Greetings

I'm in the process of designing some bicycle frames and wanted to use FEA to generate better results.

Thus I wanted to ask a (apparently) simple question:
Which kind of FEA analysis should one do to optimize or check for stress areas in bicycle frames?

Thanks a lot!

What loads do you have? If you've only got static loads, do a static analysis, if you've got dynamic loads do statics + fatigue.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

Hi

I'm not sure which loads should I use. but basically we're dealing with forces coming from the wheel hubs, from the rider wheight and also lateral loads. I think that's it, correct me if I'm wrong.

Also remember that a bicycle frame is subject to variable stress, kind of like a car (holes in road, bumps, gravel pavements, etc)

Thanks!

Is this for a class?

I suggest that you instrument a real bicycle with a real
rider and see what stresses you need to worry about.

TTFN

Hi

No, this isn't for a class and I don't have any measuring equipment available, that's why I think FEA might help me in the project. Still, I know that there are many bicycle companies that use FEA to develop their frames, and I just wanted to know what kind of FEA analysis they do.

Thanks

As has been said the loads are variable and as such I'd consider fatigue as being the most damaging factor. I'd first do a simple beam model of the frame to size the components and then do a detailed 3D shell model (assuming thin tubular sections) to assess the welded joints. Not knowing the loads or the frequencies and range would be a problem but you could just consider the static load factored by 2 (say) for dynamic effects and assess for 2 million cycles. Excuse the pun.

corus

What type of bicycle frames are we talking about?  Road bikes and mountain bikes will see different loading and uses/users as say tricycles and racing bikes.  You have to know what you are simulating before you can use that FEA data for anything useful.

"Art without engineering is dreaming; Engineering without art is calculating."
Steven K. Roberts, Technomad
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

Hi

It's for a cruising bicycle, but I want to take into account some ocasional abuse.

Thanks

This sounds like the dog chasing his tail syndrome.  You want to use FEA to simulate real world loads yet you don't know what the real world loads are!  I can tell you from first hand experience build a prototype of your design. Then do what IRstuff suggests.....instrument the frame and set up some load case testing.  This will give you a starting point for optmization.  If you have the fortitude you can apply some physics and resolve the reaction forces a typical frame might see.

Their are many frame builders in the bike industry that just build frames off the cuff....and it shows in the final outcome.  I would also suggest taking a frame building class.  I've seen them offered by local frame builders.

Best Regards,

Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NVIDIA Quadro FX 1400
      o
  _`\(,_
(_)/ (_)

Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

See forum664