High RPM shaft seals?

[petn7]

Dave (or anyone else),

I recently installed a brushless motor into my SWM WTC. With my battery, motor, and ESC set up, the prop is spinning at over 33,000 RPM. How have you handled the WTC shaft seals on your Sushi or other high powered submarines? Is there some trick, or does one just have to cut down on the RPMs (this is what I have done for now)? The SWM WTC has a brass bushing that gets VERY hot. Would replacing it was a rulon bushing help to significantly reduce this heat?

Any thoughts or suggestions would be appreciated.

[fgroza]

Re: High RPM shaft seals?

That is faster than most motors run. Grease or oil should help .
Frank

[bigdave]

Re: High RPM shaft seals?

A Rulon bearing can only help but I don't run my props that fast even in the Sushi.
I am using a more powerful motor in my Sushi and Waterslider combined with a higher pitch prop.
This has its own set of problems, mainly torque roll.
Both the Sushi and Waterslider have a lot of weight in the keel and very large tail surfaces to try and counter the torque.
With that kind of RPM you will make a lot of heat, even with cup seals. But thankfully water is a great cooling device. BD.

[petn7]

Re: High RPM shaft seals?

Thanks for the input.

Yeah, it's probably better to go to higher pitch/bladed props and lower RPMs. Maybe I'll look for another type of prop.

I have also been thinking about going to high RPM ball bearings to help reduce heat.

Dave: what kind of props do you use?

[bigdave]

Re: High RPM shaft seals?

The Waterslider uses a high pitch Graupner racing prop.
The Sushi uses a seven blade Engel prop for the Lafayette.
Not sure of the exact sizes. BD.

[Guest]

Re: High RPM shaft seals?

Those are very high RPM's. We are dealing with displacement hulls, unlike high speed planing hulls, so there is limit to how much speed we can achieve without requiring stupidly high amounts of power and ever decreasing returns (inverse square law- double the speed, four times the power).

The Germans modellers are well experienced in this area with their subdogs/dolphins etc. They tend to aim for RPM's of about 8-12000 RPM with larger props. Torque roll can be compensated for in a couple of ways- contra rotating props or the use of twin levellers set at 45 degrees and independent control of the rear dive vanes. Each method has it's pros and cons.

You may want to look at DU-B bearings. These are bronze bearings impregnated with PTFE. They are designed to run in water, or even dry, but the water will act as a lubricant and will remove heat.

[petn7]

Re: High RPM shaft seals?

Those are very high RPM's. We are dealing with displacement hulls, unlike high speed planing hulls, so there is limit to how much speed we can achieve without requiring stupidly high amounts of power and ever decreasing returns (inverse square law- double the speed, four times the power).

The Germans modellers are well experienced in this area with their subdogs/dolphins etc. They tend to aim for RPM's of about 8-12000 RPM with larger props. Torque roll can be compensated for in a couple of ways- contra rotating props or the use of twin levellers set at 45 degrees and independent control of the rear dive vanes. Each method has it's pros and cons.

You may want to look at DU-B bearings. These are bronze bearings impregnated with PTFE. They are designed to run in water, or even dry, but the water will act as a lubricant and will remove heat.

Thanks for your thoughts Sub culture. I agree, 30,000+ RPMs is probably pointless and I never really intend to use such high RPMs, but as long as my motor + ESC + battery combination could produce that sort of power, I wanted a drive train that could at least handle it for short periods without permanent damage to the submarine.

Some neat ideas to think about.