Hello all,
Thank you all for the feedback. I have really appreciated it. I have been making cylinders for almost 20 years. I have tolerated leaks and have taken measures to mitigate as I've made one offs, but when you are thinking about making these things for production, your mind expands and the implications become greater. A Simple thing like O rings and leaks become magnified.
I spent today dealing with 'O' rings. Last night I cut the grooves in the flange of the respective front and back end caps that I will use to prototype all the arrangements. Slipped the rings on and then placed the cylinder in my pool. So far so good, no leaks that I can see. The end caps are a tight fit and then 'O' rings press very firmly into the polycarb.
I then gave both end caps a coat of resin. In this heat, 30 degrees, dry in no time.
So this morning I checked the resin coat on the caps. Nice and dry, 10 am and already 32 degrees, high humidity. The plan today was once again to test the 'O' rings but this time I'm in the pool too.
After cooling off for 40 mins or so and holding the cylinder down half a meter I had a slight drip inside. Should do better than that.
I took the cylinder out and had a look at how the O rings sit in their grooves. The resin dried unevenly in the grooves creating high and low points. This would need to be sanded or turned out. I placed the caps on the lathe and turned down the high points. I then sanded some further to level down the grooves. Slip on the 'O's and fix the caps back on and back for a swim. After twenty minutes more of a leak.
Back to have a look at those rings.
Along with the question of how oversize that flange should be, to which I thank all the contributions, I have also been thinking about the groove to compression relationship with the 'O' rings. Should the groove be wide and shallow to help squash the o ring even further or narrow and deep. Currently the grooves are narrow and a little deep. The O ring just rises like a bump just above the radius of the flange. Pressing against the inside of the polycarb I noticed a couple of potential problems.
We've all done it,
I think there may be a couple of factors that lead to this. 1. Not enough groove for the O ring to sit in? 2. That this O ring is too sloppy. Get a tighter one? Opinions please. I have filed a 45 chamfer along the inner edge of the polycarb to help deflect the O ring down as it slides into the underside of the tube. This does assist.
Theoretically the water can only get in two places with O rings. Above and below. The O ring needs to seat well with both. This next photo shows what I think is the most important thing to get right with O rings.
As you all know, when an O ring presses against the side of the tube you can see a black line where the rubber is pressing against the inside, especially in the right light. This should tell me at least the outside of the O ring is creating a seal. I can't see beneath the O ring to see what is happening in the bottom of the channel, all you can do here is get it smooth and consistent.
By the afternoon I managed to get no leak. I believe this is because I got at least one O ring to press firmly against the inside of the Polycarb. A thin black line barely does the job. A thick black line consistent and all the way around should provide the line of defense we are all after.
I think that the thicker the line the better. I want both rings to press firmly and created a thick black line all the way around.
So my question is. Wide shallow channel or narrow deeper channel? or does it matter as long as the O ring is squashed and there's a thick black line inside the polycarb? Suggestions please?
Something for HWSNBN,
I look at all your photo's where you have 1--20 cylinders sitting on a bench, and I think to myself, wow, he has machined all those caps and they don't leak. I have one of you cylinders and It don't leak.
Do you have a percentage of caps that you test and have to fail as they leak?, or is your routine so good after all these years that you can pretty much make every end cap watertight?
I'm guessing that after making hundreds of these you have in place procedures or steps that guarantee no leaks. I would appreciate your wisdom on this.
David h.
Thank you all for the feedback. I have really appreciated it. I have been making cylinders for almost 20 years. I have tolerated leaks and have taken measures to mitigate as I've made one offs, but when you are thinking about making these things for production, your mind expands and the implications become greater. A Simple thing like O rings and leaks become magnified.
I spent today dealing with 'O' rings. Last night I cut the grooves in the flange of the respective front and back end caps that I will use to prototype all the arrangements. Slipped the rings on and then placed the cylinder in my pool. So far so good, no leaks that I can see. The end caps are a tight fit and then 'O' rings press very firmly into the polycarb.
I then gave both end caps a coat of resin. In this heat, 30 degrees, dry in no time.
So this morning I checked the resin coat on the caps. Nice and dry, 10 am and already 32 degrees, high humidity. The plan today was once again to test the 'O' rings but this time I'm in the pool too.
After cooling off for 40 mins or so and holding the cylinder down half a meter I had a slight drip inside. Should do better than that.
I took the cylinder out and had a look at how the O rings sit in their grooves. The resin dried unevenly in the grooves creating high and low points. This would need to be sanded or turned out. I placed the caps on the lathe and turned down the high points. I then sanded some further to level down the grooves. Slip on the 'O's and fix the caps back on and back for a swim. After twenty minutes more of a leak.
Back to have a look at those rings.
Along with the question of how oversize that flange should be, to which I thank all the contributions, I have also been thinking about the groove to compression relationship with the 'O' rings. Should the groove be wide and shallow to help squash the o ring even further or narrow and deep. Currently the grooves are narrow and a little deep. The O ring just rises like a bump just above the radius of the flange. Pressing against the inside of the polycarb I noticed a couple of potential problems.
We've all done it,
I think there may be a couple of factors that lead to this. 1. Not enough groove for the O ring to sit in? 2. That this O ring is too sloppy. Get a tighter one? Opinions please. I have filed a 45 chamfer along the inner edge of the polycarb to help deflect the O ring down as it slides into the underside of the tube. This does assist.
Theoretically the water can only get in two places with O rings. Above and below. The O ring needs to seat well with both. This next photo shows what I think is the most important thing to get right with O rings.
As you all know, when an O ring presses against the side of the tube you can see a black line where the rubber is pressing against the inside, especially in the right light. This should tell me at least the outside of the O ring is creating a seal. I can't see beneath the O ring to see what is happening in the bottom of the channel, all you can do here is get it smooth and consistent.
By the afternoon I managed to get no leak. I believe this is because I got at least one O ring to press firmly against the inside of the Polycarb. A thin black line barely does the job. A thick black line consistent and all the way around should provide the line of defense we are all after.
I think that the thicker the line the better. I want both rings to press firmly and created a thick black line all the way around.
So my question is. Wide shallow channel or narrow deeper channel? or does it matter as long as the O ring is squashed and there's a thick black line inside the polycarb? Suggestions please?
Something for HWSNBN,
I look at all your photo's where you have 1--20 cylinders sitting on a bench, and I think to myself, wow, he has machined all those caps and they don't leak. I have one of you cylinders and It don't leak.
Do you have a percentage of caps that you test and have to fail as they leak?, or is your routine so good after all these years that you can pretty much make every end cap watertight?
I'm guessing that after making hundreds of these you have in place procedures or steps that guarantee no leaks. I would appreciate your wisdom on this.
David h.
Comment