Alec, How do you compensate the oil? I'd love to try some of those 36 volt Minn-Kotas. They've got a ton of umph, and might get me back a couple of hundred pounds of payload from George's Model-T Rex style thruster cans. And it would be cheap, too. Vance
I had an email conversation with Carl about a year ago on that topic. They're just straight air compensated, with Swagelok SS fittings tapped into the trolling motor casings. The reason I'd contacted him was to ask whether he was using air, because some on here maintained that at his depths, the partial pressure of O2 in air would be a fire hazard. I think his sub demonstrates it's not.
BTW Snoopy's trolling motors started out air compensated and are now in their second season with oil compensation. I have nothing at all against air compensation, and would go with that if my air bottles were outside the hull. But the way it was implemented on Snoopy the air was passed through the shafts from the cabin, and there just wasn't space to do it properly along with the cables. What's been interesting about the switch to oil is I can't notice ANY difference. The motors seem to pull just as strong, and even sound exactly the same as before.
cheers,
Alec
Oil compensated DC motors work just fine at moderate depths. Alvin had problems originally with brushes arcing, but he Hymak 5 hp motor used by Hyco on nearly everything they built was a serious workhorse. You get to tear it down and change brushes periodically as they wear faster, and they'll get the oil dirty, so you'll have to watch that. I was on Karl Stanley's web page last night and it looks to me like his Idabel is using about a case of trolling motors, and they must be compensated, as the sub is rated for 3000 foot service. Maybe we ought to ask him what the secret is, if any.
Vance
-----Original Message-----
From: DJACKSON99@aol.com
To: personal_submersibles@psubs.org
Sent: Wed, 15 Nov 2006 10:35 PM
Subject: [PSUBS-MAILIST] Oil Compensated Thursters
Can anyone support this statement: "Scripps has tried to fill the DC motors with oil, but the oil gets between the brushes and the commutator, where the insulation properties of the oil causes problems. Although it would be possible to use high voltage to break through the oil film, the high voltage is a safety hazard for the divers."
I was thinking about 24 or 36 volt oil compensated brushed trolling motors, but after reading the above I looked and could not find any examples of oil compensated brushed motors under 100 volts.
What are your experiences and thoughts?
Thanks
--Doug J
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