Vibration data of buses 1

[ariky]

For ergonomic research concerning driving buses I'm looking for data about vibration transferred from the road to the bus (and further into the driver's seat). Can anybody provide any information (such as frequency range, accelerations)or direct me to any website containing the above.
Many thabks

 

[rob768]

The wheels and suspension more or less will filter out any but the very low frequencies. what's left will be related to resonance of the bus on it's springs which wil be excited when driving over bumps, holes and objects on the road. The magnitude of those will depend on speed, the "impact" from driving over such objects and the damping of the dampeners.
Engine vibration will be submitted to the drivers seat though.

 

[IRstuff]

That'll depend on the bus. Most city and passenger busses are pretty good, but not school busses. Even then, the long distance passenger busses have special suspensions for the driver's seat, so it's pretty obvious that the time-integrated vibration/shock is still too high for the drivers' butts coming directly from the flooring.

You might have a look at MIL-STD-810F for some vibration profiles. Also, ISO-2631.

TTFN

 

[ariky]

Thanks for those responding. I've read a UK survey from November 2000 that found vertical accelerations with city buses of app. 0.6 m/sqr.sec.(rms). Does any have other figures (even approximations).
To IRstuff, I've looked into MIL-STD-810F (it is about consideration for laboratory tests)and found no figures; can you direct me.
Many thanks

 

[GregLocock]

Check out relevant literature by Griffin

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

Did you look at Method 514?

TTFN

 

[Rob45]

ariky:
Concerning that level of vibration, .6m/sec.^2, or .06 G:
what you'll find is that the other factor in seat-base vibration is the frequency.
For example, .06G acceleration at 20 Hz would be perceived as quite rough, quite a lot of vibration, while the same level of acceleration at 200 Hz would be considered quite smooth, an insignificant vibration level.
I'm basing this on my experience in heavy trucks, comparing test data to customers' perceptions, and also to a "vibration computer" sliderule furnished by Endevco.

As you might have guessed, wht people really notice is vibration velocity, not acceleration, and a good rule of thumb (or sliderule, in this case) is that the vibration velocity should not exceed about .15 inches per second.
This figure also agrees well with an internal standard that the Eaton Corporation use.

 

[rob768]

I have absolutely no experience in measurements of vibrations (levels or frequencies) in buses, but isnt what you're saying, 0.06 g, extremely low? I assume that that applies on a flat road, and refers to trasmitted engine vibrations only?
The one time i travel with a bus, my experiences are different..

 

[Rob45]

Yes, that's a low vibration level, from the standpoint of structures, but it's high from the standpoint of annoyance.
And you wouldn't want an annoyed bus-driver, now would you?

 

[GregLocock]

ISO have standards for whole body vibration for humans. I suggets you have a look at them.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rmw]

I have a couple of hundred thousand miles under my butt driving a bus. I deliberately did not get the new "S" endorsement so that I can never be asked to drive a school bus again. Nothing but motor coaches.

Your problem depends upon whether the suspension is spring, toralistic, air bag or something else.

And then if it is a pedestal seat, spring suspension seat, air suspension seat, with or without shock absorber or other.

As an Eagle bus driver, I did not know that road vibrations could be transmitted to the drivers seat, although I did once have to align the miter box to the engine to stop a vibration there caused by misalignment.

I have always wanted to put an air ride seat like the 18 wheelers have but never could justify the expense because the std seat (spring/shock) is so comfortable.

rmw

 

[ariky]

Thanks for all,
1. For your info. vibrations at 3 - 5 Hz are very harmful to humans' back (this is one of the main reasons for WBV-Whole body vibration which causes low-back disorders).
The acceleration figure I've mentioned before (o.6 m/sec.^2))refer to that frequency range.
2. Such vibrations are transferred from the road through the wheels and the suspension system to the chassis and to the driver's seat; inferior or malfunctioned vehicles' suspensions and/or seats suspension, transfer those vibrations.
3. Engine vibrations cause higher frequency vibrations which are of no interest to me.
4. IRStuff - many thanks for the directions you gave; anyhow the info within Method 514 wasn't helpfull.
5. Greg:
5.1 I don't have a handy Iso 2631 copy (this is the relevant standard);I'll have to check with a local liberary (maybe you know whether the relevant data is available on the web; f.o.c.).
5.2 What literature by Griffin (M. J. ??) do you mean and where is it available on the net (I've only found and reached titles of several articles but didn't reach the articles themseleves)
Regards
Arik

 

[GregLocock]

I doubt it is available on the net. Yes, MJ Griffin, ISVR, in the UK.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.