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[darrencuk]

Hi I was just wondering if u guys can help with my universal coupling question :s I'm going to be running a 3.17mm motor shaft so I have brought a 3.2mm coupling for the prop end I am looking at a shaft on cornwall model boats its 68 mm long 4mm thick with the inner part at 2mm which the prop screws on to so I understand I need a 2 mm coupling my question is will this be safe using a 3.2 up front and bringing it down to a 2mm reason I'm asking is 68mm is spot on leangh I need just worried about lowering size at back hopefully one u guys out there can help u have been very helpfull so far thanks again :)

[DickyD]

Sorry, cant really understand what you are asking.

All you need to know for a universal coupling is the diameter of the prop shaft and the diameter of the motor shaft.

[wartsilaone]

I tend to agree with Dicky. I can't see any problem as long as you have the couplings to match the motor and prop shaft.

[pugwash]

I think what is worrying him is the torque involved reducing from 3.2mm to 2mm - I dont think there should be any problems
providing you haven't got an ENORMOUS motor on the end of the shaft.

Geoff

[john44]

You havent said what size /type of propeller you are thinking of using.Also on what type of boat,
 If for example it is going on a tug-boat with a large prop I would be a bit worried.

john

[Netleyned]

Sounds like a 385 so it should not be much of a prop on that on a 2mm shaft

Ned

[darrencuk]

Its a custom built boat I'm trying to cut down on room as its a small boat I'm running a 540 motor I was thinking off running 30mm prop 2 blade or 3 don't no yet was just worried about tourque

[Shipmate60]

2mm is rather small for a 540 motor.

Bob

[Netleyned]

Senior moment from me sorry
Transposed my twos and threes
385 2.3mm 540 3.2mm

I agree with Shipmate 60
2mm shaft is too small for a 540


Ned

[darrencuk]

ok thanks What prop shaft would u run in your opinion then still learning

[Shipmate60]

A standard 4mm propshaft will be fine.
If the length is crutial contact MMB as Mark will make shafts to an exact size   CLICK HERE

Bob

[darrencuk]

So just so I understand 4mm prop shaft will be 4mm center part so I will need a 4mm coupling but the outer shaft of the prop shaft the part that fits in the hull is 6mm and I will need a m4 size thread prop?

[DickyD]

Right 

[darrencuk]

Do u think the person u have said about making me a shaft could make a 4mm one in the length 100mm

[Marks Model Bits]

Hi, yes we have them in stock give me a ring and I can help you more

Mark

[darrencuk]

Just like to say a big thank u to everyone who helped me I now have a shaft on order from mark very happy thanks guys this site is very helpfull