Made my own Venturi...

[vacpress]

yes. sweet...

[TAXI]

hey guys I was reading a looking at some of the post for the vac looks like a great idea. I want to use it where i work at here is the problem am having. I work at place that sells fly ash and we have spills and instead of using a shovel to clean it up we are thinking about making one of these from a 55 gal. drum so what ever we suck up will go in to the drum. I seen the pic. for it can i use the same one that in the pic and attach it to the drum or would I have to make a bigger one any help will help!? as am getting tired of shoveling

[Geof]

hey guys I was reading a looking at some of the post for the vac looks like a great idea. I want to use it where i work at here is the problem am having. I work at place that sells fly ash and we have spills and instead of using a shovel to clean it up we are thinking about making one of these from a 55 gal. drum so what ever we suck up will go in to the drum. I seen the pic. for it can i use the same one that in the pic and attach it to the drum or would I have to make a bigger one any help will help!? as am getting tired of shoveling

Don't apply too much suck to a 55 gal drum unless it is a very heavy wall one. I have sucked one down to about 1/3 its normal height with a compressed air venturi.

[keebler303]

you will need more flow for a shop vac type thing. Why don't you just use a standard vacuum and plumb it into a drum as the reservoir.

Matt

[Salty72]

shark hope you don't mind I took you design to the next level and came up with this, I made the jet and the body out of a solid piece of brass, I can tell you that once adjusted and running a 6 BAR(about 85Psi) and connected directly to a vacuum gauge it draws about 15"Hg (7.3Psi) when connected to the MDF former I built and sealed I get 11"Hg (5.4Psi) obviously not quite as sealed as I thought

Note: when running a 2BAR (30Psi) you get about 7"Hg (3.4Psi) off the gauge I did notice the as you slowly increased the input air pressure, the guage increased quickly.... but to get the last few Inches of Hg out of the venturi It took a rather large increase of airflow and although I didn't map the flow rate -V- pressure... So... I am only guessing but at about 60Psi from the compressor I would believe is optimum.

Next Question is.....If I double the diamentions of the venturi will I get "better" results (notice how I didn't qualify Better???? )

[Salty72]

Also if you can't get any rubber foamy stuff.... you can place "BLUE TACK" between your work and the Vacuum clamp, this trick works really good.


Definition:Blue Tack is a 3M product that resembles a soft putty, It is used to hang papper from just about any surface and has the consistancy of plastercine but never hardens..

[Bob La Londe]

The maximum force you can get is 1 atmosphere of pressure, 14.7 psi, if you are able to draw a perfect vacuum. The best vacuum you can get with a venturi is about 90% of a perfect vacuum which is about 13.2 psi. It is fairly easy to get around 60% to 80% of a perfect vacuum with venturi which is between 8 and 9 psi. This does not sound like much but if your part has a decent sort of area the total force holding it down can be large; at 60% vacuum one square foot, 144 square inches, is clamped with a force of 1152lbs. All this assumes your system does not have any leaks; venturi vacuum generators cannot overcome leaks.

Would you say based on that then, that Vacuum clamping ins't all that suitable for smaller parts? Say, like a 1 X 3 brass plate for engraving with a drag engraver? I tried yesterday with an HF venturri vacuum and was not pleased with the results. I made the vacum fixture with about .125 lip under the plate all the way around. If I pressed down gentley to start it would pull a vacuum and the part would stay put, but the tiniest little catch like a chip sticking for a fraction of a second would result in the plate shifting.

I wound up doing my job old school with a cheap drill press vise with parallel steps machined into the jaws. I had 17 plates to engrave and the idea of using a vacuum clamp was really appealing.

Or, would you say the HF vacuum was not giving optimal results? I don't feel like I was getting the 14-16 lbs of holding force you say is possible. I was able to pick the plate up with a fingernail against the holding force of the vacuum. It would slide a little bit before my finger nail would catch and lift it.

P.S. I looked at the HF "pump", and it looks a little simpler than the OPs drawing after I got it out of the fancy plastic box. Just an aluminum block with a 1/4 NPT fitting on one end and a 1/8 NPT tube on the other, and the air exhaust parrallel to the two. Seems like the vacuum passage has to make a 90 inside the block. I wonder how much that reduced its efficiency. When I get done with my current project I may mill it in half to see how its built.

P.P.S. I was going for a metal to metal contact. I'm sure I had some leakage at the corners, although I did finish in exact stop mode with a finish pass of .001

[LUCKY13]

I am not sure if it would work, but instead of going bigger on diameter what about building a sort of two stage unit? I dont know the math but one stage should assist the other to help build much better vacume.


BTW, they sale a compressor operated vacume unit for automotive ac work that is faily cheap. I have one but its been a long time sense I had it hooked up and I remember getting better than 20" of draw on a AC system. Not as good as a pump but good enough to get the job done. The one I have is either Mac or Snap On so it was good quality. I dont have a compressor right now to test it and I had never been inside it. I would guess it was built much like these DIY units, or maybe even a staged unit.

Jess

[gurew]

i dont understand why you just dont goto your local pawn shop and buy a vacuum pump used in AC work...thats what i use for carbon fiber work...the venturi way is lame as hell and a huge waste of energy and lots of wear and tear on your compressor

[Bob La Londe]

i dont understand why you just dont goto your local pawn shop and buy a vacuum pump used in AC work...thats what i use for carbon fiber work...the venturi way is lame as hell and a huge waste of energy and lots of wear and tear on your compressor

While a regular vacuum pump would probably work better I've never been in pawn shop that didn't want new+ price for stuff. I quit looking for anything in pawn shops years ago.

[gurew]

craigslist? i have boiught 2 of them in my lifetime..1 from each source and both about $100-200 less than new price and both were almost never used...