I need some help figuring out how to plumb a post pounder on my Bobcat. My initial thought is to plumb the return line directly into the filler cap - i bought a second cap and was hoping to pop an iron pipe fitting through it. Just don't want to break something if that's a bad idea I have a 2004ish(not sure exactly) Bobcat S300 that I am trying to hook up to my Black Cat Post Pounder. The post pounder is very similar in design to a Shaver post driver - it effectively has a low-ish gpm requirement (10-12), that actuates a single cylinder. That cylinder raises a large weight, which drops down on top of the post. When the weight drops on the post, all of the hydraulic fluid needs to be returned to the hydraulic reservoir quickly and without restriction. When I use the post pounder with my tractor, the return line is plumbed directly to the hydraulic tank so that it dumps fluid directly into the tank without any restrictions. My S300 has 3 hydraulic connections on the front. I plumbed the driver so that the return line goes to both male adapters - I assume one is the case drain (middle one) and the other is the high flow return (top one). The issue is I am getting some restriction, causing the cylinder to drop slow-ish. The fluid doesn't return fast enough to effectively pound the post. Has anyone plumbed something similar successfully? Can I connect the return line directly to the fill cap on the hydraulic tank? The fill cap vents the tank, so would doing this cause pressure buildup? Or introduce too much air to the tank? I don't want to break anything and was hoping someone who has successfully done this could comment. Or at least tell me what not to do!
Ok, this is very weirdish. I sounds to me like you're trying to make an attachment work on a skid steer that wasn't designed for a skiddy. Yes, the (small) center coupling at your coupling manifold is a case drain, but a small line, so it's a no go for this. And yes, you're going to get restriction on return of that attachment as the Bobcat plumbing for the aux goes through the control valve for both aux couplings, that will be restrictive for rapid release of oil from a cylinder. As for direct connect to hyd reservoir, only way you can do that is a port in the reservoir that is below the fluid level. For example, connecting by modification to the fill cap, that's going to inject rapid flow of oil back into the reservoir through an air space. When that oil hits the fluid in the tank it will aerate it, won't take long you'll have a tank full of bubbles, not good. I don't know what your finances are like, but it would be better to obtain a post pounder that's designed for a skiddy if you can do that.
Thank you so much for the response. This post pounder was designed for a skid steer/tractor, and was being used on a skid steer by the guy I bought it from. He didn't have the flow issue - and I didn't until I went to hook it up on my skid steer (worked perfectly on the tractor). I'm not able to buy another post pounder right now. This one has to do the work, unfortunately. I thought that was the case drain, but wasn't positive - and yes, it is very small. This makes sense - and is exactly what I was afraid of. Is there a way for me to tap into the reservoir below to fill level without causing myself a massive headache? My first thought would be to just attach a tube (old hydraulic hose or something) through a modified hydraulic fluid cap so that the hydraulic fluid dumps into the bottom of the reservoir. I would measure first, but I imagine about 30" should be sufficient. If the tube dispenses below the fill line, it should prevent introduction of air. But it also seems to be like someone has definitely figured out a better way than this. And I'm afraid of doing something that will damage my bobcat.
I'm not familiar with the S300 hydraulic reservoir, but it's likely there's plug, possible SAE O-ring boss plug, that you could remove and rig up a return pipe back into the tank fluid. But that still leaves an operation problem in my head. Bobcat, thumb switch on right drive lever controls aux. Move thumb switch to operate cylinder to lift weight. And then what, thumb switch the opposite direction to retract cylinder (drop weight). That thumb switch is working the control valve, both directions, two way hydraulics. That's where I'm stuck, how are you going to operate the aux hydraulics, two way hydraulics, controlled by the thumb switch controlling the 4 way control valve and somehow route one of those pipes without going through the control valve since the control valve IS the aux hydraulics? I'm really puzzled here how you're going to do that.
I lifted the cab to look at it earlier today. I'll lift it again tomorrow to see if I have any easy plumbing options - or see any plugs/ports. The right thumb switch controls aux, but I am going to control it remotely (like you would with a backhoe attachment). Trigger switch turns hydraulics on permanently while you are outside of the cab. You lift seat bar, hit aux button, pull right trigger - and you can exit the cab and control hydraulics from outside. So only one way hydraulics because of this. Which may complicate things. If only there was a way to dump the hydraulic fluid back into the reservoir from the dump line without any flow restrictions - and without introducing air. I'm determined to figure it out. Lol
How many gallons? What about an accumulator?
Do you have a picture of your setup? I thought the Black Cat drivers were the style with the tall mast and drop weight, unlike a Shaver with the H-beam and springs? The new Shaver skid steer drivers are indeed using one of the main hydraulic lines + the case drain line to get enough return flow, and still I'm skeptical. They are taking the big 3/4" return line and splitting it into the 5/8 (or maybe 1/2?) main line and 3/8 case drain. The one thing those drivers have that would help is that in addition to the weight they also use spring pressure to accelerate the weight, and that may be forcing the oil back, unlike yours which I assume is 100% gravity. As for dumping it directly into the tank, I have an older Shaver HD10 that we use on a Case 1845C and it has the big 1" return line dumping directly into the fill port. Never noticed any problem with it aerating the oil and we driven 10's of thousands of posts with it. You'll need to also make sure that either there is enough room in your setup for the air to escape around the return hose, or if it is sealed tight that you have a good, large breather vent on the tank. The large volume of oil returning so quickly will create a lot of air pressure in the tank. The safest, but most expensive option, is to mount an auxiliary 5-10 gal tank and pump on the diver itself. In that setup the skid steer hydraulics are just continuously running a pump which feeds the driver, and the oil dumps back into that tank. Completely isolates the skid steer hydraulics from the driver and no worries about return lines, etc.
Can you bypass the skid steers hydraulics altogether ? Use the skid steer hydraulics to spin a orbit motor running a pump. Fabricate the new tank, pump & motor and hang it all on the attachment.
I can’t see how you could damage the Bobcat with what you will be doing. I would try and have the return go at least 5” below the hydraulic level in the tank. If you find that your aeration is too much, you could go lower. If don’t think you will have a problem.
You are spot on with what my driver looks like vs a shaver. The only difference is the Shaver has that spring to assist with the return. Mine is entirely gravity. Mine uses the case drain and the main return line. And it is not sufficient. That is what I was thinking about doing in regards to what you have on your case. I just don't want to break anything in the process. Funds are tight at the moment, so can't really make an aux pump setup work unless I could figure it out for 1 to $200. Thank you for the response. I bought a spare cap and was going to effectively plumb the return line through the cap and have a spare hydraulic hose going down through the fill hose about halfway into the hydraulic tank to reduce splash and air introduction.
I have seen setups like that with similar drivers, so I could definitely do it. I'm just afraid of the budget getting out of control if I start doing something like that.
Amazing! That's exactly what I'm going to do. I'll update the post when I figure out of it works/doesn't.
Biggest problem I ran into on my setup is keeping the hose in the tank, allowing enough air to escape, and not letting dirt/water in. Its always been an issue with this type of return setup, whether its on a tractor or skid steer. Be sure the hose is well attached, I used to just use some hose clamps and wire to hold it in but on a couple occasions it came loose. Since its constantly running it pumped the entire contents of the hydraulic tank onto the ground before I realized it, took less than a minute. I've been running various types of post drivers on tractors and skid steers for 20-25years and have never had a problem with oil aeration (knock on wood.) Almost all of them just dump the oil right in the fill port, not below the oil level. Not saying it couldn't be a problem on some applications or maybe I've just been lucky, IDK.
Thank you for the response! I'm super glad to hear someone else has done what I'm planning to do. Makes me at least more comfortable knowing my skid steer won't instantly implode. Lol I bought some iron pipe fittings and a new off brand hydraulic filler cap. I'm going to pop a hole in the cap, and secure the fittings through the hole. Based on your advice, I'll make sure there is plenty of air flow around that as well. I might have to pop some additional smaller holes and throw a foam cover on it or something to keep dirt etc out. Once I figure it out, I'll update this thread so that someone can search for it in the future.
That’s a good idea. I would be tempted to install a NPT down pipe to a 90 degree king nipple and clamp the return to the king nipple and drill some 1/4“ to 3/8” air holes around the king nipple. Covering it with something that allows rapid air escape and dirt out would be a great idea also. Good luck.