Carl,
My 1st bike weight in at 35-36#. Maybe because I bought a EZ1 seat
(about 10#).
2nd bike with 0.035 Thickness 4130 came in at 28# but has some flex
I'm working on fixing (my own design so that could be the reason)
3rd bike (simular to 1st) I'm building is using 0.035 thickness 4130
steel. However, I'm not using a sliding boom for the bottom bracket.
From my calulations for 4130 0.035 thickness for main tube stress is
about 1/3 of yeild strength so plenty strong enough. The weakest part
is the chainstays. I've used 0.069 thick 7/8 and 3/4 OD tubes.
If you're using a sliding boom the thinner wall could make it hard to
clamp down on it.
Hope this helps.
Bob
--- In bentechriders@yahoogroups.com, Carl@v... wrote:
>
>
> Hello Group,
> I just ordered a set of plans and had a question.
> In the "FAQ" section on the main web page it states:
>
> "A lighter frame can be achieved if thinner chromoly main frame
tube
> and an aluminum seat frame are employed. You will find that a
> homebuilt frame can be made as light as commercial recumbents
costing
> thousands of dollars more."
>
> How thin can one go and still retain sufficient strength and
stifness?
> Has anyone gone with a thinner main frame?
> Thanks,
> Carl