Backhoe Build A Backhoe For PT425... It Could Happen

[J_J]

David, This picture is for your consideration. You have to have a certain ratio of push point. pivot point, and dipper stick length. The more length on the short side of the dipper stick the more power you will have at the bucket. The ratio seems to be about 1 to 10. I am not saying that the one I built is correct, but it looks about right.

 

[J_J]

Using a pivot.

With a 1 to 1 ratio, a push of 5000 lbs will give 5000 lbs push.

With a 1 to 10 ratio, a 5000 lb push will give a 500 lb force at the end of the dipper stick.

With a .5 to 10 ratio. the push would be 250 lbs

I believe this is correct.

 

[MossRoad]

The plans call for a dipper stick length of 60". The pivot point is 12" down from the top. So, that is 1 foot on one side of the pivot and 4 feet on the other. So will 1000 pounds of push on the short side give me 250 pounds of push on the long side?

 

[BillCroasmun]

MR,
Maybe I haven't thought this through enough but your example would require more cylinder travel for the same arc.
I think more cylinder travel with less movement in arc would translate to more force. Not sure if this increase is enough to take it beyond it's specs and require any beefing up? /forums/images/graemlins/confused.gif Maybe one of our more engineering capable members can answer that.

I drew this up real quick with the pivot point on the arm (red line represents the radius of arc) as well as offset (blue line) to show how the radius increases with the second design.

 

[MossRoad]

Yes, I unserstand that, too. Good points from everyone so far. As for beefing it up, this this is pretty beefy for a PT425. /forums/images/graemlins/wink.gif

 

[MossRoad]

J_J,
How thick is the steel on those plates attached to the tubes?

 

[J_J]

Those plates are 1/4, with support bushings around the holes.

 

[MossRoad]

Good. I have 16 pieces of 1/4 inch plate that may work just right if I need to make similar brackets.

I was looking at hydraulic cylinder lengths this morning(I was also dreaming about the linkage for the boom-to-dipper stick last night, YIKES!) in the Northern catalog. The plans call for 16" stroke cylinders. The Prince brand are something like 31" closed distance between pins. The LION brand is close to 26" closed distance between pins. That's almost 5 inches shorter for the same stroke cylinder. Both are rated at 3000PSI. The Prince brand rod is 1-3/8" The LION brand rod is 1-1/2". Any ideas why the LION brand is so much shorter than the Prince brand? Any experiences to make you think one is better than the other? I'd like to go with the shorter length, if practical.

 

[J_J]

Welded cylinders are the best, and more compact and they cost more. I am using tie rod cyl on mine just because I got a good deal on them off Ebay. I also cut the rod end fixture off and welded on a cross tube. Some of the cylinders leave 5 or 6 in of rod when closed. I don't know if there is any advantage to that. Just cut off what you don't need. I would say use what you can get and make it work. You may have to adapt the pin holes to get a good fit. You learn a lot by doing. If I built these things for a living, they would get better as time goes by. Beef up every thing you can before assembly.

 

[pajoube]

WOW, I had no idea a hole saw could go through that much metal. Did you have to use allot of oil?
PJ