GTM roll cage modifications and race car build log

[kabacj]

My plan is to weld a plate to the underside of the floor pan to keep the seat clearance higher, but that might be difficult for welding a decent bead. I'm also ready for the seat belt install, and I see that you've modified the anchor points. Are you using theC5 belts, or something else?

Hi Tino. You could definitely weld a plate under the floor pan, but its much harder to weld over your head, and you only lose an 1/8 of an inch with the plate on the inside. I am using a six point system from Schroth Racing.



Yes I did need to add mounting points for the harness. It took a little trial and error to get all the mounting points in good locations where all the adjustments worked as designed. With the seat only a half inch off the floor pan the anti submarine belts were more difficult to install. Normal cars have he seat at least a few inches higher off the pan and as a result have easier belt routing options. Also note that the top mounts on my setup wrap around the harness bar I made. I did not use clips on the top, but I could have. I thought the bars looked nicer.

Good show man, looks good.

Thanks Gene. BTW no doubt the individual carbs on your sons car are more work, but you don't see them every day. I personally like that. And they look and sound so cool.

How about attaching it to the Harness Bar? seems logical to me!

Hey Mendo, some racing organizations require additional bracing to mount the upper part of the seat to the cage. or body structure of the car.

Something like this.



I don't like the idea of a pole pointed at my spine, and every forum has some horror story of a guy who was injured because his seat failed for some reason. I figure there might be a solution out there that we could borrow or modify to fit the GTM.

Maybe I will just brace the seat along the lines of many of the full containment seats out there and not add any additional mount. It does need something. I'm unsure what the right thing to do is so was looking to see if anybody has seen or experienced a solution that works.


John

[vnmsss]

Wow, John! You've been a busy, busy man! Thanks for posting all the pics...I truly appreciate how much work (design/engineering/fabrication/installation) you've devoted to making your GTM an amazing race machine! Big kudos, my friend....Very nice work!

Karen

[JCHRacer]

Hey Mendo, some racing organizations require additional bracing to mount the upper part of the seat to the cage. or body structure of the car.

Something like this.



I don't like the idea of a pole pointed at my spine, and every forum has some horror story of a guy who was injured because his seat failed for some reason. I figure there might be a solution out there that we could borrow or modify to fit the GTM.

Maybe I will just brace the seat along the lines of many of the full containment seats out there and not add any additional mount. It does need something. I'm unsure what the right thing to do is so was looking to see if anybody has seen or experienced a solution that works.


John

I was planning on filling the space between the back of the seat and the firewall with expanding foam like this stuff:

https://www.pegasusautoracing.com/pr...asp?RecID=1038

Should spread the load, it's light weight and will be WAY safer than the spine pole.

[Fraser D]

You could use something like this?
Not sure if it abides by the rule book.

http://www.jegs.com/i/JEGS+Performan...70291/10002/-1

[kabacj]

Update

T-48 hours

I have addressed many of the little issues I discovered last visit to the track.

One thing that surprised me was the lower aluminum under the radiator. It bent somewhere between 100 and 130 mph.

Reinforcement of this piece was on my list, however I figured this piece was bending on the gen 1 GTMs because the air intake is so large. Turns out the gen2 also requires reinforcement if you plan on hitting the track or you live in Germany where you can exceed 75 mph on the road

I used a piece of 3/4 square .063 aluminum. I plan on building something to fill the gap between the splitter and rad enclosure/ wheels. The square aluminum will act as a mount for this piece.


Second project was a vacuum canister to house my intake pressure sensor. With 8 throttle bodies I don't have a common plenum to measure intake pressure. I do have vacuum pickups at the base of each intake. These are combined and routed to this canister. With this setup I have a stable place to measure vacuum.



There was an open threaded hole in the top of the block so I built this canister to mount using that attachment.



I think I am going to redo this canister after I make the intake and coil covers but this is good enough for now.



Only a few more things to finish before the next test.

John

[kabacj]

On my first track day I built a temporary dash out of duct tape and cardboard.




It was very functional but not exactly pretty. It was time to make a more respectable temporary dash.

I cut and welded some aluminum into this frame. I then sprayed it with some wrinkle paint.



I added a bracket on the back so I could bolt the gauge cluster to the frame and steering column.



Next I drilled and tapped the frame and steering column to receive the same 1/4 20 stainless allen bolts as used on many of the interior parts.

I buried the wires in loom as best I could until I can make a shroud for the gauges



With this new setup I was able to move the gauges lower so I can see them all at once through the steering wheel even tho I am nearly sitting on the floor pan.



The top position is open for the transaxle temp gauge. I left out the gas guage as thats unnecessary on the track.. Ha I say that after I ran out of gas the last track visit. I figured I had enough gas for one more 20 min run. Little did I know I did not. The car shut down 100 yrds from pit in. The good thing I learned is that my tow hook works. The pickup, flapper/ sump setup in my custom tank gets every last drop from the bottom of the tank. And the car does not sputter at all before it runs totally dry... I guess that,s good.

John

[kabacj]

Wow, John! You've been a busy, busy man! Thanks for posting all the pics...I truly appreciate how much work (design/engineering/fabrication/installation) you've devoted to making your GTM an amazing race machine! Big kudos, my friend....Very nice work!

Karen

Thanks so much Karen. After 2 years I am really excited to get the GTM out on the track. Hopefully I'll be half as successful as you were with your coupe.

I was planning on filling the space between the back of the seat and the firewall with expanding foam like this stuff:

https://www.pegasusautoracing.com/pr...asp?RecID=1038

Should spread the load, it's light weight and will be WAY safer than the spine pole.

Great idea Joel. I like the fact that it spreads the load and is a great way to absorb energy in the event of an impact.

You could use something like this?
Not sure if it abides by the rule book.

http://www.jegs.com/i/JEGS+Performan...70291/10002/-1

Thanks Dave.

I had not seen this mount. Of course I could never buy something I can make. . This is a great design to copy elements from. Thanks for posting.

I was also thinking of welding some C channel to my seat like they did on this seat.



I figure I can mount a bracket like the one Dave posted but only need to worry about stabilizing the seat laterally. Preventing the top of the seat from twisting sideways in a side impact. Then using Joel's idea I can prevent the seat from folding in a rear impact. Then with some C channel I can stiffen up the shoulder and hip bolsters to prevent them from flexing and folding with a side impact.

Before I started all this I researched the companies that make custom full containment seats. They are both expensive and difficult to get fitted without bringing the whole car to their shop.

As we have discussed there is little room to fit a guy taller then me two inches under the stock cage height with a helmet on.

My ability to mount and tilt the seat at the ideal position was key.

Thanks for the suggestions guys.

Ill post what I come up with.

John.

[kabacj]

Thanks Hank and Crash. Hank your endorsement means a lot. The thing I like about the Stack setup is the software. It seems open and configurable. I also like the video support. It's less focused on the hey check me out on the track and more focused on video as another data stream for analysis. It's very easy to compare two video laps with all the other captured data. Lots of reasearch still needed however.

Thanks
John