Direct Drive question

[Flipper]

When asked this question, here is the reply I send -

The larger the pressure washer, the more often you clean, and the longer you spend cleaning each time, the more you need belt drive.

One leading pump manufacturer privately admits warranty claims on direct driven pumps are about 3 times higher than on similar pumps that are belt-driven.
<O</O​

Belt driven pumps usually operate at lower RPM with a larger oil capacity. A pump coupled directly to a motor or engine places strain on the motor and mounting bolts and will absorb extra heat and vibration that will shorten the life of the unit. Most direct drive pumps do not really contain enough oil to do the best job coping with the extra heat. With direct drive, anything that happens to the motor happens to the pump and vice versa. Even "high quality" direct drives will require more maintenance, may be more difficult to repair (pumps nearly impossible to remove from engine or gear shafts are common), and will require major repairs more often.
<O</O

Direct drives can be built cheaply in a compact and efficient package. But small inexpensive direct drive units may have a life expectancy of only 100 hours.

Improvements such as gear reduction drives, shock absorbing mechanisms and more precise machining, have made direct drives better, but at a cost that begins to rival belt drive. For continuous or frequent use they cannot overcome the inherent advantages of a quality belt drive.<O</O​

 

[Russ Johnson]

Hi, Philip. Your career sounds fascinating.



"3 times higher than on similar pumps that are belt-driven."

Is that ratio based on total pumps in for repair or is it based on units sold. There are thousands more direct drive machines sold in the US than belt drives. I know my sales ratio is about 1 belt drive to 10 direct drive of different sizes.

We had bad storms around here last year, so there was a massive demand for generators in our area. I had several generators of the same series come in for warranty repair, and 1 of another brand. My first thought was "substandard equipment", but then I got to thinking. If they sold 25,000 units area-wide (city of 1,000,000 pop.), and I saw 6 under warranty (and I do 85% of the warranty service for this area), then the failure rate per units sold was very small.

Welcome to the nut house. I look forward to your posts.

 

[Tony Shelton]

just get a pressure guage in after the injector to set the flow right.
they too..
... are really low cost.

Jerry, you're killing me with the low cost thing. oke::wave2:

I don't do the same type of cleaning most guys around here do. I'm training guys from all over the western hemisphere, some of which have never even used a pressure washer.

I'm trying to come up with the most bang for the buck while not overspending on things that are unnecessary.

When I first started we cleaned with ultrasonic machines. I can't tell you how many thousands I wasted before I discovered that a simple pressure washer was more than adequate.

Then I spent around $9k on a brand new hot water machine because I was afraid of buying a lesser brand and wanted the warranty. Later I found out that most of our work can be completed with as little as 1500 psi.

My latest experiment involves the idea of one hot box and up to four 4-5 gpm cold machines. (using the box only when needed and only on one machine) If we need four guys cleaning filters we can do it running all four machines.

If we need two guys cleaning coils we can do it @ 9 gpm running all four.

Or maybe we just need one guy cleaning filters on a quick roof. In that case we only have to fire up one machine.

a 13hp motor uses a lot less gas than a 30 hp.

Another advantage to multiple machines is that you don't have to worry about calling it a day when one unit breaks down. We haven't had that problem in a few years because we have backup.

I'm just trying to design something reliable and inexpensive to run to keep profits up. I do understand the value of buying good parts, but my days of spending a lot of dough on an experiment are over. Thus the chinese motor and the DD unit for this experiment.

One more question though, when hooking two machines together, one 2500 psi and the other 1500 psi both with about 5.5 gpm, what purpose does installing check valves on each line serve. I've tried to sit down and draw it out, but I can't see any benefit to it. I would imagine you will have to adjust both unloaders to match so I can't see the reason for the check valves. Is it to keep something bad from happening to the machine that is shut off while the other is running? Is it possible for pressure to make a pump run backwards? I can't picture it.

 

[Russ Johnson]

I like the check valves in case of an unloader failure. The unloaders have a check valve at the outlet. It's just a redundant safety measure, kind of like putting a pressure switch and a flow switch on a hot water machine.


You know, Tony, you might do well to fasten pipes to the boom on your lift joined by 1/2" pressure hose. That way there's no weight to pull up. Hook the bottom to the the pressure washer(s) and hook up the gun hose(s) at the top of the lift.

 

[Christopher]

Great tip, Paul !
Maybe the ST61 injector with the variable ventui would be even better,
since you can adjust the flow through it.
...and they are really low cost.

Who makes the ST61 injector Jerry? I have not heard of that one before.

Does that just regulate the flow or is it an injector by itself?

Thanks.

 

[Flipper]

"3 times higher than on similar pumps that are belt-driven."

Is that ratio based on total pumps in for repair or is it based on units sold. There are thousands more direct drive machines sold in the US than belt drives. I know my sales ratio is about 1 belt drive to 10 direct drive of different sizes.

I'm not 100% sure. Someone emailed me that information a long time ago. From my understanding, it was based on percentage. In other words, 1 in 10 for belt driven units versus 3 in 10 for direct drive.

 

[Sirocco Jerry]

Chris,
the ST61 is made by Suttner,
it is a variable-venturi injector..
you can leave it in,
betwen your heater and hose-reel, with venturi open all the way, to NOT restrict flow when you're not using it,
Then you can adjust it in, to the point it draws soap when you want it,
with ANY length of hose you want to use on the outlet run.
It's the only injector I know of that works that way..
..a "cool tool" for sure.
I think Russ sells 'em.