Can't decide which bike/motor to buy - Help me choose

[cwah]

I previously purchased an ebile, but it's way too big (25kg) and too slow (only 33 kph max speed). I can't even carry it in public transport so it's time to change!

I'm planning to change it to a faster (40-50 kph) and lighter bike (less than 20kg). I'm now narrowed to 3 choices, but I can't decide. So I'm asking for your advice.

Choice n°1:
Brompton bike + Crystalite 209.

Pro:
- Best of the best for folding bike
- Easy to carry on public transport
- Can go to groceries with my bike folded
- Regen possible

Con:
- Direct drive so it's a bit heavy. Motor is 3.9kg + controller weight will add a total of 5 kg.
- No freewheel
- Efficiency is lower with direct drive
- Not that stealthy because of the big motor visible

=> Bike without battery would weight around 17 kg (12kg + 5 kg) with a max speed around 45 kph.


Choice n°2:
Dahon uno + friction drive (can buy the one from Kepler or Adrian)

Pro:
- Quite stealthy
- Very light (1-2 kg added max for the motor + controller)
- Freewheel
- Good efficiency
- Motor is cheap to replace

Con:
- Can't work under the rain and that's a big issue because I live in london and it's often wet.
- Still a beta product
- Need to have a minimum speed of 12 kph before I can start the motor
- Limited speed (around 45 kph max)
- Most noisy

=> Bike without battery would weight around 12 kg (10kg + 2 kg) with a max speed around 45 kph.


Choice 3:
Dahon uno (same bike) + geared drive (BMC, mac or Cellman?)

Pro:
- Freewheel
- Can have good acceleration on start
- Better efficiency

Con:
- No regen
- Noisy
- Difficult to repair if there is any problem
- May not be possible to go very fast

=> I don't know too much about geared motor, so I'm not sure which one would be the best one for my need.

I have now a big dilemma, my first choice was the friction drive for the weight but as I live in London it may not be appropriate when it's raining. So among these 3, what would be the best choice for a commuter looking for a light and fast bike?

Thanks guys

 

[neptronix]

Friction drive eats tires. I would not say it is good for full-time use. Great for stealthyness or periodic usage, such as climbing a hill, though.

The Crystalyte you mentioned would probably be the most dependable motor of the bunch. I have not heard of a 209 motor however... do you mean 409? It's also not going to be too fast.

The MAC or BMC is going to be your fastest option, as long as we're talking about the 500w motor. A 6 turn MAC ( equivalent of BMC's "v3" ) on a 20in. wheel would net you up to 35+ mph with the right voltage, or more like 20mph-25mph on 36v.

If you run the 350w motor instead, you're probably looking at having power that's comparable to the small crystalyte. And you'll need to run over 36v on that wheel to go above regular bicycle speeds, for sure.

All hub motors have issues with the rain, unfortunately. And friction drive is by far the worst in the rain. coating the stator & magnets with red stuff may negate this, but i am not sure. You will have to research.

 

[cwah]

The crystalite 209 is a motor dedicated for Brompton:

http://www.crystalyte-europe.com/product.php?productid=16137

At 48V, it should be able to reach 45 kph (or 27 mph).

So I should choose a 500 W geared motor? What's the best between a MAC and a BMC motor? (I'm looking for a stealthy and efficient motor.)


I would also like to have a battery that's not too heavy for a distance around 25km or 15 miles. For now my bike uses around 12wh/km (or 7.5wh/mile), if I can keep these figures with the new motor that would be perfect.

 

[neptronix]

A ha...
The brompton has 75mm dropouts in the front.. that's a very odd size, and no MAC motor would fit that.
I bet the rear is something weird like 100mm, am i right?

The MAC/BMC style motors are designed for 100mm front, 135mm rear. Same with pretty much every hub motor as well.

That motor is really narrow, i'm now thinking it's not a very powerful motor at all.
It does depend on how fast you want to go, i guess. But i would say this bike is not a great performance platform.

 

[cwah]

I don't know what is the dropout size on the rear for the brompton. But as there is already a kit available for brompton in the front I didn't look at it.

I've just realised that the Dahon uno rear dropout is smaller than 135 mm because it is only single gear. I'll have to choose another dahon, probably a dahon speed or mu.

Now I'm thinking of a Bafang 48V500W. Is it the most efficient system? Can I overvolt it without problem? I'm hoping to reach 30mph for 15 miles. What battery should I get for that?

 

[Ykick]

I'm hoping to reach 30mph for 15 miles.

Safely? That will greatly depend on the road surface lottery...

To better flush out options you might want to provide your location and description of the commute you're attempting to navigate.

Do you really need a folder? If so, would a 24-26" wheel version work?

 

[cwah]

I need a bike I can easily carry on the tube or the bus. It doesn't matter if it's a 24 or 26'' wheel size. But I haven't found any standard size bike able to be carried easily on public transport.

I live in London, so space is a real problem and even taking the tube may be crowded. My commute is mainly on flat road, with a lot of red lights and sometimes a bit bumpy but I should accomodate. I would prefer acceleration over speed if the later is now too low

I've actually a full size foldable e-bike with a max speed of 22 mph but I'd like to travel bit faster. It's heavy (25kg) and I never had the courage to fold and carry it on the tube.

 

[Ykick]

Sorry, I missed your OP about London.

People have done sensible small efolders but they're fairly weird about dropout width and real estate to mount things like battery pack, controller, etc. Plus, small wheels suck on rough roads IMO... I'm in NYC rode 20" wheels for a short time before I decided to go bigger to help with pothole leverage.

So, your current folder - what type battery? Could it be improved to something lighter, faster, better?

 

[SamTexas]

Choice 3:
Dahon uno (same bike) + geared drive (BMC, mac or Cellman?)

Pro:
- Freewheel
- Can have good acceleration on start
- Better efficiency

Con:
- No regen
- Noisy
- Difficult to repair if there is any problem
- May not be possible to go very fast

I'm a satisfied owner of the cell_man's 350W front geared hub. Mine is NOT noisy at all. What's to repair? If the hub motor fails and you don't want to mess with it, just replace the whole wheel.

I don't think you can get to 45kph (28mph). The controller uses 50V capacitors so the max you can go is 12s lipo (44.4V nominal, 50.4V fully charged). That's what I did and the maximum speed is 34kph (21mph), no pedal assist. With pedaling I can get it up to 37kph. My bicycle is a MTB with 26" wheels.

BTW are you sure you want 45kph on a folder with smaller wheels? I know I don't.

 

[cwah]

I have now a full size folding bike:

250W Direct drive conhismotor with 36V10AH (heavy) frog battery. I have a range of about 27 km or 15 miles and my average consumption is 12 wh/km with a max speed of 33km/h (22miles/h). So I'm looking for similar range and something slightly faster.


I seen on the forum that geared hub motor have better efficiency. Some members go as low as 7wh/km at 35-40km/h. I'm hoping to have something similar. If it can go 45km/h at 10wh/km that would be perfect.

SamTexas, your actual bike speed is the same as mine with Conhismotor direct drive. What's the bike efficiency? And do you know think the Bafang 48V500W would reach 45-50km/h without using too much wh/km?

 

[SamTexas]

SamTexas, your actual bike speed is the same as mine with Conhismotor direct drive. What's the bike efficiency?

Here's the efficiency report I posted in another thread:

I do most of my tests on an 18 miles loop, starting and ending at my driveway. The road is mostly flat with occasional incline up and down to 3% grade. The loop is practically empty, and I have a wide bike lane. About 10 traffic lights (I have to come a full stop at half of them) and 4 or 5 stop signs. I was always pedaling and the throttle was used all the time, wide open whenever possible.

Top speed = 23mph (37kmh), avg speed = 17mph (27kmh), 8.54wh/mi (5.34wh/km). My bike is a rigid mountain bike with fat knobby tires (for suspension) pumped to 45psi.

And for completeness, here are the numbers for the same loop, with the motor doing ALL the work (absolutely no pedaling)
Top speed = 21mph (34kmh), avg speed = 14mph (22kmh), 13.34wh/mi (8.34wh/km)

On bike paths, my average speed is only 12mph and the energy consumption is very low, less than 3wh/mi. But that's because I was contributing at least 80% of the needed power.

And do you know think the Bafang 48V500W would reach 45-50km/h without using too much wh/km?

I have no experience with that hub. If you decide to use it, please report back on its efficiency once you've gathered sufficient data.

 

[cwah]

With the same speed on a mountain bike, your motor only uses 8.5wh/km. Mine uses 12wh/km. It's 40% more efficient than mine. That's why I want to change it to a geared hub motor!

 

[Ykick]

I've bought Conhismotors before and I don't remember ever seeing a DD that small? Unless I'm off my rocker, it would appear you've already got a geared hub motor.

 

[cwah]

hmm.. acceleration is very bad but I'm able to reach 33kph which is not bad for a 250W motor.

But if it's a geared motor, then I don't understand why my efficiency is so low.

ps: Actually it's maybe still a direct drive because I don't think many of us have a 250W motor...

 

[Ykick]

hmm.. acceleration is very bad but I'm able to reach 33kph which is not bad for a 250W motor.

But if it's a geared motor, then I don't understand why my efficiency is so low.

There's a lot more involved than simply "geared is more efficient". Different windings, wheels sizes, controllers, voltages, rider, wind, hills, etc. The list goes on and on...

Efficiency can and will be all over the map. I suggest you work with what you got and get equipped with the tools (CA, power meters, etc) to better understand and evaluate your particular needs. Then, build the end all, be all eBike of your dreams. In the end, you'll have what works well for you plus tools, practical knowledge and 2 functional bikes. Which is always a good thing to have on hand.

 

[cwah]

I already have a wattmeter in my bike. I use most of the time 12A at 36V. And I also know what I need:
- A small bike I can carry anywhere (bus/tube/train) but still fast enough for commuting.

I'm now thinking of buying a mac 500W high speed on a dahon speed. This seems to be the best compromise to date but I4m not sure so I'm asking for endlessphere community expertise :lol:

 

[cwah]

I may finally use the Bafang as it seems to be the lightest to be able to reach the required speed.

It would be the Bafang 500W48V at 201 rpm (high torque) with 3 Lipo winforce at 22.2V5.2AH because they are extremely cheap.

So I'd have a total 66.6V, a max speed around 40kph for a 20'' and autonomy around 15 km. Is it correct?