GTM roll cage modifications and race car build log

Quote:

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Originally Posted by mikespms

Hey John,

Very cool! It will be like riding a 4 wheel motorcycle. What is your first gear and final gear ratio,In your video it looked like you where going 150mph@6000rpm was that in 5th? Did the trans come with a rear mount or you have to make it,looks like the pad with the 4 holes on the side of the trans would line up with your rear frame mount with minor modification.Or is that for the shifter? Is there anything like this available for that trans or do think this may work(dynojet quick shifter)http://www.dragspecialties.com/search/?ci[0]=204&ct1=3071&format=json&q=&offset=282&rows=6
That car is going to be a blast to drive.

Mike

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Hey Mike

Ill need to dig up the ratios for you but when using the SDR I am going 150 at 6k in fourth. The motor makes power up to 7k and redlines at 7200.

The pads you see on the side actually are for brackets that hold the shift cables. I took them off in order to try to get the stock subframe to fit on. Unfortunately the tail housing of the S4 is larger then the SDR. The gear actuators are also farther back so the stock hanger is not going to work. I designed a new hanger over the weekend that I will make out of aluminum, but I realized this am i might be able to modify the stock hanger. its going to be heavy, but it might be quick enough to justify.

I am not sure which shifter I am going with, but I was thinking about this one. http://hargettprecision.com/index.ph...equential.html

I was a little sad to take apart all the stuff that was working so well, but at the same time it gets me closer to my dream car.




John

Quote:

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Originally Posted by crash

As I have mentioned before, Team PDG uses the stock GTM shifter. We just changed the pivot points and U joints to make the entire setup much tighter. It took a little tuning, but it works very well. Just an option.

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Good idea Crash. I dont have the factory five setup anymore as I traded most of it in when I got the cable shifted SDR. Since I want to be able to swap the SDR and S4 in and out... not that I will, but I wanted to be able to have a street friendly setup and a track friendly setup if the need arrises. Makes my life a bit more difficult short term, but its also a fun challenge to see if I can do it.

If I am successful I will be able to swap out the transaxle and shifter / cables between the SDR/ a Porsche Box/ and the S4 in an afternoon. Why would I ever want to do that you ask? I dont know :) but maybe I would. I really hate when I could have made somthing easier if planned for it ahead of time. Im doing my best to plan for it !

John

Quote:

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Originally Posted by crash

As I have mentioned before, Team PDG uses the stock GTM shifter. We just changed the pivot points and U joints to make the entire setup much tighter. It took a little tuning, but it works very well. Just an option.

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Crash on second thought. I might be able to rig up somthing using solid rod. That will take lots of brain power however. I want to just get it going with cables first.

I have enough fab work to do just to get the swap going.

I'll call you when I am ready to start that project.

Thanks for the suggestion.
John

Quote:

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Originally Posted by kabacj

Hey Mike

Ill need to dig up the ratios for you but when using the SDR I am going 150 at 6k in fourth. The motor makes power up to 7k and redlines at 7200.

The pads you see on the side actually are for brackets that hold the shift cables. I took them off in order to try to get the stock subframe to fit on. Unfortunately the tail housing of the S4 is larger then the SDR. The gear actuators are also farther back so the stock hanger is not going to work. I designed a new hanger over the weekend that I will make out of aluminum, but I realized this am i might be able to modify the stock hanger. its going to be heavy, but it might be quick enough to justify.

I am not sure which shifter I am going with, but I was thinking about this one. http://hargettprecision.com/index.ph...equential.html

I was a little sad to take apart all the stuff that was working so well, but at the same time it gets me closer to my dream car.




John

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That's one awesome set up,you need a long straightaway for 5th gear. That Hagertt shifter looks good,the dynojet quick shift and others like it works in conjunction with your shifter. They work with a button shifting and momentarily interrupting the ignition allowing to shift with out the clutch instantly , used on bikes for drag racing and for people that don't know how to use the clutch . Don't know if dynojet makes something for the ls, but if there is a way to momentarily interrupt the ignition it would work like a paddle shifter.
Just an idea:cool:
Mike

Quote:

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Originally Posted by mikespms

That's one awesome set up,you need a long straightaway for 5th gear. That Hagertt shifter looks good,the dynojet quick shift and others like it works in conjunction with your shifter. They work with a button shifting and momentarily interrupting the ignition allowing to shift with out the clutch instantly , used on bikes for drag racing and for people that don't know how to use the clutch . Don't know if dynojet makes something for the ls, but if there is a way to momentarily interrupt the ignition it would work like a paddle shifter.
Just an idea:cool:


Mike

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Hey Mike. The dynojet kill switch is a good idea. I have something like that on my 125 race bike. The benefit , for me at least, was energy savings over a long race. Just the little bit of mental and physical effort to chop the throttle on up shifts was significant. It allowed more time to relax instead of needing to concentrate on shifting. Sounds like a minor thing, but it was amazing how much of an advantage it offered.

I bet my ecu can take a momentary kill input. It has a boat load of features I have not even started to investigate. I'll find out.

The dynojet kill switch might be a good idea for team PDG. Endurance races were where I found the most benefit.

Re finding a track where I can use fifth gear. I can't wait. 4th pulls hard all the way to redline. You can see on the video I'm pulling longitudinal .3 G under acceleration in 4th. I will need to trim out the wing going much faster, but I figure road America or Daytona will be good places to test out 5th.

Those tracks are on my wish list.

John

Add VIR to your list if you want to wind the car out in 5th, along with Pocono. Some clubs do run the Long Course, using the North infield, front straight, and turns 1 and 2. Basically the North Course but with the other parts of the tri-oval. Some clubs run the full tri-oval in the afternoon; cars that go less than 140 find it a bit boring... Also, have you done Summit Point Main circuit? I bet you could take turn 11 at 80-85, and then you have 3/4 of a mile before turn 1 at about 50. Here is some old footage of turn 11 to 1:
https://www.youtube.com/watch?v=XB8MaGlpiaU#t=10

Hey Keith!

I'll run Pocono this year hopefully VIR.

I have heard the same thing about running the trioval. It's only fun above 150. I have only driven an oval once in my life. It's actually fun. Driving up and down the banking as well as taking the turns as fast as possible is harder then it looks.

The turns that look the same on TV have a whole new meaning at speed on the track. Each turn has its own character.


Regarding the build. Parts and raw materials are starting to arrive. A new starter, lots of aluminum, tires, rims and some wiring supplies.

It's going to be a busy weekend.

John

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Originally Posted by kabacj

I was looking for some inspiration to get out in the garage and get the GTM ready for the track and I was reviewing videos. I thought I would share this one.

http://youtu.be/tOvqqEmCujE

John

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That is one cool video John!!!!!! Hadn't had time to see it till now. Just WOW!!!!!!!!!!!!!!!!! The sustained Gs you are pulling are awesome.
How accurate is your telemetry? I noticed that on high G turns and under heavy braking your oil pressure is really dropping. You might want to take a look at that. For example look at 2:56, 3:59, 4:57 under braking and 5:58 at 1.20 Gs. There are more but just wanted to point out a few instances.

You can see that the wing is making some downforce because it flexes downward on the straight. All of ours do that too. Some more than others, but yours indicates that it is building a good amount of downforce.

Is this engine dry sumped?

Quote:

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Originally Posted by Kempo

That is one cool video John!!!!!! Hadn't had time to see it till now. Just WOW!!!!!!!!!!!!!!!!! The sustained Gs you are pulling are awesome.
How accurate is your telemetry? I noticed that on high G turns and under heavy braking your oil pressure is really dropping. You might want to take a look at that. For example look at 2:56, 3:59, 4:57 under braking and 5:58 at 1.20 Gs. There are more but just wanted to point out a few instances.

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Hi Hugo. Glad you like the video.

I knew when I posted the video somebody would see the oil pressure fluctuation. Regarding the telemetry. I have confirmed the MPH, the G Meters are accurate. Those readings come from the STACK data logger and I have compared them to another data logger back to back. The Engine signals I record come via the CAN bus on the ECU. Since all the programming on the ECU is custom and the ECU decoding on the stack DVL is also custom, and I did not calibrate the two last year I am not sure that the ECU numbers are perfectly accurate. I was always more worried about car setup rather then camera/ data setup.

Thats a long way of saying I am not sure how accurate the readings are. You can see the throttle never hits 100% even tho I assure you I am flat on the floor. The temp seems a little low to me.... but yes the oil pressure is a concern.

Even if its just a relative number its clear that there i some oil starvation going on in the video. After this run I noticed the same thing and added more oil to the motor. That seemed to lessen the variation in oil pressure on later runs. Its also note worthy that I see negative oil pressure. That's a little weird. Maybe it can happen but seems unlikely.

Mast motorsports have a special extra deep high capacity oil pan they use that they claim solves the oil starvation problem commonly seen in LS3s. It is most likely true that the oil pan solves the issues in most cars but it looks like the GTM develops higher G loads longer then most cars.

For the short term the plan is to put in an accusump. Since I only seem to see the issues under hard braking and the 3 qt accusump is supposed to be able to provide up to 60 seconds of oil pressure. It might be a work around. I hope so anyway.

Thanks for the observation. Im glad people are watching my back.

John

Quote:

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Originally Posted by crash

You can see that the wing is making some downforce because it flexes downward on the straight. All of ours do that too. Some more than others, but yours indicates that it is building a good amount of downforce.

Is this engine dry sumped?

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Crash you made my day. That is the coolest thing EVER! I have never heard about or seen a wing flex under load like that. Its pretty easy to see if you watch the space between the wing edge and the text. The space grows and shrinks as the speed changes. Its interesting that your wings do that too. I know you guys have a super down force configuration with a multi element wing. It would be nice to measure how much down force I am making I am going to work on that. Have you guys done that? I know my data logger has an input for linear potentiometers. Its just an expensive setup to find out facts that are cool but its not like I am racing for money and can justify it.

No unfortunately its not dry sump yet. As I said to Hugo, I am going to try to get by with the accusump and make sure to keep the motor very full of oil to avoid any starvation issues.

It depends on how things go this year, but dry sump is on the short list. I knew I would need one. I just did not think it would be this soon.

Thanks a lot for the observation on the wing I am not kidding that is so damn cool. I am going to put cameras all over that thing and on the rear suspension so I can see what is really happening back there.

John

We have not measured wing down force with an instrument other than the seasoned GM factory test driver we had in the car last year, Paul Edwards, and the rest of us amateur drivers. This is actually a test session where we were doing back to back wing tests. https://www.youtube.com/watch?v=eZ9vIUi7aRY We can change our wing in about 30 seconds, so we went out, ran a few laps to get things warm and get a base line, then came in, did a wing change and saw how the feel and lap times compared. This is why it looks like Paul is up to speed so quickly on the out lap in that video...everything is already warmed up. :)

We are at the point where small changes make a noticeable difference in lap times and with drivers like Paul we can be assured that what he is telling us(besides what the computer is telling us) is indeed what is happening.

EDIT: Almost forgot, that video will also wet your appetite for how the Mendeola S5 will shift. It's a beautiful thing.:)

Sheeee-Nikes Crash that is one of the best videos I have seen from you. I think I pulled a 1G in my chair just watching it, and the Mendy is sweet

Thanks

I have to agree with Ron - GREAT video! My wife laughed at me as I'm steering and leaning into turns while I watched it!

It is truly amazing of the infectious passion this car generates. Who would ever thought of a group of enthusiasts could build a car and attract world class drivers for the sheer enjoyment of the sport of road racing! NOT IN MY WILDEST dreams. There has been over 100 people work on this car and another 100 just offering advise. I might add worldwide! You might also take in the account of operating an a very limited (small) budget! As Mike indicated, having Paul join us, it has been very educational and raises the bar each time we take the car out. If you had not read any of our other stuff before the 25, Paul was runner up in the Red Bull F1 search, then went to GM for 11 years as a test driver and then won a Grand Am championship in a Pontiac GTO. Most of his experience came from the European circuits, winning The Grand Prix of Monaco in a vintage Penske F1. We are so honored to all the talent, behind the wheel and behind the scenes. BUT, let's not forget the PDG regulars that have put this project in the winner's circle time after time!

Crash. That video is awesome. Nice editing and multiple camera views. I really can't wait to get out on the track with the new setup.

Richard you have put together a great program. I am looking forward to the day when you guys post a win at the 25 hour. It only a matter of time.

In order for me to get out on the track I need to make a new transaxle support and rear subframe. I could have cut up my old one, but I figured I have some time. Why not start from scratch.

This is the old sub frame. It also functions as my wing mount and rear tow hook receiver.
http://i1073.photobucket.com/albums/...psvapmauak.jpg

After drawing a few sketches. Step one was to make a foam model that allowed me to verify all the pickup points and make sure I would not have any clearance issues


http://i1073.photobucket.com/albums/...psqokfoubj.jpg


The next step was to make the mounts that attach to the frame. I could have used a bit of tubing with a half inch hole it and welded that to the frame, but I figured that a solid chunk of aluminum would allow me more welding surface and a much stronger part.

Boy it would be nice to have a mill, but I made due with the bandsaw.

http://i1073.photobucket.com/albums/...ps6mxfrvps.png

I drilled a hole in the frame and plug welded the mounting boss into the arm of the frame.

http://i1073.photobucket.com/albums/...psxa8iucul.jpg

Next I welded the box section tube closed.

http://i1073.photobucket.com/albums/...psvwl809yc.jpg

And welded the frame together.


http://i1073.photobucket.com/albums/...pstzpoyxs2.jpg

Now for the test fit.

http://i1073.photobucket.com/albums/...ps0h9xzdka.jpg

It fits!

Of course I put it in the car several times as I was welding to manage the warping as I welded. I basically warped it into shape using each subsequent line of beads to move the frame into the shape I wanted. The subframe drops into the mounting tabs on the frame. Even when using a jig I find that the stress builds up and the part springs out of shape a bit when you take it out of te jig. My method might not be the right way, but it works for me.

The new subframe will also be a rear bumper.

Still need to hang the transaxle. More to follow.

John

that is some pretty crafty stuff! great work!~

R

very nice. those welds are super. looks like the right way to me.

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Originally Posted by Cobra 61

that is some pretty crafty stuff! great work!~

R

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Quote:

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Originally Posted by carbon fiber

very nice. those welds are super. looks like the right way to me.

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Thanks Richard and Jason,


Last weekend I spent most of the time staring, drawing, modeling and measuring. After many mental iterations of the design i decided to make the parts of the design that I was happy with.

It took me two days to make this part even though the actual building only took a few hours.

http://i1073.photobucket.com/albums/...pstzpoyxs2.jpg

I have spent the week building the remaining parts of the subframe and transaxle mount in my head. Imagining the stress loads and also the possible difficulty installing or removing the parts.

I hate when you put things together and in order to work on part A you need to take out B, C , D, E and F.

I want to be able to take out any part without messing with the other parts. I also wanted to take the rear subframe out without forcing the body out of the way to clear.

I want this car to be like my two stroke race bikes. you can take the whole thing apart rebuild it and put it back together in an hour.

Requirements

1)light weight but strong
2)stiff but not rigid attachment of the Transaxle to the subframe
3)easy installation and removal
4)transaxle bracket and subframe structure that can stand up to the fatigue loads of the track


I had a hard time with how I would design the attachment point between the transaxle hanger and rear subframe.

Factory five did a nice job with the mendiola SDR mount. You insert the bottom bolts and swing the mount up into position insert the top bolts and drop the transaxle down on the pads.

http://i1073.photobucket.com/albums/...psmq1zwzxo.png

I wanted to carry the same idea, but of I could not rest the transaxle on the subframe like factory five did.


I have come up with this side view of how the bushing will connect with the subframe and transaxle hanger.

http://i1073.photobucket.com/albums/...psbwnogsog.jpg

the bracket will hang from the subframe instead of resting on it. I figure i will weld rings that capture the bushings and that will stabilize the setup as well as limit some of the motion but still allow twist in compression.

here is a top down view of the subframe with bracing and mounts for the transaxle hanger.

http://i1073.photobucket.com/albums/...psrgvzs4wx.jpg

I have a assortment of polyurethane bushings and hardware. It will be interesting to see how this all works out.

John

Good progress this weekend. As usual the I thought I could get more done, but at least the work completed came out well.

I needed to support the rear sub frame with a method that would be strong enough to support the transaxle as well as stabilize the subframe if it were to get a nudge from a car following too closely on the track.

I figure using the design I used for the rear strut supports that make a V over the motor would be both strong and easy to fine tune.

http://i1073.photobucket.com/albums/...F5671AF553.jpg


Now for the time consuming part. I machined 4 ends for the struts that support the rear subframe. One side of the strut has left hand treads and a rod end.

http://i1073.photobucket.com/albums/...psbzt02ldp.jpg

The other side has right hand threads and a rod end.

http://i1073.photobucket.com/albums/...ps7wtvfjg0.jpg

Each end has a press fit into an aluminum tube. This ensures prefect alignment and makes a very strong joint. I'm sure The the ends would stay put even if they weren't welded.

http://i1073.photobucket.com/albums/...ps24iqsi04.jpg


Next I made some brackets out of 1/4 inch aluminum plate and welded it all up.

http://i1073.photobucket.com/albums/...psjkaascby.jpg


The solution works well. Plenty of room around the transaxle and very strong.

http://i1073.photobucket.com/albums/...pslnrreufs.jpg

John

The family insisted that I attend the family vacation so my other child, the GTM, did not get much attention over the past two weekends. It was great to get some quality family time.
On the other hand I have a deadline to get the GTM back out on the track so I spent a few hours on it this weekend.

http://i1073.photobucket.com/albums/...psbmzj65vo.jpg


Two major points of progress. I installed an x brace in the rear sub frame. Boy it's stiff! I actually think it will play an active role stiffening the rear shock towers now.

You can also see the plywood template I made to pickup the mounting points on the transaxle and subframe. More refinements needed here but I'm close.

Finally I tipped the whole subframe down so it does not block the holes in the body where the exhaust pipes exit. My original idea was to run the frame perfectly level off the top mounting tabs like factory five does. The problem is my subframe is much wider and more visible from the rear. There is no reason it needs to be level in my application so I decided to tip it down.

Part of the adjustability I get with the left and right hand threaded links are changes like this one. I just made both links a half inch shorter and I am golden.

John

Looks awesome... Your craftsmanship is inspiring.

I ran my front brake lines this weekend, finished up the throttle cable/assembly and started building my custom axles. It was nice to be able to work with the garage door open.

A few neighbors stopped by so that's motivating in itself.

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Originally Posted by longislandwrx

Looks awesome... Your craftsmanship is inspiring.

I ran my front brake lines this weekend, finished up the throttle cable/assembly and started building my custom axles. It was nice to be able to work with the garage door open.

A few neighbors stopped by so that's motivating in itself.

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I must agree working with the garage door open is great. Sadly I need to keep it shut when I'm tig welding so the breeze does not blow the shielding gas away and mess up my welds.

Hopefully I'll have the GTM street legal by June. I'll stop over so I can see a 818 under construction.

John

I learn alot watching guys like you. What is your background, what have you done that makes this stuff such a no brainer for you?

You have a tig welder, you have some kind of band saw, drill press, lathe, or a mill. I'm really thinking I need to open my eyes, I have been building cars off the floor of my garage for so many years. Using crude tools, making a bracket out of some other combination of metal that was in my bin. It all comes out good, but I'm missing the boat., too much work.

You really didn't need much to make that rear brace, did you?

Quote:

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Originally Posted by fastthings

I learn alot watching guys like you. What is your background, what have you done that makes this stuff such a no brainer for you?

You have a tig welder, you have some kind of band saw, drill press, lathe, or a mill. I'm really thinking I need to open my eyes, I have been building cars off the floor of my garage for so many years. Using crude tools, making a bracket out of some other combination of metal that was in my bin. It all comes out good, but I'm missing the boat., too much work.

You really didn't need much to make that rear brace, did you?

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Ha thanks Gene you are too kind.


I have been very impressed with the metal parts you made, like your rear hatch supports. A whole lotta hand work to get them done but they looked GREAT. Of course a black car will highlight the beautiful bodywork you have done. Yes sometime tools make it easier but often they simply make your work faster and more accurate.

What experience do I have?

I sit at a desk all day. I have never built a car. I did'nt tig weld before I got the kit. I have no engineering training I have never raced cars. I just got all these tools in the past 3 years. I really have no idea what I am doing. I simply learn as I go.

I have a talent for building things in my head in 3D and imagining how they will work in the real world. I spend quite a bit of time thinking about how this stuff will work under stress loads before I start building. I test ideas/ prototype them if I can. I second guess myself until I have run out of things to second guess.

I am also a good copy cat. If you dont know what you are doing, copy somebody who does. You will probably end up in a good place. I study how race cars were made in the 60s and 70s and how they are made now. Lots of pictures on the internet to get ideas. Im sure the internet makes this stuff I make look like I just throw it together. But I really work at the design before I build anything.


Tools:

I have a good tig welder. I have a good band saw that is designed to chop angles and retrofitted it with a small table. I have a 1950s lathe and a ton of woodworking tools including the drill press. All of my metal working tools were purchased used for under $1k total so they are very affordable in the context of the GTM expense. I needed all of them to make the rear transaxle sub frame and hanger.

I ended up buying all these metal working tools so I could make the bits that stand between me and a successful custom project. Although I don’t enjoy having to make stuff under pressure of a deadline like I am doing now with this transaxle hanger, I really love making stuff. When I retire that’s all I will do.


I just try to make parts that are functional and pretty. I like to solve problems. I’m glad to share them with you guys. Hopefully my solutions work. If they don't ill be sure to tell you so if you make parts like I have you can learn from my mistakes. Having the right tools for the job makes it a whole lot easier.

I have a little God given talent, TONS of determination and $1000 dollars worth of used tools and a welder. This work is not a "no brainer" for me. It just looks like it is :)

John

"I sit at a desk all day. I have never built a car. I did'nt tig weld before I got the kit. I have no engineering training I have never raced cars. I just got all these tools in the past 3 years. I really have no idea what I am doing. I simply learn as I go"

Sorry John I have to call BS on that statement.

I've seen, worked with rookies, and examples of your work is not that of a rookie. Unless.......

You got a pro doing all the work and then you come in behind and take the pictures, and try to "shine" us forum wingnuts. :rolleyes:

Ron

Well, like I said, I'm missing the boat then. I haven't baught a tool in 20 years, I think I will look into some of that stuff when I get the GTM done.
Thanks man

Quote:

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Originally Posted by Presto51

"I sit at a desk all day. I have never built a car. I did'nt tig weld before I got the kit. I have no engineering training I have never raced cars. I just got all these tools in the past 3 years. I really have no idea what I am doing. I simply learn as I go"

Sorry John I have to call BS on that statement.

I've seen, worked with rookies, and examples of your work is not that of a rookie. Unless.......

You got a pro doing all the work and then you come in behind and take the pictures, and try to "shine" us forum wingnuts. :rolleyes:

Ron

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Very funny Ron and thank you for the compliment.


My mom says im not your average rookie. My wife says im borderline certifiable.

I keep working at something till I get it. Funny one definition of insanity is doing the same thing over and over and expecting a different outcome. Maybe my wife is right!

Scouts honor no BS. My statement is 100% true.

John

It was Good Friday. T- 10 days and counting.

I have 10 days till I'm due out on the track for my first event of the season.

On the list for today.

Transaxle hanger bracket:

I have already made a cardboard template then transferred that template on to a piece of 1/4 inch plywood.

http://i1073.photobucket.com/albums/...ps27379d37.jpg



After cleaning up and mounting the plywood I was able to see that the relationship of the bracket and rear subframe was going to work.


Next was transferring the shapes to aluminum.

Cutting the convoluted section was a real pain. The 1/4 inch 6061 aluminum does not cut well with a hand held air saw. I my only option was nibbling out the inside curves on the bandsaw then cleaning it all up with a die grinder and carbide bur. It was time consuming, but it worked.

After all that work to make the hanger I needed to drill out the mounting holes. I don't like making over sized holes to account for tolerances. I wanted the holes in the bracket to be the same 3/8 inch as the mounting holes in the transaxle. It's very hard to drill 4 properly aligned holes within a few thousandths of tolerance. I need a CNC mill! I reminded myself that in the good ole days before computers machinists did it all the time. It can be done.

I painted on a layer of machinists dye and marked the holes. I drilled a pilot hole with a bit that minimizes runout and wandering and then drilled out to the final 3/8 size. To my relief all 4 holes were perfectly aligned.

http://i1073.photobucket.com/albums/...psqyv9vibt.jpg



With the hanger bolted up I was able to see where I needed to install the brackets on the rear subframe that would receive the bushings. Using some of the scrap from the hanger I cut and welded the brackets. Next I drilled a hole to receive the polyurethane bushing.

http://i1073.photobucket.com/albums/...psyryl7vxb.jpg


With that done I needed to fabricate some bushings.

I had hoped to find something off the shelf, but it turned out that it was easier to make the needed bushings. I researched buying a cast rod of polyurethane,but it turned out that It was much cheaper to buy a bunch of polyurethane suspension bushings for a total of $20.

Now all I needed to do was mill the suspension bushings to size. Most sources said that I would need to freeze the polyurethane with liquid nitrogen so I could cut them on the lathe. That would be a problem. Because polyurethane is not easy to mill most bushings are cast in the shape needed.

I figured if I made a razor sharp cutter with the right shape I should be able to turn the bushings. Well that might be true but I still needed to hold the bushings in the chuck. That was not working. Once gripped in the chuck the bushings deformed and were not held tightly enough for accurate machining.

No problem. I'll hold them another way. I machined a piece of brass rod, sized so I could just barely press the bushing on by hand. Since the bushing was expanded slightly I would need to account for that when I cut my final outside diameter but at least now I am ready to cut.

http://i1073.photobucket.com/albums/...pskq65m6jc.jpg

The system worked perfectly. I was able to turn ribbons of polyurethane off the bushings and both cut and size them as needed.


I milled up my bushings. While I was lathing parts I turned sleeves that limit the compression of the poly as well as attached aluminum washers.

http://i1073.photobucket.com/albums/...ps2lxfqzs8.jpg

Now the test fit. I used the bushing pressed into the cross brace as a drill guide so the bolt dropped right into the hanger. I tightened it up. Looks like its going to work.

http://i1073.photobucket.com/albums/...psmsgsyy9p.jpg

Whew. That was a lot of work for one day. Easter weekend is not a great weekend for getting work done so I needed to cram in all the work while I could.

John

Impressive work as usual John. Said it once and I'll say it again you really, really, really, have skills.

Quote:

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Originally Posted by Kempo

Impressive work as usual John. Said it once and I'll say it again you really, really, really, have skills.

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Hey Hugo! Glad to see you are still hanging around the forum. Please keep reporting your adventures with the GTM. I hope one day I can have as many pin up girls around my GTM.

Right now I need to keep my mind off the pretty girls and focus on finishing the GTM in time for my track visit on Monday.

Saturday and Sunday of Easter weekend were mostly dedicated to family visits but I was able to spend a few hours in the garage.

On the task list

Remount the rear wing/ body support:

Since I tipped the rear sub frame down so its not visable from the rear, the rear wing support needs to be a little taller. That ment I needed to move the threads that hold the rod ends down about 3/4 of an inch. I lathed up some aluminum rod and welded it on to the frame extending the threaded section.

http://i1073.photobucket.com/albums/...pskzegrnuh.jpg

Next I needed to attach the struts that locate the rear wing body support. More brackets and welding.

http://i1073.photobucket.com/albums/...psgoztrfh9.jpg


Finally the last bit of fabrication is to add the exhaust supports.


http://i1073.photobucket.com/albums/...psbqsd8lhk.jpg



I had made exhaust suports out of 3 inch clamps. These worked fine over the past year at the track. It seems like the exhaust wrap I installed between the clamps and the muffler tubing (not pictured) was enough to prevent the rubber from melting even under the high heat of track conditions.

http://i1073.photobucket.com/albums/...A95E36AED5.jpg

And here is a shot of the sub frame and wing support all ready for installation.


http://i1073.photobucket.com/albums/...pskjxvxent.jpg


Now all I need to do is modify the shifter and hook up the cables and I'll be ready to go.

That is awesome. Good luck finishing it up this week.

Quote:

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Originally Posted by longislandwrx

That is awesome. Good luck finishing it up this week.

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Thanks. I finished ! But as you may have guessed. That's not the whole story.



My normal thrash to get all of my planned upgrades complete prior to the first weekend of the year ended 8.00pm Sunday night for Mondays track day.

I finished my punch list that includes new tires I mounted and balanced myself. (Both a first)with bigger 275s up front. New exhaust section from kooks without the cat section that roasts the cv joints at track temps. New sequential transaxle and sequential shifter and dual disk kennedy stage 2 clutch. A re designed, light weight rear sub frame that also acts as a rear bumper.

Testing things out at home I ran the transaxle through the gears on jack stands. I also checked out my modified shifter. It all worked. That was amazing in itself. The reverse setup was heavily modified and that even worked!

I drove it in the driveway in forward and reverse. All seemed great! It was a late night by the time we had packed up. Off to the track at 3am



We arrived at the track at 7am. A little tired I roll the car off the trailer

As usual it attracts some stares

I start it up and that turns heads. It sounds really good without the cats .

The I put it in gear which is still an odd experience pulling directly back for first

Let out the clutch. It barely grabs. Odd

I go back and adjust the slave cylinder till it's barely any travel moving the clutch fork to disengage the clutch. Still nothing.

I knew it was bad. This is not how a new clutch fails. You can't slip it or you can't get it out if there is a problem. Since it's a multi disk dry clutch you can hear when the pressure is off. It sort if rings. When I let out the clutch I hear pressure being applied but no drive.

My gut said call Kennedy. It felt like I had the wrong friction disk or steels. Too thin or something like that. I waited till they got into the shop in California. In about 30 seconds he knew what the problem was. One of the clutch plates needs a small chamfer added to it. A few seconds with a dremel will fix it he said.

Turns out others had the same problem. Without the chamfer there is enough extra metal to keep the friction disk nearest the flywheel from touching the flywheel.
http://i1073.photobucket.com/albums/...psfnevmlbu.jpg
I was disappointed that I could not drive the car, but it comes with the territory. Low volume custom parts all mixed together. I expect some "tuning"

I wish i would have done some hard throttle test runs at home, but it was poring rain Saturday and Sunday night blasts at 8pm would not have been popular with the neighbors.

Good news is I'm back at the track on the 16th

I hope to get my nasa racing license. The neighbors are just going to have to deal with a few loud blasts up and down the street while I test out the clutch setup

Out comes the transaxle. Again! It's ok. My new multi part subframe should cut down on the time.

John

Good lesson in what happens regularly in racing...just about anything you can think of...and everything you haven't!

I would of had to pull it apart at the track. Even if I ended up towing it home in pieces. I figure I went through that much effort, I may as well add a little bit more.

Quote:

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Originally Posted by crash

Good lesson in what happens regularly in racing...just about anything you can think of...and everything you haven't!

I would of had to pull it apart at the track. Even if I ended up towing it home in pieces. I figure I went through that much effort, I may as well add a little bit more.

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Don't think I didnt consider going to harbor freight and getting and engine crane and pulling it out. I went to bed at 12.30 after I finished loading up the trailer and doing other odds and ends. I just cant stop working on stuff if I have time. I woke up at 3am to drive to the track so I was working on only a few hours of sleep. The forcast was for heavy rain on Tueday so it was likely to be a wash out. AND altho I had brought enough parts and tools to rebuild almost anything I forgot one key thing. The stupid clutch alignment tool! The barriers kept adding up.

If I had anything like normal energy levels I would have done it, but yeah it was pretty hard to admit failure and go home.

In a pinch you can use a socket and a short extension for an alignment tool. :)

Quote:

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Originally Posted by crash

In a pinch you can use a socket and a short extension for an alignment tool. :)

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Yep that's a good idea. I was going with the plan of going to Home Depot getting a pine dowel and turning it down to size then adding a strip of metal to align the splines on the multi disks. You know something quick and simple.

Course I could always call Ian and ask him what Porsche input shaft the Mendiola s4 uses. Do you happen to know what input shaft the Mendiola s4 uses? Getting that tool at autozone may be a problem tho

Needless to say the engine crane and clutch alignment tool will be in the trailer next time.

I believe the splines on the S5 are of something American made. Can't completely remember, but I'll see if I have a reference. :)

Hey John,

http://store.snapon.com/Clutch-Servi...r-P635965.aspx
I have one of these it works well when you don't have an old input shaft for alignment

Quote:

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Originally Posted by crash

I believe the splines on the S5 are of something American made. Can't completely remember, but I'll see if I have a reference. :)

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Thanks Crash

Quote:

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Originally Posted by mikespms

Hey John,

http://store.snapon.com/Clutch-Servi...r-P635965.aspx
I have one of these it works well when you don't have an old input shaft for alignment

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Thanks for the link Mike

Yes this clutch is tricky. I need to align both the plates with the pilot bearing and the splines of the disk.

http://i1073.photobucket.com/albums/...ps29mcdqe4.jpg

Needless to say I will carry the tool at all times now.