A bike for 'Eddy' - just for starts and steep hills?

Crankwinder

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May 25, 2023
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This time I really am 'asking for a friend'. My friend - let's call him 'Eddy', not his real name but he'd like that - is fundamentally a very strong rider, who regularly rides more than 100 miles in a day and goes like a locomotive on flat or undulating roads (where the rest of us form up like carriages behind) but struggles on climbs due to a gammy right leg. Eddy's left leg does it all really and once he's up to speed momentum keeps him rolling. But gravity sucks :(. Drag increases, momentum decreases and eventually Eddy stalls between left pushes. And once Eddy stops, he cannot easily re-start.

Starting is dodgy enough at any time or place for Eddy: his right leg can neither push the pedal down hard enough, nor provide a steady prop to stand on while his left leg does the job. On a hill his only option is to point the bike downhill then do a U-turn. Not very safe - and Eddy really does not like to stop at junctions, for a much better reason than most of us have :oops:!

Eddy's recently got an E-bike and it helps keep him moving uphill, but on anything much over 15% (1:7) the motor stalls too. And here's another thing: we ride in the Derbyshire Peak District, where the hills are fiercely steep. It's just too route-limiting for us to avoid the double arrows that Ordnance Survey sprinkles generously over our local lanes - indicating 20% and even steeper gradients!

This E-bike (it's a Ribble) has a Mahle hub-motor. I guess the current and torque increase the slower it rotates, but only up to a point and surely that drains a battery faster than a motor that keeps spinning at its most efficient rpm? I'm thinking Eddy would do better with a bottom-bracket drive, where both rider and motor get an easier and more efficient ride when a lower gear is selected. And the Mahle system does not offer start-assist, not at all. I know, I asked Mahle if a different controller was available that did that, but no. So I'm wondering, does Fazua offer start-assist? Or is there another super light and efficient 'stealth' e-bike system that does?

What would anyone recommend for my impressive friend? Remember, Eddy can go faster on the flat with his one good leg than most of us can with two. He doesn't need any help with that, just for starting and the steep stuff. And it's still got to look and ride just like a pure muscle bike. Nothing less will do for our Eddy :cool:.
 
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soundwave

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matthewslack

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Tricky! A mid-drive with enough torque and appropriate gearing will get Eddy up any hill, but will not ride easily enough turned off to exceed 25kph most of the time, and won't do the 100 miles turned on.

A beefier hub motor will be a very different riding experience to the Mahle, and may still not manage the steepest, longest ascents. It would ride without resistance above 25kph, however.

I think I'd be looking at two big batteries and a best compromise mid-drive, but to ride at the unassisted speeds eddy current ly enjoys it would have to be a 45kph speed pedelec with the unwanted requirements that would bring.
 

soundwave

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guerney

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How heavy is Eddy? Does he look like this guy?

 

Woosh

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A TSDZ2B with 48V15AH would do it. Very low consumption on the flat and strong enough on hills.
 

AntonyC

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It sounds as though a throttle's almost essential for hill starts and your TSDZ2B has that, with wide range gearing it seems ideal.

Alternatively, two hub drives? Very roughly, if Eddy can climb say 6% by momentum, 22% would need two motors/controllers fit for 8% each. Reduced cooling at slow speed would be offset by having double the motor mass and surface area, and so long as the steepest sections are short maybe 'excessive' current or more discrete motors would be possible.

Granted this would only deliver a <<16% hill start.
 

Woosh

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The key advantage of the TSDZ is its very low battery consumption when human power is already near enough to maintain the speed.
 

Crankwinder

Finding my (electric) wheels
May 25, 2023
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The key advantage of the TSDZ is its very low battery consumption when human power is already near enough to maintain the speed.
Eddy's really looking for a ready-made E-bike with battery discreetly stowed INSIDE the frame, not a conversion.
 

soundwave

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matthewslack

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Eddy's really looking for a ready-made E-bike with battery discreetly stowed INSIDE the frame, not a conversion.
Eddy will need to test ride a likely contender from each of the system manufacturers on a realistic route.

The important part is the second half, when not fresh, and the important test is (a) riding above 25kph with assistance having cut off and (b) turning off assistance for the last 10 miles to simulate running out of battery.

No point making these assessments with fresh legs in a quick turn round the block.

Try Shimano EP8 and E6100, Bosch Performance Line and Performance Line CX, and equivalent Yamahas, I don't know their models.

I don't know of any hub motor contenders: is there a higher spec Mahle?

Having ridden a few mid-drive bikes from all three big names, my recollection says there is nothing that satisfies the requirements.

The only other avenue, which is probably not what is wanted, would be a slow wound hub motor in a 20" wheel on a trike. This would have a lower maximum assistance speed and better hill climbing by about 50%, and zero drag unassisted. But would still need verifying on the hills.

Otherwise it's back to the 45kph Bosch Performance CX speed pedelec.
 
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guerney

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Eddy's really looking for a ready-made E-bike with battery discreetly stowed INSIDE the frame, not a conversion.
That's a real shame, because a cadence based 250W BBS01B with throttle conversion of a decent bike would fit the bill. Eddy wouldn't need to exert as much force with his weak leg, using a cadence based system. The last thing I want from my bike is exercise, which is why I use a BBS01B. I don't know if the current limit of a 48V BBS01B controller can be increased, but the 36V controller's limit can be set to 20A, (haven't read any reports saying otherwise - it certainly can on mine), battery capability permitting. And with a kit, @Woosh has said that the law doesn't apply to throttles on conversions:

https://www.pedelecs.co.uk/forum/threads/build-spec-by-committee-might-that-include-you.45773/page-3#post-688195


He's a big guy, but mostly bone and muscle.
Even if Eddy was mostly fat and yet more fat like that guy, he could fit a smaller chainwheel on his BBS01B conversion.
 
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Woosh

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Eddy's really looking for a ready-made E-bike with battery discreetly stowed INSIDE the frame, not a conversion.
a ready made e-bike won't help him much with hill start.
 

AntonyC

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So at the moment OP's friend aims to find and make do with the OTS ebike that helps the most. Is he at all open to designing the built up bike that helps him the most, or the most discretely?
 

Crankwinder

Finding my (electric) wheels
May 25, 2023
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So at the moment OP's friend aims to find and make do with the OTS ebike that helps the most. Is he at all open to designing the built up bike that helps him the most, or the most discretely?
Maybe. It depends on what you had in mind exactly. A requirement to hide the battery inside the frame however, seems to rule out conversions.
 

saneagle

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They always start off with a simple problem that's easy to solve, then put so many constraints on it that it's impossible to solve.

Go and have a word with Eddy and tell him to get real.
 
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soundwave

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they did make a bike with hidden motor and batt in the frame but was stupid expensive and not alot of power thus they went bust
 

guerney

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Maybe. It depends on what you had in mind exactly. A requirement to hide the battery inside the frame however, seems to rule out conversions.
I like my big detachable battery - 19.Ah, so voltage sag doesn't impede tackling any hill, even while hauling a heavy bike trailer. If I ever do leave my bike locked up in a public place (I don't, because my bike folds so I take it into workplaces, and into supermarkets via shopping trolleys etc), my bike will be less interesting for thieves. I can reduce the weight of my bike before heaving it onto trains, by removing the battery and placing it in my rucksack. It's easier and cheaper to diagnose problems, repair or replace.
 
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Crankwinder

Finding my (electric) wheels
May 25, 2023
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I've been crawling over Fazua's website and it looks like their latest 'Ride 60' system (but none hitherto) has what Eddy needs, namely a 'Boost' function (see p30 of this pdf manual) that provides up to 4 seconds of 450W power from standstill. That should be enough to start up any hill, while he gets into the saddle and transfers his good left leg from ground to pedal. Provided he's selected a suitable gear of course. But as this model also has 'Push Assist' (p31), gear selection can be sorted by walking a short distance in that mode whilst leaning on the bike and operating the shifters. So: we've just got to find a nice E-road bike equipped with Fazua Ride 60. I've got a feeling it won't be cheap! A test ride will still be needed to check that one gets a full four seconds of Boost before one has necessarily pedalled a full circle.