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Author Topic: Universal Couplings  (Read 1005 times)

ajb63

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Universal Couplings
« on: April 11, 2018, 06:40:12 PM »

Hi
I am new to boat modelling and have a question on couplings.
At the moment I have the red plastic universal joints with brass inserts.They slide together easily but also slide apart easily to . Is this how they should operate or should there be an interference fit , or are they glued .
Thanks in advance for any replies.
Alan
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Liverbudgie

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Re: Universal Couplings
« Reply #1 on: April 11, 2018, 07:12:59 PM »

You leave them as they are, there is no need to secure the inserts to the plastic sleeve. Ensure though that the motor shaft and prop shaft line up as straight and level as possible.

LB
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Colin Bishop

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Re: Universal Couplings
« Reply #2 on: April 11, 2018, 07:15:59 PM »

In a proper setup the coupling should only be taking radial forces, it's not intended to absorb the thrust from the prop which should usually be taken on the outboard end of the propeller tube. (and not on the motor bearings!)

Colin
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ajb63

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Re: Universal Couplings
« Reply #3 on: April 11, 2018, 07:26:28 PM »

Thanks for the rapid replies.
Another question resolved.
Thanks
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SailorGreg

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Re: Universal Couplings
« Reply #4 on: April 11, 2018, 10:03:38 PM »

You might also want to consider what happens when you select reverse (assuming your boat does this).  In my early days I nearly ruined a nice propeller by not allowing for the fact that when the propeller pulls backwards it tries to pull the UJ apart. If there is space in the system, one or both brass inserts will be pulled partially or completely out of the red plastic bit, and the prop might hit the rudder. The way to avoid this is to install a collar and washer on the shaft next to the inboard end of the prop tube so that the collar takes the astern thrust not the UJ,  Hope that all makes sense.


Greg

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Re: Universal Couplings
« Reply #5 on: April 12, 2018, 09:00:03 AM »

You might also want to consider what happens when you select reverse (assuming your boat does this).  In my early days I nearly ruined a nice propeller by not allowing for the fact that when the propeller pulls backwards it tries to pull the UJ apart. If there is space in the system, one or both brass inserts will be pulled partially or completely out of the red plastic bit, and the prop might hit the rudder. The way to avoid this is to install a collar and washer on the shaft next to the inboard end of the prop tube so that the collar takes the astern thrust not the UJ,  Hope that all makes sense.


Greg






    I always thought that was why prop and shaft sets came with a collet and grub screw (that would make a good name for a gastro-pub )
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ajb63

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Re: Universal Couplings
« Reply #6 on: April 12, 2018, 09:21:58 AM »

Hi l am building the Model Slipway Tamar and prop. Shaft is threaded M4 both ends. After reading on forum  l understand the shaft end float situation. I just thought when l brought the u/j there would be more of an interference fit, but from all your replies that is not the case. Thanks again for another resolved issue.
Alan
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SailorGreg

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Re: Universal Couplings
« Reply #7 on: April 12, 2018, 09:42:34 AM »






    I always thought that was why prop and shaft sets came with a collet and grub screw (that would make a good name for a gastro-pub )


Perhaps I have been unlucky but I can't recall buying a prop shaft that actually came with a collet for the inboard end. They all should, but if you look at the ads for generic shafts and tubes, most do not show a collet. And what cuisine would The Collet and Grubscrew be serving?  ;)


Greg

ajb63

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Re: Universal Couplings
« Reply #8 on: April 12, 2018, 10:30:51 AM »

I think the person meant collar and grub screw on a plain diameter shaft.
Alan
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ChrisF

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Re: Universal Couplings
« Reply #9 on: April 12, 2018, 10:40:59 AM »

You have to be careful of some of the plastic couplings as they can come apart if a good load is applied to them.

Where I do use them I use the Raboesch (from Cornwall Model Boats etc.) which seem to be good quality and the inserts are a good tight fit. This is on a fairly low powered, low speed model.

For most of my models I'm going to use the more substantial all metal or metal/rubber couplings.

Chris
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Baldrick

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Re: Universal Couplings
« Reply #10 on: April 12, 2018, 12:33:39 PM »

I think the person meant collar and grub screw on a plain diameter shaft.
Alan


 whichever term you prefer, being of an engineering background I prefer collets.
https://www.rcworld.co.uk/acatalog/Wheel-Collets-Collars.html
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Netleyned

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Re: Universal Couplings
« Reply #11 on: April 12, 2018, 02:04:16 PM »

And what cuisine would The Collet and Grubscrew be serving? 


I
ron Rations :D
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Netleyned

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Re: Universal Couplings
« Reply #12 on: April 12, 2018, 02:05:56 PM »

Font Genie strikes again >>:-(
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derekwarner_decoy

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Re: Universal Couplings
« Reply #13 on: April 12, 2018, 03:17:21 PM »

So I think Ned says.....'And what cuisine would The Collet and Grubscrew be serving?'    

<*< Derek
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Derek Warner

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Netleyned

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Re: Universal Couplings
« Reply #14 on: April 12, 2018, 03:21:23 PM »

Hi Derek,
You missed the answer
Iron Rations :D
Ned
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derekwarner_decoy

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Re: Universal Couplings
« Reply #15 on: April 12, 2018, 04:14:45 PM »

Sorry Ned......it was there, but the intelligent IT system embedded within our WEB differentiated before and after the ICON.......I could not post it all :embarrassed:

Iron Rations :D

Interestingly, on the Continent  [France] ..many model steamers appear to be reverting to simple dog+pin type couplings....so typical of yesteryear but of course for low powered  O0 and relatively low speed applications

Derek

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grendel

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Re: Universal Couplings
« Reply #16 on: April 12, 2018, 04:50:36 PM »

I have used the front wheel cv unit and drive shaft off of a model car to go between the motor and the propellor shaft on one of my models, seems to be nice and smooth
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grendel

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Re: Universal Couplings
« Reply #17 on: April 12, 2018, 04:58:05 PM »

like this
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derekwarner_decoy

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Re: Universal Couplings
« Reply #18 on: April 18, 2018, 11:24:00 PM »

or this?
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Derek Warner

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RST

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Re: Universal Couplings
« Reply #19 on: April 19, 2018, 12:18:43 AM »

Sacriledge but I usually use the red Raboesh universal couplings also.  I've used them for 20 years plus but these days I find the double coupler is always slack.  I use a drop of epoxy or thick rubbery cyano on the brass coupler and all's well. I always try to fix the motor in alignment first-off so I use a single cell, just enough to turn the motor and find the "sweet spot" before fixing etc. Shoot me but it works well -nothing high speed though.
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