Smaller motor

T

tomv

100 W
Joined
Jul 16, 2007
Messages
178
It looks like crystalyte is the king of diy battery kits. It also looks that their philosophy is bigger is better, which in many cases is just fine. Their 5 series motors have no match in go-fast department if matched to suitable battery.

After doing some driving on my 408 i came to realize that even that is way way more than i need, and the weight is unacceptable for me. I can't carry my bike over the stairs, into trains and subways.

So what are the options on the other side of the spectrum? What's the lightest hub motor that will give 300W continous 500W burst? Or to put it another way, what's the best motor that would allow my bike to stay within 50 lbs (25lbs bike, 15lbs LiIon battery, 10 lbs motor)? Anything that would be compatible with crystalyte controlers would be ideal!

I know that non-hub motors like cyclone kit or various curie bike designs have better power/weight ratio, but I'd much rather have sealed,clean,silent,reliable hub motor.
 
I also have a hunch that the higher the voltage the better power/weight ratio becomes. So let's assume that a 50-80V battery is available.

Illuminating case - Latest Prius uses DC/DC converter to step up voltage to over 500V. Motor has over 90% efficiency (umnatched in e-bikes even at most efficient rpm)
 
Look like P2B hub motor with 4.4kg from the site meets your needs.

http://www.users.bigpond.com/solarbbq/bikesale/bsale.htm
 
These include the controller etc. but the p2 series are light and will give great hill climbing assist as well. http://www.users.bigpond.com/solarbbq/bikesale/bsale.htm
What about the Puma? 8 something pounds? and brutually powerful by the reports from Knoxie.
 
The7 said:
Look like P2B hub motor with 4.4kg from the site meets your needs.

http://www.users.bigpond.com/solarbbq/bikesale/bsale.htm
Click to expand...

I forget the name of the manufacturer of schwinn's motors, and it might be the same as the one above. I haven't seen them in kits yet. I think each is good for about 250w continuous.

A cyclone type kit that drives through the regular chain would also be lighter.

Front hub motor:
http://www.schwinnbike.com/products/intbikes_detail.php?id=892
r_20.49.AS7_CAMPUS_M.jpg
 
if you're after a light motor - you can't go past the puma- $$$ but my god so much torque :)

p2b isn't bad eihter :) i have no experience or user reports on that one though.
 
xyster said:
The7" I forget the name of the manufacturer of schwinn's motors said:
Do you mean TongXin motor?
But TongXin motor uses roller type for planetary gear which is very weak when compared with teeth planetary gear in other hub motors (like P2B and Puma).
Click to expand...
Click to expand...
 
The7 said:
xyster said:
I forget the name of the manufacturer of schwinn's motors, and it might be the same as the one above. I haven't seen them in kits yet. I think each is good for about 250w continuous.
Click to expand...

Do you mean TongXin motor?
But TongXin motor uses roller type for planetary gear which is very weak when compared with teeth planetary gear in other hub motors (like P2B and Puma).
Click to expand...

Yah, the TongXin is the one I was thinking of. I didn't know that about the internal gearing.
 
xyster said:
Yah, the TongXin is the one I was thinking of. I didn't know that about the internal gearing.
Click to expand...

This is the roller type planetary gear.
 

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I keep reading how fragile the Tongxin is, but I still haven't broken mine yet. :) Probally will now.
They are silent and for the power very good torque, and mine has taken a pounding, lots of monster hills and the loacal MTB park (great fun with assist) but not a massive amount of miles.
I wish I could afford a lightweight battery pack as a sub 5 kg all up weight would be possible, the 12 kg of batteries I haul don't help the hpv side of things.
The Nano I think from different discussions is an improved Tongxin and the forerunner to the P2 series? but that could be completely wrong.
 
This covered somewhere on solar bbq's site, but basically the 2 nylon and 1 metal gives a quiter gear system with very close to the same strength as the all metal version for the stress's imposed.
The all metal is the ultimate in strength but at the cost of noise.
 
okay, I can accept that, but wouldn't making all three nylon be even quieter?

Anyway, a more important question for me is if nylon gears can withstand operating at minus 40 degrees without becoming brittle & shearing? I already have a big heavy hubmotor ebike & I'm scouting for something small & light for use in winter. Don't need speed over 15mph cuz you can't really. A geared motor with lotsa torque for plowing thru drifts & light for carrying for when you can't are the key ingredients. The Puma looks like it would do the job but it also has nylon gears so I would like the be certain if it will survive the freezing cold.
 
:arrow: This is the kind of argument I've been making.

Is 25 lbs "worth it" to get a hub motor that can deliver good performance?

Why not take a 500 watt motor and trick it out with double the voltage and maybe MCL (motor current limiting) to keep the heat down and (of course) add some gears. How about some forced air cooling as well to really make sure your motor will survive the extra power?

The choice becomes:

25 lbs for the hub motor

or

10 lbs (or less) for a small motor, 3 lbs for gears, so 13 lbs.

How valuable is a 12 lb weight savings?

How much do you spend on the battery?

In the end these decisions are subjective...
 
P2B is an geared hub motor which weighs 4.4kg (9.7 lb).
Direct hub motor of similar performance is about 6kg (13 lb).
 
The7 said:
P2B is an geared hub motor which weighs 4.4kg (9.7 lb).
Direct hub motor of similar performance is about 6kg (13 lb).
Click to expand...

By geared you mean "geared down" so that the fixed motor speed is higher. All that gives you is a minor 5% - 10% efficiency increase. To really get the most benefit from gears you need a gearing range of at least 200% from top gear to bottom and my calculations show that the maximum benefit it attained at 300% which is what I'll have on the next project. (Sturmey Archer 8 speed hub) For example, the typical derailler rear cluster goes from 14-28 and that's only 200%.

For any fixed motor (size and power output) you will always can get more with multiple speed hub gearing. A long time ago there was a thread where I proved that for any given motor there is roughly a 2 to 1 advantage to the geared (multiple speeds) bike over the fixed gear. You have to roughly double the power output of the fixed gear bike in order to equal the performance of the multiple speed bike.

:arrow: Which brings us back to the "small motor question" which is that you can get the performance you want with a really small motor if you:

1. Have Gears.
2. Overvolt it.
3. Force Air Cool it.
4. Change the controller to MCL. (optional)
 
safe said:
A long time ago there was a thread where I proved that for any given motor there is roughly a 2 to 1 advantage to the geared (multiple speeds) bike over the fixed gear.
Click to expand...

Would agree with you that multi speed could provide a better torque requirement for traction purpose over one speed gear.

That is why CVTs are mostly used in 50cc Vespa-type scooters.

There is an multi-speed geared hubmotor kit available for LSM as:
http://www.e-ride.ca/Electric_Motorcycles/MotConversion.htm
 
safe said:
:arrow: Which brings us back to the "small motor question" which is that you can get the performance you want with a really small motor if you:
Click to expand...

Theorectical, for the some power output;
Motor A running at 200 rpm; anf
Motor B running at 2000 rpm.

Motor A will be 10 times the physical size of Motor B.
But when reduction gear is used, the overall size difference is not that high.

Any gear ratio of greater 10 will cause the motor run at a too-high motor speed.
 
Miles said:
The7 said:
There is an multi-speed geared hubmotor kit available for LSM as:
http://www.e-ride.ca/Electric_Motorcycles/MotConversion.htm
Click to expand...

"Electronic gears" aren't quite the same thing, though...
Click to expand...

To my understanding, they are real mechanical gears which are controlled automatically by electronic means.
 
That's not my reading of this:

"The CPU estimates the resistance and continuously switches between the four electronic gears providing maximum performance with minimum consumption."

Have you any other reference apart from this rather ambiguous text?
 
Miles said:
That's not my reading of this:

"The CPU estimates the resistance and continuously switches between the four electronic gears providing maximum performance with minimum consumption."

Have you any other reference apart from this rather ambiguous text?
Click to expand...

What do electronic gears mean in your understanding?

Will email to ask the dealer?
 
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