Prop Movement??

[M.M.]

Well i just got my boat today and i noticed that between the stinger and the drivedog there is a small gap which allows the prop to move in and out about a 1/16 of an inch. There is also a gap between the drivedog and prop, which i can't seem to get rid of even when he prop nut is completely tight. It seems as if i have run out of threads for the prop nut. so do i need to fix this and how? Or is some movement good?

[ED66677]

nope! if it's a flex drive line you have to keep this gap because the flex shorten under load!

[egneg]

If the prop is to short for the threads just add a piece of cooling line and a lock nut to keep it in place.

[Fluid]

...i noticed that between the stinger and the drivedog there is a small gap which allows the prop to move in and out about a 1/16 of an inch.

If the boat has a flex cable, this is not enough gap. Increase the gap to the diameter of the cable - this is a good rule of thumb. The short 1/16" gap will allow the drive dog to rub on the stinger, causing lots of drag and heating up your cells, motor and ESC.


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[M.M.]

Ok, so the gap between the drivedog and the sting should be approx. the same as the width of the cable? Yes it is a flex drive, so how do i know how thick the cale is? (I though i remember seeing that it was .150, but im not sure)

[Fluid]

Since we have no idea what the boat or setup is we can't answer your question. But look at the cable and set the gap close to the diameter of the cable - it does not need to be exact. A little more is better than too little.


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[M.M.]

here is the boat: http://cgi.ebay.com/ws/eBayISAPI.dll...m=300268910685

It has a flex shaft that is ground down on the end to form a square which connects into the peice that the prop screw on to.

[egneg]

The gap should be 2.5 times what it is now or 0.157 inches.

[M.M.]

Well after some more inspection today i found that my set-up must be way different from yours.

On mine i have the flex shaft the connects to the motor via a coupler, then at the other end it has been ground down to form a square"key". This "key" slides into the propshaft(i think thats it) which goes into the stinger. So then i realized that the actual propshaft peice does not move, it just stays in the stinger housing. The part that will allow for the shrinkage of the flex cable is where the square "key" on the end of the cable slides into the propshaft. This allows that cable to shrink approx. 3/8 to 1/2 inch, however, there is not enough room for the cable to expand. So should i adjust it to allow for expansion, or will the cable only shrink and not expand under load?

[785boats]

M.M.
Your last assumption is right. The stub shaft is a floating shaft. When the flex winds up it slides in the socket.
1/16" is more than enough gap.
Make sure that nylon thrust washer is always there because the rear of the strut takes the thrust with this set up not the motor as with the more standard setup.
A word of caution... I have split the socket on three of those stub shafts & the square end of the flex just spins in the socket. Probably because of the upgraded power plants.
All the best.
Paul.

[B-DAWG]

785 I have the same boat and setup. I just ordered a Medusa 28-56-2800Kv motor. I'm running 3S 11.1V 30C battery, castle hydra 120 ESC, X435 prop. Do you think I'm going to run into any driveline problems? I'm going to try and go to a X440 or X438 prop.

[785boats]

It's hard to say.
Here's my experience.
Split one with an aquacraft SV27 package in it with an X645 prop on 4s lipo.
Split another one with an Ammo 2300 kv motor & a Grim Racer 40mm x 52mm /3blade prop on 4s lipo.
Split another in my 32" cat (with the same driveline) on an 8XL with an X640 on 4s Lipo.
My solutions.
I soldered the one into the shaft on the cat. Still going strong.
I've just replaced the stinger on this mono hull with a 3/16" one & will be testing on Saturday.
All the best.
Paul.

[M.M.]

So what is there that i can replace the driveshaft with?

[785boats]

Give it a chance first. It might be fine. Use it for a while first. If it splits, then worry about replacing.
Steve sells some good units here on O.S.
Cheers.
Paul.

[M.M.]

Cool thanks,
well i should be able to get the rest of my parts soon and get it running hopefully.