Fast Ebike for a tough commute

[niwrad]

I can see why regen braking can be unpopular. I am currently waiting for a fixed clutch geared hub motor to be available within the next 6 months to solve the weight problem, as the large direct drive motors are indeed heavy.

However as for pedaling with the motor off, I've done it a few times and it's honestly not that bad compared to no wheel, with the obvious problem of not being able to go 20+ mph. I've noticed that the increase in resistance tends to increase much more rapidly after 15 mph, but I've been able to maintain 15. With the setup I have my motor computer automatically decreases power draw so that the motor is always energized even at very low voltages, giving a constant 10-20 watts on what would be an otherwise dead battery.

With the motor controller I have, I have the option to add in "virtual freewheeling" which gives out about 25 watts at all times while the wheel is in motion, which actually makes it "freewheel" more than a plain wheel would be. The only downside I've noticed is that the motor is continuing to run even when I stop pedaling, and without the pedal and crank noise to mask it, I can just barely hear the whine of the motor at lower speeds like 5 mph.

I'm doing everything to mitigate the disadvantages and get my benefit; an 17% increase in range, which is just enough to get me through my commute. If I didn't have as much stop and go traffic, then I can see why this would be not as big of an advantage for other riders.

 

[matmaxgeds]

You are waiting for a different non-freewheel geared motor to this one? https://www.ebikes.ca/product-info/gmac.html

 

[thundercamel]

Anyone saying that you need 1000W to go 40mph must be sitting straight up and riding like they're on ape-hangers.

Grin's motor simulator says that the load to go 40 mph on a full recumbent is 978 watts. A road bike set up for commuting is very unlikely to be that slippery. The simulator gives a load of 1355 watts for 40 mph on a semi-recumbent. If you are a very strong cyclist and can output 355 watts, that means the motor system still has to supply 1000 watts.

OTOH, bikecalculator.com says that on aero bars you can go 40 mph with "only" 904 watts of power. But that's a pretty iffy position for commuting. For drops the same calculator gives 1143 watts.

So no, one need not be sitting upright riding like they are on ape-hangars to suggest that they need 1000 watts to go 40 mph. They only need to have a bit less than optimal drop bar position, non-skinny tires and not have the ability to output more than 250 or so watts on their own. In other words, in the vast majority of real world situation most people really do need about 1000 watts of motor power (more battery power) to go 40 mph for any time longer than possibly a short burst of speed. There are only a very few exceptional situations (discounting going downhill or falling out of an airplane) where you don't need 1000 watts to get to 40 mph on a bicycle. It is a pretty realistic generalization.

It is true, however, that if you are an exceptionally fit rider and build a lightweight road e-bike with a small geared hub motor, that you can get by with a lot less battery and motor power. There are at least two threads on this forum that have outlined exactly those kinds of builds. (https://endless-sphere.com/forums/viewtopic.php?f=3&t=49691#p734494)
But even an exceptionally fit rider isn't likely to sustain 300 watts of output for for very long. But 200 watts or a bit more is realistic. And with that you can maintain speeds around 30 mph for extended periods with just 300 watts of added motor power - assuming you have a really good aerodynamics.

The OP posted a Strava track of his 30 mile commute. He averaged slightly better than 16 mph over that distance while having to do a fair amount of climbing - though his net elevation gain was less than 200 feet. This plus his yearly mileage tells me that he's an avid, fit, but probably not elite-amateur level rider. I'd bet he can sustain 200 watts for extended periods which is well above typical. Even so, the notion that he needs about 1000 watts of assistance to go 40 mph for any significant distance applies to him as well.

Well said, wturber

 

[mystryda]

Anyone saying that you need 1000W to go 40mph must be sitting straight up and riding like they're on ape-hangers.

There are only a very few exceptional situations (discounting going downhill or falling out of an airplane) where you don't need 1000 watts to get to 40 mph on a bicycle. It is a pretty realistic generalization.
The OP posted a Strava track of his 30 mile commute... do a fair amount of climbing

Well said, wturber

Look guys, we're talking past each other. The OP said he wanted top speed of 35-40 mph. He route has lots of hills. I'm talking about going downhill. wturber's talking about everything except going downhill.

"Top speed" and "top speed in the flats" are very different things. Any respectable cyclist can hit 40 mph while tucked on a regular road bike on something around an 8% grade; sit straight up--ape-hangers in my language--and he'll have a hard time crossing 30mph on the same descent.

But this doesn't mean that the OP is asking a meaningless question.

If he picks direct drive motor that's optimized for climbing then my understanding is that the motor will arrest his speed, much like engine breaking with a manual transmission; the model I ran on Justin's simulator shows the MAC 12T motor topping out around 24mph with 36V, 30 with 48V. Please correct me if I'm wrong.

If he wants that top speed--yes, going downhill--then I think he is confined to three choices: a geared hub motor, a mid drive, or a fast winding direct drive (like a MAC 8T @ 48V or MAC 6T @ 36V). [I'm not recommending the MAC motors, I'm just giving examples from the simulator.]

 

[MadRhino]

Come-on. I am going downhill 9 grade 80 mph with a 4t DD hub. I climb avg 9 grade at 50 mph for miles.

A fast commuter is best built with a big DD hub and RC lipo. Otherwise it will be heavier, more expansive, more maintenance.

 

[niwrad]

You are waiting for a different non-freewheel geared motor to this one? https://www.ebikes.ca/product-info/gmac.html

Yeah, I emailed Justin already. I need the Brompton version, the one listed is used with standard 10cm dropouts but I need their narrow motor

 

[wturber]

Look guys, we're talking past each other. The OP said he wanted top speed of 35-40 mph. He route has lots of hills. I'm talking about going downhill. wturber's talking about everything except going downhill.

When someone talks about top speed and doesn't otherwise qualify things, the assumption is usually level ground and no head or tail wind. The assumption isn't downhill ... or uphill unless there is some clear reason given or implicit in the context. My heavy rather commuter routinely breaks 35 mph (and would probably go faster if I didn't hit the brakes a bit) with me sitting fully upright and going downhill ... and using zero watts. But that is a characteristic of the hill more than it is of the bike.

 

[mystryda]

When someone talks about top speed and doesn't otherwise qualify things, the assumption is usually level ground and no head or tail wind. The assumption isn't downhill ... or uphill unless there is some clear reason given or implicit in the context.

Thanks for explaining. I'll keep that in mind going forward.

 

[FiberOptic]

And... if you really think about fast e-bicycle to Ride and NO "e-moto" or e-bike with throttle only - you should think about transmission.
for 40km'h for comfort pedalling with PAS you need at least 12x53t transmission ratio. and 11x58T for 50km.h
And need to research the motor-wheel and voltage. most wheels can't be faster 40km h even for 2kw controller and 48V. you will need to increase voltage.
\most stocking electric bikes has small front chain ring -7speed rear googs. and motor that can't ride fast at this current voltage.
you can increase voltage withut problems. most controllers take +40% voltage increasing

 

[Jil]

for 40km'h for comfort pedalling with PAS you need at least 12x53t transmission ratio. and 11x58T for 50km.h

All depends on your wheels.
My Surly Krampus has 29x2.5" tires, with 38x11 transmission I pedal comfortably (95 rpm) @ 45 kph.

I can see why regen braking can be unpopular. I am currently waiting for a fixed clutch geared hub motor to be available within the next 6 months to solve the weight problem, as the large direct drive motors are indeed heavy.

I have installeld today a GMAC 8T on my Krampus, I can confirm the regenerative breaking is effective.