21 Gas Buses Save Yearly 78,500 Gallons of Imported Fuel
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,Tilling Group Has Achieved Notable Success with Producer Gas. It Operates 43 Vehicles on Solid Fuel and Uses Gas Vehicles Exclusively at Two of its Depots COMPARABLE fuel costs of 1,67d., 14,......2,75d. and 1.52d. per mile for running on producer gas, petrol and oil fuel, respectively, are not the .least interesting and valuable items of information given in a report on its producer-gas experiences issued this month by the Tilling Group. Coming from such a source they can safely be regarded as thoroughly authentic.
Mr. John F. Heaton, chairman of Thomas Tilling, Ltd., first gave consideration to the question of alternative fuels in 1938. Thereupon investigations were made and producer gas was chosen as most practicable.
At the outset the Gohin Poulenc plant was adopted for experiment, and three units were acquired early in 1939 and subjected to tests. In May of that year„ rights to manufacture having been gained, three plants were put in hand by the Bristol Tramways and. Carriage Co., Ltd., a member of the Group, whilst sufficient material was purchased for the construction in the future, should the need arise, of 500 producer-gas plants. Arrangements were .also made for bulk fuel storage.
Failure of Fabric Filters During the latter part of the year it was found that the filtering apparatus was not wholly satisfactory, and cylinder-bore wear came into the story. The fabric of the filters became either burnt by the hot gases or choked through moisture and dust. Also air leaks ■developed at the hopper and firebox doors.
To remedy the latter, steel flanges were fitted to the apertures and castiron doors provided, the respective contacting faces being machined flat, the joints being sealed with asbestos packing, and the securing studs being replaced by bolts.
Some trouble was experienced with distortion of the producer • body, which was alleviated by. welding-on strengthening plates.
To overcome the filtering difficulty trials were made with sisal and oiled coke, but complete satisfaction was ncit attained.. On the one hand it was found that proper packing of the sisal container demanded too much care and skill, Whilst on the other, even when
correctly packed, the filtering medium lost efficiency as it became clogged, and impeded the flow of gas.
During these experiments cylinder wear was excessive, the worst figure being 0.001 in. of wear in 150_ miles.
As the outcome, it was decided to redesign the plant, employing the Government Emergency producer as a
basis, The dry filter was discarded and in its stead was used a water gascleaning apparatus designed by Mr. W. J. Morison, chief engineer of the Eastern National Omnibus Co., Ltd., another unit of the Tilling Group. A description of this device appeared in this paper on January 30.
On behalf of this organization, research was commenced at this time, May, 1940, by the Mining Department of Birmingham University. It has since submitted certain reports, on the obscure subject of cylinder wear, which prove the efficiency of water filtration.
Cooling and Cylinder Oiling Other modifications made included the provision of baffles in the cooling tubes to compel the gases to make intimate contact with the walls, and the positioning of the tubes vertically, which has proved to be more effective in respect of cooling. Another improvement was the incorporation of a drip oil feed for upper-cylinder lubrication.
As .a general result of these measures more consistent running has been obtained, and, over a considerable period of testing, wear averages the very different rate of 0.001 in. per 4,000 miles, which is comparable with that for petrol.
• Progasite is the fuel that has been mainly used. It is delivered in open trucks, because it need not be dry now that the water filter is used. This fact represents a saving of 7s. 6d.
per ton. Further, it is treated with sodium carbonate to reduce the tendency to clinker.
Among other fuels tested, Suncole and Oco are named in the report as giving performances comparable with soda-treated anthracite. Their drawback is their bulk, larger hoppers being necessary for equal range of operation.
Petrol is used only for starting, a limited amount is allowed for each vehicle and the petrol carburetter is not controlled from the cab.
Many operators of producer-gas vehicles will be particularly interested in the Tilling servicing routine. Regular operations include removing clinker and ash from the firebox, recharging the hopper, cleaning the coolers, washer and water separator and renewing the water in the washer. A point mentioned as noteworthy is that, unlike dry filters, there is no dust in connection with cleaning this filtration system. Every day sparking plugs are taken out and cleaned.
Notable P.S.V. Performance
In the Tilling Gronp's total fleet there are 43 vehicles running on gas in various parts of the country. Two small depots operate only gas vehicles, namely, the Maldon depot of the Eastern National Omnibus Co., Ltd. (nine vehicles), and the Cromer depot of the Eastern Counties Omnibus Co., Ltd. (12 vehicles). The services from these two centres cover town and country conditions, average running speeds of 141-183 m.p.h., have routes up to 41 miles in length, and involve monthly mileages of 48,000.
Maldon returns a fuel cost of 1.37d. per vehicle mile, which includes petrol for starting and labotir for treatment
of the anthracite. Extra labour in filEng hoppers, etc., as compared with petrol operation, amounts to 0.3d. per vehicle mile. This additional sum has been taken into account. in the figures quoted in the first paragraph.
It is emphasized at the conclusion of the report that the saving in imported liquid fuel effected by the use of producer gas at these two depots alone amounts to 78,500 gallons a year.