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

MossRoad · Jul 2, 2006

Finished up the main boom today. Drilled 1" holes in the ends and welded 1" ID tubing inside. Welded the two sections together. Also cut out and tack welded some bushings onto the pivot box for the main boom to slide in to. Started to rain. No photos today.

Running totals:
Time = 15.0 hrs.
Cost = $218

MossRoad · Jul 5, 2006

Cut the dipper stick to length and started making the brackets that will be welded to each side of the dipper stick to hold it to the boom. Drilled 1" holes in them for the pivot point in the end of the boom.

Running totals:
Time = 17.0 hrs.
Cost = $218

MossRoad · Jul 9, 2006

MossRoad said:
Cut the dipper stick to length and started making the brackets that will be welded to each side of the dipper stick to hold it to the boom. Drilled 1" holes in them for the pivot point in the end of the boom.

Attached the brackets to the dipper stick tonight. I had to put 1/2 inch spacer plates between them and the dipper stick so that they will clear those 1/8" plates that are welded all over that steel tubing I have, AND so that I can put 3/8" bushings on the inside of the plates where the pin goes through. It looks plenty sturdy. It was too dark to take pictures. Will take them later in the week.

I may have to put a counter weight on the end nearest the tractor. There is 10.5' of steel in front of the boom pivot point and there is only 9' behind it. When you add up the steel in the pivot bracket, the hydraulic cylinders, hoses, fittings, bucket and hardware, it will probably be more weight than the wheels, outrriggers, outrigger cylinders, hydraulic valves, hardware, seat and operator. I'll have to see after it is all together.

All I know is that it is HEAVY!!!. I can barely lift the end of the dipper stick when it is pinned to the boom and fully extended. My guess is the boom, dipper stick and brackets weigh close to 250#. Once I put the cylinders, hoses and bucket on it, I'm guessing 450# to 500#.

Now I'm tired and I go to bed.

Running totals:
Time = 18.5 hrs.
Cost = $218

J_J · Jul 10, 2006

J_J said:
David, I don't think I get the full 180. It's more like 80/80, I am thinking about making one side a full 90 degrees. I will just have to switch the turning cylinder to the other side. for working in that direction, or just turn the PT around. Some machines use two cylinders to turn the boom. You will probably have to do some trial and error. I will be out of town for a week , Reunion, etc in S.C.

David, My boom steering looks something like this.

All the lines did not appear on my drawing. The large part is the center of the frame. The bottom smaller piece is the boom. A graphics illustrator , I am not.

MossRoad · Jul 10, 2006

Thanks, J_J. That looks similar to the swing cylinder linkage on my plans.

O.K. Math time. I know you went over this with me once before, but I want to measure twice and cut once, so to speak, so here goes.

On the dipper stick cylinder...

If I attach the cylinder 8" above the pivot point and the dipper is 8" long below the pivot point and the cylinder has 36,000 pounds of force, I should get 36,000 pounds of force because of the equal distances from the pivot point, right?

So if the cylinder remains at the 8" then do I divide 36,000 by the times I add 8" like the following:

dipper = 8" = 1 to 1 = 36,000 pounds of force
dipper = 16" = 1 to 2 = 18,000 pounds of force
dipper = 24" = 1 to 3 = 12,000 pounds of force
dipper = 32" = 1 to 4 = 9,000 pounds of force
dipper = 40" = 1 to 5 = 7,200 pounds of force
dipper = 48" = 1 to 6 = 6,000 pounds of force

Is that correct or is the force cut in half each time I add 8 more inches?

dipper = 8" = 1 to 1 = 36,000 pounds of force
dipper = 16" = 1 to 2 = 18,000 pounds of force
dipper = 24" = 1 to 3 = 9,000 pounds of force
dipper = 32" = 1 to 4 = 4,500 pounds of force
dipper = 40" = 1 to 5 = 2,250 pounds of force
dipper = 48" = 1 to 6 = 1,125 pounds of force

J_J · Jul 10, 2006

David, I believe the top set of numbers is correct.
Say you had a fulcrum point at 1 ft and the load was 36T If you pushed down at the 6 ft point with 6T, you could balance the load of 36T. The ratio would be 6 to 1 Your dipper is doing this in reverse.

MossRoad · Jul 11, 2006

Good. That's the numbers I'm using. It will be 8" above the fulcrum and 48" to the end of the dipper stick. At that point I'll have about 6000# of force. Add to that the length of the bucket and it will be less, but that seems O.K. Also, the bucket curl will have tremendous force. It looks like it will be less than a 3:1 so somewhere better than 12,000#. Bet I can smash some beer cans with that!

Attached is a picture of the dipper on the boom. A lot of that large plate can come off.

MossRoad · Jul 11, 2006

I forgot to mention some specs...

It it 48" from the end of the dipper to the pivot point where the dipper attaches to the boom. When stretched out flat, it is about 9.5' from the end of the dipper stick to the boom swing point back at the frame.

I need to get wheels on it and a ring type hitch on the rear and a hook type hitch for the tractor so I can move it around easier. I also need to get some hydrualics on it and the outriggers. It is getting so I have to take it apart each time I want to move it around. It was about all I could handle lifting it into that position to take that picture last night. But I'm tough!

.... no I'm not.

Running totals:
Time = 20.0 hrs.
Cost = $218

J_J · Jul 11, 2006

MossRoad said:
I forgot to mention some specs...

It it 48" from the end of the dipper to the pivot point where the dipper attaches to the boom. When stretched out flat, it is about 9.5' from the end of the dipper stick to the boom swing point back at the frame.

I need to get wheels on it and a ring type hitch on the rear and a hook type hitch for the tractor so I can move it around easier. I also need to get some hydrualics on it and the outriggers. It is getting so I have to take it apart each time I want to move it around. It was about all I could handle lifting it into that position to take that picture last night. But I'm tough! .... no I'm not.

Running totals:
Time = 20.0 hrs.
Cost = $218

I didn't know that you planned to put wheels on the backhoe. I thought that you would hook it up to a QA plate, so that you could drive up, plug in, and go.

I built mine to hook up to the three point hookup on the front of my 1445. When I park it, I will set the boom on the ground, and drop the out riggers, unhook and drive away.

MossRoad · Jul 11, 2006

I really think it will be too heavy to lift. It is already close to 400# without any hydraulics, bucket, controls, etc.... cantilevered out there in front of the PT I'm pretty sure I will hit pucker point promptly.

I will put wheels on it so that I can tow it around like a trailer and position it. When I put the outriggers down, the wheels will lift up a bit. I'm thinking of putting T's in my main PTO lines in the engine compartment and running them out the rear of the PT. That way I could use it behind or in front of my PT. I'm thinking that if I put too much force on the lift arms, I could damage them, but in the back of the PT, it is just a hitch. The worst I could do is pick up the rear of the tractor. Hopefully, I would notice before damaging anything.

Another reason I want wheels on it is so that if I ever want to make it self powered, I can remove the counterweight, add an engine, hydraulic pump, filter and reservoir and it can be a stand alone unit. If I ever have a job that requires lots of digging and hauling away of the spoils, my daughter could use the PT seperately while I operate the backhoe. Just thinking ahead, in case that ever happens.

Now, what kind of tires to use and how to mount them...

I have an old boat trailer with a stout axle. It takes 14" car rims, so that may be the donor. I don't need a suspension on it. I could probably attach that under the cross piece of the main frame and have the outrigger go out at angles to clear the tires. Only problem is I want to keep it as narrow as possible for tight space maneuvering. I will experiment to see what works best. Perhaps smaller tires underneath the frame instead of outside the frame. I just want to be sure the tires have enough float so they can go over soft ground without digging in. Lots to think about, but I will probably temp the boat trailer axle on it just so I can move the darn thing around.