the part about hub and crank drives are very true though, each having benefits - the only bit i would add (having just done fifteen miles on a kalkhoff Tasman) is that a good crank drive with a torque sensor is a revelation, a Chinese crank drive with a movement sensor is really not a revelation, at all, in any sense of the word...
Wisper 905 - what's the Nm torque rating?
- Thread starter allen-uk
- Start date
What, not even downhill? I do that quite often downhill on my way back from the supermarket, gravity powered by shopping!
Here in pedelecs we actually have an unofficial 50 mph club for those who've exceeded that downhill. My best is just fractionally short of that.
See this link item
.
the Bafang BBS01 is somewhere in between. Bafang are playing catch-up and will release their torque sensing version soon. The good thing about Chinese CDs is that you can get more powerful versions.
urgggh, yes, I have done 40 plus on a non electric racer downhill (breaking all laws except nature's), OK, maybe 30 is OK, but a pothole at 50 on my pedelec would definitely result in permanent removal from this forum, so to speak..
I was with Shimano last week at Eurobike. I asked their tech Director what the maximum electronic power they would allow through ANY of their transmission systems, as we can turn the new Kombi centre motor up to well beyond 100Nm.
His reply was 30Nm from standstill building up to 50Nm when the bike was moving otherwise the Shimano components will not be within warranty. Worth remembering when purchasing a mid motor bike. The best set up is a Nuvinci 360 through a Gates or Continental carbon belt, but that is expensive.
Hub motors of course don't have to go through the bike's transmission.
All the best
David
His reply was 30Nm from standstill building up to 50Nm when the bike was moving otherwise the Shimano components will not be within warranty. Worth remembering when purchasing a mid motor bike. The best set up is a Nuvinci 360 through a Gates or Continental carbon belt, but that is expensive.
Hub motors of course don't have to go through the bike's transmission.
All the best
David
yes, I used to have a giant lafree/twist that aye hub gears (went through three in as many years). incongruously though my OH's klakhof tasman remains fine despite her (and me) putting much more than the maximum 70nM through its shimano 8 speed hub. I frankly don't understand it (I assume its the pause thingy between gears that make the teeth mesh much more completely)..
the Bosch Classic motor in the Tasman has 44T on the front cog, 20T on the Alfine-8 on the rear cog, the maximum torque transmitted to the rear cog is 50NM * 20/44 = 22.7NM, within the recommendations.
The four speed Shimano hub gear that was on one of the Lafree range for a while suffered numerous failures and as a result, Shimano discontinued it. That was replaced by the SRAM 5 speed and later the SRAM 7 speed hub gear, but they suffered a very slow downward gear change. Trying to rush those usually lead to eventual trouble due to chips of metal being broken away and either breaking up the rest or jamming the gear stationary.
The much larger diameter Shimano 8 speed hubs have more robust components, probably contributing to the better reliability.
.
Last edited:
I'm afraid youre wrong - teh tasman with impulse 2 (that's all tasmans that are less than a year old) have an impulse 2 motor with 70 nM.
but you are right to bring in the way gears (naturally) affect torque on a hub, it's easilly overlooked (though my lafree with all of its 24 V nonetheles ate all hubs - sram included - until i put in a rohloff )
30Nm from rest is remarkably low when a 15 stone rider standing on the pedals exerts a torque of over 140Nm.