Hi Nori,
My gear box is a 1: 1.47 "speed up" rotary cutter gear box, which
means if I'm running at PTO speed of 540 rpm, I'm looking at a blade
speed of about 794 rpm. That's fine if you're cutting air, or grass,
but moving water and cutting paper is considerably more load.
What I discovered is that with about 120 gallons and just 20# of
paper, I had to have my engine up to PTO speed before engaging the
PTO, or it would just stall the engine -- and to put that much torque
into a non-moving mass of water and paper is less than ideal/safe --
better to bring up to speed gradually. My compact tractor has a 37
HP diesel engine, so maybe others with an engine twice the size won't
have this problem. (Nori, how many HP is your tractor?)
With a tow mixer, you have the advantage of just naturally starting
the blade up slowly, and a variety of transmission gears in your tow
vehicle. With a PTO, unless you've got a good-sized tractor, you
have to start up with higher revs -- less than ideal, especially
considering the mass you have to put into motion and mix--and it is
just an ON/OFF proposition.
My blade is a 21" lawn mower blade with an airfoil-like curve
designed to create an updraft -- so this added considerably to the
drag the blade encountered. So I've decided to reduce the load by
cutting down my blade to 12-14", eliminating the updraft curve, and
grinding the blade with a curve so that it will shed chunks it
can't/won't cut (rather than just carrying them wrapped around the
blade). The smaller blade, flatter profile, and "S" curve should
reduce the start-up load and allow me to start up slower and more
gradually crank up the rpm as needed. Stay tuned!
By the way, my 4" gate valve works really nicely so far. I
especially like how I can easily control the flow volume and quickly
shut it off.
Best,
Eric
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