Hello; Can anyone advise me on bicycle sprockets / gears?

[james125]

Hello all.

Strictly not a cycling question but I aim to use bicycle components to construct a chain drive to a supercharger for a motorcycle. I want to achieve a gear ratio of between 8:1 and 6:1, is this possible to do with bicycle sprockets? Ideally I'd like to find a website that'll let me buy individual sprockets. Something like a 12 tooth gear and a 90 tooth sprocket would be ideal.

Thank you very much!

 

[Tim Hall]

I think you might struggle with the 90 tooth bit. Road chain rings are generally 52, some are 54, that sort of size. A few specialist time trial machines, or those funny lying down bikes might use something bigger, but 90. Wow. Graeme Obree used something huge for his mile attempt, but I'm guessing that was a special, rather like the rest of his bike. (Google suggests it was 67 teeth)

Highpath Engineering might be able to help, they make specialist stuff.

 

[Canrider]

12 tooth is easy to find. 90 will not be (at least within bicycle-specific off-the-shelf parts).

A very brief internet trawl finds a 60-tooth TA Alize chainring : http://www.peterwhitecycles.com/chainrings.asp
And hostel shoppe have a 73-tooth from Greenspeed (they make trikes): http://www.hostelshoppe.com/cgi-bin/readitem.pl?Accessory=1155076891

 

[slowmotion]

My guess is that you would have to go for a two stage drive because, even if you could find the sprockets, the large one is going to be huge with a simple two sprocket set-up. Also, you should consider the number of tooth engaging with the smallest sprocket. With belt drives, it is usually recommended to have five of six teeth engaged, which implies a minimum tooth number of about 12 teeth on the smaller sprocket (with a huge centre distance.).

Here's a brief intro to chain drives. There are loads more if you Google.
http://roymech.co.uk/Useful_Tables/Drive/Roller_chain.html

 

[Chris Norton]

I know a gear cutting firm. Will probably see it as a challenge.

Phoeniks gears in Boston.

Speak to nik on 07885 992355

Top bloke and one of my oldest friends.