CONTROLLING MAXIMUM SPEED BRINGS FUEL SAVINGS
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by Tony Wilding
MIMeChE, MIRTE MANY OPERATORS concerned at the reduced fuel economy and higher rate of wear on vehicles driven for long periods on motorways will welcome a device that controls maximum speed without impairing performance lower down the scale. Although reducing ,engine governed speed can sometimes save Thel it cannot be the full answer for trucks because of its effect on general performance. But now a unit which does not affect 'formal performance but keeps vehicle speed to a predetermined maximum is available in this country.
This is the AE Road Speed Regulator imported from America and marketed by AE Auto Parts Ltd with a registered address of Forster Square, Bradford. The work of adapting the unit for British vehicles and so on is based at the Bradford factory of Hepworth and Grandage which is, like AE Auto Parts, a member of the Associated Engineering Group, and recently I visited this company to try out a vehicle fitted with the regulator. A 47-mile route was covered with the truck—a Leyland Super Comet four-wheeler—in the empty condition and then laden to a gross weight of almost 15 tons, runs being made first with and then without the regulator in action.
These tests showed that the device improved fuel consumption to a worthwhile extent—about 16 per cent unladen and 10 per cent laden while there was only a relatively small drop in average speed. The accompanying panel shows the results obtained on these tests. The route used included a hilly motorway section and about 20 miles of heavily trafficked main roads.
The AE Road Speed Regulator consists of one operating unit with an associated spring-loaded linkage system to the fuel pump or carburetter—the system can be applied to both types of power unit. The regulator is an electro-mechanical device incorporating a centrifugal governor assembly and is interposed in the speedometer drive. The flexible connection from the regulator to the fuel pump or carburetter ends in a component which houses a spring-loaded piston; the casing is connected to the end of the normal throttle-control linkage with the fuel control lever attached to the movable piston.
In this way the normal action of the accelerator is unaltered except when 'a preset speed has been reached. Then the regulator takes over control of the fuel pump or carburetter lever and reduces the fuel delivery. As the power requirement varies due to terrain and so on, the regulator senses changes in road speed and the control is moved in a direction to allow the linkage to open or close the "throttle" for an increase or decrease in demand. Regulation and correction is constant to maintain the preset maximum road speed (with full throttle maintained) within the, capabilities of the power unit.
On the road the AE Road Speed Regulator worked well. The maximum speed setting was 48 mph which I thought was ratht,r low and would have preferred at least 50 mph as a more realistic figure for motorway running. The Super Comet used for the tests was loaned by S. L. Dowell (Transport) Ltd of Rugby and as the equipment had only been fitted a short time it may be that adjustment will be made after experience with it. This facility for altering the speed setting is an important feature of the unit although to do this seals have to be broken. And the electrical connection which can be disconnected to make the unit inoperative is also sealed in normal applications.
At road speeds below the maximum set on the regulator there was no sign that there was anything different from a standard
production vehicle. And when, on the motorway, the maximum speed of 48 mph was reached there was no sudden shut-down of power, the feeling being that the normal governed engine speed had been reached.
It was unfortunate, in a way, that a Super Comet had been chosen for the tests because this vehicle needs very heavy foot pressure to maintain maximum• throttle, there being heavy spring pressure on the last quarter of the accelerator pedal travel. This made the effort needed to maintain the modest speed of 48 mph rather onerous and the situation was worsened when running fully laden by a fault in the fuel pump—possibly sticking elements—which had the effect of making maximum speed in certain circumstances about 42 mph. What happened was that the vehicle reached 48 mph as normal and then the regulator brought back the fuel pump rack but did not return it to the full throttle position when road speed had reduced. I was told that in normal circumstances road speed will vary only slightly with full throttle maintained, and I had this confirmed by trying out a Ford Transit fitted with the equipment on which a road speed exactly on the set figure could be kept to continuously.
There was not the same trouble on the unladen run with the Leyland although after reaching the regulated maximum speed the figure fell to 47 mph and it was impossible to get back the extra 1 mph. These maximum speeds compared with 62 mph laden and 63 mph unladen when running without the regulator in operation.
It was interesting that in spite of the difference in maximum speeds less than 4.5min extra time was taken on the 26.8-mile motorway section when the equipment was in use running empty and this was increased only to just under 6min when running laden. And if there had not been the trouble with the fuel pump there would no doubt have been even less difference between the runs.
The motorway figures are the more significant ones for it is obviously only here that the regulator comes into effect—when driving legally. The test route included some normal road running so that a picture of the results to be expected on general operation could be obtained. The route was from the Hepworth and Grandage factory in Bradford by A650 to MI (just 10 miles) then south on M1 to the A628 junction and back over the same route to the starting point. Clearly, a vehicle operating most of the time on motorways would show an even better improvement in fuel consumption accompanied by a greater reduction in average speed and the reverse would be the case for a vehicle running less on motorways.
Main advantage Comparing the two runs when the vehicle was fitted with the regulator and when it was out of action, overall average speed for the 93.6 miles was 33 mph at 12.4 mpg with the regulator and 35.1 mph at 10.8 mpg without it. These show an improvement in fuel consumption of 15 per cent with a worsening in average speed of less than half of this amount-7 per cent. Like the productivity factor figures shown in the table (obtained by multiplying mph. mpg and gross weight) these figures indicate that the vehicle was running at a more efficient level when the regulator was in operation.
This is obviously the main advantage of the device. There is a lot of sense when considering applying the regulator to a vehicle in one's fleet to carry out some experiments by altering the maximum speed setting to find optimum results. In fleets where advantages of high vehicle speed show up in improved productivity savings in fuel may not outweigh improved vehicle utilization. But this is rare and it is more usual to find a couple of hours running at a road speed of 60 or 65 mph balanced by a longer rest period or longer wait at a delivery point.
As well as fuel savings there must also be big savings in reduced wear and tear and greater reliability especially when unladen; nothing is more likely to cause trouble in an engine or transmission than continuous running "on the governor". I was told that useful fuel savings have been made by operators of Cummins-engined vehicles fitted with the regulator and a list of operators already showing interest is impressive. Evaluation of the equipment is at present being carried out by firms such as Silver Roadways, Tate and Lyle, National Carriers, London Brick and Texaco, and operators who have already evaluated the AE Road Speed Regulator and have placed repeat orders include Continental Oil Co, United Carriers and S. L. Dowell whose vehicle was tested.
The selling price of the AE Road Speed Regulator varies according to the numbers ordered. For one set suitable for I2V operation the price is £46 which reduces to £36 15s each when 100 are involved. For 24V electrics a single set costs £50 and when 100 are ordered the price is £40 each. Fitting kits cost £5 15s each.