O-rings vs Gasket - sealing the block

[Long Haired Git]

I'm designing a cheap easy waterblock aimed for moderate performance.
It consists of a copper base and an acrylic top section.

For reasons I don't wish to discuss, I was hoping to use an o-ring between the two, but with no groove at all.

I was hoping to use a 2.0mm thickness o-ring that was quite compressible, thinking it would be around 1.0mm thick once fully compressed (D50?)

What chances of sealing?

My next thought was putting a smear of silicon sealant just "to be sure".

Failing that, I could get a (neoprene?) gasket. Ironically, it would be a round shape and again I'd be looking at it being 1mm thick or so once compressed.

However, an off the shelf o-ring is going to be lot cheaper than a custom neoprene gasket.

Advice appreciated...

[maxSaleen]

It might be cheaper to make a Cu top and smelt the two together. This would provide a better seal, and might be cheaper if done in mass production. If your going to use an O-ring, I would at least cut a groove in the block (unless of course your equipment doesn't allow for this).

[jaydee]

If you don't trust just silicone you could get some rubber gasket material in sheets and cut a peice to fit. Should have the stuff at an autoparts store. Just make sure your screw spacing is close, especially with a plastic top. I would just use clear silicone though. Once you tighten the bolts you can't even tell the stuff is there.

[TaTs]

I have used only silicone to seal this block.



I applied some of it and once the bolts were tightened it spread evenly. After 24 hours I tested it for leaks and voilá, it's been running for about 5 months with no problems.
If you are not planning on opening the block say, once or twice a week, silicone is definetly the way to go.

________
TaTs

[Cathar]

Yeah - I'd go with the rubber gasket material.

Heck, I even have some 1mm thick stuff here if you want me to send you some.

[jaydee]

Originally Posted by Cathar

Yeah - I'd go with the rubber gasket material.

Heck, I even have some 1mm thick stuff here if you want me to send you some.

Definatly a lot less messy. Easier to take the block apart to.

[Long Haired Git]

Originally Posted by maxSaleen

It might be cheaper to make a Cu top and smelt the two together. This would provide a better seal, and might be cheaper if done in mass production.

Nah - my block will be very cheap. Just the material cost of a copper top is more expensive than the machined acrylic top, let alone the effort to drill and tap barb holes. It also means I cannot take it apart, which is not really acceptable due to other constraints. Thanks anyway.

Originally Posted by maxSaleen

If your going to use an O-ring, I would at least cut a groove in the block (unless of course your equipment doesn't allow for this).

Equipment should be fine as I have none and will get it professionally made. The issue is that an O-ring groove, in its design, means that the two surfaces being seperated now touch each other. It my cases, I don't want this. The groove is also machining I wish to avoid.

Originally Posted by jaydee

If you don't trust just silicone you could get some rubber gasket material in sheets and cut a peice to fit.

Ta - this is firming as an option but I will discuss further below.

Originally Posted by jaydee

Should have the stuff at an autoparts store. Just make sure your screw spacing is close, especially with a plastic top.

Define close? I have approx 30mm between hold-together bolts. Close enough?

Originally Posted by jaydee

I would just use clear silicone though. Once you tighten the bolts you can't even tell the stuff is there.

As per above, I need the o-ring or gasket in order to provide some spacing.

Originally Posted by TaTS

If you are not planning on opening the block say, once or twice a week, silicone is definetly the way to go.

I think, though, that "smoothing" the gap between the top and bottom caused by the o-ring with silicon goop has a number of advantages:
1) Cheap. Very little silicon material used per block, and silicon material is cheap. O-rings are more expensive than I thought, but I assume much cheaper than a custom gasket shape. O-rings at AUD$2.30 each? Sigh. Oh hang on, if I find a commonly used size they're like AUD$0.60. Phew!
2) Easy. A quick and easy job with no real skills required. Perhaps a minute per block including making it look good.
3) Professional. It won't look cheap, even though it is.
4) Simple: Joe-Blo has the tools at home to take the block apart, clean it up, put it back together and get it right. He/she could replace the barbs or o-ring or bolts if damaged without needing to buy them off me.
5) Protective: I can mark the silicon with a mark from a stamp and hence know if a block has been reassembled.

Originally Posted by Cathar

Yeah - I'd go with the rubber gasket material. Heck, I even have some 1mm thick stuff here if you want me to send you some.

My issue is simply how cheaply I can get 100 made. Cathar - you should be able to guess why I want the gap! 1mm thick rubber won't be thick enough when compressed. Can I double up? I can't find a URL online to know how compressible it is and whether I can thus get some that is approx 1mm thick when properly compressed.
Even so, I can't see how I can cheaply make them coz I waste so much material. Cutting them out by hand is out too - too time consuming. The benefit is I can use a custom shape of the rubber mate to make my block a little better, but the cost scares me.
Sigh.
In my searching I have come across "X rings" and also "Boss Gaskets". Not sure if they will be better for what I want to do?

[killernoodle]

X rings are like O rings, but are better at sealing surfaces that rotate around eachother. They are more commonly used on motorcycle chains and such. They also hold lubrication better than O rings. Really, the benefits of using X rings just arent there for waterblocks.

[R.A.Floyd]

Originally Posted by Long Haired Git

..Nah - my block will be very cheap. Just the material cost of a copper top is more expensive than the machined acrylic top, let alone the effort to drill and tap barb holes.....

So, when you machine the acrylic top, why don't you make a oval or rectangular (the last one is easier/cheaper to produce) chanel for the O-Ring right into the acrylic ?
If your top is thick enough, and you leave adequate space between the O-Ring's channel ane the acrylic sides - the construction will be quite strong.

Despite of the thickness of the O-Ring, it can be smashed so the two parts of the block will be practically touching each other IF the channel is accordingly machined. How to do this - look at the attached drawing (a well known picture about O-rings indeed, and I've tested it with a lot of them).

[Long Haired Git]

I don't want the top and base touching.
I am relying on the O-ring to provide a small seperation between the two for reasons I do not wish to discuss.
I am well aware of what the O-ring groove does, and how it is an intrisic part of the sealing process, and how it normally aides strength.

I was just hoping to avoid needing to use it.

Actually, strength is an issue I suppose. With only the O-ring between the top and bottom, I will have a fair bit of clamping pressure when the block is mounted.
I'll also need a thick copper base to avoid warping...

[jaydee]

Originally Posted by Long Haired Git

I don't want the top and base touching.
I am relying on the O-ring to provide a small seperation between the two for reasons I do not wish to discuss.
I am well aware of what the O-ring groove does, and how it is an intrisic part of the sealing process, and how it normally aides strength.

I was just hoping to avoid needing to use it.

Actually, strength is an issue I suppose. With only the O-ring between the top and bottom, I will have a fair bit of clamping pressure when the block is mounted.
I'll also need a thick copper base to avoid warping...

You're going to want to use a gasket instead. If you just use an o-ring and expect it to make a gap your going to crack the top when you tighten the screws.

Not sure what you want the gap for but it could be milled into the top. I have done similar myself as I to wanted a gap but I needed the acrylic top to sit as flat over the largest surface area I could so it won't crack. Just mill the area you want the gap down a little and leave the rest.