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Thread: GTM roll cage modifications and race car build log

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  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.



    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; 03-14-2015 at 08:21 AM.
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

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    Procision-Auto'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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  3. #3
    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.
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

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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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    Talking about a tall guy not fitting in a racing gtm.

    A tall guy needs a GT 43

    http://m.youtube.com/watch?feature=mhee&v=UzC-mQoY3aI

    John
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  6. #6
    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!
    Brian Zakrzewski
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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

  9. #9
    Member kabacj's Avatar
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    I added the lower door bars on both the passenger and driver side. Both bars are as far outboard as possible while not intersecting with the diagonal square tube.

    Here is a view from the top



    here is a view from the side.



    John
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  10. #10
    Senior Member mikespms's Avatar
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    Quote Originally Posted by kabacj View Post
    I added the lower door bars on both the passenger and driver side. Both bars are as far outboard as possible while not intersecting with the diagonal square tube.

    Here is a view from the top



    here is a view from the side.



    John
    Hi Jonh,
    Are you going to put the other tubes in also?
    Drivers side looks good, where you able to fit the seat on the passenger side with the tunel panel in ?
    Mike

  11. #11
    Member kabacj's Avatar
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    The last weekend was a mad dash to get my car finished for my first track day October 6th. I am out of my mind to try to get the car finished that quickly, but I like a challenge. BTW by finished I mean it drives and has a primed body on it.

    This past weekend I painted up the chassis. It was kind of sad to cover up the steel, but it must be done. Its nice to see the frame shiny and black again.





    I welded up the engine compartment braces, made some double shear tabs welded them in and installed the braces.






    Installed my motor with Pfadt motor mounts, hooked up the cooling system, installed the belts, and installed the, fly wheel, clutch and starter.

    Here is an over head shot of the motor with the braces installed. They have right and left hand threaded rod ends so I can twist them up and preload the chassis. I am interested to see if I can notice the stiffness change by removing and adding them back on the track.



    Transaxle goes in tomorrow night and ill start wiring.

    So much to do so little time.

    John
    Last edited by kabacj; 09-19-2012 at 09:55 PM.
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  12. #12
    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; 12-27-2012 at 10:04 AM.
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  13. #13
    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
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

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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

  17. #17
    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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    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

  19. #19

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    Definitely looks better than the S bar.

    I would consider leaving the passanger side upper bar out entirely. You have tons of crush space between you and the passanger door, and including the lower frame rail in the equation, you already have two side bars there. If they say anything, just run a couple of stringers from upper to lower and you are good.

    Still not sure if the main hoop flies, but if the scrutoneer says it's good...then it's good!
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    Member kabacj's Avatar
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    After lots of thinking, I realized that the S bend top bar would be less strong then a straight tube. (see post 45 for a picture) Of course the S would bend over instead of pulling the verticals in.
    I spoke with "Hank" from the forum here who has much more experience at this than I. He pointed out that the top of the S would be near my helmet and its better to hit your head on a net then a bar.

    So change of plans. I decided to go back to basics. I built a cage in tape to see how it would relate to other parts.



    That looked pretty good so i made the top bar out of steel. I decided to go up to .120 wall tubing for the door bars. A few extra lbs here are worth the extra stiffness in my book.




    The front tips down so I can still exit in a dignified manner when driving on the street.

    I was thinking of making the passenger bar even lower. I will not have passengers on the track and for street use this bar is easy to get over. The last thing I want to hear is my wife complaining that its hard to get in and out of the car.

    note the front of the passenger bar nearly intersects with the lower door bar.



    I am not sure if this is NASA or SCCA legal. If anybody knows I wold be glad to hear it.

    I will run both sides by my local scrutineer to make sure he is happy with it before I weld it in.

    John
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  21. #21
    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
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  22. #22
    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

  23. #23
    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
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  24. #24
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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.

  25. #25
    Member kabacj's Avatar
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    Nearly done.

    I finished constructing and welding both the passenger and driver door bars.


    My concern on the passenger side was that entry and egress would be nearly as easy as stock. Although I most likely could have gotten away with a less structure on the passenger side, I am a sucker for symmetry. Having door bars on the driver side and nothing on the passenger side would bother me. Since they actually are very easy to get over I was pleased how they looked when added. Regarding entering and exiting. The bars don't actually get in the way. The car is so low the passenger can just sit in the seat then swing their legs in. My grandma could do it.


    passenger



    and with the body on.



    The driver side.



    and with the body.



    Funny how these things go. Now that its done I look at it and say of course you would do it that way. Prior to starting I was really unsure how the whole thing would go together.

    Since it has been so humid I coated the whole cage with POR 15 metal prep. A great idea I borrowed from the competition coupe build. The metal prep keeps the bare tubes from rusting while the final welding is completed.


    John
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  26. #26
    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.
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  27. #27
    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?

  28. #28
    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.
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  29. #29
    Member kabacj's Avatar
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    Unfortunately vacation has gotten in the way of the build.

    I was able to make a bit of progress today however with the addition of 1 inch square tube that re enforces the area that I needed to remove in order to install my single passenger side fuel tank. This braces the frame and I think reasonably equates to the strength of the structure as designed by factory five.



    My goal with the tank was to get as much capacity as possible with the goal of 18 gallons. Because of that I made the tank as high as I could and still allow filling using the stock filler location. The shape of the tank got in the way of the 1 inch tube I needed to add. I sorta knew this was going to be a problem, however I hoped I was going to come up with some way to re enforce the frame but not notch the tank. I could not think of anything that was as strong as the method I used so I needed to cut the tank.

    I bent up a little plate and welded it in.



    Ill loose a few ounces of capacity with that little cut out, but the 18 gallon number was just a target.

    I also cut the interior aluminum panels to fit around the new roll cage structure.

    John
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  30. #30

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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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  31. #31
    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.
    GTM # 344
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    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  32. #32
    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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    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.
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  34. #34
    Member kabacj's Avatar
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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
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  35. #35
    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?
    #28 FFR Challenge Series
    #28 FFR Type-65 Coupe
    2011 Western Endurance Racing Championship
    2010 West Coast Champion
    Drive it.....Like you stole it!

  36. #36
    Member kabacj's Avatar
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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
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

  37. #37
    Junior Member TheChief's Avatar
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    That looks really great! You are an insperation to us all.

  38. #38
    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

    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
    LS MAN's Avatar
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    John, superior workmanship, very impressive!

  40. #40
    Member kabacj's Avatar
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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
    GTM # 344
    Build Start December 2010
    First Start October 2012
    First Go Kart March 2013
    First track day April 2013

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