Hi guys, I'm a studying mechanical engineer from Adelaide Australia. I'm looking at making my first aluminium bike frame and have a heap of questions. To start with can I just use off the shelf aluminium from a supplier? And what's the best way to make chain stays as they are probably the most complex part. I'm designing the bike on CAD first and starting with single speed for my first one to see how I go and I'll move on from there. Any other advice?

Engineer in the British sense or the American sense? I know a machinist from Scotland that calls himself an engineer. Caused me all sorts of confusion at first. He's only lived here for 20 years, I imagine he just does it out of stubbornness.

First off, I'm no expert, so most of this is just stuff I've picked up on forums. There aren't a lot of framebuilders left that build with aluminum. There are aluminum alloys that can be used after welding without heat treating (6005 maybe?), but I think they have fallen out of favor. So that's a downside. There are still aluminum bicycle frame tubes available for purchase. That's probably the best place to start if they meet your needs. Alibaba maybe? Chain stays are often made from straight tubes and bent/crimped. Very common on custom mountain bikes. You should be able to get a drawing of your cranks, that's where the real problems are if you are using fairly narrow tires.

I suggest drawing your bike in a 3d parametric cad program such as solidworks if it is available. I'm trying out Fusion 360.

Steel is so much easier to start with. I'm not sure how good of a welder you are, but the typical mechanical engineering student isn't much of a welder. Unless you are a machining student, in which case it is still probably true, only less so.

I know a builder that usually uses Ti. I asked him why he doesn't build in aluminum, and his reasoning is that Kinesis frames can be imported into the U.S. for about $25. And he didn't want to compete with someone that was selling frames for 1/6 of what he can buy tubes for. Ti is about the same difficulty and doesn't have to be heat treated, so that's what most custom builders use.

I'm not sure who produces Nova's aluminum tube sets. I assume it is Deda, but that's based on unreliable rumors.
https://www.cycle-frames.com/bicycle-...INUM-TUBESETS/
I assume they will ship.

Welding leaves conflicting stresses , so once welded there is a solution heat treatment,

annealing and melting is not far apart in degrees ..

Frame is alignment jigged in the oven ..

in the 80's early Cannondale frames were delivered straight, but some of them had wavy tubes
from when they were soft during the normalizing heat treatment

Back then there was Vitus and AlAn out of France and Italy,, they were assembled by epoxy bonding the tubes to the other parts..

AlAn used a tapered thread , and before the epoxy cured the tubes were rotated,
(RH thread on one end LH on the other, like a tutnbuckle) so the tubes pulled the 'Lugs' over them..

Now Aluminum Tubes are Hydroformed into force & style, determined shapes with ends prepared to be ready for welding..


Think about a Trip to Taipei, & Taiwan in general, there is the biggest concentration of bike industry companies on the globe.

Adelaide Australia, is a lot closer than I am.

...

Thanks for your help, pretty much put aluminium out of the question. Might start with a steel lug build and then go from there. The issue with Ti is that with the welding process it doesn't react well to oxygen so you usually have to create a atmosphere around it with neon gas to get a good quality weld. That's why it's more suited to smaller production and not so viable for mass production cycles and Ti isn't the cheapest.

I'm drawing it up on solidworks, I'll do a full assembly with FEA to optimise it. Try and get some weight down and see how we go. At least I can't braise and MIG weld at home and would have to outsource it.

I'm doing mechanical engineering at uni, 4th year but I don't want to be just a desk jockey and I believe if I'm asking a trades person to make something I should have some understand and knowledge of how to manufacture it myself so I try and increase my skills that way too (lathe, welding, braise, milling machine ect)

If you're going to outsource the actual fab then you builder will likely want some input on the specs. If you're doing the fab on your first I would suggest not trying to reduce weight too much. A lot of metal working skills get learned with the first few frames. Learning requires making mistakes IMO. Using tubes with thick walls allows for these to happen with less consequence. Andy

Any sort of metal tubing you'd want to weld a frame out of is going to require inert gas welding, not just Ti.

Your best bet is TIG'ing a steel tubeset. Lugs are great, but restricting in angles and connection points.

I find aluminum welding is always a big pain.

6061 tubing should be generally weld tolerant. Some fillers are designed for heat treating, others are designed to use as-is without heat treating, but you will lose some strength if you don't heat treat.

7005 is a bit stronger, and will allow for a lighter frame, but 6061 is still a commonly used metal.

You can purchase ready to weld aluminum tubes and small parts.

TUBES ALUMINUM :: Nova Cycles Supply Inc.
ALUMINUM TUBESETS :: TUBE SETS :: Nova Cycles Supply Inc.

Probably quite a few other suppliers too.

If you're building a standard triangle frame aluminum frame, then it might be good to start with a tube set. Go with your own if you're doing something very custom like a cargo bike.

However, some cargo bike builders will also look for good donor bikes for things like forks and rear triangles.