Very soft stretchy rubber grommets, where from?

[Ian PParticipant @ianp]

I need to 'near hermetically) seal a cable where it passes through a panel without removing its moulded-on connectors.

Ideally a 'Polo' mint soft rubber washer is stretched over the connector which is then passed through a shouldered bore, on either side of the rubber ring are pairs of 'D' shaped blocks (thick washers cut across the diameter). End pressure is then applied so that the rubber sandwiched is compressed so that it seals on the bore and on the cable OD.

I know my soft/stretchy' description is like a piece of string but normal 70 Shore O rings are far to hard and probably would not stretch to suit a cable of 5mm and a connector of 20mm dia. On examples I have seen the rubber is more like Jelly Babies, if anyone remembers those!

Googling for soft rubber rings is likely to lead one astray! so I'm hoping someone here might know of a suitable source.

Ian P

[Ian PParticipant @ianp]

[David George 1Participant @davidgeorge1]

Have you thought of splitable cable glands there are a few manufacturer's here's one https://www.icotek.com/en-uk/product-catalogue/cable-glands/

David

[Brian Sweeting 2Participant @briansweeting2]

I think I know the type of thing you are looking for but for the life of me I can't name them.

In the meantime is there anything suitable from this grommet company….

**LINK**

[Clive Brown 1Participant @clivebrown1]

Could you use self-amalgamating rubber tape?

[HughEParticipant @hughe]

Ian , have you considered making some moulds and using a potting compound used in the external cable joining process. I think Srewfix sell it. Certainly TLC do.

[not done it yetParticipant @notdoneityet]

Some formers (like shuttering for concrete pours) and an elastic silicone sealant?

[HughEParticipant @hughe]

Ian, can't find it on screwfix site but magic gel on the toolstation site might do the trick.

[Speedy Builder5Participant @speedybuilder5]

Perhaps a normal grommet, cut through on one side and super glued once in position?

[John HaineParticipant @johnhaine32865]

Surely the process by which you get the cable through the panel without removing the connectors should allow you to fit a normal cable gland at the same time? 😉

[Grindstone CowboyParticipant @grindstonecowboy]

Maybe this 'mouldable glue' would do? **LINK**

[Neil WyattModerator @neilwyatt]

Why not mould a grommet in place using a silicone based putty like Sugru or Kintsuglue?

Neil

[Clive FosterParticipant @clivefoster55965]

Tried the cut a normal grommet and superglue suggestion from Speedy Builder5. Worked for a while but after a year or three the glue came unglued. Not sure how long it actually lasted. Know it was fine after one year but noticed it was unstuck after three.

Probably do better with the special glue supplied with split CV joint gaiters and similar flexi-rubber under car duties.

When dealing with small bonding areas and less than rigid substances correct glue choice seems to be the secret of success. Trouble is the right glues seem to be expensive and / or hard to get. Even when they claim to be suitable for difficult materials the consumer, blister packed, versions don't seem to be anything like as effective as the real thing.

My success rate is something like 1 in 3 with ordinary consumer glues on difficult materials. 100% when I've been able to lay my hands on the right stuff.

Clive.

[Ian PParticipant @ianp]

Some good suggestions, thanks all.

Picture is of an existing 'Pass-Thru' that is used on underwater camera housings, some used at depths over 100m and the housing and contents might be valued in tens of thousands of pounds so failure and leaks have to be avoided.

The rubber ring shown is one that split when stretching. As supplied it has a bore of about 6mm and an OD of 20mm. Because this particular camera is made in different lengths the sealed joint needs to be re-makeable to suit the cable on a particular setup.

The one shown is a standard commercial item so this size is not a problem, what I am trying to do is custom make some to suit very small (1.5mm) diameter cables that have 12-15m diameter connectors moulded on both ends of the cable.

I suppose that more important than the hardness of the rubber, is its stretch-ability, I have never used Sugru or similar products but it seems unlikely to me that its unlikely to have the properties of common or garden elastic bands, which is a bit what the ring shown feels like.

Ian P

[not done it yetParticipant @notdoneityet]

Castration rings might fit the bill?

[JuddyParticipant @juddy]

could you possibly cut a slice from a soft rubber hose such as this

**LINK**

[John HaineParticipant @johnhaine32865]

Posted by not done it yet on 07/02/2019 14:14:52:

Castration rings might fit the bill?

or the bull…

I'll get my coat.

[Michael GilliganParticipant @michaelgilligan61133]

Ian,

A while ago, I was recommended to try Bentley Advanced Materials : **LINK**

https://www.benam.co.uk/products/silicone/

These products may be ideal for your application

[ they were a little costly for my immediate need, but yours is in a different league ]

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Suggestion:

Use a silicon rubber ring. Compress it by a washer with chamfer. (Ideally without having to cut the washer. )

Bolt the washer to the panel so that when the fixings are tightened they compress the silicon rubber to seal against the panel and against the cable.

Howard

[Benjamin DayParticipant @benjaminday94198]

If you don’t mind a little messing about, this stuff is pretty straight forward. This one sets to 40 shore but other grades are available.
EBay item number 123090909279

[Benjamin DayParticipant @benjaminday94198]

Or run a generous bead of cheap bathroom silicone around a 6mm rod and let it set……..

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Benjamin Day on 07/02/2019 17:57:52:
Or run a generous bead of cheap bathroom silicone around a 6mm rod and let it set……..

.

Honest question, Benjamin [because I've never tried what you suggest] : How likely is that to stretch to clear Ian's 15mm connector ?

MichaelG.

[Benjamin DayParticipant @benjaminday94198]

I would say quite likely to be honest. And it only costs ?1 from ?land so worth a try. Its Cheaper than E6000 elastic glue and available everywhere.

[Michael GilliganParticipant @michaelgilligan61133]

[Joseph Noci 1Participant @josephnoci1]

I required a similar solution to seal the tether command cable for a small underwater UAV – I found two options – SKIFFY, a company that supplies plastic and rubber fittings, screws, grommets, etc. They had a pale white grommet that was very soft – It was not a doughnut, but a panel grommet, ie, with a slit on the outer periphery to fit the sheet metal panel. The one I used was 8mm ID and 16mm OD and stretched over a 24mm plug with some lubricant applied. Some did snap in the process.

The second, and finally better option, was Silicon tubing from the local hospital – used in the peristaltic pumps, OD of 14mm, ID of around 6.5. I fed the tube into a metal tube of snug length, let an 8mm section protrude and cut it of with a Stanley type knife blade. That little ring stretched over 28mm internal without snapping. Make sure to get the silicon stuff – they also have what looked and felt like polyethylene which is unsuitable.

Joe

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