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Author Topic: Fixing prop and coupling to shaft  (Read 9064 times)

justboatonic

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Fixing prop and coupling to shaft
« on: September 04, 2011, 06:06:56 pm »

There's a similar thread about fixing small props on shafts but I dont want to appear as if Im hijacking that thread.

So, how do you use the lock nuts on a prop shaft to securely fasten the coupling and prop? Reason I ask is I used a spot of super glue between the lock nut and prop and found all I'd done was super glue the lock nut to the prop boss! Fortunately, I managed to separate the nut from the boss but I thought the lock nut was to prevent the prop coming off the shaft completely?

So, what's the best way to fix the prop and locking nut on the shaft? Is it necessary to loctite the lock nut at the coupling end?
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Shipmate60

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Re: Fixing prop and coupling to shaft
« Reply #1 on: September 04, 2011, 06:54:56 pm »

I dont use loctite at all.
I just lock the locknut to the prop out of the shaft and refit the shaft, never lost a prop yet!!

The coupling end is tightened in the model with 2 of the correct size spanners allowing only about 1/32" free play in the shaft.

Bob
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DickyD

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Re: Fixing prop and coupling to shaft
« Reply #2 on: September 04, 2011, 06:56:56 pm »

Make sure the locknut is tightened against the prop.

Works for me.

Belt and braces, use Loctite as well. :-))
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Timo2

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Re: Fixing prop and coupling to shaft
« Reply #3 on: September 04, 2011, 07:46:41 pm »

Hi

    Props,Nut,Washer, & Shaft ==   Happiness    O0

   Have a look at  http://en.wikipedia.org/wiki/Jam_nut

                        http://en.wikipedia.org/wiki/Locknut

                        http://en.wikipedia.org/wiki/Propeller

  timo2
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justboatonic

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Re: Fixing prop and coupling to shaft
« Reply #4 on: September 04, 2011, 08:00:59 pm »

Thanks all.

Due to the design of the MSW Envoy, you cant fit the nut and prop to the shaft then insert the shaft into the tube.
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Shipmate60

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Re: Fixing prop and coupling to shaft
« Reply #5 on: September 04, 2011, 08:10:23 pm »

In that case just lock the prop in place I use a bit of thick balsa on the hull and tighten the locknut to the prop.

Bob
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justboatonic

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Re: Fixing prop and coupling to shaft
« Reply #6 on: September 06, 2011, 03:18:35 pm »

Just had a thought (dangerous I know!), the prop shaft came with a nut at each end ie one at the coupling and one at the prop.

is this right or should both the nuts be at the prop end ie prop, nut behind that then second nut to 'lock' the first nut and prop?

Ta.
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Colin Bishop

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Re: Fixing prop and coupling to shaft
« Reply #7 on: September 06, 2011, 03:49:54 pm »

No, the idea is that the top nut should lock against the coupling and the bottom one against the prop. You might need a spacer at the top end to ensure that the 'slack' in the shaft is kept to a minimum. (a short length of tube slid over the shaft should do it.) You should also have a washer at each end between the tube and the nut to act as a thrust bearing.

Glynn Guest went into all this in a great deal of detail in the recent Model Boats Special issue but from the queries I have since seen on various forms few people seem to have read it.

Colin
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justboatonic

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Re: Fixing prop and coupling to shaft
« Reply #8 on: September 06, 2011, 06:13:22 pm »

No, the idea is that the top nut should lock against the coupling and the bottom one against the prop. You might need a spacer at the top end to ensure that the 'slack' in the shaft is kept to a minimum. (a short length of tube slid over the shaft should do it.) You should also have a washer at each end between the tube and the nut to act as a thrust bearing.

Glynn Guest went into all this in a great deal of detail in the recent Model Boats Special issue but from the queries I have since seen on various forms few people seem to have read it.

Colin

Thanks for the clarification, Colin. I dont subscribe to any mags atm.
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Colin Bishop

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Re: Fixing prop and coupling to shaft
« Reply #9 on: September 06, 2011, 07:06:56 pm »

Quote
Thanks for the clarification, Colin. I dont subscribe to any mags atm.

I appreciate that not everyone wants to subscribe to the mags but it does mean that the same very basic questions come up time and time again on the internet  Forums and can result in 'response fatigue' on the part of people who are able to answer them. One way arround this is to use the various Forum's search facilities which will very often give you the answer you want before posting yet another variation on a commom theme. That way everybody is happy.

Colin
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irishcarguy

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Re: Fixing prop and coupling to shaft
« Reply #10 on: September 29, 2011, 06:25:53 pm »

I turn the nut all the way on to the prop end of the driveshaft, it should just turn on with finger pressure, then turn the prop on the same way until it bottoms out ( reaches bottom of threaded hole in prop ). It should do this with just finger pressure, if not & it binds clean the thread with the proper size tap or die so that the prop screws on freely without binding on the thread. When the prop is on all the way you now turn the nut tight against the prop. Do NOT hold the prop with anything except your fingers, using pliers or other gripping tools to hold the prop will almost certainly damage the prop. If you install the prop in this manner you should have no trouble. Make sure you use the RIGHT SIZE spanner to tighten the nut, if you don't & you round off the corners of the nut you may a lot of difficulty getting it off later. needless to say you do not grip the drive shaft with any sharp edged tool that might damage the shaft surface, if you do this you will in all probability permanently damage the shaft causing it to leak water or worse bind in the outer tube. Any other questions just ask or PM me, I will be most happy to help you at anytime. Mick B.   
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Mick B.

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Re: Fixing prop and coupling to shaft
« Reply #11 on: September 29, 2011, 09:30:10 pm »

I start by matching the shaft to the tube , buy taking the shaft out off the tube putting on two washers and then the nuts then if needed I shorten the tube so it wont bind and so that no thread is in the bearings ,I then silver solder one nut on the prop end.
 depending on the size of the prop wind on prop mark then shorten thread  keeping a min of 10 mm dress the end  you can then never accidentally lock the prop too shaft or run thread in bearings down at the lake and swapping props can sometimes be a bit hecktick, , if you use a washer that is small in overall dia or one from a smaller size and open the hole out can get a small spanner on a bit  easier, I also use a stainless steel nuts where possible.
small cheap old pressed spanners can be bought on ebay then open up the jaws with a diamond file if wrong size. oh and I always fit an oiler

this is just how I do it, other's have there own way , it's what suits you .

Peter
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Shipmate60

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Re: Fixing prop and coupling to shaft
« Reply #12 on: September 29, 2011, 09:46:13 pm »

Mick,
You are more likely to damage a flat bladed prop by using fingers alone.
How do I know, been there, done that.
If it is a large prop on a 4 mm shaft either use loctite or hold the prop mechanically.
A large prop can exert quite high forces on the locking arrangement when going from ahead to astern or vice versa depending which handed prop you use.
In a model such as the Envoy it is too easy to only hold 1 blade as the rudder/skeg is in the way.

Bob
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