converting a 3-pt concrete mixer from PTO to hydraulic drive

[dfkrug]

Was there some reason you took the hyd motor apart?

Thx, JJ.

Two reasons: I wanted to see how it was made inside. And, though I
bought this as new and the ports were protected, it was not from a
regular dealer like SurplusCntr, so I want to check for cruddy old hyd oil
inside. A lot of used hyd stuff (cyls, pumps, etc) has dirty oil in it, often
due to it sitting around unprotected. If you do buy used hyd stuff, you
can see what kind of life it had by looking inside. I don't have a lot of
good luck to report with used hyd stuff. How about you?

 

[J_J]

Yep, I have purchased motors off Ebay that had Styrofoam beads in them and cylinders with out plugs. The caution here is about taking things apart and stretching the o-ring, and no parts locally available . Sometimes you will get rebuilt and don't know it.

I have a small cement mixer, and just might do what you did. I plan to put a pulley on the hyd motor, and attach it on the side, so I can put it back like it was in case the tractor won't run.

 

[dfkrug]

Speaking of putting the mixer back to PTO drive, here is the drive
spindle and drive sprocket. There are inner and outer ball bearings and
a zerk for grease. In this photo, you can see that the sprocket is
somewhat worn from use. I should have put chain lube on it more
frequently, which required removal of the cover plate.

I don't plan to go back to PTO drive, but ideally, the drive sprocket
should have less teeth so the drum would turn slower at idle.

 

[jim_wilson]

Resurrecting from the dead.............


Either one of you guys been using your converted mixers much? How have they been working out?

I just picked up a used Mixer 80 tonite I found on a bankruptcy auction for $450 - and I want to try and convert it to mount on the FEL on my B3200. I think my biggest hurdle is just figuring out the right hydraulic motor to use on it.

 

[dfkrug]

Either one of you guys been using your converted mixers much? How have they been working out?

I have not used mine in a year or 2. I do plan to pour some concrete within the next year, and I lean toward
the zero-slump mixes I have used the last couple of times. Tamped into place with 1.5" aggregate.

One modification to consider: removing the existing mixing bars, and going with plates welded to the inside
of the drum. This way, reversing the drum will help to eject the mix. I have not done that (yet).

 

[jim_wilson]

I have not used mine in a year or 2. I do plan to pour some concrete within the next year, and I lean toward
the zero-slump mixes I have used the last couple of times. Tamped into place with 1.5" aggregate.

One modification to consider: removing the existing mixing bars, and going with plates welded to the inside
of the drum. This way, reversing the drum will help to eject the mix. I have not done that (yet).

Thanks - I was actually thinking the same thing (welding or bolting in plates instead of the mixing bars that is).

I think the biggest hurdle I have in converting this over to hydraulic drive is figuring out what hydraulic motor to use on it.

 

[dfkrug]

I think the biggest hurdle I have in converting this over to hydraulic drive is figuring out what
hydraulic motor to use on it.

The Charlynn motor I used, and the equivalents, are fairly inexpensive. To get one big enough to go direct drive would be too expensive. Cheaper motors are lower displacement, and would run too fast direct drive.

If I did mine over, I would probably use one less tooth on the drive sprocket for a bit slower speed.

 

[jim_wilson]

The Charlynn motor I used, and the equivalents, are fairly inexpensive. To get one big enough to go direct drive would be too expensive. Cheaper motors are lower displacement, and would run too fast direct drive.

If I did mine over, I would probably use one less tooth on the drive sprocket for a bit slower speed.

Yeah - that's pretty much what I'm seeing. I've looked around and any hydraulic motor that will spin at ~ 540 rpm (so I can hook it up direct drive) - is pretty expensive. All of the cheaper motors of lower displacement run way too fast for a direct drive.

Is there a formula to figure out how to size a motor based on pressure and flow to get a certain RPM out of it? I know the flow of my tractor is about 6.5 GPM for the accessories (steering is separate) - and if I remember correctly the pressure is about 2000 psi.

What I'd like to do is be able to just bolt the motor on with as few changes as possible.

 

[J_J]

Could you not use this motor as a direct drive?

It can flow 16 GPM, at an rpm of 740, but if you run it at half the GPM, say 8 GPM, your speed will be about 389 rpm.

Just put an external relief valve across the motor and set it at 1840 psi.

The pressure will be dependent on the load.

4.75 cu in DYNAMIC BMPH80H2KP HYD MOTOR

 

[dfkrug]

Is there a formula to figure out how to size a motor based on pressure and flow to get a
certain RPM out of it? I know the flow of my tractor is about 6.5 GPM for the accessories (steering is separate) - and if
I remember correctly the pressure is about 2000 psi.

You can calculate the RPM you are going to get, knowing your flow rate and the motor displacement. Or you can
just use the SurplusCnter motor app.

Pressure is not important for a hyd mixer, as it does not take much to turn the drum. However, it would be
great to have a drum spin at as little as 30RPM. 60RPM is plenty fast at the upper end. That rules out direct
drive, unless you get a gigantic motor. If your slowest speed is too fast, low-slump mud will just adhere to
the inside of the drum, without any mixing action. BTDT.

Because the power required to turn the drum is so low, you can run the tractor at barely over idle speed without
bogging then engine. This would give you about 1/3 of your rated flow, perhaps 2.2 GPM. Count the spocket teeth
and buy a drive sprocket that gives you the reduction ratio you want.