Torque is meaningless. It's force that gets you up the hill and power that determines how fast you go up. Any motor in a 20" wheel will give 30% more climing force as it would in a 26" wheel.
Help! What COMPLETELY LEGAL Ebike will get me up hills?
- Thread starter Bike & Tina Turner
- Start date
It's just a bit difficult to get your head around the numbers.
For hub motors, the torque is measured at the wheel so the tyre diameter is important, the resulting climbing force at the point of contact with the road is inversely proportional to the radius of the tyre.
Smaller wheels correspond to greater climbing force.
Big wheels need big torque to turn, for the same wheel, More NM is better.
I can show you how to calculate the minimum torque needed to climb comfortably a steep hill if you like. You need the minimum speed (like 8mph), the total weight of you and the bike and the gradient of the hill. Subtract from that your own pedalling contribution, you'll arrive to what the motor must supply.
For crank drives, the torque is measured at the chainring and the resulting climbing force at the wheel is inversely proportional not only to the radius of the tyre but the front to rear transmission ratio too. It follows that crank drives can excel at hill climbing by good use of gears, having a small front to rear transmission ratio.
For hub motors, the torque is measured at the wheel so the tyre diameter is important, the resulting climbing force at the point of contact with the road is inversely proportional to the radius of the tyre.
Smaller wheels correspond to greater climbing force.
Big wheels need big torque to turn, for the same wheel, More NM is better.
I can show you how to calculate the minimum torque needed to climb comfortably a steep hill if you like. You need the minimum speed (like 8mph), the total weight of you and the bike and the gradient of the hill. Subtract from that your own pedalling contribution, you'll arrive to what the motor must supply.
For crank drives, the torque is measured at the chainring and the resulting climbing force at the wheel is inversely proportional not only to the radius of the tyre but the front to rear transmission ratio too. It follows that crank drives can excel at hill climbing by good use of gears, having a small front to rear transmission ratio.
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In this context the figure is quoted simply to convey the fact that the e20.8 model has more grunt than the near identical standard e20.7 model, in case that matters to the OP.
KISS.
According to @Nealh, my 19.2Ah battery with it's cheapo LG MH1 cells is capable of providing 25A continuous. My BMS is limited to 22A, and I need 1A for lights. I haven't had any need to increase controller amps from 15A yet, despite hauling heavy trailers up hills. I have yet to find a hill and/or hauling task which would require the BBS01B's max 20A. I'm certain @saneagle could list 250W rated hub motors capable of withstanding 20A to 30A coursing through their windings (he said as much recently on a thread somewhere), for legal hub motored Woosh Hill Slayers™. A stable of such beast pedelecs would be the envy of other manufacturers, and would fly off his bike racks, I reckon, judging by the many queries about hills we get on this forum from the:
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As saneagle said, torque numbers are meaningless. You need to specify a host of other details like power. yield and RPM. Manufacturers supply test charts to help with selecting the best motor for the job. I usually look for maximum torque for 180rpm at around 500w for my 26 and 700c bikes to run on 36V 16A controllers. Geared hub motors with similar size and weight tend to give similar maximum torque but some have higher yield than others so are preferrable. On bikes with a lower power controller like the Woosh Faro, I am looking for best torque and yield for 350W. 350W means I can go for a smaller, lighter hub motor like the Aikema 85SX, now 85SX(RC1). Aikema change the naming scheme of their motors a lot. The 85SX gives 42NM with 14A controller and 45NM with 16A controller.
There is one more factor that needs to be taken into account, the gear reduction ratio. The Aikema 85SX for example has two stage 11.5:1 reduction gearbox, much better at 80rpm than motors with the same maximum torque at 180rpm but with 4.5 reduction ratio because the yield at low speed is better with higher reduction ratio.
Maximum torque a complicated subject so take the advertisement at your risk.
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Nice looking bike that is similar to my own 20 year old hybrid bike, not wanting to hijack the thread but is your frame aluminium? Google says ali frames have a life span and should be replaced after 10-15 years, is this true?
My advice to the original poster would probably be to buy a new bike rather than convert her Raleigh, it would be a lot less hassle and a new purpose built e-bike should be more reliable, that said my bike suits my needs well plus I enjoyed doing the conversion and used it to familiarise myself with bike mechanics, also my bike has no problem with any hills!
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No, it's steel. It's no lightweight but is very comfortable to ride. I put that down to the curved forks and running relatively low pressures with the 26 x 1.95 tyres (40psi front, 45psi rear). The tyres are cheap Vittoria Easy Riders which have a shallow tread in the centre, and are surprisingly free running on tarmac. I've had it rolling at a sustained 20mph on the road, with electric assistance of course. If I push it any more with the pedals I "spin out" at around 23mph. Having said that, I prefer to look at the scenery so don't often run that fast.
I agree with your comments re-converting an older bike - I just happen to like tinkering at least as much as riding!
p.s. The bike cost me £35.00 on ebay.
We're going way off topic, but I can't fit anything bigger than 48t without hitting the chainstay, so I've kept the original triple crankset. I fitted a new Shinano 14-28T 7 speed freewheel and wasn't aware that DNP make an 11-28T - oh well!
i got a 52t on my bike but can sprint at 100rpm every road bike in ten years has been destroyed overtaking me is a act of war
Be careful, one time I racing a roadbike and just starting to win, when a bus came past at about 40 mph. The roadbike guy chose his moment and tucked in behind the bus, then waved at me as he disappeared into the distance at 40 mph.i got a 52t on my bike but can sprint at 100rpm every road bike in ten years has been destroyed overtaking me is a act of war
One thing I note is how light the person is. My daughter is currently using my old rear hub Oxygen Emate to commute to work and is a similar weight.
On a few practice rides we had together I was struck by how with my daughter riding the bike the performance and hill climbing ability of the old Oxygen had been transformed.
I was riding my crank drive Yamaha Haibike, a very capable hill climber and my daughter as an inexperienced cyclist in the wrong gear was flying up a steep hill that I could only just keep up with her using my high assist level. Bear in mind the Oxygen is cica 2011.
So a simple relatively cheap generic Chinese rear hub bike might be all that is required. Job done. Cheap to buy and easy to fix and replacement batteries that cost in the £165 to £210 range from a reliable recognized supplier like Yose when you need a replacement.
My old Oxygen is 12 years old and still working a treat. Now that is good value. Grandfather rights and an unrestricted throttle means that on the level she can sit there not pedaling with the throttle open trundling along around 18 mph.
As someone in the racing car business once said, "Add lightness and simplify".
On a few practice rides we had together I was struck by how with my daughter riding the bike the performance and hill climbing ability of the old Oxygen had been transformed.
I was riding my crank drive Yamaha Haibike, a very capable hill climber and my daughter as an inexperienced cyclist in the wrong gear was flying up a steep hill that I could only just keep up with her using my high assist level. Bear in mind the Oxygen is cica 2011.
So a simple relatively cheap generic Chinese rear hub bike might be all that is required. Job done. Cheap to buy and easy to fix and replacement batteries that cost in the £165 to £210 range from a reliable recognized supplier like Yose when you need a replacement.
My old Oxygen is 12 years old and still working a treat. Now that is good value. Grandfather rights and an unrestricted throttle means that on the level she can sit there not pedaling with the throttle open trundling along around 18 mph.
As someone in the racing car business once said, "Add lightness and simplify".
Really? Are we really saying the OP needs to know all that to grasp the basic difference between the Estarli e20.7 and e20.8?
The nm figure in Estarli's specification is a simpler, more easily digested comparative figure the layman might hope to grasp when comparing the two otherwise near-identical models. One version of the bike has more grunt/power/poke/hill-climbing ability (call it what you like) than the other; it need be no more complicated than that. Nobody knows what that's really like until they're ridden one/both; it's indicative, a relative comparator.
I'm sure Estarli have done their homework as thoroughly as you do.
Why do so many simple OP questions - asked in the OP's now deleted original post - need to descend into geek-fest monologues?
It's not the first time that torque figures are discussed. Saneagle has a clear view on this. I think although it's complicated, it is better to understand the physics (tyre radius, weight, gradient, speed, mass etc) so you can make better decisions. I don't know which motor the Estarli uses so can't comment there. In general, you need a 36V 17A controller for 50NM.
Very sorry, I evidently need new glasses.She
Your bike is in excellent condition. If you want to convert it, I would suggest an XF08C rear hub which looks very discret or a middle motor like TSDZ2 which has excellent natural ride feel. Email kits@wooshbikes.co.uk if you are interested.
My experience with the woosh xf08c kit https://www.pedelecs.co.uk/forum/threads/woosh-xf08c-cassette-with-rear-rack-battery.45406/
Motors are transducers. They don't have power. They give power according to how much power you give them. If you exchange a 250w motor for a 1000w one, you don't get any more power.
The same applies to torque. For any motor, torque is proportional to current, so there is no such thing as a 40nm motor. Give it 10 amps and it might make 20nm, and at 20amps it'll make 40nm.
Internal reduction ratios and wheel size are the two biggest factors that affect climbing force, where you're basically using the principle of levers to trade speed for force.
The reason we have to give explanations is because people don't understand how things work. If you don't understand, you can't make an informed choice, and these things normally start with a question about choice.
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