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Author Topic: shaft and motor alignment  (Read 7371 times)

Stuart

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Propshaft alignment
« Reply #25 on: August 09, 2008, 09:24:55 PM »

I am currently building my first model, a Hunstman 31 on a GRP hull and have a query regarding the propshaft alignment. I have fitted the electric motor and also positioned and used epoxy resin to fit the propshaft which is joined to the motor using a coupling. I am quite satisfied with the alignement of the propshaft from  the stern up to the motor, however I do have one issue. The coupling after attaching to the motor drops slighty for the propshaft to be able to screw in to it. It therefore is not in a totally straight line. It is difficult to measure how much it drops and I have taken digital photo's if this helps should they be needed.

My questions are, should this be something to worry about?
Should I wait until it is powered up until  I see whether this causes vibration or has a negative effect on the life of the batteries.
Should I correct this, which would mean freeing the propshaft from the epoxy resin, if this is possible without causing too much damage. I am just finishing fitting out the inside of the hull and I am yet to complete the superstructure before considering any paint job.

Any thoughts would be appreciated. Thanks. Stuart
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barryfoote

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Re: Propshaft alignment
« Reply #26 on: August 09, 2008, 10:12:01 PM »

It sounds to me as though the couplings diameter is larger than the props shaft. The coupling should have come with an internal collar so that the shaft is a tight fit. If you think this may be the cause, get back to the shop where you bought the coupling from and see if the have a collar for it.

Barry
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DickyD

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Re: Propshaft alignment
« Reply #27 on: August 09, 2008, 10:14:59 PM »

Stuart, if you have to move anything it might be easier to move the motor.

Try attaching the coupling to the prop shaft first.

If its a little bit out it shouldn't matter to much, thats why you have the coupling.

Give the motor a run and see if you have any adverse affects.

Good luck. O0
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Garabaldy

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Re: shaft and motor alignment
« Reply #28 on: August 11, 2008, 01:35:02 PM »

i fitted my motors to my tug and powered them up in the  bath on friday night.  Starboard sounded smooth as silk but ironicly you could see clear as day the alignment was MILES out where as the port side alignment looked good but it sounded more like a 12 cylinder diesel engine turning over when i powered it up.  So i took everything out on saturday morning then chisled the motor mounts out and totally redesigned the mounts and fitting them using a modified MMM alignment tool and the "dollop" of p38 filler method.

Now all alignment looks good from all angles O0  When powered up this time, the starboard side was as smooth as silk.  The port side, which now in theory should have near perfect alignment sounds much the same as before.  I can see the end of the coupling which is attached to the shaft bouncing up and down.  I notice the nut on the said shaft is very "wonky", it looks like the threads have been very poorly cut.  If this is the case, would this be the cause of my vibration.  IE the coupling cannot mate to the shaft concentricly because the threads are "wonky".

Has anyone else experienced a similar problem?
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Shipmate60

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Re: shaft and motor alignment
« Reply #29 on: August 11, 2008, 01:45:13 PM »

I have had problems with the coupling ends being bored off centre which will give vibration and noise.

Bob
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Martin [Admin]

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Re: shaft and motor alignment
« Reply #30 on: August 11, 2008, 01:55:55 PM »

Or you could have a bent prop shaft!
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Garabaldy

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Re: shaft and motor alignment
« Reply #31 on: August 11, 2008, 02:56:43 PM »

I dont think the shaft is bent as it slids in and out of the tube perectly O0
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Martin [Admin]

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Re: shaft and motor alignment
« Reply #32 on: August 11, 2008, 04:24:17 PM »

Take out the shaft and roll it on a very flat surface, glass, worktop etc......
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Garabaldy

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Re: shaft and motor alignment
« Reply #33 on: August 11, 2008, 06:38:07 PM »

the shaft is spot on, the problem is the nut.  The the tap which cut the thread in the nut did not go through the nut concentricly.  I swapped the nut for a good one and there was no vibration atall.  Problem sorted  ;D

Now i need a new nut, such an inconvenience >:(
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Martin [Admin]

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Re: shaft and motor alignment
« Reply #34 on: August 11, 2008, 06:48:38 PM »


There's always some nut behind annoying problems!  {-)
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bbdave

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Re: shaft and motor alignment
« Reply #35 on: August 12, 2008, 06:03:56 PM »

Just fitted motor coupling etc into my swordsman here's how i did it i bought a shaft and coupling from Mobile Marine which they make themselves the coupling ends are brass one tapped 4mm the othe a grub screwed 3mm hole but both ends accept an 8guage wire on the inside ends so i used a piece of piano wire to line things up smeared th motor mount with vaseline and bedded it onto P38 which i will drill and tap later here's the pics as this explains easier  {-)

The coupling the tube can be cut to suit



8 guage piano wire




Motor all lined up the back end needs to be supported to avoid the motor hanging on the shaft



P38 set



Dave
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