Slater
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| posted on 20/3/09 at 02:19 PM |
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car weight
During my SVA test the front and rear axle weights was measured using a device in the rollers.
The front axle was 310 kg, the rear was 310kg. No driver, full tank of fuel.
Does this mean the overall weight is 620 kg?
I did ask at the time, he said it's not as simple as adding front+rear, to get an accurate result I would need to take it to a weighbridge.
Why do they call Port Harcourt "The Garden City"?...... Becauase they can't spell Stramash.
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l0rd
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| posted on 20/3/09 at 02:43 PM |
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Nope, It has been posted several times. Do a quick search. This doesn't mean that your car is 620Kg.
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RK
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| posted on 20/3/09 at 03:45 PM |
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Just go easy on the ale for a while.
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Mix
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| posted on 20/3/09 at 04:16 PM |
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Hi
I'm confused ............ accepting that the car may not be in the same horizontal plane when weighing the front and back axles, which will
induce variables, what else would lead to the total weight not being the sum of the front and rear axle weight?
Regards Mick
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02GF74
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| posted on 20/3/09 at 04:18 PM |
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quote:
Originally posted by l0rd
Nope, It has been posted several times. Do a quick search. This doesn't mean that your car is 620Kg.
..... .the reason being?
surely it'll be pretty close, not more ta=han 10% out I'd have thought.
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dinosaurjuice
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| posted on 20/3/09 at 04:57 PM |
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if the car is level when each axle is weighed the total mass will be sum of both axles.
the axles are the only upforce of the car and have to equate the total downforce.
i would love to hear the explanation as to why it would be different..
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DarrenW
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| posted on 20/3/09 at 05:05 PM |
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The equation is (front axle + rear axle) X 1.333
Wow, what a heavy car.
Strangely at my test the SVA man said yyou did add both weights but i cant accept that.
In my mind if the car has perfect 50/50 weight distribution and is on a level pnae then it may be close, but surely there are several factors that
make simple addition innacurate - its just that i dont know what they are. There must be a bit in the middle of the car that is getting weighed
twice.
Weighbridge would seem to be sensible idea, but then there is the issue of how they are calibrated. Some are designed for 20T vehicles, so will be set
to be accurate at those loads ( a bit like a micrometer that should be calibrated with a setting master that is close to the size being measured to
get the most accurate result).
If you go to scrap merchants weighbridge and it comes out at 400Kg, id suggest you dont go there in future if you have any scrap to sell.
Ill guess true weight with full tank and no driver to be between 580 and 600Kg. So close to axle weights.
[Edited on 20/3/09 by DarrenW]
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Hellfire
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| posted on 20/3/09 at 05:07 PM |
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When measured like this your not simply weighing half of the car - the front (or rear becomes a fulcrum) therefore you have an element of
triangulation - using simple trigonometry you can calculate the combined weight. It's not a simple at that as the engine is not forced to be
central etc etc....
It's much simpler using a weighbridge though 
Steve
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Paul (Notts)
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| posted on 20/3/09 at 07:11 PM |
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If they are both on the weighing rollers at the same time then you would add them together.
BUT if only one at a time then the Turning moments get involded and no formula works without knowing the location of the center on mass of the car.
Paul
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Fred W B
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| posted on 21/3/09 at 02:03 AM |
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quote:
if the car is level when each axle is weighed the total mass will be sum of both axles.
i would love to hear the explanation as to why it would be different..
Seconded - If the car is exactly horizontial when each end is weighed the total mass is the sum of the two ends - end of.
If the car is not horizontial you could work it out if you knew the angle the car was sitting at and the wheel base
Judging by the comments this roller device sits the car at an angle - so take a trolly jack and a spirit level with you?
quote:
Weighbridge would seem to be sensible idea, but then there is the issue of how they are calibrated.
You might be suprised how accurate some are, particully those that weigh trucks moving into and out of scrap metal works. If you find one to use,
before you put the car on stand on the scale yourself and peer through the window at the readout - if you know what you weigh you will get a good idea
if the calibration is good.
Cheers
Fred W B
[Edited on 21/3/09 by Fred W B]
[Edited on 21/3/09 by Fred W B]
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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Mix
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| posted on 21/3/09 at 09:10 AM |
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Hi
The issue here is the fact that the car is not in the same condition when each end is weighed and hence the total weight will not be the sum of the
axle weights.
The vehicle does not need to be level to ascertain it's total weight, it just needs to remain in the same condition, (ie if it is 2 degrees nose
down it stays that way throuout the weighing process).
Providing constant condition is maintained the weight can be found with a set of scales used under each wheel individually and the results added
together.
I think some of the previous posters are confusing total weight, (which remains constant no matter what the static attitude of the car is), with
weight distribution, (which is dependant on attitude).
Regards Mick
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mk_xe
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| posted on 10/4/09 at 10:42 PM |
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yup thats right
if you weigh each corner of the car in same position and add up then thats the weight of the car
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