[PSUBS-MAILIST] Air compensating thrusters

[Alan via Personal_Submersibles]

Jon,
the purpose of my email covering everything I've heard about compensating
was in response to Vance's suggestion that someone write a white paper
on it. So I was more interested in bringing out all the facts rather than debating
the issue. You bring out some more good points on the pros of a simple system.
This thread was started by James who had bought expensive thrusters &
wanted to get it right.
Cheers Alan

Sent from my iPad

> On 28/07/2014, at 1:44 am, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> Alan,
> 
> Everyone is correct...about their own experience.  This is a Ford vs Chevy debate with neither system being a perfect solution.  Primary use is likely going to dictate the best path to take, air comp if you can't sacrifice power reduction or risk brush issues in commercial operations, oil comp for simplicity in recreational operations.
> 
> Alec's experience is a pretty good story for recreational diving.  A 10 year life prorates to a cost of only $25/year for each MK101 and from a performance perspective he can't tell the difference between air/oil comp on a small minn-kota.  JimK's 7-ton Bionic Guppy gets muscled around easily with three oil comp'd MK 101's so they obviously have plenty of power even if its less than it would be with air comp.  That's enough evidence for me...no regulators, no extra gas to carry, no extra plumbing, no overpressure valves and no worries about maintenance or failure on all those small air compensated components.  At $255 for a MK101 lower unit, I'll just create a replace-one-motor-a-year budget.  No need to open the can, replace brushes, turn the armature; just replace it with a new one and I'll never have one motor that is more than four years old.
> 
> So you probably just want to toss a coin and pick a method.  Maybe start with air comp first on a new build because if you don't like it then converting to oil comp will potentially be easier than vice-versa.
> 
> Jon
> 
> 
>> On 7/27/2014 3:42 AM, Alan James via Personal_Submersibles wrote:
>> Thanks Alec,
>> I was intending to also mention your experience as a balance to the negatives
>> but got distracted.
>> The problem is that I am hearing a lot of conflicting stories.
>> Even with air compensation there are problems. Greg told me he had a problem
>> with moisture getting in through the exhaust valves of a second stage regulators.
>> I have put extension tubes around the exhaust manifolods of my ambient sub's compensating
>> regulators to try & stop this.
>> I dive mostly in sea water, which is not as forgiving as fresh, so want to get it right.
>> Emile was telling me about repeated problems with one of his sub's thrusters, & he is now using
>> expensive rim thrusters. I will leave it up to him if he feels like sharing the details.
>> The guys at Fugu sub with 30 years commercial experience are saying go with air, there are too many hasles with oil. All commercial oil compensating units have about 5psi overpressure which your system doesn't have. So who is right? 
>> Cheers Alan
> 
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20140728/3db5fa59/attachment.html>