Recumbent - Considering Titanium to homebuild a recumbent trike, Tadpole or Greenspeed design
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03-31-06, 02:32 PM
1) Any advice other than the fact that Ti is hard to weld and expensive?
2) Any design adjustments I'll need to take into account?
3) What will the estimated frame weight be? Best guess!
I am a newbie to bents and actually ride standard geometry, but my wife needs recumbent due to Arthritis in the spine, and a trike due to only 1 inner ear due to tumor removal. Bents are comfortable, but I'm just more secure, myself, on standard geometry! The intent is to build her a touring trike to ride with me.
1) Any advice other than the fact that Ti is hard to weld and expensive? Titanium is as easy to TIG weld as mild steel, but can be v-e-r-y expensive if the man (or woman) on the torch, deviates from strict guidelines. Absents of impeccable cleanliness is unforgiving - even a single fingerprint from a washed hand can induce joint failure. From beginning to end, any and all tools which have porous surfaces (i.e. grinding wheels, files, etc) which were once used for steel, should never be used to prep titanium. And, titanium is brutal on tooling, so expect to purchase a fare amount of quality bits and cutters. Also, thin walled ti tubes require back-purging - another necessary hassle.
2) Any design adjustments I'll need to take into account?Impossible to accurately answer without seeing the lay-out and parameters of the desired design.
3) What will the estimated frame weight be? Best guess!Ti typically weights 2/3 that of steel, but unfornunately, isn't as strong. So, don't expect much, if any reduction in weight - and some titanium designs end-up weighting more.
Yeah, you might be better to stick with cro-mo steel or 7005 aluminum...
You can Tig titanium, but it's expensive and as PaPa says, its unforgiving. I'd advise 4130 thin walled steel tubing which you can easily get from any aircraft supply company.
04-04-06, 09:23 PM
Agreed, for the homebuilder it's hard to beat chromo. It doesn't have the cachet that Ti does, but a lot easier to work with and makes into strong, reasonably light frames.
04-05-06, 09:15 PM
If you don't think you want to build a frame, try this guy. www.tetcycles.com/index.html
I've seen one of his tandem trikes, it was awesome!
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