So You Say Your WTC O-rings Don't Seal Anymore?

[Bob Gato]

Everyone seems to concentrate on the o-ring and the groove. And yes, probably the o-ring has shrunk a bit. From my days in another life of Skydrol and 5606A hydraulic fluid I started thinking about back-up rings. These are flat "shims' that reside in the groove on either side of an o-ring. their purpose is to prevent the seal from going oval and consequently losing some diameter. Maybe when troubleshooting a Leaky McSqueeky -double check the groove's width and not just it's depth in relation to the o-ring.

[Subculture]

My understanding is the use of backing rings are to prevent o-ring extrusion which can occur at high pressures e.g. well past 1000psi.

[Bob Gato]

If the o-ring groove is too wide.backing rings will prevent the o-ring from squishing out and reducing its intended diameter... Another case for thinking outside of the box... I know we're not talking about 1,000 PSI here.. but with possible loose tolerances, if you can keep the o-ring from squishing out to the sides it should stay proud enough to seal.

[RCSubGuy]

Good point, Bob. I like your thinking.

David's grooves are typically a tad wider than the seals in the older SubDrivers. This could definitely help, but the fabrication may be beyond the skills of the average modeler.

[Subculture]

O-rings have to squish in order to seal though.

Grooves should ideally be wider than the o-ring. The amount varies by o-ring, but tends to be about 1.3-1.4 times the rings cross-section.

This gives the o-ring a bit of space to expand and also allows it to roll slightly when you wish to release the seal.

https://www.globaloring.com/o-ring-groove-design/

[Bob Gato]

Thanks for posting Global O-ring's specs ...All I am saying is that if all else fails and since most model subs are built with one eye closed an arm extended with the thumb up in true seat of the pants form, maybe the width of the o-ring groove should be checked with respect to the width of the (new) o-ring being used. If the groove exceeds limits putting a shim of sorts couldn't hurt to try. -While you are at it check the groove's depth also...

[redboat219]

I remember someone posting here about wrapping the endcap o-ring groove with plumbers' teflon tape to help the o-ring seat better.

[RCSubGuy]

I remember someone posting here about wrapping the endcap o-ring groove with plumbers' teflon tape to help the o-ring seat better.

Yes, I've had good luck with this solution. First and foremost, however, I'd swap out the o-rings for new ones. It makes a big difference, as I do notice they seem to shrink over time.

[JHapprich]

Exactly! Teflon tape into the grooves and reinsert the O-ring! Helped me yesterday as i replaced the cylinder of my zb-1 for a new lexan tube.

[Subculture]

You can purchase o-rings in incrementally cross-sectional sizes. That can help if you have a poorly made endcap and the o-ring hasn't enough compression to seal effectively.

[Bob Gato]

Exactly! Teflon tape into the grooves and reinsert the O-ring! Helped me yesterday as i replaced the cylinder of my zb-1 for a new lexan tube.

Congrats ! you just made Teflon backup rings... The plumbers tape is probably the better option... I'm glad it worked out.

[JHapprich]

Oh i just am too lazy to cut those grooves deeper to make space for a thicker o-ring to match the slightly larger diameter of the new tube. Tried that method and it works nicely!

In my older (dry hull) models i use really fat o-rings from plumber's hardware as a seal. They are squeezed about 2mm wider in the tube. These seals never ever failed in decades.