Looking for alternatives to teflon tape to loose end caps


#1

I'm having a heck of a time working with the tape. I find it end up bunching up and having strands cross over the o-ring after pushing the end cap off and on.

Are there o-rings that are slightly wider in diameter that we could order to close the gap in tolerances of the electronic tubes instead?


#2

John stager made the grooves wider and deeper with a lathe to get on bigger o-rings.
http://openrov.com/forum/topics/another-fix-for-the-end-caps-in-electronics-tube-being-loose


#3

Brian,

There are some tricks to putting the Teflon tape on correctly, mostly related to managing where the edges of the tape end up. Colin and I have got a system pretty much down which we can show you (and hopefully document) soon.

In the mean time, I might also recommend only using one O-Ring (we usually use the inner one) on each end cap. This will work just as well at keeping a seal, and is less likely to result in leaks from lack of concentricity. If you do this, your Teflon tape should be able to stretch over the inner face of the end cap so the edge of the tape doesn’t get caught on anything.

For the future, we are looking into switching to a single, fatter O-ring end cap design that could handle worse tolerances. We’ll keep you in the loop with what we come up with!

Eric


#4

I got ahold of some 1/8" O-rings that I was hoping would work (they do barely fit into the groove) but they were thicker and they didnt work. Not fruitful. However I was thinking I could sand down the inside of the tube or something to force them to work (I dont have a lathe). But I didnt get that far as I just went with tape. If you want me to send some to you to play with let me know in a p.m.


#5

Id like to bump this discussion up again. I am competed with my build and unfortunately am failing the waterproofness testing. I have a 2.4 design with the single O-ring. I have been trying the teflon tape with no success. I am up to 3 layers with what seems like increasing problems. Has anyone figured out a better way or other ideas? How are you using the

I did get a vacuum pump and to test the seals, put about a cup of water in the housing to see where the bubbles were coming through. Im thankful that my potting is holding up well but I find each time have several places that the air is bubbling in around the o rings when under vacuum.


#6

John,

I’m sorry to hear about your troubles. Would you mind sending a photo of the end cap pushed into the tube as you would have it for a dive? I’m not sure if there are any specific ideas that will solve the problem, but I’ll see if anything makes itself apparent. I hope we can get this figured out for ya!

Eric


#7

Thanks for taking a look. I reapplied the teflon to the non potted one and got an improved vacuum hold... I don't have time tonight to try the wire end. The wire end is tough to get the teflon straight with the wire bundle in the way.

I may try to drizzle a bit of solvent in the groove to see if there may be some channeling from an incomplete assembly.

With the vacuum pump, how many inches of Hg are you pulling? I have been having a hard time getting to 5 inHg and i think that is a depth of only about 5-6 feet.

1517-IMG_4625.jpg (3.41 MB) 1518-IMG_4628.jpg (3.67 MB)

#8

ok, I think I have the O-ring problem solved. I changed approach on the teflon tape and it it a very tight fit. While vacuum testing I found a few drops that made it into the housing from the motor leads. This may be where I am getting an issue when trying to use the horz thrusters in the water, they cut out immediately and the BB turns off while the vert motor works well. Im guessing a short or exposed wire in and around a motor.


#9

John,

I'm glad to hear you're making some progress. You may want to coat the part of the motor leads that you think water is getting in from with liquid electrical tape to prevent "hosing" as I call it where water travels down a wire between the conductor and the insulator.

For batteries, are you using the 26650 batteries we've been recommending? Unless you're on throttle setting "5" (OpenROV cockpit starts on setting 3 by default) the ROV should not brown out with two thrusters running. Perhaps only one of the battery packs is actually giving you power..

Also, when you apply the Teflon tape, you may want to take extra care to make sure there are no wrinkles in it that form as these may create a path for water to travel beneath the O-Ring. The Teflon tape I use is wide enough that quite a bit ends up hanging over the inside edge of the endcap (which I just bend over against the inside face). It looks like in your photos that the tape your using doesn't quite make it to that inside edge.

I think I wrote it down somewhere on the forums, but if you like, I can let you know the specific brand of Teflon tape we've been using.

I hope this starts to work out for you!

Eric


#10

I am using the recommended batteries. In my bench tests I was able to run all 3 motors full speed with the lights on high with no issues. Granted no real load in the air but I think the batteries are good. I think I may have exposed leads in a motor circuit that only draws when trying to power the horz motors. I built the motors to the instructions but must have been a bit sloppy. I may try the hot glue technique and pull a vacuume on the wires to try to plug the wire ends. I need to look up the posts on dip sealing the motors again. Anyone used some sort of electronics varnish to seal up this area?

I did the Teflon on the O rings a bit different this last time. I let the entire width of the tape go into the groove. Sort of applied it perpendicular as apposed to flat parallel. My thought was that as long as I didn’t twist the tape, any ripples or creases in the tape would be parallel to the O ring and not across. It made for a very tight fit. That part seems to be working well. My vac pump will only get up to around 15 inHg but it seems to hold. That’s when I found the jacketing. I submerged the unit while pulling a vacuume. If I didn’t have the motor issue I would just strip a bit of mid wire insulation, tin it and do the hot glue/shrink wrap.


#11

Has anyone considered / tried making the channel of the endcap a bit shallower by filling it with a thin film of acrylic glue (and I mean glue like Acrifix S116 which adds real material and is not just a solvent the cement we're using to assemble the acrylic parts) ?