How to use FEA in bicycle design?

[chocobanana]

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!

 

[GregLocock]

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.

 

[chocobanana]

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!

 

[IRstuff]

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

 

[chocobanana]

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

 

[corus]

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

 

[MadMango]

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.

[green]"Art without engineering is dreaming; Engineering without art is calculating."[/green]
Steven K. Roberts, Technomad
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[chocobanana]

Hi

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

Thanks

 

[Heckler]

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
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[amorrison]

See forum664