Aquacraft MiniMono Drive Shaft keeps coming loose

[Puddle Jumper]

Lost prop shaft blues

I've lost several propshafts (along with the prop and propnuts thank you).
I noticed those are all sold seperately.
The wire either spins loose from between the setscrews and falls out, or the wire pinches off from overtightening the set screws.

I came up with a simple modification.
drill an angled hole in the side of the coupler, and bend the shaft wire to run out the side of the coupler.
This effectively "keys" the shaft. The set screws only have to be tight enough to keep it from pulling out in reverse.

the coupler has to be removed, and to do THAT, the drive shaft tube has to be shortened.
Best done with a dremel, being sure to protect the hull with something in case you slip.
I used wood shim tips.
then cut back the tube.

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remove the coupler
use an automatic centerpunch to mark a spot roughly centered between the setscrews.

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start a 1/16" hole straight down into the coupler, just enought to get a bite and then drill the hole through to the center at about a 45 degree angle. Drill TOWARD the propshaft end of the coupler (smaller hole).

IMG_0608.jpg

Then drill out the propshaft end of the coupler, increasing the hole size to about 7/32".
This gives you room to work the wire into the key hole.
Then it's just re-assembly (don't forget the boot on the end of the propshaft sleeve), and use plenty of shaft grease.
Final step is bending the propshaft wire.
A radiused curve as shown will help work the wire into place.
With practice, a tighter angle bend will help reduce vibration.
Image is shown out of the boat for clarity and compared to a straight shaft.

IMG_0612.jpg

Finished install should look like;

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I hope this saves us ALL a bunch of money!!

[JackJ]

Hey, that looks like a great solution! Received my Minimono a couple weeks ago, but haven't run it yet since I've felt like I needed some extra drive shafts and nobody has them in stock.

Thanks!

Jack

[Puddle Jumper]

Good luck with that!
I think the rest of us have been buying up the inventory as fast as they could stock it!
I hope this helps.
Have fun, its a blast!!
Advise you start off with the turning rates turned down and about half throttle till you get the feel of it.
It turns a lot tighter to one side (right I think), and it can flip itself.
It will float, but you dont want the electronics to get wet.
I made some course bouys that work great.
I'll have to post those.

DC

[3b3b]

Good idea. Any added virbration noted in the boat? I would think the bent end going thru the coupler would throw the whole thing off balance an possibly add more stress to the motor.

Hey... no need to cut the tube. Just undo the 3 bolts that hold the motor and cooling plate. But it is a slight PITA to rescrew the bolts.

[Puddle Jumper]

I did try that.
And you're right! it looks simple.
I couldn't get a good enough bite on the screws to loosen.

I expect the amount of weight imballance to be insignificant.
If anything, the shaft wire in the key hole of the coupler should help to re-ballance.
I'm actually more worried about the shaft being off centered coming out of the coupler, and reaming out the hole in the end of the shaft sleeve boot.
I plan to find out about the vibration tomorrow!

If it explodes in flames I'll let you know!!

[3b3b]

Wishing you no flames or high temps. :)

I've been thru 2 shafts and on my 3rd since July. New grub screws and loctite helps but still not problem free. And with all 3 shafts, I notice that they are all misalighnted... really sucks.

I've asked Jeff http://rcraceboat.com/ if he could make a coupler and wire shaft for the mm but has not replied back.. Anyone know what's the size of the wire? 047?