Wheel Spinning Motor?

[ML_Woy]

Well Guys, have been given a project by the manager of my bicycle store and I need some help. Thought someone might have some good ideas here.

The manager wants me to build him a display where he can showcase a new item we are selling, a device which hooks to your bicycle spokes, is battery powered and when riding your bike at night lights up your spokes and actually projects a message as the wheel turns. These are not new, I saw them in 2004 at the bicycle show in Germany one summer. Anyway we have an unused bicycle truing stand to hold the wheel with the device and I need some type of AC motor that I can mount to the stand, with a wheel attached, that I can bring in contact with the bicycle wheel to make it spin.

So I am looking for ideas on what type of motor to use, building a mounting bracket to connect it to the stand should not be a problem.

Any suggestions appreciated.

M.L. Woy

 

[twstoerzinger]

Hello M. L.

Here's a quick "back of the envelope" calculation.
You didn't say how fast you want the demo to run, but let's say 15 mph.

15 mi/hr / 60 = 0.25 mi/min * 5280 = 1320 ft/min surface speed of the wheel.

Lets say you surface drive the wheel OD by a small drum on a 1800 rpm motor shaft (a 4-pole motor will approach 1800 rpm with a light load).

1320 ft/min / 1800 rev/min = 0.73 ft/rev (circumference of the motor drum).
0.73 ft/rev * 12 = 8.76 in/rev (circumference of the motor drum in inches)
8.76 /3.14 = 2.8 inches diameter (drum on the motor)

I takes almost no power to drive the wheel. So, if you need to come up with a 1/12 or 1/6 HP, 1750 (or so) RPM, 120 VAC so you can plug it in. You then make an aluminum drum about 2 inches wide by about 2.8" diameter, with a bore to fit the motor shaft, with set screws, and maybe a key way. (This is the machining part).

Since the motor is the heavy part, I would mount the motor on the display base, and fab a simple fork to hold the wheel (maybe from an old front fork). Pivot the end of the fork opposite the wheel, so that the wheel axle rides directly above the motor shaft. The fork holds the wheel in alignment while the drum (on the motor) drives the wheel by surface contact. If this is a high-class bike shop, you could even hide the motor from view with painted sheet metal or cardboard.

For larger wheels or different speeds, just adjust the above calcs.

Safety Note: I suspect that some type of transparent guard is required to be sure that a customer cannot get his or her fingers, hair, clothing or whatever into the spinning spokes, or the nip between the wheel and motor.

Terry S.

 

[ML_Woy]

Hello M. L.

Here's a quick "back of the envelope" calculation.
You didn't say how fast you want the demo to run, but let's say 15 mph.

15 mi/hr / 60 = 0.25 mi/min * 5280 = 1320 ft/min surface speed of the wheel.

Lets say you surface drive the wheel OD by a small drum on a 1800 rpm motor shaft (a 4-pole motor will approach 1800 rpm with a light load).

1320 ft/min / 1800 rev/min = 0.73 ft/rev (circumference of the motor drum).
0.73 ft/rev * 12 = 8.76 in/rev (circumference of the motor drum in inches)
8.76 /3.14 = 2.8 inches diameter (drum on the motor)

I takes almost no power to drive the wheel. So, if you need to come up with a 1/12 or 1/6 HP, 1750 (or so) RPM, 120 VAC so you can plug it in. You then make an aluminum drum about 2 inches wide by about 2.8" diameter, with a bore to fit the motor shaft, with set screws, and maybe a key way. (This is the machining part).

Since the motor is the heavy part, I would mount the motor on the display base, and fab a simple fork to hold the wheel (maybe from an old front fork). Pivot the end of the fork opposite the wheel, so that the wheel axle rides directly above the motor shaft. The fork holds the wheel in alignment while the drum (on the motor) drives the wheel by surface contact. If this is a high-class bike shop, you could even hide the motor from view with painted sheet metal or cardboard.

For larger wheels or different speeds, just adjust the above calcs.

Safety Note: I suspect that some type of transparent guard is required to be sure that a customer cannot get his or her fingers, hair, clothing or whatever into the spinning spokes, or the nip between the wheel and motor.

Terry S.

Thanks Terry, so it is off to find a motor. The truing stand I have has a nice base to mount the motor to. Plan to run it only at night in the store window when the business is closed.