Programmable Vacuum Switch?

[vtgaryw]

I just set up my vacuum chamber (pressure cooker pot with a diaphragm pump.) It holds vacuum well, so well, in fact, that I'd like to not have to run the pump continuously.

Anyone know of a reasonably priced programmable vacuum switch so I can turn the pump on and off as needed?

Thanks,

Gary

 

[vtgaryw]

Sorry, meant to post this in the casting and stabilization sub-forum, not sure if I can move it?

 

[BSea]

why don't you just put in a valve that you can shut. Once you get the vacuum you want, close the valve, and shut off the vacuum pump. If it holds really well, you may not have to do anything. If not, you can check it and run the pump as needed. Maybe not what you're looking for, but a lot cheaper.

 

[frank123]

Fairly easily made.

Use a scavenged carburetor diaphragm type vacuum control from a junkyard, a spring attached to the pull rod from it that is tension adjusted by a screw or bolt and a salvaged microswitch to flip the pump on and off (or trigger a relay controlling the pump [power if your switch is low amperage which it probably is).

A vacuum gage is obviously needed to tell the vacuum you're pulling and adjust it where you want it, and you just "T" the gadget into the line to your vacuum chamber.

Cost 5 bucks or so maybe if you don't have a junk box full of all those things you could never figure out why you needed but couldn't bring yourself to throw away that already has the parts in it.

Or you could spend a hundred bucks or so and buy one that will work just as well. I've seen some pretty fancy ones in electronic and mechanical construction designs that will control it down to an almost immeasurably small accuracy.

 

[vtgaryw]

Hmmm.... a couple of simple, foolproof, mechanical ways to accomplish something I can throw money and technology at? Nah...

Actually, I can see the carb diaphragm working well.

My pump actually holds pressure when you shut it off, so I wouldn't even need a shut off valve if I just turned it off and checked on it every hour or so...

I guess I have enough projects for now anyways.

Thanks

Gary

 

[Tim'sTurnings]

My tanks keeps the vacuum pretty good too. But I leave my vac pump running as Curtis suggests.
Tim.

 

[Jim Burr]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

 

[JohnGreco]

You want to keep it running so it can continue to draw air out of the wood....that isn't something that happens in a few minutes. If you have a cut-off valve you can test this by vacuuming how much you -think- it needs, then turn the valve until there are no more bubbles. Then open it back up. I'm willing to bet you'll see more bubbles as it draws more air from deeper within the wood.

 

[BSea]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

Just because it doesn't say it will work, doesn't mean it won't. I know most pressure pots don't say anything about making them a vacuum chamber. But people here do it all the time. In fact there's an article in the library about doing that. Since he's been using it as one, I'd say it works. What's the worst that could happen?

 

[MesquiteMan]

If you are going to be stabilizing and want the best results, you do NOT want to hold vacuum. You need the pump running so that it continues to evacuate air from the chamber and the wood. Think of it this way...put a straw in a coke and suck on it. As long as you continue to suck on it, the coke continues to flow into your mouth. If you suck the coke up the straw to the top just before it get to your mouth and hold it, the coke stops flowing. The same thing happens int he wood.

My chambers will hold vacuum as well. I have one that has a valve on it so I can hold vac. This is for testing purposes only. I can pull that chamber down full of wood and close the valve making it hold vac. It quickly stops bubbling. As soon as I open the valve back up, it starts bubbling all over again.

If you are worried about the pump...don't be. Most are made for continuous operation. Not sure on diaphragm pumps but I know good rotary vane oil filled pumps are made to run as long as you want. Be aware that a diaphragm pump is most likely NOT going to produce as deep of a vacuum as a rotary vane pump. The deeper the vacuum, the more air you get out of the wood and thus, the more resin you get back into the wood.

 

[Jim Burr]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

Just because it doesn't say it will work, doesn't mean it won't. I know most pressure pots don't say anything about making them a vacuum chamber. But people here do it all the time. In fact there's an article in the library about doing that. Since he's been using it as one, I'd say it works. What's the worst that could happen?

Uhhhh...it could explode under inappropriate use. I'm just a fan of using tools as they were intended...part of being a licensed medical professional.

 

[sbell111]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

Just because it doesn't say it will work, doesn't mean it won't. I know most pressure pots don't say anything about making them a vacuum chamber. But people here do it all the time. In fact there's an article in the library about doing that. Since he's been using it as one, I'd say it works. What's the worst that could happen?

Uhhhh...it could explode under inappropriate use.

Implode. The absence of pressure cannot make a thing explode. As such, it is somewhat unlikely that significant damage/injury would be likely to occur.

I'm just a fan of using tools as they were intended...part of being a licensed medical professional.

I'm also generally a fan of using things as intended, but I recognize that we are an inventive lot and frequently discover new uses for items. In the pen making world, we see that very often. A few examples are how we use paint pots as pressure and vacuum vessels or how we utilize resins and glues in ways that were not initially imagined to create and finish our pen bodies.

 

[Jim Burr]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

Just because it doesn't say it will work, doesn't mean it won't. I know most pressure pots don't say anything about making them a vacuum chamber. But people here do it all the time. In fact there's an article in the library about doing that. Since he's been using it as one, I'd say it works. What's the worst that could happen?

Uhhhh...it could explode under inappropriate use.

Implode. The absence of pressure cannot make a thing explode. As such, it is somewhat unlikely that significant damage/injury would be likely to occur.

I'm just a fan of using tools as they were intended...part of being a licensed medical professional.

I'm also generally a fan of using things as intended, but I recognize that we are an inventive lot and frequently discover new uses for items. In the pen making world, we see that very often. A few examples are how we use paint pots as pressure and vacuum vessels or how we utilize resins and glues in ways that were not initially imagined to create and finish our pen bodies.

Amazing!! When was the last time you saw someone killed by super glue. I understand your intent, but again...you failed.

 

[sbell111]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

Just because it doesn't say it will work, doesn't mean it won't. I know most pressure pots don't say anything about making them a vacuum chamber. But people here do it all the time. In fact there's an article in the library about doing that. Since he's been using it as one, I'd say it works. What's the worst that could happen?

Uhhhh...it could explode under inappropriate use.

Implode. The absence of pressure cannot make a thing explode. As such, it is somewhat unlikely that significant damage/injury would be likely to occur.

I'm just a fan of using tools as they were intended...part of being a licensed medical professional.

I'm also generally a fan of using things as intended, but I recognize that we are an inventive lot and frequently discover new uses for items. In the pen making world, we see that very often. A few examples are how we use paint pots as pressure and vacuum vessels or how we utilize resins and glues in ways that were not initially imagined to create and finish our pen bodies.

Amazing!! When was the last time you saw someone killed by super glue. I understand your intent, but again...you failed.

That smell of failure is coming from your pits, not me.

I never said anything about super glue killing anyone. Perhaps you were reading someone else's post in some fantasy reality.

While we are on the subject of life experiences, however, when was the last time that you heard of a pressure cooker, under vacuum, exploding?

 

[Ice31]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

Just because it doesn't say it will work, doesn't mean it won't. I know most pressure pots don't say anything about making them a vacuum chamber. But people here do it all the time. In fact there's an article in the library about doing that. Since he's been using it as one, I'd say it works. What's the worst that could happen?

Uhhhh...it could explode under inappropriate use.

Implode. The absence of pressure cannot make a thing explode. As such, it is somewhat unlikely that significant damage/injury would be likely to occur.

I'm just a fan of using tools as they were intended...part of being a licensed medical professional.

I'm also generally a fan of using things as intended, but I recognize that we are an inventive lot and frequently discover new uses for items. In the pen making world, we see that very often. A few examples are how we use paint pots as pressure and vacuum vessels or how we utilize resins and glues in ways that were not initially imagined to create and finish our pen bodies.

Amazing!! When was the last time you saw someone killed by super glue. I understand your intent, but again...you failed.

People....since we are all reasonable and can think for ourselves lets remember that it's his choice to use the pot how he sees fit. No need to get into a tuff about it. On the other hand I doubt that either of you are engineers so you haven't ran the calculations to see if the pot can handle the external pressure that is being put on it by the vacuum. Well neither am I, but I do work for a company that works on pressure vessels on a regular basis so I looked up the specs on pressure cooker pot and plugged it all into our program just to see what it would tell me....verdict...."adequate reinforcement"....meaning that the standard 5qt pressure cooker that I looked up will handle a full vacuum without failure. Even though it is not "rated" that way it looks as though it will handle it without imploding. So Jim, rest assured, it is possible that this process of repurposing this tool is completely safe.

 

[BSea]

Pressure cookers are just that...for cooking artichokes, taters...so on. Why on earth would you thing it would be suitable for vacuum or pressure casting...did the label say it would work?????

Just because it doesn't say it will work, doesn't mean it won't. I know most pressure pots don't say anything about making them a vacuum chamber. But people here do it all the time. In fact there's an article in the library about doing that. Since he's been using it as one, I'd say it works. What's the worst that could happen?

Uhhhh...it could explode under inappropriate use. I'm just a fan of using tools as they were intended...part of being a licensed medical professional.

Since we are talking about a vacuum chamber, exploding really isn't a hazard. Even imploding violently is unlikely since most pressure cookers are steel. At worst it would collapse the sides of the container or crack whatever top they were using. I have read a few example of vacuum chambers sold on the internet that have collapsed under vacuum. And they were actually sold as vacuum chambers.

 

[ChrisN]

If you are going to be stabilizing and want the best results, you do NOT want to hold vacuum. You need the pump running so that it continues to evacuate air from the chamber and the wood. Think of it this way...put a straw in a coke and suck on it. As long as you continue to suck on it, the coke continues to flow into your mouth. If you suck the coke up the straw to the top just before it get to your mouth and hold it, the coke stops flowing. The same thing happens int he wood.

...

The deeper the vacuum, the more air you get out of the wood and thus, the more resin you get back into the wood.

But after all the air has left the wood, the vacuum won't get any better. If you have a switch set for a certain level of vacuum, the pump will run until it hits that level, and then will turn off. If more air seeps out of the wood, the vacuum level will drop, the pump will turn on and evacuate it, the vacuum will rise, and the pump will turn off. This would be great for putting a bunch of blanks into a chamber overnight - rather than letting the pump run all night, it could turn off when full vacuum is reached, and maintain that level throughout the night without running continuously.

 

[MesquiteMan]

You will also ruin a rotary vane, oil filled pump if you do this and also risk contaminating your resin with vacuum pump oil!

A rotary vane oil filled pump is made to be started and stopped with no load at all. Starting it against a vacuum will cause premature failure of the flexible coupler that connect the motor to the actual pump mechanism. If it is shut down under load, it will cause it to spit oil on the next start up. Then, depending on your pump, if you do not have a check valve, the vacuum in the chamber will suck the oil out of the pump and your resin will become contaminated. I know this for a fact as I have seen it myself and even replaced some resins for a customer who had this happen.

Oil filled rotary vane pumps are made to run as long as you need them to. I have never worried about running mine non stop until the bubbles stop coming from the wood, even if that is 8-10 hours.

You are correct that after all the air has left the wood, the vacuum will not get any better. However, by that time, there is not need to keep pulling vacuum and it is time to release and come back to atmosphere!

All I know is I can put blanks in a chamber and pull vacuum for an hour and still have bubbles coming out of the wood. If I close a valve and isolate the chamber so that vac is no longer being pulled, the bubbling will stop almost immediately and the vac level on the gauge will remain the same at full vac according to the gauge. As soon as I open the valve and start pulling again, they blanks will start bubbling again.

If you are going to be stabilizing and want the best results, you do NOT want to hold vacuum. You need the pump running so that it continues to evacuate air from the chamber and the wood. Think of it this way...put a straw in a coke and suck on it. As long as you continue to suck on it, the coke continues to flow into your mouth. If you suck the coke up the straw to the top just before it get to your mouth and hold it, the coke stops flowing. The same thing happens int he wood.

...

The deeper the vacuum, the more air you get out of the wood and thus, the more resin you get back into the wood.

But after all the air has left the wood, the vacuum won't get any better. If you have a switch set for a certain level of vacuum, the pump will run until it hits that level, and then will turn off. If more air seeps out of the wood, the vacuum level will drop, the pump will turn on and evacuate it, the vacuum will rise, and the pump will turn off. This would be great for putting a bunch of blanks into a chamber overnight - rather than letting the pump run all night, it could turn off when full vacuum is reached, and maintain that level throughout the night without running continuously.

 

[vtgaryw]

That makes sense, I'll defer to Curtis's expertise on that.

I use an RV diaphragm pump that I use for my small sugaring operation. Like I said, I ran it almost 3 weeks straight this spring with no problems, they will run continuously (and dry!) for ages.

As far as using a pressure cooker, it's not an issue, I'm not using it as a pressure pot. The cooker is plenty strong enough for the external psi on the pot at 20-30 inches of vacuum.

Thanks,

Gary

You will also ruin a rotary vane, oil filled pump if you do this and also risk contaminating your resin with vacuum pump oil!

A rotary vane oil filled pump is made to be started and stopped with no load at all. Starting it against a vacuum will cause premature failure of the flexible coupler that connect the motor to the actual pump mechanism. If it is shut down under load, it will cause it to spit oil on the next start up. Then, depending on your pump, if you do not have a check valve, the vacuum in the chamber will suck the oil out of the pump and your resin will become contaminated. I know this for a fact as I have seen it myself and even replaced some resins for a customer who had this happen.

Oil filled rotary vane pumps are made to run as long as you need them to. I have never worried about running mine non stop until the bubbles stop coming from the wood, even if that is 8-10 hours.

You are correct that after all the air has left the wood, the vacuum will not get any better. However, by that time, there is not need to keep pulling vacuum and it is time to release and come back to atmosphere!

All I know is I can put blanks in a chamber and pull vacuum for an hour and still have bubbles coming out of the wood. If I close a valve and isolate the chamber so that vac is no longer being pulled, the bubbling will stop almost immediately and the vac level on the gauge will remain the same at full vac according to the gauge. As soon as I open the valve and start pulling again, they blanks will start bubbling again.

If you are going to be stabilizing and want the best results, you do NOT want to hold vacuum. You need the pump running so that it continues to evacuate air from the chamber and the wood. Think of it this way...put a straw in a coke and suck on it. As long as you continue to suck on it, the coke continues to flow into your mouth. If you suck the coke up the straw to the top just before it get to your mouth and hold it, the coke stops flowing. The same thing happens int he wood.

...

The deeper the vacuum, the more air you get out of the wood and thus, the more resin you get back into the wood.

But after all the air has left the wood, the vacuum won't get any better. If you have a switch set for a certain level of vacuum, the pump will run until it hits that level, and then will turn off. If more air seeps out of the wood, the vacuum level will drop, the pump will turn on and evacuate it, the vacuum will rise, and the pump will turn off. This would be great for putting a bunch of blanks into a chamber overnight - rather than letting the pump run all night, it could turn off when full vacuum is reached, and maintain that level throughout the night without running continuously.