Backhoe Design Ideas

[dfkrug]

I guess that answers my next question. I have two 3" cylinders for the swing. I was wondering whether to plumb them as single acting or double acting. Double acting has a lot more force and may be smoother, but single acting requires less flow (i.e. Faster). If swing speed is frequently an issue with these smaller hoes, then I will plumb them as dual acting cylinders. I suppose that worst case I can always go back in and plumb them single acting later if I want more swing speed.

If you are going to use two 3" cyls, they will swing your boom slower than
smaller cyls, if the geometries are the same. Slower is better here. DA cyls
will give more force, when one pushes at the same time as the other pulls,
but they will be slower as you said. Weak boom swing is a complaint for
many of these small attachments as the moment arms used to attach to is
short. 3" is quite big for swing cyls....you don't usually see them on hoes
smaller than 10'. They DO give the best of 2 worlds...lower speed and more
force. Some hoes with 2 swing cyls, go "over center" when fully swung to
either side, which is self-cushioning at these extremes.

 

[Iplayfarmer]

How big is the return hose fitting? Not sure that's gonna flow enough oil? Nothing to loose for that price. Only one way to find out, if it doesn't work swap out for another. No big deal in the end.

Certain there is someone on this forum who would know something about that pump.

Good luck,
Joel

I don't know anything about it other than what it said in the e-bay listing. I do know that the WC is about a 20 HP tractor, so it should be compatible with my little 1215.

I should have the pump in a week. When I get it I'll post some more details. I'm hoping someone here on the forum will have some details about flow and pressure for me. That would help a lot.

 

[charlz]

Weak boom swing is a complaint for
many of these small attachments as the moment arms used to attach to is
short.

Yep. I repacked my swing cylinders a few months back and they are better but the swing is weak. There are times like back filling in a tight spot where being able to push dirt sideways back into the hole using swing would be nice... but it doesn't push much. My hoe has two SA 2" cylinders for swing.

99.9% of your swing is used while digging though so I think speed out weighs strength if you can't have both.

 

[dfkrug]

99.9% of your swing is used while digging though so I think speed out weighs strength if you can't have both.

The same short moment arm used by the swing cyl(s) give you weak force
as well as high speed. Both are undesirable, but the moment arms are
short in order to get a full 180-deg swing. I am not aware of any hoe
attachments commercially avaliable that give you less than 180-deg of
swing, except for the Chinese hoes. The old Woods hoes (and old Kubota)
used a single cyl and complex bicycle chain arrangement to get the 180-deg
at the expense of weak swing and complexity. Believe it or not, my
CADDigger 728 had a stronger swing force with only one cyl (3") vs my
current 2-cyl Woods 7500 clone (2"). The moment arm was larger for the
728, but the swing was only about 120-deg. I also broke the cyl
connection once as the design was inadequate, even at 1500psi.

 

[Iplayfarmer]

Yep. I repacked my swing cylinders a few months back and they are better but the swing is weak. There are times like back filling in a tight spot where being able to push dirt sideways back into the hole using swing would be nice... but it doesn't push much. My hoe has two SA 2" cylinders for swing.

99.9% of your swing is used while digging though so I think speed out weighs strength if you can't have both.

I have figured that with both cylinders plumbed Double Acting I can make a full 180 degree swing in 4.5 seconds running off the tractor hydraulics. That should be fast enough.

If this new pump puts out the 5-7 GPM flow that I'm hoping it does the swing goes down to under 2 seconds. That may be a little too fast. I suppose that I can always idle down until I get the hang of it.

 

[charlz]

I have figured that with both cylinders plumbed Double Acting I can make a full 180 degree swing in 4.5 seconds running off the tractor hydraulics. That should be fast enough.

That sounds pretty slow, especially since you are usually feathering a couple of controls at the same time while coming out of the hole to the spoils pile: swing, boom up and bucket curl.

If this new pump puts out the 5-7 GPM flow that I'm hoping it does the swing goes down to under 2 seconds. That may be a little too fast. I suppose that I can always idle down until I get the hang of it.

That sounds about like mine, I run about 50% or a little more throttle but you can definitely snap the boom around if you are only using swing. I wish I knew how big my dedicated pto pump is. 100% throttle makes everything slam around too much. I only go that high when I am doing some tough digging and want max breakout force.

 

[Iplayfarmer]

Time for another actual design question...

This guy uses brass shims in with his articulated fittings. I've looked up brass shims, and they are not cheap. How important is this little design element, and is there a better alternative?

 

[dfkrug]

I've looked up brass shims, and they are not cheap. How important is this little design element, and is there a better alternative?

I think you mean brass BUSHINGS. Shims are used on some hoes, but I have
only seen them to take up slop in the boom/dipper pivot. I use a couple of
them on my hoe now.

As for the bushings, the CADDigger called for long nylon bushings for the
boom swing pivot, and the two pivots on the boom. Commercially-available
hoes often have pivot insert bushings that are replaceable.

 

[Iplayfarmer]

I think you mean brass BUSHINGS. Shims are used on some hoes, but I have
only seen them to take up slop in the boom/dipper pivot. I use a couple of
them on my hoe now.

As for the bushings, the CADDigger called for long nylon bushings for the
boom swing pivot, and the two pivots on the boom. Commercially-available
hoes often have pivot insert bushings that are replaceable.

He does use bushings, but he's also using shims or washers in between the steel parts of articulated joints. He talks about it a little in videos 22 and 23. I know he goes into more detail on one of the other videos, but I can't find it right now. He's got hours of video on building this backhoe of his. When I went back over the videos I realized he was calling them bronze washers rather than brass washers.

 

[JoelD]

The same short moment arm used by the swing cyl(s) give you weak force
as well as high speed. Both are undesirable, but the moment arms are
short in order to get a full 180-deg swing. I am not aware of any hoe
attachments commercially avaliable that give you less than 180-deg of
swing, except for the Chinese hoes. The old Woods hoes (and old Kubota)
used a single cyl and complex bicycle chain arrangement to get the 180-deg
at the expense of weak swing and complexity. Believe it or not, my
CADDigger 728 had a stronger swing force with only one cyl (3") vs my
current 2-cyl Woods 7500 clone (2"). The moment arm was larger for the
728, but the swing was only about 120-deg. I also broke the cyl
connection once as the design was inadequate, even at 1500psi.

My caddigger side swing was also very strong with a single cyl., stronger than my Kioti 2376.

My Caddigger had a large cyl for the boom than it did for any of the other cyls. Makes a big difference when lifting very heavy rocks and other objects.

If you go to their site you'll see the cyl. dimensions.

One thing for sure, their kits are very strongly built and capable.

Joel