No problem jumpugly, it’s always good to be able to help somebody else.

…I need help myself sometimes (well quite often really) and always appreciate it when I get offered advice.

Bob.

Roy, so far I have been using M4 inserts. I make the hole in the props hub a medium press fit with some superglue so it aligns with the insert pretty good.

I don't build (or even have) speed/racing boats. I don't classify patrol boats as "speed boats". Thus I have no interest or issues with specialty shafts. Just keeping it simple with my scale boats.

Lew

Thanks for posting your reply Bob! It's a huge help as I want to try and limit my mistakes. Right now I am still integrating the servo arm and rudder now that the Traxxas drivetrain and driveline are set.
Be prepared for more questions!
👍😁

Hi jumpugly,

Most of my fast electric boats have flexible drive shafts and they are always completely removed from the boat after every session, cleaned and re-coated with a special flexi-shaft grease.

The flexi-shaft is then re-inserted into the drive shaft tube and the end play is adjusted.

The end play is important to get right as some flexible shafts “wind themselves up” and so become shorter so it is important to allow for this.

Manufacturers of boats that come with flexi -drive shafts usually suggest the size of the gap to be left between the end of the drive shaft and the dog drive collet, but after each run I always check the gap to see if it is running “tight” and if it is I will readjust it to increase the gap to be safe.

These flexi-drives need to be replaced from time to time, but if bought from a third party supplier the direction of the twist needs to be checked as they can be made for use with clockwise and anti-clockwise direction drive systems.

It is fairly easy to check this direction of turn to make sure that when the flexi-drive is inserted it will tighten when turned and not unwind.


Bob.

Hi Gang! I am sorry for the recent radio, but was happy to see Lew bring up an interesting subject this morning.
The Traxxas drive line I am using in my K7 has a stuffing tube filled with plastic Teflon liner to hold the flex shaft snuggly. However, the shaft has to be greased like crazy with their marine grease to support the power being produced by the brushless dual lipo setup. Something I am basically learning on the fly as I have never floated anything with this much power.
Two of the biggest concerns are, props blowing up and flex shafts unwinding and obliterating themselves and the stuffing box components if you gun the motor in reverse.
So, I am proceeding with extreme caution these days especially on the issues of Lipo charging, discharging, and safe storage levels, in addition to all my driveline concerns.
Fun, fun, fun!
👍😂

Hi Lew if you 3D print a propellor what about the thread or do you clamp them in place?
Roy

Many years ago a friend who was instructing on using a lathe said a stuffing box is a good item to make.

With the screw adjustment that brought pressure onto a few winds of string and vaseline, it clamps tightly onto the rotating shaft but only for 0.5mm leaving the shaft hardly feeling the drag. Works well but not an item that would sell commercially.

The commercial shafts and their bearings in the tube are not interchangeable. There is too much variation in the actual diameter of a 4mm shaft, or 5mm come to that.

I recently upgraded an open frame red magnet electric motor as the shaft was sitting in a 20 gauge aluminium frame. I just used the interlocking brass tubing you can buy, which with a 5mm length and lightly oiled can make a good bearing surface.
I accept phosphor bronze is much better but I can so easily replace the existing bushes it does not much matter.

In commercial prop shafts it is easy to knock out the end bearings, Just pull the shaft out a bit to the other side of the bearing and hit the shaft end lightly with a hammer and they fall out.
This way you can shorten the prop tube and then replace the bearing.

The biggest problem is when you come to threading the shaft, I have to visit my friend with a workshop and he does it using his lathe.
There is an additional problem as the thread cutter has a grub screw to adjust the cut and you want as tight a fit onto the prop or U/J as you can get.

Lew sorry to go off piste a bit with bearings!
Roy

I noticed that props and shafts seems to be popping up in different subjects again. As it has been a while and there are new members on model-boats.com, perhaps this should be discussed again. As usual, chime in with your opinions.

Some of my boats (usually kits or RTR models given to me by others) have factory made shafts and props.

My focus here is on home made shafts, stuffing boxes, and props.

Seems some people go to a great extent to make the shafts and stuffing boxes (materials, bearings, etc.). I make my own out of copper/brass tubing (usually K&S) soldered together. There is a gap between the shaft and outer tube filled with Vaseline (petroleum jelly). I also added a filler tube near the motor end. Make your own length. Simple and no leaks over all these years.

As for props, the last few I designed as 3D printed them using ABS. Sure, I can't get a high polished brass finish on them but then I haven't seen many ships with that kind of finish. Virtually no expense, just time. If I want more, no problem. I probably spend less time in making a prop than searching for one. Two, three, four, five blades, whatever. ABS is tough but I can always print another. Not to mention replacing a lost prop.

Anyway, that's my opinion.

Lew