SeaCharger build blog: see the latest progress on the project

THRUSTER

10/23/2014

This single blog post could never explain even a hundredth of the thought and work that went into the thruster. Months and months of design and redesign and prototyping resulted in what you see here. This is the first thruster with the outer tube of the housing removed. The two black things on either end are delrin end caps with various features machined into them. The gold thing is an R/C airplane brushless motor, the one with the lowest kV rating I could find in this size class (basically that means it's meant to turn slowly). It drives a 4:1 belt drive reduction using a GT2 timing belt. Then there's a magnetic coupling that transfers the power through the sealed delrin end cap to the propeller which would be to the left if it were present in this picture.

This thruster has about 25 days of run-time on it without any significant, noticeable wear. Not saying that's enough for 100% confidence in the design, but it's a good start.

8 Comments

Glaukon

2/2/2017 05:00:27 am

Hello there,

Congratulation for the successful recovery off the New Zealand coast. What are the specs for the brushless motor you used?

Damon McMillan

2/27/2017 08:06:41 am

Hi Glaukon,

Thanks for your interest. The motor was just a low-KV brushless motor from Cobra Motors. Nothing special.

Damon

Nick

11/10/2018 05:49:08 pm

Can you remmember the Kv of the motor?

Bruce Fitzsimons

4/17/2017 03:59:03 am

Hi Damon,

Can you give any more details/pictures of the magnetic couplings? Its a great idea, but I'm not sure if you used a thrust bearing on each side, or just PTFE (or just the delrin) for it to ride on?

And are you getting it back from NZ anytime soon? A postmortem would be fascinating and useful for others.

Thanks,
Bruce

Damon McMillan

4/18/2017 11:39:36 am

Hi Bruce, the propeller shaft was supported by a ceramic ball bearing on one end and a simple PEEK bearing on the other end. The ceramic ball bearing took the thrust load.

Seacharger will be in a museum in NZ until July, at which point I'll bring it back. I'm anxiously awaiting the opportunity to tear it down!

Thanks for your interest!

Bruce Fitzsimons link

4/25/2017 08:37:18 pm

Thanks Damon! I think I understand now, a single ceramic ball. Very nice, efficient and elegant.

I am collating a set of autonomous water vehicles on Reddit here: https://www.reddit.com/r/autonomousboats/ if you're interested.

You may like this one, I've seen some wave powered boats using a long tether but this guy has cracked it properly:

https://www.reddit.com/r/autonomousboats/comments/6621hu/commercial_autonaut_wave_powered/ (reddit link just because I found the patent which is more informative). It'd never be possible for a passenger craft as it's designed to rock as much as possible with the waves.

Thanks again.

andres barrios

1/21/2018 04:29:45 pm

congratulations for your project really is very cool, I have a doubt because you used a submerged propeller, being this more complex and more likely to fail, and did not use a normal system as used by sailboats or normal boats? Is the difference in performance better with the system you used?

Damon

1/22/2018 11:08:18 am

Thanks Andres!
The performance is probably a little better since the propeller is operating in less-turbulent water (the farther away from the surface, the less turbulent). Also, on a boat of this size, you have to assume that the whole boat will be frequently submerged. So even if I had put the propeller up near the surface, I'd still have to make sure it was completely waterproof.

THRUSTER

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