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Thread: GTMR Progress

  1. #1
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    GTMR Progress

    Well, since it is the off season for racing and I had some free time, I continue to work on the GTMR. I think I am going on 6 years now.

    I painted the body with filler primer, then took a long board sander to it and found all the high/low spots. Some filling with body filler for the major spots is in order, and then some more filler primer.

    I also have been able to nearly complete the jig for the uprights. This is a "YUGE" step in the building process because it really ties all the wheels/brakes/suspension together and must be done in such a way that is geometrically correct, and dynamically advantageous. I built all of this within a Bill Mitchell authored dynamic suspension design program and am now to the build stage. The jig insures that upright #1 is equal in every critical way to upright #10. I have actually two fixtures in order to build the uprights. They are all hand fitted and made 100% out of 4130 steel.

    IMG00964-20170103-1632.jpgIMG00902-20160529-1132.jpgIMG00961-20161218-1551.jpg
    Last edited by crash; 01-20-2017 at 10:50 AM.
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  2. #2
    Senior Member The Stig's Avatar
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    Wow... That's looking cool It's also a LOT of planning and thinking, and execution. Very interesting to say the least.

    Please post more pictures as you're able to.

    Mike
    The Stig

    Some say, that I only know two facts about ducks, (both being wrong); and that if I could be bothered, I could solve the "da Vinci Code" in 47 seconds...
    All I know is that I'm called "The Stig".
    GTM #0081

  3. #3
    Senior Member beeman's Avatar
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    Awesome Crash. Let's race and see who gets done first! Glad to hear an update, yours is one of the top couple builds I look forward to getting updates on (and Mike's is one too of course - but he is almost done...NOT FAIR!).
    Last edited by beeman; 01-20-2017 at 12:32 PM.
    MK3.1 2004 Mach 1 donor. ABS, PS, TC.
    GTM #304 LPE 525hp LS3
    2000 C5 Lingenfelter LS1@489hp
    1999 Corvette FRC/Z06 track car

  4. #4
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    Hi Crash,
    Looking good. I worry I may have a problem and wonder how you are addressing this. I believe you widened your rear fenders and this will allow for wider tires. On my car I have 345's on 20" 13.5 wheels but to get the wheel out to the three inch widened fenders the wheels are "deep dish" with an 8" backspacing. Can you share your plans around wheels and offsets?
    Thanks,
    Gary

  5. #5
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    Well, I am building this car from the ground up. It does use the GTM body, but not much else. I have built 6 cars this way previously and I ALWAYS start with the body and the tires I want to use. IIRC the rears I have are 360 wide on 18" rims. The fronts, again IIRC, are 320 wide on 18s. These are tires that are used on LMP1 race cars and are slicks. Just because I make the car able to fit these does not mean that I must run such a large tire, I just want to make sure I am able to run that if I need to. Wheelbase is 106 and track width is increased to 78". You will notice the large offset on the uprights, and that is due to the large endurance sized brake calipers that I am fitting the car with. If I wasn't interested in running 24 hour races, such large brakes would not be necessary and thus I could use the C5-C6 uprights. So it all really begins with the tires, then I choose a rim that will maximize the lengths of the suspension arms(the most offset to the outside of the car I can get), offset the upright the minimum I can with the brake calipers I need to run, then finally put everything up to that point into the computer and see where my suspension points need to be on the uprights for "proper" positioning for camber, caster, scrub, etc. and then check everything dynamically throughout the suspensions travel range.

    So to answer what I believe you are asking, call John at CCW for proper wheel selection as my GTMR and how I go about wheel selection is going to be totally different than your stock GTM. He knows the GTM well and will get you what you need.
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  6. #6
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    Took some more picture this weekend. These show the prototype upright being fitted to the brakes and checking for clearances of both the brakes and the CV joint. In the first couple pictures you see how I go about assembling the pieces onto the welding jig. Again, you can see the very large amount of offset that was needed for these very large brake calipers. Those top hats are also custom made.
    IMG00974-20170204-1140.jpgIMG00975-20170204-1145.jpgIMG00976-20170204-1145.jpgIMG00977-20170204-1645.jpgIMG00968-20170129-1512.jpg
    Last edited by crash; 02-06-2017 at 10:50 AM.
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  7. #7
    Senior Member beeman's Avatar
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    That is so far over my head I can't even comment on it, other than it looks exotic. If this is what you are doing with the upright, I can't imagine what else you have in store for your car!
    MK3.1 2004 Mach 1 donor. ABS, PS, TC.
    GTM #304 LPE 525hp LS3
    2000 C5 Lingenfelter LS1@489hp
    1999 Corvette FRC/Z06 track car

  8. #8
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    IMHO uprights are some of the least appreciated components on a car. They almost completely determine how well a suspension can be adjusted and set up to try and make the car go quickly. There is a TON of work involved in suspension uprights. I have been working on these for about 2 years now...on and off...while also piloting the FFR PDG GTM to a number of racing championships. Very close to production now and just need to finalize the second welding jig for the suspension and brake mounting points. The second jig will also likely be used for holding the uprights rigidly while machining the holes for those mounting points. The bottom mounts are already made, but the top ones still need to be machined.

    IMG00897-20160522-1801.jpg
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  9. #9
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    Been welding like a mad man...
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  10. #10
    Senior Member beeman's Avatar
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    Do you see a market beyond the GTM community for the uprights? Corvette or Porsche guys? Would be nice to have some sales volume with all the work you are putting into them...
    MK3.1 2004 Mach 1 donor. ABS, PS, TC.
    GTM #304 LPE 525hp LS3
    2000 C5 Lingenfelter LS1@489hp
    1999 Corvette FRC/Z06 track car

  11. #11
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    I have had a couple of people now tell me "you aren't gonna make any money with those", and "why don't you just start with a big chunk of billet and make that out of machined aluminum?".

    My answer to the first one is that I am not trying to sell these, I am trying to build the strongest, lightest, best performing upright that I can. The answer to the second question is that I don't own a CNC mill(yet) and this I can build over time, adjusting things as the situation and evolving build design of the car dictates. Repairability is also a factor.

    Right now I couldn't see selling these for less than $3500 a piece, and, frankly, I don't really have the time to build a bunch of these. They are VERY labor intensive.

    When combined with those Alcon calipers, and the forged wheels, and the NMB rod ends there is about $10k worth of hardware at each corner of the car. Just the small form factor weather proof Lemo plugs for the wheel sensors are $600.

    The cost of this car is adding up quickly.

    Hopefully I won't exceed the cost of Pandora!
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  12. #12
    Senior Member Roger Reid's Avatar
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    The amount of labor going into those uprights is staggering. Just the weld fixture looks like mega hours. Then there is the weld procedures to keep warping to a minimum. Of course all that could be cured by using titanium as a base material.
    Good job.
    Just an old man with a great hobby

  13. #13
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    I've been working on the brake caliper mounts. I know it doesn't look like much progress, but mounting the calipers is critical. This is the prototype, and once it is done, then I can go back to the weld jig and make the fixtures that will align all the rest of the uprights perfectly with what I have done here on the prototype.

    This is one of the areas where the component car concept really cuts down on time and effort required to build. By using the GM parts, none of these issues needs to be addressed, so something that is taking me months to build is a simple bolt on part when done as the original kit intended. It takes a months long job that most would not want or be able to do, and makes it into a one day job.

    IMG01007-20170430-1439.jpg
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