Homebuilt Mid-Engine Sports Racer

Neil

Supporter
I have been building this car over a period of many years. With the exception of its fiberglass body, all the fabrication was done by me- including the chassis, suspension, and engine. I chose the McLaren replica body that was made by Manta Cars in Santa Ana, California for their Mirage kit car because I knew that it had good aerodynamics but it was necessary to modify it significantly for its intended purpose- to run on the salt flats of Bonneville, Utah.

The engine is an aluminum block Donovan, 383 cubic inches, mated to an inverted Porsche G50-01 with a KEP adapter. The chassis is a steel tube space frame with stressed aluminum panels riveted on. It has an SCTA roll cage of round heavy gauge tubing with a titanium shear plate. The front suspension is based on Ford steel uprights while the rear is a 5-link with Porsche 996 aluminum uprights. I designed the suspension geometry using Suspension Analyzer v2.4. Dry weight is about 1985 lbs (900kg).

Here is a clip of it running in my shop.
The exhaust sound pressure modulates the cell phone camera lens focal length!

Regards, Neil Tucson, AZ
 
Great build you have there Neil, I watched the more detailed build diary video you have up in addition to this one , very nice work. -Vinny
 

Neil

Supporter
Thanks, Vinny.

I built a Sabel back in the early '70s- Tube chassis, fiberglass body by John Sabel, 140 HP Corvair flat six driving a Porsche transaxle out of a 914. Lightweight (about 950 lbs-- ~431 kg) and fun but I vowed never again to build a chassis with round tubing. fitting the curvature of the ends was a nightmare. In those days the tools to make those ends were only a hacksaw and a file.

I wish I had kept a build diary of that car. I sold it to Dick Morel in Maryland who is in the process of restoring it.

Regards, Neil Tucson, AZ
 

Cliff Beer

Supporter
Fantastic build there Neil. Looks amazing. You have quite a car. Being a scratch build, I can't imagine how much blood, sweat and tears the build has taken to date. Keep up the good work! You must be getting excited to be nearing the end of the build and have a running and driving car.

Really have a lot of admiration and respect for guys who do a great job of projects like this first hand with their own innovation, skill, and hard work - no check book mechanics.
 

Neil

Supporter
Thanks, Cliff. It has been an interesting project. My "machine tools" are a drill press, a small HF plasma cutter and a cabinet full of hand tools. I did have a few things done by outside shops- the two hoops in my roll cage were bent by a local off-road shop and I had my rear Porsche 996 hubs re-machined from 130 mm to a 5" bolt circle with 5/8" studs so that I could use circle track racing wheels. I will get the car sorted out during World of Speed at Bonneville next month.

One thing I might recommend to anyone building a car is to find a local EAA chapter (Experimental Aircraft Association) in your area and join. You will find people with a wealth of knowledge about construction techniques. Alternatively, much of this can be found on-line. Aircraft and race cars have a lot in common! One of the most useful things I ever did years ago was to enroll in an Airframe and Powerplant Mechanics course at our Tucson community college.

Regards, Neil Tucson, AZ
 
the detail of brackets ,nut plates, rivet patterns....all so time consuming.
looks like General Dynamics built the thing.

how did it go at speed weeks? are you, did you go back this year?

cool indeed.
 

Neil

Supporter
Thank you, Mesa. It has been a fun project and I have learned a lot while building it.
At last year's Speed Week I had some problems in tech inspection (scrutineering, as John Horsman calls it), they wanted me to extend my firewall out to the edges of the bodywork, make it easier to get in and bail out quicker, etc. When I started this project I did not foresee the SFI-20 firesuit & HANS requirement. Plus, as many of you know already, the latest approved helmets are significantly larger than the previous generation. I've made those changes and I am now preparing to go to the "World of Speed" event at Bonneville in September. I missed Speed Week this year because of a conflict with a granddaughter's wedding.
Speaking of General Dynamics: :cool:
 

Attachments

Neil

Supporter
Found this, Very cool build.

How did you like the audio soundtrack, Howard? I and two of my GI friends attended the ADAC 1000 kM race at the Nurburgring in 1963. At the time I had a Butoba portable tape recorder with me at the South Curve. It was a tube-type (valves?) battery-powered unit with a spring-wound drive motor. Every twenty minutes or so I had to wind up the spring with a folding handle on the back. Technology has made a few changes since then! The announcers spoke in German and then in English. It is easy to distinguish the different sounds of the Ferraris and the Porsches.
 

Howard Jones

Supporter
I had guessed that it was recorded at a German GP. Again a very cool idea! Good luck at speedweek. What speed are you expecting?
 

Neil

Supporter
Thanks, Howard. The ADAC 1000 kM race is a sports car race; if you listen closely, the announcer refers to Lola # 115 several times. It was the Lola Mk 6 GT, a forerunner of the Ford GT40.

I missed Speed Week but I'll be at World of Speed in September. Since it will be my car's first outing, I just want to get things sorted out before a full-power run. The car is geared for 209 mph if a 4% tire expansion is factored in. Considering that a Porsche 917 could achieve over 220 mph down the Mulsanne Straight with similar Cd, frontal area, and horsepower, 209 does not sound too far off- considering the difference between a salt and asphalt surface.
 

Neil

Supporter
Last year I was in a hurry to paint my rear spoiler but I had run out of the usual zinc chromate (or zinc phosphate) primer that I usually use on aluminum parts. It isn't as good as the two-part zinc chromate that I used on my aluminum panels that I riveted to my steel tube chassis but it's a decent primer that is quick and easy. I did have a can of some sort of gray primer on hand so I used that and then topcoated it black.

This year the paint was blistering off in patches so I rubbed the loose patches with a Scotchbrite pad. Large areas of paint came loose so I simply scraped off the paint with a low-angle razor blade to get it down to the bare aluminum. Obviously that primer had very poor adhesion so I threw out the remainder of the stuff!

I scrubbed the aluminum with Scotchbrite, wiped it clean, and wiped the surface with phosphoric acid. After rinsing the surface and drying it, I re-primed the aluminum with a green zinc phosphate primer. Tomorrow I will again topcoat it black.

Moral of the story-- don't get in a hurry and take shortcuts. :(
 

Attachments

Neil

Supporter
Two days ago I was checking to see why my tach was not working and found that my battery was going open-circuit under load. Click the starter button and everything went to zero volts. Off to Costco to buy a new 24F battery. In accordance with the SCTA rule book my battery is in an enclosed box (since it is mounted in the cockpit) and I put it far forward in the right side foot well for weight balance. If I ever build another car I'll pay more attention to accessibility... :confused: Anyway, a new battery in now installed and the electrical system is now working normally- except the tach. I think it's NFG. :mad: I ordered a new one but we'll see if it arrives in time. Otherwise, it's calculator time to relate RPM in gear to GPS speed.

As long as I was working on my electrical system, I made up a matching cable for the auxiliary power connector that I had already mounted in place. This way I can plug in the connector and connect the jumper cable to an external battery for starting, charging the on-board battery, etc. The military current rating for this connector is 750A so it can easily handle the current of starter.

Regards, Neil Tucson, AZ
 

Attachments

Neil

Supporter
Rod;

My front suspension is based on a Ford forged steel upright that I bought from Shell Valley. They used it in their Cobra kits. The a-arms are swaged steel tubes with outboard ball joints from Speedway Motors and rod-end bearings inboard. My steering rack is from Wilwood, a Mustang II clone (I think).
 

Randy V

Admin
Lifetime Supporter
Would like toknow more about those fans and if they’ve ever been used to cool a radiator yet! Very interesting!
 

Rick Merz

Lifetime Supporter
The fans stood out to me as well. I like the different approach just wondering about the total weight, cfm and current draw. I have two 12" Spal fans that pull 1640 CFM each at around 15amps so 3280 cfm at 30 amps with a total weight of 10.5lbs (both fans) not counting the fiberglass shroud. This is the third car that I have used these fans on and the first two never had issues with cooling even with the AC on in 95° stop and go traffic. I have yet to drive my current GT40 but I do not think there will be a cooling issue.
 
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