Ballast system ideas

[subt1]

I am trying to make a mini rov and at the moment am trying to design the ballast system for it.
Initially I thought of using a bladder in the bottom of the rov and pumping water into and out of it, which would make the rov dive or surface. For this I would use a bladder (I have seen some available primarily used for air but I assume they would take water) a pump which can go in reverse as well and maybe a solenoid/valve (I’m not sure if this is needed or if the pump would stop the water from going the wrong way. Does this sound like it would work? I would obviously then have to make my rov buoyant in the first place; I’m assuming this can be done with foam?
If this doesn’t work then I might use the method of pumping air into the bladder. My question with is, does the air have to be pumped from a specific tank or can it just pump air from within my rov, I understand the pressure will increase but shouldn’t do by much. What sort of valve would you use with this?
I’m trying to build it as small as possible so I don’t know if any of these lean towards being a smaller system. Any help/guidance would be appreciated.

[JWLaRue]

Re: Ballast system ideas

Welcome to the SubCommittee forum! You've come to the right place for answers.

Either method that you proposed will work. There are a number of r/c sub guys who have built systems using a bladder as the ballast 'tank.' To get you started with some more details, check out this web link from one of our members:

http://www.frontiernet.net/~bwelch/ballast.htm

Dave does a very good job at explaining how either type of ballast system can be constructed.

Let us/me know if this helps and please feel free to continue asking questions....we're always glad to help.

-Jeff

[Guest]

Re: Ballast system ideas

If you want to trim your sub for negative buoyancy or adjust for different water densities, then your initial method of pumping water into a bag will work best.

If the ballast volume is relatively small, then peristaltic pumps are reversible and don't require a check valve. They permit very accurate metering of the water, but do tend to be a bit slow, which is why they're best suited to smaller volumes.

Ebay is quite a good place to pick up cheap pumps. Bags suitable for use can be anything from a balloon to something like an iv bag.

Another solution is to pump into a large syringe instead of a bag.

[subt1]

Re: Ballast system ideas

Thank you for the advice. Will check out the link to compare the two systems again. I want to keep the rob as small and light as possible so i guess peristaltic pumps would be good. I'll do a bit more research and see if there are any other questions that come up....

[Guest]

Re: Ballast system ideas

One other thing worth mentioning as you say you want to keep things small- peristaltic pumps do tend to be a bit chunky compared with other types of pumps.