Old School Chopper Frame Fabrication
from http://220.127.116.11/neatstuff/ Part 1 The easiest frame to build is a traditional old school styled chopper since there aren’t any complicated bends or compound miters to cut so we decided to show the chassis fabrication process from A to Z as we do it. Others probably have different techniques but this systemhas worked for us over the past thirty years and guarantees a good straight frame using a minimum of special tools or really fancy jigs. About half of the frame is constructed without a traditional building jig being used to begin with so this is a good project to start with if you want to build a traditional frame jig but you don’t have a frame to use as a mock-up. As work progresses on the chassisyou can fabricate a jig one piece at a time when it’s needed. The frame for this particular project is derived from the stock 1948 Harley hardtail design but we stretched the downtubes four inches, the backbone two inches and raised the rear axle plates plates one inch and shifted them two inches rearward. These changes result in a lower than stock frame having a perfectly straight backbone linefrom the steering neck to the rear axle when viewed from the side for the classic chopper look. These instructions are intended to accompany part of the material that we provide with our large-scale building plans. This is the first time that we have published them separately and while we have tried to modify the diagrams and exhibits to fit into the size limitations imposed by a web page some ofthe pictures may be to small to be readable. If you don't have our plans and you reach a stumbling block on your project please contact us and we'll see if we can help you out. The frame we're building for this particular project will accept Panhead, Shovel and Evo engines and Knuckleheads and Flatheads with a front motor mount spacer. It's designed to use a 140 or 150 rear tire with standardchain. Our goal for this particular project is to have a rolling chassis for under $1500 or about $6000 less than if we bought one ready-made. To start with you need thirty feet of 1.25”x.120” ERW tubing. We’d suggest that you buy two full twenty-foot lengths since this will give you some extra material in case you make a few miscalculated cuts or bends. You’ll also need two feet of 1x2x.120rectangular steel tube for cross members. To start the project you won’t need a steering neck or axle plates until further down the line so you can get this frame started with very little upfront cash outlay. After you’ve secured the tubing you can cut it into working lengths using an abrasive cutoff saw if you have one otherwise use a sawsall or even a small tubing cutter. As a last resort a regular oldhacksaw will get the job done but will eat up a good chunk of time and give you some nasty blisters. Figure 1 illustrates the primary chassis components of a typical VTwin rigid frame that consists of the following primary elements:
1. 2. 3. 4. 5. 6. 7. 8. 9.
Steering head. Also called the stem head, steering neck or headstock. Frame Backbone. Sometimes called the Top-tube. Seat post.Backbone or Top Tube brace. Wishbones. One left and one right. Also called the upper rear wishbones. Wishbone cross member. Also called the upper fender mount. Side tubes. Sometimes called the side rails, bottom rails or lower tubes Seat post cross member. Rear transmission mount/cross member.
10. Axle plates or side plates. 11. Front tubes or Down tubes which extend into the bottom rails 12. Fronttransmission mount. 13. Rear motor mount. 14. Front motor mount 15. Motor top mount. The following table lists the pieces to be cut, the length and the quantity. Allowance has already been factored in to account for the bend lengths and to permit some room for possible cutting mistakes.
Quantity 1 2 1 1 1 2 2
Item Backbone Wishbones Wishbone Cross member Seat Post Seat Post Cross member...