Adding a Hydraulic Pressure Gauge?

[tomrscott]

Has anybody added a hydraulic pressure gauge to their tractor? I was thinking it would be kind of nice to have a feel for how hard it is working. Also have thought about eventually adding the JD shim kit to the pressure relief on my 790 and would want to know how high it runs then.

If you wanted to do this, would you just tee into the high pressure line right out of the hydraulic pump with a narrow gauge line and make real sure to get all the air out? I have seen hydraulic gauges that ran up to 3000 pounds full scale for $10 to $15. Seems like it would be worth it to have a feel for how much load you've got on the hydraulics. I even saw one that was panel mount with the fitting on the back.

 

[kennyd]

I made one that just plugs into a QD, I used it to check the pressure on my tractor.

Here is a Picture

 

[texbaylea]

I did the same as Kenny but simply screwed my guage into the male QD. With my setup, it is easy to see from the seat.

Vernon

 

[ZJ_HR]

If you add one like Kenny showed, you'll just measure relief valve pressure.
I added one for checking working and relief pressure.
Range is 250 bar = 3625 psi

 

[ZJ_HR]

And connected in series with cylinder, left from rear working light...

 

[tomrscott]

I would like a gauge that I can easily view at any time from the operator position so that when I pick up a heavy load, I can easily see how close to the limit I am.

Is there some problem with running a small gauge line from a TEE right out of the Hydraulic pump to the gauge in a more convenient location? Since there is no flow in the line to the gauge, even something like 1/8" line shouldn't cause any appreciable effect on the system or the gauge readings.

That way I can see hydraulic pressure for any cylinder as I actuate it, even the rockshaft. This would also serve as a "poor man's" scale. You could calibrate a conversion table and know how pressure translated to weight in the bucket lift or bucket tilt, or a load on the rockshaft. The only downside is that it wouldn't show holding pressure, just the pressure when actuating it. The only way a cylinder could see higher pressure than this gauge showed would be if you dropped additional weight into a bucket that was being held in position.

The biggest nuisance to this is that when you release the SCV, the pressure would drop back to idle. Perhaps you could create a "peak hold" circuit with a check valve that could be released with a pilot input or electrically. Hummm....

 

[v8dave]

Be careful, gauge needs to be hooked up with proper lines and fittings. A high pressure hydraulic fluid leak could penetrate your skin. Use steel lines and fittings intended for the pressure.

 

[keeney]

If you put the gauge between the loader boom lift cylinders and the SCV, it will show the pressure holding the bucket up regardless of the valve being open or closed. The setup with the tap between a male and female quick-connect might be ideal for this, or you could plumb it in on the loader itself and mount it up on the arm or something.

You can see dynamic pressure spikes that significantly exceed the relief pressure setting when the valve is closed if the load is bouncing up and down or you are ramming the tractor into a heavy pile.

Think of it this way - what would happen to the loader if you were to suddenly cut the hose going to the lift cylinders? It would fall to the cround. Unless it is resting on the ground or otherwise blocked up, there is pressure in that line holding it up.

Except when the loader is resting on the ground, you will need to subtract the pressure caused by the empty weight of the loader from all values. Zero payload weight will not be zero pressure.

Many loaders have a fairly non-linear lift geometry leverage curve. The pressure for a given weight will typically be higher at full height than down near the ground. You will want to calibrate your "scale" at a given lift height - preferably down near the ground.

- Rick

 

[Henro]

<font color="blue"> I would like a gauge that I can easily view at any time from the operator position so that when I pick up a heavy load, I can easily see how close to the limit I am. </font>

tomrscott,

I've done a lot of loader work with my tractor over the last couple years. A LOT...

I grabbed onto that quote above, because I can't think of a reason why I would need to know when I was approaching the limit of the loader. The loader tells me when I have reached its limit, and reaching the limit does no damage, just trips the pressure relief valve and I immediately back off and do what is necessary to lift less and get the load back within the limits of the loader.

I can understand the desire to have extra information and all that. I just don't see a practical need for such information.

In the past I considered adding a pressure gage like you are doing. I thought about it and in my case wrote it off as unnecessary. I am sure you can install one simply. One of the long time posters here has done it. I remember the post and want to think it was a blue tractor, but it has been a while and I don't remember who the poster was.

You certainly can add one and it will work like you think it will. If you are using it to gage weight you may have to also consider the geometry of the loader linkage, at different heights, if you want accuracy.

If you put the gage on the output side of the loader valve it would show holding pressure, but then would not show system pressure when other implements were operated.

I think you need to add at least two gages... /forums/images/graemlins/grin.gif

 

[ZJ_HR]

If you make T connection with hose and manometer just behind pump, you'll see pressure just during lifting.
If you want to measure "weight" in loader, you need to connect T with manometer in lifting hoses circuit. Just make something like on my first pic, put high pressure hose between T and manometer and install it in fast connectors toward lifting cylinders.
But, as somebody mentioned, your loader has overload valve anyway, so you don't really need it.
I made and used this gauge when I had jerking during lifting hopper on my corn picker, and wanted to detect problem.

 

[v8dave]

</font><font color="blueclass=small">( Be careful, gauge needs to be hooked up with proper lines and fittings. A high pressure hydraulic fluid leak could penetrate your skin. Use steel lines and fittings intended for the pressure. )</font>

Oops, this isn't a complete thought/idea. What I left out was: if you are trying to mount something in the dash board. You might be tempted to use copper because it is easier to form, but if you plan on using rigid hydraulic lines, use steel.

Excuse the bumbling........

 

[tomrscott]

v8dave,

Good advice for anyone who might be reading the posting, but yes I am very aware of the pressure limits of different fittings. I've spent quite a bit of time looking at hydraulic fitting specs.

I might use steel tubing, or at least 1/8" hydraulic hose rated to 4kpsi or better.

Still mulling over what I want to do with a gauge. I guess my biggest interest is wanting to know what kind of peak loads my hydraulic system sees. If anything does go wrong, I guess the engineer in me would like to know what pressures are happening. I guess the loader is the most critical, and the system might see pretty big transient loads from things like a heavy load being carried and bouncing. Maybe a boxblade hitting a rock could see a pretty big thump too. The more I think about it, the more I think I want to rig a resettable "peak hold" circuit with a pilot check valve. I could put a ball valve in series with the check valve to release it, or maybe an electrically operated pilot check valve.

Still thinking about it.

 

[Trackintrail]

I was wondering if you guys had any input on Using the gauge to estimate the weight you are lifting? how sensitive is valve adjustment and temperature to this pressure here? Lets say I am lifting 1500lbs, and I am reading 500psi on my gauge, If I hook this up to a different forklift and try to use the same readings, will it be different because the valves are adjusted differently? Would I have to recalibrate my weight to PSI comparrisons? Also, how much does temperature affect this.

Thanks.

 

[SPYDERLK]

v8dave,

Good advice for anyone who might be reading the posting, but yes I am very aware of the pressure limits of different fittings. I've spent quite a bit of time looking at hydraulic fitting specs.

I might use steel tubing, or at least 1/8" hydraulic hose rated to 4kpsi or better.

Still mulling over what I want to do with a gauge. I guess my biggest interest is wanting to know what kind of peak loads my hydraulic system sees. If anything does go wrong, I guess the engineer in me would like to know what pressures are happening. I guess the loader is the most critical, and the system might see pretty big transient loads from things like a heavy load being carried and bouncing. Maybe a boxblade hitting a rock could see a pretty big thump too. The more I think about it, the more I think I want to rig a resettable "peak hold" circuit with a pilot check valve. I could put a ball valve in series with the check valve to release it, or maybe an electrically operated pilot check valve.

Still thinking about it.

Do not put a gauge in the loader lines after the valve. It will see a lot of transient loading as you move and it will fatigue the Bourdon tube over a fairly short time. The gauge will probably blow before this tho because of the very high [as much as 10kpsi] transients seen as you move with a full bucket or push hard into a pile with the valve centered. The relief valve is not in this part of the circuit. The bucket will fall if the gauge blows.
I put a gauge in my pump output line as you are thinking about. At the connection to the hose feeding the gauge I threaded the interior of the connector and forced a set screw in lightly. The oil must travel thru the thread helix so flow is very slow. This way if the gauge or hose blows it will only drip. I find that my loader valve builds near 1000psi before opening the lines to feed the loader so everything takes at least 1kpsi. The heavier loader loads give a reading more in proportion to the weight of the load.

Its good because a gauge in this location always gives you a reading of how much pressure the pump is working against no matter what part of the hyd circuit you are using.
larry

 

[AKKAMAAN]

I was wondering if you guys had any input on Using the gauge to estimate the weight you are lifting? how sensitive is valve adjustment and temperature to this pressure here? Lets say I am lifting 1500lbs, and I am reading 500psi on my gauge, If I hook this up to a different forklift and try to use the same readings, will it be different because the valves are adjusted differently? Would I have to recalibrate my weight to PSI comparrisons? Also, how much does temperature affect this.

Thanks.

Hello All!

I'm new to this site and I like it a lot with all the versatility and knowledge available.

I think you can add a gauge between valve and cylinder...SPYDERLK is making an important point though....so put a three way valve b4 gauge to shut it off when not reading...(3rd way drain gauge to tank)....

another way to try is putt'n an very small restrictor about 1.0mm with a 0.8-0.9mm wire loose in the hole for self cleaning, that will keep high energy shocks away from the gauge, but still allows you to read load-pressure....