Jump to content
HybridZ

IMSA GTU vintage racer build


Recommended Posts

Agreed :) I have been building my war chest of paint over the past few months haha

I have silver, orange metallic, and black base coats. All are acrylic urethane with separate hardeners and reducers. I also have urethane clear coat is gloss and matte. I had to clear a whole 5’ square section of the garage just for bodywork stuff haha. 

Link to comment
Share on other sites

3 hours ago, AydinZ71 said:

Agreed :) I have been building my war chest of paint over the past few months haha

I have silver, orange metallic, and black base coats. All are acrylic urethane with separate hardeners and reducers. I also have urethane clear coat is gloss and matte. I had to clear a whole 5’ square section of the garage just for bodywork stuff haha. 

It's funny when you talk about painting a car, most everyone thinks about the physical act of spraying it. When it comes to bodywork, spraying is equivalent to the last 5 minutes in the history of the universe.

Link to comment
Share on other sites

ahahha, no kidding! The color is just the "sexy" part folks want to know about. I also built a war chest of bodywork material first. Durablocks... five rolls of varying grit paper, AL filler, regular filler, ahahha. 

 

Sanding sanding, and more sanding....

 

I have DA'd the existing finish down to primer/filler/bare steel. Using the existing filler matrix so I have less work to do, but down to bare steel on most of the car.

Link to comment
Share on other sites

  • 4 weeks later...
Posted (edited)

Slow progress. Close to finishing up the rear suspension. I keep finding things I need to clean and paint. But it is getting there. 

 

I suppose its time for the big reveal. Based on Cary's sugggestion, I am going with an external shock. Not sure I can get away with it, but its easily reversable. It was surprisingly easy to do. I used adjustable shock brackets from AA Manufacturing with a some angle iron for strength.  Even easier in the front to connect to tubing. I used 1/2 threaded rod with rod ends to mock it up. I 3d printed a shock body to make sure there was clearance. I took a set of cheap Toyota MR2 struts and drilled a little hole in the bottom to drain out the oil. They are loaded in the strut tubes just for keeping geometry, no friction.  The only tricky part is the motion ratio is different than the strut.

 

Right now I am thinking Penske 7500's for the shock. They are reasonably priced,  come custom valved to my parameters, have multiple lengths, and are double adjustable. 

20220703_193611.jpg

20220703_194946.jpg

Edited by clarkspeed
  • Like 1
Link to comment
Share on other sites

The MR2 struts will still see friction at the piston and upper strut bushing. Don't imagine it will be a problem to run them without oil since they won't be doing anything other than taking the side loads from the struts and you've eliminated all the heat from them actually damping.

Very cool idea. 

Link to comment
Share on other sites

On 7/4/2022 at 4:21 PM, JMortensen said:

The MR2 struts will still see friction at the piston and upper strut bushing. Don't imagine it will be a problem to run them without oil since they won't be doing anything other than taking the side loads from the struts and you've eliminated all the heat from them actually damping.

Very cool idea. 

Yes, you are correct. There is friction present. It takes maybe 3-4 oz pull to make them move in my estimation. I could measure but it will not help me. I think over time it will be less. But main thing is there is no change with velocity. It took a lot of pumping to get all the oil out.

 

I made a design for a bearing loaded strut tube with a HD strut shaft (low friction). I would cost maybe $100/corner. I decided I would postpone because this is cheaper and I need to proove the concept.

Link to comment
Share on other sites

No comments on my color choices? 

 

Step by step. I have designed a measuring tool that fits to the front crossmember control arm holes. It will allow me to thrust align the rear wheels to the chassis. Then at a later date I will align front with rear and set toe. I spent many a nights thinking about this and studying alignment methods and machines. If both front and rear control arms have adjustable toe and adjustable length, and you want symetric, then there is no fixed reference other than suspension pick up points. I will post pics when available. 

Link to comment
Share on other sites

I am quite proud of this little tool. I did a dry run tonight and it looks like it works. The 3d printed brackets have pins that slide into the front control arm holes. The 24x1" scale is really just there to keep everything square. The 60x2" scale slides through the brackets and is aligned to center of chassis by the marker pins in the bracket. 23.5 between holes. I installed cast iron rotors on the rear and measure to the rear control arm bolt to adjust control arm length even on both sides with zero camber. Then will use a line laser to the the front scale to set rear toe to zero and verify the left and right CA lengths are the same. 

That should ensure rear is aligned with chassis and later, much later, I can thrust align front to rear.  I'm not sure all this is necessary, but with double adjustable control arms Front and rear, it sure seems easy to get the track and toe uneven left to right and have the chassis tracking sideways. I ran these rear control arms on another car and first thing I found were the lengths were different even though the rod end stick out looked the same.

20220711_194228.jpg

20220711_194237.jpg

20220711_194243.jpg

20220711_194313.jpg

Link to comment
Share on other sites

I found I needed to change the rear toe-link design from left-right threads to using different thread pitches as it was super sensitive when adjusting.  I planned for but never made it far enough to change this all over to shims.  I wanted a faster at the track way to make changes that didn't involve needing a lot of precision and had to be repeatable.  I noticed most of the pro teams and car designs from 2000 on starting using that method instead of left-right threads.

 

Your 3D printed tool reminds me of the flag alignment system I've seen some of the formula car guys use.  It mounts over the top of the chassis and uses that to establish center.   Measure camber, caster, track this way.  Flip 90 degrees and measure toe.  Much quicker than strings to setup and make adjustments.

  • Like 1
Link to comment
Share on other sites

Now you tell me!. Just kidding. I have been running this design for years and never noticed it before, but yes adjusters are super sensitive.  A full turn is probably over 1" of toe change or more.  If I ever make some more rear arms, I will definitely address this. 

 

This exercise has been very beneficial so far.  I found I had the wrong springs installed, interference with the helper springs, and L/R cambers uneven due to stack height of the hats/bearings.  All corrected yesterday.  In the end, I have exactly 1mm wider track on passenger side than driver's side, but stub axles are not fully torqued down and that is location of the error.  Rear set to 0 camber, 0 toe nominally to start and "centered" to chassis.  I am satisfied with the rear.

 

I have another idea that has been baking in my head for a couple years.  I want to fab a hub mounted alignment system that also incorporates scales for corner weighting.  I don't know why no one had done this before.  Heavy duty inline load cells are $50-100 and a digital read out/load cell amplifier/programmer is less than $10. It would need to have a leveling mechanism (laser reference) and ablity to slide a little so camber can be adjusted.  Lasers are also super cheap.

 

 

Link to comment
Share on other sites

  • 4 weeks later...

Let's get a update in. I had a damn sinus infection which slowed me down for a couple weeks, but I'm still chugging along.

 

After the rear alignment I dropped it off the rotisserie onto jackstands. Spent a couple hours planning out the final welding push up front. I've got to mount a radiator, oil cooler, along with G-nose braces and air dam braces. Along with shroud for radiator and pulling cool air for the engine and brakes. Quite a bit of packaging. 

 

The good news is I got the front sway bar all worked out. It was a leap of faith that everything would clear.

20220810_210137.jpg

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...