jawnn

What is the over lap in gears if using a 12-24 cassette with the Sram duel drive 3 speed or the Sturmey Archer F30 3 speed??

Does the F30 jump 177% for each gear? I do not know what the Sram does.

I like the idea of having much lower gears for a trike.

KC8QVO

You can figure out the ratio. Take the stock drive tooth count on the internal gear hub then set it proportional to the tooth count of the rest of the cassettes in the set. 18t on the hub vs a 26t on the cassette = 1.44. (take 26t and divide it by 18t = 1.44). Then take the gearing of the IGH range and multiply by that 1.44 to get the total range.

Say the top end is 260% and the low end is 75%, using the same 18t drive cog. Using a 26t cassette on top of it would get you a range of (1.44x.75)=1.08 to (1.44x2.6) = 3.74. Put another way, the range on the 18t cog is .75-2.6 and with a 26t cog it is 1.08-3.74. If the 18t cog is the low end and the 26t cog is the top end on that set your "total" range is now .75-3.74, or 75% to 374%.

Make you a spread sheet on Excell or Open Office Calc and put the numbers in. That makes it easy to change up ratios too - change one number and the rest calculate through at the click of the enter button.

fietsbob

If the DIY math is too much https://sheldonbrown.com/gears/internal.html

want more complexity? make it up with a half step chainring set.




the AW3 2nd to 3rd up 1:1 to 1:1.33 [1/3 up]

the 2nd to 1st Down Shift is from 1:1 to 1:0.75 [1/4 down]

davidad

The 3speed hub is only useful in the top or bottom gear. If you want to get wild try a shimano Capreo hub with a 9t to 32t ten speed cassette. https://bike.shimano.com.sg/media/tec...9830702944.pdf
https://bike.shimano.com.sg/media/tec...9830604456.pdf

A friend has ICE and Greenspeed trikes with this hub and cassette.

jawnn

OK this should tell me something

- Overall Range - 177%
- Gear 1 - 75% (-)25%
- Gear 2 - 100% Direct Drive (Gear 1 + 33%)
- Gear 3 - 133% (+)33.3% (Gear 2 + 33%)

Bill Kapaun

The simple way is 3/4, 1, 4/3

fietsbob

Its useful when you cannot fit a triple crank .. the 3 internal-hub gears replace the triple crank .

Want to know ratio overlap ? do the math yourself.

jawnn

So I did some math... hope its not wrong:

22 sprockets on the front / 34 on the rear x 26 wheel = 16.82 gear inches minus 77% = 12.95 gi

And on 20 inch wheel

22/34 x 20 = 12.94 gi minus 77% = 9.96 gi

It would be much cheaper to use a Mountain tamer fourth chain ring for 10.5 gi with a 18 sprocket chairing and 20 inch wheel.



But I am glad to see that it does have some use for some one. (Its useful when you cannot fit a triple crank)

mconlonx

On a 12-28 7 sp cass, each shift with the Dual Drive IGH seems to account for 2 shifts of the cass. Meaning, if I'm in second (middle) gear with the DD IGH and I drop down to low gear, if I upshift twice on the cass, it feels like basically the same gear.