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I am trying to make a home made manometer, the only thing I don't have is the tubes to screw into the vacuum ports. does anybody know where I could get some?
 

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Hmmm. You're taking a different route than I.
 

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I love Captain Midnights approach. I have done it in a similar yet more clumsy way than he shows. I think that's great.
 

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Hmmm. You're taking a different route than I.
What did you use for fluid?

Also, I don't see a way for air to enter to allow the fluid to move. Does it just pull the fluid up more on the side with more vac? Can you provide more details on this?

I like my 25 year old mercury stix, but at some point I will need to replace it and plan on making my own.


Bill
 

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What did you use for fluid?

Also, I don't see a way for air to enter to allow the fluid to move. Does it just pull the fluid up more on the side with more vac? Can you provide more details on this?

I like my 25 year old mercury stix, but at some point I will need to replace it and plan on making my own.


Bill
Most of the time I use two-stroke pre-mix oil.
Sometimes I'll vary it though, thinning the fluid out. Depends on how accurate I need to be.

Air to enter? There is air in the lines.
Yes, fluid is pulled high on the side with more vacuum. If vacuum is relatively the same, or equalized, between a pair of lines then a even reading will show.
It is possible for a imbalance to be so pronounced that fluid could be pulled into the intake tract. Watching the fluid levels on start-up is mandatory.

I've found no need to restrict the vac pulses. Having adjustable valves to do something with the vacuum on start-up might be a good idea for some or many. When I use the gauge, I usually have the imbalance to a minimum prior to hook-up and am fine-tuning so sucking fluid over the top is rare, but it has happened to me. Holding the line up and letting the fluid drain back down is all that is required to do when it happens. I've never actually sucked fluid out of a line. I'd really have to not be paying attention for that to happen.

I use regular, clear PVC line for the most part.
I use barb'd unions to join 2' sections (thereabout) of ice-maker tubing to the elbows. Those elbows get hot and will soften regular PVC to the point that it will collapse on itself from the vacuum. The thicker ice-maker tubing holds-up to the heat just fine.

Allen-head screws work well for drilling if using for a mano. I've used them with locking nuts and nylon washers with no leaks.

Having fluid levels at 26" works for me. Many will have their fluid at a lower scale. 26" just works for the chair I sit in (easy eye level) while balancing...
 

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Most of the time I use two-stroke pre-mix oil.
Sometimes I'll vary it though, thinning the fluid out. Depends on how accurate I need to be.

Air to enter? There is air in the lines.
Yes, fluid is pulled high on the side with more vacuum. If vacuum is relatively the same, or equalized, between a pair of lines then a even reading will show.
It is possible for a imbalance to be so pronounced that fluid could be pulled into the intake tract. Watching the fluid levels on start-up is mandatory.

I've found no need to restrict the vac pulses. Having adjustable valves to do something with the vacuum on start-up might be a good idea for some or many. When I use the gauge, I usually have the imbalance to a minimum prior to hook-up and am fine-tuning so sucking fluid over the top is rare, but it has happened to me. Holding the line up and letting the fluid drain back down is all that is required to do when it happens. I've never actually sucked fluid out of a line. I'd really have to not be paying attention for that to happen.

I use regular, clear PVC line for the most part.
I use barb'd unions to join 2' sections (thereabout) of ice-maker tubing to the elbows. Those elbows get hot and will soften regular PVC to the point that it will collapse on itself from the vacuum. The thicker ice-maker tubing holds-up to the heat just fine.

Allen-head screws work well for drilling if using for a mano. I've used them with locking nuts and nylon washers with no leaks.

Having fluid levels at 26" works for me. Many will have their fluid at a lower scale. 26" just works for the chair I sit in (easy eye level) while balancing...
I used ATF in mine. Only because it was red and it works fine and it's easy to see. I didn't use a yard stick either, I simply measured off a graduated scale on the base board and marked it with a square prior to adding the tubing. Works like a charm
 

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.....Air to enter? ....
Mine has a chamber that holds the mercury, and it has four tubes running up out of it, and the front of the chamber has a hole with a small chunk of open cell foam in it to allow air to enter (and exit), but won't let out the mercury. Without the hole the mercury would not be able to be pulled up into the tubes.

Being thick and heavy, the mercury does not travel too far up the tubes, but I can imagine with a lighter fluid that there might be an issue.

That said, I wonder how it would be with four tubes, each plugged at the end, all set like a sink drain trap is, with trapped air on the plugged end.


Bill
 

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Mine has a chamber that holds the mercury, and it has four tubes running up out of it, and the front of the chamber has a hole with a small chunk of open cell foam in it to allow air to enter (and exit), but won't let out the mercury. Without the hole the mercury would not be able to be pulled up into the tubes.

Being thick and heavy, the mercury does not travel too far up the tubes, but I can imagine with a lighter fluid that there might be an issue.

That said, I wonder how it would be with four tubes, each plugged at the end, all set like a sink drain trap is, with trapped air on the plugged end.


Bill
Yep. There's all sorts of variations of them.
I've a homemade flowbench that uses the same basic idea. Both are very accurate and consistent, but only unto themselves. Neither the manometer or the flowbench logs are useful to anyone but me. The operation and scale of them are particular to each tool for each part or engine they're on.

That's what I like about homemade tools.
 
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