I work for a small "3 guy" pest control company and the boss asked me spec a custom pesticide sprayer, And since I am the techie mechanically inclined guy, I was filled with gleeful delight

I have a sprayer in my truck now that is a 50gal 5.5hp Briggs and Stratton hooked to a Continental Belton PT-1a gear pump "No longer made" Supposed to be doing  8gal a min at 150psi. The pump was rebuilt the end of this year "Took a month for parts" and ever since I got it back it has dropped from 110psi to 60psi and is not doing what I need it to

So If I can spec and put together a rig custom built for our use for under 3 grand, Myself and the boss would be very happy.

Water/pesticide tanks are easy. The hose reel will be a electric coxreel. Pump I am leaning on is a hypro roller. And I am stuck on what engine to use....

I would love a electric start since this rig will be inside a truck bed with a topper, But keeping cost in mind I can do with a pull start. Been doing it for the last year anyways..

SO you small engine guys... Stick with the briggs? I do hear good things about Hondas. Also I am thinking I will need a gear reduction since the pumps max is 1000rpm and a honda GX120 is up to 3600rpm

Thoughts or input?

The better single cylinder engines these days are Honda and Subaru -- that's pretty much all you'll find on quality commercial/industrial equipment.  

Check out lawnsite.com for info on the rest of the sprayer construction.

ar-jedi

Thanks that site has a lot to look at.

One thing I do not know how to do is size the motor for the pump. How would I do this?

the sprayer will have a specification for input power at a given output flow rate (GPM) and pressure (PSI).  

do not undersize the engine or you'll have a couple of issues, foremost that the pump is going to drag the engine and drastically reduce the engine life.
you can't put a 4cyl car engine in the bay of a semi tractor-tralier, and pull 40tons for 200K miles.

ar-jedi

Honda all the way. I have several Briggs. All get hard to start after some age. Every Honda I've had just fires right up every time.

http://www.delavanagpumps.com/rollerpro/diagram.htm

http://www.delavanagpumps.com/rollerpro/6900.htm

note:
a typical gas engine is governed to run at 3600 RPM maximum; most roller pumps can not spin that fast so you will need a gear reduction or belt drive for the pump.

ar-jedi

Thanks for the links, Its nice to have another option for a pump.

I understand that I will need a gear reduction since the pumps max rpm is 1000. What I was unsure of is how much HP I needed to run the pump.

Example... The hypro 7560 at 540rpm will make 100psi at 12gpm. I cant figure out how much HP I need to run that..

However my pump I have now is/was running at 150psi at 8gpm with a 5.5HP motor, and that worked perfect for what we used it for. I want to push the same or a little more out of the new setup, So I think I should be good with a 5.5 or 6hp motor me thinks...

ETA every pump I look at has nothing stated about the power to run it. Only rpm and flow rates

IMHO, 5.5HP is plenty for a 8GPM 50-100PSI application.  you'll get long life out of the engine.

ps
see
http://www.sprayerdepot.com/Shop-by-Category/Kings-Skid-Sprayers
and
http://www.sprayerdepot.com/Shop-by-Category/Honda-Engines

some of the engines on the 2nd link above are supplied with OEM 6:1 gear reduction.

ar-jedi

That was my thinking also..

Thanks for the reassurance

Will post a build thread just for the hell of it when its done

Wylie's

They do everything from small home owner stuff up to self propelled sprayers.