What makes a noisy bus ? How to get a quiet bus ??

hseochin SG

30 years ago, was mainly the noisy engines & lousy 3rd party bodies.

Nowadays, 3rd party bodywork have improved in quality but still tend to be a major source of noise irritation, i'll say. Modern engines are much quieter BUT certain types of gearbox & air-con compressors are simply too noisy !!!!
Worse, some use very noisy radiator air intake fans where the fan makes as much if not more noise than anything else on such a bus !

My equation for a quiet bus thus is :
Quiet bus = quiet engine + quiet gearbox + quiet air-con compressor, mainly these factors.

Other helpful features would be full engine & gearbox noise encapsulation, good quality bodywork with no 'loose ends' which squeak, crackle or rattle ! Also quiet air-con blower unit in the interior !

Therefore, optimal matching of these components upon bus purchase would certainly go a very long way towards ensuring the ultimate possible level of quietness, an extremely important component of pasenger comfort !!

I notice that on a bus with quiet engine, the noisest component is some 'ill matched' air-con compressor. Next down the line is some 'ill matched' gearbox.
Much effort can be put in to develop a most quiet engine BUT the passenger may not be able to take notice hence appreciate it much if the quietness is 'spoilt' simply by ill matching with noisy (often non original !!) key components.

For maximum passenger comfort, bus operators are well advised to take note & ensure that the original bus chassi maker 'endorsed' components are always used & to evaluate throughly with high priority on quietness any other component, assuming they already have a bus with quiet engine.

SBS1908B SG

You mean like VSO. Noisy voith, noisy condenser? Not to mention ear-splitting bell. Evil or Very Mad

Windy_hates_B10TLs SG

Easy. Double glazed windows, sound deadening material in the panels. Use Denso air-conditioning… there is nothing like a low pitched hum of a Denso. Also, if you don’t want noise, don’t have hub reduction or a hypoid rear axle. Have an automatic gearbox, since they won’t be noisy. Don’t have an exhaust brake. Etc.

hseochin SG

What i hate most about these models are the extremely noisy radiator air-intake fans they use either in front or on the right side ! The engine itself i believe is quite quiet. Of course the noisy air-con machinary behind next in irritation !! As such the noisy gearbox don't seem so obvious here, probably 'drown' out !

On those 1.5 deckers i've riden on via PlusLiner from KL to SGP, i observe they
also use tranverse engine layout with the air-con machinary piled on top of the engine. But the engine, air-con & gearbox ALL were on the quiet side of things, even @ 100+ km/h speeds on the highway. Scania L94 i believe does NOT use those stupid noisy radiator air-intake fans like Leyland or Volvo, however !
SBST should perhaps sent an investigation team to explore why other's are so much quieter than theirs !

^tamago^ SG

Noisy radiator fan on the right side of the VSO. but it's nice seeing leaves being blown away by the fan, like the O.405G's.

the later VO's also have loud radiators at the front too.

the Voith gearbox only contributes in tis aspect by holding the engine and hence the radiator fan at higher rpm's for a longer time.

Windy_hates_B10TLs SG

Simple solution to the loud fans on the VSOs... put a match to them and *BOOOM!!!!* Twisted Evil Laughing

iveco SG

Most of the noisy buses I know of are front-engined, like the B57, OF1417 and Hino AK. Not forgetting the Bedford school buses.

ZYX2005 SG

the scania l94Ub is (was?) reknown for its quietness. i tried taking SBS2888T on 518 in march 2003. damn quiet when idleing.

nowadays i hear its not as good as when in 2003 or before.

the hippo tours scania L94Ub are not so quiet as the air-con is very noisy. but outside u can hardly hear its engine when it goes by

ZYX

^tamago^ SG

yes. i liked it particularly for its ZF, powerful low-bass engine and the turbocharger whistling its way when the bus was speeding on tampines ave 10 & pie, if u sit at the rear inside the bus. Lance-like, but much smoother.

hseochin SG

But on O 405 G, they don't use those loud sounding 'remote link-up' type of fans as on the Olympians. So what you hear from the engine of the O 405 G is largely the 'real' engine sound, not mainly noisy fan sound !!

That's why the O 405 G's interior (likely exterior also) engine noise levels upon even hard acceleration is quieter than the Olympian's (with their type of fan noise included) since their engines obviously don't work without those fans.

Airbus330Captain SG

VSO’s are not noisy , i find the radiator not as loud the first time they were released on the roads . I really enjoy the sound of the acceleration and it’s a very comfortable bus to ride on.

hseochin SG

Then maybe since then they addressed that issue on some units.
But on all the units i've riden, it remains unacceptably noisy to me, with such fan noise the main irritant. Even hearing from some distance away outside, i hear more of loud fan noise than 'real' engine noise upon acceleration, which makes the entire vehicle unneccessarily noisy to me.

When i consider noisy or quiet, i'm comparing 'across the board' with the quietest buses/coaches i've personally experienced & i don't tend to serparate PSV's into citybuses (which tend to be the noisier lot on the whole) & coaches, which have given me ultimately the quieter rides.

Suspension ride comfort has been improved on the latest Olympians, even from the upper deck. But i'll still don't find it the best in this area. As for enjoying the sound of the acceleration, i find the deaf-silence nature of the V-type engined buses far superior simply in that one hardly senses the presence of the engine (or any other sound) even as the vehicle's quickly & forcibly accelerating !

carbikebus SG

Try to put those buses on everyday revenue services and then you will know Cool

sbs&tibs SG

I find some MK3 quite noisy when they brake. Very irritating.

SBS9828X SG

So ur saying that this is causd by wear and tear? another factor is maintenance... theirs are far better Rolling Eyes

hseochin SG

I do believe those long distance coaches are subject to overall more demanding & stressful operating envirnoment than citybuses.

Like citybuses, both are very well used with little down time.

But in the case of coaches, these are driven mainly on highways for many hours non-stop @ maximum engine speed so temperature & all manner of mechanical stresses are taken to the extreme. Not surprising brakes too have to work much harder to slow down & stop a coach which normally runs @ 2 to 3 times faster than a citybus in slow city stop-start (i.e. more opportunties for the vehicle to 'rest') traffic !!

hseochin SG

On maintenence, based on the condition of the buses i've riden on, i find e.g. Handal Indah's buses better maintained than SJE's !

The_Bus_Guide SG

I feel that citybuses are more prone to wear and tear compared to express buses. That's because citybuses are subject to frequent acceleration and braking due to stop/go traffic conditions. The lower gears puts the most stress on the engine because that's when it will rev the highest. Gearbox are also subject to a higher wear rate due to the constant shifting of gears.

Express buses, although twice as fast as citybuses, are actually cruising on the overdrive. They don't really push the engine to the limit but holds it at mid-range to get the best fuel consumption without compromising on torque and power. As for braking, unless you're reaching a toll booth or there's obstruction ahead, a slight jab on the pedal is sufficient.

Halide SG

Yeah i also agree that citybuses are subject to more tear and wear bcoz of the frequent acceleration, braking and sometimes at the mercy of some ruthless drivers who treat the buses like rally cars. Furthermore, some of these citybuses serve high density routes and therefore commonly operates with full pax load, straining the suspension.

hseochin SG

On the brakes, in the case of citybuses, due to the lower driving speeds, the 'actual' brake pads get used more frequently, i'll say. Compared to outstation coaches where due to the higher driving speeds, more braking tends to be done via retarder or exhaust brakes (if used) & the 'actual' brakes are used only when a low enough speed is reached, before coming to a standstill.
So on brakes, i'll agree the 'actual' wear on the brakes on citybuses can be greater than on outstation coaches.

The various gears in the automatic gearbox for citybuses can also be used more often compared to the gears in a manual gearbox for outstation coaches, where the highest road speed gear tends to be used most of the time.

In both cases, wear on the gearbox can be very high only that its distributed differently. A case of possibly lower wear on each gear but with more gears being subjected to roughly the same level of wear for citybuses versus a case of very extremely higher levels of wear on the top road speed gear with far less wear on the other gears in the same gearbox for highway coaches. Ultimately which ever the case, the gearbox would still require sufficient frequent maintenance. 1 (especially important often used) gear fails even if the other gears are hardly used, the 'productivity' of the vehicle becomes noticibly worsened, which is definitely not acceptable !

Regarding engine operating speeds, i notice the automatic gearbox is programed such that the engine rarely touches & stays for any noticble time @ the maximum speed level. Majority of the time gear changes take place well within the green zone, so the engine doesn't really need to be exerted much to move the bus along. Road speeds are much lower [compared to the outstation highway coaches] implying actual levels of power & torque transmission through the engine, gearbox etc. tend to be much lower than the maximum designed to be handled.

The situation you mentioned below does not happen too often, as (from currently available coaches in use in Malaysia) i observe if you stay in the middle of the greenzone, your (level) road speed only ~ 60 to 80 km/h, too unproductively slow to be maintained for long stretches on the highway ! In order to be twice as fast as citybuses (assume these @ 60 km/h only) the outstation coaches would go @ 120 km/h, which i find quite a normal speed which can be maintained for quite some time on the N-S highway & that's in fact the sort of speeds actually used often from all my trips over the years. So @ 120 km/h, the engine speed is ~ 2500 rpm which is where the red zone starts !! In reality, this is the sort of engine speeds used much (almost all !) of the time on the outstation highway coaches.

The drivers simply want to extract the maximum possible performance from the coach & to appear as productively efficient as possible (to their passengers) so they tend to drive as fast as the driving envirnoment can allow. So this green zone i'll say is rarely observed & mostly it's touching well into the red zone !!
Yet the coaches somehow can withstand such levels of wear, which is definitely very much higher than on citybuses & even seems like 'chickenfeed' in comparison !

In summary i'll say that in the area of brakes, those on citybuses tend to be used much more than on outstation highway coaches while in engine operating speeds hence engine wear/stress levels, the engines on coaches are the ones used much more 'fully', being pushed literally to the end of the line whether on the speedometer or tachometer, which is hardly so in citybuses ! Gearbox wear high in both cases but the high speed stress to the gears on coaches can be worse than merely high use (but lower speed) stress on citybuses.

So from these factors alone, my deduction is that citybuses are subject to less overall stress hence less overall wear & tear than on outstation highway coaches. If the coaches were driven @ citybus levels of speed mostly, then the citybus would be the ones more subject to wear & tear i'll think.