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ones are not previously known. In this case the want of tune on the first trial prevented a better test being carried out.

I tried the vehicle again when the tuning had been carried out. On this occasion a speed of 20 miles per hour over rough roads on the level, with a load of one ton, was easily kept. The radiator boiled to excess on the first trial, but only slightly on the second trial. I am informed that the makers are now prepared to guarantee that no overheating will occur at any altitude, as they have modified the radiator and cooling arrangements still further. Acting Assistant Director of Public Works.

May, 1926.

Sub-Annex 5.

Comments on the Report on Morris Roadless Lorry. Running of Machine in Drying Cotton Soil.

The report states that the speed of the machine was 1 to 2 miles per hour. This is a pardonable error, as speeds are very hard to judge. The actual speed of machine with trailer recorded by the speedometer was 5 to 6 miles per hour. This would no doubt have been in the region of 10 miles per hour had the carburettor been fitted with a smaller choke tube and jet, suitable for the altitude we were running at.

Regarding the stiffening of the track due to soil adhering to the outside, and the intrusion of soil into the unit, thereby causing loss of efficiency, I should like to correct this report in one or two details. The report states that the track unit was cleaned, and one man was then able to push the machine. Only the soil adhering to the outside of the track was cleaned off, the soil in the unit was not removed, so it will be seen that the intrusion of soil into the unit contributed but a little to the loss of efficiency of the machine. I have since carried out tests both in black cotton soil and red soil when in a drying condition, and by the use of a very simple scrape I find that the external part of the track can be made self cleaning, so removing a defect which reduced the efficiency of the machine. By alteration to the driving sprockets, allowing larger mud scrapes, removing the ribs between the teeth, and altering the silencing rings, the tendency for the track to ride out of mesh was reduced to a minimum.

Since this test took place, I have been informed by the patentees of the track unit, Roadless Traction, Limited, that they have produced a new type of sprocket which will obviate the packing of soil in the teeth and in the recess between each tooth, and that any soil that gets on to the path when the bogies run will not cause the teeth of the track to come out of mesh.

On this new type of sprocket the teeth are open at the bottom as also is the recess between each tooth, so that any soil that is between the track and the sprocket must pass through without interfering with the pitch or causing the teeth to come out of mesh.

The report states that when the soil was cleaned from the track unit the track showed three inches of sag. The report is quite correct regarding the sag, but not the cause. These tracks, when correctly adjusted, have a sag of 1 to 2 inches, so in this case there was roughly one inch of sag in excess of what is allowed. The sag in the track was noticed after running on dry soil for about ten miles. This slack in the track I attributed to the idler wheels, which are used to adjust the track to the correct tension, slacking themselves back owing to the spindles which hold them in position not being sufficiently tight. The soil which got into the idler wheels in no way interfered with or reduced the efficiency of the machine. It meant that one carried 15 to 20 lb. more on the machine. This will be obviated on future machines. The machine has since been tested on sand and in wet black cotton soil, when it was in probably its worst condition and was able to negotiate either in a very satisfactory

way.

The new larger power unit has been tried out here under very severe conditions, and found to be very satisfactory. The cooling in future will be adequate under any conditions. From the foregoing comment, it will be seen that defects in the first machine have been noted, and the machines now being produced will be free from these and will operate satisfactorily under the most severe conditions.

June, 1926.

C. SKELTON.

APPENDIX D.

Extract from a despatch from the High Commissioner for 'Iraq to the Secretary of State for the Colonies.

19th May, 1926.

I have the honour to transmit for your information the enclosed copies of correspondence, in which details are given of the experimental use of Citroen Kegresse vehicles in this country. As you will observe, these vehicles have not yet been used in this country to any great extent, but the information

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so far obtained is sufficient to show that they are well adapted for use in Iraq in the rainy season.

H. DOBBS.

High Commissioner for ‘Iraq

ANNEX 1.

Extract from a Memorandum dated 29th April, 1926, from Air Headquarters, Baghdad, to the Secretary to His Excellency the High Commissioner, Baghdad.

Caterpillar Track Vehicles.

1. A Citroen Kegresse has been undergoing tests with the Shergat-Mosul Convoy throughout the recent winter.

2. Mileage with the Convoy Section to 1st April, 1926, was 1,014 miles, but this vehicle has seen a certain amount of previous service.

3. The Kegresse tracks are easily penetrated and damaged by flints on metal roads, and except in emergency it is not used on such surfaces.

4. During the recent wet season this vehicle has accomplished trips up to 40 miles, when the conditions were such that the journey could not be accomplished by a Ford with certainty.

5. It has, on numerous occasions, retrieved badly bogged Ford cars and Ford ton trucks.

6. On one occasion it retrieved a Leyland lorry which was unapproachable by other vehicles.

7. It has never itself been "bogged or incapable of extricating itself.

8. Its performance is excellent in very soft sand. In the case of an aeroplane which had crashed on very soft sand this vehicle. was able to tow it to hard ground when no other method of moving it was possible.

ANNEX 2.

Extract from a letter dated 7th May, 1926, from the Managing Director, Cotterell and Greig, Limited, Baghdad, to the Under-Secretary to His Excellency the High Commissioner for 'Iraq, Baghdad.

Roadless Traction.

I have to state that to the best of my knowledge no type of trackless transport has been employed here with the exception of Holt Caterpillar Tractors and Bullock ditto. These were imported by the British Army during the war, and on account of their ponderousness and heavy fuel consumption may be ruled out from the point of view of economical transport.

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The only 'half-track type of transport so far introduced into Iraq is the Citroen Kegresse. This consists of a Kegresse attachment to an ordinary type of touring car.

When the Nairn Transport was held up last winter by heavy rains about 50 miles outside Ramadi, this Citroen Kegresse was chartered by the Nairn Agents to proceed to the convoy's assistance and to bring in the mails. I am reliably informed that it successfully negotiated, on low speed, most of the distance between Baghdad and Ramadi, and only came to a standstill owing to some fault in the gearbox. At this time no other cars were able to proceed, and there is no doubt that the road conditions at that time were appalling.

I understand that the road track was completely obliterated by mud and water and that the driver made no serious attempt to keep to the road, but simply made his way in the direction of Ramadi, clearing obstacles as best he could. Despite the breakdown alluded to above, I consider that this incident demonstrates the all-round utility of the half-track vehicle in this country.

We ourselves have carried out a great deal of transport work with Fordson tractors, but to date these have been entirely confined to tractors with four wheels. From the performance of these vehicles on the roads, we have come to the conclusion that they are not entirely suitable for traction on heavy sand, neither are they suitable for hill climbing except in dry weather.

APPENDIX E.

Notes on some Characteristics of the War Department Type Rigid-Frame Six-Wheeled Vehicles.

It has been the aim of the War Department since the war to encourage designs of load-carrying vehicles suitable for war,

which would also be suitable for commercial production and employment.

One of the main desiderata is that such vehicles, without undue detriment to their road performance, shall have a considerable ability to travel "off the road or on very bad roads. The rigid-frame six-wheeler appeared to present a suitable line of investigation.

For some years the Experimental Branch of the R.A.S.C. has been carrying out examination of the many six-wheel designs, and exhaustive trials with a Renault six-wheeler of the well-known Trans-Sahara type.

The conclusions arrived at were that, apart from the general desiderata, such as light weight, strength, use of standard units, &c., the salient points on which the successful performances of the six-wheeler depend are:

(a) That the suspension of the driving axles should be such that, under all conditions of tractive effort, the weight of all four driving wheels on the ground shall remain equal.

(b) That the suspension shall also permit of free articulation of the driving axles, within as wide limits as is practicable, in such a manner that the springs are not twisted, nor the equal weight distribution over the four driving wheels disturbed. This enables the wheels to conform to rough ground without affecting the drive and whilst causing a minimum of chassis displacement and distortion.

(c) That a high tractive effort is required, and should be obtained, rather by gearing down a moderate-sized engine than by provision of a very large engine.

(d) That a low intensity of pressure between driving wheels and the ground is required to reduce sinkage and some form of non-skid to enable sufficient adhesion to be obtained to make full use of the high tractive effort provided, when travelling over soft or friable ground.

It was found that no existing designs complied entirely with (a), (b), and (d).

Suspension.-A new design was therefore prepared for the suspension. This design, patented by the War Department, has given excellent results, and the principle is incorporated in the vehicles now being developed.

Transmission. In addition to a normal four-speed and reverse gearbox, a two-speed reducing gear is incorporated. There are thus provided four speeds and reverse of a normal order for use when running on roads, or good going, and four speeds and reverse of a much lower order to produce the high tractive effort required for negotiating soft or rough going and steep gradients.

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