ME 485/585 Vehicle Design S09 H1 Pg 1 of 1
1. Given a truck whose wheelbase is 130 inches long and its static front and rear axle loads are
2500 and 1500 lbs respectively, find the distances from the front and rear axles to the CG.
2. A vehicle has its front axle located 35 inches in front of the CG. Determine an appropriate
wheelbase to provide a 60/40 front/rear weight distribution.
3. Given a vehicle whose static front and rear axle loads are 3500 and 1000 lbs, center of gravity 25
in. high and wheelbase of 125 in, calculate the weight shifts during acceleration for the following
table values of ax/g. Assume that insignificant aerodynamic drag, rolling resistance, and or hitch
loads and that the vehicle is on level ground (grade=0%). Report the results in a table similar to the
one shown below:
ax/g Wf (lbs) Wf / W (%) Wr (lbs) Wr / W (%)
0.1
1.0
2.0
3.1 Determine how many g’s are required for this vehicle to do a “wheelie?”
3.2 Assume that the vehicle has a typical spring damper (i.e. shock absorber) suspension. What
generally happens to the vehicle's pitch angle during large accelerations?
3.3 What happens to rear axle traction forces during braking? Does weight shift help or hinder the
braking process (tricky question)?
4. Assume that an ATV is driving up an incline at a constant velocity. Ignore aerodynamic drag,
hitch forces and rolling resistance. The vehicle’s static front and rear axle loads are 350 and 250
lbs. The center of gravity is 20 in. high. The wheelbase is 60 in. Also ignore the weight of the
driver.
4.1 What grade angle would cause the ATV to pitch backwards or flip over when going uphill?
4.2 What grade angle would cause the ATV to pitch forwards or topple over when going downhill?
4.3 When descending a hill, assume that there is sufficient run-out at the bottom. Would stepping
on the gas decrease the likelihood of pitching forward over the handlebars?
4.4 What actions can the driver take to prevent flipping backwards while climbing? Or toppling
forwards while descending?
4.5 What design guidelines, with respect to CG/axle location, might you recommend for ideal ATV
hill climbing and descending (tricky question)?
5. Use the Gradeability Spreadsheet (from website) for problem number 3 on page 15 of your text
that presented in class. Experiment with different values to answer some of the following
questions:
5.1 Use the spreadsheet to calculate the maximum grade angles for FWD, RWD and 4WD vehicles,
by iterating or using Excel’s “Solver” feature.
5.2 Compare the grade angles of the approximations determined in that textbook versus the exact
formulas as calculated in the spreadsheet (i.e. calculate % error) ?
5.3 Determine the maximum grade angle for each of the vehicle types under conditions of moderate
snow or ice when the friction factor is equal to 0.1?
5.4 Determine the maximum grade angle under conditions of dry pavement when the friction factor
is equal to 0.8?
5.5 How would the traction performance be affected if the hitch point was lowered?
5.6 For all van drive types (i.e. FWD, RWD and 4WD), determine the general effect on the van’s
gradeability caused by shifting the trailer's center of gravity forward, such that the tongue weight is
increased, when going uphill? When going downhill?
6. Explain where to concentrate a vehicle’s weight for good gradeability (i.e. FWD, RWD &
