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wjkrostek 
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Joined: 18 Dec 2010
Location: Wasilla alaska
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 Topic: pressure guage used as a scale
Posted: 17 Nov 2017 at 1:14pm |
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I was thinking of putting a pressure gauge on a tractor front loader to use as a weight scale and was thinking one of you all may have done this already. It seems that it should work with some testing of some known weights like bulk fertilizer bags for a ton wt and 50 lbs bags for hundred wts. It will be rough but better than nothing. Used to get a rough wt on round bales of hay and bulk bag of oats. The pressure on my loader is maxed at 2800 psi (book) and because of spike I would start with a 4000 psi gauge. Anyone with any ideas?
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wayne IA
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Joined: 22 Sep 2009
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Posted: 17 Nov 2017 at 8:16pm |
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There are gauge kits available for doing just that. You can build your own a lot cheaper than the kits. Would just need to figure out a scale for it (PSI to pounds of weight) and keep in mind that you would need to take the weight readings at a consistent height so the linkages are at the same angle to give a reliable/repeatable value.
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Eric B
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Joined: 09 Feb 2012
Location: British Columbi
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Posted: 17 Nov 2017 at 9:02pm |
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I'm sure you can make that work very well. I did it on a dump truck hoist. It's a little more difficult with accuracy on a truck depending how far forward or back the load center point happens to be. It would work a bit easer on a tractor but as Wayne says you have to keep the loader at the same height when you read the gauge.
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Currently- WD,WC,3WF's,2 D14's B. Previously- I 600,TL745,200,FL9,FR12,H3,816 LBH. Earth has no sorrow that Heaven cannot heal!
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wjkrostek
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Posted: 17 Nov 2017 at 10:12pm |
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What psi gauge did you use on your truck and did you run into any spikes when you stopped to rough. with a max 2800 psi when I lift a ton sack it will just about lift the back wheels off the ground. I assume that must be close to the max psi. but I don't know for sure. I could get a better reading if I could start with a 3000 psi gauge.
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Coke-in-MN
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Joined: 12 Sep 2009
Location: Afton MN
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Posted: 18 Nov 2017 at 7:42am |
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similar system used on trucks with air ride bags - weight is calculated by air pressure .
then load cells measuring deflection of a given distance within a sensing material by resistance of electrical current - is another way.
Many loaders used in industry now have built in scale readers on lift units - in fact they have progressed to where a onboard computer prints out a weight ticket - it is not a certified ticket for resale of materials by weight - but is generally within 100 # of certified scale BOL issued by weigh-master.
Edited by Coke-in-MN - 18 Nov 2017 at 7:46am
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Eric B
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Posted: 18 Nov 2017 at 11:52am |
I used a 3000 lbs. gauge. To spike the pressure could of course easily happen by reefing the control closed very quickly without the hoist being all the way down (with a load in the box). Once the load is resting on the frame all risk is gone. I had used a brass elbow fitting which developed a crack after some time and then I removed the gauge too. I guess by now they have somewhat perfected the scales on loaders but 3 years ago when I retired the loader scales could sometimes be out by up to 5%. That said, I think some of it had to do with how well the operator was able to use the scale too.
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Currently- WD,WC,3WF's,2 D14's B. Previously- I 600,TL745,200,FL9,FR12,H3,816 LBH. Earth has no sorrow that Heaven cannot heal!
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DiyDave
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Joined: 11 Sep 2009
Location: Gambrills, MD
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Posted: 18 Nov 2017 at 6:36pm |
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Either 4k or 5k gauge will cost the same... I have one on my lil ASV RC 30 loader, never have calibrated it... The main thing is to have it be an oil filled gauge, or vibration will kill it early...
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wjkrostek
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Posted: 18 Nov 2017 at 8:08pm |
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I was thinking of using the 3000 psi because there is more distance between the marks so I figured it would be a more accurate guess when you read it. But will it spike and break the gauge if it is stopped sharp on the down stroke. I don't know how much abuse the gauge will take or do they break easy? So do I need a 4000 psi as a safety factor. The most I will be picking up is 2000lbs so there may already be a safety built in. What is the psi normal on 2000 lbs on a JD 452 loader?
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wjkrostek
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Posted: 18 Nov 2017 at 8:12pm |
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it's a 542 loader. The more I think about this the pis is depending on how many square inches are in the lift cyl. I don't know how to measure it without taking it apart. and with two cylinders I guess that doubles the sq. inches. So I figure to measure 2000 lbs will come up to way less than 2000 psi. I have to assume each cyl will have at least one sq inch. So now I'm thinking it will be less than 1000 psi to lift 2000 lbs. Maybe all I need is a 2000 psi gauge. Am I thinking this out right? Anyone with hydraulic experience please set me straight.
Edited by wjkrostek - 19 Nov 2017 at 1:24pm
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Dozer
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Posted: 24 Nov 2017 at 7:25am |
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I did this long ago to check that my trailer load was not overweight.
A 1.125" diameter hydraulic cylinder has an area of 0.994 square inches.
A pressure gage will read directly in pounds.
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CTuckerNWIL
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Posted: 24 Nov 2017 at 7:39am |
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You could always put a gate valve in line with the gauge and only open it when you want to weigh a load. Then you wouldn't have to worry about spikes damaging the gauge.
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Dozer
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Posted: 24 Nov 2017 at 9:15am |
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There are complications using loader cylinder hydraulic pressure to measure the weight in the bucket. The hydraulic pressure needed to lift a given weight depends on the bucket position and the leverage of the loader arms. You should make a separate weigh station. Place the loaded bucket on the weigh station with the loader valve in the float position. You could calibrate using whatever hydraulic cylinder you have available by using a known weight in your bucket.
The shock on the pressure gage will be reduced by using a small diameter restriction before the gage
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DMiller
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Posted: 24 Nov 2017 at 9:42am |
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Also have to compensate for ram side or open side as dynamics of pressure to applied lift will be different. Usually ram inclusive side has less area for push so pressure will go up for a given weight as on the old 500 series loaders that had the bucket cylinders on the wrong side of the boom as per industry standard.
Most of the industry has the piston side for lift but NOT all companies do.
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HudCo
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Posted: 25 Nov 2017 at 6:38pm |
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so how and where is this gauge piped in , i would like to do this on a small walk behind fork lift that i use around the shop
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DiyDave
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Posted: 25 Nov 2017 at 7:17pm |
 HudCo wrote:
so how and where is this gauge piped in , i would like to do this on a small walk behind fork lift that i use around the shop |
Most all are plumbed into one of the lift cyls, at the bottom or lift port. a fork lift should be easier, as it has only 1 lift cyl... 
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