Thread: Blueprints
View Single Post
Old 01-07-13, 09:04 AM
  #11  
ksisler
Senior Member
 
Join Date: Sep 2012
Posts: 1,739
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 25 Post(s)
Liked 2 Times in 2 Posts
Originally Posted by MassiveD
I build and design boats, that was one of a couple of root things that got me into all this making stuff thing. Bikes are different from boats, sorta. There is not a big business of plans. I have boat plans that are hundreds of pages long. Though one of my favourite builds was a small catamaran that I built for fishing, sorta a green thing. What was great about it was that I knew what I wanted, and there was only one 8.5x11 sheet of instructions, plus the hull lines, which were in a simple table. It was great because I got the plan exactly as I wanted it. No material the designer liked or had access to that would drive me crazy sourcing. Anyway, for the most part bikes are very simple, one does not need plans. essentially you need locations for the axles, the bottom bracket, a seat tube angle, and a head tube angle. The rest is pretty much connecting the dots as far as getting a bike to plan is concerned. Of course simple matters like axle position will affect one's fit to the bike. With some oversimplification, the basics are that the head tube goes where it has to go given the wheels and tires you are using (get these first); the forks you will use (many builder do not make the forks, either because they are too challenging to make, and dangerous to screw up, or because they are specialty carbon or suspension forks); and the angle you are going to have for your head tube (steal this from an existing design, or copy listed specs, it is often 73 degrees). The seat tube is usually 73 degrees and depends on your seat choice, and the body position your bike is set up for, and your seat post. Comfort bikes have outlier seat tube angles. One of the best ways to get seat post numbers is from a good bike you fit well. Given the correct posture on a bike, the seat tube relates you to the pedals, and does not vary much bike to bike, other than where odd postures are encountered, as with something like a time trial bike, or comfort bike. Once you have your two verticals laid out on paper, the rest is easy. Your BB drop relative to axle height will be a range for the type of bike you are building. Again scavenge manufacturer's catalogs, and online source. You draw in the top tube relative to torso fit needs and standover needs, you can get a number from online calculators. And the downtube, just goes where it goes. The rear stays are the biggest build challenge, but design wise, they are mechanical. They go where the drivetrain needs them to be, wheelbase determines, drop as already mentioned, etc... You just copy what is out there. The bad news in all this is that making bikes is a lot more difficult and uses a lot more expensive and weird tools that you may expect. Also, unless you are a welding expert, air aircraft or refrigiration, or pipe fitting, Tig or gas welder, you may have more of a learning curve than you imagine. I got into the whole chopper thing, and I can tell you bikes are way more difficult, frame wise.
+5 Massive for the general view; Bikes are generally rather simplistic, expecially for folks who have built a few frames. After a while a detailed plan really doesn't seem as necessary. The devil is in the details of execution though and I suspect that takes a bit longer for most.

On a humorous note; I have been quoted more than once to have said "the first recumbant bike resulted from a novice builder working from a few functional specs but no specific design or plan" while I actually did say "the first tandem, aka; the NagaCycle, probably resulted from a frame builder finally agreeing to allow his spouse to help out in the shop...and Mr Naga had no idea what he had started!"
ksisler is offline