Frame building

[Mathius]

Hi all. I'm not new to metal working, I'm a certified, TIG, MIG, and stick welder, but I've never done any work on a motorcycle before. I would like to try building a motorcycle, doing most of the fabrication myself. I first thought to buy a parts bike and make the necessary modifications to get the look I desire, but I'm not sure this is the best way to go as most of the bikes I've seen have a smaller (length-wise) frame than what I would like.

Once I have chosen the motor, tranny, and tires sizes I desire, what is the best way to decide the proper lengths I need to make a frame that not only looks good, but drives well. Can someone give me some tips on planning this out? Where does one get started?

Mathius

[Prostreet]

Hi Mathius
Welcome to Metal Meet . Im sure you will find plenty of info here . I my self have no imput here as i have never built a bike but i have read some of the threads on them . Tin man Boogie man Envy and a host of others (sorry could not remember all of them) and like some will tell safety first . Good luck you have come to the right place .
Steve.

Safety DEFINITELY comes first! As for getting the dimensions you want for a frame, one of the best methods I've found is as follows.

1. Find something to sit on, roughly the height of the seat you want on your bike.

2. Sit on this and stretch your arms and legs out to where you feel like they'd be at a comfortable riding position.

3. Have a partner help you take measurements from this, and incorporate those ideas into a frame design.

I have a set of plans in my member gallery of a mini chopper frame design I drew up that you may be able to adapt into a full-sized design. It's fairly easy to change the measurements or design cues to suit your needs and artistic vision. To make the bike a full-sizer as is, I think the only thing that would be necessary would be to increase the OD of the tubing, as this design was based on 1" DOM, which would be a little small for a full sized bike. As for how to make it drive well, the most important measurements to keep in mind are rake and trail, ESPECIALLY trail. An improper trail measurement can make the bike unstable and dangerous in the extreme. If you have any questions, don't hesitate to ask them, and we'll answer them as quickly as we can.

~Adam

P.S. - Keep in mind that there is A LOT of red tape involved in registering and/or titling a home built motorcycle. this can be a real pain in the @$$, so you might want to keep this in mind while thinking about your project. It may be easier and cheaper to buy a frame from a licensed manufacturer, which will come with an MSO to aid in titling.

[Boogiemanz1]

Envy is certainly correct.. another thing that needs to be added in the legality area is that the builder of the frame is always responsible for it. If you sell the bike and someone has an accident on it, you are in the line of fire. No one will take responsibility for their own actions anymore. They would rather get a lawyer and sue everyone. Of course you can somewhat protect yourself by incorporating or other maneuvers.

A jig is important to get things correct. Changing anything changes everything. If you build a proper jig to maintain things like motormounts, engine clearance, rear wheel spacing, and neck angle, once set, you can change everything else without too much problem. It gives you a dimension that you can build to and makes keeping everything aligned much easier.

Building a jig is usually as much work or more as building a bike. It will make all the difference in the finished product.

Having a decent bender is a great help. Remember that tubing size is measured on OD and pipe is measured ID. That is why a pipe bender is not appropriate for motorcycle work unless you can get tubing dies for it.

The flat plate parts are easily designed and cut. For people challenged with a torch, a flame cutter shop will do it for a few dollars. Making mounts that the tube goes through allows you to weld 360 degrees and not create stresses.

Neck for the frame should be turned out of something compatable with your tubing for welding. 4130 is NOT a good material for a street driven bike.

These are general statements from my experience only. Good luck.............john

Mathius

There are companies out there that will build a frame to your specific dimensions.


Troy

[Mathius]

Originally Posted by Troy

Mathius

There are companies out there that will build a frame to your specific dimensions.


Troy

... which would be more expensive, and not give the satisfaction of building it yourself.


Does anyone have any pictures of a good jig?

I hadn't thought about the legalities of titling a home built bike. Modifying an existing bike would make building a jig easier, and finding the proper ride height easier as well.

Envy: I had thought about the ride height, and I find your suggestions to be very practical. I watch American Choppers often and my dad will sometimes watch with me. He complains and complains about choppers, saying the front end wobbles too much and complaining about ape-hanger handle bars, etc. I maintain that I think if someone built a chopper to his platform, taking into consideration handle bars that he would be comfortable with, and finding a way to strengthen the front forks to prevent wobble, then he would enjoy it.

Mathius

[Boogiemanz1]

Here is a link to a good page on rake and trail.............http://www.bikernet.com/garage/kennedy.asp............and this one shows a real good adjustable jig that Daytec uses http://www.streetchopperweb.com/tech...ingstc_daytec/..............................john

Choppers also may simply not be your Dad's preferred style. Nothing wrong with that. Show him some pictures of other styles of bikes, like baggers, bobbers, flat trackers, etc. and see what he responds positively to. One of the main reasons the forks wobble on a lot of choppers (this is called fork flop) is because they have way too much positive trail. (Again, it would behoove you to read up on trail and how it affects handling.) Too much trail is generally caused by builders wanting to get their forks way out in front as far as possible and not taking handling into consideration. At this point, the bike will seem rock-solid stable at speed (almost too stable) and will be very difficult to turn, even more so than you'd think from being so long. This is where a lot of builders make a HUGE miscalculation: raked trees. These little babies can bring your trail measurement back into a safe range, but care must be taken to ensure they don't reduce trail to the point of making your bike unstable. Another mistake made with raked trees is slapping a set on a stock bike and taking it for a ride without considering how it will affect the bike. This could possibly cause a situation where the bike has a negative trail measurement, making the bike highly unstable, and putting the rider's life in severe jeaprody. Do a Google search on trail measurement, and read up as much as you can on it. If you have any more questions, don't hesitate to ask, because a cool looking ride isn't worth risking your life. I'm looking forward to what you come up with!

~Adam

P.S. - I won't even go into the American Chopper debate here, although I WILL say that they have brought choppers and motorcycles to the forefront of the public's consciousness, which is definitely a good thing, IMPO. People are more attentive of motorcycles on the road, choppers are being made safer, and bikers are both more plentiful and less shunned. All positive changes.

P.P.S. - I just scored the powertrain for my first bike project! WOOHOO! Complete and running powertrain from a 1979 Suzuki GS425 twin with a 6-speed overdrive tranny, coil, carbs, electric start with kicker backup, and even a clutch cable! All for $50, and it's only an hour's ride to pick it up! How sweet it is!

I don't know when it will show again, but on Monster Garage this past Monday they took a 2004 Harley Softtail and made it into a cust0m (using only the frame and engine from the Harley.) They showed a jig for streching the neck and the rake on a frame. Don't know if this helps at all....

[Jason93]

Like someone else said, building a good jig to make your own frame will cost you 3-5 times what your frame will easily. A good jig is essential if you want to build your own frames from scratch. Not knowing how much experience you have in bike building, I would suggest buying a frame and modifying it. You can find some really good deals on a frame then you can make a temporary jig to stretch the backbone and downtubes as well as the rake to your liking. As for the bike handling good at all speeds, that comes from the trail and if its set up properly the bike will handle good.

I suggest modifying a frame, as all the critical mounts are already in place. There is a lot more to building a bike than what you see on the Discovery Channel. Let me rephrase that, there is a lot more to building a bike that will perform like it should than what you see on tv. Too many times I have seen people who want to be the next jesse james build a bike only to have twice as much money in their bike than they should and have a bike that was not put together right from the start, and then all they have is problems.

With that said I'm sure your capable of building a bike, just be sure to plan everything ahead of time and know what your getting into if you decide to build your own frames from scratch. If you need any assistance on frame building just ask. One other thing I can not stress enough is make sure you get components that work together, there are a million companies making components out there and not all of them work well together, often its wise to find a builder who's been around for a while to help you select components. Thanks and good luck.