[matt167]

Another question.. being the HF pumps are single stage reed valve pumps, can they run continuous or do they need to shut down?.. reason I ask is I found the right unloader valve and kickdown, and the right size pulley to obtain just under the 1,100 RPM. But also found a centrifugal clutch with the right size pulley. with a regular gas unloader valve, I'm not sure how to make the pump unloaded for starting if I went that route. the diamater pulley I need is 3.67" calculated, and the cent clutch is 3.7", so it should be very close to perfect..
I'd like to go with the $8 pulley if I can tho. clutch is 10 times more money

[cobalt327]

Several unloaders here that are not dependant on the pressure switch- http://www.airtekltd.com/valves.htm

I'm not sure why you would have the compressor pump running constantly, but there may be a duty cycle rating- although I don't recall seeing anything like that before. I'd imagine the pump could run continually as long as the temperature wasn't excessive.

When all is said and done, is the engine going to go to an idle after the tank is full, then kick back up to speed when the pressure falls? If that's the case you will need a centrifugal clutch, unless you want to hand crank it every time.

[matt167]

If the pump is belted directly to the engine with no clutch, the pump spins all the time, and normally gas compressors run 2 stage pumps which are designed to do that normally anyway... But both of the HF pumps are single stage reed valve pumps which would normally fully shut down with the electric pressure switch and an unloader..

My setup will use a continuous run unloader designed for gas compressors, and has a port to operate the throttle kickdown.. But I'm not sure if a reed valve pump should continue to spin even at a reduced rate. theres a big diffrence in price between the pulley and the clutch

unloader valve


throttle control


But if it needs to shut down and I use the centfifigul clutch, I don't know how the pump head will unload, unless the vent will fully unload the compressor head.

[cobalt327]

Both of my compressors I have now, and all that I've ever had for that matter, were start and stop, not a continuous run, so you're into an area that I have zero experience. But my gut tells me the pump you have will not want to run continuously. There's no duty rating to it?

Unless I've missed something, the 'Load Genie" will unload the compressor at shut down for an easier restart.

[matt167]

It doesent have any duty rating listed, only that it's recommended to run at 655 RPM or 1/2 of it's max speed under most conditions. I would run it at max speed to get the 10 CFM@ 90 PSI, being it is not going to be used as a main compressor, only when I need more air

[oldred]

Normally driving the pump directly from the engine is the best way to do this and that's why factory gas compressors are set up this way but with that pump doing it that way may be a bad idea. I am about 99.99% sure that type pump is going to be splash lubricated which means it likely will not get enough oil while running in idle so you may be stuck with using a clutch for that reason. Rigging an electric clutch would be best but it can be really tricky to get it to work properly since it has to be synchronized with the engine coming back to speed from idle, if it kicks in too soon the engine can stall and if it kicks in after the engine reaches full speed it can be a really heavy jolt to both the clutch and the engine. A centrifugal clutch will solve that problem, will be cheaper and will be MUCH easier to set up properly. The downside is they tend to not last very long if the compressor is used a lot. Whichever you use you will still need an unloader for the pump and a kick-down actuator for the engine throttle and don't forget the backflow valve in the tank.



Cobalt, just a note about the Genie unloader, all piston compressors electric or gas (well all conventional compressors anyway) require an unloader to reduce starting torque and come from the factory with them already installed. In fact unloader failure is one of the biggest causes of electric compressor motor failure.

[matt167]

Min operating on the pump is 655 RPM, and at the 1,800 RPM idle that the engine is rated for, comes out to 532 RPM so it wont work. looks like a cent clutch is what it has to be. the 1 I found is rated for 13hp, it should last ok on the 6.5-7hp engine. It's smaller than the optimal size, and will run the pump at 864 RPM, but that's splitting the diffrence anyway

http://www.mfgsupply.com/gomini/gomi...ard/h34p3.html

[Soul_Hunter]

with a gas powered compressor you'll probably want it to run continuously when your using it. if you have to start it every time you need more pressure, it will get old very quickly. i know it did for me.

have you thought about getting one off craigs' list?

[matt167]

It will run continuous, just the throttle control will idle the engine during the time it's within the pressure range of the unloader, and with the idle, the clutch will allow the pump to stop as it should being only single stage..

I'v considered buying used on CL, but every one I find that's in the range of what I belive I could build this for ( $350ish ) I find looks like it's been stored outside or just plain abused.

[Soul_Hunter]

i know you were talking about the continuos run time of a reed valved pump, i believe most of them are reed valved and use a slinger for lubrication.
i don't think single or dual stage really matters that much as far as run time goes.
if i can remember, in the next day or so i'll try to pull the module number off the compressor in my work van and look up a break down of the pump.

im not sure if an electric PTO clutch from a lawn tractor will work.
the mower deck belt does slip when you engage the clutch.
on a compressor with such a short belt, there won't be much if any slip.
i guess it could be worth it to try if you can get a used clutch for really cheap. i know new they are not cheap.
you'll need a pretty big pulley on the pump to get the RPM right.

most of them got stuck in the back of a pickup, so they can get to looking pretty bad.
aren't you in New York?
if so, this one may be worth a look, for parts if nothing else.
http://rochester.craigslist.org/tls/2722668044.html

could buying new be an option?
http://www.sears.com/shc/s/p_10153_1...07000P?prdNo=1

to bad you can't run across what this guy did,
http://www.youtube.com/watch?v=UeAzZ3rj7K4

[matt167]

With the 12" pulley on the pump it comes with and the 3" clutch pulley, rpm comes out to 864 RPM, which is below optimal but above reccomended running speed of the pump..

Harbor Freights smaller 212cc gas compressor pump does seem to use there 3 hp pump that they sell for $139, so it may be safe to run it without a clutch.

I'll have to take a run to sears or HF to try to mimmic there setup.. Rochester is quite a drive for me, and for $600, I could buy 1 of the HF 220v electric models and run it with the 5k watt generator

[matt167]

well, HF's small 9 gallon 212cc gas compressor, which looks like a mirror image of the Sears compressor, down to the 212cc engine that looks just like the HF Predator engine. Is definitely a single stage unit, but not the same unit as they sell as a replacement, tho very similar. The exact pump they use is available on Ebay a lot cheaper than the HF pump, but I'm leery of the flywheels on them.

[cobalt327]

Originally Posted by matt167

well, HF's small 9 gallon 212cc gas compressor, which looks like a mirror image of the Sears compressor, down to the 212cc engine that looks just like the HF Predator engine. Is definitely a single stage unit, but not the same unit as they sell as a replacement, tho very similar.

Is the small HF 9 gallon gas compressor made to run constantly or does it have a clutch? I went to the Product Manual link and all they have is the Owners Manual for the engine, nothing on the compressor itself.

I notice the HF 9 gallon 212cc gas compressor engine has a 7 on the side below the 212 cc displacement, as in 7 HP- http://www.harborfreight.com/212-cc-...sor-68140.html. But that is missing from the Predator engine in the manual and on the engines sold separately. I wonder why that is.

[matt167]

from what I have learned about the 212cc clones is that Loncin rates theres as 7hp. Given the difference in displacement that's probably accurate.. as for the manual. it is there, but the link isn't right. take the "eng" part out of the link and the actual manual will come up, sadly doesent give the normal HF parts breakdown. The compressor is direct drive with just a pulley on the engine. 3.5"-4"ish and the pump pulley looks the same dia as the replacement pump they sell.. The unloader valve is also the identical valve I'm wanting to use, with the same 'whip' for the throttle control.

[oldred]

Apparently ,since they have no disengage between the pump/engine (I have never seen a factory compressor built that way) they just use the unloader to vent the pressure and then idle the pump along with the engine. This would have been my first suggestion for the method used but of course the problem is the minimum RPM which I am sure is due to oiling. Just to hazard a guess here I would think maybe that specific pump for the small gas compressor may have a modified lube system allowing for the idle RPM?