Fluid Mechanics

[Farenheit251]

I was cleaning a very large home on the lake. The guy makes his living as a freelance engineer/genius that companies call in when the regular geniuses have trouble and as an expert witness. He wanted to know how my cleaning worked.

I explained how much airflow I gained with 2.5 hose and why I thought it flowed 50% more air. He corrected me. "Your airflow is what it is at the machine. You need to measure loss of airflow". He pulled up a chart and printed. It was for fluid flow through various size pipes. He said the results would be the same except for turbulence which we couldn't calculate but larger would be better with turbulence.

Across all applicable flow rates the 2" hose lost 3 times more flow. So 150 feet of 2.5" will give the same airflow as 50 feet of 2". A 300 foot run equals 100 feet of 2". I knew it was better but it was neat to see actual numbers.

 

[bob vawter]

my favorite post so far!

 

[Greenie]

The 300 and 100 sounds about right, I've had several guys say they swear the vacuum is the same when they are stretched out with the big hose as they "used" to have on a short run of single 2".

 

[Larry Cobb]

Brian;

That sounds like an interesting discussion.

Fluid flow is more complicated than comparing flow thru a "pipe".
It is loss of lift from the TM to the wand.

Pipe is straight and has smooth walls.

When I was cleaning some epoxy floors a week ago, I noticed lost vacuum effects from more foam in the hose when I applied extra detergent.

The testing we did at Nick's Bar-B-Que did not show much advantage for 2.5" hose at 100' with single 2" wands.

I thought it would show a difference, but I oversaw the testing and I didn't see any problems.

With long lengths or two wands, I am sure that the 2.5" will show less loss of lift from the TM to the wand.

Larry

 

[Bob Savage]

The "4-to-the-door", or 2.5" vacuum hoses really do work, and work best when the truckmount is set up correctly in regards to the blower, it's plumbing, and the powerplant.

If a TM vacuum system is "choked down" somehow, the larger volume hose won't add any significant vacuum gains.

 

[Bjorn]

by the time your 4 to the door 5 to the floor 8 to the ceiling

you could have just used a vac booster and be done with it bringing another vacuum inline to overcome drag is not a drag

 

[bob vawter]

t....i found soma those thingies in the bottom of my Steam Genie waste tank.......one time!

 

[Bjorn]

don't stick a fork in a plugged in toaster either bob it will F uc k up you pacemaker

 

[Duane Oxley]

He was looking at the hose size alone.

The wand plays as important a part in the final analysis.

Not negating the importance of hose here, but the "variable" of the wand's airflow restriction is "key", as well.

For instance, did you show him your wand? Is it a 1.5", 1.75" or 2" shaft? Do you use a whip hose? How big is the wand's slot?

All matter. But the hose part is very cool to hear from your experience this way...

 

[everfresh1]

don't stick a fork in a plugged in toaster either bob it will F uc k up you pacemaker

How do those things work ?

 

[royalkid]

don't worry about it Lamie...they won't work well with your rug doctors...btw, what are you doing on a non-political thread? Is youtube down?

 

[Farenheit251]

I thought it was neat to see actual nimbers instead of just going by sound and feel. I decided to make a 6 foot 2" whip line to be able to swap out with my 25 footer. (It is a good idea to have the mini whip anyways if you are using a water claw for extractions.) The results blew me away. I didnt expect to run the mini whip all the time but with the results I an using it whenever practical. I do lots of vacants and restaurants. On my interior designers house I still run 25' of 1.5".
A mini whip is a cheap experiment costing only a scrap of 2" hose. If you already have 100' of 2.5" give it a try.
Bob Savage mentioned the importance of not having plumbing restrictions on the machine which I agree with, but the engineer changed my thinking a little. The whole purpose of the larger hose is to preserve the airflow you have so it is not lost to drag/ resistance. Any machine can gain the benefit as long as it has enough airflow to quickly put the hose under negative pressure.

 

[GeneMiller]

I recently went to the 2.5 hose and if feels like the whip is hooked straight to the truck regardless of how much 2.5 I have out.

Gene