1986 Bobcat 743 - Hydraulic stalls when using an auger

[Chessie]

I have a 1986 Bobcat 743 that I bought with a root grapple. It works great, even if the grapple arms move slowly.

I bought a new auger. I tried to drill a large hole (18 or 20" in diameter) to a depth of about 4 feet. When I'm pushing down on the boom, I'm able to stall the auger and stop it from spinning. I upped the RPM's and can get a little more out of it, but it can bog down. I'm able to reverse and/or lift the auger out of the hole, but when the auger stops spinning, there is a noise (presumably the hydraulic oil under pressure... bypassing? )

There are a pair of hitch balls on this unit. Apparently it was used as a backhoe before (?). Maybe it's worn out?

Is there an adjustment on the relief valve? Is the relief valve easy to replace? Is there something else that I should look at?

Thank you, Chessie

 

[Wayne440]

There is more to properly using an auger attachment than many people realize. Buying the first attachment you find, sticking a big auger on it and expecting it to punch a hole in one step like you see in advertising videos is more often than not a route to disappointment. I would expect to remove and clear the auger several times before reaching 4 feet, unless the soil conditions are perfect and the auger attachment is a low RPM, high torque model.

Meaning no offense, I have some questions and opinions.

(1) have you used a skid steer auger attachment before?

(2) do you know the flow and RPM ratings of your attachment?

(3) how long do you expect it to take to drill a 20 inch hole 4 feet deep? (that is removing roughly .3 cubic yard of material)

(4) the relief valve is probably doing just what it is supposed to. Adjusting the valve is probably not the solution- adjusting whatever action or condition causes the valve to operate is usually more appropriate.

(5) my machine has the backhoe mounts on it as well. I don't consider that a sign that it is worn out. That is as unreasonable as saying "someone probably used an auger on this machine, maybe it is worn out". The machine supplies hydraulic pressure and flow to whatever is attached, other than operator abuse, what that attachment is doesn't make much difference. (the exception might be a hydraulic hammer).

 

[Chessie]

There is more to properly using an auger attachment than many people realize. Buying the first attachment you find, sticking a big auger on it and expecting it to punch a hole in one step like you see in advertising videos is more often than not a route to disappointment. I would expect to remove and clear the auger several times before reaching 4 feet, unless the soil conditions are perfect and the auger attachment is a low RPM, high torque model.

Meaning no offense, I have some questions and opinions.

(1) have you used a skid steer auger attachment before?

(2) do you know the flow and RPM ratings of your attachment?

(3) how long do you expect it to take to drill a 20 inch hole 4 feet deep? (that is removing roughly .3 cubic yard of material)

(4) the relief valve is probably doing just what it is supposed to. Adjusting the valve is probably not the solution- adjusting whatever action or condition causes the valve to operate is usually more appropriate.

(5) my machine has the backhoe mounts on it as well. I don't consider that a sign that it is worn out. That is as unreasonable as saying "someone probably used an auger on this machine, maybe it is worn out". The machine supplies hydraulic pressure and flow to whatever is attached, other than operator abuse, what that attachment is doesn't make much difference. (the exception might be a hydraulic hammer).

Wayne440...

I appreciate the reply/thoughts/questions... Here are some answers:

1) I've used a Bobcat "tool cat" with a big (transplant) auger on it. That was probably a more powerful machine with higher-flow hydraulics, just because of how it operated. I'm sure that the Bobcat Toolcat was newer than this '86, Model 743 with a 36 hp kubota.

2) No, unfortunately I do not, I bought it new, but from auction.

3) I don't have expectations, and would be happy to sit and watch it... if it take a full 60 seconds, I'm okay with that.

4) Okay, can live with that. I haven't put any "high-flow" (or other than the grapple) attachments on my machine, so maybe it's just fine.

5) I don't know that it's worn out, I was just trying to add full information. I bought it used. It's a good machine, no leaks, likes to run and has lots of power in the wheels and lift, so I know that the hydraulics are good.

It may be exactly as you said, that I'm trying to do too much too quickly, I figured it couldn't hurt to ask.

I bought this attachment planning to drill holes for a shop/pole-barn and a couple of porches... I plan to drill down, clear the holes and pour concrete into the bottom and into "sono-tubes" (heavy round cardboard forms for pouring concrete.... https://www.sonotube.com/sonotubeconcreteforms.aspx) and then attach building supports on these.

If it's normal for a small machine like mine to drill such a hole in three or four stages, lifting out and clearing the hole and then continuing down, then I can certainly live with that. I appreciate the thoughts/comments.

Chessie

 

[Wayne440]

Based on your answers, I will venture a guess that there is nothing wrong with your 743, and that maybe the auger attachment is not ideal for your machine. But it will work and still be immeasurably superior to digging holes by hand - my limited experience is that it is normal to remove and clear the auger several times when drilling a 4 foot deep hole.

 

[ddbackhoe]

I have a 1986 Bobcat 743 that I bought with a root grapple. It works great, even if the grapple arms move slowly.

I bought a new auger. I tried to drill a large hole (18 or 20" in diameter) to a depth of about 4 feet. When I'm pushing down on the boom, I'm able to stall the auger and stop it from spinning. I upped the RPM's and can get a little more out of it, but it can bog down. I'm able to reverse and/or lift the auger out of the hole, but when the auger stops spinning, there is a noise (presumably the hydraulic oil under pressure... bypassing? )

There are a pair of hitch balls on this unit. Apparently it was used as a backhoe before (?). Maybe it's worn out?

Is there an adjustment on the relief valve? Is the relief valve easy to replace? Is there something else that I should look at?

Thank you, Chessie

Any idea if its a planetary drive or ? you may just be adding too much down pressure. Does the auger drive have its own relief circuit ( cushion or crossover)?

 

[Chessie]

The head unit does not seem to have its own relief valve. When the auger stalls, it's behind the seat that I hear the hydraulics making a different (bypass?) noise.

The down pressure on the auger is definitely the key (as well as how much dirt is piled up on the auger) to how much it is working and if it stalls.

My plan, going forward, is to exit the hole a few times and to learn to be gentle on the down force....

Tnx

 

[North Idaho Wolfman]

If your grapple is slow and the boom and dump are fast it could be as simple as Bad / Plugged / Faulty quick connectors.
The 743 are a mid flow (11gpm) units, so running normal hydraulic implements can be a bit anemic, there is sub compact models that require a lot less flow that would be suited for what your doing.
Putting a simple pressure guage on a quick connector will give you a quick answer on the health of the pump and the relief valve