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Old 08-12-2020, 09:12 PM   #11 (permalink)
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Road bike hub conversion

What about using the bicycle hub that has the coast clutch built in?

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Old 08-13-2020, 10:55 AM   #12 (permalink)
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Why even care if the motor spins or not? Not looking at a lot of power consumption on a freewheeling armature if the field is disconnected, just bearing and drive gear loss.
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Old 08-14-2020, 01:17 AM   #13 (permalink)
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Quote:
Originally Posted by freebeard View Post
With twin motors you get torque vectoring. My previous reply explained the spur gear differential in the golf cart axle.
Either with twin motors and torque vectoring or a single motor and an actual differential, still makes more sense than having only one driven wheel. But it's also worth to consider how to eventually provide an effect analogue to a differential locker, which is useful even for city driving sometimes such as starting uphill from a standstill in a rainy day.
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Old 08-14-2020, 05:53 AM   #14 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
Why even care if the motor spins or not? Not looking at a lot of power consumption on a freewheeling armature if the field is disconnected, just bearing and drive gear loss.
If the motor is designed to reach optimum speeds e.g. 4000 rpm at 10 mph, what is going to happen to it at 60, 70, 80, 90, 100 mph? It would just put unnecessary wear and tear on motor and gearbox components.

I think I know an option that might be of interest. I'm getting a Bafang mid drive kit for my bicycle. Whilst I'm not planning on modifying my car, I know one of these has a freewheel built in and plenty of torque as it is driving the pedals so it should be able to turn wheels on a heavy car fine. All you'd need is a chain and sprocket then, although it would be preferrable to have the freewheel sprocket on the back wheel to stop any problems associated with a chain at high speed. It would be ideal to have the motor direct drive from the centre of the wheel though I am not sure how this would be done with existing brake gear in the way.

What I would be interested in is a custom sprocket that bolts on behind the wheel, contains an over run clutch and allows clearance for a chain without hitting the tire or side of the car. This seems like the most easy on, easy off setup without making permanent modifications to the car.

With 1000 watt motor at low speed I doubt torque vectoring would be a problem as the motor would likely only be used below 15 mph (about the same speed range as two people pushing my car from behind). It's been working fine on every power wheels vehicle so far. It's not designed to be a hybrid, more to use when going so slowly that the "basal metabolic rate" of the main engine is wasting fuel, and it would be more efficient to cut a hole in the floor and "Fred Flinstone" it. Though a motor on each wheel could add power.

For a go kart "differential" I would just use an engine driving a back axle and have each wheel be able to free wheel faster than the axle so that when it turns right only the right back wheel is powered and the left over runs and vice versa. Also if one wheel was off the ground or on slippery surface, the wheel on solid ground would do the work (unlike the situation you see in some cars - likely every FWD car I've ever driven - where the wheel on the snow slips and the wheel on the dry tarmac doesn't help it out.)

Last edited by CeeforCitroen; 08-14-2020 at 06:05 AM..
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Old 08-14-2020, 01:42 PM   #15 (permalink)
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Mike Dabrowski already did something like this.

He used a custom rig with an electric motor on a swinging arm driving a scooter tire that was pressed to the ground with a pneumatic cylinder.



A summary here:
The 5th wheel or Ewheel - MIMA Honda Insight Modified Integrated Motor Assist

More detail:
Final 5th wheel - MIMA Honda Insight Modified Integrated Motor Assist
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Old 08-14-2020, 02:40 PM   #16 (permalink)
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The design of the rear suspension and position of the shocks and springs does not lend it self to any type of drive system without nearly a complete rebuilding. I was not confident enough in the concept to risk permanent modifications that may not work as expected. I finally decided to remove the large final muffler in the exhaust system, and use that space for a drop down 5th wheel, powered by the high torque Etek motor, and driven by a scooter wheel.
This wins the thread. Now, just use a hub motor and have it pivot 90 and it becomes an aid to parallel parking.
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Old 08-14-2020, 05:13 PM   #17 (permalink)
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IIRC the spare wheel is located where the swinging arm could be assembled.


Quote:
Originally Posted by CeeforCitroen View Post
For a go kart "differential" I would just use an engine driving a back axle and have each wheel be able to free wheel faster than the axle so that when it turns right only the right back wheel is powered and the left over runs and vice versa. Also if one wheel was off the ground or on slippery surface, the wheel on solid ground would do the work (unlike the situation you see in some cars - likely every FWD car I've ever driven - where the wheel on the snow slips and the wheel on the dry tarmac doesn't help it out.)
How to control it would be the most challenging part, but the idea is interesting.
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Old 08-15-2020, 01:22 PM   #18 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
Why even care if the motor spins or not? Not looking at a lot of power consumption on a freewheeling armature if the field is disconnected, just bearing and drive gear loss.
Eddy current loss is greater than bearing losses in a permanent magnet motor and it's a big reason Tesla went with induction motors.

You also have mechanical strength limitations on the rotor.

A freewheel hub with a small motor geared very short is not a bad idea.
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Old 08-15-2020, 03:24 PM   #19 (permalink)
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Quote:
Originally Posted by samwichse View Post
Mike Dabrowski already did something like this.

He used a custom rig with an electric motor on a swinging arm driving a scooter tire that was pressed to the ground with a pneumatic cylinder.

A summary here:
The 5th wheel or Ewheel - MIMA Honda Insight Modified Integrated Motor Assist

More detail:
Final 5th wheel - MIMA Honda Insight Modified Integrated Motor Assist
I think I read about someone with the nickname "Mr Fifth Wheel" somewhere. Perhaps this was the guy. His motor looks to be a bit more powerful than what I had in mind - which would have been little better than a two man car push type speed. I wouldn't even use it to pull off a stop light. Once I'm up to 20 mph or come to a hill I can use the car engine again, but for those annoying times when you have to go slower than even idling in first gear will do, this won't putter away the fuel as much. Just wondering whether the existing wheels could be used but to be honest any "wheel on a stick" would do. I'm not too concerned about torque vectoring with a couple of horsepower at most though.

As for electric bikes, I have no idea how energy intensive manufacturing batteries are, though the battery on an e-bike is considerably smaller than that of a car. About 20 laptop batteries worth at the most, or 120 x 18650 cells for a large size battery. I think mine is going to be 52V 17.5Ah, so that's 14 cells in series by at least 7 in parallel.

Now here's another silly (or not?) question - does the energy cost of a continuous string of cars decelerating and accelerating round a cyclist outweigh the energy cost of one more car on the road?
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Old 08-15-2020, 03:32 PM   #20 (permalink)
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Quote:
Originally Posted by serialk11r View Post
A freewheel hub with a small motor geared very short is not a bad idea.
Yeah, at motorway speeds I imagine that thing would be SCREAMING! I'd be surprised if the gearbox didn't fall to bits, especially if there are any nylon gears in it. Something like this which I'm getting to convert my bicycle has a freewheel built in. https://www.amazon.co.uk/Bafang-BBS0...TF8&th=1&psc=1
It actually has 2 free wheels. One so the motor can spin the chain ring that would go on the end without spinning the pedals (so you can keep your legs still if you want). Another in the chainring and pedal connection itself so that when you pedal, you don't get the additional drag of spinning the drive train and motor.

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