignment would be difficult.
entry 284
<< | show individual entries | >>