Why does the back of a bus go over a bump so violently but the front of the bus is not impacted the same ??
In: Physics
The weight of the engine at the front dampens the initial movement but accentuates the second bump.
It has to do with the placement of the wheel axles and weight distribution. At the back of the bus, the wheel axle is further forward leaving several feet of the bus extending outwards. Thus, when the bus goes over the bump, the entire back raises up and slams down.
Weight distribution (engine block) and harmonics.
the engine block at the front of the bus holds that end down more.
But also, and possibly more significantly, after the front end bounces from a bump, by the time the back is bounced it’s already swinging a bit, so the bump at the back of the bus is sometimes made extra ~~awesome~~ violent because it’s being amplified.
I do it… I mean… The bus driver does it on purpose to mess with those snotty kids in the back.
I’ll try to explain this as best I can. Let’s say you’re driving along the road with your family. And you’re driving along la li la. And then, all of the sudden there’s a truck tire in the middle of the road. And you hit the brakes. Err! Whoa, that was close. Now let’s see what happens when you’re driving with the ‘other guy’s’ brake pads. You’re driving along. You’re driving along and all of the sudden the kids are yelling from the backseat, ‘I got to go to the bathroom, daddy!’, ‘Not now, damn it!’, truck tire, eeeee, ‘I can’t stop!’. Help! There’s a cliff! Aah! And your family’s screaming ‘Oh my god, we’re burning alive!’ ‘No! I can’t feel my legs!’. In comes the meat wagon. And the medic gets out and says, ‘Oh, my god.’. New guy’s in the corner puking his guts out. All because… you want to save a couple of extra pennies.
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The rear suspension is subject to different loads than the front suspension. The front suspension is softer cause it’s more consistently loaded. Fuel tanks, passengers, and, cargo make up the varied loads and the rear needs to make up for it.
Most buses have the front wheels near the front end of the bus, with the rear wheels more centered. This allows for tighter turns and a consistent load on the front end. The consistent load is important because in case the power steering goes out, the weight of the cargo won’t effect the steering (that’s also why vehicles with larger tires have larger steering wheels).
Think of a bus like a commercial pickup truck for passengers.
The suspension in the front is better actuated than the rear. Most busses have a solid rear axel which does not make for a comfy ride.
You’ll experience the smallest bumps when you’re midway between the front and rear axles. You’ll experience the largest bump when you’re outside the axles (generally possible only at the very back of the bus).
Get a ruler and move it up and down from the 1 inch mark and the 8 inch mark. Note that the 12 inch mark moves more than any other part of the ruler, no matter which “axle” is moving.
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