Mak­ing a grand en­trance

There is more to a bus door than just open­ing and clos­ing. SMC Bus Doors ex­plains the in­tri­ca­cies and in­ner work­ings of its mod­ern bus door that com­bines func­tion­al­ity with the lat­est in safety and op­er­a­tion sys­tems


There will be many fa­mil­iar faces grac­ing the stands at the QBIC Aus­trala­sia Bus & Coach Expo on the Gold Coast this month, but few will have seen as many bus ex­pos as Dar­ryl Wil­son, OEM sales man­ager for pneu­mat­ics spe­cial­ists SMC Bus Doors, a divi­sion of Ja­panese-based global pneu­mat­ics giant SMC.

Wil­son started out in pneu­mat­ics in 1981, when he was 21, and has been with SMC since 1997. He’s al­ways had a love for work­ing with elec­tron­ics and pneu­mat­ics, which he de­scribes as a “sim­ple tech­nol­ogy that al­lowed me to de­sign things with­out need­ing to be too com­plex”.

To­day, SMC man­u­fac­tures around 90 per cent of all bus doors on route buses in Aus­tralia, and it’s all done lo­cally. Its Cas­tle Hill man­u­fac­tur­ing fa­cil­ity in Syd­ney’s north-west em­ploys more than 150 full-time staff, in­clud­ing 18 en­gi­neers.

The SMC stand will fea­ture a minia­ture work­ing bus door, and show­case a ag­ship new fea­ture de­signed to vastly im­prove safety and com­pli­ance to the coun­try’s strictest reg­u­la­tions, as well as a re­de­vel­oped and much smarter sen­si­tive edge.


The need for a bet­ter sen­si­tive edge in bus doors arose af­ter a se­ries of en­trap­ments, in­clud­ing a tragic fa­tal­ity in Syd­ney in 1994 when a ve-year-old girl’s foot be­came trapped in the bi-fold­ing rear door of a bus. While each state and ter­ri­tory has its own reg­u­la­tions con­cern­ing safety stan­dards, NSW brought out the high­est specications: NSW TS146 and TS147 (com­monly known in the in­dus­try as RTA146 and RTA147), which gov­ern re­quire­ments for door safety sys­tems and driver’s vi­sion re­spec­tively.

In the case of en­trap­ment is­sues, TS146 re­quires that bus doors de­tect if a per­son or ob­ject is caught in a door, pre­vent the bus from mov­ing if such a de­tec­tion is made, and not ap­ply a clos­ing force greater than 150 New­tons. Ad­di­tional rec­om­men­da­tions in­clude that the bus door should au­to­mat­i­cally re­open if de­tec­tion is present, that the bus’s stop brake be au­to­mat­i­cally ap­plied when­ever the driver has opened the doors, and that the door should de­tect down to 20mm, the ap­prox­i­mate width of a child’s wrist. Wil­son says he’s proud that SMC’s re­designed doors do all this and more.

De­vel­op­ing a more sen­si­tive sen­sor sys­tem within the rub­ber edge of a bus door wasn’t easy. The vast ma­jor­ity of route bus doors these days are glid­ing rather than bi-fold­ing. They open in­wards in an arc, and usu­ally fea­ture a handrail built onto the door. The chal­lenge with the arc sys­tem is that the an­gle of the door edge is al­ways chang­ing in re­la­tion to any po­ten­tial ob­struc­tion, mean­ing the sen­sor might not be trig­gered if the con­tact oc­curs at the wrong an­gle. The new de­sign has solved this prob­lem, mean­ing the edge is now sen­si­tive at all an­gles.

“We also have to have it sen­si­tive to the very bot­tom, which is quite a chal­lenge,” Wil­son says. “It needs to sense a child’s foot, so we’ve got to ef­fec­tively rest it on the step.”

The re­design also al­lows for eas­ier re­moval or re­place­ment, and fea­tures an ad­vanced seal­ing, with an over­lap­ping lip on the lead­ing door­leaf to pro­vide bet­ter pro­tec­tion from the weather and keep­ing out noise.


Much thought also goes into the ac­tual me­chan­i­cal work­ings of the bus doors. A pneu­matic/elec­tronic sys­tem is at­trac­tive eco­nom­i­cally to bus builders be­cause it can plug di­rectly into the al­ready avail­able com­pressed air used for the air brakes and air bags.

The pneu­matic com­po­nents within the door sys­tem are op­er­ated elec­tron­i­cally. An ac­ti­vated so­le­noid will put air into a valve, which changes the di­rec­tion of the cylin­der.

The ac­tu­a­tor sits on top of the door and does its magic from above (hence

the need for a minia­ture door at the expo, oth­er­wise you wouldn’t be able to see the good stuff).

Com­pressed air goes in one side of the ac­tu­a­tor, push­ing ex­haust air out the other side. The speed the door opens or closes at is con­trolled by the rate of com­pressed air com­ing out, mean­ing pneu­mat­ics can achieve smooth, steady move­ment.

The al­ter­na­tion of high and low pres­sure at the right time is crit­i­cal for the SMC sys­tem to work and achieve op­ti­mum safety. When the bus is trav­el­ling at speed, the doors will be un­der high pres­sure. When the bus stops, the doors open un­der high pres­sure (to give sta­bil­ity to the handrails), but close un­der low pres­sure. The low pres­sure re­mains un­til the bus starts mov­ing, where a speed sen­sor in the bus then sig­nals the door to switch to high pres­sure. It’s all de­signed with sim­plic­ity, safety and efciency in mind.

“I think we’re world lead­ers in the amount of tech­nol­ogy we’ve put into this,” Wil­son says. “NSW TS146 may get in­creased to an even higher stan­dard with NSW TS155 due for im­ple­men­ta­tion in Jan­uary 2018, so we’re do­ing a lot of re­search and de­vel­op­ment on that and will be dis­play­ing some of our im­prove­ments at the up­com­ing bus show.”


Hav­ing a huge, global par­ent com­pany denitely has its ad­van­tages when it comes to ma­te­ri­als.

With SMC prod­ucts often be­ing used in the tough­est en­vi­ron­ments, in­clud­ing min­ing, the com­po­nents that go into mak­ing the pneu­matic bus doors are in­dus­trial grade, and should last the life­time of the bus, so long as they’re ad­justed and main­tained to SMC rec­om­men­da­tions.

Wil­son has a ser­vice van full of spare parts al­ways on the go. The re­cently im­proved ware­house and dis­patch sys­tem im­ple­mented by SMC across its na­tional net­work has also im­proved de­liv­ery times for parts.

Build­ing a good re­la­tion­ship with body builders has also been para­mount to SMC Bus Doors’ growth, says Wil­son. The three ma­jor body builders in Aus­tralia all use SMC on their low-oor route buses.

It’s about nur­tur­ing a partnership, ac­cord­ing to Wil­son.

“We might do the con­trol sys­tem or the body builder might do it,” he says. “Then you’ve got the in­ter­face with the body and the in­ter­face with the chas­sis. There’s quite a lot go­ing on, for ex­am­ple a dif­fer­ent chas­sis with the same body may give us chal­lenges in door height.”

Flex­i­bil­ity is al­ways re­quired, as lo­cal bus builders pride them­selves

The SMC stand will fea­ture a minia­ture work­ing bus door, and show­case a flag­ship new fea­ture de­signed to vastly im­prove safety…

on be­ing ex­i­ble for their cus­tomers’ needs. It’s their main ad­van­tage over im­ported buses.

“We de­velop all our prod­ucts in partnership with the body builders, and that means be­ing able to adapt to dif­fer­ent re­quire­ments and work through so­lu­tions,” Wil­son ex­plains.

But body builders are gen­er­ally stan­dar­d­is­ing their bod­ies. They’ve had to im­prove their pro­cesses, and SMC has done the same, he adds.

“The body builders have the same chal­lenge: man­u­fac­tur­ing in Aus­tralia,” Wil­son says. “We’ve al­ways tried hard to keep our costs down, and it’s a very big chal­lenge, par­tic­u­larly with the high labour costs in Aus­tralia. But we’re a pos­i­tive com­pany, we care about the in­dus­try and we’re al­ways go­ing to be there.

“We pride our­selves on buy­ing and pro­duc­ing Aus­tralian, and I hope the op­er­a­tors con­tinue to buy Aus­tralian.”

Wil­son says he hopes state gov­ern­ments will reg­u­late for

Hav­ing a huge, global par­ent com­pany def­i­nitely has its ad­van­tages when it comes to ma­te­ri­als

Aus­tralian con­tent in the fu­ture, given that they con­trol the buses and hand out the con­tracts.


Wil­son says he’s look­ing for­ward to chat­ting to any­one who stops at the SMC stand, and demon­strat­ing the new door in ac­tion.

“With the sen­si­tive edge, we fore­saw an is­sue and had to solve it. It wasn’t easy. We had a cou­ple of goes at it and came up with some­thing re­ally good. De­sign­ing some­thing, putting in a con­trol sys­tem, then see­ing that come into fruition and op­er­ate as a pub­lic ser­vice, there’s a re­ward in that.”

Be­low: A lot of plan­ning goes into the de­sign of the bus doors Op­po­site page: Wil­son with a demon­stra­tor model; Where the magic hap­pens

Above: The SMC Pneu­mat­ics premises

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