Armless chainwheel.

[fruitcake]

I want a spider (and at least two chainrings) without an arm. 

Am posting this in the darkside because I know they exist for recumbent bikes, like this one
Cannondale Bicycle Corp. - Recumbent

A while back I saw parts of a similar system for sale, this was a system where the right arm and the spider were separate components.  Alas, I can't remember the brand.

Anyone know where such a thing can be aqcuired? Anyone, perchance, have one? Failing that, does anyone have a right crank that they would like to donate for Mr Hacksaw to pay a little visit?

It'll be used for a project converting a tandem to a cargo bike.

[Cunobelin]

My first thought would be Highpath Engineering

[Ian H]

Easiest thing would be to acquire a cheap chainset and saw the arm crank off. On the more traditional designs it would be possible to make a very neat job.

[Wobbly John]

Why can't you just put suitable chainrings on the front and run the chain straight to the rear hub?

Although this might run the risk of 'Chains a bit slack' comments.

[arabella]

I suppose something like a ghost wheel/sprocket/whatever you call it is no good then?

presumably you want something for the other side of the BB as well, or are you just going to leave the axle sticking out as is?

given that the extracycle has an extra long chain you can probably survive without though.

istr that specialites TA might have had the detachable spiders, there's probably a page in english if you look, I'm sure there was last time.

[fruitcake]

Thanks for the ideas.

Why can't you just put suitable chainrings on the front and run the chain straight to the rear hub?

Although this might run the risk of 'Chains a bit slack' comments.

All the images of long chains show the chain sagging which I assume leads to chain-'bounce' when going over a bump.  I also suspect the extra weight of the chain would affect shifting. 

I suppose something like a ghost wheel/sprocket/whatever you call it is no good then?

Mostly, the cargo to be carried would be food shopping.  Thusly, a phantom chainring would be too appealing for children outside the shops to play frisbee wiv. 

presumably you want something for the other side of the BB as well, or are you just going to leave the axle sticking out as is?

Planning a naked axle non-drive side.

istr that specialites TA might have had the detachable spiders, there's probably a page in english if you look, I'm sure there was last time.

Looks like the TA chainwheel is secured through the arm, the spider being fitted to the arm.

Easiest thing would be to acquire a cheap chainset and saw the arm crank off. On the more traditional designs it would be possible to make a very neat job.

This is now where I'm at.  Since it seems a shame to amputate a usable crank, does anyone have a double or triple chainwheel with damaged pedal threads?

[Cunobelin]

Lateral finking!

Idlers!

Many recumbents use idlers, often with a pair to accept the "drive and return" lengths of chain, and often these move the chain out of it's natural path to allow for frame shape (cross  tube on a trike for instance)

I know tht my Trice and my Catrike had them - so does my Street Machine and Hurricane.

There is a company called "Terracycle" in the States who seem to be the "popular choice" on the 'BentRider site.

Alternatively there were anti "chain suck" or "chain retention" devices for mountain bikes that used a similar concept and could take up slack.

On the other hand there is a possibility to make your own intermediate drive! or go to www.recumbents.com and type in "idler" for  whole range of ideas

[Sigurd Mudtracker]

My Tour Easy clone has a full three lengths of chain winding its way round a front triple and a set of sprockets a long way back.  Not had any problems so far (although I do believe the real thing uses idlers on the non-drive side).

Idlers might be better wrt drag and power losses than an intermediate drive.

[Mr Larrington]

istr that specialites TA might have had the detachable spiders, there's probably a page in english if you look, I'm sure there was last time.

Looks like the TA chainwheel is secured through the arm, the spider being fitted to the arm.

Yep, the spider is secured to the right crank with a lockring.

[PhilO]

Another simple alternative would be to use chain tubes. I've had success on the 'bent just using black plastic conduit from B&Q, but many here will recommend the proper stuff.