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.