Hey there guys, first of would just like to thank this forum for providing such a wealth of knowledge for people like me. I joined up about a year ago and started reading up and asking questions in regards to composites and got some really good information.
During the past year I have been working with fibreglass quite alot and I think Im at the above average level now and can make plugs/mold/products of various complex shapes and sizes.
Lately I have been thinking about working with carbon fibre and the likes of it and have been reading up all the information again, I think this time around I will try out some infusion and what not.
Anyways Im looking at buying my first pump now and would like some information and details in which I should look out for.
I will be starting off with small stuff and have a play around with that first but ultimately I would like to be able to work with large items such as cf bonnets and trunks for my car.
For items that are large as these, what should I look for in a pump? Thats in terms of hg/psi/cfm/hp etc… This is more of a personal hobby rather than something for the means of revenue so I have no problem with having a small pump and making one item at a time.
Any recommendations, information or details will be greatful
The thing is all these cfm, psi, hg, hp etc… terms, I know what i t means and what it represents but never had any experience with them so have no idea what would be the “requirements” for what I stated.
Im not asking where to buy one but rather what to look out for. Problem is that I live overseas so shipping is a pain in the ass so Im trying to source one locally with the specs I need
Im also going to keep my eye out for a first pump. I dont even know where to look or what to ask for. What exactly are these types of air pumps called? And what business what sell them? My fiberglass supply store doesn’t sell any vac gear.
I’m not the most experienced guy on here but I’ll give it a shot.
CFM = cubic feet per minute. Your requirements will vary depending on the size of the parts you want to make. If you’re producing small car or motorcycle components you won’t need a pump with a large CFM capacity. One or two CFM would suffice if it is capable of pulling an appropriate vacuum, see next…
HG = is a mathamatical abreviation for “Inches of Mercury” . Without going into a long diatribe on vacuum you can find everything you ever wanted to know on wikipedia here…
Most pump mfgrs will have a rating on their pumps that equate to the Torricelli’s (SP) mercury barometer. IIRC 30" HG is a near perfect vacuum so the higher the number the deeper a vacuum the pump can draw. I think my Robinair says 29" HG. There are other pump mfgrs that’ll specifiy microns for their vacuum pump capacity so the lower number there is important.
PSI = Pounds Per Square Inch which is a commonly used specification for compressor mfgrs. Again the wikipedia article listed above will explain that. Not very important in vacuum infusion process unless you’re using a venturi “vacuum generator”.
When it comes to vacuum pumps it’ll probably relate to the capacity (volume) and performance (vacuum attainable) of the pump.
So it pretty much boils down to cost vs performance when deciding on a pump. If you can give us some idea of the size and complexity of the project we can help you more.
The Robinair, Gast and a few other pumps are good choices for the hobbiest and professional. With proper care they’ll get the job done and last forever. Your most economical option (<$50) would be to refit a refrigerator compressor for use in your infusion projects. A little searching you’ll find that info on here as well.
IIRC the pump was about $200 Cdn and another $100 in fittings, switches, valves, piping, etc. I’m planning on infusing a whole 30’ plus boat so I did some research on pump capacity etc. Check e-Bay for vacuum pumps and you’ll find a few, new and used. Most vacuum pumps are easily rebuildable so don’t hesitate to pick up a used unit just make sure you can get the parts to rebuild it first.
I agree, Gast make a really good,small pump and it is very quiet too. I’ll try and get photo and part number. Welch also make good pumps, but they’re expesive, professional models.
Got mine off of e-Bay from a supplier called “Climate Doctors” IIRC. I don’t think they sell on e-Bay anymore. Good price under $200 but they took forever to ship it.
well robinair pumps pull 50 microns for the non cooltech pumps, cooltech robinair pumps pull 20 microns, yellowjacket pulls 15 microns
0 microns is like pulling 30hg (perfect vacuum) so the lower the micron number the better
also the cfm (cubic feet per minute) i guess if i were you i would look for something around 5-6cfm unless you have more $$ to spend… thats just how much air it will move per minute…higher the cfm faster it wil suck all the air out
Just go and find yourself a fridge vac pump. You can find them for sale for cheap or free at your local dump. I have been using one for a while and it works great. Pulls about 28" at 3000ft elevation.
Thanks for the info KnottyBuoyz. Like I mention though, in terms of size and complexity of shapes a car bonnet would probably be the biggest thing that I will make or attempt to make.
With that in mind, what kind of cfm rated pump would I be needing? 5, 10cfm??
As for a refrigerator pump, I have read up on this and there seems to be a few people running that set up on this board. My question however, what kind of mould size limit would be present on this? Im guess it wont be powerful enough to infuse a car bonnet???
The size of the pump (volume) isn’t the most critical factor. What’s important is that it can pull a deep vacuum. A car hood with a 5 cfm pump would probably take less than a minute to pull down and with a 2 cfm pump it’d take 2-3 minutes. It’s only a measure of volume of air the pump can move per minute. Once the bag with your part is pulled down to maximum vacuum it won’t be moving great volumes of air, it ain’t like a shop vac!!!
As long as you’re not in a hurry a low volume pump is fine. A good all round pump is something in the 3-5 cfm range. Anything larger means bigger motors, more cost, more heat, more noise, etc. and aren’t any more efficient than the refer compressor.
There’s a fella who recently posted on one of my threads, Fram, who’s building a tri-hull catamaran using resin infusion.
He’s using a small lab pump and it works fine. You can probably imagine that it takes awhile to pull the bag down but after you achieve a good vacuum you don’t need volume.
the fridge pump works great. It pulls down medium size molds fairly quick. If you build yourself a small pressure vessel/pressure pot, the additional volume will pull the bag down real quick.
well i was pulling 22-23hg with the other vaccum generator i had, i always got some kind of bridging somewhere…i hated it…now i pull 28hg and that pretty much solved all the bridging i had
I have been using my fridge pump for some time now, works great, absolutely silent, and works well. it gets my about 27-28" Hg (I’m at a high altitude).
Love my fridge pump. I run a double reservoir now made from 4" PVC piping. Each about 3ft long. Once the tanks are charged/evacuated I can pull out a hood or trunk mold in about 3mins or so.
I;m still wanting to get a setup with a mac valve and vacuum switch so I dont have to leave the pump running until the resin gels. With that setup the pump will kick on when the vac falls to a set limit. genius!
Looks like fridge compressor pump its gonna be then lol!
Just thought someone can give me some extra feedback though, for this pump to work though which would be the right one to use?
Are we talking about the pump out of a normal kitchen fridge/freezer or would something like just a small garage/bar fridge work just as well too?
Also whats the deal with these pressure pots/reservoirs? How do they make the process faster? Are you guys just closing the line that runs from the mold to these pressure pots till it reach full vacuum then releasing them or something?
the reservoir acts just like a reservoir, but in this case as a reservoir for a vacuum, when you open up the valve it would equalize the pressure between the mold and the reservoir, jsut a way of speeding up the evacuation of the mold. I don’t have anything like this, I find it more then quick enough to evacuate my molds.
Just call around to 2nd hand appliance shops or those repair apliance shops, chances are they keep old fridge compressors. ask to buy one, just make sure they have removed all the freon in the propper manner…
the ones that I have come with a built in mech to automatically start up, some might need one put on, ask around for one that has on on it, that much easier and less hassle.
I just run the line form the compressor to the mold and clamp off the lines from the mold etc as I need.
