re large chainwheel

On Mon, 10 Apr 2006 22:03:25 +0100, "geepeetee" <[email hidden]>

Quoted message said:

I have a single chainwheel from a brompton at the moment so i would be
starting from scratch. The bike has a six speed freewheel on the back and i
would just need a single on the front still.

Challenge provide 65 tooth rings as standard on a number of their
models, perhaps a Challenge dealer might be able to help. Try ringing
Bikefix (or any recumbent dealer I imagine):

http://www.bikefix.co.uk/

I think these are the people who supply Challenge:

http://www.dutchbikes.nl/bodies/onderdelen.htm#020

Looks like they deal direct too, so you could order from them.You can
see though that big rings ain't cheap.

Another alternative is to shorten (or buy shorter) crank arms, that
would increase the effective gearing. I'm currently using this kind of
set up on my 406 wheeled recumbent and it's a fun experiment. Cadence
shoots up and you can gear way down and still have an effectively
higher set of ratios available. Currently using a set of adjustable
crank shorteners at a length of about 110mm, and a standard 53 / 39
chainset. It feels like it provides as big a gear as the 65 tooth set
up I was on previously, although I've not bothered to do the maths.

Interesting project you have there, recumbent built from 50mm exhaust
pipe. Good luck!

"Bob"
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Call me Bob said:

Currently using a set of adjustable
crank shorteners at a length of about 110mm

Out of interest, where did you get them from and how much did they cost?
What's the adjustment range, and do they affect Q-factor?

About 8 months ago I replaced the 28-42-52 chainring and 170mm cranks on
my Street Machine with a 28-38-48 ring and 152mm cranks. The 170mm
cranks were too long. The 152mm cranks are too short, and the gearing
is too low. I really want to try something around 160-165mm that I can
use with the original rings, but I haven't been able to find anything
shorter than 170mm with the right BCD.

I'm starting to think that I might benefit from using longer cranks in
winter than in summer, so adjustable cranks would probably be a good
solution. I thought about using the crank adjusters made by Highpath
Engineering, but I didn't fancy the increased Q-factor. Besides which,
the facility to shorten my 170mm cranks by 20mm wouldn't be terribly
helpful:
<url:http://www.highpath.co.uk/cycles/products/specialneeds/shorteners.html>

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Danny Colyer <URL:http://www.colyer.plus.com/danny/>
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Danny Colyer said:

Quoted message said:

Currently using a set of adjustable
crank shorteners at a length of about 110mm

Out of interest, where did you get them from and how much did they cost?
What's the adjustment range, and do they affect Q-factor?

I'm using the Thorn shorteners Danny, see here:

http://www.sjscycles.com/store/vIndex.htm?item251.htm

I paid 40 odd quid for them on ebay.

The adjustment range is really quite large, what with the two possible
pedal positions and the slotted fixing points. The SJS blurb says
between 118 - 154mm but they go lower than that, down to about 98mm on
the 170mm Campg Veloce chainset I'm using. I don't think you'll
squeeze much more out at the top end though, so you're target of 160
may not be quite possible.

They do affect Q factor, significantly. They add at least 13mm each
side, plus any washers that your particular chainset might need to
ensure they run perpendicular to the BB axle. Mine needed two and so
extra Q factor is about 18mm.

They're quite an inelegant lump to have fixed to your cranks, and the
large Q factor bump is not ideal, but for me this is a temporary
arrangement. I specifically went for the Thorn shorteners over the
Highpath ones you linked to because of the greater adjustment
potential. I'm tweaking these up and down trying to find a position
that I think I'll like permanently. Once I've found it I'll have
Highpath do a proper job on a chainset for me, and I'll sell the
shorteners on.

I don't think these will be any good to you as a long term solution,
but if you think you might want to play with them for a while before I
sell them, I'm sure we could arrange that. I'm not at all sure though
how much longer I'll need them, so you may have to wait a good while.

"Bob"
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Email address is spam trapped, to reply directly remove the beverage.

Call me Bob said:

I'm using the Thorn shorteners Danny, see here:

http://www.sjscycles.com/store/vIndex.htm?item251.htm

Thanks Bob, I haven't seen those before. They look more practical than
the Highpath ones, but I think you're right that they won't be a lot of
use to me.

Quoted message said:

I don't think these will be any good to you as a long term solution,
but if you think you might want to play with them for a while before I
sell them, I'm sure we could arrange that.

Thanks for the offer, but I think I'll just keep looking out for a set
of cranks of the right length.

--
Danny Colyer <URL:http://www.colyer.plus.com/danny/>
Subscribe to PlusNet <URL:http://www.colyer.plus.com/referral/>
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