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Home > Tech Tips > Build / Modify Frames

Chopper frames - Should I build my own?

By Pharaoh

The starting place on any custom chopper project should be the frame. And many of you thinking about building your own chopper are asking yourself one thing: Should I build my own? I'm not going to try to persuade you either way, just give you some of the things you need consider. Like many things in life, building a frame isn't as easy as it looks. Here are a few things to think about.

  1. Is The Style and Dimensions I'm Looking For Even Made?
    Today all stock frames and most aftermarket frames are mass produced. While this does lead to increased consistency (in theory anyway) and lower costs, selection sometimes takes a hit. If you're looking for a specific rake or stretch, chances are you will have to build, have built, or modify a frame. Companies like Paughco and many small shops will build you just about any frame you want, but often times the price will be a lot more than what you want. So building your own may be your best option.

  2. Do you have the tools and skills?
    If your not a good steel fabricator, don't attempt to build your own frame. Period.

    If you do have some metal working skills, the bare minimum tools you will need are:

    • Welder - I prefer to TIG weld all frames. If that isn't available, a wire feed will work - a 220V or greater is ideal. If you're using one of those 110 units, you have to make darn sure you're penetrating with your welds. But again, TIG is the best for frames.

    • Saw - Band saw, chop saw, or similiar fixed saw to cut tubing. A torch or sawzall isn't accurate enough.

    • Finishing - A grinder is darn handy, particularly if you can switch between grinding and sanding discs.

    • Handtools

    • Frame Jig - if you don't have one but DO have the above tools, you can make one. You will need a long peice of round stock to set the neck, some channel or I-beam to mount everything to, and some angle for braces. We'll talk more about this in a minute.

  3. Engineering Considerations
    What's rake and trail? Stretch? What does DOM mean, and how size should I use? If you don't know what I'm talking about here, you better learn before you get started. Rake and trail refer to front end/frame geometry as it relates to handling. Stretch is a loosely used term to describle how much over stock the legs (down) and backbone. DOM stands for Drawn Over Mandrel, and refers to a type of tubing commonly used for frames. Do your homework before you even think about beginning.

  4. What About Alignment?
    Do you like to have to fight your bike flop over at low speeds, wabble and vibrate at high speeds, scrub tires, and generally have it steer like you are hearding cattle? Didn't think so. But if you don't make sure key components are in alignment, that's exactly what you'll get. This is where a frame jig comes into play. Generally you will have a peice of round stock that is welded at the correct angle you want your neck, and a number of other setups to control all critical dimensions of your fabrication. You also need to make sure the axle plates are aligned correctly, or you will have handling problems or "scrub" your rear tire.

    Another big alignment issue is the motormounts, both side to side and distance apart. If they're a little off, they will make installing your driveline a nightmare. Same goes for trany mounts. I have mock-up motors and tranny's just for this purpose.

  5. Inspection, Liscensing, and Insurance
    I don't imagine you would like it too much if after you just finished your bobber masterpeice, you go to the DMV and they won't title it. Or if you go to insure it, and no one will write coverage on it. Some states are very strict laws about titling custom motorcycles, so start asking around before you begin your build. Many states require a MANUFACTURERS MSO for the frame, with legitimate numbers, and a receipt or they won't even look at it. On quick way around this is to buy a wrecked bike, and use the neck with its numbers for the frame. Another way is to use a generator shovel, panhead, or knuckle motor with title. On this vintage of bikes, the title went with the motor, not the frame. A final method is to file for a frame builders VIN system with the US department of transportation, which allows you to issue numbers and MSO for any frame you build.

    Equally important is making sure you can insure it. Most insurance companies won't insure them, period. Many companies that do will charge you an arm and a leg. So again, do your homework in your state.

So as you can see, it's not as easy as welding some tubing together and rolling down the road. For the vast majority of beginners, starting out with a stock bike and modifying it will be the easiest method. Rolling chassis are another good way to go if you are unsure of your skills. But for those that want something truly special, building your own frame is the only way to go.

And you don't have to go it alone either. The following companies offer frame building prints and technical books to help you. One of my favorites is The Chopper Builders Handbook, but there are others available as well.


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