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Thread: GTM roll cage modifications and race car build log

  1. #1
    Member kabacj's Avatar
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    GTM roll cage modifications and race car build log

    In an attempt prepare the GTM for top speed runs, track duty, and hopefully even SCCA and NASA approval for racing I have made a few modifications to the GTM frame.

    The job started with bending and welding in roof bars that cross over the passenger compartment and follow the curve of the fiberglass.


    I

    these bars allow for the duct that channels air into the engine compartment but maintain the maximum head room possible under the stock bodywork.

    Next step was to cut out the 1 inch square tubing that supports the rear hoop and beef it up with 1.5 .095 wall DOM tubing.

    After a few versions I was able to get the tubes to just kiss in the center but still place the down tubes very near the stock 1 inch square tubing location. In order to keep them perfectly vertical and aligned, I under bent them by a few degrees and then pulled them into place with ratchet straps.



    Next I welded everything in. Boy it would be nice to have a rotisserie for this job. I was laying on my back feeding rod working the foot pedal and straining to see what I was doing on a few of the welds, but it all worked out.



    This is what I have so far.



    With the help of JCHracer we might soon have a plan that folks can follow in order to modify the GTM for NASA and SCCA racing, or just to beef up the frame for full on track duty.

    Still lots of structure to add, but its a start.

    John
    Last edited by kabacj; 04-28-2023 at 03:54 PM.
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    LCD Gauges's Avatar
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    Pretty good welds for being on your back, and half blind. Wish I had that sort of skill with all of my senses present!

    Will the rear glass still be in place, or do you have a modification for that section?
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    Member kabacj's Avatar
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    Yes the rear glass will be kept. Unfortunately in order to fit the roof bars and my air intake I ended up almost cutting through the upper section rear bulkhead. I cut and welded on a strip of aluminum to allow for more clearance.


    I might need to trim the section around the roof tubes just a bit more.



    Of course now I need to cut the bottom side of the oval opening for the rear glass since I added that half inch strip on the top half. I will fit the window as the last step after everything else works.

    I am trying to retain all the aspects of a stock GTM when I make modifications. Only builders will be able to tell what I added and what was built by factory five. That's my goal anyway. We will see how it comes out.

    John
    Last edited by kabacj; 12-27-2012 at 10:14 AM.
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    Tech Support, FFR Brian Z's Avatar
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    Wow! Nice job with the mods! The tubing is in just the right spots and the welds look great!
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    What a pain in the a**, came out real nice. You have put alot of work into that. Sure does look good.

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    Senior Member Joe Mush's Avatar
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    That is some great looking fab work

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    Quote Originally Posted by kabacj View Post
    I am trying to retain all the aspects of a stock GTM when I make modifications. Only builders will be able to tell what I added and what was built by factory five. That's my goal anyway. We will see how it comes out.

    John
    Me too.
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    Member kabacj's Avatar
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    Thanks for the compliments guys.

    I still have a ways to go on the additional structure.

    Attached is an example of how I want to lay out the bars. You can see this was an earlier version of the left and right uprights. They did not touch in the center like I planned so I binned them and started over. I also changed the location of the radius. I was so excited to use my bender, I did not want to make a template. As they say haste makes waste... I can cut them apart for the other elements of the cage so only time was wasted. Oh well live and learn.




    If everything goes as planned this weekend ill install the bars as shown in blue tape just in time for the wiring to begin and maybe another tweak on the gas tank. If I am REALLY lucky ill have the car in go kart condition for the open house.


    John
    Last edited by kabacj; 04-28-2023 at 03:11 PM.
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    Senior Member Kempo's Avatar
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    Impresive work John. I really like the quality of your welds. You have talent.
    Last edited by Kempo; 05-16-2012 at 08:21 PM.
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    Does anyone have information on installing an electronic LS3 Gas Pedal to the GTM?
    Is there a bracket or information available or is it just "Do the best you can to fit it on the pedal box?
    Thanks for any feedback.

    Radkat

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    Senior Member Kempo's Avatar
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    Quote Originally Posted by Radkat View Post
    Does anyone have information on installing an electronic LS3 Gas Pedal to the GTM?
    Is there a bracket or information available or is it just "Do the best you can to fit it on the pedal box?
    Thanks for any feedback.

    Radkat
    I'm using the LS3 on mine. You need to install two riv-nuts in the fire wall and use the provided template. Here is a link to what I had to do.

    redirecting to that link in order to not hijack John's cage thread.

    http://thefactoryfiveforum.com/showt...ll=1#post30822
    Last edited by Kempo; 05-16-2012 at 11:32 PM.
    GenII GTM #354
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    Member kabacj's Avatar
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    Quote Originally Posted by Kempo View Post
    Impresive work John. I really like the quality of your welds.
    Thanks Hugo.

    One thing i did learn about the stock frame. The stock factory five welds are SOOOO much thicker and stronger then necessary. Thats a good thing.

    When I cut off the 1 inch square tubing I had a whole lotta grinding to do in order to remove the stout welds that factory five puts on each and every attachment point.

    We surely dont need to worry about cold welds or poor penetration on the stock frame. Each Factory five weld had a 1/4 inch thick bead with perfect penetration every time.

    The factory five weld quality is one thing you can only see when you cut the car apart. It sure made this job harder, however it made me feel good about the quality of the welds I did not cut apart.

    John
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    Smile LS3 Erod Gas Pedal

    Thanks Kempo for the information.
    It looks like the mounting bracket and gas pedal for the LS3 Erod is different.
    I appreciate the quick response and information.
    Radkat



    Quote Originally Posted by Kempo View Post
    I'm using the LS3 on mine. You need to install two riv-nuts in the fire wall and use the provided template. Here is a link to what I had to do.

    redirecting to that link in order to not hijack John's cage thread.

    http://thefactoryfiveforum.com/showt...ll=1#post30822

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    Senior Member mikespms's Avatar
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    Hi John,
    Outstanding job on your mods.Are you going to make any mods to the front of the frame or the foot box area?I noticed the A/C hose,are you going to register your car for street use or is it going to be a track car? And are you going to be able to use the close out panels behind the seats and center engine cover? I am impressed with your bends using that harbor freight bender
    Keep up the good work. Mike

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    Member kabacj's Avatar
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    Quote Originally Posted by mikespms View Post
    Hi John,
    Outstanding job on your mods.Are you going to make any mods to the front of the frame or the foot box area?I noticed the A/C hose,are you going to register your car for street use or is it going to be a track car? And are you going to be able to use the close out panels behind the seats and center engine cover? I am impressed with your bends using that harbor freight bender
    Keep up the good work. Mike

    Hi Mike, yes I modified the front of the car and the foot box too. I need to upload a few of those pictures for you.

    The footbox mods were done to prevent a very hard side impact from intruding on the foot box. The mods also prevent the tire from swinging back pivoting on the A arms *into the foot box after hitting something very solid at very high speed. The foot box mods provide a six point cage required for racing.

    Yep this will be a fully registered street car with heat and AC. Any comfort feature added to the cabin will be installed in a manner that it can be easily removed. Except the AC of course. I am going to have plenty of HP so I am not worried about parasitic losses from the AC compressor.

    My dream car is a street car that can go out on the track and compete with pure race cars. A registered car will be nice to just cruise around slowly on a nice sunny day on the street and leave the aggressive driving for the track.

    Of course im going to compromise a bit to make it more livable with heat and AC, however, take any production car and make it a street registered race car and there are a ton of compromises that the factory made that I can't change. That was my logic. If I am really lucky I will be able to go out on the track with plates on and compete at the same level as high dollar race cars. Again that's the dream.

    All of the close out panels and engine cover can still be used just like the stocker. I will need to trim the aluminum and add tabs on the round tube for the left and right lower aluminum panels behind the seats but that's no big deal.

    The roof bars were bent with the harbor freight bender. The cage bends under the hoop were done with a JDsquared bender. the JDsquared is just a wonderful tool. Easy to use, super high quality, American made to last a lifetime. Expensive.. but you get what you pay for.


    John
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    looks good john. getting this done will help out the guys who want to race, knowing what has already been accepted. great work.

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    Member kabacj's Avatar
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    Quote Originally Posted by mikespms View Post
    Are you going to make any mods to the front of the frame or the foot box area?
    Hi Mike,

    Here are the mods for the foot box area

    This painted bar that passes through the panel intersects with the square tube mid way down and lands on a perch I made the outside edge of the foot box floor.



    These supports keep cage elements that surround the windshield from twisting . They clear the stock dash without trimming.



    I made good progress on the cage mods under the rear hoop. As usual I made it really hard on myself with very complex tubing intersections. Two more solid days and the frame should be compete… unless I think of something else to change.

    John
    Last edited by kabacj; 12-27-2012 at 10:19 AM.
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    Senior Member Kalstar's Avatar
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    Quote Originally Posted by kabacj View Post
    Hi Mike,

    Here are the mods for the foot box area

    This painted bar that passes through the panel intersects with the square tube mid way down and lands on a perch I made the outside edge of the foot box floor.


    These supports keep cage elements that surround the windshield from twisting . They clear the stock dash without trimming.


    I made good progress on the cage mods under the rear hoop. As usual I made it really hard on myself with very complex tubing intersections. Two more solid days and the frame should be compete… unless I think of something else to change.

    John

    John, Wow, I mean WOW! You are a craftsman!

    Question, any guess on how much additional weight added?

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    Member kabacj's Avatar
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    Hey Jim.

    Thanks for the compliment.

    The tubing weighs 1.426 lbs per foot

    I have not been keeping close track of the total length of tubing used so far ,
    But I figure 25 or 30 lbs. added when I am done.

    Also remember I took some structure out.

    I got a light weight racing battery so I'm back to even. Ha just kidding.


    John
    Last edited by kabacj; 05-21-2012 at 04:17 PM.
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    Senior Member mikespms's Avatar
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    Quote Originally Posted by kabacj View Post
    Thanks for the compliments guys.

    I still have a ways to go on the additional structure.

    Attached is an example of how I want to lay out the bars. You can see this was an earlier version of the left and right uprights. They did not touch in the center like I planned so I binned them and started over. I also changed the location of the radius. I was so excited to use my bender, I did not want to make a template. As they say haste makes waste... I can cut them apart for the other elements of the cage so only time was wasted. Oh well live and learn.




    If everything goes as planned this weekend ill install the bars as shown in blue tape just in time for the wiring to begin and maybe another tweak on the gas tank. If I am REALLY lucky ill have the car in go kart condition for the open house.


    John
    Hi John,
    I like that foot box mod. I think it adds the extra strength needed in that area, for added safety. I already closed up that area in my car but if I build another one, ill do something similar.

    Looking at the blue tape going across the center, I think it will interfere with the front of the engine did you take a reference measurement form your motor mounts foward. In my car the top of the engine is about a 1/2 inch from the bottom of the rear window frame and water pump and top of the idler pulley is foward of the window bulkhead.

    Mike

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    Member kabacj's Avatar
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    Quote Originally Posted by mikespms View Post
    Hi John,

    Looking at the blue tape going across the center, I think it will interfere with the front of the engine did you take a reference measurement form your motor mounts forward. In my car the top of the engine is about a 1/2 inch from the bottom of the rear window frame and water pump and top of the idler pulley is forward of the window bulkhead.

    Mike
    Hi Mike,

    Yep you are right the cross bar is pretty close to the idler pulley. Since the photo, I actually had a forum member with an installed LS3 verify the distance from the top of the pulley which is the highest point on the motor to the bottom of the roll bar hoop. He measured 8 1/4 from the bottom of the roll bar hoop to the top of the idler pulley.

    My bar is 7.5 inches from the bottom of the hoop to the bottom of the cross bar. Yes its very close. I figure 3/4 inch is miles of clearance.

    I have also installed the window bulkhead to make sure that the cross bar is reasonably in line with the bend in the bulkhead that allows for the water pump and idler pulley.

    I may drop in the motor before I do my final welds .... or just roll the dice and hope for the best. Whats the worst thing that can happen? ill just lower the motor, trans axle, and install a dry sump system HA! that's in the plan anyway, just not before I get the car running down the road.

    Thanks for the heads up however. I must admit I am a bit concerned about welding it all up without my motor in place to verify clearance. I am famous for attempting to get too tight tolerances. Lets hope this one I get lucky or my motor shows up soon.


    Thanks again for pointing it out.

    Here is a shot of what I have so far with the rear cage. This is still under construction and the two left tubes still need a bit of work to fit properly, but the cross bar fits well and is at the height I plan to weld it.

    You can see that my plan modified a bit from the tape version to the steel version.




    John
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    John,

    I think it would be helpful to others to name what sanctioning body this was approved by and in what region so that others can referrence this thread when building, as well as "discussing" what they have built with other tech inspectors. Just part of the documentation process, and could be very helpful to many of us.
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    Member kabacj's Avatar
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    Quote Originally Posted by crash View Post
    John,

    I think it would be helpful to others to name what sanctioning body this was approved by and in what region so that others can referrence this thread when building, as well as "discussing" what they have built with other tech inspectors. Just part of the documentation process, and could be very helpful to many of us.
    Yep, totally agree. I will share what I have learned as soon as I have a logbook in hand from each organization. I am still working through the approval process. The goal is to satisfy both NASA north east, SCCA new york, and the Loring timing association with this cage.

    I know that the PDG team have blazed a trail in this regard with the only GTM that I am aware of that is SCCA and NASA approved.

    Ill update both this thread and the other forum with all of the dimensions for folks to reference in the future.

    John
    Last edited by kabacj; 05-22-2012 at 07:20 PM.
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    Senior Member mikespms's Avatar
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    003.JPG

    A few pictures that may help you to determine the position of the center tube. there is about a 1/2 inch at the closes point between the top of the intake and the back of the window bulkhead. In the front there is about 2 inches between the back of the idler and the intake and block. There is room but is going to be a very tight fit. And you need to be able to lift and tilt the engine back for the motor monts studs to go in or out.
    Attached Images Attached Images

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    Member kabacj's Avatar
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    Quote Originally Posted by mikespms View Post
    003.JPG

    A few pictures that may help you to determine the position of the center tube. there is about a 1/2 inch at the closes point between the top of the intake and the back of the window bulkhead. In the front there is about 2 inches between the back of the idler and the intake and block. There is room but is going to be a very tight fit. And you need to be able to lift and tilt the engine back for the motor monts studs to go in or out.
    Thanks for the pictures Mike very helpful. I also was worried about tilting the motor in to clear the motor mount studs. I figured worst case I install the mounts then drop the motor on top then bolt the motor to the mounts. Regardless your point is well taken. Worst worst case I make new mounts that bolt to the frame from the bottom instead of using a stud. I could safety wire the bolt so it would never vibrate and fall out. Or remove the parts that interfere before indrop the motor in.

    Regarding the intake clearance. I hope I might gain a little there...maybe. I don't know if the stock front intake runner is farther toward the front of the motor then the intake port in the head.

    Looks like it is from pictures of the intake viewing from the bottom.

    The hillbornes might gain me a little there.



    I think the front most intake runner is at least one half inch more forward then the intake port on the stock manifold. That said I do want the option of running a common plenum intake.

    Maybe I'll just tack the cage until i get the motor.

    Thanks for the help.
    John
    Last edited by kabacj; 05-23-2012 at 06:19 AM.
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    Some good progress this weekend.

    I was able to get lots of tubing fitted and most of it welded in.

    The first thing was to finish the gussets in the windshield opening.

    The lower gussets are under the dash pad and in keeping with my stealth race car theme I moved the upper gussets as far up as possible. When I had the gussets lower I found that they start to get near your line of sight out the front. Sure the lower position is the stiffest for a pure track car, but I wanted braces that were less pronounced.

    As you can see below these braces are just touching the vertex of the windshield frame allowing me to weld all the way around the tubing.



    Next was fitting the rear structure.

    Here are three shots of the cage pre welding. From the pics in my album you can see I changed things slightly from the masking tape mock up, but its pretty close.







    A close up of the joints . I got these nice tools to cut fish mouths in tubing which is great except when you are attempting to land one tube on the radius of another. Yep all hand work. As usual much more time consuming then I expected, but it worked out in the end.



    Just need to figure out the door bars and I'm done.

    John
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    Super Moderator vnmsss's Avatar
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    Nice work, John! It's great to see another competition cage build in progress....We'll be out here following your thread and cheering you on!

    Karen
    PS...What top speed/bracket will you be competing?
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    Quote Originally Posted by vnmsss View Post
    Nice work, John! It's great to see another competition cage build in progress....We'll be out here following your thread and cheering you on!

    Karen
    PS...What top speed/bracket will you be competing?
    Hey Karen. Great to hear from you!

    The target bracket is 200+

    I'll need to my qualify my way up to that level but that's the goal.

    John
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    Trick Tool Maker, Super Moderator Hankl's Avatar
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    Hey John,

    Karen was at Loring also!! LOL

    Hank
    “If you didn’t have enough time to do it right the first time. How come you always have time to go back and do it again?” FFR1000186CP

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    Horsepower is how fast you hit the wall and torque is how far you take the wall with you.

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    John, superior workmanship, very impressive!

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    Thanks for all of the encouragement guys.

    This weekend I finished welding the cage with exception to the cross bar that goes over the motor. I think it will be fine where it is, but better be safe then sorry. Ill trial fit the motor then weld it in.

    I also fit the two aluminum panels back as they were prior to adding the round cage reinforcement.



    I was shocked but both left and right panels fit perfectly using the holes I drilled before cutting the frame apart.

    I was very careful to try to minimize the warping that is un avoidable when you cut things apart and re weld them. I was very lucky to get both sides back exactly the way they were prior to welding. All of my 1/8 inch mounting holes drilled in the aluminum still fit into the holes in the re welded square tube! That was a relief because drilling those 1/8 inch holes is not fun.

    The rear most edge of each panel was riveted into the 1 inch square tubing that I cut out so I simply trimmed the panel and added a tab near the bottom of the round tube.



    The panel is very sturdy.

    NASA rules state that the roll bar behind the driver should have rear supports with a 30 degree included angle.

    Of course they also say that you can use back stays that land on the shock towers like the stock GTM has IF you follow all of the other cage requirements.

    Here is a picture of how a back stay would look at 35 degrees. It lands on the only strong point of the frame in the proper orientation to the roll bar.



    In order to make a landing area for the tube I would need to add a plate and some gussets to tie into the 1 inch square tube.

    I think I am going to try make a case that the stock GTM back stays are sufficient. I personally don't feel that the 30 degree back stays are any more safe on the GTM, actually probably less strong as attachment to the frame is stiffer near the shock towers. But rules are rules..

    From what I read SCCA seem to be OK with the stock GTM back stays.

    I am working on the door bar design now. I am not sure if you guys noticed the height and size of the McLaren door sills. They are HUGE. I think I can meet the safety requirements but still cover the bars in the GTM for street duty. Ill post my mock up for review.


    John
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    The NASA kicker rules are absolutely ridiculous! Ask me how I know!?!

    No way a Grand Am DP would meet the requirement.

    Good luck to you.

    Please let us know how you come out on this detail.
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  33. #33
    Junior Member TheChief's Avatar
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    That looks really great! You are an insperation to us all.

  34. #34
    Member kabacj's Avatar
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    A quick note on the tools I used to bend up the cage.

    I went with a JD squared bender. Everybody that gets one says they are great and I agree. Its just a great tool. Very well made.





    I could not spend 180 bucks on the base. (after shipping costs) so I welded up some scrap to make a pretty good base.



    I used an old brake drum from my old F150, some scrap 1/4 inch steel plate, some scraps from a lally column I cut apart for some other project a little hammer tone paint and I had a base for free.

    I LOVE making stuff from crap that I have saved over the years. I had those tubing scraps for 10 years! So glad I got to use them! I also like to know that ill have a little bit of my f150 forever.


    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  35. #35
    Member kabacj's Avatar
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    More solid progress this weekend.

    I tell you I must have spent 3 hours staring at this problem over the past two weeks. My goal is to add SCCA and NASA legal door bars to a car that can be street driven. Ideally I should be able to cover the bars and make them look less race car and more street car. Finally I don’t want the bars to make entry or exit any harder.

    The ideal way to attach door bars to the stock frame would put the bars right in the same plane as the current window and interior door frame. With this situation the door bars occupy the same space as the stock door frame. If you want working windows and doors this option is out. Several racing bodies also prohibit removal of the stock door framework. In order to install door bars you either need to make a bar that squiggles it way around the obstructions and spans a large distance, or you need to create new landing areas for the door bar structure.

    After considering all of the pros and cons I decided new structure to attach the door bars would be easier and stronger.

    The first problem was the rear verticals. I did not want to break the plane of the firewall and I also needed to avoid blocking my fuel tank install. The tank is so tight, I have no more then 1/8 clearance at the pinch points. I can just glue some rubber on to the frame to cushion the tank and it does not need any other mounting. (but I will mount it firmly)

    Now the verticals. The bottom of the tube lands right where stock corvette seat belts attach. I will not use those seat belt mounts so I cut off the plate. In order to make attaching the tube easier, I used the cut off pieces of seat belt mount to weld up a continuous horizontal plate to attach the vertical bar. It makes it easier to slide the bottom of the bar in from the front. It wedges in when its too long. This way I can sneak up on a tight fit.


    I cut and bent two symmetrical but mirror image vertical bars for the driver and passenger side.



    What’s cool is the vertical clears the stock cross brace but is just touching. I Debated cutting the cross brace out , but there is not much gain and its possible that the frame would pretzel if I took out that support. The frame is jig welded and I found it to be pretty symmetrical, however when its cut apart it will spring to relieve any pent up stresses.



    I ended up using the cross brace as another point to attach and stiffen the rear vertical.



    Next was the front vertical. I attached the bottom to the 2x2 square that runs across the foot box and the top of the tube to my window frame gusset. The gusset was an easier attachment point because I could more easily run a bead around the joint. I think it looks cool there too. With all this new structure the frame is starting to look like a fortress.



    In keeping with my street car/ stealth race car theme I can also hide these supports under the dash .

    Finally the whole point of adding the vertical bars is to add the horizontal door bars.

    The lower bar is a simple straight bar. It runs just slightly inside the door shell. The top bar is the tricky one. I am going to mock that one up because I think if done properly it might not obstruct the entry into the car at all and yet still meet the safety requirement. I have seen corvette bars where the top bar is an S bend allowing the front half of the door bar to be lower. This is key in the GTM because swinging your feet out is a little tricky. A high set of door bars in this area is going to make it very difficult to get out.



    Getting out with the X style door bars would be very hard. Basically you would need to crawl out or be very good at yoga.

    All the vertical elements were welded up. Next weekend is mock up, cutting,and fitting the horizontal elements.


    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  36. #36
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    What are your plans for the main hoop height requirement? Unless you are rather short, this is the other MAJOR problem with the FFR GTM cage.
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  37. #37
    Member kabacj's Avatar
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    Quote Originally Posted by crash View Post
    What are your plans for the main hoop height requirement? Unless you are rather short, this is the other MAJOR problem with the FFR GTM cage.
    Im 5'7. 140 lbs. so that helps with the helmet clearance issue. Helped racing bikes too. Its always nice to automatically have a weight advantage on the race vehicle running down the track.

    With the conventional left hand drive GTM seating position, isn't it pretty easy to use a reclined seat to gain the required head room with the racing seat at floor pan height? Keep in mind that the bars that form a V in the roof follow the contour of the roof fiberglass. These curved braces increases the cage height to its maximum. Unless you raise the roof you would not be able to have more helmet clearance under the cage.

    Is the roof scoop on the PDG GTM actually a stealth gurney bubble allowing the cage to be even higher then the fiberglass roof?

    John
    Last edited by kabacj; 06-27-2012 at 12:06 PM.
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  38. #38
    Trick Tool Maker, Super Moderator Hankl's Avatar
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    John,

    It looks like you're going towards the SIB's we have in the Coupe, NICE WORK!!

    Hank
    “If you didn’t have enough time to do it right the first time. How come you always have time to go back and do it again?” FFR1000186CP

    Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car.
    Horsepower is how fast you hit the wall and torque is how far you take the wall with you.

  39. #39
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    Quote Originally Posted by kabacj View Post
    Im 5'7. 140 lbs. so that helps with the helmet clearance issue. Helped racing bikes too. Its always nice to automatically have a weight advantage on the race vehicle running down the track.

    With the conventional left hand drive GTM seating position, isn't it pretty easy to use a reclined seat to gain the required head room with the racing seat at floor pan height? Keep in mind that the bars that form a V in the roof follow the contour of the roof fiberglass. These curved braces increases the cage height to its maximum. Unless you raise the roof you would not be able to have more helmet clearance under the cage.

    Is the roof scoop on the PDG GTM actually a stealth gurney bubble allowing the cage to be even higher then the fiberglass roof?

    John
    Yes it does allow for the bars to extend up higher into the roof area for added safety for the taller drivers.

    The rule states that the main hoop must be higher than the drivers head, and that there should be "reasonale" clearance for the helmet. I believe some sanctioning bodies specify around 2". This and the kicker placement are THE two main issues that have to be addressed. In a stock GTM there simply isn't enough leg room to lay the driver back without changing the footbox area.

    Have you spoken with the official you had look at your setup about this potential issue?

    I actually had to raise my roof 1.75 inches to meet this requirement on my new GTMR. That's even with the reclined driver position...but I'm 6' 3".
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  40. #40
    Member kabacj's Avatar
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    Quote Originally Posted by crash View Post
    Yes it does allow for the bars to extend up higher into the roof area for added safety for the taller drivers.

    The rule states that the main hoop must be higher than the drivers head, and that there should be "reasonale" clearance for the helmet. I believe some sanctioning bodies specify around 2". This and the kicker placement are THE two main issues that have to be addressed. In a stock GTM there simply isn't enough leg room to lay the driver back without changing the footbox area.

    Have you spoken with the official you had look at your setup about this potential issue?

    I actually had to raise my roof 1.75 inches to meet this requirement on my new GTMR. That's even with the reclined driver position...but I'm 6' 3".
    Oh see the problem is you are too tall. I don't have any of those problems. Ha just kidding.

    I have the required 2 inches as well as have my helmet below the rear hoop, but I can see how it would be nearly impossible to get a 6 foot guy in a comfortable position under the stock cage without altering the foot box or adding the gurney bubble. Of course the GT40 also had the same problem. A 6 foot guy is really stuffed into that car and in some cases will not even fit. Forget about getting helmet clearance. Check out Jeremy Clarkson when he tries to drive an original on YouTube. The door hits the side of his head. He needed to get a modified version in order to fit.

    John
    Last edited by kabacj; 06-27-2012 at 02:18 PM.
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

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