Question on shortening the my VW chassis

So I've decided to forgo a new tube chassis and go the "old school" route of shortening an existing VW chassis. I'm still a little unsure on the exact steps I should take if I want a completely re-vamped chassis.

The procedures I want done are as follows:

-Remove the old floor pans
-Shorten the chassis (that is to say, the torsion tube)
-Sandblast the entire chassis (again, effectively the torsion tube)
-Install new floorpans
-POR-15 the entire chassis

This is the order that I see the steps in, but I think there may be other (better) ways to do it. In my process, the torsion tube would be "alone" for a while and I'm not sure if its wise to do that without floor pans.

Thoughts?

I assume when you say torsion tube, you mean the tunnel that starts at the frame head and ends with the frame horns the engine mounts to, right? We here on the SOC generally call that the tunnel.
There's a tube transversely mounted through the tunnel which ends in two stickey-out parts 'bout the size of toilet-paper rolls -- that is generally referred to as the torsion tube.
The torsion tube contains the little bars which work against each other to provide springiness to the rear of the car, and are a key component of its suspension.

What you're describing sounds about right. You hack a chevron-shaped section a little more than a foot long out of your pans and tunnel, weld them back together and adjust the lengths of any pieces that pass through that space.
Welding it back together is next, followed by drilling any holes you need to drill, pre-fitting any modifications and then disassembling them for blasting, priming and painting with whatever materials you like. In all, it takes a little more than 20 minutes. ;)
(Mine took two years. Not a record, by any means.)
There's a tab at the top of the page for folks about to embark on a project like this -- the 'library' -- and with scores of us here to cheerlead and offer physical labor, beer-drinking consolation and general tech help, it might even be a little bit fun.

Welcome to the Madness!

I appreciate the reply.

Not to nitpick, but thats actually not the procedure I described. I would be doing the shortening of the tunnel (as you call it) without the floor pans in place. So, I wouldn't need the "chevron" I could actually just make cuts directly to the tube and then make any cuts to the new, aftermarket, floorpans (chevron or otherwise).

Is that a process you would still recommend?

If your floor boards are shot - chistle them off then cut the tunnel and shorten and add new pans when done. You might want to use fiberglass pans or even diamond plate or flat steel. No strength in the replacement OEM style pans anyhow plus you hack off the seat brackets and battery clamp anyhow. You'll want to caulk new pans in after welding and pain the seams.

Yup, little support with replacement pans, I just did a set for a street buggy build and had to add 1" x 1" square tube in the bolt channels. ~Alan

I went with box tubing and diamond plate aluminum for mine. I kind of went in my own direction with this thing.
The chevron-shaped cut is intended (I think) to increase the integrity of the pans when they're welded back together. I don't think I would want a straight, side-to-side weld; too weak for the way I treat the Hoopty.
My answer to the problem:

Have you read the chassis shortening instructions on the CMC manual available here?

Leave the pans in until you have finished the tunnel. Cut the exact same amount out of both pans so when it's shortened you have extra references points to help keep it straight. and be mindful of keeping the tunnel straight you don't want a swayback pan or a arched backbone. It causes problems with the engine setting level. especially on a VS..

It is significantly easier to shorten the central tunnel with floor pans already in there. Otherwise, you'll be screwing around for hours or days trying to figure out how to get the pans shortened separately AND make them fit the shortened tunnel.

So, remove the old floor pans and everything else you want to replace, sandblast whatever you want, then re-assemble with new, stock-length floor pans and THEN cut it in two and shorten it.

Read the CMC buld manual up in the library section. I essentially followed those directions on the kits I've built and it's always worked well (just finished shortening another one last Summer).

BTW: that process yields the same results as the shortening directions on the Manx Buggy sites. The cuts aren't precisely the same, but the difference is mice nuts.

gn

I did mine a bit differently as I need to get it past the Authorities and do not want them to see that I cut the pan. A lot more work, but results in what I believe is a stronger and prettier job

Drill out the spot welds holding the tunnell and ribbed bottom plate together so that you can separate the two. Cut the tunnell using a zig-zag pattern, removing the section from the wasp waist part of the tunnell so that when joined it is flush. You can either cut the floor section or in my case remove the entire rusted POS and build new.

Cut the ribbed bottom section shorter at the front equal to the tunnell section removed, and weld to the frame head. Strength is maintained and you cannot see the cutting process. Neat TIG welding at the tunnell cut will not show.

Will post some pics of the finished product, but got the idea here. It is the "VolksMagic" method and I made a couple more zig-zags on the tunnell section for extra strengh:
http://www.shining-wit.net/rick/buggy/design/body/#Chassis%20Shortening%20Methods

I added a new frame head, and complete new floors at the same time so a bit more complicated, but a real nice, clean job, invisible cutting, and I believe the strongest of all methods