Another Homemade Backhoe

[skidoo]

I was referring to a bracket such as the one in this picture. I don't know the purpose of it. But, I speculate that it provides a means to keep the forces more straight with the piston as the angle of the piston doesn't move much throughout the motion range. I see in your video that the piston moves from parallel to about a 30 deg angle through out the piston range and it does not have such a bracket.

 

[David Devuono]

Mine has that bracket, only instead of being arc shaped, mine is L shaped. It is made 1/2 inch thick and I will be adding an H brace to stabilize it. As well commercal backhoes have like 5,000 PSI and large cylinders so they don't need extra leverage. This piece is to allow the bucket to curl without having a large bracket produding off the back of the bucket. (I think ) Since I have so much stroke available, I made this lever longer then normal to make extra dipper power. Its potentially an expensive mistake if the backhoe does not work but its keeping me out of trouble this winter.

 

[wmgeorge]

Mine has that bracket, only instead of being arc shaped, mine is L shaped. It is made 1/2 inch thick and I will be adding an H brace to stabilize it. As well commercal backhoes have like 5,000 PSI and large cylinders so they don't need extra leverage. This piece is to allow the bucket to curl without having a large bracket produding off the back of the bucket. (I think ) Since I have so much stroke available, I made this lever longer then normal to make extra dipper power. Its potentially an expensive mistake if the backhoe does not work but its keeping me out of trouble this winter.

I found when building my BH, the cylinders were not the major expense, but the steel, bushings, control valve and etc. I don't think I had over $300 in cylinders. I admire you using what you had on hand...but doing the re-design to make them work must be chore. I'm wondering how you will limit the stroke to be only 24 inches out of 36? I think I would have sold the long ones, and purchased ones a more common size for a backhoe.

 

[skidoo]

Well, it sure sounds like you are having a lot of fun!

 

[Renze]

As well commercal backhoes have like 5,000 PSI and large cylinders so they don't need extra leverage. This piece is to allow the bucket to curl without having a large bracket produding off the back of the bucket. (I think ) Since I have so much stroke available, I made this lever longer then normal to make extra dipper power

We use an arm like that on our commercial payloaders for years: as you said it gives extra power where most needed, in other words, gives a constant curl torque over the full bucket motion. If you use bigger cylinders, you will have power where you dont need it (speed loss) when the cylinder is also capable to generate the bucket torque in the less favourable positions of the cylinder vs. hinge points.

Designing mechanisms like this, is allways a lot of fiddling with the geometry if you want to lay out the torque in the curl positions where needed, without slowing the speed so much where torque isnt needed.

 

[Stampeder]

Interesiting project! Looks like you've got it well thought out and you're well on your way.
The question I have is what sort of hydraulic rate pump will you need. I was told these things are pretty hungry when it comes to hydraulic fluid and you need a pump with substantial delivery capacity to run them.
My 50 hp tractor hydraulic pump tops out at 15gpm, so I can't operate the skid steer rotary front mount augers because they take close to 20 gpm.

Keep up the good work.

 

[David Devuono]

I don't see the long stroke as an issue because you should not use the internal stops in the cylinder to limit the cylinder stroke, you should use an external stop. As well a 36" stroke cylinder with 12" inside the cylinder would be more stable then the same dia cylinder with 24" stroke, fully extended, not that there should be much lateral force on the cylinder. As far as pump capacity, I would think that anytime you are using a hydraulic motor, you will require lots of GPM, operating small cylinders require a lot less. My tractor has about 5 gpm at 2300 PSI (+_ on a 40 year old tractor). The previous owner had a FEL on the tractor and it raised the bucket with 2 cylinders at a reasonable speed. Anyway as long as it works faster then a pick and shovel, I will be happy, plus will be safer cause I won't have to be in the hole digging

 

[David Devuono]

Things are progressing. I scored big time when looking for a control unit for the backhoe. Found with the help of a great young hydraulic counter person a discontinued BM40 6 spool for $199.99. Anyways mocked up the backhoe on the weekend and found a few clearance issues that require work. Its getting far too heavy so will cross my fingers I am not making a big pretzel.
I set things up using the built in receiver hitches I have on the back of my trailer.

 

[andymil]

I was referring to a bracket such as the one in this picture. I don't know the purpose of it. But, I speculate that it provides a means to keep the forces more straight with the piston as the angle of the piston doesn't move much throughout the motion range. I see in your video that the piston moves from parallel to about a 30 deg angle through out the piston range and it does not have such a bracket.

These links are part of the four bar linkage that allows the bucket to rotate more than it would if the cylinder rod was attached directly to the bucket. A bucket with links can rotate 180 degrees and have more power as the cylinder reaches full extend or retract.

 

[David Devuono]

After a busy week of late evenings and using up a vacation day I finally got the backhoe together and installed on my tractor. I had fun routing the hoses as I originally planned on 1/4 hose, only to be told I could not go from 1/4 hose to 1/2 without using two adapters, so I went with 3/8 hose. Later the guy fingers out its not 1/2 but ORB 8 and he finds a single adapter. I should have made him redo $600 dollars worth of hoses. Anyway the 3/8 hose is tough to bend and all my hoses were 6" short due to the large bends required. I was able to make do with the short hoses. I also realized that I will have to reroute the exhaust as the old Massey 135 exhausts out the rear. My first project was to dig out a stump and after 20 minutes I realized the frost was still in the ground and I would need a jack hammer so that project will have to wait a few more weeks. I do have to run the tractor at high revs to get the flow needed for cylinder speed. Perhaps a 3ph pump will be in its future? I will post a video in a few days.