Split the input….hmmm. This is not my field, but from the formula it looks like the big inputs for the pressure differential are density of the fluid (the air) and the velocity.
Air density will track linearly with pressure, and a big enough compressor could keep up a steady pressure. But splitting the pipe in 2 directions will cut the velocity in half. Found this little guy for calculating velocity of air. V=fps P=psi D=pipe diameter If I have a trailer compressor at 100psi and 180 SCFM then I should get about 70fps through a 1” pipe. 1" pipe = 70fps 3/4" pipe = 123fps 2x 1" pipe = 35fps 2x 3/4" pipe = 62fps That velocity drop reduces the pressure differential….and that seems to be a square function so it’s a very significant change. The pressure differential ought to linearly affect velocity of the vacuum. ….BUT the lifting force of the vacuum ought to be a matter of velocity and mass of the airflow (because F=MA) So a tighter constriction increases velocity, but a wider pipe increases total mass of air you can move. Since force is a straight product of mass and acceleration I think you’d want to reach the highest possible intersection of CFM and velocity. …..and at this point I’m out of math ideas and I’d resort to testing experimentally. Like measure the time it takes your vacuum to lift 5 gallons of water with various sizes of pipe and venturi constrictions. -Adam From: AF <af-boun...@af.afmug.com> On Behalf Of Steve Jones Sent: Monday, May 22, 2023 11:35 AM To: AnimalFarm Microwave Users Group <af@af.afmug.com> Subject: Re: [AFMUG] Air vac I use an auger to dig them, vac to clear them. Same thing with the airspade/airvac combo. I dont do posts less than 48 inches. Whats really pushing this is the last project was installing 2 inch duct for the power company, the old primaries were failed concentric, as it turns out the stuff is dangerous, it faults on its own, jabbing shovels and post hole diggers at it is a recipe for disaster and water is its mortal enemy. Im chasing more contracts with that power company to replace more of that concentric. Im not gonna get the cutting power of water, but ill have dry spoils to put back in the hole. I wish I hadnt done all the drugs, id be able to understand the maths on this, im wondering if I cant split the input and double the lift with two venturis On Mon, May 22, 2023 at 9:23 AM <dmmoff...@gmail.com <mailto:dmmoff...@gmail.com> > wrote: So you dug post holes with a shop vac? Is it sandy where you are? I feel like I hit about 10,000 rocks per post hole. Many too big for a vac hose, and many just big enough to clog it. I might have to try it anyway. From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > On Behalf Of Steve Jones Sent: Sunday, May 21, 2023 6:12 PM To: AnimalFarm Microwave Users Group <af@af.afmug.com <mailto:af@af.afmug.com> > Subject: Re: [AFMUG] Air vac I'm having better luck with the prototype than a shop vac already, just trying to improve the lift. Toting a generator isnt really an option. I also just have a shop vac hose, if theres moisture the dirt collects on the sides with a shop vac and loses lift. That's how I've always dug post holes. On Sun, May 21, 2023, 3:53 PM Chuck McCown via AF <af@af.afmug.com <mailto:af@af.afmug.com> > wrote: I think you would have better luck with a strong shop vac and a 30 gallon drum. I have seen guys do that and it worked OK. Air powered vacuum producers work but I don’t know how well. Sometimes they are called eductors or ejectors. Take a look at this one: <https://www.globalindustrial.com/p/2-in-line-vac-only-aluminum?infoParam.campaignId=T9F&gclid=CjwKCAjwgqejBhBAEiwAuWHioM68tuz0PVLcvHFy4CRspRtvhy5gEQQryMrUkOoNv4MVeUTRSWTkvxoCrv8QAvD_BwE> https://www.globalindustrial.com/p/2-in-line-vac-only-aluminum?infoParam.campaignId=T9F&gclid=CjwKCAjwgqejBhBAEiwAuWHioM68tuz0PVLcvHFy4CRspRtvhy5gEQQryMrUkOoNv4MVeUTRSWTkvxoCrv8QAvD_BwE Best Regards, Chuck McCown McCown Technology Corporation 8401 N Commerce Dr Lake Point, Utah 84074 801-250-9503 Office 435-830-4306 Cell <http://www.mccowntech.com> www.mccowntech.com <http://www.microtrench.pro> www.microtrench.pro <http://www.terabitnetworks.com> www.terabitnetworks.com From: Steve Jones Sent: Sunday, May 21, 2023 11:56 AM To: AnimalFarm Microwave Users Group Subject: [AFMUG] Air vac I need advice from you nerds. I'm a broke joke, so hydrovac isnt in my budget. Besides, I want dry spoils to put back in the hole. This revision works for venturi. I have multiple size reducer but right now I'm just doing 3/4 to to inch. The 3/4 to 1 then 1 to half back to 1.5 for the venturi side seemed to have the best lift, but the hardware store didnt have everything, so it's all in 2 inch right now I'll dump to a 2000lb peanut sack if I can find one, but for now I'll just use a 30 gallon drum and dump on the mega movers. This is for use in conjunction with the airspade I did have some coin to get. Venturi math gets complicated and I'm full retard so I need to find he best ways to increase negative pressure and where to drill the ports. I also wonder if theres an option to recapture the exhaust into the airspade. I need you nerds to go full geek. If I can get valves correct I'll have the local machinist make me a couple that are pressure rated. This is to mimic the airvac I also cant afford. This proof of concept has the lift to clear potholes and handholes, but I need to clean it up and get more efficiency. A side discovery is that this setup is perfect for blowing straw and seed with glue _____ -- AF mailing list <mailto:AF@af.afmug.com> AF@af.afmug.com <http://af.afmug.com/mailman/listinfo/af_af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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