I've posted my build diary on the Yahoo Manta Group website but some folks have had difficulties in seeing the photos there. I'll post in parallel here and hopefully it will be easier to navigate this site.
Briefly, long go I bought an unassembled Manta Mirage kit from a local fellow with the idea of building it into a dual- purpose street/track car. The build started off in that direction but I soon realized that the compromises necessary would result in an overweight, uncompetitive track car and a totally unsuitable street machine. About that time I attended Speed Week at Bonneville for the first time and decided that this Mirage was going to be built to SCTA (Southern California Timing Association) rules. A few car shows might be the only other option.
I'll attach a couple of pictures that show the general idea and also a few details.
In August I assembled the car in its still- unfinished state and trailered it up to Bonneville to get it looked over by the SCTA tech inspector. This way I could find out if there were any problems and then have time to remedy them as the build finished. No such luck-- Speed Week was completely rained out; there was 6" of water covering the salt flats. I found a couple of inspectors who gave it a quick look but that was all. As they say "That's racing".<br><br type="_moz">
SCTA rules require a very sturdy roll cage as well as on- board fire extinguishers, parachute, race tires, etc. I added a full roll cage and after all the welding was finished I had the bare chassis sandblasted. Next was a two- part zinc chromate epoxy primer followed by a topcoat of two- part polyurethane isocyanate resin.
I still don't know if I'll really need a fan to cool the radiator but I thought that now is the time to fabricate one- just in case. I decided to use an array of six small 12V fans and this made it necessary to cut 6" holes in my aluminum shroud. I made a circular gizmo out of 5/16 aluminum plate. on one end I drilled a 3/8" hole for a pivot bolt and 3" away from that I drilled a 7/16" hole that fits my rinky-dink Harbor Freight plasma cutter. The arc distance is set by a stack of 3/8" washers. After the pivot bolt is fastened to a center hole, the torch is placed into the 7/16" hole and the arc is run around the pivot. Voila! a nice big hole is cut out.
The fan panel is almost finished; I still need to run the wires to the barrier strip. I did the usual 2- part zinc chromate primer and assembled the ribs with 1/8" Avex rivets.
I searched the internet for a pull knob that would be suitable for my battery cut-off cable, a push- pull control cable with ends threaded 10-32. No luck, so I made one out of 1/2" 6061-T6 aluminum plate. Nothing fancy- I cut it out with a hacksaw, dressed it up on a belt sander and then tapped it 10-32. I had a can of self-etching primer so I tried that after soaking it in a phosphoric acid solution. The topcoat of red should make it visible to the emergency crew. I designed it so that it could be pulled by a person wearing gloves.
To enclose the cockpit and add stiffness and strength to the tube chassis, I riveted on aluminum panels of 0.063" 7075-T6 with A256 and Monel 5/32" dia. Cherry and Huck rivets. These are very high strength fasteners that require a hydraulic rivet gun; pulling them with a hand tool is out of the question. Cleco skin fasteners were used as temporary clamps to fasten the panels to the chassis tubes while drilling holes and then pulling the rivets. The two- part zinc chromate epoxy primer was used on all the aluminum panels.
I ran into town to run a few errands, one being to take advantage of a heat gun on sale at HF for $8.99. My old Ideal heat gun finally burned out the heating element. It was a POS and not repairable so I junked it and, most conveniently, the HF sale came up at the right time for me. Out of desperation yesterday I tried my wife's hair dryer on the shrink tubing but it would barely affect it.
I finished wiring all the fans on my panel and they all work.
I'm using a Porsche G50-01 transaxle, inverted so that the car goes forward. The adapter, flywheel, and clutch are Kennedy Engineered Products. The shifter is a rod type with Thompson ball- bushings and Apex u-joints.
Rear uprights are Porsche 996 and the rear calipers and rotors are from the front of a Porsche 928 S4. I had the rear hubs re-drilled to convert the original 130mm bolt circle metric threaded holes to a 5 stud on a 5" bolt circle ("5 on 5") pattern so that I could use Bassett circle track racing wheels. The new studs are coarse thread 5/8" -- a standard in circle track racing but using a different taper lug nut.
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