I've seen a lot of guys zee frames...some do more work than is necessary, some struggle, some do it un-necessarily for the look they're after. And usually, IMHO, it's just not necessary to Z the front of a frame. Between dropped axles and the old suicide type spring perch, you can get a LOT of front end drop. However, sometimes there's a good reason to Z the front rails. Here's how to do both ends quickly and painlessly. With slight modifications, this method will work for virtually any ladder-style frame. If you're careful the frame ends up SQUARE, and the wheelbase doesn't change.
This chopped '32 gluebomb body on stock Revell rails is going to need the rear Z'd, and we're going to do the front at the same time. The procedure is basically the same. It's usually a good idea to plan where your Z will start, and this one in front is going to start exactly at the firewall. In a real car, this is really the best place. It's easiest to use this particular technique if you make the Z where the top and bottom of the rails are parallel.
The cuts for the Zeees will be the DIAGONAL lines. The vertical lines are for reference, and show where the Z starts relative to the body. I use a very fine Sharpie for the lines.
Transfer your cut and reference lines across both the top and bottom of the chassis. Make SURE everything is square at this point. If your lines get nasty, you can clean them off with isopropyl alcohol and start over.
At the rear, extend your cut lines up the floor sides and across the top. Make SURE your cut and reference lines are SQUARE and ACCURATE. Cut lines are the DIAGONALS.
Make your cuts with a razor saw. Cut across the top of the rear floor first, keeping the saw square across the floor and not going down into the rails. When you're just barely through the floor, CAREFULLY make your DIAGONAL cuts. Take a file and TAPER the sides of the rear floor towards the rear of the car, as shown, for clearance. Cut the front rails the same way, leaving the crossmember in place to keep everything aligned.
Remember those reference lines? Glue your cut sections DIRECTLY ABOVE where they used to be. Make sure your diagonal lines are PARALLEL as you glue everything back together. Check everything for squareness from the top. You'll see that because we cut the rails on the diagonal and placed the cut ends directly above their original locations, the chassis is exactly the same length as it was, so the wheelbase ( distance between axle center-lines ) is the same. This technique gives you a QUICK and ACCURATE Z that's the depth of the frame at the point you cut it, and it avoids all the monkey-motion of making vertical pieces, etc, and the headaches of keeping all those pieces aligned.
Here's the chopped '32 shell on the newly Zeeed rails. Front Z starts nicely at the firewall, keeps the kinks out from under the engine, and out of the interior. It also works well to start the front Z inside the car behind the firewall, which gives straight rails AHEAD of the firewall. You will have to modify the firewall and the floors more with that approach. The rear has plenty Z for a fair amount of drop, about 6+ scale inches. Rear rails can also be Ceeed (cutting a C-shaped notch in the bottom of the frame rail for a little more clearance for the axle) over the rear axle if a little more lowering is wanted. Combine the front Z with a dropped axle or a suicide mount, and you can get the rails on the ground under the body shell. If you want even more drop in the rear, you'll have to use vertical spacer pieces between the cut rail ends and the original rails. Or, with a little judicious adjusting of the angles at the glue joints, you can get a little more drop without screwing up the overall length and wheelbase.
How you reinforce the glue-joints is up to you. My method is to thin the rails at the joint by about .020" on both sides, and add two plies of fine RC model airplane fiberglass and slow-cure eopxy. When cured, I file the sides of the frame to the original width. No goofy looking lumps of styrene, no breaking during subsequent handling.
You can get pretty radical with this simple Z . This is that same frame with a dropped axle under the stock front cross-member, but a suicide mount would put the rails on the deck. The channeled '32 tub is the old Switchers version.
Edited by Ace-Garageguy, 13 February 2013 - 05:44 AM.