3 Speed Hub Gear With a Triple?

[cycleruk]

Purely from "simple" thought I wouldn't have expected any problems because of small chainsets.

OK, imagine tightening up a 1/2" nut with a 5" long spanner, you've not got enough leverage to round off the corners.

now imagine trying with a 4 foot long spanner - the corners are gone.

the same goes for the little teeth on the little cogs within the hub. there's a minimum mechanincal advantage below which you shouldn't go. for an i-motion9, that's 1.7:1.
for an SA AW, some of us seem to recall that it's 2:1, but no-one can find the definitve answer.

I understand what you say but the "spanner / nut" is up against a "dead end".
A hubgear isn't, it's just put under more load depending on a steep hill / force and rolls forward. (except against a brickwall. )
Thinking of a standing start, then a small chainring is easier to get going than a large one so would this make any difference?
The most that I can see is the weight of bike and rider but I don't understand if that will be any different due to chainring size?

Sorry for running 2 threads in one post!

[pioneer]

Mick, 26 miles on a Chopper? Now I'm impressed!

You'll be on Westcountry news (or whatever it's called these days), soon. I can see it now "I'm the biggest kid in the village!"

Well done Mick. Don't know LEJOG (or is JOGLE?) will be enough for you now. How about New York - L.A.?

[Mick F]

JOGLE will be enough.
I'm already tired of the thing.

I really need to do a LONG ride. 50 odd would be right, and weather permitting, I'll be doing one tomorrow or Wednesday. (busy Thursday and Friday) Maybe the weekend, but unless I can do a 50 or 60, I won't be able to gauge my overall speed. The longest leg I have to do is 88 miles - Inverness to Pitlochry.

[hubgearfreak]

Purely from "simple" thought I wouldn't have expected any problems because of small chainsets.

OK, imagine tightening up a 1/2" nut with a 5" long spanner, you've not got enough leverage to round off the corners.

now imagine trying with a 4 foot long spanner - the corners are gone.

the same goes for the little teeth on the little cogs within the hub. there's a minimum mechanincal advantage below which you shouldn't go. for an i-motion9, that's 1.7:1.
for an SA AW, some of us seem to recall that it's 2:1, but no-one can find the definitve answer.

I understand what you say but the "spanner / nut" is up against a "dead end".
A hubgear isn't, it's just put under more load depending on a steep hill / force and rolls forward. (except against a brickwall. )
Thinking of a standing start, then a small chainring is easier to get going than a large one so would this make any difference?
The most that I can see is the weight of bike and rider but I don't understand if that will be any different due to chainring size?

OK, think of a tight nut that needs undoing. the same scenario as a bike starting off. of you have too much mechanical advantage (leverage) you'll break stuff.

Sorry for running 2 threads in one post!

you're not, it's them with their talk of a toy bike that are

[Mick F]

Sorry
I feel chastised!

Actually, I came onto this thread because I had some info about a double chainset with a SA 3sp.

[hubgearfreak]

threads are doing that all the time mick, it doesn't matter, does it?

[cycleruk]

[

OK, think of a tight nut that needs undoing. the same scenario as a bike starting off. of you have too much mechanical advantage (leverage) you'll break stuff.

Sorry for running 2 threads in one post!

you're not, it's them with their talk of a toy bike that are

O.K. I give up. My brain hurts. I'll stick to my derailleur gears.

Toy bike

[Mark_C]

Not sure why nobody has mentioned this yet, but the problem with combining a triple and a 3-speed hub is that you will have nine ratios but neither shifter on its own will give you reasonably small steps. So every gear change will be a double shift. Also, some of your ratios may be duplicates. Even with nine distinct ratios, and a cunning sequence of double shifts, since you will have a fairly large overall range the steps between ratios will be larger than the ideal.

[hubgearfreak]

some of your ratios may be duplicates.

isn't this the case for any triple chainwheel?

[cdtb]

hi
Have just read the thread with interest, firstly because I owned one of the Mk 1 Choppers -great bike to look at but hard work to ride on the hills - good luck Mick. Secondly, I have used a 3 speed Sturmey AW hub with a five speed 28-16 freewheel screwed onto a Sturmey threaded driver, coupled to a 52/36 chainset, for almost 30 years. The set up has been superb, versatile, reliable and robust. The hub has been stripped down 3 times and serviced during that time. On one occasion when the hub had to be dismantled it was realised that i had a snapped a 'leg' on a threaded driver. Three freewheel bodies have been used, several individual sprockets replaced, and several double chainrings replaced. The bike has been used most days over the last ~30 years, predominantly as a commuter/shopper, but has also been used for heavy laden camping/touring in hilly terrain -without problems. I'm not very strong and weigh 73kg but I was interested to read about the 'maximum ratio' issue and clearly i have exceeded 2:1. Maybe i have been lucky but the durability of this set-up is testimony to the robustness of this hub. and i can throughly recommend adding a triple to an AW three speed hub.

[hubgearfreak]

so you've had a 30 speed bike for decades?

thanks for sharing the facts with us. it's interesting to know we can ignore the 2:1 that we've got stuck in our heads, but where it's come from remains a mystery

got any photos?

[robinlh]

Also in Cornwall,the other end.
Its the weather you know.
Before I forget,that was a beautifully restored or maintained chopper.
R

[steve browne]

Re: Breaking a Sturmey Archer hub gear from using too much torque/too low a gear. Whilst riding up a steep hill in bottom gear of a S5/2 hub there was sudden and complete failure due to the hub locking. Dismantling revealed two faults 1) One of the two low gear pawls was misaligned due to one end of its rivet having slipped out of the planet cage allowing it to take up a position at an angle to the axle instead of inline with it. Poor manufacturing tolerance? 2) One of the four arms had snapped off the sliding clutch (same as in the 3 speed hub). This was using a 36tooth chainring and 32 tooth rear sprocket giving a gear of 20.3". The hub had been in use for twenty years including touring whilst fully laden. I have replaced the planet cage and clutch and will be using a higher bottom gear in future. This may be of use to anyone else running hybrid systems and very low gears with Sturmey Archer hubs.

[steve browne]

Re: Breaking a Sturmey Archer hub gear from using too much torque/too low a gear. Whilst riding up a steep hill in bottom gear of a S5/2 hub there was sudden and complete failure due to the hub locking. Dismantling revealed two faults 1) One of the two low gear pawls was misaligned due to one end of its rivet having slipped out of the planet cage allowing it to take up a position at an angle to the axle instead of inline with it. Poor manufacturing tolerance? 2) One of the four arms had snapped off the sliding clutch (same as in the 3 speed hub). This was using a 36tooth chainring and 32 tooth rear sprocket giving a gear of 20.3". The hub had been in use for twenty years including touring whilst fully laden. I have replaced the planet cage and clutch and will be using a higher bottom gear in future. This may be of use to anyone else running hybrid systems and very low gears with Sturmey Archer hubs.

[rogerzilla]

The only AW failure I know of was on a tandem; and SA were always a bit cagey about whether they were suitable for that use. The teeth were stripped off the planet gears.

SA hubs have a very easy life on a Brompton - the torque is about half that on a bike with 700c wheels, although they obviously make a lot more rotations.