Agreed. 72W seems inadequate.

 

You could use that motor to drive the chain that drives the free-wheel, that would solve the non-back-drive problem, but what I do not see is a motor output shaft. I am guessing, based on the appearance, that it is a power seat adjusting motor. If that is the case then it does not have an output shaft, it has a square hole to drive a flexible shaft. So let us know what the original application was.

Yes, you're right, a square hole to drive a shaft.

 

The solution is to drive a sprocket that engages the pedal chain thru an over-running clutch, and use one of the flexible drive cables as the connection. That will allow a very minimum drag and also eliminate the problem of the motor stopping the wheel.
But there is one additional concern, which is that motors for any of the adjustment accessories in a car are intended for intermittent duty applications and they will get way to hot in anything like constant duty service, especially at anything near full load. Of course, the guess about the original application is still just my guess.

 

The solution is to drive a sprocket that engages the pedal chain thru an over-running clutch, and use one of the flexible drive cables as the connection. That will allow a very minimum drag and also eliminate the problem of the motor stopping the wheel.
But there is one additional concern, which is that motors for any of the adjustment accessories in a car are intended for intermittent duty applications and they will get way to hot in anything like constant duty service, especially at anything near full load. Of course, the guess about the original application is still just my guess.

I did manage to get some specs: It is 12 V, 2.8A , 590 RPM No load and it is a car seat motor

 

Cae seat motors are able to provide quite a bit of torque, but consider how long the average car seat adjuster motor is run, even when one is trying to get exactly the right position. Those are short duty-cycle motors and if you run one for five minutes it will probably get "quite warm." Also, at 12 volts and 2.8 amps it is about a 32 watt motor, which may not provide enough torque to be worth the effort.

 

Cae seat motors are able to provide quite a bit of torque, but consider how long the average car seat adjuster motor is run, even when one is trying to get exactly the right position. Those are short duty-cycle motors and if you run one for five minutes it will probably get "quite warm." Also, at 12 volts and 2.8 amps it is about a 32 watt motor, which may not provide enough torque to be worth the effort.

No, 2.8 A is the No load current not F.L. which I guess is @10A

 

Coming back to bikes. I may have asked this question before but lost the thinking behind it. I want to add a small motor or engine to my bike. Since model aero engines (say 5 cc)/motors are very light, thinking of using these. Only, they come in high speeds. Wonder if this is a major issue as surely it can be geared down but someone challenged that idea and I have lost the reasoning behind it. Any help appreciated.

 

Coming back to bikes. I may have asked this question before but lost the thinking behind it. I want to add a small motor or engine to my bike. Since model aero engines (say 5 cc)/motors are very light, thinking of using these. Only, they come in high speeds. Wonder if this is a major issue as surely it can be geared down but someone challenged that idea and I have lost the reasoning behind it. Any help appreciated.

It does not have sufficient power. You would need about 50cc (max before requiring a licence).
You need bare minimum ¼ hp or 200W. Better to start at about 350W.

 

Here is another suggestion that is much simpler, I did it and it works: change to a three-speed front sprocket with a smaller low gear, and the get a rear free-wheel setup with a larger first gear. you can get to having at least two crank revolutions per wheel revolutions and I have found that to work on any hill where the rear wheel does not slip. You may need to also change the shift levers, but that is not a big deal.
And the weight penalty is far less than for adding even a minimum electric motor system.
And it never runs the battery dead, or to be recharged.

 

Friction drive isn't really so bad. Back In the 50's I rode to school on a push-bike with a bolt-on friction-drive petrol-engine. My first engine was a Velosolex (an earler version of this). I later had a rear-wheel drive engine (I never did know the brand). With both engines you started them by initially pedalling the bike, then engaging the 'clutch', which simply yanked the drive roller down onto the tyre. Surprisingly, in two or three years of cycling this never shredded the tyre or caused a puncture.

Remember what engine?

 

Friction drive on a front wheel means a few pounds of mass adding to the inertia up front and that will certainly make the quick maneuvering sometimes needed rather dodgy at best. NO THANKS, I have no interest in that, not one bit. I do not ride that gently.

 

Remember what engine?

As I said, the first was a Velosolex, the second was an unknown (unmarked) brand. Both were 49cc if I recall correctly.

I do not ride that gently.

I had no choice, as both engines were pretty feeble. Max speed was around 25mph. Back in the 50's there was little traffic on the roads, and as it happened I never needed quick manoeuvering (luckily).

 

That motor has a worm gear in it. That would not be a good idea on a bicycle because if you were to cut power to the motor it would be like applying the brake and it will throw you over the handle bar.

Thanks for reminding me; dont want to get thrown over! Wonder how to solve this - using a clutch or freewheel or any other solution?

 

Thanks for reminding me; dont want to get thrown over! Wonder how to solve this - using a clutch or freewheel or any other solution?

Driving through a freewheel would work, it serves as an overrunning one-way clutch.