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Gina

All Sky Camera Revisited

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Maybe you can incorporate an O ring somewhere.

Dave

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1 hour ago, Gina said:

Maybe just grease would work better that sealant.  Or perhaps a greased paper gasket - works for engines.

indeed...

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6 minutes ago, Starlight 1 said:

Try 2 pack epoxy , use it alot on RC boats.

Yes, no doubt that would work - I'd be surprised if it didn't but I'm surprised silicone sealant didn't work.  Bit final though - to get inside any time in the future, if a problem arose, would mean breaking the casing.

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Posted (edited)

Just tried to separate the casing parts at the flange and it's stuck solid most of the way round.  So much so that the casing has broken trying to prise it apart!!  OTOH the seal for the USB cable, also apparently well sealed with lots of sealant is leaking profusely.   Looks like I need to change the design completely.

Edited by Gina
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Hi Gina, we used to use a product called aquafix made by soudal....hands down the best sealing mastic I ever used and around £4 a tube on ebay, it's thick stuff and helps to place the tube in a bucket full of warm/hot water so it flows better.

https://www.ebay.co.uk/itm/All-Weather-Sealant-Soudal-Aquafix-Even-Seals-Under-Water/111233914303?hash=item19e60ed5bf:g:~FAAAOSwF1dUPreH

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12 minutes ago, Gina said:

Just tried to separate the casing parts at the flange and it's stuck solid most of the way round.  So much so that the casing has broken trying to prise it apart!!  OTOH the seal for the USB cable, also apparently well sealed with lots of sealant is leaking profusely.   Looks like I need to change the design completely.

Have you a lathe Gina?

If so you could consider printing the mating flange surfaces with loads of skin thickness and then face the flanges and machine a 2mm deep x 3.2mm wide O-ring groove into one, for a BS1806 2.62mm cord dia O-ring in whatever ID you need.
Bit too lush maybe?

 

Tony

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Can you use some sort of  cable glands ? they're IP rated, don't know if they're pressure sealing though.

Dave

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1 hour ago, tonyowens_uk said:

Have you a lathe Gina?

If so you could consider printing the mating flange surfaces with loads of skin thickness and then face the flanges and machine a 2mm deep x 3.2mm wide O-ring groove into one, for a BS1806 2.62mm cord dia O-ring in whatever ID you need.
Bit too lush maybe?

 

Tony

I do have a lathe but can't get at it ATM.

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Posted (edited)
51 minutes ago, Davey-T said:

Can you use some sort of  cable glands ? they're IP rated, don't know if they're pressure sealing though.

Dave

I'm using grommets for the pressure tube and 7-core cable.  These seal fine without any sealant.  The water tubes go through printed pipes as part of the base which are smaller than the OD of the tubes so these fit tightly and also seal fine.  The dome has also sealed well with no sign of a leak.  The problem areas are the main flange and the USB cable.  I could cut and join the USB cable then it can go through a grommet and solve that problem.

Edited by Gina

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Just now, Gina said:

I'm using grommets for the pressure tube and 7-core cable.  These seal fine without any sealant.

Was your USB cable just clamped ? may work better with a gland giving a rubber seal, I think the conical ones used in glands actually tighten up if subjected to pressure.

Dave

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I do any lathe work for you Gina ,its only a little lathe so not over 5 ins round or it not fit in. 

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36 minutes ago, Davey-T said:

Was your USB cable just clamped ? may work better with a gland giving a rubber seal, I think the conical ones used in glands actually tighten up if subjected to pressure.

Dave

Clamped and sealed with silicone sealant - oodles of it.  Should have sealed alright.

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27 minutes ago, Starlight 1 said:

I do any lathe work for you Gina ,its only a little lathe so not over 5 ins round or it not fit in. 

I'll bear that in mind, thank you, but I want to get the ASC working again for tomorrow night if possible as it's forecast to be clear.

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2 minutes ago, Gina said:

Clamped and sealed with silicone sealant - oodles of it.  Should have sealed alright.

I don't think silicone sealant is all it's cracked up to be, OK in a thick layer round your bath but less so for thin layers or trying to squish round things with your fingers :grin:

Dave

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Posted (edited)

Yes, I've come to that conclusion!  Though this was squeezed between 3D printed parts.

I have some 4 core screened cable I can use for the USB and that can go through a grommet.

Edited by Gina

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Posted (edited)

To retain the mirror flat surfaces on the 3D printed parts I think I shall design and print two rings to hold the O ring in place - one inside and one outside with the outside one having the clamping holes.

662105967_Screenshotfrom2019-05-0817-56-34.png.331a203018b9151c41afd2ec70476931.png

Edited by Gina

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Printed those parts and now printing a new base plate.

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Still have clear skies forecast for the dark period overnight in spite of current total cloud cover with some of it very dark and looking like rain.  There will only be a short interval between moonset and sunrise though, and in view of that I don't think I'm going to "bust a gut" to get it all working by tonight.  Slow and steady generally gives better results.

The O ring is scheduled to arrive this afternoon.  New base plate has printed fine and I'm installing the cables and other parts.  I think I can use the present top - I've got most of the silicone sealant off it.  The inner ring that retains the O ring will also raise the camera to allow for the thickness of the O ring.  I also have the electronics to sort out.

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The O ring has arrived and I've assembled the ASC with O ring dry and it leaks but I haven't been able to find where by testing with soapy water.  It isn't easy to see bubbling down in the flange channel where the O ring is.  There is certainly no bubbling round the cables or tubes.  Guess the next thing is to take it apart again and grease the O ring and try again.

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I think the O ring would work better in a groove if that's feasible.

Dave

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I agree but to produce a smooth groove is not easy.  3D printing is not necessarily perfect.

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Added white grease profusely and reassembled.  Still leaks.  Not as badly but evident in two places around the flange.  So that's another idea gone.

I'm thinking the only solution will be to make the flange joint permanent and if I need to repair anything inside I'll just have to either break it apart or saw it open.

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Most of the clouds have departed and the sun is out so it would seem that forecast is probably right.  However, it also seems the chances of having the ASC working for tonight is vanishingly small

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