Tether buoyancy idea.

[PaulC]

Well as far as using styrofoam it depends on which type that you are talking about. If you are talking about the white "standard" type then one has to be careful to get the right kind, because there are different grades of it. Some of it isn't as strong as you think. And finally, styrofoam will compress at depth... check this out http://www.youtube.com/watch?v=zsOkbspVuuM. But to be honest with you with the depths that you all deal with at the MATE competition I really couldn't tell you, but I would look at using either the blue or the pink foam wall board. The blue is what I am currently using on my rov, but I also haven't had it below thirty or forty feet, but on my new rov the depths are going to be greater so I am experimenting with using pvc capsules. If you are doing this for a school project then you might try to get a donation of syntatic foam. But these are just the opinions of one person.

[bigbellydude]

Well, as for depth, the competition takes place in slightly deeper than standard pools, about 12 feet max. We are hoping to use this ROV in other places, however, and we would not want to have to haul it up over the edge of our maybe rented boat out on the lake. I think we might look at getting a larger diameter PVC pipe, put caps on both ends, and a screw on cap of sorts on the top. Before putting it in the water, we would open the screw cap to fill it with air, then close it tightly and hope it floats. We may have to do some playing around with it, but we will continue to do research.

[PaulC]

Hey bigbellydude do you have any pictures or drawings of your proposed ROV for the competition several of us on the forum may be able to help out if we had a better idea of what we are trying to help you work on. Granted I am by no means a engineer just a hobbyist and a 3d modeler.

[bigbellydude]

I am in the process of acquiring AutoCAD, AutoCAD Civil 3D, and Autodesk Inventor, through Autodesk's student software program. As soon as I get the software, I will make a quick drawing and post it in the MATE forum.

Josh

[sthone]

Someone posted these floats over at Robotrov and they might be worth looking into....

http://www.memphisnet.net/product/3761/floats_plastic

Still bulky and they would have to be attached during construction of the tether but still interesting, I might have to buy a few and fire up the pressure chamber to see what kind of depth they can handle.

-Steve

[PaulC]

Steve those are the second time I have seen those yes that would be interesting to find out the what depth those would be rated to.

[sthone]

I just ordered a variety of those floats to test out, I'll let you know how they are.

-Steve

[PaulC]

Cool that would be great I love it when I can hear about other peoples bench testings.

[sthone]

floats1.jpg (221.56 KiB) Viewed 3468 times

So I received my order of floats from Memphis Net & Twine Company, I ordered a few of each, the top row is a variety of the Hard Plastic Floats, first one in the second row is a 2" Dia Standard PVC Sponge Float, and then we have a few Hard Foam Floats.

I haven't actually pressure tested any of these but I'm guessing from there make up they will all be good for the depths most of use are looking to achieve.

The Hard Plastic Floats are pretty solid, they are made in two halves and joined together so they have a center cross section. They are hollow but have a wall thickness of about 1/8" (I cut one in half and will post a picture of it later) the down side is .... the hole through them is only 5/16" (for some reason I was picturing a 5/8" hole when I ordered them.) so you wouldn't be able to fit much more than a ethernet cable through them.

Both the PVC Sponge Float and Hard Foam Floats are pretty solid too, they are not what I expected at all, I figured they would be somewhat squeezable, they aren't. Which is a good thing, I think they should withstand some good depths, but I still have to test them. I still want to hack a few up to see in they can be cut down smaller (to be less bulky) and maybe see if the hole can be drilled bigger, because they too only have a 5/16" center hole.

I'll post more as I continue with my tests.

-Steve

[PaulC]

Has anyone thought of using either regular or synthetic cork for tether floats? It doesn't compress very much, and can be drilled.