simonr Posted November 28, 2006 Share Posted November 28, 2006 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. 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 Quote Link to comment Share on other sites More sharing options...
Diff Posted November 28, 2006 Share Posted November 28, 2006 Very clever idea! Quote Link to comment Share on other sites More sharing options...
dollythelw Posted November 28, 2006 Share Posted November 28, 2006 mixed measurements Si? whats that in bushels per mm/Hg? ....I'll get my coat... Quote Link to comment Share on other sites More sharing options...
simonr Posted November 28, 2006 Author Share Posted November 28, 2006 mixed measurements Si?whats that in bushels per mm/Hg? ....I'll get my coat... 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 Quote Link to comment Share on other sites More sharing options...
gav- Posted November 28, 2006 Share Posted November 28, 2006 was wondering how best to get corner weights for the bowler- looks like this is it!!! nice one Quote Link to comment Share on other sites More sharing options...
dollythelw Posted November 28, 2006 Share Posted November 28, 2006 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 erm ........... yeah ok its been known...a lot........busted Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted November 28, 2006 Share Posted November 28, 2006 erm ........... yeah ok its been known...a lot........busted 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 " Guilty big time as well Nige Quote Link to comment Share on other sites More sharing options...
pugwash Posted November 28, 2006 Share Posted November 28, 2006 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? Quote Link to comment Share on other sites More sharing options...
simonr Posted November 28, 2006 Author Share Posted November 28, 2006 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 Quote Link to comment Share on other sites More sharing options...
TOR4x4 Posted November 28, 2006 Share Posted November 28, 2006 Thus the 2400psi shown equates to 634kg - which is about right for the weight of one corner. one corner??? wow don't you mean one end Quote Link to comment Share on other sites More sharing options...
MogLite Posted November 28, 2006 Share Posted November 28, 2006 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 If you get some numbers - I'll show you mine...... Quote Link to comment Share on other sites More sharing options...
gav- Posted December 27, 2006 Share Posted December 27, 2006 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? Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted December 27, 2006 Share Posted December 27, 2006 'piston contact head' size has nothing to do with it, you need the cross-sectional area of the piston. Quote Link to comment Share on other sites More sharing options...
simonr Posted December 31, 2006 Author Share Posted December 31, 2006 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 Quote Link to comment Share on other sites More sharing options...
gav- Posted January 1, 2007 Share Posted January 1, 2007 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 Quote Link to comment Share on other sites More sharing options...
BogMonster Posted January 4, 2007 Share Posted January 4, 2007 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" Quote Link to comment Share on other sites More sharing options...
bishbosh Posted January 5, 2007 Share Posted January 5, 2007 Simon, That would be the perfect tool for measuring unsprung weight at each corner of the vehicle - just put it on the spring seat and lower the chassis onto it - Bob's your grannies son. Quote Link to comment Share on other sites More sharing options...
Mark90 Posted January 5, 2007 Share Posted January 5, 2007 Except that would be measuring the sprung weight Quote Link to comment Share on other sites More sharing options...
bishbosh Posted January 5, 2007 Share Posted January 5, 2007 Bah, I know what I meant!! Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted January 8, 2007 Share Posted January 8, 2007 Bah, I know what I meant!! Or for unsprung weight measure axle-body and axle-ground and calculate the difference Should be accurate enough for most purposes? Quote Link to comment Share on other sites More sharing options...
gav- Posted January 17, 2007 Share Posted January 17, 2007 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. Quote Link to comment Share on other sites More sharing options...
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