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Bus stability

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Bus stability

A couple of hours ago I went down to Halfords on the bus.
The bus was a double decker and I got to thinking if everyone who got on the bus went upstairs and it filled up with no-one downstairs would the bus be much more unstable.
With an average empty bus weight of 7 tons we add approximately 3 tons of passengers to the top deck.
That sounds a bit unstable to me Undecided
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Re: Bus stability

Fit all buses with 1 cubic centimetre of neutron star core at axles, it will stop Strat's concerns.
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Re: Bus stability

Double deckers have to be able to tip at 45 degrees without falling over before they're even allowed off the production line.


Must be said though, I don't think I'd want to be on the top deck during one of those tests!
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Re: Bus stability

that is without passengers - add 7 tons on the top deck and it would fall over
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Re: Bus stability

Most buses are equipped with self levelling air suspension, and do not "lean" significantly on bends. If you see a bus parked on a steep camber road you may notice it is pretty much upright, only after several hours when the air reservoirs drain off do they take on a lean, but quickly straighten up when the engine is run. Normally this is only seen in bus depots with buses that have stood unused for several days.
Other than that, the weight distribution of modern buses is very low down in the chassis.
The only time they may become alarming is in high side winds, but is unlikely to be a real problem.
However, having said that, in the hands of a mad stupid driver it is possible to turn a double decker on to its side on a sharp bend, and happened around this area some years ago, I remember seeing photo's of it in a local newspaper....an empty school bus.
You may remember early films of double decker LM and Routemaster buses on skid pans being cornered at high speed when the outside wheels left the ground, but they couldn't be made to turn over.
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Re: Bus stability

Quote from: Oldjim
that is without passengers - add 7 tons on the top deck and it would fall over

You'd think so but all this stuff is tested before hand.
A relative of mine used to be a bus driver many years ago and I put this to him once - his answer was that it wasn't a real issue because the centre of gravity is so low on them. I think he also mentioned something about large water tanks being fitted and filled for the tipover test but can't be sure.
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Devonian
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Re: Bus stability

Did somebody mention a low centre of gravity?
TORPC
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Re: Bus stability

How can one unsee what has been seen ?Huh
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Re: Bus stability

I wonder whether or not the bike stays on the ground when the rider stands up Undecided
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Devonian
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Re: Bus stability

I thought I looked cool on my bike.  Cry
TORPC
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Re: Bus stability

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Re: Bus stability

I am a bus driver, the average weight of a single deck bus is 7.2 tonnes. Average weight of a double deck bus is 9.6 tonnes. Which implies the top deck only adds 2.4 tonnes. With sixty people upstairs, weighing 4 tonnes, that still leaves in excess of one tonne extra on the bottom deck as ballast.
nanotm
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Re: Bus stability

the only problem with the test's are they don't take into account the annoying brat who would be chirping happily and bouncing about like a possessed loon
unlike all the older wiser and considerably more scared people who would all be too busy staying dead still and praying for a return to normal driving position .....
of course that's totally ignoring the fact the entire test is somewhat strange considering roads don't actually have a 45 degree camber in London .....
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Re: Bus stability

Quote from: nanotm
of course that's totally ignoring

you?
As for london, it isn't the only place on earth and yes I've been on double deckers that do tip over pretty substantially on country lanes so the test is not pointless.
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TORPC
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Re: Bus stability

There are several different reason(s) why the tests are carried out
I may not name then all
That said
Here are two that contains various situations that could cause a DD to tilt
1. Mother nature can & does cause no end of safety issues for all modes of transport, especially via extremely high winds going over bridge(s)
2. Accident(s) caused by the driver or other vehicles etc