New 9 Speed Internally Geared Hub with 554 Gear Range

[Merlin]

Hi,
I'm involved with a rear IGH project that will be a 3-speed 400% range with a torque rating over 350nm and no under-drive ratios (1;1, 1:2 & 1;4). I'm guessing you don't use any of your under-drive ratios for 90% of your riding given the power of the Bafang Ultra so wanted to get your thoughts on the described IGH solution.

Also I believe you might be exceeding the torque rating on the 3x3 with a belt drive ratio with nearly same size front and rear sprockets. I'm just wondering if you think the life could be impacted if the torque limit is exceeded because Rohloff has a table defining what the final drive ratios should be to avoid damaging the IGH.

Our IGH will accept the full rated torque at the IGH axle which is not possible with any IGH we know of.

The 3x3 Nine comes stock with a 32T rear sprocket, so I do not believe a 42T will put me past the 250 nm torque limit. You are correct, the first 3 gears are so low that only a mountain bike on a very steep trail might benefit from them and the last two gears put me faster than I am comfortable with. I start out in fourth gear on power level 1 and at gear 7 I go to power level 3 for a fast ride. A three speed would be great with a 350nm of torque if it is built for a Gates Belt and can achieve 28mph with a 42T front sprocket. My frame clearance for a larger front sprocket looks sketchy. 90% of the ride I only use gears 4 through 7. Gears 8 and 9 put me over 28mph at 60 cadence.

 

[Ken M]

The 3x3 Nine comes stock with a 32T rear sprocket, so I do not believe a 42T will put me past the 250 nm torque limit. You are correct, the first 3 gears are so low that only a mountain bike on a very steep trail might benefit from them and the last two gears put me faster than I am comfortable with. I start out in fourth gear on power level 1 and at gear 7 I go to power level 3 for a fast ride. A three speed would be great with a 350nm of torque if it is built for a Gates Belt and can achieve 28mph with a 42T front sprocket. My frame clearance for a larger front sprocket looks sketchy. 90% of the ride I only use gears 4 through 7. Gears 8 and 9 put me over 28mph at 60 cadence.

Thanks for the feedback. One of the shortfalls for an IGH based on compound planet gears is the under-drive ratios which tend to be of dubious value on commuting ebikes, especially higher power ebikes. We will have less gears but non will be below a 1:1 direct drive ratio so the final drive ratio from the front sprocket to the rear should be kept close to equal which helps belt life while allowing the rider to fine tune a speed/cadence for the ebike.

 

[teskow]

I have both a 9 spd and an 11 spd on Specialized ebike. I really liked the 11 spd and never had experience with the 9 until I changed one of them. I prefer the 9, less shifting and as someone said, my cadence preference expanded.

Re oil bath or grease, I had a 3 point brushcutter on a tractor that wouldn't hold oil. I filled the differential that drives the blade with grease and never had a problem. One of the tractors also had an oil bath gear drive above the front wheels for steering. Wouldn't hold oil so filled it will grease, no problems. There are also different grades of grease, some really hard and some runny.

I believe that is what corn head grease is designed for.