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Author Topic: Drive shaft advice  (Read 1652 times)

mbm999

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Drive shaft advice
« on: April 15, 2020, 09:35:26 pm »

Hi,
Could i draw on your experience and ask about the set up for the drive for my boat (Aeronaut Diva), please.

I decided to dispense with the supplied propshaft (not least because its so stiff it won't rotate in the tube) and am undecided as to the correct arrangement for the new setup (i'm also not sure that a 3 blade prop is the right choice so would like to keep my options open).
On both the shafts i'm considering, the propeller (when fully screwed on) leaves a portion of the shaft thread exposed when the nut is tightened against the propeller ie. the thrust washer does not sit against the tube bearing. I'm also assuming that the plain shaft should run in the bearing and not the threaded part.
So, the questions ....
1. Should I pack with washers/nut or shorten (cut) the excess thread or buy a different propeller and hope it is slightly longer (or something else).
2. Is there an optimum distance between the end of the propeller and the rudder as i can't decide whether to use the 6.5" or 6" shaft.
3. I think i may have made the prop tube hole a little too big, would you just epoxy it in or use P38? (or something else).
4. Is there any advantage to having a slimline prop tube (the 6.5" i have is slimline (but has a slight dent in it) whereas the 6" is not slimline).
5. I've noticed that many people use a U/J instead of a rigid connector - is this purely to guard against a misaligned drive?
 
Any suggestions/comments are more than welcome.
Many thanks,
Mark
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ChrisF

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Re: Drive shaft advice
« Reply #1 on: April 16, 2020, 09:33:29 am »

Hi Mark - I've got the same issue with my prop shafts in that the thread is too long and would run inside the bearing. I'm going to cut it down with a Junior hacksaw and file the end. Make sure there is a nut on it when doing it so that you can screw it off afterwards to ensure the thread is Ok.

The prop needs to be pretty close to the rudder for the rudder to be effective. Around 8mm to 10mm is about right.

Put some tape on the hull around the prop shaft and run the epoxy in around the prop shaft having abraded the tube for the epoxy to get a grip. Then use P38 or Milliput putty to fair in where the tube exits the hull.

You could use a rigid coupling if the alignment is dead on but that is difficult hence why UJ and other flexible couplings are used. Alignment still has to be accurate though unless you use double or dog-bone couplings. I use a solid coupling to set up the motor/shaft alignment and then replace it with a flexible coupling.

Chris
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GG

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Re: Drive shaft advice
« Reply #2 on: April 16, 2020, 10:58:11 am »

Mark,
        Might be worth reading the thread "Free Turning" in the Techniques.... Tutorial section?


Glynn Guest
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Shipmate60

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Re: Drive shaft advice
« Reply #3 on: April 16, 2020, 06:59:48 pm »

With all that free play the boat will be driven through the motor bearings/bushes, nor a great idea.
If necessary as has been suggested shorten the shaft so only abour 1.32" is set.


Bob
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john44

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Re: Drive shaft advice
« Reply #4 on: April 16, 2020, 07:34:17 pm »

Hi Mark, you are correct in thinking the smooth shaft runs through the shaft bushes, if you have exposed
thread showing it may draw water into the tube, like an auger on a drill does the thread will do the same.


John
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mbm999

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Re: Drive shaft advice
« Reply #5 on: April 17, 2020, 12:50:21 pm »

Appreciate you all taking the time to reply.

Many thanks,
Mark
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