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  1. #46
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    Hi David

    Just to clarify, there are two types of vacuum system.
    Type one sucks the air out of a space or bag -- the Roarocket kits are the simplest example.
    Type two relies on the Bernoulli effect to create the vacuum. Compressed air is passed through an orifice where it speeds up and in the process creates a partial vacuum. The vacuum pressure can be used for clamping.

    By the description, the Vicmarc vacuum chuck is a Bernoulli type device.
    regards from Alberta, Canada

    ian

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  3. #47
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    Nov 2012
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    Thanks ian,

    I remember a (very) little of Bernoulli from my school physics. However, am I correct in thinking that all the bag systems effectively end up with the same atmospheric pressure doing the compressing or do higher vacuum pumps 'magically' press harder once all the air is out of the bag?

    My inquiry about vacuum clamping was inspired by an article in Taunton's Fine Woodworking by Roland Johnstone 22 May 2017 (on-line). Johnson use a "laboratory vacuum pump" with no cfm or other characteristics specified, probably because the emphasis of his article is on designing and making the clamps themselves. However, the photo of his set-up shows a vacuum pump hooked up to a small gas bottle, which he is probably using as a pressure vessel to even out the work of the vacuum pump. If I can find what specifications work for those clamps and I know the cfm spec for Vicmarc's vacuum chucks then I am hoping I can buy a machine that will serve both purposes. ATM I am awaiting a response from an Australian eBay supplier of small vacuum pumps (around $150.00 single-stage), and have found some old threads on the forums to follow-up as well.
    David

  4. #48
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    For a venturi vacuum system (works on the Bernoulli principle), I think I'd buy a small, portable and quite air compressor that could also power an 18 g brad nailer, (as well as a 23 ga pinner) on teh basis that the compressor is more versatile than a straight vacuum pump
    regards from Alberta, Canada

    ian

  5. #49
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    Oct 2004
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    nsw
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    52
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    Hi,


    Mr Thumbsucker. Can you please tell me why you went with the pump you did, rather than a refrigeration vac pump?
    My brother is a refrigeration mechanic, and when I sought his guidance as to vac pumps, and sent him a link to the pump you bought he couldn't explain to me what benefit there was in getting the pump you did, over something like this?
    9CFM 2 Stages Refrigerant Vacuum Pump Refrigeration Gauges Tools Air Condition
    This one will pull 9CFM (or 254L/min), as opposed to yours that is rated at 140L/min.

    There's obviously more to it, so I'm hopeful you can point me in the right direction. I'm just starting to try to source parts necessary to build my own vac system, and want to make sure I get a pump that is suitable, but not spend more than necessary. Is there a major advantage in the one you got? Is it the maximum vacuum that can be maintained by the pump, or some other deciding factor?

    Also how are you regulating vacuum? Have you purchased some sort of vacuum pressure regulator?

    TN

  6. #50
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    Feb 2016
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    Canberra
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    Do you need to regulate it? Is there any reason you couldn't leave it turned on for the full time?

  7. #51
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    Oct 2004
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    Well my thinking is that ultimately if I build it right the first time, it could end up multi-purpose - used for
    vacuum clamping veneers
    vacuum clamp on the lathe
    vacuum hold down clamp on the bench for sanding small panels etc
    I'm guessing not every application will require the ultimate amount of vacuum pressure possible from the system.
    And in this link (Project: EVS - The Concept) which seems to be the go-to site for this type of application, they include components to regulate pressure etc.

    Personally, I know very little about this stuff, but if I have to build a vacuum clamping setup (as I don't see any readily-available solutions out there aside from the roarockit type stuff, which won't cut it), I want to make sure that whatever I end up buying/building can do everything I'll ever need. I've been down the path of buying tools to do 'todays' job, that under-perform tomorrow when you try something different.
    Any info I can source on the net indicates that others that do this stuff a lot all seem to use a system similar to joewoodworker type arrangement.

    However, I'm happy to be pointed in the right direction. My refrigeration mechanic brother reckons I should just buy the refrigeration pumps for ~$200 and 'just plug it in and leave it on till the glue dries'. But this forum posts suggests there must be a reason people are building using different pumps, and regulating pressures etc.

    Hence any light people can shed on what better pumps offer, and how to regulate the pressure from them, and how/why they do it that way - I'm all ears.

  8. #52
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    The short aswer is oil.

    Here is the long answer:

    Vacuum is an integral part of many laboratory processes, but costs associated with generating a vacuum, such as process costs, user costs and cost to the environment, have never really been considered seriously. Although technology has advanced to provide smaller, cleaner and quieter options, not many people are taking advantage of it. “Vacuum pumps last a long time and many people go through their careers without actually buying one,” says Peter Coffey, vice president of sales and marketing at Vacuubrand Inc. “Hence, people tend to replace their vacuum pumps with what they have used before and not take the time to find out about the alternatives.”

    Oil-lubricated pumps have been around for many decades, while the oil-free diaphragm pumps are a more recent addition. Although oil-free pumps tend to be one and a half to two times more expensive than oil pumps, there are a lot of advantages to their use as well as significant lifetime savings. First of all, no oil is used, and therefore there is no cause for oil contamination and no necessity for oil change or disposal. Oil-free pumps can be built to be corrosion resistant and hence do not require regular maintenance. “Service intervals on better oil-free pumps exceed 10,000 operating hours,” says Coffey. “If you use your vacuum pump 20 hours a week, 50 weeks a year, that’s 10 years before the first scheduled service!”
    The other misunderstanding that leads to the choice of an oillubricated pump is that people think that more vacuum is always better. Oil-free diaphragm vacuum pumps can provide vacuum levels from atmosphere to below 0.5 mbar/torr, whereas oil-lubricated pumps offer high capacities and higher vacuum levels up to 10-3 mbar/torr. “What is more important is matching the vacuum to the application, and almost any application can now be performed using an oil-free pump, with the exception of freezedrying,” says Coffey.
    For certain applications he also recommends considering buying a pump with controls that provide a good balance of speed and control. “Even manual controls are better than none, but electronic controls offer huge productivity advantages,” he says. “In many applications, the type of vacuum control used will determine how much scientist time is needed for oversight and how fast the application proceeds.”
    Another issue is the oil pump in operation turns into a fine aerosol of toxic oil and this is not good stuff to be breathing in. That is why Labs supposidly recommend running an oil vacum pumps under an extractor.

  9. #53
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    Oct 2004
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    nsw
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    Thanks for that info. I knew there'd be a good reason for it.
    How are you monitoring and switching the pump on/off? Did you buy some type of vacuum switch?
    And did you follow joewoodworker's configuration with MAC switch and PVC tanks, or have you gone down a different path here?
    And where did you source vacuum hose and brass fittings etc from?
    I'd love to see some pictures of your setup if you have any.

  10. #54
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    The pump is rated for continues operation and is less then 58 decibels loud so their is no need for tanks.

    I am still waiting for the EZ-VAC bag connector & check valve from Off The Edge Sailplanes :: Vacuum Bagging

    The pump came with a hose and brass fittings.

    However I am still looking for a suitable Inline vacuum pump filter (40 micron). To prevent glue getting into the motor.

    I have purchased some vinyl and special glue and once I have all the parts I will be making the bag and doing a test run.

    I will post back.

    FineWoodworking has just posted a log post about building your own vacuum.

    A closer look at Rollie's budget vacuum pump - FineWoodworking

  11. #55
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    Apr 2005
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    Nerang Queensland
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    66
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    Quote Originally Posted by ian View Post
    For a venturi vacuum system (works on the Bernoulli principle), I think I'd buy a small, portable and quite air compressor that could also power an 18 g brad nailer, (as well as a 23 ga pinner) on teh basis that the compressor is more versatile than a straight vacuum pump
    Don't, a Venturi vacuum pump takes a lot of air, so you need a really big compressor to vacuum any length of time. If you get a small one it will quickly burn out
    Neil
    ____________________________________________
    Every day presents an opportunity to learn something new

  12. #56
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    Nov 2012
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    Brisbane
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    Quote Originally Posted by thumbsucker View Post
    FineWoodworking has just posted a log post about building your own vacuum.

    A closer look at Rollie's budget vacuum pump - FineWoodworking
    In that article it is a shame that Rollie (Roland Johnson) does not say which model of Welch Duo Seal pump he has used. Those pumps are all oil-type pumps, belt-driven by 115 volt motors so are not what we would use here in Aus anyway, but the actual model spec would have been useful to give its capacity. The current line of Welch Duo-seal pumps range from small 25 l/min units to 650 l/min monsters. His looks like a tiny one, but there are a few other little ones at the bottom of their range too.

    As thumbsucker says above, the newer model oil-less pumps look like much better value if buying new and for the longer term here in Aus.

  13. #57
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    Apr 2014
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    Kew, Vic
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    Hi Thumbsucker,

    just following up to see how you went with the 140RVD (Rocking Piston, Vacuum, Dual Head) vacuum pump for your vacuum bagging? I'm inching towards buying a pump, but would value your feedback on the pump so far.

    I note that Vacu-press (Yareus in Australia), Bagpress and Airpress (both in UK) all use rotary vane pumps rather than dry head piston, and the last two at least use German-made Becker pumps (also available from Rob at Bettervac). I haven't been able to discover whether one type is better than the other - do any forum members have any advice or views? To be used for small curved items mainly.

    Many thanks,

    Brian

  14. #58
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    Apr 2014
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    I bought a 3.5 CFM rotary vacuum pump advertised on ebay on the 8/8/17 for $27.63 delivered from Germany!

    Went to copy the listing to notify WWF of the bargain and I find that the listing has been withdrawn with a note that if you have paid they will honour the sale. So I am hoping that it will eventuate.

    Vac pump.jpg
    This is the picture that was advertised does anybody recognise it?

    I thought that it was too good to be true but at that price I couldn't resist it.

  15. #59
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    Nov 2012
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    Quote Originally Posted by homey View Post
    I haven't been able to discover whether one type is better than the other - do any forum members have any advice or views? To be used for small curved items mainly.
    Brian
    Hi Brian,

    I'm sure that Thumbsucker reply on his experiences. However, in the detail covered above by various posts it seems clear that if you want the safest and best you would buy a rotary vane, oil-less pump. The oil vapours from the piston pumps is toxic apparently. They are more expensive but will last longer and be quieter.

    In my case I found that I can run a Vicmarc vacuum chuck from my Festool CL26 vac and I use a Roarrocket kit to make my own veneered boards for the bases (and sometimes lids) of boxes. The kit works well and I have never had a failure. I use Purbond, a low-foaming polyurethane for such work. The Roarrocket kits are designed for the work you are doing ("small curved items mainly") but also work fine for flat sheets such as I make. I make up sheets the full size of the veneers that I have and then cut the size I need for the box from that sheet. I get numerous box bases from one glue-up.

    It seems clear that the small piston-type, cheapo Chinese units will also work (if you buy the correct capacity) but they tend to be noisy and the toxic fume issue put me off buying one.

    David

  16. #60
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    Apr 2014
    Location
    Kew, Vic
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    Hi David,

    Thanks for the feedback. Noise and fumes would both be issues for me. I spent some time in a workshop in Yorkshire recently where the noise of the small piston pump was overwhelming.

    My work is mainly boxes and virtually all have veneered tops and bottoms. That's a great tip, by the way, to make panels the size of the available veneer then cut to size later. Why didn't I think of that? Thanks!

    Generally I've used TiteBond for flat panels but for curved stuff I've used urea formaldehyde (cascamite) to give a rigid bond. Do you use Purbond for curved work?

    Given your success with the Roarocket kit I might give that a whirl before taking the plunge on a pump.

    Bohdan, your pump looks like this one at $US56:

    https://www.zeny.us/products/zeny-3-...410a-r134-blue

    Zeny are a company that sells all sorts of stuff - outdoor canopies, pet supplies, sports gear. Essentially they find a manufacturer, stick the Zeny name on the product and sell it direct or on eBay. Will be interested to hear what you think of your $27.63 pump

    Thanks again,

    Brian

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