Where and what kind of hydraulic high pressure gauge that will go up to 3000 pounds should I get? It would be just for my personal use on my marklift Model 62 manlift. And the service manual said to connect it to a high pressure port, but I don't know where I would find the high pressure port. Would it come directly off of the main hydraulic pump? And if so, I don't know how I could get the main hydraulic pump to pressure up and see the gauge while I am operating the ground controls or aerial controls. There is a gage attached to the proportional valve manifold, but I think that is for pilot pressure, which normally runs between 100 and 500 pounds. Picture attached.
My preference is Cat. Seems like the $25 gauges from the hydraulic shops don’t last as long. Cat runs about $65. 8T-0859 is a 3,600 psi gauge. What are you wanting to test? There are different points for different issues.
Not familiar with your machine, but from what I can see in the photo it looks like that gauge may be plumbed into the main supply line for that valve. If so, it would read max pump pressure when one of the functions was dead headed. Oh, and +1 on the Cat gauges.
Picture's not clear but that gauge might be a 6,000 psi gauge so it should do the job. Something about that valve and even the marking on it remind me of the Snorkel lift we had at the quarry. If you want to be able to watch that gauge while working something I'd just pop it off by the quick connect and take it to any good hose shop and tell then you want to have a hose so many feet long installed between the gauge and quick connect. Also ask them if the can supply a new quick connect and the fitting to attach the Cat gauge when you get it. My rule of thumb for gauges is to select one that has a maximum reading of approx twice the pressure you want to read. That gives you a little safety margin if a relief valve is not set right or there is some other problem.
That's a 6,000 PSI gauge. There is also a number four JIC male Tee fitting at the bottom of that plumber's dream below that gauge where you can attach a hose and run it out to where could see it if you didn't want to pay $50 for another quick coupler.
Thanks everyone! Cmark so if that gauge is plumbed into the main supply, then it would be showing the pilot pressure when a function is not engaged, correct? What does Deadhead mean? Would that be for example if you keep the control lever engaged after the extension boom has extended all the way out? Yes it is a 6000 pound gauge, but it seems to be filled with a clear fluid, oil? To prevent corrosion? I'm wondering if I remove that gauge to attach it to a hose, if that oil in the gauge would flow out, since it is mounted vertically? Great idea on the hose. I'm thinking I could just attach it to a 25 foot hose, and just coil it up and leave it attached to the hose inside the engine compartment?
The question is IF it's the supply line. Hard to be sure from the partial view in the photo. The larger hose on the left, does it go to a pump?, and is there another hose on the opposite end of the valve going to the tank? If so then yes, it's a supply line. To deadhead would indeed be to, for example, extend a cylinder all the way and hold pressure on it, then the gauge would show the pressure going to that cylinder. With the caveat that I'm not familiar with this machine, I would say that the gauge would NOT indicate pilot pressure. My best guess right now is that the small hose going into the valve bottom left of the picture is pilot oil.
Oh, and yes, better quality gauges are filled with oil, mainly for damping. On top there should be a rubber bung. As long as it's in place the oil won't run out.
Thanks Cmark! Yes actually that big hose comes directly from the main pump and there is a hose at the other end of the proportional valve manifold that goes back to the storage tank. Okay, so I assume that holding pressure after deadhead will not blow out the hydraulic hoses. Normally when the engine is idling with no functions engaged the pressure gauge shows about 100 to 200 lbs, but if I look at the gauge 5 or 10 seconds after extending the boom for example, as long as it takes me to walk around the machine to look at the gauge, it will show a thousand pounds pressure. Does that sound normal? And what do you think of this idea, I could just put my cell phone in video mode or use a video camera aimed at the pressure gauge and record the readings while I'm operating the functions?
IF your hoses are in good condition, holding pressure on them will not be a problem. If they're getting a bit old and crusty, it's at your own risk Usually I would expect the pressure to drop back to close to zero immediately a valve is put back to neutral, but once again, I'm not familiar with that machine. What exactly are you trying to achieve here? Do you have a specific problem? Good idea about videoing it.
It's usually glycerin that they put in the gauges. It stays clear and won't freeze. It's also good to know what kind of a pump and hydraulic system you have. An open center parallel passage system will most times have a positive flow gear or vane type pump while a closed center system might have a variable flow piston pump. It will make a difference on what you see on the gauge and how the machine is acting. I haven't worked on that brand of man lift before so don't know what you have.
Cmark, I'm wondering if my drive wheel motors are low on torque because of low hydraulic pressure from the main pump. I have another thread going which I haven't gotten any replies on entitled " boom lift Drive Wheels torque fade". I just posted a schematic diagram of the torque drive motor on that thread. It's a Cessna 20800 variable piston motor assembly.
Okay so I was able to read the pressure by recording the gauge with my cell phone video. With no function engaged, the pressure was about 200 lb, but when I engage the boom lift function the pressure jumped up to 2500 lb. And when I engaged the drive wheels, the pressure also jumped up to 2500 lb. And the right side wheel continued to spin, but the left wheel stopped turning. Is this normal pressure for the drive wheels? Would this rule out the main hydraulic pump as being the cause for loss of torque in my drive wheel motors?
Looking at the photo you posted in one of your other threads, unless I am mistaken, it looks like the component which splits the hydraulic flow to the motors is a plain manifold. If that is the case, both motors will see the same pressure but the one seeing the least resistance (traction) will spin. Do you have a hydraulic schematic for the machine?
Thanks Cmark. Attached is a screenshot of the hydraulic schematic and a closer up screenshot of the hydraulic motor area on my 1980 marklift 62. The third screenshot is a hydraulic hose schematic in the same manual but it is dated 1986 and it is showing a two speed shift cylinder on each wheel, whereas my 1980 model has just 1 two speed shift cylinder operating both wheel motors. I could also just upload the entire PDF manual at 12 megabyte if that would be allowable on this forum.
The gizmo I circled splits the supply oil between the two drive motors, very much akin to an open differential in a drive axle. Whichever motor has no traction will steal all of the oil, by design, leaving the other motor motionless.
And if my poor skills at reading hydraulic schematics is right that would only be effective in on direction. I recall the Snorkle Lift we had at the quarry had a flow divider valve in the lines from the control valve to the motors. If memory serves me right it was suppose to send approximately the same amount of oil to each motor, kind of like a limited slip differential. It may have only been when in say a low speed situation, been a few years so I'm a bit cloudy on this!
Not that it will help with this machine but did find the drawing for the Snorkel Lift, not the same kind of schematic type drawing. In it you can see the two different flow dividers in the drive circuits forward and reverse:
The other direction doesn't have anything but a tee. Thing I circled may very well be just a flow restrictor then. Either way, that schematic shows that the motor with the least resistance gets all the oil.
The component circled contains two orifices which appear designed to allow both motors to have pressure at the same time, but I'm not sure what the Down Arrows denote. Bear in mind that when the motor is run in the opposite direction, the oil from the motor still had to go through these orifices so the effect will be the same.
Well, I pulled off the left side motor today and will proceed to disassemble it tomorrow for a visual inspection for broken or worn out parts. I also want to see if I should be able to move that shift lever by hand and if it is jammed in one position. I'm thinking that I would like to just disconnect the 2 speed shift cylinder and bolt the motor shift lever into the position that would provide greater torque, even if the wheels turn at a slower speed.
So if there is more fluid volume going into the hydraulic motor and therefore more torque, does that mean that the wheels will be turning more slowly? I would think yes, but so much of what I have learned about this machine tells me not to assume anything LOL
I believe the circled item is a priority flow divider. The schematic as shown does not identify all the parts in the valve so we can't determine the logic of how it is supposed to work. They can be set up as pressure operated or flow operated. The ones I am familiar with are prioritized for flow. Basically they are set up so that no matter what the pressure it takes to turn a motor a spool valve will shift to enable that the same flow goes to each side. Lets say one wheel runs up against a rock while the other stays running on flat ground. Common thought says the motor against the rock will need more pressure to enable it to rise up over the obstruction. But since it takes little pressure on the flat side wheel, all the pump flow will go to that motor and make it spin real fast. The priority valve has a spool that shifts between the sides. When pressure on one side increases the spool shifts to restrict the flow to the low pressure side. As to the question of flow and torque go, there is more to the statement than that. In this case you have a specified amount of flow for travel as a whole. Increasing the flow will only make the motors turn faster. The amount of torque they can put out is determined by the efficiency of the motors and the settings of the various pressure control valves. So if you have ten gallons of flow to the motor and pressure control is set at 1,000 PSI then it will have the same torque as a unit with 20 gallons of flow and the pressure control set at 1,000 PSI all things being equal. The way you get two speeds and two different torque outputs is to change the angle of the swash plate and the distance the pistons move in the motor. Low speed means the swash plate is tilted all the way so the pistons have a long way to travel. High speed means the swash plate might be at half the angle so the same amount of oil flow makes the motor spin a lot faster. Keep in mind that it doesn't matter what speed you are in as far as the necessity of the flow divider is concerned.
Thanks for that detailed reply John! And now that I have completely disassembled and inspected that left drive motor at least I know the terminology for a swash plate LOL. What an amazing piece of engineering! See pictures. I saw no obvious damaged or worn parts, unless some of these parts like the pistons have to be measured with a micrometer? But everything seemed as if it was factory new. And at least I know that I can move that shift lever by hand now without damaging anything internally. So since I found no obvious damage, I am thinking that I will switch the left and right drive wheel motors and see if the same wheels do the same thing they did before, which would tell me that the problem is not the drive motors, but probably somewhere up the line in the switching v alves such as the one circled in red?
More pics I assume this above is the swash plate?
I don't want to **** on your bonfire too much as you're clearly a self-help, have-a-go kind of guy, but you really need to pay special attention to what you're doing putting it back together. The first thing I note is that you have the barrel upside down on a rusty bench. The barrel face is precision lapped and can tolerate NO blemishes, same as its mating surface on the head. The same applies to the slippers and swashplate surface but these don't seem to have been exposed to danger at this point. If your barrel is OK, when you assemble it you need to aim for as close to hospital grade cleanliness as you can achieve. Rinsing parts in a bucket of diesel isn't, IMHO, enough. Invest in a half dozen cans of brake cleaner and use them liberally. Good luck.
Thanks Cmark! Actually I rinsed everything in gasoline, but I never let gasoline come into contact with rubber parts. I'll start using the brake cleaner instead. So I take it that there are no parts that I need to measure with a micrometer?
There's nothing you can measure that will make any difference. You could maybe measure the piston bores, but any wear would be obvious with a visible step. Super critical is barrel and head finish, piston and bore finish, slipper and swash plate finish. Just plain critical is shaft bearings and swash plate carrier bearings.
Thanks so much Cmark. One question on the swash plate, when the swash plate is at 0° and all of the pistons are at the same level, does that have more torque or less torque than when the swashplate is at a 17 degree angle, making half of the pistons higher and the other half of the pistons lower?
Well, when the swashplate is at 0° the thing isn't going to turn at all but to answer your question seriously, for a given flow, the closer the swashplate is to 0° the faster it will turn but with less torque, and a steeper angle will give less RPM with more torque. So your drawings show the motors in the slow speed position.
Thank you!
The two absolutely critical areas are where the slipper feet run on the swash plate and where the barrel runs against the seal plate on the output side. If either shows any damage that you can feel with your finger you would need a new part. The barrel would usually be lapped to the seal plate when ever the motor is opened up. I don't think anyone here thought the motor was your problem but at least you get the schooling on how the motor works. Be very careful when you resemble the motor. Cmark is correct in that cleanliness is as important as getting all the parts back in the right place.
Thanks for that reply. So let me ask for some clarification on this. Is it possible that everything is working properly but that just one of my wheels is spinning when the other one stops because this is like a posi traction in a car transmission, where you have 2 driving wheels but if you get stuck in soft ground, only one wheel turns? And if so, is there a way to override this and lock both of the wheels into drive? And does it make a difference if I am in high speed or low speed? I have this feature on my farm tractor where I can engage both driving wheels if I am driving diagonally over a ditch, and one wheel is spinning while it's elevated off the ground.
There is no connection between the drives other that the hydraulic hoses. Follow the hoses from the motors back. There should be a valve block somewhere that the hoses connect to. That would be a flow divider. That would be the only thing as far as I know that will limit free rotation of one side and keep the other side turning. Actually man lifts generally are not for use in soft or uneven ground conditions. What are you using yours for?
We ran into this kind of problem with a couple different manlifts at the quarry where I worked. The first one we had was a JLG60F and later we were updated to the Snorkle ATB60. Can't be sure but I think the Snorkle was a bit better on uneven ground. If you were to look at the schematic I posted a few pages back it had a gear type flow divider. Kind of like a simple gear pump with no input shaft. Oil came in the inlet through a single port but when it flow rotated the gears there were two outlet ports one for each gear/drive motor. Assuming no wear or internal leakage each drive motor would get the same volume of oil flow. But we all know nothing is perfect and there would be some internal leakage. So I guess it would be closer to a limited slip differential action than a good old Detroit Locker diff!
Looks like that flow divider is interaxle! The interwheel ones would have to be pilot operated, otherwise if the would be full time - they would tear up tires really quick!
About gauges - I had a good luck with Wika!
Do you have any problems releasing parking breaks?
I’m not thinking of my self as pump- motor specialist! But I think I see evidence of cross port leakage on the port valve plate ( the dark spot on top between kidneys) and some external bypass ( on the left side ). I think this motor sat idle for a while. It’s definitely in need of good lapping!!!
As for the simbol on diagram - that’s an interesting one! The arrows parallel two short sides of the box indicate that both outlets is pressure compensated, but the problem is - there’s no diagonal arrows across orifice simbols ( which supposed to indicate them variable orifices). If this just a typo or honest mistake, then best guess will be that it is automatic hydraulic lock differential. Pressure compensated means that if one of the wheels would have low pressure on the line, then orifice should open up allowing more flow to the side with less pressure. If it is pressure compensated spool type flow divider - it could be your culprit, as a spool can be stuck in off center position.
I see now! I missed another (gear type ) flow divider! Strangely enough spool type is on one line going to motors and gear type on the other line?! Picture is not good, can’t read, without understanding of what is what I can only guess that gear type is “ differential lock” and spool type is regular differential ( gives more flow to the wheel that travels on outside/longer radius, and looks like the diagram you posted is for four wheel drive as well as four wheel turn machine, because motors connected in cross fashion, and there’s turn switching valves) And the “motion control valve” switches from one mode ( flow divider ) to the other.
OP, as it seen from the pictures and diagram, your motors displacement regulates by single speed shift cylinder by external linkage, it would be good idea to check the linkages and weather both motors awash plates have the same angles!
But then again on the hose daigram it shows that each travel motor has its own speed shift cylinder - contrary to hydraulic diagram above!
No problem at all with the brakes. If I turn the needle valve all the way in on the brake control valve it locks up the wheels even if I engage the wheels, so the needle valve is out about 3/4 of a turn. Yep, that hose diagram was the only diagram I had in the service manual and it showed a 2-speed selector cylinder for each wheel, but in reality, I only have one 2 speed selector cylinder and that is on the right side motor, and the lever has a long rod connecting it to a lever on the left side motor. But guess what? In the process of pulling off the right side wheel motor so that I could switch it with the left side motor, I discovered that the lever that connects to the 2-speed shift cylinder had a lot of free play in it where it connects to the swashplate shaft. The roll pin was completely split in half lengthwise. See picture. And so I think that the swash plates on each motor could have been in different positions. The diagram shows the swash plates should go from 4 degrees to 17 degrees, and so it is possible that 1 swashplate may have been at 4 degrees while the other one was at 10 degrees for example. So at what angle of the swash plates will make the wheels turn at a slower speed, 4 degrees or 17 degrees of tilt? And will a slower wheel speed give me more torque when I'm driving the machine uphill?
Perpendicular to motors shaft is 0 flow, the more parallel to motors shaft the more flow! But that’s a swash plate, I don’t know position of the shift lever to a swash plate.
Judging by your previous photos the lever is parallel to the swash plate
John, I will be using this man lift for pruning tall trees on my property. I have over 500 trees, and the tree services wanted $800 a tree LOL. TVA, what is lapping?
So I'm getting confused trying to picture in my mind perpendicular and parallel LOL so let me try to understand a different way, the more tilted the swash plate, the more flow. Tilted would be around 17 degrees and half of the 9 pistons would be higher and half would be lower. Kind of like a butterfly in a carburetor, right?
I’m driving right now, just go to you tube and search “lapping valve plate”. But I would not recommend diy though!
Yes - all Pistons at the same level means no flow! Butterfly in carburetor closed - is perpendicular to throttle body, fully open - parallel to the trottle body. In your case lever at 90 degrees across shaft is no flow, and vice versa.
Another question: are these motors mounted to steer axleor non steer? And is there an swash plate angle indicator on the shaft? Probably on the opposite side from lever ( like on Rexroth pumps ).
Don't worry about the angle of the swash plate. Fix the broken linkages and then try out the machine. Some times you don't have to understand all the complicated stuff. Just fix the easy stuff first and see if it takes care of the problem.
TVA, no swashplate angle indicators on the motors, and the motors are on the non steering wheels. I am also attaching better pictures of the control valve box that the motors are connected to. It shows two large lines going out to each motor and two large lines coming into the control valve box. It also shows the brake needle valve connected to that same control valve box.
Like John said - fix the linkage problem and see if it helps, then go from there.
Thanks TVA. As long as I have the motors off, I decided to look at the brakes a little more closely and I see a grease zerk fitting and I'm wondering how do you know when the grease is full, when it starts oozing through the driveshaft seal? Also wondering what kind of grease you would recommend, I have not looked in the manual yet. There was grease between the brake housing and hydraulic motor, but no zerk for that area, so that's why I'm thinking possibly the grease comes through the drive shaft seal from the brake housing? I was going to just pack that area with water-resistant grease from a can before I mate the brake housing and motor back together.
Are you sure those are grease zerks and not bleed screws?
TVA, no wonder my grease gun would not fit this fitting LOL. I think you saved me from making a big mistake here LOL but I have never seen a bleeder screw like this before. I am just used to what you see on automobiles, which are not all one piece. Actually I turned this brake assembly upside down from where it was before with the bleeder screw facing down.
That branch is “dead end” so your gonna have to bleed it when you’re done, just like car breaks!
Not sure what you mean by dead end? So on the left wheel the bleeder screw was halfway up the side of the brake assembly, but on the right wheel the one pictured above, the bleeder screw was on the bottom. So would I be better to have the bleeder screw on top, which would ensure that the brake assembly is full of hydraulic fluid? Or flip it around again so it's on the bottom, like it was originally. Also I would assume when bleeding these brakes, that I would just need to have the engine running, as opposed to like in a car where someone has to depress the brake pedal while cracking open the bleeder screw? I'm assuming brake lines are fed with pressure from the pilot pressure hydraulic lines.
Dead end means no outlet to bleed by it self, hence you need bleed screw, the position doesn’t really matter, but facing upward I think is best.
That’s a spring activated parking breaks, so you will have pressure while you try driving forward or in reverse, it should drain off when you stop.
No break release fed from drive motors line! You will have pressure while trying to drive, doesn’t matter forwards or backwards, it should drain off when you stop.
Thanks TVA! I will YouTube how to bleed hydraulic brakes to try and get a better idea of this bleeding procedure.
And I am assuming I should still pack grease between the wheel and brakes and hydraulic motor mating areas?
You mean break housing and motor it self? I would use thin coat of neversieze.
To bleed the air I would jack up both drive wheels, put the clear line on bleed screw and put machine in drive, until I see no bubbles in clear line ( it will only take a second/s) tighten the screw before stoping, repeat on the other wheel.
That needle valve on break line - you definitely don’t want it open all the way, unless you want to fly out of basket as soon as you move drive lever in to “stop” position!
TVA, when you say put a coat of neverseize, I assume that is what you would put on the splined shaft from the motor to the brake housing motor? And I assume that the neverseize has the consistency of heavy grease so it would not melt or run off to the bottom of that cavity between the motor and brake housing? There was what looked like about a half a cup of melted Grease at the bottom of those housings when I took them apart.
I'm also curious about the position of the bleed screw on the brake housing. If the bleed screw is on the bottom or side of the brake housing and there is air inside the brake housing, air bubbles would go to the top of the housing above the bleed screw, so how would the hydraulic fluid get above the bleed screw level in that air pocket?
Neversize has a base of light grease with graphite, molibdenum or copper added to it, so even when grease will dry up years from now you will still have naturally anti corrosive and anti friction material in there! You can BYU it in any auto parts store, it might have different names though!
Thank you!
Air lighter than oil - that’s why I think up is best position because the first thing that will get pushed out when bleed screw opens will be air! And you supposed to do it under pressure! In this system you induce the pressure by driving!
I had another idea about pressuring up the system without jacking up the wheels, which is a lot of work with my 50 ton bottle jack but only rises 5 in at a time and for each wheel. If I disengage the wheels on the outside of the hubs, as if I was going to be towing the unit, then even if I engage the wheels with the control lever, they would not turn, but it would pressure up the system, and hopefully not blow out the hoses?
Good deal!
Hello TVA, I was wondering if you could take a look at my latest post on this link below, since it relates to the discussion on this same post. Thanks! HeavyEquipmentForums