2 to 3 speed

[12boy]

There have been some posts on converting an S RF3 3 speed SA hub to a six by adding a second sprocket. I have a 2 speed hub with 12 and 17 tooth sprockets and a chain pusher. Is there a way to add another sprocket to that hub, and if so has anyone done it? I really like the lightness of the 2 speed hub and a step between 55 and 78 gear inches would be nice.

 

[TheDoctor]

I'm sure it could be done. I'd start by taking a 10 speed cassette to bits, getting three sprockets and two spacers, and fitting instead of the two sprockets you have. Then either modify the existing shift lever by filing an extra notch, or fit an old-skool MTB friction thumbshifter. Three speed conversion kits are around IIRC. Usually sold for fitting to a 6 speed to make a 9 speed, but they should work just as well for your purposes.

 

[Schwinnsta]

I have made that mod. I got the Bikegang kit. It came with three cogs, spacer, derailleur mod to clamp the cable end, and clip ring. I also bought a 10 speed chain and a Sunrace 3 speed friction shifter. It works well. I had to add a spacer / washer on the axle on the inside of the drop out as there was a slight interference with out it.

 

[berlinonaut]

There have been some posts on converting an S RF3 3 speed SA hub to a six by adding a second sprocket.

Which - just for the record - does not work w/o using frewheel parts of the BWR, does not add much benefit and thus is a pretty unusual mod. Possible, but more than uncommon.

I have a 2 speed hub with 12 and 17 tooth sprockets and a chain pusher. Is there a way to add another sprocket to that hub, and if so has anyone done it?

In principle it works the same way as the 9-speed mod that I did to my BWR. I even think many years ago in this very forum was the first mention of a 2-to-3-speed mod that I read of. It was documented as a pdf and it was made on a 2-speed. Could later be found in the (no longer existing) Bromptontalk-wiki as well. I did an extensive write up of my mod over at bikeforums and I think here in the forum are at least a couple of links, possibly in the BSR-thread as well.

 

[12boy]

I will try both ideas...I was thinking that a10 speed chain would be needed. Thanks.

 

[berlinonaut]

I will try both ideas...I was thinking that a10 speed chain would be needed. Thanks.

That's what I used, just to be sure. No idea if it was really necessary. Probably not.
If you want to go further: You can btw. in the meantime also buy a rear wheel from brommieplus (via their website or via ebay) that is using a Hubsmith hub that is able to take 3 sprockets by default and 4 if wanted, including the benefit of being able to use an 11t sprocket.

 

[12boy]

Will be checking that. The Bikegang kit at 25 pounds for 3 sprockets and a C clip seems a bit much.

 

[bikegang]

Will be checking that. The Bikegang kit at 25 pounds for 3 sprockets and a C clip seems a bit much.

If you can wait, we will have new pilot sample out soon. 11T/14T/17T all in one (CNC machined by KCNC ) for easier installation and more efficient drive, if you like to be our lab rat?

 

[12boy]

Sure would...sweet ratios and an unobtanium 11 tooth!

 

[u_i]

11T/14T/17T all in one (CNC machined by KCNC ) for easier installation and more efficient drive

CNC suggests aluminum. Is that correct?

 

[12boy]

Sure hope not..Al sprockets, especially with 11 teeth would wear out PDQ.

 

[TheDoctor]

You can CNC mill any material, if you have suitable kit. It's not limited to aluminium.

 

[TheDoctor]

Will be checking that. The Bikegang kit at 25 pounds for 3 sprockets and a C clip seems a bit much.

You do get a shift lever too. The Brompton 2 speed sprocket set costs £10, so an extra 15 for another sprocket and a lever sounds reasonable.

 

[u_i]

You can CNC mill any material, if you have suitable kit. It's not limited to aluminium.

The cost for steel is 4-8 times higher.

 

[12boy]

Be good to check it out.