Q: How much resistance when motor is OFF

Electrically assisted bikes, trikes, etc.
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natmat
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Q: How much resistance when motor is OFF

Postby natmat » 6 Oct 2017, 2:41pm

Hello all,

Just seeking observations from others here...

I've a ShimanoSteps mid-drive system. When it's OFF there is some, a little but noticeable, resistance from the motor.

It's barely noticeabl if I'm pedalling slowly, but start pedalling quicker/harder and it becomes significant - almost the feeling of cycling on flat and more like treacle than free spinning. Whether it's because I've had assistance then switched it off and it feels like hard work (as jumping up and down does after being on a trampoline?) without those bonus Watts I don't know. Pedalling backwards is fine, has no resistance whatsoever. I'll try riding the bike OFF from the start and see if I've just answered by question.

Nathan.

Marc
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Re: Q: How much resistance when motor is OFF

Postby Marc » 6 Oct 2017, 4:51pm

I don't use a mid drive, but geared hub motors (Bafang SWXH '250W'/2.7kg and BPM '500W'/4.6kg versions) and a 5.5kg direct drive hub motor (MXUS XF40, similar to a 9Continent DD hub).

The geared hub motors with their internal 'freewheel clutch' have barely perceptable or no resistance.
When I put the little Bafang SWXH in my trike, I could only feel the difference to a 'normal' rear wheel for a day or two. Geared hubs are the ideal choice if you only use motor power to flatten-out hills.

The cogging of the direct drive hub motor is clearly perceptable on the other hand. The resistance of the direct drive is roughly comparable to an underinflated Marathon Plus tyre: Ok if you are peddaling along at low speed, but annoying and power sapping if you try to pedal at a brisker pace.
The DD hub is mounted in my commuter trike, but I would hate to pedal it the 30km back home without power.

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[XAP]Bob
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Re: Q: How much resistance when motor is OFF

Postby [XAP]Bob » 7 Oct 2017, 7:18pm

Don't notice any from my hub motor
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natmat
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Re: Q: How much resistance when motor is OFF

Postby natmat » 7 Oct 2017, 8:06pm

Interesting comments, thank you.

Today I rode with my Steps is OFF mode from the start. It just felt like a normal, if heavy, bike. However, switching off after having it on, still feels odd. So I conclude it's the lack of Steps power that makes it feel odd, not any friction/resistance in the motor. So I think the perceived 'pedalling in treacle' feeling is a consequence of switching the power-assitance off. I wonder if the steps actually starts to apply extra power/torque just before the top of the crank rotation, or rather just before point in the rotation where I could physically start applying power.

I haven't yet had a chance to use a rear/front hub motor... so can't comment on whether that feels any different.

As an final comment, the Steps system is REALLY impressive! After buying this bike out of curiosity, I now have no intention of selling it.

N.

reohn2
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Re: Q: How much resistance when motor is OFF

Postby reohn2 » 8 Oct 2017, 8:53am

Glad you're having such a positive experience with your Steps system,other than when switching off.
The only thing I can think of is it still having to turn an idling geartrain within the Steps unit,though the ressistance would be minimal it's felt by the rider.
How long have had the bike,what's the battery size and what kind of mileage do you get from a charge?
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natmat
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Re: Q: How much resistance when motor is OFF

Postby natmat » 11 Oct 2017, 8:59pm

reohn2 wrote:Glad you're having such a positive experience with your Steps system,other than when switching off.
The only thing I can think of is it still having to turn an idling geartrain within the Steps unit,though the ressistance would be minimal it's felt by the rider.
How long have had the bike,what's the battery size and what kind of mileage do you get from a charge?


So, I now conclude there's no friction when the power is off. It's just that after cycling powered and then switching it off, the difference is marked, but it's not because of any friction that I can detect.

Had the bike about a year. It's the standard 400W Li-ion. Charged the battery indicates a range of 40-55 miles (EcoNormHigh). I've managed 60 miles on a charge, at Eco, pedalling leisurely. I've also managed only 30 miles pedalling hard. Charges from flat to full in about 4hr.
I alternate cycling and cycling daily, so I use it for either 40 or 60 miles per week.

The best thing is it doesn't detract from unpowered cycling, which I still enjoy. However, the grin still has't worn off as I whir up the hills.

hemo
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Re: Q: How much resistance when motor is OFF

Postby hemo » 16 Nov 2017, 10:02pm

The treacle feeling is just the extra weight of the hub and is centrifugal, if that extra mass was evenly distributed at the circumference of the wheel it wouldn't be so bad, but as the mass is central at the axle it is a heavier dead weight to move unpowered. Low gearing is needed until you are rolling then you should be alright once in to double figures mph. The real effort needed on inclines with out power.

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natmat
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Re: Q: How much resistance when motor is OFF

Postby natmat » 17 Nov 2017, 9:27am

hemo wrote:The treacle feeling is just the extra weight of the hub and is centrifugal, if that extra mass was evenly distributed at the circumference of the wheel it wouldn't be so bad, but as the mass is central at the axle it is a heavier dead weight to move unpowered. Low gearing is needed until you are rolling then you should be alright once in to double figures mph. The real effort needed on inclines with out power.


Not, it's not the hub. The Steps is a mid-drive so the motor is "integral to" the bottom bracket assembly and drives the rear wheel via the chain, rather than the rear wheel housing the "engine". The bike therefore does not have a hub motor. In fact it has standard rear wheel/hub, not a NuVinci.

hemo
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Re: Q: How much resistance when motor is OFF

Postby hemo » 17 Nov 2017, 9:49am

My error didn't read the post correctly.
My bbs01 is similar when unpowered the slight resistance is probably down to the internal gearing, though like a hub you are still riding a bike that is heavier and weighs about the same with a battery as well.

kwackers
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Re: Q: How much resistance when motor is OFF

Postby kwackers » 17 Nov 2017, 10:01am

I find turning the motor off very odd.
I'm now so used to how it feels when I start peddling that without it the bike feels heavy and wooden. Interestingly this feeling is most prevalent on initial start and falls off quickly.
I don't think there's any obvious drag from the motor (bafang mid drive), certainly nothing worth worrying about.

It can be very odd sometimes as you approach max speed or max peddle cadence and the motor starts to drop the assist as you provide more. Almost like a cliff edge. It can actually feel harder to get past than turning the assist off and doing it manually!
Another weird feeling is travelling at the limit and hitting a hill, the pedals actually get lighter as the motor takes over the strain which is very odd (the bike obviously slows enough for the motor to kick back in), something similar in reverse happens at the bottom of hills too.

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natmat
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Re: Q: How much resistance when motor is OFF

Postby natmat » 17 Nov 2017, 11:12am

I agree with the odd sensation when power tails-off/stops at the limit. On more than one occasion I've stopped to check that I don't have a puncture.

When cycling on the Eco setting I am providing sufficient power (i.e. input power on the cranks) to ensure the motor is running at it's Eco-level-max (I think that's about 80W). And because it's so constant when it disappears it exaggerates my (and probably anyone's) eccentric pedalling effort-profile.