Center of Gravity Measurement
FINDING THE HEIGHT OF THE CENTER OF GRAVITY BY MEASURING WEIGHT CHANGE WHEN TILTING THE VEHICLE:
M
\ Q'
\ \
M \ M Q'
\ c | h \
ang X | \
O-------------------------C----------------------Q
[---------- a ------------]
[------------------------- b --------------------]
b = wheelbase or track O-Q from axel to axel
a = length to center of gravity O-C when level
X = angle of tilt ang QOQ'
h = height of tilt vertically at Q'
c = height of center of gravity above the axel line
M = total weight
W = weight at O
1. W = M (b-a)/b = M (1-a/b)
when tilted through angle X, Q is raised by h and more weight is transfered to O
increasing W to W'
2. b' = b CosX
3. a' = a CosX - c SinX
substitute 2 & 3 in 1
4. W' = M (1 - (aCosX - cSinX)/bCosX) = M( 1 - a/b + (cTanX)/b)
rearranging 1 gives
5. a = b(1-W/M)
substitute in 4 gives
6. W' = M( 1 - b(1-W/M)/b + (cTanX)/b = M( W/M + (cTanX)/b)
solving for c
7. c = (W'/M - W/M) b/TanX =
8. bCotX (W' - W)/M =
9. b^2(W'-W)/hM
To get the center of gravity above ground add the axel height above ground to c.
Richard Gray (c) 97/07/26
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