Mon­sters’ thrall

The Courier-Mail - Motoring - - Big Wheels -

THERE is some­thing about mon­ster trucks that captivates young kids, es­pe­cially boys.

Just ask par­ents who have shelled out for tick­ets to the Mon­ster Jam shows in Bris­bane, Mel­bourne Syd­ney and Perth this Oc­to­ber.

Some kids are sim­ply ob­sessed with some­thing that has such big wheels, while many oth­ers have an ap­petite for the de­struc­tion these ma­chines wreak.

Many par­ents, in­clud­ing this writer, have been drawn into the world of mon­ster trucks through their kids (OK, I con­fess, I was fas­ci­nated as a child too).

The wan­ton de­struc­tion and the lack of me­chan­i­cal sym­pa­thy on dis­play dur­ing the freestyle ses­sions, which few trucks sur­vive in­tact, can grate with adult automotive en­thu­si­asts.

How­ever, the en­gi­neer­ing in­volved in build­ing trucks that can per­form stunts such as a com­plete back­flip and keep driv­ing can’t be any­thing but im­pres­sive.

The Mon­ster Jam trucks are built on be­half of the se­ries pro­moter and share the same ba­sic con­struc­tion of a su­perthick tube frame that is built to cope with mas­sive stresses.

They all run 1.7m tall tyres that were orig­i­nally de­signed to tra­verse farm­land. Each team cuts the tyre tread down to make the trucks han­dle bet­ter.

There are oc­ca­sional punc­tures but the tyres are durable given the forces in­volved and some of the me­tal they hit, such as wrecked cars.

Mon­ster trucks run mas­sive oil and ni­tro­gen filled shock ab­sorbers (two per wheel) plus springs, that work hard to ab­sorb the forces gen­er­ated by jump­ing a five-tonne truck. The huge tyres also com­press on im­pact and re­bound, caus­ing the trucks to bounce up in the air (of­ten with spec­tac­u­lar re­sults). To jump so far into the air and do wheel­ies on de­mand, the trucks need a lot of power.

This is taken care of by an all- alu­minium 9.4-litre Mer­lin motorsport su­per­charged V8.

Run­ning on po­tent methanol fuel, also used by top speed­way and drag rac­ers, the en­gines pump out an in­cred­i­ble 1120kW and turn old-school two-speed Pow­er­glide au­to­matic trans­mis­sions.

The main ap­peal of mon­ster trucks is on show in the freestyle com­pe­ti­tion, in which driv­ers win points for the most spec­tac­u­lar jumps, rolls, donuts and crashes, but there is also a rac­ing com­po­nent.

Mon­ster Jam trucks are not ag­ile when it comes to the tight turns of the race cir­cuits, which are con­fined to sports grounds, but they are sur­pris­ingly fast.

In fact, the team that runs the iconic Grave Dig­ger truck in­sists it is a smidgeon faster from 0 to 48km/h on dirt than a Nissan GT-R on dry bi­tu­men, com­plet­ing that dash in just 1.52 sec­onds.

Hus­tling a mon­ster truck around in an en­closed space like an arena is not easy. They have rear-wheel steer­ing to re­duce the oth­er­wise vast turn­ing cir­cle.

The locked rear dif­fer­en­tial keeps both rear wheels turn­ing at ex­actly the same rate — this would make turn­ing on tar­mac ex­tremely dif­fi­cult but ac­tu­ally al­lows for bet­ter cor­ner­ing on dirt be­cause the rear wheels start slid­ing straight away.

One of the key el­e­ments that helps cre­ate spec­tac­u­lar mon­ster truck ac­tion is track de­sign. The type of jump, in­clud­ing the an­gle and the shape, en­able par­tic­u­lar tricks. One style of ramp en­ables driv­ers to at­tempt back­flips, which are now fairly com­mon in Mon­ster Jam shows.

James Stan­ford

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