I am planning construction of a 3 foot retaining wall, and I plan to
level my back yard with approximately 2000 cubic feet of dirt. The
dirt will be dumped in the street in front of my house. I recently
watched my neighbors spend three days of a similar project hauling
wheelbarrows full of dirt (less dirt than I plan to use) and it made me
seek out alternative, cheap methods of moving all the dirt in one day.
Renting a little earth mover for $400 for a day (delivery/pickup fees,
diesel, rental) is too pricey in my estimation. My new idea is to
instead rent a high-horsepower canister vacuum, or perhaps re-purpose
my home's central vacuum unit, using 90 feet of PVC tubing as a
temporary dirt conduit from the front street through to the back yard.
I anticipate the supplies and rental should cost less than $200. The
first and last thirty feet will be flexible tubing to allow maneuvering
the vacuum discharge around to position the dirt as it's sucked through
and to move with the dwindling pile of dirt in the street.
I figured that if my central vac unit is rated at around 100 cubic feet
of air per minute, I could get perhaps 10% of that sucking large
amounts of dirt, so 2000 cubic feet of dirt at 10 cubic feet per minute
would in theory take 200 minutes. The electricity cost would be small
for several hours of operation, but I'm wondering whether a rental
vacuum or my home's existing unit would burn out under the strain or
need numerous cool-down sessions, pushing the total time spent to many
hours more than I want.
Can anyone tell me why this is a dumb idea? Do you have any better
cheap dirt moving ideas? Any suggestions for other forums on which to
Surrey, British Columbia
There is a real-life device called a mudsucker which is used to suck
mud, silt, etc. out of the bottom of ponds, etc. (hence the name.) It
basicallly is a vaccum with a very long hose attached to it: Of course
in that case the dirt is extremely wet, which helps to lubricate
Have you factored in the cost of replacing the blower motor on your
vacuum when you overload it in this fashion?
Sounds about as smart as using a Yugo to pick up the bags of cement to
pour a 200 sqft driveway.
shows a gigantic
trailer-hauled bad boy. I imagine it would cost quite a bit more than
$200 a day to rent that thing. Also, I don't think I could direct the
output dirt they way that I want to. But I'm pretty sure I couldn't
burn out its motor!
Is the city really going to let you dump a pile of dirt
10X10X20' in the street in front of your house? Will your
neighbors appreciate this?
Why not make room and have the dump truck dump the dirt in your
Dynamite. Catapult. Rotate your house so the rear is in the
street prior to having the load delivered. Rent a "bobcat", and
let 12 willing horses and water-filled tires make short work of
it. Rent a belt conveyor, and shovel the dirt onto the conveyor.
Have a crane lift the dumptruck up and empty it in the backyard.
How much is your time worth?
You are correct, the motor is not usually rated for 100% duty
cycle. You will be emptying the cannister every few minutes.
You will not get 10% volume movement... more like 1% if you have
any hope of not clogging the delivery lines.
"Spend a pound to save a penny."
Be sure and grade the yard so that surface water is directed
*away* from your house.
David A. Smith
David-- My wife agrees with the spirit and letter of all of your
comments. But I'm still convinced it's a workable idea. I need a few
more humiliating responses (preferably from physics Ph.Ds) here before
I give up and hire a Bobcat, etc.
My one quibble with your analysis of the vacuum: the canister would not
be attached; I would be directing the output hose straight onto the
If we could, we would have the dump truck drive down the public walkway
next to our house and dump in the back yard. Our neighbors already
established the precedent of leaving a honking pile of dirt in the
street for a few days with no one seeming to mind. The street is
already narrow because only one side of the street has been developed
I'm guessing his plan is to hook the vacuum hose directly to the intake
of the vacuum impeller so that all the dirt will have to pass through
the vanes of the impeller. This is the way many cheap vacuum cleaners
are designed in that it eliminates the need for a hard body chamber to
hold the vacuum. This means that all the dirt they pick up in their
lifespan passes through the impeller (which is what often wears out
first). I doubt these type of vacuum cleaners last for 2000 cubic feet
worth of dirt (which they only move a short distance). If this guy
actually succeeds in moving a couple of wheel barrows worth a 100' with
this contraption I would be impressed.
My intention was not to humiliate. Who's idea was it to "fill
your back yard"? If it originate with your wife, it may be an
attempt to get you to "tone it up".
You need to review the inner workings of a vacuum:
hose -> enclosed canister (for settling) -> particulate filter ->
fan blades (driven by a motor to move air) -> atmosphere
If you "open the canister", the fan simply draws from the
atmosphere, ignoring your hose. Try that now, rather than
waiting for the big day of delivery.
A company called Exair makes what is called an "air amp". It
takes a stream of compressed air, and directs it around the
inside of a specially shapped "funnel". The Coanda effect causes
this higher velocity stream to stick to the walls, leaving the
air in the center to respond to being surrounded by
unidirectionally moving air. If the downstream side of this
system is open, 1 part compressed air (at 6 or 7 bar) can cause
15 parts of total air movement down, say, a pipe or hose. This
is used to vacuum parts off a floor (for example), but hose
lengths are short and almost always vertical.
David A. Smith
The little I have read about vacuum physics (aha, ignorance is the
culprit!), and a presentation by an unsuccessful vacuum salesman a few
years back tell me that a vacuum works through air flow, not suction.
My home's central unit has the intake flowing into a removable
canister, then the air flows through a large filter hanging in the
center of the canister and then out an exhaust tube. My plan was to
remove the bottom of the canister so the filter was hanging free in the
open air, then direct the dirt away into the yard before it hit the
filter. Will I have destroyed the loop and lost all air flow by doing
this? Will the vacuum motor burn out by being forced to age 153 years
in one day? It looks likely now. I have to hope that I don't injure
myself, another, or our property with a Bobcat, or that the cheap
laborers I hire don't injure themselves on my property and sue me.
I enjoyed your comments and was not really humiliated. If I cared
about the potential for humiliation, why would I ever consider posting
on USENET? The idea to fill the backyard came from watching the
neighbors turn what the home developers left as an uncomfortably
sloping back yard with dying grass from not enough topsoil into a still
quite sloping (therefore no flooding the basement) but better toned
Umm.. the density of the dirt with respect to air? You will definitely
overload the motor.
I like the "pay some kids $7/hr to move the dirt" idea, or even better,
pay them $50 (or whatever seems reasonable) to get the job done- no
slacking that way.