Source of green donuts for instrument tubing installation?

[Movses Babayan]

None of the usual suspects online produce results - or I don't search using correct terms.

[Pat Russell[_2_]]

Did you try "castration rings?"

[Dave Nadler]

On Friday, April 6, 2018 at 1:49:23 PM UTC-4, Movses Babayan wrote:
> None of the usual suspects online produce results -
> or I don't search using correct terms.

https://www.fleetfarm.com/detail/syrvet-100-pk-castrating-rings/0000000001081?gclid=Cj0KCQjwtZzWBRD2ARIsAIPenY0z6J zWoEngZUxpNpZMy6NoSeg4bzcJSxIvZ-8BlKB2YazHnoeCmpMaAnt6EALw_wcB

[[email protected]]

Did you search for "rubber grommets"?

[[email protected]]

Available from Farm Supply stores, veterinarians, Tractor Supply stores.
Note: I use them, but out here in the high desert, where double-digit humidity is the exception, not the norm, the rubber donuts dry out and crack after a few months. But then, considering their intended purpose, longevity is not a part of the design.

[Bob Kuykendall]

On Friday, April 6, 2018 at 12:02:45 PM UTC-7, wrote:
> Available from Farm Supply stores, veterinarians, Tractor Supply stores.
> Note: I use them, but out here in the high desert, where double-digit humidity is the exception, not the norm, the rubber donuts dry out and crack after a few months.

Fuel injector O-rings might work; they tend towards large cross-sections and small IDs.

[[email protected]]

I dont use the docking rings anynore, after a few years they deteriorate to mush. I now use a short length
of silicon tube that fits over the instrument tube, a much better lasting material, and cheap.
Dave

[bumper[_4_]]

On Friday, April 6, 2018 at 4:55:52 PM UTC-7, wrote:
> I dont use the docking rings anynore, after a few years they deteriorate to mush. I now use a short length
> of silicon tube that fits over the instrument tube, a much better lasting material, and cheap.
> Dave

Silicone is a good choice. If you prefer O-rings, though you cannot always go by color, green ones are used in auto air conditioning system seals and indicate HNBR. This would be a particularly good rubber for glider tubing "clamps" as well. See the link for HNBR characteristics:

http://www.mantaline.com/capabilities/material-expertise/hnbr-rubber/

bumper

[krasw]

Is there a particular reason to use donuts or anything similar at all for instrument installation? Just push the tube to pneumatic port and go flying.

[[email protected]]

Using them prevents leaks later on, clamping the tubes.

[krasw]

On Monday, 9 April 2018 10:05:36 UTC+3, wrote:
> Using them prevents leaks later on, clamping the tubes.

I have fixed two leaks in pitot static systems over the years. Both were caused by clamped fitting. That's when I started to take seriously the instruction to never clamp pneumatic tubes with anything. Silicon tubes are idiot-proof, PVC tubes age and may become loose if fitting is connected frequently, the fix is to shorten the tube few centimeters and then plug it back.

[[email protected]]

On Friday, April 6, 2018 at 10:49:23 AM UTC-7, Movses Babayan wrote:
> None of the usual suspects online produce results - or I don't search using correct terms.

Movses, I have a bunch because I had to buy 100 of them. I only needed a dozen. I'll bring them to BoD this Tuesday.

-Kevin

[AS]

On Monday, April 9, 2018 at 3:05:36 AM UTC-4, wrote:
> Using them prevents leaks later on, clamping the tubes.

Has anyone ever tried a short piece of shrink-sleeve - no longer than the barbed fitting on the instrument - over the tubing? Slip it into place and hit it with a hot-air gun. Should shrink uniformly before doing damage to the tubing.
Uli
'AS'

[[email protected]]

"Has anyone ever tried a short piece of shrink-sleeve - "

Probably not a good idea. It will help the sealing, but the contraction when heated does not impart a lot of actual compressive force. Also, you will need a razor knife to get it off, which will likely damage the tubing.

I like these:

https://www.amazon.com/Wingsmoto-Tubing-Spring-Motorcycle-Scooter/dp/B012MBHEHQ

8.5 mm may not be exactly the size you need.

[Eric Greenwell[_4_]]

krasw wrote on 4/9/2018 12:39 AM:
> On Monday, 9 April 2018 10:05:36 UTC+3, wrote:
>> Using them prevents leaks later on, clamping the tubes.
>
> I have fixed two leaks in pitot static systems over the years. Both were caused by clamped fitting. That's when I started to take seriously the instruction to never clamp pneumatic tubes with anything. Silicon tubes are idiot-proof, PVC tubes age and may become loose if fitting is connected frequently, the fix is to shorten the tube few centimeters and then plug it back.

Yep, use silicone tubing. It doesn't age like the clear plastic stuff, and remains
easy to push on and pull off. My glider came with the plastic lines for the pitot,
static and TE, so I shortened them, then added back the length needed with a
barbed plastic fitting and silicone tubing. No more tubing problems, and easy to use.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf