Screw drive garden tractor

[4570Man]

If I ever get around to building one I have all of the hydraulics out of a skid steer that was headed to the scrap yard. You might find the needed hydraulics cheap out of a bobcat at a scrap yard.

 

[GolfAddict]

Well, the project is over for now...thanks for all the great comments and help along the way! love this forum, i spend many hours searching through it there is a wealth of knowledge here!
Here is the finished product: https://youtu.be/FlJE8OheKbo

It really worked pretty good, but the machine you had to work with just wasn't robust enough. It sure was a great project to watch though - thanks for sharing it!!

 

[Xfaxman]

Great project, it was fun while it lasted. :thumbsup:

Now you can convert it to hydraulics.

 

[Rednic79]

If I ever get around to building one I have all of the hydraulics out of a skid steer that was headed to the scrap yard. You might find the needed hydraulics cheap out of a bobcat at a scrap yard.

what's that stuff worth ya think?

 

[4570Man]

what's that stuff worth ya think?

My grandpa needed an engine to go in a man lift, and it was a hard to find motor because of width restrictions. He bought a whole bobcat for $1500. We removed the engine, all hydraulics, the almost new tires, and drained the hydraulic fluid (over 10 gallon). Then he sold the rest for scrap.

 

[Rednic79]

hello again....so i've been making some good progress on my "screw drive" garden tractor. (if you wan to check it out go to my youtube channel "rednic79" or not..hehe) anyhow....i need some help and advise. i want to put shear pins on the ends of the new screws where the sprockets attach to the shafts so that in a total jam up situation, the pin breaks instead of my whole machine (again).... does anyone have any thoughts on what size of pin i should use? should i use a bolt? what grade? etc?
thanks!
Nic

 

[CalG]

The shear pin diameter should be 40% of the shaft diameter to be "just" equal in strength. when the pin and the shaft are made from the same strength material.

You can do the math on "grade 8 " bolts through "mystery metal shafting" if you want.

 

[Fallon]

Grade 5 or 8. The higher the grade, the stronger the bolt, but also the more brittle. You want something that will snap cleanly. A grade 1 or 3 will tend to bend & leave you with a jammed twisted bolt. Also, make sure there is smooth bolt shaft being sheered, not threads. Threads are much weaker & less reliable than the solid shaft.

 

[Rednic79]

The shear pin diameter should be 40% of the shaft diameter to be "just" equal in strength. when the pin and the shaft are made from the same strength material.

You can do the math on "grade 8 " bolts through "mystery metal shafting" if you want.

so... you think I should go with 3/8 on a 1" shaft? will that break the bolt in a jam up?

 

[CalG]

It really depends on what you need to protect. Is it the shaft the pin is fitted to that has failed? Or is there a weaker mechanism somewhere down the line?

But a 3/8ths grade 3 (ungraded) would be a safe start to protect the shaft. maybe even start with 5/16ths. If the soft ones shear to easily, it's easy enough to go grade 5.
And if those fail too easily, redrill for the 3/8ths. and step up through.