Wisper 905 - what's the Nm torque rating?
- Thread starter allen-uk
- Start date
Bafang rear motor, though I don't know which version, I think the 36 volt 16 amp controller had taken over from the 15 amp one at that date. With restriction off it was geared to give 18 mph assist, so I'd guess a torque figure around 40Nm.
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Deleted member 4366
Guest
It doesn't have a torque figure because the torque varies with speed. At 5mph, it makes about 30Nm, but at stand-still that increases to 45Nm, , though you can't use that torque on the road, and at maximum no-load speed, it's close to zero. An Ezee motor gives about 45Nm at 5mph and a Bafang BPM.CST about the same with their 20A controllers
I'm speaking of what is likely to be the claimed figure of course, I doubt Wisper would claim less, since you want to compare and the claimed figures are all you have on most makes Allen.
But as d8veh says above and about crank units in another current thread on this subject, there really are no reliable specific figures for accurate comparison, so comparison rides are the best guide.
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But as d8veh says above and about crank units in another current thread on this subject, there really are no reliable specific figures for accurate comparison, so comparison rides are the best guide.
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Thanks for the comments, and the ones on my linked question about What torque actually IS, i.e. what it measures.
Can't say I fully grasp it yet, but I'm trying.
Try this for size (and we're talking off-road bikes here):
1st) On the one hand, a 500W 48V bike with a claimed torque of 80Nm.
2nd) On the other hand, a 250W 36V bike (similar frame, gears, etc to the other) with a claimed torque of 40Nm.
Are there ANY circumstances, configurations, of electrics/bikes/etc., where the SECOND bike could be described as being 'as powerful' as the first, when talking about each bike's hill-climbing capabilities?
Or (as I suspect) are the laws of physics being ignored in favour of the laws of salesmanship?
Ta.
A
Can't say I fully grasp it yet, but I'm trying.
Try this for size (and we're talking off-road bikes here):
1st) On the one hand, a 500W 48V bike with a claimed torque of 80Nm.
2nd) On the other hand, a 250W 36V bike (similar frame, gears, etc to the other) with a claimed torque of 40Nm.
Are there ANY circumstances, configurations, of electrics/bikes/etc., where the SECOND bike could be described as being 'as powerful' as the first, when talking about each bike's hill-climbing capabilities?
Or (as I suspect) are the laws of physics being ignored in favour of the laws of salesmanship?
Ta.
A
Probably salesmanship, but if we ignore the claimed torque figures, gearing matters also. If the 500 watt one was hub-motored and geared internally for high assist speed, and the 250 watt one geared for low assist speed, they could be fairly equal in hill climbing.
But of course there are so many suspect statements in the originals, for example the 500 watt and 250 watt figures. The 250 watt will usually be a purely nominal figure for legal reasons, many 250 watt rated e-bikes are capable of 500 watts of actual power, sometimes even continuously. Equally we don't know what the 500 watt one is without further clarification. The voltages don't necessarily mean anything in hill climb terms, higher voltages are often used for higher speeds, gaining no torque.
Generally though, claimed torque figures do have some relationship to truth, so if one is claiming twice as much, it will usually be the better climber. But as d8veh has already said, crank drives through the chain have their torque at the rear wheel determined by the chosen bike gear. The lowest gear gives the most steep climb capability, but as said, at the cost of the corresponding low speed. The crank drive Tonaro e-bikes claim 120Nm torque force for example, but that will be in bottom gear so climbing at a very low cycling speed.
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But of course there are so many suspect statements in the originals, for example the 500 watt and 250 watt figures. The 250 watt will usually be a purely nominal figure for legal reasons, many 250 watt rated e-bikes are capable of 500 watts of actual power, sometimes even continuously. Equally we don't know what the 500 watt one is without further clarification. The voltages don't necessarily mean anything in hill climb terms, higher voltages are often used for higher speeds, gaining no torque.
Generally though, claimed torque figures do have some relationship to truth, so if one is claiming twice as much, it will usually be the better climber. But as d8veh has already said, crank drives through the chain have their torque at the rear wheel determined by the chosen bike gear. The lowest gear gives the most steep climb capability, but as said, at the cost of the corresponding low speed. The crank drive Tonaro e-bikes claim 120Nm torque force for example, but that will be in bottom gear so climbing at a very low cycling speed.
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Deleted member 4366
Guest
It's easier to answer you question with examples. A bike with a 500w Bafang BPM motor and 30 amp controller would literally be able to ride rings around your Wisper when climbing a steep hill. It would have approximately double the climbing power, so it would be able to go up a hill twice as steep at thr same speed or one jusft as steep at twice the speed. It would be no contest.
If you use twice the power, you need a battery that can provide it, and it'll use up its charge twice as quickly, so you need a bigger battery.
If you use twice the power, you need a battery that can provide it, and it'll use up its charge twice as quickly, so you need a bigger battery.
Thanks flecc, d8veh, all makes sense.
Seems like this could be a job for BEBA, laying down guidelines for the measurement of torque in ebikes. Needs doing before the whole ebike industry descends into the same sort of anarchy as, say, personal computers, where comparisons are so difficult for a non-technical buyer.
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Seems like this could be a job for BEBA, laying down guidelines for the measurement of torque in ebikes. Needs doing before the whole ebike industry descends into the same sort of anarchy as, say, personal computers, where comparisons are so difficult for a non-technical buyer.
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i wish someone would design a motor that can consume 30 amps and take one up a very steep hill and yet cruise at 20mph using 20 amps and so not need a huge battery..
That'll be the BBS02 then?
I am considering getting one shortly and putting it on a mountain bike for off road riding.
A bit dearer than your quoted price but in the UK and with free delivery.
http://www.custom-ebikes.com/bafang-bbs02-750w-mid-drive-motor/
I will be using the battery from my Dillenger kit and mounting it in a triangle bag.
I am considering getting one shortly and putting it on a mountain bike for off road riding.
A bit dearer than your quoted price but in the UK and with free delivery.
http://www.custom-ebikes.com/bafang-bbs02-750w-mid-drive-motor/
I will be using the battery from my Dillenger kit and mounting it in a triangle bag.
I don't mind - but also sincerely don't like - movement sensors and crank drives. I had a vision of a powerful but economic hub drive and a rohloff setup (have an extra one) with the hope that movement sensors are less unhelpful in that configuration
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Deleted member 4366
Guest
There's loads of motors can do that: the obvious ones are the 500W Bafang BPM (code 11 or 12) and the 500w 36v Bafang CST.
At 20 amps, you'll flatten a 10aH battery in about 25 minutes, so you still need a reasonably big battery - something above 15ah unless your journeys are short.
for 500W, you can have BBS01 36V 25A or BBS02 48V 18A. The BBS02 runs at higher RPM, more suitable on flat roads - I prefer BBS01 with stronger torque at low speed for offroading.
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Deleted member 4366
Guest
Trex, you need to be more careful in recommending these crank drives. Please explain to be people the down-side as well as the up-side. Some people will read your posts and think that these BBS crank drives are some sort of ebiking panacea, which they're not. Don't forget also that your weight is a lot less than some of us, which makes a big diffetence in the perception of how the system behaves.
I cant find a BBS01 at 500 watts, can you put me up a link to one please so I can compare specs.
It may be better for my needs and slightly easier on the geartrain.
It may be better for my needs and slightly easier on the geartrain.
it's not on the woosh website yet.
http://www.alcedoitalia.it/shop/motori-centrali/motore-centrale-per-bici-elettrica-bafang-bbs02-36v-25a-500w/
Please note what d8veh said.
Note also that none of the forum members who have done the conversion with the BBS01 kit runs into any problem while there are plenty of threads about problems with hub kits.
D 8veh and Trex do argue about crank and hub drives.
Cranks are good and potentially more efficient.
They were the best for a number of years and the Panasonic held the crown for most of them.
Hubs are simpler and cheaper with a greater selection on the market.
Panasonic are an up and coming brand here now?
You must remember that power up hill costs watt hours, you get better performance with a high powered motor.
But a lot less range.
A lower power motor will keep going for longer with the same battery. And usually that will mean greater range even if you don't pedal much.
But here's my hobby horse. A legal motor can make you a super cyclist.
If you do have an incident an illegal one could stop you from claiming and even end up I front of the beak.
If you want to do +30mph with a range of over 100miles there are plenty of mopeds.
Cranks are good and potentially more efficient.
They were the best for a number of years and the Panasonic held the crown for most of them.
Hubs are simpler and cheaper with a greater selection on the market.
Panasonic are an up and coming brand here now?
You must remember that power up hill costs watt hours, you get better performance with a high powered motor.
But a lot less range.
A lower power motor will keep going for longer with the same battery. And usually that will mean greater range even if you don't pedal much.
But here's my hobby horse. A legal motor can make you a super cyclist.
If you do have an incident an illegal one could stop you from claiming and even end up I front of the beak.
If you want to do +30mph with a range of over 100miles there are plenty of mopeds.
I have hobby horses too, but the older I get the more I realise the real world is more relevant than my views. practically in a world in which car drivers regularly beat the speed limit and I have to travel ten miles a cross a 50mph road which I have to share with them (and that I want to spend as little time as possible on) and in which I feel in complete control of a (hydraulically brakes and on fat big apple tired) pedelecs at 20 or so mph I don't feel I'm exactly committing a UN war crime..i wouldn't recommend 30mph on a pedelec to anyone though