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Stilt not too late to change

14th April 1978, Page 39
14th April 1978
Page 39
Page 40
Page 41
Page 39, 14th April 1978 — Stilt not too late to change
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The Dodge Drivers Club has been reformed by Chrysler. Membership is open to drivers or mates who work on Dodge Karrier or Commer vehicles, irrespective of the size or application.

Membership is free and includes a free £500 accident insurance policy, low price holidays, free information bureau (I suppose that means service and not one each) and a quarterly newspaper, the Dodge Drivers' Express.

Operators and drivers should keep their eyes open in CM for the membership coupon but, if you're desperate, contact the Secretary, Dodge Drivers' Club, Astral House, 1 7/1 9 Maddox Street, London W1 R OEY.

One thing concerns me the club badge, reproduced here, has unfortunate associations in,

DRIVERS are very much in favour of the extra power manufacturers are putting into their heavy commercial vehicles. It makes their lives easier by cutting the number of times they need to change gear and allows a high top speed.

That's fine if they obey the speed limits, particularly on motorways. The trouble is that if a lorry has the power and is geared to run up to a maximum of 113km/ h (70mph) it will certainly be used at that speed — in fact probably reaching 120km/ h (75 mph) on the overrun. This may speed the driver's journey, but the effects on fuel economy are disastrous. So how do you ensure that a driver keeps to the legal limit on the motorway and so returns a sensible consumption? The answer is probably to fit some form of governor, other than the fuel pump's own, which will restrict the speed. Of course, if the fuel pump is permanently governed, the vehicle will be restricted in all gears and the benefits of the additional available power negated.

In this case the truck will almost certainly be difficult to handle, poor in traffic and more likely to put unnecessary strain on the engine and running gear. What's required then, is a governor which limits the speed in top gear to around the motorway maximum. Such devices are called road speed governors and at present three manufacturers make them in the UK.

Stan Hartshorne, product planning manager for the Cummins Engine Company in Europe, has done a lot of research into road speed governors and his results are very illuminating. Using CM's Scottish road test route profiled on Cummins' computer, and by changing the maximum allowable speed to 113km/ h (70mph), Stan was able to simulate road speed governing by restricting cruise speed to 97 or 105km/ h (60 or 65mph).

For the analysis a "standard" vehicle was used. This was a 4 x 2 tractive un with a two-axled semi-traile Frontal area was considere to be 2.4m x 3m (8ft x 10f and the tyres 11.00 x 22. tubeless radial.

The transmission was Fu ler Road Ranger RTO 9509 with a Rockwell R170 re: axle. Rear axle ratios wet simulated to give gear speec of 97, 105, 113 and 12 km/h (60,65.70 and 75mp1 so that comparisons could made. Gross weight of th kOe.hicie was 32.5 tonnes (3 sons) and the style of drivin was "economy".

In order to allow ampl power for pulling the gears speeds of up to 120km/ (75mph), the American Cun mins NTC 350 was used ; both 2100 and 1900rpm. an alternative, the NT 350BC at 1900rpm an 224kW (300bhp) was als red. A total number of 27 ns was carried out with the roe engine variants. The aph (fig 1) shows the suits of Stan's work and e expected fuel savings.

There is a point on the • aph which needs ex aining. At 113km/h Omph), the fuel consump311 appears better than it ally is. This is because the unputer was holding the 'hide at its pre-set limit of 13km/ h (70mph) instead of lowing it to run out to aximum. Nevertheless, it in be seen that, using the ghicle geared for 105km/h i5mph), at 97km/h iOmph) a saving of 5 per 3nt can be made.

By running the vehicle at 7km/h (60mph) when it is eared for 120km/h P5mph), the saving is an nazing seven per cent. On us basis, Stan Hartshorne trnmed up by saying that the tad speed governor can how fuel economies by tearing fast and preventing to use of that geared speed.

He points out that the ime results can be obtained

y the same fast gearing and

responsible driver or one iho obeys the law. It may be Dssible to override the de ice if the driver is deterlined to find a way. How

ver, with such potential wings to be had, road speed ovemors do seem to make a a of sense.

In addition to fuel savings, tough, the road speed gov rnor is used by operators uch as those running mkers, for safety reasons.

nd a further saving in terms I reduced wear and tear is nether point in their favour.

With this in mind CM took a tok at those available on the ritish market, and how they rork.

The road speed governor rill either have speed sign

ing, where the governor XeS the engine speed accoring to road speed itself or mply controls the fuel pump ick position.

The former is better as it ositively regulates the aeed, while the latter is a ompromise because each idividual vehicle must be set p on level ground running illy laden at its desired laximum speed. Which type IF operation can be had deends on the type of fuel ump fitted to a particular shicle.

Fidus Controls, of 80 Elsrick Road, Newcastle upon Tyne, manufactures an electronic road speed governor which is actuated by a sensor very near to the propshaft flange, accurately determining the vehicle speed.

This data is relayed to an air-operated actuator which controls the fuel pump's supply to the engine and thus regulates speed. It does this only when top gear is selected, by a device attached to the gearbox.

Transport Efficiency Limited of Bridgeman St, Bolton, Lancs markets the Groeneveld Speedlimiter. Operating only in the highest gear, the Speedlimiter can be controlled from either the tachograph or the gearbox. It has a pneumatically operated cylinder in the throttle linkage which allows the speed to be regulated.

The electrical impulse which operates the cylinder is taken from the tachograph speed indicator lamp via a relay and a solenoid valve. Thus speed can be set to a desired maximum. Below this maximum, the throttle rod is at its normal length by having air pressure in the valve, whilst when maximum is reached, air is exhausted and the rod shortened. If a vehicle is not equipped with a tachograph it is still possible to attach the device to a speedo head.

The third device comes from Associated Engineering of Leamington Spa, which also makes the Econocruise electronic cruise control for cars or light vans. For lorries it makes the Econocruise Truck Speed Limiting device. Like the Fidus device, it senses the vehicle's speed via a magnetic pick-up near the propshaft. These signals are relayed to an electric motor which winds the fuel pump control shaft forward or back, depending on the speed of the vehicle.

The cost of the Econocruise is around £300, whilst the Fidus costs about the same. The Transport Efficiency device is some £40 less.

An important point to watch with any road speed governor operating on top gear is that the next gear down will not give a higher speed than top. If it does, the driver will use that lower gear, so the point of the exercise is lost. Also if an air deflector is subsequently fitted to reduce drag, the vehicle will again go faster, so the road speed governor will need to be reset.

For the last few years a great deal of interest has been shown in road speed governors. If they are fitted properly and not by-passed in service, they will 'definitely show operators a fuel saving.

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