Bang on in every respect! It’s much like range, if only us manufacturers could agree on how power and range should be reported, we tried at BEBA but no one else seemed to be interested. I suppose it’s better for some to be selling smoke and mirrors?

my worry is older people who need a good motor to assist them on hill systematically look for a crank drive because they understand the usefulness of the gearing on bikes.

However, most of them have a problem with cadence. If they are in their 80s, they can't keep the cadence higher than 60RPM for long. It's difficult to convey to those who can't cope with a higher cadence that the power of a crank drive motor is proportional to the cadence and they would be better off with a geared hub motor and a cadence sensor.

my worry is older people who need a good motor to assist them on hill systematically look for a crank drive because they understand the usefulness of the gearing on bikes.

However, most of them have a problem with cadence. If they are in their 80s, they can't keep the cadence higher than 60RPM for long. It's difficult to convey to those who can't cope with a higher cadence that the power of a crank drive motor is proportional to the cadence and they would be better off with a geared hub motor and a cadence sensor.

 

I agree 100%. I find riding the Wisper Torque bike on my short commute far less tiring than riding the new Wisper HT mid motor. This is why we win so many sales over the Raleigh Motus for example, once people try both bikes the choice is easy... unless of course the rider has to climb very steep hills.

 

Both motor types have their place in the market. I am certain rear hub motors will gradually come back into fashion.

 

The throttle fitted to either system is a great advantage.

All you need to get up any hill is enough amps and a motor that won't burn when dealing with them. I've just been trying my 250W Bafang CST hub motor up a hill. It runs with 48v and 28 amps. It's the same weight as a Bosch, but it'll go up just about any hill twice as fast (subject to 15.5 mph limit of course), and pedalling is optional.

 

I too like the Wisper Torque for general riding around. Wisper should make a light weight hybrid version to take full advantage of that motor. Don't forget that every kg saved from the Torque means that it can go up a 1% steeper hill. At least 5% should be possible, so if the Torque can manage a 15% hill, the hybrid should manage a 20% one.

Edited March 2, 20197 yr by vfr400

Don't forget that every kg saved from the Torque means that it can go up a 1% steeper hill.

dodgy math?

if that proposition were true then the reverse 'every kg put on the bike means it can go 1% less steep hill' - put a baby seat and a baby on your bike, would the bike stop going up any hill?

 

The correct statement would be: if your bike can climb 10% then shedding 1kg will make it go 10% + 1% of 10% = 10.1%, not 11%.

dodgy math?

if that proposition were true then the reverse 'every kg put on the bike means it can go 1% less steep hill' - put a baby seat and a baby on your bike, would the bike stop going up any hill?

 

The correct statement would be: if your bike can climb 10% then shedding 1kg will make it go 10% + 1% of 10% = 10.1%, not 11%.

All up weight is approx 100kg, so 1kg makes 1% difference.

 

The formula for going up a hill is

 

Power = mass x gravity constant x dh/dt, wher h is the height and t the time.

 

Turn it round to get dh/dt = P/mg

 

That means that the rate of climb is directly proportional to power and inversely proportional to mass, i.e. a 1% decrease in mass will increase your rate of climb by 1%, or you could say that for a fixed rate of climb, if you increase mass by 1%, you have to increase the power by 1% to keep it the same.

All up weight is approx 100kg, so 1kg makes 1% difference.

that bit is correct, you are supposed to gain approximately 1% extra elevation, not 1% extra gradient.

But gradient is elevation divided by distance, so gradient is directly proportional to height, or for the same distance a 1% increase in height is a 1% increase in gradient.

But gradient is elevation divided by distance, so gradient is directly proportional to height, or for the same distance a 1% increase in height is a 1% increase in gradient.

let's say you climb a 10% gradient for 1km in 5 minutes. Your destination's elevation is 100m higher than your starting altitude.

If you carry 1kg extra weight, you'd slow down a little, after 5 minutes, your elevation suffers a little, you are at 99m higher than when you started.

What is the gradient if you rode the whole 1km? 9.9% or 9%?

let's say you climb a 10% gradient for 1km in 5 minutes. Your destination's elevation is 100m higher than your starting altitude.

If you carry 1kg extra weight, you'd slow down a little, after 5 minutes, your elevation suffers a little, you are at 99m higher than when you started.

What is the gradient if you rode the whole 1km? 9.9% or 9%?

In that example, the gradient is still 10%. With the same power and 1% less mass, you will have 1% less speed, so in the same time you will cover 1% less distance and 1% less height.

In that example, the gradient is still 10%. With the same power and 1% less mass, you will have 1% less speed, so in the same time you will cover 1% less distance and 1% less height.

you mean 1% more mass, 1% less speed.

OK, after 5 minutes, you ride 990m instead of 1km. Your elevation is 99m above your starting point.

99m/990m = 10%, not 9%.

That's right. To go up the same 10% gradient in the same time, you only go 990M, so to do the same 1000m up that 10% gradient, you have to pedal 1% harder, or, if you pedalled the same, but up a 9.9% gradient, you'd make the 1000m, which is where we started.

you said that if the bike is 1kg lighter, you can go up 1% steeper hill so 5kgs lighter = 5% steeper hill, eg from 15% to 20% which cannot be done by removing 5kgs. You'll need more power, removing weight is not enough. 5% weight reduction on a bike capable of 15% can only make it go up 15.8%, not 20%.

 

every kg saved from the Torque means that it can go up a 1% steeper hill. At least 5% should be possible, so if the Torque can manage a 15% hill, the hybrid should manage a 20% one.