Ok fellas, I need some help wrapping my brain around this one. How does the hydraulic fluid get from the pump to the track motors of an excavator? I had a new guy ask that question today and I had no answer for him. It is something I have never really thought about. Since you have unlimited 360* swings, there are obviously no hoses. I'm lost on this one. Thanks
center swivel ..It's in the center with lots of hoses running into it
center swivel
I'll admit to wondering the same thing..... Didn't some of the older machines run out of swing and engage the track motors to keep turning in the desired direction?
That could get dangerous if you were on top of a pile or something and didn't know you were going to run out of swing, track you right off the top.
Seems like a very good question to me... and after looking at heavylift's photo, I gotta admit... I'm still confused:beatsme
Think of it as 4 grooves in a flat plate with seals that slide on the plate. Each drive has fluid passing through 2 grooves to the lower chassis and out to the drive motors. Each groove carries the fluid for one direction of movement. This allows the machine to move it's tracks regardless of the house position or where the dipper is at. They all rotate around a center pivot shaft and the rotation is driven by slew motor turning a gear that turns the house using a ring gear similar to a starter and a flywheel. When they leak at the seals it is a job to repair.
It's like a bar stool ...top spins...bottom stay put..... the hose are attached to the top.. then the are a bunch of oil grooves and o-rings , bearings. it transfers fluid thru the grooves to the bottom stationary part(while it rotates or stationary) with the various ports exiting the bottom, sends the fluid where it goes....
So the valves for the specific directions are in the under carriage, so all this thing is doing is sending pressurized oil down there, not controlling anything?
I believe I get it now, and the valves are up in teh housing with the rest of the valves, all that they do is control which direction the oil flows into and out of the final drives... which are basically hydraulic motors.
But there are two motors, so wouldn't there need to be 4 lines running down? So that each motor can run independently? I'm still confused.
Does a scenario ever develop in worn out seals where the grooves "short circuit" and erroneous flow pressures develop?
This is how it works as far as I know... You have a rotating and stationary component. The inner upper unit in my example here is attached to the upper structure and rotates with it (Dark grey) while the outer lower unit (light grey) is fixed to the lower structure of the machine. Machined all around the inside diameter of the lower unit are groves that match up with a port from the upper unit. You can have as many circuits as you like going through depending on the size of the rotating assembly... On most excavators it's 5, 2 for each motor and a case drain. On minis you also have the circuit for the blade... Somebody please correct me if I'm wrong but I'm pretty sure this is how it works... Hope it helps.
Thanks for the drawing, I see how it works now. That is actually a brilliant design.
Wow spitzair, helluva good drawing bro! :notworthy And your spot on man, that's pretty much what it looks like inside. And yes ForsytheBros., if the seals fail internally, you would get a "short circuit" effect.
On a tracked machine there is an extra passage for two speed travel making six the normal swivel. There are swivels with even more passages and some with a hollow center for an air swivel and electrical swivel as well. Rough terrain cranes are an example. Really nice drawing!
Thanks for all of the replies fellas. I was still confused until I saw the drawing. The design of those are surprisingly simple yet extremely complex. Thanks again!
Oh jeezzz, don't remind me of that John C. I once had to pull the swivel out of a P&H T300 hydrocrane which have only a lower engine. Four Vickers Vane pumps up front to deliver oil up 4 BIG lines connect to the swivel directly above the front tandem stump. Electrical collector ring hanging off the bottom of it with a bunch of rings. Outriggers were controlled by toggle switches in the upper cab sending voltage to the valves on the lower frame. Then you had power and ground to upper, ignition, start, shutdown, and all the gauges and warning lights. Lastly an air swivel right up the center for the air throttle. That thing was an absolute PITA to work on. On top of bad seals, it also had electrical issues from years of shadetree electrical repairs, so I basically decided to re-do the connections in the collector ring. Had wires hanging down under the machine, a pile of wires. Was off on a field job, returned to find one of the other mechanics had moved the rig. Yep, u-joint yoke on front of the front tandem got a hold of the pile of wire and made holy hell out of it. Like I needed more work to do on that thing. :Banghead
Stupid Question of the Day: Yes, that is a good drawing... :thumbsup And when the seals start to fail, that can equate to weak travel power... And, I need to get ours fixed again , thank you very much... lol OCR...
Ok...what's the story with that?
Great drawing. It was only after i purchased an excavator that i learned this simple yet mysterious design. One small detail left out is how they handle the alignment problem. How do they maintain the precise fit in the hydraulic swivel, while allowing the house a lot more loose play where is connects to the track frame. On my volvo the bottom portion of the swivel is hard mounted to the track frame dead centre in the machine, while the upper portion is only loosely rubber mounted to the house frame. When you swing the body you can see the slop in this connection. Pretty ingenious if you ask me. I wondered about it for years.
like Atco said Cranes are way different,,,, especially the one motored cranes... about the only thing they don't send thru the swivel is water for a heater.... most have the diesel or propane.. can you imagine setting in your car ... and all the functions in the car going thru the swivel.. turn the headlights on...turn signals... gas pedal... brakes.... starting the engine .... forward and reverse.... think of that 6 way power seat and driver 4power window controls as the outrigger and beam controls
Stupid Question of the Day: That's just a "figure of speech"... Cat fixed it once, and it seems to be leaking again... the travel is getting weak. It was nothing pertaining to you... OCR But the edit was...
Drott 40s, 80s and cruise cranes were about the worst I dealt with. The 80 barrel assembly was huge but you had room to work. The 40 was small and could be handled but the electrical and air was a huge pain. The barrels were soft steel and the seals would cut grooves in it. They didn't last but a couple of thousand hours and you had go through all the crap again. Track machines are breeze. I've got a kinship with anyone that had to go through that. Oil running down your sleeves into your armpits, electrical shorts that could be anywhere from the switch in the cab to the starter on the engine and air brakes that didn't work and the operator forgot to tell you that before you went to unload the thing off a low boy. You don't have to fix many of those before you start looking for another way to make a living.
Centrejoints Heres a couple of pics. Up close and personal with my joint haha. No 1 from under the digger, still in-situ. No 2 joint removed from digger. No 3 looking @ bottom of joint. top two fitting go to blade, angled fittings on each side go to respective track motors (forward/reverse) tee fitting on very bottom is case drain from track motors from memory smaller tee @ back of joint was for two speed track. the tee fitting on top of joint one side was case drain from swing motor, the other side was return to tank It's a weighty sucker @ 20 odd kilos. Bit of a struggle trying to hold it in place whilst getting a bolt in it all the while laying on your back with bent arms phew! earned one of these after that effort:drinkup
There is one other hydraulic line that goes to the track motors for the spring applied hydraulically released brake on each motor. When you stop moving, there is a set of spring applied plates that come on to prevent the machine from creeping back and forth while you are digging. When you use the travel pedals, hydraulic pressure is simultaneously applied throught the brake release lines via a shuttle valve to push against the spring applied brake, allowing the travel motors to turn the gearbox. It is considered 'failsafe' because the default is to have the brake locked on if there is a loss of hydraulic pressure to the system. To see this in action, lift up one track with the boom, track to full speed and let off the pedal quickly. The track stops almost instantaneously because the failsafe brake loses hydraulic pressure and the spring take over right away.
Correct me if i am wrong, But i thought i read somewhere that the new bladerunner's were radio controlled :beatsme ? Pj
Tracked machines use travel pressure to release the brakes now days. Basically it takes a couple of hundred pounds of main pressure trying to roll the motor which is teed off to release the brakes. The last separate brake line I saw was on a 40 Drott.
Say for example, a tracked machine quit running. Would this mean that you would have the ability to pull it onto a trailer or to a different location? Or would you have to dismantle the track motors? BTW, this should be noted as Stupid Question of the Day 10-04-09.
I'm gonna take a shot in the dark here and say you'll be pulling the final drives apart. I know a track loader isn't a track hoe, but we had a 963c blow a hydrostatic pump a few years ago in the quarry and had to pull the finals apart so it would free roll (or is it free track:beatsme). took a 988 to pull it off the pile it was on and push it onto the lowboy.
I worked on a Bantam wheeled crane once, similar to the Drott rubber tired excavators, what a nightmare that swivel was! Unless it was in one certain spot you couldn't crank the engine over, luckily it had a seperate crank button on the lower unit, I guess somebody else had problems with it too... Powerjoke, a Radio controlled blade? That's an interesting concept! They'd have to have a valve unit in the lower house and some kind of electrical power supply going down there to make it all work...
I thought there was a pressure release switch somewhere, since I have seen them pulled onto trailers before.
To move a dead machine you have to remove the outside cover on the final and remove the sun gear in the planetary gear set. It only takes a few minutes to do but you will loose all the oil. It's not a dumb question either. I don't know how many times I've had to do that to move burned machines. The people in suits don't know anything about machines but sure do raise cane when they get a bill for services they don't understand.
As long as your sprocket is circular on the inside and not wavy like some models you can just take the bolts out of the sprocket and let it rotate around the final drive. It's not really faster than taking the final drive apart but you dont have to deal with the oil or buy new gaskets. Just make sure the tracks are tight and try not to turn it too much while pulling so you don't run the sprocket off the final drive.
this reminds me of a contractor that bought a mini that we work for. he asked the same question when he bought a used mini and dad looked at him and said well you can only turn them one direction 10 times till the hoses get tangled up and pull the hoses apart. did the guy that sold it to you tell you how many which way it was when you got it??? and he was scared to death for a few minutes till we told the truth
Greetings all thanks for your forum this is the second time i have found the answer to my questions regarding my excavator i have a small Hokuto 300 HD - 2 i find it really handy on my small farm i have had it approx 1 year and have today noticed a tell tale drop of hyd oil following my movements i have tracked it down -- you bet to the swivel it took me longer to find out what it was called thanks to your forum the mystery was solved:notworthy now my quandary begins it is only leaking oil when rhs track is turning the leak seems to be a seal in the top of the unit it seems reasonably straight forward to remove the swivel from below however i am not sure what i will find when removed and perhaps dismantled it seems to be not as complicated as some of the other units discussed in this thread i have some experience with repairing hydraulics and have good engineering workshop with some metal machining equipment without knowledge of availability of spare parts for this make of machine does anyone think that the unit may be serviceable using generic style O rings or is it advisable to take the unit to hyd specialist so far i dont think there is any major damage and hopefully a new set of seals may fix the leak the tracks are both working well ... perhaps i have noticed from the beginning that one was slightly faster than the other but very marginal so from a newbie thanks again for your forum and look forward to your suggestions
Welcome to the forum hokuto. :usa Before you begin your repair, if you've not already done so, you need to identify your fittings and have a sufficient number of appropriate plugs and caps for the hoses you disconnect to keep from making a terrible mess with oil. And before you start, remove the cap from the hyd reseroir as most excavators have a pressureized hyd system, vent off this pressure. Next, take a center punch and mark your hose/fitting connections. Choose a hose as a starting point, punch a single dot on the hose fitting and the matching swivel fitting. On the next hose fitting, punch two dots, the next three, until you've marked all your fittings. Be sure and note how the swivel is oriented when installed, you don't want to reinstall it and try to decide, "did it mount this way...or turn this way???" The rest is pretty simple to remove swivel. Once you get it on a bench, you'll probably find some sort of retainer ring that holds the swivel assembled, it's usually pretty easy to remove center rotary joint from swivel housing, you occasionally find some deteriorated o-rings that hang things up, but they usually come apart with no real complaints. Again, note how the center rotary joint is oriented in the swivel housing. As for the seals, they vary. Some just use typical o-rings. I have also seen them use seals like crown seals, Hallite seals, TP seals, and even T seals. But you can't fret over being able to obtain seals, because if your swivel is leaking you don't have a choice but to take it apart and see where it takes ya. I can't tell for sure, but it looks like you may have pipe thread fittings in the swivel, but if you have any o-ring boss fittings now is the time to replace those o-rings as well. Good luck and keep us posted.
It is really something to have all this wonderful knowledge available. Atcoequip thanks for your reply your advice is well received i would like very much to make sure i don't make any unnecessary mistakes and your advice reinforces this point i make a point of digitally photographing every thing i pull apart from every concievable angle as well usually i dont need them on reasembly but its a bit of insurance just in case. i have removed some of the controls blocking access and cleaned up everything from the top i have not cracked any hyd lines and am in no hurry to do so until i have made sure i need to with a better view and a clean up i can see the oil seal that appears to be leaking and have noted it in the photo attached i can read the identification numbers on it and wonder that because it doesn't leak that much perhaps i should try replacing it while still in machine and all hyd lines attached? my next step is to video the leak in action and seek your opinion:notworthy the machine is quite old and the previous owner mainly used it to infrequently unload drums from a truck...not a lot of swiveling i imagine.... but now i am using it quite a bit and do a lot of swiveling ....so perhaps this outer seal has had a bit of a fright with all the swiveling and being so old:beatsme it would seem that the unit has 2 extra ports at the top which have blank plus in them i have not checked underneath but i wonder if they could be used for a blade hyd's? :drinkup regards shane
Hmm, hard for me to tell in pic, but looks like a rather unique swivel. That looks like it might be a canned lip seal in the pic. That would not be a pressure seal as much a seal to keep contaminents out of swivel, water and dirt. The pressure seals will be insided at each port ring. Once the oil goes by a failed port seal, it will force by that lip seal. Time for new seals. You may be able to drop the center rotary joint out of the swivel housing, but keep in mind, your going to be leaking oil until and probably while you put it back together, might get a bit messy. Most likely, the two unsued ports on the swivel would be for a unit that has a blade fitted.
Yes atcoequip i agree I was hoping for less suspense but alas i must face reality , it should be done properly now before it causes more damage. In oz we have a saying "suck it and see" you described it as "take it apart and see where it takes ya" I just hope when i do dismantle the unit it has seals that are available my biggest problem is safely elevating the machine enough to get underneath to remove hoses and retaining bolts i think there will be ample room to lift unit up through cab which will be better than dropping it out the bottom:Banghead if i can get the replacement seals it may be time to renew both the hyd oil and filter as i have not done that since i purchased the machine i cannot find either volume or type of oil to refill with....have you any suggestions regarding replacement hyd oil in an older machine like this or tips on the approach to changing the oil ....such as emptying rams etc i will post the video as it does show clearly the leak..... i just have to work out how you tube works:bash regards shane
Sorry about being slow to get back to ya shane, in chatroom right now. Lift one end of tracks with bucket, place 6 x 6 or equivelent blocks under tracks on that end. Swing around, lift opposite end of tracks and place blocks. Now you can get under machine. Can't say for sure about your machine as I've never seen one of that brand, but most swivels work best dropping them out the bottom. Don't mean yours will be that way though. As for the mystery seals, in most cases, you can find appropriate replacements. But in some odd cases, a little machine work and a good seal supplier can come up with alternatives to weird seals. As for oil, who knows. A good quality hyd oil should work fine. I use typical AW hyd oil (Anti Wear), it just depends on the viscosity needed. I use an AW32 in my area. But if your in a hight temp climate, you might want to use AW46. It would be good to get some input from other Aussies; Squizzy, RocksnRoses, or Hendrick, as well as numerous Aussies I'm not thinking of right now. Please do keep us updated.
not at all you have been anything but slow thanks for your help it has given me enough confidence to get on with the job i will keep you informed shane
I have a 690b jd excavator wont start (motor locked up) need to get from there to home on lowboy how do i move this 38000 lbs onto and off trailer
Welcome to the forum kansasssnova. :usa Unless boom is in stowed position and bucket is off the ground, your in a world of hurt. If it is stowed, only thing you can do is remove the drive motors from the planetary drives and use other machines to move the dead beast. Not going to be a fast/easy project.
Is there any reason you can't take a small portable hydraulic pump (jaws of life type)and tie it into the system in place of the factory pumps? It would be painfully slow to operate, but I can't see why it wouldn't work. Anyone have thoughts on this?:beatsme
Great idea in theory but in reality plumbing into a lifting ram is probably all that would be practical...opening off the other side of the rams and leave the excess oil drain into something. Easiest fix with a dead duck is lift the dipper off and dismantle the final drives im afraid
Pleased to inform you all that on removal and dismantle all went well. as can be seen in the accompanying photos its a fairly straight forward design should be no problems getting the correct o rings and single cup seal my only query is that the top end of cylinder bore does have some wear being the result of sand etc getting past cup seal and wearing the bearing surface and o ring hence the oil leak i plan to lightly hone the bore hoping the new o rings can cope with that being done to prevent this happening in the future i will fit a plastic disc to try and keep some of the muck from sitting on top of the cup seal it seems to be a flaw in the design any suggestions would be gladly accepted:drinkup
Excallent idea! Hello. I really do like your idea of a bit of plastic to keep the crud out. And, the worst design for a swivel has to be the older gradalls. I do dearly love operating that machine, but some of its design makes one wonder. :Banghead
I imagine that when the center is fitted with its new o rings it will take considerable force to insert it into the cylinder ! would it be best done in a press? Apart from lubricating with some hyd oil is there any other suggestions on reassembly?
Looks good hokuto. As long as the groove worn in it isn't too deep, it should seal just fine for ya with a little polishing. Any good assembly grease will do when fitting together. I use Loctite Viper Lube. I've also used Lubriplate 105 assembling seals. You don't want to use a press to put it together if you can help it. A press takes away the "feel" of fitting the o-rings. They're usually not too bad to fit together. One thing you can do is heat up the outer housing in a pot of water on a hot plate or stove. Don't really have to get to boiling temp, but warming it up will make it expand. Pull it out of the pot of water, wipe dry, apply assembly grease, and slip it onto the center joint with o-rings. Should work ok for ya.
thanks for the advice i will give that a try regards shane
Further to my task I have all the bits needed to re assemble turned out a little difficult to get the proper o rings most of the suppliers were happy to supply an imperial size o ring which was obviously under the original size finally found company "BSC motion technology" who had experienced staff and supplied the correct metric sized o ring with additional attention to the correct hardness value to boot !! I have honed the cylinder My next quandary is that the finish inside the cylinder is exactly what would suit combustion chamber /ring assembly but i feel it is a little abrasive for the O ring assembly Few years ago i reconditioned a hydraulic ram on my FEL and used the same hone on it and at that time felt the same about the finish on that occasion i decided to try and polish it by various cut and polish / abrasive household cleaner pastes etc so far the ram has stood the test of time and worked fine Do you think it necessary to try and polish this job before assembly? the hone stones are of medium grit nothing too radical but seems to me not quite the effect i am after any suggestions regards shane
Done and dusted job completed last week dug heaps no leaks on and upward thanks for your help
Good to hear ya got it working mate. Sorry I didn't respond to your last post. For a while I quit getting email alterts to threads, then one day, started getting them again. I guess that's when you made your post, must have missed it. :beatsme