:MTF_wel2:

Available pressure is only one of several factors dictating the lifting capacity of a front end loader. The cylinder size, how the cylinder geometry is arranged, the leverage as it relates to the cylinder and length of the arms, and the dead weight of the bucket and arms ahead of the cylinder that has to be lifted regardless of payload. Beyond the hydraulic issues is also the friction involved with the various pivot pins which must also be overcome by the cylinder. One misaligned pin can eat up a lot of pressure.

The pump.

This unit appears to use the hydro's charge pump for the hydraulics. The Sundstrand charge pump is rated for a maximum pressure of 1000 psi. Exceeding that pressure risks damage to the pump casing and pump drive. The normal relief pressure for the implement hydraulics on a JD 400 from the factory is 850-950 psi.

The cylinder.

The lift cylinder visible appears to have a 1.5" bore x 16" stroke (1.5x16). That's not really a large cylinder with less than 1000 psi to work with. At 1000 psi, it can generate a pushing force of 1760 lb. That sounds like a lot, but that is also directly in line with the centerline of the cylinder.

The geometry.

When the angle of that force against a lever is anything but 90°, there is a corresponding loss of force that can be applied to perform the work. For example, when the angle between the cylinder rod and the arm is 45°, only 70.7% of available force can be applied to raising the arm.

The leverage.

The cylinder pushes against the arm in one location and the load is at another location. Scaling from the pic, it appears that the cylinder is pushing on the arm at 3' from the post and the load is about 8' from the post (horizontal distance, not direct line). This gives an apparent 2.67:1 leverage against which the cylinder is acting. Apparent because there is a parallax error due to the camera position compared to what can be scaled from a plan on paper. Any dimensions that can be derived from looking at a pic are educated guesses.

The dead weight.

The bucket appears to be 54" wide and 18" tall. From its construction, estimated weight is about 150 lb. Added to that is about 30 lb for the arms ahead of the lift cylinder connection and 15 lb for the bucket cylinder.

As a side note, the bucket won't last long without a cutting edge welded to the
front edge.

In theory, using the guesstimated dimensions above, maximum payload could be as high as 450-500 lb. This is optimistic in my view. An accurate assessment requires accurate dimensions and available pressure.

Corrective action.

- Playing with the relief valve on the existing system is not an option worth the effort. The possible gains are . . . limited.

- A larger bore cylinder will yield considerably more lift without requiring much, if anything, by way of modifications. It will slow the lifting process considerably due to the limited flow capacity of the pump.

- A longer stroke will improve the lifting force to a somewhat lesser extent, depending on how much additional stroke is involved, but will also reduce the lifting speed to some extent. It will also require relocation of the cylinder mounts.

- Any other corrective measures are labour intensive and basically involve redesign of the loader. This is not really a bad idea since the loader arms are one of the least expensive parts of a loader build in terms that the wallet can understand. It's cheaper than a new pair of cylinders. While it can result in an improvement in lift capacity with the existing cylinders, it will not match replacing the cylinders with ones with a larger bore.

- Last is to install a separate auxiliary pump which can handle more pressure. This solution also requires a new valve set to operate the loader and a separate reservoir. It will result in some benefits worth having, but it is the most expensive solution by far. Finding a place for the pump and reservoir can be a real head scratcher.

Any of the suggested solutions will be costly in time and/or funding, and redesigning of the loader arms is math intensive when calculating for efficiency when using the same cylinders.

 

Tudor thanks for the reply, a lot to take in from your post. Could there be any other issue rather than redesign? Usually when a hydraulic system is working hard you can hear it right? This system the minute you put any kind of load stops dead, it does not try neither from the tilt bucket nor the two lift cylinders. They are 1.5" cylinders by the way rated at 3000lbs. This unit is running 650 psi pressure and from what I read that is norm for the jd400 isn't it? Sorry to question you just really does not make sense to me as the hydrostat on this tractor works great no issues at all!

ps this is an old pic there is a new welded cutting edge on the unit now.

 

Could the hydraulic lines be too small? The fact that it stops instantly when a weight is applied sounds like it simply doesn't have the pressure to start the process of extending the rams. That could also mean the ram/arm angle is so un-advantageous that the force for break out is too much. In other words, you are trying to lift something with a straight line advantage that is like lifting the floor as you stand on it. The first thing I would do is to stick a gauge on all parts of the system as you try to engage it and see what is the local operating pressure at that point. If the pressures are good then you can focus on the geometry/ram of the setup. Good luck because you will love that loader!

 

As inspectorudy says, check the pressure for all functions. The place to do this is the charge pressure gauge port on top of the main pump body beside the implement port on the right side. From that location all functions can be checked for pressure by dead heading the cylinders in each direction.

From my reading of many JD posts regarding implement lift pressures, the JD120 and 140 GTs appear to be relieved at 550 - 650 psi and the 3xx and 4xx tractors with Sundstrands are generally in the 850-950 psi range.

In the case of the Sundstrand with the relief buried in the main pump's cast iron case, there is a good possibility that you won't hear the relief valve sound off over the engine noise, especially if it is set for a low 650 psi.

I made a bubble brained error when doing the calculations for the lift capability previously. Using 650 psi, it should be able to lift 400 lb with the estimated dimensions that I used. Since the system stalls out, the dimensions need to be corrected for accurate calculations to get a better understanding of what may be wrong.

If the hydro is working correctly, the charge pump is also working correctly, but charge pressure only needs to be 50-150 psi to keep the hydro supplied. The charge relief valve dumps excess flow into the implement lift hydraulic system rather than directly back to the reservoir. When the implement relief pops, it dumps directly back to the reservoir via internal drain ports in the hydro.

 

The JD400 (at least my 1981 model) relief valve in built into the 3 spool control valve. It's a bit clumsy to get at under there but doable to shim up the pressure. The ball and spring are under a cap that is the lowest/most forward corner of the valve. The valve is mounted angled up on the front. Mine was shimmed to 1150 psi. I've since added an auxiliary pump but the onboard worked fine for a couple of years before I got the bug to upgrade.

Another thing to look at is the middle handle float position. If that is sticking, it will goof up the rest of the system. If being stuck in float were a problem, it would show up as, when turning, the arms would lift unexpectedly. As the power steering is demanding fluid, the pressure builds and backs up in the system overcoming the float function. Does the power steering assist work normally?

All the hydraulic fluid flows through the power steering valve on it's way back to the transmission pump reservoir. That is why sometimes an issue upstream shows up there.

Good luck!

 

this probably has nothing to do with anything, but the loader arms look out of proportion to the loader, the arms that lead to the bucket look extra long

 

I agree with Don about the arms being out of proportion to the two lift arms that should be parallel to the hood. This thing has a Praying Mantis look about it. Also, the top part of the lift rams are not connected to the parallel arms but to the sloping arms which to me are not lifting the arms as much as it is pushing outward on those sloping arms. Let Tudor do the geometry but it doesn't look right. What does it do without the bucket on the arms? If it won't lift just the arms then it will never lift the bucket too.

 

I was trying to avoid a discussion on the arms in the interest of keeping the costs in time and money reasonable.

The arms will work fine as they are for the time being, but this is basically a light duty loader good for learning how to operate. For serious work, a redesign is a must. Impact loads on the cutting edge are going to play havoc with the long and steep front part of the arms.

A good design allows the impact load travel a straighter path to the posts which should be reinforced with the diagonal bracing to handle the load.

Note that the top of the arm is not parallel to the top of the hood. The lift cylinders on this one are 2x18.

 

ok thanks guys, sometimes things are what they are and I just need to revamp the loader. I will purchase two 2.5" x 30" hydraulic cylinders and mount them on the loader front arms so that they are horizontal. I will start with that and see how it goes. I have a pto snow blower that it looks like I will have to use for the time being. I couldn't pass the deal on this up $2500.00 with blower and loader so I can afford to put some money into it to get it working properly. This will also give me two cylinders to mount to the bucket in order tilt it easier. Grandpa Jay thanks for chiming in I saw your loader and let me say fantastic work. Also Tudor thank you sir for your expertise everyone here is a huge asset.

 

Umm. Installing 2.5x30 cylinders on a GT loader is akin to installing a transport's diesel in a Volkswagen. Overkill is an inadequate description. It will also take something on the order of 6 times as long to raise or lower the bucket with the existing pump.

Change the 1.5x16 cylinders to 2x16 cylinders. That will increase lift capability by 78% with a comparable reduction in lifting speed.

It takes a specific amount of pressure to raise the arm with zero payload. Increasing the cylinder size reduces the pressure requirement leaving more available pressure to lift payload.

The math for loader geometry is totally integrated. Change just one dimension and every calculation for the loader will have a different answer from the baseline calculations.

 

I got my loader working nice, unfortunately I did install the 2.5x30 cylinders because I already had them and cost was a factor. The Hydraulics are slower than I would like and I am assuming it is because of the larger cylinder but honestly I am happy very happy. I also modified the snow blower on this unit and it works amazing as well, it is a pto driven style and it throws a ***** ton of snow. Special thanks to Tudor who I really didn't listen to lol but he did give me the right direction to move in.