Advice for disabled rider on steep climbs - realistic?
- Thread starter stuck-indoors
- Start date
Some conflicting advice given here
My opinion- although not road legal, a bbshd conversion will deliver all the power you need. Simply drop down the gears to suit whatever the hill incline is
A hub motor will 100% splutter & stall at low road speeds
Your hard tail mtb could be suitable for bbshd conversion - let us know the make / model/ year
My opinion- although not road legal, a bbshd conversion will deliver all the power you need. Simply drop down the gears to suit whatever the hill incline is
A hub motor will 100% splutter & stall at low road speeds
Your hard tail mtb could be suitable for bbshd conversion - let us know the make / model/ year
I did suggest the Yamaha motor which mounted on the https://www.giant-bicycles.com/fr/explore-eplus-0-gts-2019 and with a 44-32 chainring replacing the original 48-36 would climb 20% gradients. Hey let's go the whole hog and replace the cassette with an 11-46 11 speed!
Here is the math:
http://www.kreuzotter.de/english/espeed.htm and http://www.bikecalc.com/gear_speed
A "roadster" (25 kg) with a 110 kg rider can climb a 20% gradiant with a road legal "250 W" motor @ 7.7 km/h. That would be 32 tooth chainring and 46 tooth bottom gear on the cassette.
So please explain "a road legal 250 W bike with a 110 kg rider can't climb 20% gradients" again... That requires 592 W at the wheel so the rider has to provide about 120 W. It sounds like the OP might not be able to provide that, I can provide over 160 W. So we just notch the gearing down a level, Sunrace makes an 11-50 11 speed cassette...
Here is the math:
http://www.kreuzotter.de/english/espeed.htm and http://www.bikecalc.com/gear_speed
A "roadster" (25 kg) with a 110 kg rider can climb a 20% gradiant with a road legal "250 W" motor @ 7.7 km/h. That would be 32 tooth chainring and 46 tooth bottom gear on the cassette.
So please explain "a road legal 250 W bike with a 110 kg rider can't climb 20% gradients" again... That requires 592 W at the wheel so the rider has to provide about 120 W. It sounds like the OP might not be able to provide that, I can provide over 160 W. So we just notch the gearing down a level, Sunrace makes an 11-50 11 speed cassette...
you can of course use gearing to help the bike but the scheme is limited by the climbing speed. A disabled person may need more than 4mph ground speed to stay on the bike. For practical purpose, you need to keep 10kph ground speed to ensure stability, 85kgs + 25kg bike, 20% gradient and 10kph requires 625W mechanical at the rear wheel. When you factor in the maximum assist ratio of popular torque sensing e-bikes, the rider is required to supply about a quarter of that requirement to climb the distance.
The fundamental consideration is how many calories a disabled rider can burn in a ride. 500 Calories? that limits how far he can ride and how much elevation is safe.
I’ve got a Big Bear. Now with rear wheel drive. It will take some beating on our very steep North Devon hills but i think you need an electric moped / scooter. Just slide onto it and away you go. Some have more pull than engine bikes.
Why have something with pedals if they’re not able to be used.
Why have something with pedals if they’re not able to be used.
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Thanks again for all the suggestions 
(even if none of you can agree with each other lol)
I'm going on a friend's turbo this weekend, with a power meter, cadence + heart rate monitor, so I'll have some real numbers to throw into the discussion. I suspect that my power output will be very low indeed - equivalent to a slow walk on the flat
(even if none of you can agree with each other lol)I'm going on a friend's turbo this weekend, with a power meter, cadence + heart rate monitor, so I'll have some real numbers to throw into the discussion. I suspect that my power output will be very low indeed - equivalent to a slow walk on the flat
Very true....
I have both the BBSHD and 02 conversions, you can put in as much or as little or nothing as regards effort - and the throttle is always there when you`ve had enough.
It's an On One Whippet X9 2013, carbon frame. SRAM X9 10 speed 11-32 on the rear.
Some people have said that a carbon frame isn't suitable for fitting a mid-drive motor like the Bafang?
Carbon bikes have too much carbon surrounding the ali BB, the material build up is to thick and won't allow clearance for any of the Mid drives to slide on , whether Bafang, Mxus, Tongsheng or GSM.
best conversion kit for it would be the 48V SWX02. It has both cadence and throttle control and optimised for hill climbing. Still, at your weight, 15% is the practical limit for climbing on throttle.
http://wooshbikes.co.uk/?hubkits#swx02-48v-kit
hi stuck indoors - welcome to the forumHi,
Just joined this forum, and I don't know any the jargon around ebikes. I'm disabled, and while I can 'ride' a bike, my heart rate has to stay very low. Basically I mustn't get out of breath, or start sweating, and there is no chance I'll be able to get 'fitter' through regular practice
Is it realistic to be looking for an ebike that will get me (85kg) up the steepest Peak District roads (up to 20%) with practically no effort on my part? just spinning the pedals? I don't care how slow it is, just so long as the bike can make it. (Walking up hill isn't possible for me either.)
Oh, and I have a couple of nice lightweight carbon bikes (road + hardtail MTB) from before I was disabled. Would I be better off looking at a conversion kit, rather than selling those bikes and buying a new ebike?
Many thanks for any advice from you experts!
Although limited to on road only check out the L1Ee-A options now coming online:
L1e-A | Rad Power Bikes Europe - Rad Power Bikes EU
You will have to check out the latest UK legal requirements to use these powered cycles on UK roads.
Registration | Rad Power Bikes Europe - Rad Power Bikes EU
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G
g_4909
Guest
Yep carbon bottom bracket rules out a mid drive motor
The metallic bolt on rear dropouts opens up the intriguing possibility of a rear hub motor - I’d still be wary of the huuuge low rpm torque needed to winch you up steep hills. A low rpm hub motor *may* be up to the job. Smaller diameter rear wheel (with shorter crank arms to avoid ground pedal strike) would help too
Well I managed to sustain 75W @ 60 rpm near the limit of my safe HR, which I'm really pleased withI'm going on a friend's turbo this weekend, with a power meter, cadence + heart rate monitor, so I'll have some real numbers to throw into the discussion. I suspect that my power output will be very low indeed - equivalent to a slow walk on the flat
very low of course compared to even an unfit healthy person, but better than I feared! I can pedal a faster cadence, but at lower power and 60 rpm felt comfortable.Going up what gradient and at what speed Stuck?Well I managed to sustain 75W @ 60 rpm near the limit of my safe HR, which I'm really pleased with
Or are we just assuming the 300% assist means 300W so you are fine in a low gear for any gradient?
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His safe gradient on Bosch CX or Yamaha PW-X kits is 10% @ 10kph.
Online calculator here:
http://www.kreuzotter.de/english/espeed.htm
total weight: 85kgs + 25kgs
total power: 300W (= 75W his + 3* 75W from motor)
gradient: 10%
speed: 10.3kph
Really useful thanks - and means it meets his 10% requirement - but won't your stall speed depend upon your lowest gearing?
It isn't always 10 kph is it?
http://www.shiftycycles.com/blog/2015/7/25/how-slow-can-you-go
Sustained 300W is elite athlete levels of power after all (although of course his total weight including bike will be much higher).
The linked calculator suggests a speed of 5 kph for a 20% gradient.
After all some mountain bikes have gearing so low that they won't stall at 3kph.
So if his gearing is low enough that he can keep his cadence up above say 40 and his HR in his safe zone, he should be able to get up most any hill in the Peaks. Or am I missing something?
At that moderate gradient he'd be better off with a powerful throttle controlled hub motor geared on the low side for 15 mph unrestricted and good low speed torque.
BPM or CST would be ok, but couldn't handle the steepest hills around 20% + without pedal assistance.
.
CD motors are optimised for 90 RPM, at 60 RPM, the maximum output of a Bosch CX or Yamaha PW-X is roughly about 70%-75% of their best.
Also, he is limited by the available gearing
10kph on 27.5" tyres = 10,000 /(2.15*60) = 78RPM at the wheels,
60 RPM at the chainring: gearing 1.3 front to rear ratio.
He will also need some margin if he is not in the best gear.
At 5kph, he'll run out of gearing or his cadence drops to 30-40RPM reducing the motor output further, and not stable enough to stay on the bike.
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