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Extending a home-made recumbent... suggestions?

Posted: Tue Jun 26, 2012 5:04 pm
by James the Giant
I just bought this home-made recumbent on Gumtree for $50. Score!

Image
Bigger picture and other pics of the bike available here
It's very sturdy, well put together, comfortable to ride, except it's far too short for my long legs. So I need to extend the pedal assembly... whaddya call it, (chainset?) a good 30cm or so.
You can see from the close-up photo that the chainset has a tube which slides over an aluminum tube welded to the frame, and it bolts together with two bolts. It's sturdy enough.
But if I extend it 30cm with scavenged cut-up frame-tubes from other bikes, I think it might flex and bend too much. There would be quite a bit of leverage on the end of a long pole.
What say ye? Is there a better way?
Apart from getting someone to weld a longer stronger bit... I'm too scottish for that at the moment.
Image
Bigger picture here

Oh, and hello! I'm James, from New Zealand. I have just arrived in Australia from New Zealand, and I must say I am impressed by the courtesy most Aussie drivers show to cyclists. On suburban roads they pass you quite wide, whereas in NZ they seem to think nothing of whizzing past seemingly just inches away.
I've been here in Fremantle for 3 weeks, and somehow I seem to own three bikes already. Hmm... this a bad habit I think.

Re: Extending a home-made recumbent... suggestions?

Posted: Tue Jun 26, 2012 8:13 pm
by just4tehhalibut
It does look like you haven't got enough of that welded on aluminium boom to play with, just sliding a longer crank tube (what else are we going to call it?) over the alum boom is going to give you flex and possibly failure where those holes have been drilled in the alum boom. I was thinking of a smaller tube inside the alum boom as a stiffener, using a CrMo tube for the crank tube, kicking around a few ideas but in the long run whatever solution will probably involve some welding. Do you know anyone who can weld? After all, even if you find a suitable donir frame for a new crank tube you'll still have to mess around for the front deraileur mount and as you can see the previous owner had to weld something on too.

Re: Extending a home-made recumbent... suggestions?

Posted: Thu Jun 28, 2012 9:47 am
by Poiter
Can you do something where the rear swing arm attaches to the blue frame.
Is it welded there or bolted up as it looks in the photos.
Keeping that boom short would be a good idea given the size of the material used.

Re: Extending a home-made recumbent... suggestions?

Posted: Thu Jun 28, 2012 10:26 am
by James the Giant
The rear is bolted... hmm.. might be possible to do something there.
Eventually I might have to concede the need to spend some money, cut off the existing small tube at the front, and get someone to weld on a big, thick tube which will take the strain.

Re: Extending a home-made recumbent... suggestions?

Posted: Thu Jun 28, 2012 10:20 pm
by Vimes
I've been here in Fremantle for 3 weeks, and somehow I seem to own three bikes already. Hmm... this a bad habit I think.


BLASPHEMY
Remember N+1

(N being the currant number of bikes owned)

Re: Extending a home-made recumbent... suggestions?

Posted: Fri Jun 29, 2012 2:16 pm
by John Lewis
Hi James,
As an interim measure you could probably take two strips of plywood and some bolts.
remove the front bit and use bolts to camp ply each side to the front section and main boom to extend it.

I know there were some bolt together recumbent ideas on line so perhaps have a bit of a look round for ideas.

Looking at your picture I'm sure the plywood idea would work and would look quite respectable when painted.

John

Re: Extending a home-made recumbent... suggestions?

Posted: Wed Jul 04, 2012 2:21 pm
by James the Giant
John Lewis wrote:Hi James,
As an interim measure you could probably take two strips of plywood and some bolts.
remove the front bit and use bolts to camp ply each side to the front section and main boom to extend it.

I know there were some bolt together recumbent ideas on line so perhaps have a bit of a look round for ideas.

Looking at your picture I'm sure the plywood idea would work and would look quite respectable when painted.

John

That is an excellent idea, and I have some good thick plywood on hand. Combine that with bolts and maybe some epoxy, and I think I have a winner.

Interestingly, there are lots of designs and ideas for wood recumbents, I think I may build one, looks so simple.
http://www.manytracks.com/Recumbent/RecumbentShare.htm