Frame design

rockmonkeysc

I have been thinking about designing & building my own hardtail frame. I have access to 3d CAD with stress analysis & an AC TIG welder (and the experience to use both properly) and a manual lathe & mill. Where can I find some good info on frame geometry & loadings?
Is it possible to get aluminium extrusions for the frame? or will I have to be clever with tube & sheet?

joshtp

start of with steel, use a good 4130 chromoly and get some practice. its so much easyer than alu. make a simple rigid or short travel HT and get the bb shell and headtube, and seat tube from bike tubing specialists, save the hasstle. make it out of stock, non buttet tubes, and overbuild to counter mistakes.... if all goes well, then get creative. for your first one make it cheap, simple, and sturdy. check out MTBR forums frame building section for tips.


but mostly, KEEP IT SIMPLE!

for Geo ideas, think of a frame you would like it too be similar too, say the on-one inbred, and take the geometry from that as a base, maybe slacken or steepen the HA by half a deg, nothing too drastic, you want it to ride well afterall... and make lots of calculations and checks before you start. so draw up the frame with the geo set around the AC of the fork you want to use, and with the axels at the same level, draw the wheels in and the bb, and the headtube, then work the frame into those points.. the bb, headtube, and dropouts.



remember also that complex joints and clever dropouts may lookawsome, and work fantasticly, but pullingtheof is hard, it will require lots of work, and time, and money.



but have fun, and i hope it works out... im half way through a custom buil long travel HT for a totaly awsome, but top secret amazing beast bike... although i have many, many cleaver uni boffins, and pro welders helping me out.... so i know how you feel, but try not to get carried away...

rockmonkeysc

Thanks for the advice.
I work in a design office & have very little to do at the moment so might start playing around with some wire frames to work out a nice design.
Steel might not be a bad idea, easy to make it look nice.

mmacavity

For steel, aluminium and titanium tubing:
http://reynoldstechnology.biz/assets/pd ... s_list.pdf

for frame fittings:
http://www.ceeway.com/

for ideas on tooling/ fixtures:
youtube
or Anvilbikes

to build a steel frame consider a Dave Yates course:

http://www.daveyatescycles.co.uk/

further info:
http://www.nimbuscycles.co.uk/Welding_Notes.pdf

hoochylala

Found this in the Tech F&Q - maybe of use;

http://www.littlefishbicycles.com/frame/

nicklouse

RockmonkeySC wrote:

I have been thinking about designing & building my own hardtail frame. I have access to 3d CAD with stress analysis & an AC TIG welder (and the experience to use both properly) and a manual lathe & mill. Where can I find some good info on frame geometry & loadings?
Is it possible to get aluminium extrusions for the frame? or will I have to be clever with tube & sheet?

first decide what you want the bike to do and then see what numbers makers are using.


then when you have decided on a material find what sizes are available for frames as they are rather limited.

mmacavity

To gather useful / useable data for stress analysis takes time and complex analysis. Frame tubes are often as thin as Euler's failure/ buckling allows.