Motor Coupling to screw shaft

[Peter Brown 15Participant @peterbrown15]

I’ve removed the old motor from my Vosper and replaced with a new one. The old coupling on the motor attached to a T bar and had a slot to accommodate this. The diameter of the shaft on the new motor is 3.2mm. Can I get a new coupling that will fit the smaller shaft size.

[Peter Brown 15Participant @peterbrown15]

Motor to screw coupling

[Paul TParticipant @pault84577]

Peter

It would help if we knew the diameter of the old motor shaft and could see a photo showing the connection point on the propshaft.

Paul

[Peter Brown 15Participant @peterbrown15]

[Paul TParticipant @pault84577]

Hi Peter

Thanks for posting so quickly but the important bit is slightly obscured by the white wires and a little out of focus. With a clear, sharp image we can zoom in and look closely at the connection.

Paul

[Peter Brown 15Participant @peterbrown15]

Will take a few pics when I get home this evening and post. Hopefully will give a better idea

[Peter Brown 15Participant @peterbrown15]

Coupling Photos

[Colin BishopModerator @colinbishop34627]

Not sure if you can just get a suitable direct replacement for the motor end in that design. You might have to replace the whole coupling. 3.2mm is a common motor shaft size and the shaft should also be a standard metric or BA thread if threaded and a standard size if plain.

The issue you may have is to reproduce the length of your old coupling which might mean moving the motor slightly forwards or backwards.

All the individual bits can be purchased here:

**LINK**

Colin

[Paul TParticipant @pault84577]

Hi Peter

Colin has hit the nail on the head with his correct solution however if it was my problem I would wind a strip of foil around the new motor shaft until it made a tighter fit to the existing part and carefully tighten the grub screws.

Its a bit of a Heath Robinson fix but means that you keep the existing fittings.

Paul

[ashley needhamParticipant @ashleyneedham69188]

The link Colin has posted if followed back to the "couplings" heading has several other different styles of coupling, some of which are longer that others. Your old coupling may have tolerated a bit more misalignment than one of those plastic u/j types. Worth checking to ensure the motor is true at least in one plane.

Ashley

[Trevor Drabble 1Participant @trevordrabble1]

Peter , If it would help you , I would have no problem in machining a bush to suit . All I need is an accurate a measurement as you can of the diameter of your new motor shaft and then existing coupling posting to me . You can PM me your details if you decide on this option .

[Peter Brown 15Participant @peterbrown15]

I’ve ordered a coupling and inserts and will give this a try. I do have enough room to move the motor back or forwards which will help. Thanks for the offer Trevor, which I may take up if I don’t have success with the new parts.

[Colin BishopModerator @colinbishop34627]

I agree it is best to go with new parts, it gives you the best chance of avoiding driveline vibration. Paul's foil suggestion is an option but I have personally never found that increasing the diameter of the shaft works satisfactorily as when you tighten the grubscrew(s) it usually introduces a small amount of misalignment.

Colin

[Paul TParticipant @pault84577]

Colin

You might be surprised at just how many things are fixed out in the field with a gum foil wrapper, from a laser level to a 500t crane.

Paul

[Peter Brown 15Participant @peterbrown15]

Cheers Paul the silver foil was a good suggestion. Having a couple of pounds spare I thought I’d give the new parts a go.

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