My new BLOG

[turtle]

hi anychance you could put a pic up how you done the motor shaft seals.
adam

[Silver dollar]

You don't need the balloon. The oil is not compressable, so if you don't have any airbubbles it will have the same volume 100 feet under water as on the ground.

[martinw]

Hi Silver Dollar,

It's virtually impossible to remove all the air bubbles, especially in a system like the one I'm designing, unless you vaccum everything (not really practical), so the compensator takes this into account.

It also takes into account any volumetric changes of the fluid due to changes in ambient temperature

http://www.engineersedge.com/thermodyna ... d_prop.htm

Martin

[Silver dollar]

Ok, didn't think of the temperature diff.

[martinw]

My thruster has now developed a bit more thrust for some reason

http://martin-wareham.blogspot.co.uk/20 ... hrust.html

Martin

[KR2_Diving]

I had a similar issue with my test tank! What I found to work very well with fill the tank as full as possible, then give it a Cling Film lid. This reduces the chance of air getting caught up in the water causing cavitation.

Just a though. Mind you, I had a much smaller tank to begin with...

[martinw]

Thanks, I may just do that

Martin

[marcane]

The hoses to the thrusters will act as compensators, really dont think you need the baloon.. have you made the ESCs yourself? Can you run the motors directly into reverse without breake? That is an issue I have om my thrusters, i have to give the the thruster two reverse signals to actually get reverse.. im running brushless outrunner, car ESC and polulu mini maestro to run it from the computer..

Best regards

[KR2_Diving]

That is an issue I have om my thrusters, i have to give the the thruster two reverse signals to actually get reverse..

Hello Marcane!
I had a similar issue myself at first... then I got the programming card for my ESC and was able to activate "Rockcrawler mode" which allows a direct transition from FWD to REV.

I am by no means an expert on ESC's but from what I gather, the "double reverse" you speak of is a feature to prevent accidental braking during an RC race. During my research, I found many ESCs that required the double signal, but then found that by getting the appropriate programming card, or by entering the programming mode of the ESC, you can change the settings to allow for direct REV.

Perhaps someone who knows a bit more about this topic could start a new thread? (or point us in the direction of an existing thread?)

Ryan
"KR2_Diving"

[martinw]

The hoses to the thrusters will act as compensators, really dont think you need the baloon.. have you made the ESCs yourself? Can you run the motors directly into reverse without breake? That is an issue I have om my thrusters, i have to give the the thruster two reverse signals to actually get reverse.. im running brushless outrunner, car ESC and polulu mini maestro to run it from the computer..

Best regards

It really depends on the volume of oil I end up with in the system, and I may at some point want to apply a slight positive pressure (with a spring) so if there is a leak fluid goes out rather than water coming in. If I get really fancy I may put a sensor on the compensator (the balloon was just for illustrating a concept) to measure the volume of fluid in it so I can tell if I have any leaks, and possibly how fast the leak is

Simple Compensator.JPG (12.29 KiB) Viewed 3547 times

And yes I have made my own ESC, so I have complete control over the firmware/software in the microprocessor

Martin