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20 ton weighing scales anyone?


simonr
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It is no more than modifying a bottle jack and adding a pressure gauge.

The gauge used is from a welding gas regulator - and they are only a few quid to buy new. The jack is a Draper 2 ton type and it cost all of £9.99.

The other two jacks I have are so similar that I would be confident just to drill in the same place.

Drill%20and%20tap%20jack.jpg

Jack%20up%20LR%20Wheel.jpg

Gauge%20says%202400psi%20or%20634kg.jpg

The last two photos show lifting one of the rear wheels on my 90.

The piston in the jack is 21.9mm in diameter or 0.584 sq inch area.

It therefore takes 3.78psi to lift 1kg

Thus the 2400psi shown equates to 634kg - which is about right for the weight of one corner.

I'll probably go and weigh the back end on a weigh-bridge to calibrate it more accurately.

Si

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mixed measurements Si?

whats that in bushels per mm/Hg?

....I'll get my coat... :lol:

Don't tell me you don't mix measurements a bit? Thou - mm - inches - feet - meters - miles whichever is closest to an integer for whatever you are measuring.

Si

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erm :unsure: ........... yeah ok its been known...a lot........busted :hysterical:

:hysterical:

Oh yeah mixey meaures, does my mates head in who is a proper engineer,.....

I pop in and say could I have this in 5mm plate say 31.5 inches by 744mm

I now get the std "Look"

This "Look" means :

ONE OR THE OTHER - CHOOSE AND RETURN OR F O " :lol:

Guilty big time as well :lol:

Nige

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how does this work in practice si?

do you just keep pumping until a wheel is just off the ground? does it matter where the jack is in relation to the axle- ie is it more accurate to use one jack in the centre of the axle or two jacks at any one time? could these be used to work out C of G if you could get them to jack high enough?

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how does this work in practice si?

do you just keep pumping until a wheel is just off the ground? does it matter where the jack is in relation to the axle- ie is it more accurate to use one jack in the centre of the axle or two jacks at any one time? could these be used to work out C of G if you could get them to jack high enough?

Correct, just pump until the wheel is off the ground.

Working out where the c of g is, is a bit more complicated. It's easy enough to work out where it is in 2D - looking down from on top of the vehicle just by the ratio of the four axle weights.

Working out how high it is off the ground is more difficult. You can do it by driving each wheel up on to a ramp and seeing how much the axle weight for that wheel changes. As you raise a wheel, the cog moves away from that wheel. You use a load of trig & similtaneous equations to work out the position of the cog in 3d. Not rocket science, but not as much fun as dangling your truck from a crane either! ;)

Si

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Working out how high it is off the ground is more difficult. You can do it by driving each wheel up on to a ramp and seeing how much the axle weight for that wheel changes. As you raise a wheel, the cog moves away from that wheel. You use a load of trig & similtaneous equations to work out the position of the cog in 3d. Not rocket science, but not as much fun as dangling your truck from a crane either! ;)

Si

Si

This is what I used Centre of gravity

Getting the front wheels two feet in the air is a bunch of fun :blink:

If you get some numbers - I'll show you mine......

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  • 4 weeks later...

I have just made mine and appears to work well.

Although i tried the front offside of the bowler and the disco300tdi and got roughly 1200psi. which equates to 300kgish.

I think my piston contact head may be a bit bigger though 25.6mm measured. Was surprised by this.

Simon, any chance of you weighing the osf of a disco and seeing what you get?

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I sent mine to Northern Chris to calibrate against his load cell - not talked to him for a couple of weeks, so don't know how it went!

One way or another, you either need to calibrate it or take it apart and measure the piston diameter. This is usually different to the piston rod (to stop it popping out when you pump it up too much!)

Si

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bugger it.

i thought that the piston may be retained by a circlip or something, its steped then?

i am using a 3ton jack, and measured the piston at 27.85mm after my previous cock up. but now guess thats wrong as well.

will need to calibrate it with a known weight then.

cheers

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Don't tell me you don't mix measurements a bit? Thou - mm - inches - feet - meters - miles whichever is closest to an integer for whatever you are measuring.

Si

Or even in the same measurement

"It's just a couple of mill over eight inches" :lol:

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  • 2 weeks later...

just incase anyone else fabs one of these up. the piston has a 29.9mm dia shaft on a 3t jack(i think most are the same, mines a wolf(screwfix) and also one from machine mart)

if you use a 3t jack youll only need a 2000psi gauge if your planning on lifting a landy, works out to about 750-1200psi on a 300tdi disco corners.

hope that helps someone.

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