Need advice from someone with experience peddling a Direct Drive hub motor without power vs peddling the geared drive without power. My plan is to power a Bob trailer to assist on hill climbs and headwinds. I realize the direct drive will have some drag, but is the drag minimal and the regenerative braking and charging worth the extra drag? Or, does the reduced weight of the motor and no drag peddling without power on a geared motor outweigh the direct drive?
Direct Drive or Geared motor for Bob-Trailer drive
- Thread starter Geezer
- Start date
Eclectic
1 kW
A direct drive motor is very reliable and simple but it does pretty much require power to it all the time. I do not like trying to pedal my bike without power for more than a few hundred yards. Regen works very well for braking but normally does not add that much extra mileage unless you have unusual circumstances. Geared motors have freewheels so they have very little extra drag when unpowered. Geared motors are more complex, noisier, more parts to break but because of their gears, they tend to be more efficient on steep hills.
You probably won't get much in teh way of braking on it unless you have significant weight on there--the wheel may just lose traction.
Same is true of drive power--if you have a lot of torque without enough weight holding it to the road, the wheel may spin if you suddenly apply it at a low enough speed.
A good DD motor, well-made, doens't have much resistance when unpowered (though there is still some, and you'll probably feel it).
A good freewheeling geared motor, well-made, does still have some resistance when unpowered, though not very much, and is significantly easier to pedal than a badly-made/designed DD motor, and still noticeably easier than a well-made one.
I can feel a definite difference between the typical "9C" type DD motor, and either the older or newer Fusin geared hubs I have. THe older Fusin and a 9C were each used on DayGlo Avenger, with the 9C being harder to pedal the faster I went, though not that much difference at low speeds. The newer FUsin was about teh same as the older, though used on a different bike (and later a trike).
I did not test this, but I expect that with the controller's phase wires disconnected from the motor, (or the battery from the controller) it would be easier to pedal at higher speeds.
Speculation: Depending on which setup, the geared motor, for the same wheel and motor size, controller, and battery, may have higher torque than the DD, so you might have to apply it more slowly than the DD to prevent wheelspin.
Either way, it depends mostly on what you want out of it.
Same is true of drive power--if you have a lot of torque without enough weight holding it to the road, the wheel may spin if you suddenly apply it at a low enough speed.
A good DD motor, well-made, doens't have much resistance when unpowered (though there is still some, and you'll probably feel it).
A good freewheeling geared motor, well-made, does still have some resistance when unpowered, though not very much, and is significantly easier to pedal than a badly-made/designed DD motor, and still noticeably easier than a well-made one.
I can feel a definite difference between the typical "9C" type DD motor, and either the older or newer Fusin geared hubs I have. THe older Fusin and a 9C were each used on DayGlo Avenger, with the 9C being harder to pedal the faster I went, though not that much difference at low speeds. The newer FUsin was about teh same as the older, though used on a different bike (and later a trike).
I did not test this, but I expect that with the controller's phase wires disconnected from the motor, (or the battery from the controller) it would be easier to pedal at higher speeds.
Speculation: Depending on which setup, the geared motor, for the same wheel and motor size, controller, and battery, may have higher torque than the DD, so you might have to apply it more slowly than the DD to prevent wheelspin.
Either way, it depends mostly on what you want out of it.
aroundqube
10 kW
- Joined
- Mar 12, 2012
- Messages
- 577
I have a 9C direct drive 2810 rear 29er. I do not notice any drag , even going up hill in granny gear,on pedal only with ( bad ) battery LVC and controller connected. At about 10 mph CA screen lights up and reads 17V ( regen ?? ). No problem riding at low speed. There is some development on a BOB looking trailer going on here ; http://endless-sphere.com/forums/viewtopic.php?f=31&t=63257
Chalo
100 TW
Geezer said:
Drag costs you speed and pedal effort whenever the motor isn't driving. Avoid it as much as possible, unless you intend to be on the juice 100% of the time.
Another thing to consider is that you're using a 16" wheel, and there are more geared hub motors that will fit into your rim than there are DD hub motors of suitably small diameter. I laced a relatively small DD hub to a 16" rim once, and it used the very shortest spokes I could find anywhere.
You'll need a relatively high RPM, low current motor/controller combination, to offset the small wheel diameter and to keep the torque moderate. With little weight on the driven wheel, you can only use so much push before you get wheelspin.
dogman dan
1 PW
Just because of the small wheel size, it could be best to go with a smaller diameter geared motor. And if you plan on lots of pedaling with power completely off, you need the internal freewheel in a geared motor.
On the other hand, it takes only a tiny bit of power to eliminate the drag from a DD motor. at 50 watts, you aren't using up much battery capacity to reduce the drag.
On the other hand, it takes only a tiny bit of power to eliminate the drag from a DD motor. at 50 watts, you aren't using up much battery capacity to reduce the drag.
LegendLength
100 W
I had a 9c and the drag made it virtually impossible to ride without power. It was like riding an exercise bike with high resistance. So I find it hard to understand your claim.aroundqube said:
chvidgov.bc.ca
10 kW
My 9C with some controllers has considerable resistance. Other controllers give very little. It varies quite a bit between controllers. It also helps to turn the controller off completely, in many cases, compared to leaving it powered on with very minimal wattage going to it.
ScooterMan101
1 MW
I had considered making a " Pusher Trailer " using a B.O.B. trailer a couple of years ago, but decided not to do it since it is too small , and too wobbly for my dog.
You have some good answers above about Hub Motors,
So ,
I will talk about the trailer itself.
First will you be using a YAK, or the IBEX trailer from B.O.B. ?
Do you already have the Trailer ?
I saw and talked to a man up at Lake Tahoe a few years back , who lived each summer/camping out of his , Homemade Copy of a IBEX trailer , ( no car / van / rv ) , it was bigger and could handle more weight than the commercial B.O.B. trailers .
B.O.B. and your local Bike Shop can sell you the Axle and Fork , then you can make your own rear, that way you can add suspension, and , use a larger 20 inch wheel.
Also, have you done your homework about the problem of " Jackknifing " ?
I promised myself that If I ever did use a pusher trailer , that I would let , Off , the Throttle before each corner, and just use power on the straights .
You have some good answers above about Hub Motors,
So ,
I will talk about the trailer itself.
First will you be using a YAK, or the IBEX trailer from B.O.B. ?
Do you already have the Trailer ?
I saw and talked to a man up at Lake Tahoe a few years back , who lived each summer/camping out of his , Homemade Copy of a IBEX trailer , ( no car / van / rv ) , it was bigger and could handle more weight than the commercial B.O.B. trailers .
B.O.B. and your local Bike Shop can sell you the Axle and Fork , then you can make your own rear, that way you can add suspension, and , use a larger 20 inch wheel.
Also, have you done your homework about the problem of " Jackknifing " ?
I promised myself that If I ever did use a pusher trailer , that I would let , Off , the Throttle before each corner, and just use power on the straights .
LegendLength
100 W
Ahh i forgot that. I was running 72 volt with a lyen 12 fet controller so that might have been it.chvidgov.bc.ca said:
