Ford 8n bush hogging question

[Tzerambo]

I have an 8n ford and I’m running a 5foot bush hog. It seems to be bogging down in the thicker grass when I run it about 3/4 Throttle. I’ve been running it at full throttle and it seems to be doing fine in first gear. I’m thinking it’s just because the grass it’s pretty thick. Any ideas? I’ll post a video of it and what I’m cutting. Thanks.

 

[plattman]

I ran an 8-N with a 5 ft John Deer 3 point bush hog for years. It worked but fine as a mower but in heavy fescue was going to be 1 st gear and mabey even raise it some to keep going.

 

[Janicholson]

I have an 8n ford and I’m running a 5foot bush hog. It seems to be bogging down in the thicker grass when I run it about 3/4 Throttle. I’ve been running it at full throttle and it seems to be doing fine in first gear. I’m thinking it’s just because the grass it’s pretty thick. Any ideas? I’ll post a video of it and what I’m cutting. Thanks.

Engines in tractors are designed to operate at full throttle when working in tillage, and on the PTO. The PTO speed is usually achieved when running wide open and loaded to maximum (not lugged down). The extra few RPM of wide open is expected in the implement design. Sharp blades, front of blade circle 1/2 inch lower than the rear of that circle (on concrete to measure) will reduce cutting energy. Jim

 

[Russ from MN]

Yes, like Jim says, it's best to run them at full throttle, and use whatever gear you can to maintain that RPM, or close to it. Our JD4600 has 12 speeds, sometimes when in tall grass or brush I use some of the pretty low ones. This year its pretty wet, if it dries up later some of the canary grass will be eye level when driving the tractor, that takes a lot of HP to grind up!

 

[Tzerambo]

Yes, like Jim says, it's best to run them at full throttle, and use whatever gear you can to maintain that RPM, or close to it. Our JD4600 has 12 speeds, sometimes when in tall grass or brush I use some of the pretty low ones. This year it’s pretty wet, if it dries up later some of the canary grass will be eye level when driving the tractor, that takes a lot of HP to grind up!

I’m used to using a 57 hp Massey and it usually runs this bush hog with ease so I’m just not used to this smaller tractor but it’s doing good I just have to be patient with her.

 

[zuhnc]

I run my 51 8N slightly above the indicated 540 PTO rpm speed, with a 5 foot Bush Hog (tm). First gear in heavy grass, second on the lighter stuff. I do have to raise the mower a few inches in heavy, wet grass, such as running across a shallow ditch. The governor should keep the engine speed where it is set, unless very thick, wet grass; that will cause RPM's to drop dramatically, regardless of throttle setting.

1850 RPM, or thereabouts is engine speed for 540 PTO speed. 8N max engine rpm is about 2200 or so. Sharp blades (not sharpened by the rocks encountered here!), and the front about 1/2 - 1" lower than the back, blade height.

Patience is the name of the game! Not a speedy tractor, but will get the job done. zuhnc

 

[docmirror]

I've used my 8N with a 5ft hog and it will bog in real heavy stuff in first. Sharp blades helped quite a bit. Either grind your blades from tip to 20 percent in, or buy new blades. It'll make some difference. Also, you can't run it real low in the front of the brush hog. I set the deck so it's tilted up just a bit. I think that's what's recommended. I moved up to an 860 for faster cut, but the 8N will get the job done.

 

[Jim.ME]

I've used my 8N with a 5ft hog and it will bog in real heavy stuff in first. Sharp blades helped quite a bit. Either grind your blades from tip to 20 percent in, or buy new blades. It'll make some difference. Also, you can't run it real low in the front of the brush hog. I set the deck so it's tilted up just a bit. I think that's what's recommended. I moved up to an 860 for faster cut, but the 8N will get the job done.

The front of a rotary cutter should be lower than the rear of the cutter. Running the front higher than the rear causes the blades to cut twice (actually more like continuously), once high at the front and again at a lower height at the rear as the cutter is moved forward. Running the front lower causes the blades to cut once in the front half of the circle and travel clear of the grass through the rear half of the circle. Having the blades cutting through the complete revolution uses more power than only cutting in half the revolution.

Setting the front 3/4 to 1 inch lower than the rear is a common recommendation in operator's manuals for lower HP requirements and fuel efficiency. Tipping the front up by the same amount increases mulching action due to the double cutting.

 

[BarnyardEngineering]

I have an 8n ford and I’m running a 5foot bush hog. It seems to be bogging down in the thicker grass when I run it about 3/4 Throttle. I’ve been running it at full throttle and it seems to be doing fine in first gear. I’m thinking it’s just because the grass it’s pretty thick. Any ideas? I’ll post a video of it and what I’m cutting. Thanks.

You're doing it right (running at full throttle, that is).

I know you're trying to "baby" it but you're doing both the tractor and the mowing job a disservice. Open 'er up and let 'er eat. The higher speed of the blades will make for a better cut and you're not bogging the tractor down.

 

[docmirror]

The front of a rotary cutter should be lower than the rear of the cutter. Running the front higher than the rear causes the blades to cut twice (actually more like continuously), once high at the front and again at a lower height at the rear as the cutter is moved forward. Running the front lower causes the blades to cut once in the front half of the circle and travel clear of the grass through the rear half of the circle. Having the blades cutting through the complete revolution uses more power than only cutting in half the revolution.

Setting the front 3/4 to 1 inch lower than the rear is a common recommendation in operator's manuals for lower HP requirements and fuel efficiency. Tipping the front up by the same amount increases mulching action due to the double cutting.

Seems I've been doing it wrong. However, my experience was that setting the blade down in the front req more power from the tractor. I think in my case, I was not cutting hardly anything in the front, and all the cutting was done at the back. As I lowered the front while cutting, it sure did slow the tractor down some.

 

[thomm16]

I have a 1955 Ford 640 and sometimes experience the same issue with the engine bogging down in tall grass, but I run the rotary cutter at the recommended 1500rpm on the engine to achieve the 540 rpm pto speed and operate in 1st gear. If I increase the throttle to 1800rpm will that result in greater wear and tear on the cutter's gear box over time, or will it have no effect. I usually run the mower with the back approximately 1" higher than the front.

Mike

 

[Buffalo Pete]

Dull blades on a standard lawn mower make it nearly impossible to cut tall grass. Sharpen them, and you'll sail right thru. As others have said, try sharpening the blades.

 

[Jim.ME]

Seems I've been doing it wrong. However, my experience was that setting the blade down in the front req more power from the tractor. I think in my case, I was not cutting hardly anything in the front, and all the cutting was done at the back. As I lowered the front while cutting, it sure did slow the tractor down some.

Think about the blades rotating. If the front is lower the grass is cut in the front 180 degrees of rotation and the blades will be above the grass at the back. If the back is lower than the front the blades are cutting grass the full 360 rotation. If you were cutting hardly anything at the front and all the cutting was at the back, either the grass was really short, or you were holding the front way to high.

If the back was lower than the front, when you lowered the front you lowered the entire deck, increasing the cut at the rear and possibly dragging the deck runners, which would take more power. Adjusting height on a flat surface, using limiting chains to help keep the front height constant regardless of how one lowers it, and adjusting the tail wheel to set the deck pitch, all go together.

 

[sotxbill]

INSTEAD... of lower the front, raise the back by adjusting the tail wheel one notch down... The the front will be now lower than the rear. The reason for cutting this way is.... when the rear is lower, the front cuts the grass first, and then the rear being lower, has to cut it again, further slowing things down, taking double the power and fouling the path that expels the grass that chokes is more. WHY would you choose to cut it twice?? SO,, you should run level, or with the front slightly lower... But if your cutter is already too low and bogging down, lowering the front more, will only make it worse. 8n is already very low on hp, and the first gear is already too fast as opposed to newer tractors with lower gears... Also running it wide open means your pto rpms is above the recommended design settings and can be hard on the cutter and the tractor. Expect things to run hot and wear faster. SO.. either cut higher and or raise the rear. Dont cut with the rear lower in heavy cutting.

 

[BarnyardEngineering]

I have a 1955 Ford 640 and sometimes experience the same issue with the engine bogging down in tall grass, but I run the rotary cutter at the recommended 1500rpm on the engine to achieve the 540 rpm pto speed and operate in 1st gear. If I increase the throttle to 1800rpm will that result in greater wear and tear on the cutter's gear box over time, or will it have no effect. I usually run the mower with the back approximately 1" higher than the front.

Mike

That extra 300RPM of engine speed is not causing enough additional wear and tear on the tractor or the mower to even bother thinking about. There's no little gnome inside the mower going, "Oh dear, it's turning 541 RPM!" and pressing a self-destruct button!

If you start the mower, set the throttle at 1500RPM, then pull into some grass and start mowing, the tractor's RPMs will be pulled down a few hundred RPM. You need to compensate for that by opening the throttle further.

 

[Butch(OH)]

Once you have the blades sharp and it set front to rear as others have said then run the tractor wide open unless the PTO speed is way over 540.
Sure seems to be lost among most that there is no law that says you must cut a full swath with a bush hog. Simply move over and cut what the tractor will pull in the heavy stuff.

 

[zuhnc]

Just today I cut a couple of swaths with the 8N and a 5' Bush Hog. Front blade height is about 8", back a little higher. 1580 engine RPM, PTO runs at 540. Grass was somewhat damp, due to recent rain, and cutting width was about 4'8" or so. Grass was pretty thick, and about 40" high. Governor maintained speed within 200 RPM, except going across a couple of ditches where I was mowing water and grass. Had to raise the mower a few inches to get through that. The ruler is 40 inches long.

zuhnc