Need offset crank, or bottom bracket

Hi. I'm working with some volunteers who are building a bike generator
exhibit for an energy expo. We have a bucket seat set up and an old bike
cut up and mounted upside down so that the person in the seat can peddle
the bike (ala recumbent). The wheel of the bike is belted to a car
generator.

So the setup (viewing from the seated person's left side) is generator,
bike wheel, chain, bottom bracket, seat. Our problem is to cover the
mechanism with plexi to keep little (or big) fingers from the moving
parts. The problem is the lack of clearance between the crank arm and
the chain ring of the BB so that the plexi will cover the ring and chain.

Is there such a thing as a highly offset crank? Is there such a thing as
a highly offset spindle??

Any ideas greatfully appreciated.

Elmer ? wrote:
Hi. I'm working with some volunteers who are building a bike generator
exhibit for an energy expo. We have a bucket seat set up and an old bike
cut up and mounted upside down so that the person in the seat can peddle
the bike (ala recumbent). The wheel of the bike is belted to a car
generator.

So the setup (viewing from the seated person's left side) is generator,
bike wheel, chain, bottom bracket, seat. Our problem is to cover the
mechanism with plexi to keep little (or big) fingers from the moving
parts. The problem is the lack of clearance between the crank arm and
the chain ring of the BB so that the plexi will cover the ring and chain.

Is there such a thing as a highly offset crank? Is there such a thing as
a highly offset spindle??

Any ideas greatfully appreciated.

The crank and chain-case from an old roadster:
http://www.yellowjersey.org/EASTGIRL.JPG[1], perhaps?

[1] State Capitol Building optional.

--
Tom Sherman - 42.435731,-83.985007

On 1/19/2010 2:03 PM, Elmer wrote:
Hi. I'm working with some volunteers who are building a bike generator
exhibit for an energy expo. We have a bucket seat set up and an old bike
cut up and mounted upside down so that the person in the seat can peddle
the bike (ala recumbent). The wheel of the bike is belted to a car
generator.

So the setup (viewing from the seated person's left side) is generator,
bike wheel, chain, bottom bracket, seat. Our problem is to cover the
mechanism with plexi to keep little (or big) fingers from the moving
parts. The problem is the lack of clearance between the crank arm and
the chain ring of the BB so that the plexi will cover the ring and chain.

Is there such a thing as a highly offset crank? Is there such a thing as
a highly offset spindle??

Any ideas greatfully appreciated.

You can get cheap wider one-piece cranks. They are used with
bicycle-engine kits, to provide clearance for the engines that mount in
the front triangle of the frame.

Here is one example for $30:
http://www.bicycle-engines.com/wide-...dal-p-106.html
-made tiny-
http://tinyurl.com/yd9dbb4

These kits are made to mount on the cheaper (department-store) bikes so
if that's the parts your working with already, you shouldn't have much
problems fitting them.

Where else to get them I am not really familiar with.
Two largely-US-centric bicycle engine forums to ask on would be
http://www.motoredbikes.com/
and
http://motorbicycling.com/
in no particular order. Or just click on the ads you see there selling
engine kits.

Good luck.
~

DougC wrote:

Elmer wrote:

Hi. I'm working with some volunteers who are building a bike generator
exhibit for an energy expo. We have a bucket seat set up and an old bike
cut up and mounted upside down so that the person in the seat can peddle
the bike (ala recumbent). The wheel of the bike is belted to a car
generator.

So the setup (viewing from the seated person's left side) is generator,
bike wheel, chain, bottom bracket, seat. Our problem is to cover the
mechanism with plexi to keep little (or big) fingers from the moving
parts. The problem is the lack of clearance between the crank arm and
the chain ring of the BB so that the plexi will cover the ring and chain.

Is there such a thing as a highly offset crank? Is there such a thing as
a highly offset spindle??

Any ideas greatfully appreciated.

You can get cheap wider one-piece cranks. They are used with
bicycle-engine kits, to provide clearance for the engines that mount in
the front triangle of the frame.

Here is one example for $30:http://www.bicycle-engines.com/wide-...dal-p-106.html
-made tiny-http://tinyurl.com/yd9dbb4

These kits are made to mount on the cheaper (department-store) bikes so
if that's the parts your working with already, you shouldn't have much
problems fitting them.

Normal one-piece cranks are probably more than wide enough for what
the OP is talking about. Normal MTB cranks of the '00s era are
probably wide enough, too.

I suspect that the basic problem arises from starting with a vintage
road bike or other bike with an old-fashioned 3-piece crank that has
narrow tread width.

Chalo