rva1945

I've just finished my next rc boat, an own design lifeboat. The stuffing tubes were homemade using tubbing for the axle and the casing, and bushing at the outer tip and a not sealed ball bearing inside. I included a lubing tube, too.

At the first trial, when I inserted the grease, it seemed to be too much and the motor could hardly turn the prop. Taking some grease away fixed it, but after almost an hour of running small drops started to appear flowing through the ball bearing, which is not sealed.

I added more grease until it appeared flowing through the ball bearing, flushing some water (which entered thje tubbing before) in the process. This time there was no water in the hull but lots of grease appeared exiting from the ball bearing, then suddenly there was no more grease and no more unwanted water even efter almost one hour non stop.

The question is: can I be satisfied with these results, I mean, did I fix the problem? Is it just about adding more grease as before/after running my boat?

The model is just a scale one, not fast, it's powered by two RS 380, 8.4V, driving 3 bladed, 33 mm (1.3") diam props, direct drive.

Please help me, this issue is puzzling me! Sorry if my English lacks some precision and please feel free to help me improve it.

Regards
Robet

jetpack

My Feedback: (1)

Just thinking...

If you stop the air from escaping through the top of the tube, you will prevent the water from following it. Is it possible to use a piece of heat shrink tubing to the stuffing tube and the shaft to form a seal?

rva1945

It seems as if air/grease/water escapes from the inner end of the tube because the ball bearing is not sealed. If it was, would it help? Don't sealed ball bearings have rubber as the sealing part? The grease will attack the rubber seal, I guess.

Regards
Robert

jetpack

My Feedback: (1)

Rubber sealed will help but rubber sealed will still leak. They are better than metal sheilds and are best left to seal out dust.

The problem with rubber sealed bearings is they still allow water, and once the water is in them it stays and rusts the bearing because it has a difficult time evaporating.

I think the best approach is to leave the system open as you can so water can be displaced and evaporated at the end of the day. The worst thing is to have trapped water during storage.

rva1945

Ok.

At the outer end, in contact with water, the stuffing tube has a bushing. The other end, inside the hull, it has a ball bearing. This ball bearing helps to stand the side load that the motor puts on the shaft.

If I replace the ball bearing with a sealed one I guess it will resist for long after giving in grease due to water preasure.

Anyway I think the issue is bushing-related, not ball bearing-related. In another model I've built, a tugboat, the stuffing tube is just less than 4" long, it is completely under water level, it has a ball bearing at the inner end; the shaft comes from a PC CD device (3mm stainless steel shaft) and at the outer end, the bushing (in contact with water), comes from that device too, both with extreme precision, obviously. No dripping here, even after hours running.

LtDoc

Robert,
Completely sealing a drive shaft seems like it isn't very common. If it were easily possible, I think the majority of kits (or scratch built) would use whatever that method was. A little bit of water seeping in is fairly common. As long as that 'little bit' isn't too excessive, or can be controlled, it isn't that much of a problem. Also why most manufacturers recommend airing out the boat between uses (evaporating the water).
It sounds like after the 'right' amount of grease was added, there was no more water seeping into your boat. One method of controlling the water entry is to do as you've already done, use the 'right' amount of grease. That probably means cleaning up the gob of grease inside the boat, but certainly a possible 'fix'. A small amount of water is 'normal' for most of us.
- 'Doc

rva1945

Ok, this last response left me more relaxed. I filled the stuffing tube with more grease again, this time there was no water but just a bit of grease spilled from the ball bearing, which, as far as it seems normal, it is no problem at all.

But I repeat: the stuffing tube which I built for the tugboat, seems to be completely sealed. At least for some hours of running time, I often add more grease as I see it's needed.

Thank