3 point hitch string trimmer, Mark II

[PHPaul]

I posted a topic on the original version here.

The right angle drive I used was VERY used when I got it and didn't like being run upside down, probably due to lube issues. In any event, it failed catastrophically.

I decided to resurrect the project this Spring and got a 30 hp-rated brush hog gearbox from Surplus Center and redesigned the mount and drive belt arrangement.

With a heavier gearbox, mounted as designed and a better PTO shaft with a slip clutch, I think this version should work quite well. String head speed seems a little low but it works okay. I may mess with pulley sizes a little down the road. I left the intermediate shaft long until I was sure I had the pulley alignment right. I'll trim that to length.

 

[texasranger556]

I like it. Do you have a shear bolt or anything to keep from bending if you catch it on something?

 

[PHPaul]

I like it. Do you have a shear bolt or anything to keep from bending if you catch it on something?

No, which may well come back to bite me in the sitter. I run in low gear with one hand on the 3 point hitch lever and lift it up over anything I can't cut.

 

[kthompson]

I like it also. Would be great for our pond or ditches. Not the sides of the ditches but growth coming out the top. I have seen a slip type design which was basically a length of metal inside a sleeve with heavy spring to allow your cutter to swing back if you were to hit something. You also could use a simple sheer pin design if you seldom hit something. Wonder about putting a hinge into the design where you could adjust the cutter head up or down some for cutting on angle.

Please know I do find your design great. Do think you ought to cover the belts to keep what ever is being cut from getting between the pulley and the belt.

 

[PHPaul]

I like it also. Would be great for our pond or ditches. Not the sides of the ditches but growth coming out the top. I have seen a slip type design which was basically a length of metal inside a sleeve with heavy spring to allow your cutter to swing back if you were to hit something. You also could use a simple sheer pin design if you seldom hit something. Wonder about putting a hinge into the design where you could adjust the cutter head up or down some for cutting on angle.

Please know I do find your design great. Do think you ought to cover the belts to keep what ever is being cut from getting between the pulley and the belt.

Thanks!

I do intend to put sheet metal covers over the belts, especially the lower one. I wanted to make sure everything was going to work as-is before doing that.

Being able to tip the string head at an angle to trim down into ditches would be great, but the only way I can see to do that would be a hydraulic motor drive and a cylinder to adjust the angle. That gets into serious money (at least compared to my budget) quickly.

I AM noodling over the idea of putting a top-and-tilt on the tractor which would be more generally useful, especially with my box blade. then I could raise the whole thing up and tilt the string head down at an angle.

I used it for a year in it's original form before the right angle drive died and didn't run into (arrrrr, humor!) a situation where a break-away would've been needed. Doesn't mean I won't in the future of course, but for right now it's not high on the list.

 

[jimmychew]

Great job on the trimmer. What do you use for string, piano wire?

 

[ArlyA]

Looks like regular string trimmer plastic to me. We use the .155 version by the roll but looking to try .170 or 180 which is a bit harder to locate on our whackers. PHpaul do let us know which string you are using and do show its attachment system.

 

[PHPaul]

The string head is off a Craftsman walk-behind trimmer and the string is the heavy plastic with a square cross-section. Not sure what size it is. Edit: I went out and measured it. It's .180 measured on the diagonal.

I cut off a 6' length, cut it in half and thread it like this:

Leaving two approximately 16" pieces on each side to do the cutting.

 

[metalbender]

A surplus 12 volt linear actuator would probably control angles.

 

[TractorGuy]

I've been thinking about building something like this. Might go with swinging blades for a disc mower instead of string.

You don't need a shear bolt on belt driven mowers. Finish mowers don't have one. They depend on belt slip.

 

[somewhereinusa]

What kind of RPM are you shooting for? What would recommended be?

 

[ArlyA]

I'm not sure but will guess you mean this type of swinging mowing blades. But I agree, that stings do not need a shear pin.

I've been thinking about building something like this. Might go with swinging blades for a disc mower instead of string.
You don't need a shear bolt on belt driven mowers. Finish mowers don't have one. They depend on belt slip.

 

[texasranger556]

I don't think anyone was suggesting a shear pin for the driveline. I was asking about something in the frame that would give way before something bent...in the event of daydreaming while driving through a gate, garage door, past a tree, clothesline, wife's brand new car, etc.

 

[kthompson]

PHPaul, I spent many an hour working on a boom mower for my tractor. Mostly in my mind. Ended up finded an old one a friend was going to scrap out so got great price and had cutter head the right size for it. I had to make some linkages for the boom and I used wood to make the test linkage with for test fitting.

To put tilt on your cutter should not be that hard as someone else pointed out. If you are interested take a look at the side mount cutters to see how they are designed. That is how I solved some of my how tos. Might not work, but looking at your pictures the question came to me, could you replace the right lift arm linkage with a cyl to raise and lower the right lift arm? A small amount of movement there would end up being a good bit at the head. It is a neat idea in design.

 

[TractorGuy]

I'm not sure but will guess you mean this type of swinging mowing blades. But I agree, that stings do not need a shear pin.

Yes that is kind of what I was thinking. A mini bush hog of sorts. I have an old 4' Befco finish mower I could use for a gearbox and some other parts.

I was thinking of the disc mower blades they sell at TS for hay mowers. A 6 pack is $9.99 and a pack of the shoulder bolts is $29.99. The blades are available in flat, CCW, or CW configuration.

I have one of those Craftsman walk behind trimmers but I would never cannibalize it for a project like this. I HAVE thought about just drilling a couple of holes in it and mounting the mower on a boom. The heavy trimmer line will last a good long time in any type of grass but it doesn't take much of a stick to break it.

I don't think anyone was suggesting a shear pin for the driveline. I was asking about something in the frame that would give way before something bent...in the event of daydreaming while driving through a gate, garage door, past a tree, clothesline, wife's brand new car, etc.

Ahh okay. I misunderstood the question. Guess you could hinge it at the transfer shaft or something and put a break away pin on the front.