• RUNNING A LORRY. ON SISAL POLES.
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A Successful Experiment with a New Class of Fuel Used in a Compound Gas Producer on a Karrier Lorry.
TN the early part of 1928 a quantity of sisal poles was sent from Kenya Colony to this country, in order to see whether any use could be suggested for this material. Sisal poles are the central stems of the plant which is left after stripping off the valuable fibre used in the production of sisal hemp and other material, and in appearance they somewhat resemble bamboo, but without the characteristic rings and knots of the last named. The poles are, however, solid; the outer skin is an extremely hard wood, closely resembling bamboo in composition and about i-in, thick, according to the size of the pole. The interior is filled with a light substance resembling pith.
The ,weight of the poles in proportion to ,their size is extremely light, and this may be gauged from the fact: that a polo 3i-in. in diameter and 6 ft. in length weighs only 7 lb. They are made use of to some small extent for building purposes, but oaring to their. very light nature this application is limited and there is, in the district where sisal is grown,
an immense accumulation of poles for which no useful purpose can be found.
It was at first thought that. it would be possible, by the use of suitable machinery, to reduce the sisal poles to chips and use them for firing boilers, but that particular application would have been a small one in Kenya Colony. However, before the first consignment of poles was totally reduced to chips, it was suggested that they might be used to furnish fuel for motor vehicles through the medium of the Compound gas producer, and the remaining poles were sent for trial to the works of the Compound Gas Power Company Ltd. at Reading.
The poles were cut into pieces a few inches in length and the total quantity of material obtained was found to be sufficient for running only a few miles, taking the consumption at 4 lb. of the sisal per vehicle mile. The results obtained were satisfactory, but the small quantity of wood did not allow sufficient running to give a con clusive demonstration of the value of the fuel, and it was then arranged to ship a considerable number of poles to this country to enable thorough trials to be carried out.
The sisal poles arrived in England early in July, and trials were conducted immediately. It was found that sisal is an eminently satisfactory fuel for use on motor vehicles. The poles were, as before, cut into short lengths ; half of the lengths were again cut into four pieces, the other half being left as cut from the poles, and trials were carried out with each size.
As no paper or shavings would be obtainable in places where these lorries would have to operate the fire was lighted in the producer direct on 'sisal, so that the material used throughout, both 'for lighting and running, was entirely from the sisal. After lighting the fire, fresh quantities of sisal were added to the producer and the fire was alldwed to burn for 15 minutes. The 'engine of the lorry was then started up on petrol and immediately switched over to gas derived from the producer.
The' vehicle used for the trial was a Karrier. type " :EH " 4-tonner On solid tyres, and it was loaded with four tons of pig-iron. A special cab allowed accommodation for the six passengers who were also carried, bringing the total mewing load of the lorry to over eight tons. The vehicle, having solid tyres, could not be taken over brokeh ground, so that the trials were conducted on the ordinary' roads ; but the vehicles which are to be used with this producer running on sisal will be Karrier type "WOO " sixwheelers, earrying three tons, and they will therefor' be able to negotiate difficult and broken country.
The sisal poles proved to be a most excellent fuel and gave rather better
results than ordinary hard wood. The consumption per mile, however, was a little more than that obtained on hard Woods and worked out at 4 lb. to the mile, the consumption of hard wood on a straight run being a little more than ai lb. to the mile. One drawback to the sisal is the large bulk occupied in proportion to the weight. The hopper shown on the vehicle in the accompanying illustration would enable the lorry to be run 200 miles on one filling, using hard wood, but on sisal the hopper would, only accommodate enough fuel for a run of approximately 50 miles. In the district where the lorries are to operate, however, this will be no detriment, as the runs will in each case bo short and there will be no difficulty in picking up ample fuel when required.
It is somewhat difficult to arrive at the relative fuel cost in the two cases : sisal has no value locally and the only expense would be in cutting up the poles to suitable size. These, being very soft and light, can be cut up into pieces of suitable length by chaffcutting machines, but in any case the cost 'would not work out to more than 10s. per ton. Petrol in this district is approximately 5s, per gallon, and assuming in broken country that the vehicle would run six miles to the • gallon, this would be 10d. per mile for petrol com pared with id. . per mile for sisal.
The proprietors of the Sisal Estate, however, assume that they will be able to run their lorries on sisal at a cost of 150 miles for a shilling, so that the fuel cost can he put down to Practically nil.
Although the district where the lorries are toe operate is flat, the route chosen for the purpose of the trial was heavy. It was found on level roads that a speed of 25 m.p.h. could be obtained and the average speed over the entire course was 17 m.p.h. A long hill having a steepest portion of 1 in 9 was climbed without having to drop into the bottom gear, ' and as this particular vehicle was fitted with an auxiliary gearbox giving eight forward gears, the were thus on this particular hill five further gears in reserve. It can be safely taken, therefore, that the lorry will be capable of going anywhere where the wheels can get a grip.
A weighed quantity of sisal of each size was fed into the hopper and the first run taken on the smallest size of sisal, this being run right out until the vehicle came to a standstill, and
the mileage was then noted. The second lot, or larger size of sisal, was then placed in the hopper and , the vehicle again run until the fuel gave out and then the distance noted. There was no observable difference between the mileages given by the two sizes of fuel.
Sisal burns completely away, leaving no ash of any kind, and only a very slight trace of silica is left on the deflector cone. It may thus be stated that sisal i.s a perfectly suitable fuel in every way, its one drawback, as before mentioned, being the large bulk occupied by any given weight. The fuel appears to contain no volatiles which cannot be successfutlY disposed of in the producer, and should prove a valuable means for opening up the districts where it is grown by permitting the operation of transport vehicles at small cost, the fuel being the heaviest item at' the present time.
The accompanying illustration shows the Karrier lorry on which the trials were conducted. The sheet-steel hopper above the driver's head is readily detachable and the vehicle can be run either with or without the hopper, as desired. In the latter case, however, it is necesary to carry the fuel in bags, it being shot into the producer as required. The engine does not have to be stopped for this purpose and if a second man be carried it could be done without stopping the vehicle, When the hopper is fitted, however, only a driver is required and the handcontrolled slide admits fresh fuel. No water is required whatever, and there are no moving parts or fan for lighting up. The Compound producer is a single-unit fitting; the scrubber or gas cleaner encircles the producer proper, and access to the scrubber is gained by the doors shown in the sides of the producer. These doors are of the man-hole type and are detached by slackening a central nut, therefore no parts can be lost.
The producer, when running, is entirely open to the atmosphere ; there is nothing sealed up and consequently there is no possibility of an explosion. The first of the Karrier "W06" lorries fitted with gas producer to use sisal will shortly be leaving for Kenya Colony, and it is hoped to give an illustration of this in due course.