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[Alan-CJ]

I have been reading with interest various posts regarding prop shaft to motor couplings.  I am building a Deans Marine 488 MTB and will probably use 2 x Deans Kestral brushed motors running on a 7.2v nimh battery.  In the past I have used Huco couplings but unless you get the allignment spot on they can be noisey, I was looking at using a double jointed coupling but these tend to be quite long, so I was thinking of giving silicone tubing a go.  I would use the splined inserts meant for the Hucos, so I believe I need 6mm inside diameter tubing, but what wall thickness?  I have seen it in 1mm, 2mm  and 3mm wall thickness, with a fairly fast boat I would think at least 2mm, is this correct?  Will this be suitable for this boat and if so, how is the tube attached, is it just a tight push fit or do you use some kind of mechanical fixing.  How long a piece of tube?  Similar to the length of a Huco?  Sorry for all the questions

[Shipmate60]

Yes on a fast boat I prefer 3 mm wall thickness.


Bob

[Alan-CJ]

Thanks Bob, I will have a look for some 3mm wall 6mm I/D and get half a meter

Yes on a fast boat I prefer 3 mm wall thickness.


Bob

[Martin (Admin)]

Hi Alan,
Push fit should do, a 'dob' of silicon or RTV gasket if they slip.   

[Rich griff]

Yes, silicon glow fuel tubing works well  on 540 size motor shafts and smaller motors like cassette players.


A bit of tube within a tube for  smaller diameter motor shafts.


This technique was used on walking pace models with great success even onotors with short stubby motor shafts but the longer the motor shaft the better.


Not used this technique on high load/torque systems yet, the tube coupling may want to "wind up"...


Following this thread with interest...

[roycv]

Spot on Alan J, we use 2mm thick walled tubing on Huco brass inserts and they work a treat.  The motors you suggest will work fine with 2mm wall tubing.
We have been using them for several years now I suggest you treat the lengths of tubing to hot water first and they will relax and if fitted when still hot and then run they will take up a straight shape.  Nice and quiet as well as vibration free.
Buy a metre!
Roy

[captain_reg]

I've had success with this on various models. Some were small models where the outer diameter of the tubing was probably not much more the 4mm. I used it as I couldn't get hold of a 'real' coupling as small as I wanted. Like others have said, very silent. I have tried it on a bigger boat which used the splined brass inserts. This tubing was quite thin wall, thinner than I think was ideal. I also had about an inch or so between the motor and shaft. In this case the tube tended to wind up if you applied too much torque. I fixed that by pushing a small length of plastic tubing about the same as the silicone tubes inner diameter. No effect on the noise of the coupling but increased the torque capacity massively.