Standard small engine (single cylinder, 4 cycle, 3 to 14 hp) rpm is
3600, some later engines run a few hundred RPM faster.
Most of the pumps I found were rated at 3450 to 3600 RPM for full
output. Note that you can get trash pumps, semi-trash pumps, clear water
pumps, and high pressure pumps.
Yours appears to be a semi trash variety. This is good for some soft
solids like an occasional leaf or bird dropping, high volume, lower
Karl Townsend wrote:
For long life you want most common engines to run in the 1400rpm to 2000
rpm range (depending on size). Ditto for noise, faster = noisier. 60HZ
alternators need to be locked at 1200rpm, 1800 rpm, or 3600 rpm for 6
pole, 4 pole, and 2 pole alternator heads. Yours is a DC unit, they can
build the windings to produce optimal output at whatever the engine
wants. 1400 rpm in a 4 cylinder flathead is a long life setup.
:I just bought a trash pump without the gas engine.
:What RPM do I spin it at?
:FWIW, I hate small gas engines. Nothing but trouble. I'll use a 3 phase
:motor for this job.
Looks like a 3600 RPM electric motor should be a good match.
3000 RPM .
Need to start on Propnae . Exh is routed around to heat liquid fuel
to "regenerate" heat into the intake .
Then switch to liquid , turn off propane .
Japan cant sell machinery in U.S. ,
Jap' makes motors in China , China trademark . missing the Jap name
Price is highly subsidized .
13HP motor has a balance shaft and retards camshaft to lower
cranking PSI , for easy starting .
3400-5500 RPM depending upon size and engine used, based upon a quick glance
at the search results.
On Fri, 3 Apr 2009 17:43:36 -0500, "Karl Townsend"
If you want to use an electric motor you can go a bit smaller - If
it calls for 5.5 HP gas engine, you can probably drop to a real 3 HP
electric motor - a 5 HP would spin it without breaking a sweat.
For some reason small gas engines are rated at gross HP, and when you
subtract the power used to run the cooling fan...
And find out the optimum speed for the pump head - probably 2,400
RPM to 3,600 RPM range common for gas engines.
This style pump head is meant to direct-mount onto a certain tapered
crankshaft tail normally found on gasoline engines - which you are NOT
going to find on regular electric motors. The pump impeller has the
female of the tapered shaft with the lockbolt, and the tolerances when
it's all bolted together is critical.
Pool pumps and stationary pressure pumps are built to bolt to a
standard C-face pump duty motor with straight keyway shaft, not these.
If you search, you can probably find a semi-trash style pump made for
an electric drive - just like you can find prerssure washer pumps
built both ways.
If you really want to go electric with that particular pump head,
you need a pedestal adapter for the pump. It has the proper tapered
shaft with center bolt, a pedestal in the middle with two shaft
support bearings and and bolting face at one end to mount the pump, a
mounting foot built into the casting, and the other shaft end has a
straight shaft with keyway to mount a standard drive pulley or a
Thern you vary the pulley ratios to drop the speed a bit from the
3,450 RPM of the electric motor to the ~2,400 RPM that the pump head
--<< Bruce >>--
Not really, we have run these small engines on a legitimate dyno at one
of the major lawnmower mfg facilities. (They paint their stuff red) The
engines tend to put out less than the engine mfg lists: something like
95% of the nameplate number down to not much over 50%
But the real reason you need a larger gas engine than electric is that
the gas engine has no additional torque capability, an electric motor
does. A 20% overload for 1 second will kill a gas engine cold. Same
overload on an electric motor will cause a surge in input power, not
I'd expect ANY pump in this class to be set up for 3600 rpm. It's the
standard speed for both gas and electric motors.
The OP listing clearly states "3/4 inch straight shaft with keyway"
A lot of work with no benefit.
It has the proper tapered
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