The point of this series is to show how we plan to build some nice Roadside Designs bicycles and frames.
All the info i'm putting up here will be OPEN SOURCE - email me if you want any drawings to technical knowledge, i'd be happy to oblige. Unless its personal or difficult to explain, everything in the following series of posts should be information enough on how to manufacture your own singlespeed/fixie frame!
1) Materials
Bicycle frames are usually made from 4 common materials - steel, aluminium, titanium or carbon. More exotig materials are available, but difficult to source and difficult to manufacture with. Shortlist:
- steel: heavy yet very strong. since thin walled tubes are difficult to acquire in Estonia, I will steer clear
- aluminium: 3x lighter than steel, stiff but prone to strain induced cracks. at same strenght, it is 35-40% lighter than steel (my material of choice)
- titanium: 2x lighter than steel, very stiff, very strong. difficult to source materials and very tricky to weld. will stay away right now
- carbon: 3-5x lighter than steel, extremely stiff, does not like scratches or dings. can be produced, but needs specialized tools, which are difficult to acquire. will stay away, but considering for future purposes.
I'm setteling with aluminium alloy, 6063-T6 and 6082-T6, because a good supply is available and its highly weldable and relatively easily machineable. It has very good material properties and nice tube sizes.
A quick pic of a frame I designed for a friend:
2) Welding
Bicycle frames are usually welded, brazed or bonded. Welding works well with steel, titanium and aluminium, bonding with carbon and if you have a flare for nostalgia and beautiful and hidden welds, then brazing is the way to go for steel.
Welding has 2 main subtypes used with steel/aluminium/titanium - TIG(tungsten inert gas) and MIG ( metal inert gas). MIG welding is done with an automatic filler rod feed(think robots), TIG welding is done by hand, and filler added as needed(MIG can also be done very well by hand, but welding round tubes with MIG welders is best done with robots).
TIG welding produces very nice welds with a wide weld pool - ensuring good quality of the frame(for example, an aluminium frame can have a 5mm wide weld pool, while titanium frames have used 2mm and less).
Welding 6000 series aluminium yields usually very good results and thusfar has not produced any frames that have cracked(thanks to the good welders too).
3) Tube sizes
When looking for tubes, its generally a good idea to scout out what the importer has to offer. First - to get the lightest yet stiffest frame possible, second - to make sure that your bottom bracket threads and headset cups fit nicely. If you can get your hands on some oval/elliptical tubes, then go for it, at the very moment i'm limited to completely circular tubes. Or rectangular.
General sizes:
Headtube/bottom bracket - 34mm inner diameter, 2-3mm wall thickness(for inches, its 1.34 inner diameter, and 0.075-0.100 inch wall thickness)
Toptube/downtube - anything starting from 30mm up to 45mm, wall thickness 1.5-2.0mm(for inches, its 1.2 to 1.75 inches for outer diameter with 0.060 to 0.075 wall thickness.
Chainstays - between 16 and 22mm, wall thickness generally 1.5mm(or 1.0mm if you are feeling adventurous. For inches, thats between 0.6 and 0.85, with a wall thickness of 0.060 inches.
4) Welding jig
A picture is worth a thousand words :).
More information regarding the project will come in a short while, probably on the 24th or 25th, depending how much food I consume.
Happy holidays :)
I was trying to overhaul a headset that was somewhat oval.I thought it was a defect I didn't know they made them like that.
ReplyDeleteHey mister, generally headtubes aren't oval - if you took your headset off and saw some ovalling, that means the frame has elongated slightly.
ReplyDeleteIf you can find a machining shop that can clear the ovalling and make you a small shim, then do that, because after some time the headset will start creaking and flexing and can break the frame.