Scale Ship's Akula II Prop / Shaft problem

[corsaire]

Scale Ships' prop is bored to accept the provided 13/64" (5.16mm) stainless steel shaft.
However, I've decided to set it up using a 3/16" (4.76mm) SS shaft instead, just becasue is easier to find couplings, bushings etc, etc.

How can I accomplish this ? In other words, how can I reduce the 13/64"
prop bore to accept a 3/16" shaft?

Another problem is the provided prop is non threaded and doesn't come w/ a set screw either.

How do you guys work around this?

Pls advise,

Thanks,

Corsaire

[Guest]

Hello

I did that to

Hello

I did that to my Akula II by inserting a brass tube that fits the 3/16th shaft and fits the prop bore,then a flat is ground onto the shaft to alighne with a set screw tapped into th prop.

K and S tubbing is the brass tube,just select the right size.

You will find that the scale prop does not produce enough thrust at any speed so just bend each blade until you are happy with the thrust ouput,the blade will not break.

Enjoy the build

Dave

[crazy ivan]

Wow, that is only 0.0078125

Wow, that is only 0.0078125 inch clearance all the way around. Not enough to sleeve it with some standard size brass tubing, unless you bored the prop out a bit more. I could suggest a couple of other approaches, neither of which are pretty unless you have a lathe.

You could tap threads into the prop. The way I usually deal with a threaded prop is to bore out a brass screw of the appropriate thread size and solder it to the shaft, then secure the prop on with a lock nut. This may require turning down the end of the shaft some so that the bore hole in the screw isn't too big. 13/64 is just around .004 in. larger than a #8 drill bit, which is the size for a 1/4-20 tap. The 3/16 shaft is too large for any reasonable hole you can bore in a 1/4-20 screw. So you would need to turn down the end of the shaft.

Going the other way, the 13/64 hole is just about .010 in. smaller than a #3 drill bit, so you might get away with tapping a 1/4-28 thread in the prop. A 1/4-28 screw might just take a 3/16 bore hole and still have enough "meat" left to be useful.

The other way would be to fill in the prop hole with a hard machinable epoxy, like JB Weld, and re-bore the prop to 3/16. Then you would need to drill and tap the hub for a very small set screw.

[corsaire]

>>>>The other way would be

>>>>The other way would be to fill in the prop hole with a hard machinable epoxy, like JB Weld, and re-bore the prop to 3/16. Then you would need to drill and tap the hub for a very small set screw.<<<<

This option seems the most feasible to me, albeit I'd had to hire a machinist as I don't have a lathe.

Thanks all for the feedback,

Corsaire

[Guest]

If you have a machinist

If you have a machinist friend, you could always ask him to ream out the bushings and coupligs to accept the off size shaft.

Andy

[corsaire]

I can't used the the

I can't used the the provided shaft by Vladimir, out of the question. For one, too wide (no space for the already tiny jolk/jumper) and that would imply to use his bushing which in turn would mean to grind the 3/8" dia. tapered stern end to an egg shell like skin, over weakening this way the stern tip.

[Guest]

Will 0.5mm make that much

Will 0.5mm make that much of a difference?

[Rogue Sub]

I just chucked the 3/16

I just chucked the 3/16 shaft into my drill press and positioned my prop under the shaft so it was level using clay then brazzed it on. The silver solder filed the holes and if needed you can take it apart later with some heat.