GP800, were you able to stretch and shrink the warping out of the tunnel skin? Done correctly, the tunnel should be and look straight.
Zollinger Tube Chassis Restoration
- Thread starter gp800
- Start date
I haven't tried much myself. I did take it to a guy who owns a body shop who I believe could fix it but he did not have any interest in taking on the job. Right now The thought is rebuilding the tunnel skin.
Watch some YouTube, buy a body hammer and dolly set from harbor freight, get a map gas torch (or use an oxyacetalene torch if you got one), and give it a shot. You can get there if you practice a little bit. The basic idea to shrinking is to heat up the bubble/excess material in the metal sheet until it is very hot, then place a cold wet rag right on the expanded part of the bubble, shrinking the bubble. The greater the excess, the more heat you need for greater shrinking. Shrinking will pull most of the warp out. Then use the hammers and dollys to offest/reverse small warps in the material until the tunnel is near flat. Repeat as needed until you get all the warps out. Stretching occurs with the hammer and dolly. To moderate your progress, feel the metal surface with your hand. When you feel bumps, then shrink and stretch as needed.
Much better outcome. Shad obviously has more experience with thin sheet aluminum. Those welds look much more consistent and clean.
Shad is very good at what he does. I did talk with him about the tunnel skin briefly, On the clutch covers the perimeter (.090) is more than double the thickness of the face (.040) which helps in managing the heat to prevent warping. On the tunnel skin the entire part was .040 so he was a little wary of taking on the project. I think if we do it again I will invest in cleco pins and have the skin "mounted" in the chassis to help it from moving around.
The heat and quench method works minimally well on steel.
Aluminum turns into weak garbage if you water quench.
That's what I've come to find just looking around. Sounds like hammer and dolley will work harden it as well. Where it isn't Structural I'm not overly concerned with strength I just want the nicest looking part that can be achieved.
I used quenching to straighten a tunnel cooler after welding. It never had an issue taking the beating. It was made from 6061 100 thou material. 040 is too thin. Try 065. That is what most CR tunnels are made from. If there needs to be more rigidity, then use 080. Also think about separating into pieces that can rivet together. That will save some warping and you can rivet in 065 (or 040) into 080.
Any new updates on the tunnel?
Summer plans?
Yes, I've still been slowly plugging away at this build. all of the material is cut out for the new tunnel and the rear cap section has been bead rolled again. This time around the tunnel skin is 3 main pieces rather than a solid bent channel with holes cut into it for the taper. While this means slightly more welding I believe it will allow for a much tighter fit, especially in the upper corners. The plan is to fit all 3 panels into the chassis and then weld them while in place. I have talked to a friend who has a high frequency machine which should allow for better heat control. I did also pickup the seat from upholstery a few weeks back. In other news, I've started a Facebook page that is focused on similar content and builds that I am working on. https://www.facebook.com/profile.php?id=100087845196952
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Quick update to help with the summertime slowness here. The chassis and tunnel have been away being welded but I’ve still managed to get a few small things done in the meantime. Before taking the tunnel down I measured and drew up a quick blueprint for the front tunnel enclosure and verified fitment with CAD. (cardboard aided design)These were originally stainless steel to protect against flying traction screws. I had a local shop bend it up along with the pocket for the steering post. With any luck I’ll be able to fit and finalize soon. I also had a friend who operates a polishing business try out his skills on a clutch cover. 
Did you get the tunnel cap finished this summer? The clutch cover looks great all polished up.
I got an update that he started on it back on 9/5/23 he was having some trouble with the arc wanting to wander due to the waterjet cut edges so he took a break.
That is likely not the problem. How the edge is cut doesn't affect arc stability so long as the cut is clean. A waterjet is definitely a clean cut on aluminum sheet. You could try laser cutting to get a different edge resolution. My experience has always been that arc instability happens because of the type of tungsten used, the wrong gas mix, or running out of gas coverage when the bottle is empty. He may have been given the wrong bottle from the gas company. If it is a co2 mix, then game over. E3 or 2% ceriated tungsten is the way to go if he isn't using those already. I get similar results with both, but I prefer E3 on 6061 aluminum.
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