3 speed Deraillier Conversion

[BADGER.BRAD]

A friend of mine ( new to cycling) asked me why his bike has so many gears (24) and then went onto explain he only ever had 3 gears on his various bikes as a kid. With this in mind I decided to convert my lads hack single speed mountain bike back to gears, As I had converted to single speed ( the complete gear train was trashed) by separating two cassettes and using the spacers to align the chain wheel and sprockets it was easy enough to use the same principal to make it a 3 speed. I tried to make each gear change a fair jump from the next and have settled on 42 teeth at the front and 24,17,11 at the rear. We used the front gear change lever ( friction type) and had to use a gear change cable with the an outer cable the full length of the cable as My lad had knocked all the cable stops off on the single speed conversion! with a quick adjustment it all works and the jumps between each gear are smack on. My commuter only has 8 gears and I only ever seem to use top or bottom for any length of time. The daft rainy day experiment seems to have worked well the only small problem I have is the chain jumps in top gear if you really give it some stick whilst riding up hill ,obviously a result of the whole drive train being a combination of nearly dead parts from different bikes (the chain is made up of two old chains).

Anyone know how much of a jump a Sturmey archer 3 speed gives between each gear ?

 

[Psycolist]

Luvin the ingenuity and that you obviously hate to throw anything away In terms of the jumping, just make sure it isnt a tight link where the chains have been joined. As far as the ratio's , sorry but I aint got a Danny LaRue

 

[RecordAceFromNew]

If you were expecting a simple answer, you would probably be disappointed after looking at this! But generally speaking your amazing contraption* has a wider range...

* But why stop at 3?

 

[BADGER.BRAD]

Thanks for the replies, I have now altered the gearing as being able to wheelie the bike to school is an essential part of cycle gearing so I'm told ! This puts the high gear back to it's original single speed gearing but also has the advantage that the high gear doesn't jump any more ( I had a spacer next to the 11 tooth sprocket so the chain would not drop deep enough into the sprocket to get a good grip) I have shortened the chain as well as it jumped off a few times over bumps so my lad said. For my trip to work I could most likely get away with two gears but I'm not sure it would like the large jump between the highest and lowest gear that I would require, The centre gear gives it a little more help.As for why stop at 3 I was just wondering how few gears I could get away with in my hilly area.

 

[sidevalve]

Now you know why the old 5 speeders weren't all that bad in everyday use. Although I admit manufacturers did often fit over high bottom gears.

 

[tyred]

Now you know why the old 5 speeders weren't all that bad in everyday use. Although I admit manufacturers did often fit over high bottom gears.

My 1970s Viking Superstar has a 14 - 24 5 speed block and changed the single 48t cottered chainset for a 40t (lucky ebay find, small cottered 3/32" chainsets are rare) and I find it works extremely well. Top gear works out at around 78" but it's high enough for me tbh as I ride on lumpy, twisty, poorly surfaced back roads most of the time and have no use for high gears.

I would highly recommend the single front chainwheel with rear derailleur approach for anyone who wants an easy to use bike with closer spaced gears than a Sturmey allows.

 

[TheDoctor]

1*7 all the way for me, at least for the tourer.
40T chainset, and a 12-32T 7 speed cassette. Top of 90" (higher than I need) and low of 34".

 

[Chris S]

Anyone know how much of a jump a Sturmey archer 3 speed gives between each gear ?

First gear is -25%
Second gear is direct drive
Third gear is +33%

On my 44/18 roadster with 26 inch wheels this works out at about the following:
1st 47 inches
2nd 63 inches
3rd 84 inches

Ideally first gear would be around 40 inches for me, but 47 inches is still low enough to get me up most urban hills without too much effort.

 

[BADGER.BRAD]

I run 44 front and 11-34 on the rear on my commuter which works fine for my commute although a little higher would be nice. As It's all up and down here I tend to either be in top or bottom gear for 85/90% of the time hence the reason the 3 speed dérailleur works so well on the hack bike. I will most likely be having a look on Fleabay for a nice cheap 7 speed rear cassette at some point !