Gear Drive vs Direct drive

scottwash

scottwash

New member
I got this off a ad.

Designed to be integrated into an existing pumping unit to reduce the gear ratio and thereby reduce the size of the motor needed to operate the pumping unit.

My question is how much larger of a pump can you go on a 13hp -
gear drive compared to a direct drive unit?
 
It doesn't change the horsepower needed, just slows the pump rpms.
 
Russ is right that ad is full of it.

You can however put a large pump on a 13 hp and get an increased gpm or higher pressure but not both. You need to fit within the standard formula gpm x psi /1100 = required hp (gas engines) (or hpX1100 / gpm = psi) . For example if I want 12 gpm I can get it but only at 1191 psi. (13 x 1100 / 12 = 1191)
 
Paul, I don't like that formula for horsepower requirements. It gives a fantasy number that is only right under perfectly ideal conditions, and is the absolute max horsepower that an engine creates under wide open throttle and full governor travel.

A more realistic formula is [(psi x gpm) / 1450] x 1.5. That is the electric horsepower formula compensated by 50% for the gas engine.

So...12 gpm x 1000 psi = 12000
12000 / 1450 = 8.276
8.276 x 1.5 = 12.4

At 1100 psi, you need 13.65 hp.
 
Russ Johnson said:
Paul, I don't like that formula for horsepower requirements. It gives a fantasy number that is only right under perfectly ideal conditions, and is the absolute max horsepower that an engine creates under wide open throttle and full governor travel.

A more realistic formula is [(psi x gpm) / 1450] x 1.5. That is the electric horsepower formula compensated by 50% for the gas engine.

So...12 gpm x 1000 psi = 12000
12000 / 1450 = 8.276
8.276 x 1.5 = 12.4

At 1100 psi, you need 13.65 hp.
Click to expand...
Some one pass the calculator please! :)
 
Russ Johnson said:
Paul, I don't like that formula for horsepower requirements. It gives a fantasy number that is only right under perfectly ideal conditions, and is the absolute max horsepower that an engine creates under wide open throttle and full governor travel.
Click to expand...
Bingo!

Since we are an ISO 9001 company we have to advertise the exact flow rate and pressure. Just about every pressure washer company rounds up so a 3.7 gpm machine is marketed as a 4 gpm. Heck, I've seen 4.2 gpm units marketed as 5 gpm machines. I've lost several sales because my machine was honestly advertised against one that was rounded up.

Then when you try to explain to a customer why it takes a 16 hp machine to compete against what others are claiming to get out of a 13 hp unit the discussion gets even more confusing. Not only do most round up, you then have to discuss engine rpms and longevity. Obviously a unit running at 100% isn't going to last near as long as one running at 70%. Many people just look at the stated performance and price without considering the long term reliability. Most first time buyers don't even know its an issue.
 
To make this thread even more interesting, it would be nice to show some of the advertisements and labels off the machines that are rounding up, fudging the numbers and out-right lying to the consumers.

I know it could be seen as bashing but it is just telling the truth so consumers understand, what is wrong with helping and educating the consumer?

It would be nice if the manufacturer would put the math showing how they got their gpm and psi along with the pump chart showing what it does at certain rpm's and hp so the consumer could do the math right there and verify that it is true.

Maybe if this was started by the big companies, it could start a "truth trend" so consumers would be better informed, be able to compare apples to apples and they would know who is just lying to get their money.

This might be a great topic for the industry publications.
 
Christopher said:
To make this thread even more interesting, it would be nice to show some of the advertisements and labels off the machines that are rounding up, fudging the numbers and out-right lying to the consumers.

I know it could be seen as bashing but it is just telling the truth so consumers understand, what is wrong with helping and educating the consumer?

It would be nice if the manufacturer would put the math showing how they got their gpm and psi along with the pump chart showing what it does at certain rpm's and hp so the consumer could do the math right there and verify that it is true.

Maybe if this was started by the big companies, it could start a "truth trend" so consumers would be better informed, be able to compare apples to apples and they would know who is just lying to get their money.

This might be a great topic for the industry publications.
Click to expand...
So do some research and write a article. Don't be shy...... Kind of all new news to me!
 
And how about rated vs max horsepower? Are all brands labeled with max hp instead of recommended hp?

Also you can just divide by 967 for the electric x 1.5 formula - one less step
 
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