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airsail said..
My cheap eBay vac pump got very hot running full time, had a fan on it to try and keep it cool. It started spewing oil then eventually died, probably didn't like no airflow through it.

Did you keep it topped up with oil? They have a sight-glass on them to check the level.

I added a length of PVC hose on the end of mine, after the oil separator as I think it still sends out a bit of oil. I topped it up with 'compressor oil' from Bunnings as I figured it does the same job.

From what I recall of an aircon install done a few years ago, they run these things for quite a while to 'vacuum down' the refrigerant lines before they add gas, so you would think it would handle being on all the time... but I guess maybe not for a really long time.

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FormulaNova said..

airsail said..
My cheap eBay vac pump got very hot running full time, had a fan on it to try and keep it cool. It started spewing oil then eventually died, probably didn't like no airflow through it.

Did you keep it topped up with oil? They have a sight-glass on them to check the level.

I added a length of PVC hose on the end of mine, after the oil separator as I think it still sends out a bit of oil. I topped it up with 'compressor oil' from Bunnings as I figured it does the same job.

From what I recall of an aircon install done a few years ago, they run these things for quite a while to 'vacuum down' the refrigerant lines before they add gas, so you would think it would handle being on all the time... but I guess maybe not for a really long time.

Yes, I had a vertical tube attached to the breather as it was spitting hot oil out. Had to keep it running as it was on a job, luckily the resin had time to gel before it failed.
Going to have a look at one of these, 72 dB compared to over 90 dB for a standard compressor. My compressor works well, just too bloody noisy for a residential area.
www.tradetools.com/product-range/air-compressors/single-phase-air-compressors/origin-air-oil-free-2x-1hp-270lpm-compressor

But that's a compressor not a vacuum pump.

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decrepit said..
But that's a compressor not a vacuum pump.

Industrial vacuum bagging uses a venturi driven by a compressor rather than a vacuum pump. Multiple jobs can be bagged using inexpensive venturis and there is no oil vapour in the work area which is really bad for bonding composites.
A compressor is really handy for other stuff too.
https://www.westsystem.com/tools-supplies/vacuum-bagging-supplies/venturi-vacuum-generator/

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airsail said..

decrepit said..
But that's a compressor not a vacuum pump.

Industrial vacuum bagging uses a venturi driven by a compressor rather than a vacuum pump. Multiple jobs can be bagged using inexpensive venturis and there is no oil vapour in the work area which is really bad for bonding composites.
A compressor is really handy for other stuff too.
https://www.westsystem.com/tools-supplies/vacuum-bagging-supplies/venturi-vacuum-generator/

Hmm interesting how long can you run the compressor for?
How do you regulate the vacuum amount?

Something is not right I have run a HVAC pump - same as the eBay ones but fair enough better quality- for around 30hrs with no oil loss.
OK, its wet around the outlet, maybe lost 10mL out of 300mL

Thats not really a workshop full of vapour. So are the cheap ones really that bad or did u get a dud one airsail?

Many folks do use a venturi vacuum generator off a compressor, but those specs on the west system one show a normal handyman air compressor will run continually to generate vacuum. So its really the same deal -a cheap one will get hot as hell and wear out.

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R1DER said..

airsail said..

decrepit said..
But that's a compressor not a vacuum pump.

Industrial vacuum bagging uses a venturi driven by a compressor rather than a vacuum pump. Multiple jobs can be bagged using inexpensive venturis and there is no oil vapour in the work area which is really bad for bonding composites.
A compressor is really handy for other stuff too.
https://www.westsystem.com/tools-supplies/vacuum-bagging-supplies/venturi-vacuum-generator/

Hmm interesting how long can you run the compressor for?
How do you regulate the vacuum amount?

Adjust the vacuum up and down by changing regulator pressure on the compressor. My current compressor cycles about every 8 minutes, runs for about 3 then turns off. It works fine but because of the noise I use heat lamps in winter or outside in sun during summer to speed the gel time.

R1der's fridge compressor concept works well. Thanks to his willingness to share his design I got up & running. As he said it gets hot. At first I thought it would seize with continuous running. So I had a spare compresser on standby. A $20 insurance policy. The original never seized!
The only problem is my compressor is stubborn to start. I have to switch on/off/on/off to get it warm enough to operate!.
I found getting a good seal on the work to be vacuumed was challenging and frustrating. The tiniest leak will compromise things. Not like compressed air systems that will have similar leaks and operate perfectly. Vacuuming is a bit of a Black Art when done on a budget.
I found trying to reuse a baoard sized vac bag more than a few times was futile. It refused to maintain a seal. I'm guessing it sustained small holes in the process of being used under vacuum. My skin fitting was too good, leaving an impression in the repair! A larger preferated flexible sheet spreads the load over the work area. For a whole board a long piece of hose with holes dreilled along its length inserted lengthways again with a flat flexible preferated material to avoid a vacuumed in hose shaped grove!
Small repairs are easily sealed with a material that looks like Blu Tac bout is 100 X stickier. Placed around the work to be done with vacuum plastic over the top. Again it can work a bit too well. I over vacced my first attempts leaving some big dents!
If you like a challenge this is one. Respect to the pros who do this well!
Hope this helps.

I have often wondered whether a 44 gallon drum with a tap at the bottom and a valve on the filler at the top connected to vacuum line would work. Fill drum with water and allow to drain out via tap on bottom. Would this give enough vacuum? Obviously leaks would be an issue but if job initially pulled down with vacuum then drum valves opened, you would be able to measure loss via volume of water coming from tap and be able to calculate time to top up drum as required. Probably need to maintain at least half the water in drum for sufficient weight of water. Live on a hill so thought this may work but don't know if sufficient vacuum would be achieved.

^^^ NO as 15 inches of mercury = 205 inches of water according to google. So assuming no leaks you will need 5m plus of water column to generate the vacuum.

Just realised 1atm = 10m water so why did I do that math, of course 0.5 bar would be 5m water
lol

Thanks Mark, sort of thought the larger surface area of drum compared to vac hose would act like hydraulics in reverse, but realise now vacuum would still be same. Cheers

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Relic said..
R1der's fridge compressor concept works well. Thanks to his willingness to share his design I got up & running. As he said it gets hot. At first I thought it would seize with continuous running. So I had a spare compresser on standby. A $20 insurance policy. The original never seized!
The only problem is my compressor is stubborn to start. I have to switch on/off/on/off to get it warm enough to operate!.
I found getting a good seal on the work to be vacuumed was challenging and frustrating. The tiniest leak will compromise things. Not like compressed air systems that will have similar leaks and operate perfectly. Vacuuming is a bit of a Black Art when done on a budget.
I found trying to reuse a baoard sized vac bag more than a few times was futile. It refused to maintain a seal. I'm guessing it sustained small holes in the process of being used under vacuum. My skin fitting was too good, leaving an impression in the repair! A larger preferated flexible sheet spreads the load over the work area. For a whole board a long piece of hose with holes dreilled along its length inserted lengthways again with a flat flexible preferated material to avoid a vacuumed in hose shaped grove!
Small repairs are easily sealed with a material that looks like Blu Tac bout is 100 X stickier. Placed around the work to be done with vacuum plastic over the top. Again it can work a bit too well. I over vacced my first attempts leaving some big dents!
If you like a challenge this is one. Respect to the pros who do this well!
Hope this helps.

Relic mine never starts up first time it cycles on and of for about 10 minutes, I have no idea why, maybe the oil is too cold and thick.
After 20 plus years of faithful service I still worry it might die mid job. Yep pin holes in used bags are hard to find, Ive wasted many hours searching for them to tape them up.
Reading this thread it's tempting to buy an ebay cheapie vacuum pump, I imagine the oil in these pumps and any air flowing through helps keep them cool? Does any one know is the board ladies pump and oil based rotary vane pump?

Ive seen one of these for a good price that might do the job www.ebay.com/itm/NASH-ELMO-G200-2BH1400-7AH06-VACUUM-PUMP-/382884871214

Checking out some vacuum pumps on ebay WTF

After acquiring some more on less serious vacuum pumps and compressors I decided to get something cheap , easy to install and wire.
Small 24V pump, now is waiting for glassing/bagging day.
eBay

^^^^ sorry mate its an aquarium pump run backwards.
It will take too long to draw a bag down to vacuum, and nowhere near enough vacuum even after many hours.

Useful to apply enough suck on a hole to draw out moisture a bit faster but that's it.

A tip to remember if running the pump all the time, is use a tap or something to restrict the suction from the pump, in preference to using a valve to let air in. The pump works better if pulling on a vacuum, rather than sucking air. Burns/much less oil and is quiter and probably works better that way.


My setup has a valve to let air in and valve to restrict the vacuum from the pump. Using a eBay pump just like in this thread.
How that makes sense.

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R1DER said..

Relic said..
R1der's fridge compressor concept works well. Thanks to his willingness to share his design I got up & running. As he said it gets hot. At first I thought it would seize with continuous running. So I had a spare compresser on standby. A $20 insurance policy. The original never seized!
The only problem is my compressor is stubborn to start. I have to switch on/off/on/off to get it warm enough to operate!.
I found getting a good seal on the work to be vacuumed was challenging and frustrating. The tiniest leak will compromise things. Not like compressed air systems that will have similar leaks and operate perfectly. Vacuuming is a bit of a Black Art when done on a budget.
I found trying to reuse a baoard sized vac bag more than a few times was futile. It refused to maintain a seal. I'm guessing it sustained small holes in the process of being used under vacuum. My skin fitting was too good, leaving an impression in the repair! A larger preferated flexible sheet spreads the load over the work area. For a whole board a long piece of hose with holes dreilled along its length inserted lengthways again with a flat flexible preferated material to avoid a vacuumed in hose shaped grove!
Small repairs are easily sealed with a material that looks like Blu Tac bout is 100 X stickier. Placed around the work to be done with vacuum plastic over the top. Again it can work a bit too well. I over vacced my first attempts leaving some big dents!
If you like a challenge this is one. Respect to the pros who do this well!
Hope this helps.

Relic mine never starts up first time it cycles on and of for about 10 minutes, I have no idea why, maybe the oil is too cold and thick.
After 20 plus years of faithful service I still worry it might die mid job. Yep pin holes in used bags are hard to find, Ive wasted many hours searching for them to tape them up.
Reading this thread it's tempting to buy an ebay cheapie vacuum pump, I imagine the oil in these pumps and any air flowing through helps keep them cool? Does any one know is the board ladies pump and oil based rotary vane pump?

Ive seen one of these for a good price that might do the job www.ebay.com/itm/NASH-ELMO-G200-2BH1400-7AH06-VACUUM-PUMP-/382884871214

Spot on I reckon: cold oil. I might warm it up with the fan heater first. My shed's in the shade all day and never gets warm. I have to make "cardboard ovens" fed by the fan heater when I use epoxy. Opposite situation to WA where you must battle with stuff going off to fast.
And yes I am careful with the flammable items when using the above. It's fed with a length of 200mm "Flex" duct hose
well away from hazardous stuff.

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racerX said..
A tip to remember if running the pump all the time, is use a tap or something to restrict the suction from the pump, in preference to using a valve to let air in. The pump works better if pulling on a vacuum, rather than sucking air. Burns/much less oil and is quiter and probably works better that way.


My setup has a valve to let air in and valve to restrict the vacuum from the pump. Using a eBay pump just like in this thread.
How that makes sense.

I'm unsure what you mean.... where is the tap going then?

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Mark _australia said..

racerX said..
A tip to remember if running the pump all the time, is use a tap or something to restrict the suction from the pump, in preference to using a valve to let air in. The pump works better if pulling on a vacuum, rather than sucking air. Burns/much less oil and is quiter and probably works better that way.


My setup has a valve to let air in and valve to restrict the vacuum from the pump. Using a eBay pump just like in this thread.
How that makes sense.

I'm unsure what you mean.... where is the tap going then?

I have a tap between the pump and the rest of my setup. The rest of the setup ie the guage, a valve that lets air in, the line itself, the bag etc. After I have got the vacuum in bag working, ie found all the holes and it pulling it excess of .3 of atmosphere, I partially close the tap between pump and the rest of the setup, that way the pump pulls about 1 atmosphere and I get .3 on other other side. I can fine tune with other valve that blleeds air. The coninitous pump work much quiter and use much less oil.

Aaah so the pump sees more vacuum.....
but for how long........won't it equalise eventually? (esp as vac leaks are waaay worse than pressure leaks )

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racerX said..

Mark _australia said..

racerX said..
A tip to remember if running the pump all the time, is use a tap or something to restrict the suction from the pump, in preference to using a valve to let air in. The pump works better if pulling on a vacuum, rather than sucking air. Burns/much less oil and is quiter and probably works better that way.


My setup has a valve to let air in and valve to restrict the vacuum from the pump. Using a eBay pump just like in this thread.
How that makes sense.

I'm unsure what you mean.... where is the tap going then?

I have a tap between the pump and the rest of my setup. The rest of the setup ie the guage, a valve that lets air in, the line itself, the bag etc. After I have got the vacuum in bag working, ie found all the holes and it pulling it excess of .3 of atmosphere, I partially close the tap between pump and the rest of the setup, that way the pump pulls about 1 atmosphere and I get .3 on other other side. I can fine tune with other valve that blleeds air. The coninitous pump work much quiter and use much less oil.

can you post at photo

Cammd, just in case you have access to old Toyota HiAces.........my system which I've used for years has a Toyota HiAce air conditioner pump which I run with a 3/4hp motor.
I use the vac side of the pump and the positive side exhausts any excess oil.
I geared the motor to pump ratio to get the vac pressure I wanted and it ended up running at 920rpm.
I have a car vac gauge plumbed in to the pump top vac housing and I squirt 15cc of oil in here to run for 18 hours.
I run the vac line (garden water system pipe) through an old 9kg gas cylinder and I use a tap in the line (garden system again) to bleed and set the vac pressure. This set up is very quiet, runs happily full time for 18 hours, will pull 0.8 bar over a full board rocker table (I only use 0.4 max usually) . It gets warm, not hot but over heating is no problem, if its a hot day I run an 8" fan aimed at the pump body just in case. These pumps are a great design and are made by Nippon Denso. They are a swash plate crank driven, 10 cylinder slider setup with reed valves on either end of the pump body. Small and compact. They come with a 12v electric clutch on the drive pulley which you can use with a pressure switch if needed although I don't bother and lock it out and run full time.
I'm not sure about Oz but here in NZ we have loads of HiAces and I've owned about 6 of them as my w/surf van over the years and before I sell them, rusted out, to the wreckers, some lose their pump.
The only problem I ever had was sucking resin through which got in the reed valves and lost pressure.
I like that fuel filter in the vac line mentioned in another post.

I went the fridge pump route initially.... had a complete mare with leaks. The stress was killing me so I forked out a bit of cash and got a vacuum pump and ran a bleed valve to regulate the vacuum pressure. Night and day and oh so simple.

I managed to get an anaesthetic pump on stand for $40 .
The art of haggling hasn't left me yet .