Adding a reservoir to vacuum system

[Mark Wollschlager]

I have a working vacuum system. Basic diaphragm pump with a variety of hoses valves and filters.
I have seen vacuum system designs that include a reservoir tank.
I suppose the intent is to hold a bit of vacuum in the event of power interruption or to allow for a leakier bit of wood to be held on.
Anyhow some are capped 4"-6" ABS/PVC pipe with tapped fittings. Certainly inexpensive. Strong enough?
I was looking at a Surplus center catalog and saw some steel tanks. A bit more volume so startup would take a bit longer.
Would it matter much either way?
To date I have just used it for finishing the bottoms of some platters out of very sound wood.
Just thinking of venturing further.

 

[john lucas]

I plan to do that on when I set up my system in this new shop. We lose power out here on a regular basis. That happened to me in a basement shop years ago. It was night time. The room went black, the turning flew off and was bouncing around the room like a pin ball machine. I didn't even know where or how to duck. I put 15 foot hose on and it gave me a few more seconds to get the lathe stopped. another problem with losing power is the lathes that have electronic braking like my Powermatic dont work when the power goes off. The work just free wheels for a long time. So this time around I'm going to experiment with putting a small tank in line to give me more time to duck.

 

[Larry Matchett]

A member of my club made one. He used a Harbor Freight air tank. He does a lot of custom laminate work he restores old pianos. He said that it keeps a vacuum for a long time and it saves wear and tear on the pump. His system stays on for 6 to 8 hrs. to let the glue dry. Here is a link to a picture of his system.
http://lighthousewoodturners.org/Newsletter%2012-5-2015.pdf

 

[Bill Boehme]

My thought about vacuum chucking is that it should be treated as if it were a jam chuck with the added feature of being able to remove the tailstock as the final step to remove the nub beneath the live center. In other words, keep the lathe speed low and keep the tailstock in place. I don't believe that you can draw any reasonable analogy between vacuum veneering where you have a sealed bag with almost no leakage and vacuum chucking where many wood species leak like a sieve through the pores in the wood as well as leaking around the seal and through the rotary coupler and the bleed valve. A piston pump can hold a vacuum when it stops, but a diaphragm pump or a rotary vane pump dump vacuum as if the line were opened directly to outside air unless a check valve is inserted in the line. But even without considering the pump, I think that having a tank is only giving a false sense of security. It won't hurt anything, but do your vacuum chucking as if you don't have a reserve tank. On one occasion my vacuum pump suddenly stopped because the thermal overload switch hit the maximum temperature limit. It took me several seconds to gather my wits and stop the lathe. The piece never left the lathe because I had the tailstock in place and was turning at a reasonably slow speed. If I were using a reserve tank and if I didn't have the tailstock holding the piece against the chuck, it would have flown off the lathe.

 

[olaf Vogel]

I have a working vacuum system. Basic diaphragm pump with a variety of hoses valves and filters.
I have seen vacuum system designs that include a reservoir tank.
I suppose the intent is to hold a bit of vacuum in the event of power interruption or to allow for a leakier bit of wood to be held on.
Anyhow some are capped 4"-6" ABS/PVC pipe with tapped fittings. Certainly inexpensive. Strong enough?
I was looking at a Surplus center catalog and saw some steel tanks. A bit more volume so startup would take a bit longer.
Would it matter much either way?
To date I have just used it for finishing the bottoms of some platters out of very sound wood.
Just thinking of venturing further.

The purpose of the reservoir tank is to allow the pump to cycle on, off. Hence not run continuously and burn out early.

In case of power out, I guess the extra time would help shut down the lathe.
A compressor tank would work better than ABS and should be cheap. 5 gallon for $50.
That would give minutes....depending on leakage.

 

[John K Jordan]

look at Joe Woodworker

I have seen vacuum system designs that include a reservoir tank.
I suppose the intent is to hold a bit of vacuum in the event of power interruption or to allow for a leakier bit of wood to be held on.
Anyhow some are capped 4"-6" ABS/PVC pipe with tapped fittings. Certainly inexpensive. Strong enough?

Vacuum is so much easier to "contain" than pressure. Nearly any kind of tank will work. I believe the PVC tubes will be plenty strong.

After a lot of research, I liked Joe Woodworker's design the best:
http://www.joewoodworker.com/veneering/EVS/concept.htm

Point "4" in this link describes the reservoir.
Many of these are in operation (look at his gallery)
http://www.joewoodworker.com/veneering/visitorspress.htm
http://www.joewoodworker.com/veneering/visitorspress2.htm
One guy used fire extinguishers for his reservoirs.

Note that this design includes a check valve.

Also, note how the design includes a MAC valve and what it does.

I accumulated all the components to build one which will happen "any day now."

JKJ

 

[Josh Stevens]

You can also buy a non return valve for vacuum systems that will hold your piece on the lathe for quite a few seconds after switching the pump off. The air still leaks out eventually but it's worthwhile for piece of mind.

 

[John K Jordan]

I put 15 foot hose on and it gave me a few more seconds to get the lathe stopped...

So you added a reservoir!

When building a horse shelter about 500 ft from the nearest power I found that running most of the length with an air hose nearly doubled the capacity of my small pancake compressor we used for the framing nail guns. As a bonus in this case, it also eliminated the need for and the power loss problems with running an electric motor with long extension cords.

One possible interesting tidbit about vacuum reservoirs. I learned a lot about player pianos when I rebuilt mine. (that old technology is astounding) In the bottom of the piano is a big vacuum reservoir to smooth out the surges from the foot pumps. This is a huge spring-loaded wood and cloth bellows that is compressed against the springs to "store" vacuum. This makes me wonder if there would be any operational or space advantage to a using a dynamic, spring-loaded reservoir on a vacuum chuck system instead of a simple tank. The tank sure would be a lot simpler.

JKJ

 

[James Seyfried]

Note that this design includes a check valve.

Also, note how the design includes a MAC valve and what it does.

I accumulated all the components to build one which will happen "any day now."

JKJ

Other than a time lag in the event of power loss, what are the expected advantages in a woodturning application. I am wondering if conditions are just right that the compressor would turn off and hold vacuum while turning, resulting in less wear on the compressor. Or what advantages are you expecting to get?

 

[hockenbery]

It seems there is some uncertainty in this thread about the purpose of an extra tank.

My vacuum system is controlled by a blead valve. I believe this is the most common control mechanism.
This is an inline leak which when closed has no leak and maximum vacuum.
When the leak is opened it decreases the vacuum from maximum of the system to 0 when fully opened.
At any give operating vacuum less that max the controlling bleed valve will allow the vacuum to fill with air when the pump stops because of loss off power.
An auxiliary tank in line increases the volume to be filled by air going through the bleed valve giving some time to stop the lathe and catch the piece before it flies off.

Al

 

[John K Jordan]

Other than a time lag in the event of power loss, what are the expected advantages in a woodturning application. I am wondering if conditions are just right that the compressor would turn off and hold vacuum while turning, resulting in less wear on the compressor. Or what advantages are you expecting to get?

From the link I gave:

4. Vacuum Reservoirs/Sub-Reservoir: The main reservoirs in the system hold spare vacuum just like a rechargeable battery. These reservoirs prevent the system from constantly cycling on and off by providing additional vacuum buffer. The sub-reservoir is a small holding tank of free air that allows the pump to achieve full RPM when starting up without back-pressure against the pump intake port.

JKJ

 

[James Seyfried]

From the link I gave:

4. Vacuum Reservoirs/Sub-Reservoir: The main reservoirs in the system hold spare vacuum just like a rechargeable battery. These reservoirs prevent the system from constantly cycling on and off by providing additional vacuum buffer. The sub-reservoir is a small holding tank of free air that allows the pump to achieve full RPM when starting up without back-pressure against the pump intake port.

JKJ

I did read the link, I also read:

...I don't believe that you can draw any reasonable analogy between vacuum veneering where you have a sealed bag with almost no leakage and vacuum chucking where many wood species leak like a sieve through the pores in the wood as well as leaking around the seal and through the rotary coupler and the bleed valve...

So even with the losses Bill mentions, do you think this system will allow the vacuum pump to cycle off while turning.

 

[Bill Boehme]

.... In the bottom of the piano is a big vacuum reservoir to smooth out the surges from the foot pumps. This is a huge spring-loaded wood and cloth bellows that is compressed against the springs to "store" vacuum. This makes me wonder if there would be any operational or space advantage to a using a dynamic, spring-loaded reservoir on a vacuum chuck system instead of a simple tank. The tank sure would be a lot simpler.

Your description seems confusing to me. I've never had the opportunity to look at the workings of a player piano, but I did get to look at an organ in an old abandoned country church ... Before vandals stole it along with the pulpit, pews and stained glass windows. I was under the impression that the bellows pump created a positive pressure.

The part about "bellows compressed against the springs" is where you lost me. Springs compressing a vacuum? If it is really a vacuum then the springs and bellows should be pulling apart.

EDIT: After mulling it over in my head, I think that I figured out how the vacuum was pulling the bellows down to compress the spring. I also see a practical reason for using a vacuum as opposed to a positive pressure ... there is an absolute limit to how much vacuum can be created.

Other than a time lag in the event of power loss, what are the expected advantages in a woodturning application. I am wondering if conditions are just right that the compressor would turn off and hold vacuum while turning, resulting in less wear on the compressor. Or what advantages are you expecting to get?

Are you talking about a Venturi system since you mentioned using a compressor? Vacuum pumps do not cycle on and off ... they run until you shut them off. Whether you are using a vacuum pump with bleed or a Venturi operated by compressed air, the pump has to do a certain amount of work (energy) to maintain a certain vacuum level while at the same time offsetting the leakage. You can't fool Mother Nature by cycling on and off. The total energy requirement is unchanged so the pump would just have to work harder when it is on.

Somebody asked earlier about any possible benefit of a spring loaded pressure tank. That's essentially what the pressure tank does for those of you familiar with water wells in rural areas. The benefit would be constant pressure output followed by an almost instantaneous drop to zero.

Like I said previously I think that the storage tank idea is a solution looking for a problem .... not that there's anything wrong with that.

 

[hockenbery]

I did read the link, I also read: So even with the losses Bill mentions, do you think this system will allow the vacuum pump to cycle off while turning.

I have not seen a vacuum pump attached to a chuck that holds pieces on a lathe that cycles off.
They run continuously and are controlled with a bleeder valve that lets air into the pump.

Mostly vacuum is used for finishing the bottom of a bowl Which is a five minute run for the pump.
I use the vacuum to hold spheres for hollowing and that may take 15-30 minutes for larger spheres.

I hold most of my bowls at about 10-15" vacuum by letting air into the system.
Some pieces will crack at much over 5"

Solid balls I hold at max vacuum with the bleeder valve closed - about 25-27" on my system.

Al

 

[John K Jordan]

Player piano vacuum mechanisms, and rebuilding

The part about "bellows compressed against the springs" is where you lost me. Springs compressing a vacuum? If it is really a vacuum then the springs and bellows should be pulling apart.

Yes, the sides of the bellows are pushed apart, could be worded better. The springs are internal so the sides of the bellows are pushed against the springs, compressing them. I hope this is not too off-topic. (A lathe would have in fact been handy for the rebuild.)

The large bellows is made from two rigid boards, one fixed to the piano and one attached with hinges that moves freely. Flexible bellows cloth is glued around the two boards to make a sealed chamber. A hose from the foot operated pump bellows reduces the pressure in the reservoir bellows. A second hose leads from the reservoir up to the piano movement.

There are strong leaf-type springs inside the reservoir bellows, arranged to hold the bellows open when at rest. Reduced pressure in the input tube acts to reduce the pressure in the reservoir bellows, "sucks" the two boards together, and compresses the springs. Continuous pumping tends to hold the reservoir bellows about half-way closed. If the operator slows pumping for a moment, the force of the springs works to spread the two halves of the bellows apart as needed to keep the air pressure (vacuum supply) constant as controlled by a regulator.


Below is more player piano mechanism info, in case you are interested or if anyone else wants to take on a fascinating wood-related project...

The engineering of the player piano is incredible, especially considering it was developed in the late 1800s. (we think we are clever) There is a vacuum motor made of 5 bellows, valves, and crank, a regulator bellows to keep the speed constant as set by a user-operated lever, and 66 fast-acting striker bellows, one for each note, each controlled by a double-action valve made from leather and wood. The striker bellows activate the mechanism that strikes the string with the hammer.

The paper drawn through the mechanism has a hole for each note to be played. When the hole passes it's designated orifice the air pressure in a tube leading to the corresponding note is momentarily increased, triggering the sensitive side of the double-action valve which then sucks air from the striker bellows and activates the hammer. This entire mechanism is so fast the note can be triggered repeatedly several multiple times a second.

But most amazing thing to me is the system that keeps the paper roll perfectly aligned with the row of holes so the right note will be played. This mechanism uses paper-edge sensors to move the entire paper carriage left and right in real time as needed, even compensating for expansion and contraction of the paper due to humidity! It uses a two staggered air pressure sensor orifices on each side along with a set of valves that trigger an adjustment bellows which provides the force to move the paper roll carriage horizontally exactly the amount needed. A lever allows the operator to shift the carriage incrementally to play a song in a different key.

This is a reliable working hybrid digital/analog pneumatic playback system with inexpensive mass-produced digitally recorded data storage media designed and engineered in the 1800s! Amazing! The piano I had was built in the 1930s.

The bellows on mine were so leaky that it took Superman to pump fast enough to make it play. I rebuilt all the bellows (thank the original builders for using hide glue), replaced all the lead tubing with rubber, made necessary repairs and adjustments, lubricated (with graphite powder), replaced all the felts and piano hammers, and restrung the bass strings. I was fortunate to find a player piano restorer kind enough to spend an entire afternoon in his shop explaining many things and providing experienced advice. He told me things such as how to get each of the 66 striker bellows off the wooden vacuum manifold, how to adjust the valves, tune up the motor, etc. He also strongly suggested put everything back together with hide glue again to be kind to the next guy who might rebuild it 40 years from then. 🙂

It took me about a month to rebuild the piano, working at least 4-6 hours every day and weekends. When I was finished, it was so tight I could literally play a roll by working one foot pedal with my thumb!

Ok, there you have it. BTW, I did this rebuild in the 70s. I may have forgotten a detail somewhere.

JKJ

 

[Bill Boehme]

That is fascinating, John. I wonder how many people in the entire world know how to repair these old mechanical marvels.Its a sad thing that some of these mechanical design techniques will soon be completely gone.

I have a small collection of old tools. One of my favorites is a die that is able to start a thread in the middle of a steel bar. I don't know of a practical use for something like that unless you know of a nut that could somehow be slipped over the unthreaded part.

 

[stu senator]

That is fascinating, John. I wonder how many people in the entire world know how to repair these old mechanical marvels.Its a sad thing that some of these mechanical design techniques will soon be completely gone.

I have a small collection of old tools. One of my favorites is a die that is able to start a thread in the middle of a steel bar. I don't know of a practical use for something like that unless you know of a nut that could somehow be slipped over the unthreaded part.

A split nut used for adjustment and locking.

Stu

 

[John K Jordan]

That is fascinating, John. I wonder how many people in the entire world know how to repair these old mechanical marvels.Its a sad thing that some of these mechanical design techniques will soon be completely gone.

I have a small collection of old tools. One of my favorites is a die that is able to start a thread in the middle of a steel bar. I don't know of a practical use for something like that unless you know of a nut that could somehow be slipped over the unthreaded part.

There are split nuts on metal-cutting lathes, used to engage/disengage a rotating threaded shaft to move the carriage when cutting threads.

Back in the '70s I found that one person in our region who rebuilt players, about 3 hours drive from me. He said at the time it was a already a lost art. He had a large room full of perhaps 20 or more pianos waiting to be rebuilt. He said the waiting period was about two years! There was a big interest in restoring these at the time. These days electronic players and player attachments are available to do the same thing far, far cheaper, but there is nothing like the "real" thing! We used to take the front off the piano and watch all mechanisms go.

A google search showed a few people still doing this. Looking at a web site it seemed to me they concentrated on high-end pianos, often grands, which often had "reproducing" movements, capable of subtle dynamics and expression instead of just hitting the note like my "cheap" piano. 🙂

JKJ

 

[James Seyfried]

Are you talking about a Venturi system since you mentioned using a compressor? Vacuum pumps do not cycle on and off ... they run until you shut them off…

Actually I misspoke (miss typed?) I meant to say vacuum pump. I must be missing something because this system seems to claim the vacuum pump will cycle on and off. At the bottom of Joe Woodworker's design page is this link: click here to read more about why these parts are needed for this system that explains this:

“The Vacuum Controller
Without this piece, the system would run continuously. This is fine if you don't mind the 74 decibels of sound being continuously emitted from the pump or if you are not bothered by the waste of electricity from a pump that has to run for the entire duration of the pressing. The vacuum controller monitors the vacuum level and cycles the system on and off as needed.”

This leads me to believe with that system the vacuum pump would cycle, unless I missing something in that description. I also realize that the check valve and other components come into play. I am just curious if it will still work that way when used for woodturning as opposed to vacuum veneering given the differences you mentioned. 😕

 

[John K Jordan]

So even with the losses Bill mentions, do you think this system will allow the vacuum pump to cycle off while turning.

If you are talking about the Joe Woodworker system, yes, from what I read the pump will cycle off as long as the leakage is not too severe and the reservoir is big enough and the system contains a pressure switch or vacuum controller and the capacity of the pump is large enough! The way I understand it the vacuum controller is a glorified pressure switch which also controls the MAC valve. I like the idea of the MAC valve and sub reservoir since it can reduce startup load on the pump, analogous to the way my big air compressor vents the pressure to reduce startup loading.

I didn't mention that I intend to use my pump for vacuum clamping and possibly some veneer work, both of which can make good use of the pump with the reservoir, as would wood infusion and stabilization. If just for chucking only, a continuous run pump might be sufficient. The pumps I've seen that were used ONLY for vacuum chucking didn't have the reservoir and controller and all - they just ran all the time the piece was turning.

Did you see Joe Woodworking's page about vacuum chucking? He talks about the pump capacity, continuous run, porosity of the wood, etc:
http://www.joewoodworker.com/veneering/vacuumchucking.htm
The biggest point I got from reading it was it was difficult to predict how a specific piece will act with a specific pump.

If the seal at the vacuum chuck is not good or the piece is really porous or the pump has a low capacity the pump might run all the time and you might WANT it to run all the time. Vacuum pumps are rated for vacuum level they can achieve plus the flow capacity. For vacuum chucking I looked for a higher capacity, a higher CFM rating. I think the pump I bought is 5+ CFM. Note that all these chucking systems include a bleed valve and maybe even a vacuum gauge at the lathe to allow adjusting the vacuum. A lower capacity pump could need the bleed valve closed a little more. A continuous run pump with high flow rate and large, well sealed bowl might need the bleed valve opened pretty wide!

You can also call Joe and discuss this - he was a real help the time I called to figure out what kind of vacuum system would do what I wanted.

JKJ

 

[Bill Boehme]

Actually I misspoke (miss typed?) I meant to say vacuum pump. I must be missing something because this system seems to claim the vacuum pump will cycle on and off. At the bottom of Joe Woodworker's design page is this link: click here to read more about why these parts are needed for this system that explains this:

“The Vacuum Controller
Without this piece, the system would run continuously. This is fine if you don't mind the 74 decibels of sound being continuously emitted from the pump or if you are not bothered by the waste of electricity from a pump that has to run for the entire duration of the pressing. The vacuum controller monitors the vacuum level and cycles the system on and off as needed.â€

This leads me to believe with that system the vacuum pump would cycle, unless I missing something in that description. I also realize that the check valve and other components come into play. I am just curious if it will still work that way when used for woodturning as opposed to vacuum veneering given the differences you mentioned. 😕

My Gast vacuum pump is very quiet (I can't even hear it over my 3M Airstream respirator) and as Al mentioned, it normally is needed for just a few minutes while the tenon is removed from the bottom of a turning. The thing that you may have overlooked is that vacuum veneering/pressing is a completely different sort of thing than vacuum chucking. When you have a sealed bag, all that you need to do is remove the air and if there aren't any leaks then the flow requirement is essentially zero. Once the residual air in the wood has been evacuated valve could be closed and the pump removed and ideally, the vacuum will hold. There are always some microscopic leaks and some outgassing in the wood as any residual moisture vaporizes. This means that occasionally the vacuum pump would need to be turned on or if you have a large reservoir it helps in minimizing vacuum loss. Vacuum chucking is a completely different situation. There are more leaks than you can shake a stick at: bleed valve is the only intentional leak, but it is a biggie. Unintentional leaks include the rotary coupler, leak between chuck and spindle, leak around chuck gasket, and leak through the wood. Sometimes leakage through the wood is surprisingly huge. Sometimes I have found it necessary to put tape over as much of the wood as I possibly can to be able to get a decent vacuum level. Vacuum pumps like the Gast are industrial tools designed for continuous duty. Not only would cycling them on and off not have any sort of benefit, it is likely to be bad for the pump ... at least, it would be bad for my particular rotary vane pump. The reason is that the pump head gets very hot and while it is running, the motor fan and air flow through the pump provides some cooling. Gast specifies a shut down procedure in the instruction manual that says to run the pump for a specified number of minutes with a completely open inlet port then a specified number of minutes with the inlet port closed and finally for a specified number of minutes with the inlet port open again. The cycle times varies with pump model. I think that some of the newer models have a simplified shut down procedure. There is also no benefit in cycling from an energy saving perspective. It actually would require more energy to have the pump cycle on and off. The reason is that motors that have a high starting torque which would be the situation of starting with a hard vacuum, require an initial inrush current that may exceed six times the normal full load current. And, that large starting current means a lot more heat that has to be dissipated. So cycling on and off equals more electric energy used and more heat build up in the motor.

 

[James Seyfried]

If you are talking about the Joe Woodworker system, yes, from what I read the pump will cycle off as long as the leakage is not too severe and the reservoir is big enough and the system contains a pressure switch or vacuum controller and the capacity of the pump is large enough! The way I understand it the vacuum controller is a glorified pressure switch which also controls the MAC valve. I like the idea of the MAC valve and sub reservoir since it can reduce startup load on the pump, analogous to the way my big air compressor vents the pressure to reduce startup loading.

I didn't mention that I intend to use my pump for vacuum clamping and possibly some veneer work, both of which can make good use of the pump with the reservoir, as would wood infusion and stabilization. If just for chucking only, a continuous run pump might be sufficient. The pumps I've seen that were used ONLY for vacuum chucking didn't have the reservoir and controller and all - they just ran all the time the piece was turning.

Did you see Joe Woodworking's page about vacuum chucking? He talks about the pump capacity, continuous run, porosity of the wood, etc:
http://www.joewoodworker.com/veneering/vacuumchucking.htm
The biggest point I got from reading it was it was difficult to predict how a specific piece will act with a specific pump.

If the seal at the vacuum chuck is not good or the piece is really porous or the pump has a low capacity the pump might run all the time and you might WANT it to run all the time. Vacuum pumps are rated for vacuum level they can achieve plus the flow capacity. For vacuum chucking I looked for a higher capacity, a higher CFM rating. I think the pump I bought is 5+ CFM. Note that all these chucking systems include a bleed valve and maybe even a vacuum gauge at the lathe to allow adjusting the vacuum. A lower capacity pump could need the bleed valve closed a little more. A continuous run pump with high flow rate and large, well sealed bowl might need the bleed valve opened pretty wide!

You can also call Joe and discuss this - he was a real help the time I called to figure out what kind of vacuum system would do what I wanted.

JKJ

Thank you for posting all the information on this John. I saved the links for future reference. I have the system that JT Turning Tools sells and it has worked well for me, but I like to learn about things. I like the idea of the auto-cycling system and have a better understanding of it, but it looks like it requires a jumper switch to make it continuous-running for vacuum turning. Towards the bottom of Joe’s vacuum chucking page it says:

“Auto-Cycling Electric Pump Vacuum Presses

The continuous on and off cycles that will be caused by this add-on are not good for the electronic components on the vacuum pump. Additionally, the pump may not cycle often enough to maintain a minimum of 15" of vacuum inside the vacuum chuck. The good news is that there is a very easy fix for this. You can simply wire in a jumper switch to convert the system to a continuous-run system. This switch will bypass the vacuum controller and allow the pump to run non-stop. Click here for instructions to add this switch to your system.â€

I still might make the Joe Woodworker system and include the bypass switch, because I would like to try some veneer vacuuming too. I also like the way Joe Woodworker has the bleeder valve and vacuum gage attached. I am going to see if I can convert mine to something similar.

...as Al mentioned, it normally is needed for just a few minutes while the tenon is removed from the bottom of a turning...

Yes, and normally I should be able to start sanding with 220 grit too. 😱