2 to 3 speed

[u_i]

Chain Guide Disc

Spacer for tensioner?

 

[bikegang]

Bromptons and other small wheeled bikes run through sprockets, especially small sprockets much faster than 700c bikes. It would be good to be able to replace them individually.

Just learned that it is not possible to produce single cog 11t for stock brompton hub, too small the remaing steel rim, will break easily. Only if it is attached to another cog ... (It is possible for 3rd party hub that uses screw in cap? instead of C clip type fastener)
Confirmed material is SCM440H heat treated steel. ED-Electrophoresis deposition surface processed black.
will pm (conversation) you shipping address, please check.

 

[12boy]

I've sent you my address today.

 

[u_i]

What is the point of choosing 11-14-17 cogs? What is this combination supposed to achieve? I am using 12-14-16 which gives 16% of gear jump optimal for BWR as 1.57^(1/3)=1.16. With 14/11=1.27, i.e. 27%, it is just as bad as with 2 sprockets. I do not see this choice doing anything either for BSR. Am I missing something?

 

[12boy]

I like the 11 because I would enjoy having the higher gear inches. With my 58/38 chain ring setup, I get 85, 67 and 55 GI on the large chain ring and 56, 44 36 on the small, good for around here. If more climbing was in store a 32 chain ring would get me down to a low of 31. I've done ok here with the 38, though. The 67 GI on the big chain ring would be a treat for level ground with 20 mph headwinds or moderate grades. I am an inveterate grinder though and rarely peddle much over 70 rpm.

 

[12boy]

I should have read your post more carefully. My current set up is a 2 speed hub, with 12/18 sprockets. Were this to work well on post my BSR I could get by with just one chain ring.

 

[Schwinnsta]

What is the point of choosing 11-14-17 cogs? What is this combination supposed to achieve? I am using 12-14-16 which gives 16% of gear jump optimal for BWR as 1.57^(1/3)=1.16. With 14/11=1.27, i.e. 27%, it is just as bad as with 2 sprockets. I do not see this choice doing anything either for BSR. Am I missing something?

I have 12-14 -17. So just a 3 speed. I like having a low for climbing. I may replace 17 with a 19. Once your over a hill you can go directly to high. You don't need the in between gears.

 

[u_i]

I have 12-14 -17. So just a 3 speed. I like having a low for climbing. I may replace 17 with a 19. Once your over a hill you can go directly to high. You don't need the in between gears.

If the 3 sprockets yield your only gears, sure you want to spread them out. If you piggyback them on the gears that are already spread out, you want to fill the gaps and limit the overlaps. Optimal jumps are 12% or so, but this is hard to do on a Brompton, 15% or 16% is a compromise and you go with 25% if you have no choice.

 

[bikegang]

I have 12-14 -17. So just a 3 speed. I like having a low for climbing. I may replace 17 with a 19. Once your over a hill you can go directly to high. You don't need the in between gears.

We like to provide as wide gear range as possible yet compatible with as many stock parts as possible
Need to file off frame end or clamp it in order to fit 19T. But not major issue. 19T is the biggest cog the stock tensioner can take.

 

[bikegang]

Be good to check it out.

Looks nice with hub 40g

 

[12boy]

What is the point of choosing 11-14-17 cogs? What is this combination supposed to achieve? I am using 12-14-16 which gives 16% of gear jump optimal for BWR as 1.57^(1/3)=1.16. With 14/11=1.27, i.e. 27%, it is just as bad as with 2 sprockets. I do not see this choice doing anything either for BSR. Am I missing something?

I don't think this will work on the BSR because even 2 sprockets won't work. The driver on the BWR is made for 2 so it should be ok for that

Looks nice with hub 40g

View attachment 505078

View attachment 505075

View attachment 505076

View attachment 505077

That does look nice.

 

[u_i]

I don't think this will work on the BSR because even 2 sprockets won't work. The driver on the BWR is made for 2 so it should be ok for that

I missed the fact that its premise is to increase the speed number without a gear hub. While it might be possible to put it on BWR, the choice of cogs is not the best for such purpose. Sorry for the confusion

 

[12boy]

I actually called my favorite Brompton shop to see if the two sprocket driver that comes on BWR hubs could be bought separately for my BSR and they said they couldn't get the driver that way and had to buy the whole hub. I assume Sturmey Archer makes the Brompton 1/2 speed hub but don't know for sure. Anyone know who makes it?

 

[u_i]

I lack a direct experience with BSR, but my understanding is that it takes Sturmey-Archer specific cogs (3-spline), not Shimano type (9-spilne) like BWR. The simplest conversion is to get 2 such cogs and put a spacer in-between. There is a long thread on BSR conversion and this is the best way I can summarize it:

https://www.cyclechat.net/threads/brompton-3-or-6-gears.251949/

 

[bikegang]

I actually called my favorite Brompton shop to see if the two sprocket driver that comes on BWR hubs could be bought separately for my BSR and they said they couldn't get the driver that way and had to buy the whole hub. I assume Sturmey Archer makes the Brompton 1/2 speed hub but don't know for sure. Anyone know who makes it?

They are made in Sturmey Archer (now in Taiwan / SunRace) , My impression is you can change the free hub body to the shimano 9 splines spec. Let me check.
It will be something like this ==>