Motor Coupling to screw shaft

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Motor Coupling to screw shaft

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8 August 2017 at 14:49 #72488
Peter Brown 15
Participant
@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.
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8 August 2017 at 14:49 #2697
Peter Brown 15
Participant
@peterbrown15
Motor to screw coupling
8 August 2017 at 14:58 #72489
Paul T
Participant
@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
8 August 2017 at 15:02 #72490
Peter Brown 15
Participant
@peterbrown15
8 August 2017 at 15:12 #72492
Paul T
Participant
@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
8 August 2017 at 15:22 #72493
Peter Brown 15
Participant
@peterbrown15
Will take a few pics when I get home this evening and post. Hopefully will give a better idea
8 August 2017 at 16:29 #72494
Peter Brown 15
Participant
@peterbrown15
Coupling Photos
8 August 2017 at 17:23 #72495
Colin Bishop
Moderator
@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
8 August 2017 at 18:21 #72498
Paul T
Participant
@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
8 August 2017 at 19:35 #72501
ashley needham
Participant
@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
8 August 2017 at 20:47 #72507
Trevor Drabble 1
Participant
@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 .
8 August 2017 at 21:45 #72509
Peter Brown 15
Participant
@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.
8 August 2017 at 22:05 #72511
Colin Bishop
Moderator
@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
9 August 2017 at 18:27 #72527
Paul T
Participant
@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
9 August 2017 at 19:17 #72529
Peter Brown 15
Participant
@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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