What happens if you run a rotary plow on a too-small tractor?

[williaty]

Compatibility limits tend to be written with the stupidest user in mind. We all know that guy who has no mechanical sympathy, no understanding of physics, and who ruins every tool he touches. Sometimes, if you have a lot of caution and care, you can get away with doing things the manufacturer officially recommends against. Sometimes you just blow things up though. I have a BCS 718 tractor and someone local is offering to sell me the rotary plow that fits the BCS line. The 718 is officially too small to use the rotary plow because the 718 makes 6.5hp and the plow's official requirement is 8.5hp. If limited to slowest gear, taken in multiple passes as required, etc has anyone actually used the rotary plow with one of the smaller and less powerful tractors like the 718? If so, what was your experience with trying?

Thanks as always.

 

[WesKootenay]

Hmmm, not sure about this. Maybe a call to EarthTools - I'm sure they must have tried it?
We bought the 732 many years ago as it was the minimum requirement to run a rotary plow. I'm guessing the 718 will run it, just won't be able to dig as deep in one pass. Also, wheel spacing could be an issue? Can you 'try before you buy'?
Good luck.

 

[CobyRupert]

I’m not even sure what a rotary plow is....had to look it up.
... but I do know horsepower is a measurement of speed (a rate).

If machine has the torque (and weight, traction, gearing, etc..) to do the same work but at a slower rate, it doesn’t require as much power.
...if you want to spend the time.

 

[CADplans]

I have run my rotary plow with both a 8HP and a 12HP Gravely,,

(the cultivator is on a 10HP,,)

As far as the rotary plow, I can not tell any difference on how the machine operates,, between 8 and 12 horsepower.

 

[CADplans]

Oh, yea,, I forgot to mention,,
that rotary plow in the pic was originally on a 6.6 HP Gravely.
Gravely never changed the basic design or size of the rotary plow as horsepower increased,,

 

[Popgadget]

I’ve used a rotary plow with a 5hp Gravely L as well as most all subsequent models. My present convertible has a 13hp Honda. I disassembled it and machined the crankshaft to mate to the Gravely transmission. That was about 20 years ago, and it’s still going strong.

 

[Jens767]

Hi williaty

I have been considering whether to reply to your post or not, as I have no experience with the BCS 718 or the Berta Rotary Plow. I have been waiting for someone with the experience that you are asking for to reply, but sadly nobody have done that yet

Your BCS 718 is probably powered by the Honda GX200 engine, which officially is rated at 5.5 hp:

Honda Engines | GX12 4-Stroke Engine | Features, Specs, and Model Info

Berta recommends a minimum of 8 hp to operate their rotary plow, which leaves you 2.5 hp short:

http://bertafranco.com/assets/bertarotaryplough4l.pdf

On top of lacking 2.5 hp, you might also have to small diameter wheels on your tractor - if you have the standard 4x8x16'' wheels of course. As you can see in the link above, Berta recommends 5x10'' rims, which would mean the 5x10x20'' wheels. These wheels are standard on some of the larger BCS models, and might not fit the 718! If they do, you might also need axle extensions in order to reach the inner tire width of 40-42 cm (16-17''), that Berta recommends.

If the 5x10x20'' wheels will fit, the 4'' increase in tire diameter, will increase speed with 4/16x100 = 25%! The 718 will run at a maximum speed of 0.65 mph in first gear with the 16'' wheels, which is very close to the 0.7 mph for the BCS 739 on its 20'' wheels. If you have 20'' wheels on your tractor though, it will drive at least 0.65x1.25 = 0.8 mph, and that with a less powerful engine

As WesKootenay rightly recommends, you could give Joel at Earth Tools a call and ask for his opinion. If he hasn't already tried your combination, he probably could. I guess, that you have already asked your local seller if you can try the plow before buying it?

I look forward to hear your comments, and even more how your tractor performed, if you had the chance to test it with the rotary plow.


Best regards

Jens

 

[williaty]

I don't know if it was good or bad, but the plow sold before I could figure out if I could use it.

 

[Tractor Seabee]

So a rotary plow is really a rototiller. Here I thought I was learning something new.

Ron

 

[williaty]

So a rotary plow is really a rototiller. Here I thought I was learning something new.

Ron

Not exactly. It's more like a post hole auger that you drag sideways through the ground. It pulls dirt up out of the bottom and deposits it beside the row, effectively rolling the round over like a typical moldboard plow.