Behind the wheel of a Scania prime mover. Halleluyiah! - Daily Nation

Behind the wheel of a Scania prime mover. Halleluyiah!

Tuesday July 24 2012

By BARAZA JM

If you have ever looked at a prime mover and wondered what it would be like to drive, believe me; it is exactly what you thought.

It requires skill, it requires concentration, it requires a good sense of geometry and perspective (people with impaired vision or judgment need not apply) and it requires a tremendous amount of testosterone if the driver of the said prime mover intends to get anywhere on time.

I cannot declare with any amount of confidence just how much of each of these qualities applies to yours truly, but that did not stop me from trying my hand out in a Scania truck.

Now, you cannot just up and drive off in a Scania, especially if you have never been in the particular model you are trying to TWOC. You need training. You need coaching. You need familiarisation. You need to go to school: The Scania Drivers’ Training Academy Of Current And Prospective Heavy Commercial Vehicle Helmsmiths.

That is not its real name, but a Scania training school does exist on the Kenya Grange Vehicles premises, and I attended a crash course before slinging myself into the pilot’s perch.

At the school we learnt the general layout of a Scania cockpit. We discussed engine brakes, exhaust brakes and retarders. We discussed turbochargers and intercooling heat exchangers. We discussed off-set angles of 89.997 degrees between crown wheel and pinion wheel in the rear differential as opposed to the normal 90 degrees. We discussed diff locks. We discussed about 310hp 5-cylinder engines and 420hp 6-cylinder engines and 730 hp V8s.

All this was familiar ground for me. I was in my element, talking shop with Mwalimu The Teacher and losing everybody else as the talk became increasingly soaked in mechanical jargon and the quotation of figures with several decimal places. We were on a roll. We discussed optimum operating rev ranges and fuel economy, including how it is affected by exhaust gas recirculation in the engine. And we discussed clutch systems.

Then there was talk of something called OptiCruise© and turbocompound engines, and this is the point at which I threw in the towel. I, too, fell by the wayside on the Road of Engineering Intelligence and the lesson ended.

Sweden Special: The Secret To Scania Dominance

OptiCruise© is a feature unique to Scania vehicles that ensures the ultimate comfort and ease of operation for any driver operating a Scania. In a nutshell, it softens up all the controls with electric and hydraulic powering systems and prevents damage or abuse by limiting revs on take-off and disallowing mis-shifts (early downshifts or short shifting upwards).

In semi-automatic models, it allows the driver to choose between auto and manual, and in manual mode, gear changes can be made, Tiptronic-style, without using the clutch. Skipping gears is also allowed, within reason, among other things. Turbocompound engines are turbocharged engines with a unique twist.

After passing through the turbocharger’s exhaust turbine, it so happens that the exiting mixture of combustion by-products still has some energy in the form of momentum (who knew?). The Swedish don’t believe in wastage, so this exhaust mass is channeled into the “turbocompound” device (I cannot, for the life of me, fathom what this is) which is somehow connected to the propeller shaft, and it is this compounding of the turbo setup that give Scania trucks and buses their astronomical torque figures (up to 3500 Nm in the 730hp V8 truck) and hard-to-believe hill-climbing ability; making molehills out of mountains, figuratively speaking.

To understand what I’m saying, get on board a Scania bus (Nyamira Express and the like) and witness the driver monster everything in his path on any steep uphill section. All this with class-leading fuel economy to boot.

Drive Time

With the lecture over, it was time to get practical, and I jumped into a P360. It has an eight-speed gearbox, and a 360hp 12-litre engine. It had no fuel, so I jumped out again, this time into an R420 Topline: the biggest, baddest tractor Kenya Grange Vehicles Ltd will sell any prospective Scania client.

After a three-foot climb off the ground, you wind up behind the controls and you may or may not notice a few things. First, the driver’s seat bounces up and down adjusting itself to the driver’s weight.

The pneumatically powered steering wheel adjustment allows for an infinite permutation of rake (fully vertical to fully horizontal and anything in between), reach (almost flush against the dashboard to almost flush against the driver’s chest and anything in between) and height (down at the driver’s knees to up at eye level and anything in between).

Depending on which R420 you are driving, there may or may not be a gear lever (fully manual or semi-automatic) and there may or may not be a clutch pedal (semi-automatic or fully automatic). My own ride for the day had both a clutch pedal and a gear lever (fully manual).

Shut the door, fire up the 12-litre turbocharged 420hp 6-cylinder engine and let it idle for a few minutes as the air pressure for the brakes build up. Then clutch in, brakes on, off with the parking brake and grab the gear lever; then realise you should have been paying attention in class.

The R420 has a 12-speed gearbox. But it is not as simple as 1,2,3,4 up to 12. No. The basic gearbox is actually a three-speed.

First is in the middle and down, second is up and to the right, and third is down and to the right, south of second. Add to this a reverse gear (up and to the left) and a crawler gear (down and to the left, south of Reverse) and you wind up with a cog arrangement that is close to the H-type common to typical manual transmissions, only this time instead of being an H, it looks like the stick figure of a three-legged animal with two heads, one at each end of its body.

Confusion ensues for the less-than-attentive.

More confusion follows when trying to fathom how three speeds turn into twelve. First there is a range divider, sort of like a 4WD car, with High and Low ranges for the primary gearbox. To switch between high and low, there is a switch on the shaft of the long-ish gear lever. So in Low range, we have gears 1,2 and 3. Flip up the switch and 1 becomes 4, 2 becomes 5 and 3 becomes 6. Anybody who knows the F330 bus will understand.

To create 12, there is also a gear splitter, this time operated using another switch, this time on the shift-knob, thumb-operated.

The gear splitter splits the six individual gears again into high and low, so six times two equals twelve. This is how to shift.
With both switches in the low position, clutch in, snick the lever into 1. That is 1 Low (first gear). Clutch out. Drive. When its time to shift, flick the thumb-operated splitter switch up to High, clutch in, listen for the pfft-pfft of the hydraulics working to change range (don’t move the gear lever) and declutch. You are now in 1 High (second gear).

Flip back the splitter switch down into Low, clutch in, shift the gear lever into 2, and declutch. That is 2 Low (third gear). Splitter up, clutch in, don’t move the main lever, pfft-pfft, declutch, 2 High (fourth gear). Splitter down, clutch in, lever into 3, declutch: that is 3 Low (fifth gear). Splitter up, clutch in, pfft-pfft, declutch, that is 3 High (sixth gear).

Now to go into seventh. First flick down the splitter into Low, then flick up the range divider, the one on the lever shaft. With the range divider in the High position, this means 1 is now 4. Shift the lever from 3 back to 1 (now 4). With the splitter in Low, this means you are now in 4 Low (seventh gear). Repeat as above into 4 High, 5 Low, 5 High, 6 Low and 6 High, which is twelfth gear. All this has to be done in rapid succession, seeing how the driver has a 1300rpm operating rev range (from 500 to 1800rpm). Sounds like a headache, right?

It is, especially when people keep cutting you off in traffic. A particularly nasty chicane in the shifting pattern is when somebody suddenly forces you to slow down just after you have gone into seventh, and so you need to return to sixth.

Without enough practice you will end up fumbling like I did; with Mwalimu the Teacher patiently telling you that you are in the wrong gear (“That is eleventh. Now that is fifth. That is ninth. Now that is fifth again. You have gone into first. Nope, that is not seventh, there is no gear there…”) as you struggle with the lever and the switches and the idiot of a cameraman is behind you laughing like a drunken hyena whilst filming your every mistake.

Get it right, however, and progress is smooth, and sweet and sublime. The cabin is quite comfortable and remarkably quiet with the windows up, more so given that I was driving a used ex-UK vehicle. With three levels of suspension (chassis, cab and seat are all softly sprung) it is a bit bouncy on rough roads, but a nice sort of bounciness.

The power assistance of the tiller makes for an effortless turning experience, and though the ratios in the steering box are much higher than in smaller cars, application of lock is intuitive: from the very beginning you just know how much to turn the wheel so as to get the desired change in direction.

The R420, when unladen, pulls hard. That lengthy description I’ve given on how to change gear is a marvel to watch when someone experienced (such as Mwalimu The Teacher) is doing it, and the acceleration is impressive for something with such a huge face as the R420. From fourth gear (2 High) upwards, there is a muted but distinct whine, the whistling of the turbo wastegate as the blower comes into action, increasing in pitch with more revs and it sounds oh so wonderful for petrolheads like me.

The Important Stuff

Any fleet operator of commercial vehicles will tell you they always look at reliability, performance and fuel economy (not necessarily in that order) when choosing their dray horses.

The turbocompound mechanisms ensure performance and fuel economy. Scania Support offers maximum uptime if and when your Scania vehicle breaks down, which will be rarely because, one, Scanias are superbly engineered to begin with, and, two, driver madness such as over-revving, unwise gear selection and clutch abuse is counteracted by the OptiCruise© system.

The Boring Stuff

Over and above good power and reliable torque, and economy, Scania engines also offer compliance to emissions standards (Euro V and Euro VI). That is stuff we don’t care much about on these shores, but it matters a lot over in Europe where Scanias are bought on a scale similar to that of Kenyans buying beer on a Friday evening at month’s end.

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