Motor pulley

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26 December 2013 at 22:22 #45807
Paul75
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@paul75
Hello Everyone.

To achieve a correct scale top speed for my HMS Duke of York I intend to change the belt drive reduction gearing ratio to increase the propellor revolutions. Hopefully I'll be able to simply remove and change the pulley wheels attached to the motors themselves but I don't know how to actually detach them.

I've attached an image below which shows the current pulley including the locking screw.

I thought the screw might be compatible with an allen key but it seems to be circular and the allen key will not engage.

Firstly can these pulleys be removed easily and how is this acheived? Is a special tool required?

Also, since I know the specific diameter of the new pulleys I will require, can anyone recommend a supplier which stocks a wide range of pulley sizes for these applications? If I can't buy these "off the peg" can anyone advise who might be able to manufacture a bespoke pulley for my requirements?

Many thanks in advance,

Paul.
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26 December 2013 at 22:22 #5285
Paul75
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@paul75
26 December 2013 at 23:15 #45810
shipwright
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@shipwright
Hello Paul,

Is this a scratch built model ship, or built from a kit or Ready to Run model ?

If this is a locking screw then possibly the hexagon socket is simply worn to circular – if that is the case then the only way that I can think of removing the pulley is to drill out the locking screw (not an easy task)

Alternatively it might be a press fit locking device that is not intended for removal.

If you fit another pulley on to the motor shaft to lower the reduction ratio you will need another belt (unless you can adjust the position of the motor.

If you reduce the drive ratio you might find that the motor is overloaded – do you know what type (manufacturer and specific electrical parameters such as no load rpm, no load current, stall current) of motor it is ?

Ian
27 December 2013 at 12:39 #45838
Paul75
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@paul75
Thanks for your reply Ian.

All four motors have the same pulley connection so I'm guessing the pulleys are not intended to be detached. I bought the model almost completed with the motors and running gear already installed. I understand from the seller that they are 540 type motors but have yet to measure the no load or stall current. I've had the model running on the water a few times and she runs well but needs an extra 50% more speed for an accurate scale top speed. After about 45 minutes of use at full power the motors are currently barely warm so I would hope they could cope with more load. If the motor pulleys can't be detached I'll look into replacing the prop shaft pulleys or perhaps replacing the entire motor to shaft drivetrain.

Thanks again,

Paul.
27 December 2013 at 13:40 #45839
shipwright
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@shipwright
Hello Paul,

The following threads on this website provide a useful insight into motor performance :

**LINK**

**LINK**

It shows how there is a maximum output from any motor which cannot be exceeded. Mark Beard's spreadsheet is useful for motor selection. It doesn't provide the crucial data on torque-speed for propeller and I have always resorted to experimental data for that.

Ian
28 December 2013 at 15:33 #45854
Telstar
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@telstar
Hi Paul

Like Ian (shipwright) I have used Mark's spreadsheet with success. However there are one or two things to resolve before this is required:

The pulley looks (to me) to be a custom made aluminum one, I think the fixing is , or was, an allen screw that has been 'rounded' by over tightening andor a poorly fitting allen key. This said, the pulley can be removed although destroyed in the process using a Nutsplitter **LINK**.

To experiment to try to determine the size of a suitable replacement pulley I would try, wrapping two or three turns of plastic tape tightly round the existing pulley (blocking the groove) replace the belt, and try a run. You may be able to temporarily increase the size further depending on how much stretch in the belt. If this gives improvement measure the overall diameter if no improvement remove the tape (back to basics)

Cheers Tom

Silly afterthought would it be possible to change the prop
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