"FLAT" TWIN ENGINES.

Otago Witness, Issue 3398, 30 April 1919, Page 44

"FLAT" TWIN ENGINES.

The horizontally-opposed-or "flat" twin engine has "made good" where motor oyclea are 1 concerned, and an increasing number of English firms are taking up its manufacture. Objections _ are sometimes urged against it on two principal grounds—namely, (1) that it i 3 difficult or impossible to secure adequate cooling of the rear cylinder, and (2) that the pistons and rings wear moro rapidly on the than elsewhere, and that loss of compression is the result. Theoretical objections, such as these reallv are, in the main can be urged against every known form of motor oyole 1 engine on one ground or another, bn\ the question is: "Eto they amount to matters of importance in.actual" practice?" As regards the overheating, we know that the well-known aeroplane makers, the Sopwith company, have gone so far as to place thetr "A B O" motor oycle engine athwart instead of in line with the firam* in order that both cylinders shall receive an

equal shard of the cooling effect. Then, in tho nek Raleigh product a special point 13 made of providing openings or duct* which permit air currents to reach the back cylinder as freely as the front one. Both of these firms, then, have adopted special measures to cope with this alleged tendency to c-verheat in the cylinder behind. The Douglas firm, on the other hand, than whom no one can claim a better and more intimate acquaintance with the "flat" twin engine, have not, so far as we know, adopted any special cooling method in ro spect of the rear cylinder, and no one needs to be told that their machine is as carefully designed and as efficient as th-a most fastidious can require. It is on* of those points which only the user can determine. The other point raised —namely, the sup posed wear on the undersides, of the pistons—may or may not have something in It. The contention is that the weight of we piston itself lying in a horizontal plane

causes the piston to bear more heavily upon the lower than the upper wall of thp cylinder, and thus increases tho friction on the lower wall. As a rule, when a reciprocating member such as a piston or crosshead travels rapidly to and fro between fixed guides the tendency is for the pressure to be greater at the top in the one direction and # at the bottom in tho other, thus neutralising the effect complained of. and doubtless it is so in the case of the piston in a horizontally-opposed motor cycle Anyway from tho look of things, there is going to bo t quite a number of flat-twin-engined machines marketed by the leading makers in England this year. CHANCING GEAR. An interesting form of competition which the automobile clubs might take up in lieu of consumption and hill-climbing' contests is

a gear-changing event. One only wants to stand on any decent hill used frequently by carists and . note the lack of proper gear-changing that goes on to realise that there is much to learn by many car-owners and drivers in this direction. A competition calling for a change up and change down, with experts at judging stations, points being awarded for quietness and evenness of speed of car during operation, would prove interesting: and instructive to many. A double purpose would be served—namely, a novel competition and an educational demonstration to many. If the faults. in changing- could be pointed out, and the right way to manipulate the changes demonstrated with the various makes of cars, additional value would attend such a competition. OWAKA TO NELSON. A SUCCESSFUL MOTOR BUN. The following acount of .a motor trip from Owaka to Nelson, via' Christchurch, Kaikoura, and Blenheim, and return via Motueka Valley, through Genhope, Reefton, Greymouth, Otira, Springfield, Ashburton, etc., should prove of general interest. I am indebted to Mr David Wratten for supplying me with the reword: A party of four—Mr and Mrs W. E. Wright and Mr and Mrs D. Wratten, of Owaka —left Owaka in Mr Wright's Chevrolet car on March 29 on the above trip. . The party left Owaka at 2 p.m. and arrived in Dunedin the same evening, and left Dunedin at noon on Monday, 31et, and arrived in Oamaru at 5 o*olock. Leaving Oamaru next morning, they arrived in Ohristchurch at 8 p.m., a distance of 310 miles from starting point. roads thus far were very fair. Ohristchurch was left at noon, and Kaikoura was reached 8.40 p.m., a distance of 122 miles. This road was very interesting, and needed careful driving, numerous Bteep cuttings and sharp turns at the bottom, ono especially—Foster's Cutting—being, exoeedingly steep, and motorists would be well advised to see that petrol tanks are full in climbing out of it. The road all through has a very fair surface. From the Conway to Hundalee, where the way runs out on to tho coast, the grades are fairly steep, and a good deal of traffio is met. From Hundalee to Kaikoura tho road runs along the sea coast, and is very good, slightly tortuous and narrow, and a couple of tunnels have to be passed through. Leaving Kaikoura at 7 a.m. on April 3 the party arrived in Nelson at 7 p.m., a distance of 189 miles.

The road from Kaikoura to Blenheim is very good, with a few very sharp turns beautiful drive through clumps of ngaio trees along the coast for a long distance. The road becomes a little more hilly after passing Scddon, and ascends the Redwood Pass by an easy grade. There are few sharp turns down grade, and a few miles' fine running on a splendid level road to Blenheim. The road from Blenheim to Nelson is more hilly—viz.. the Rai Saddle and "Wangamoa Hill, which are both fairly steep with hair-pin bends, and need careful driving. Leaving Nelson, the party spent a week at Motueka in tho fruit gardens, the apple harvest being In full swing.- The party spent a day picking strawberries. This fruit Is grown extensively in Motueka now, and picking goei on from October to end

of May. Leaving Motueka they proceeded up the Motueka Valley through Motupiko and Glenhope to Murchison. This road is very fair, but there is a sharp climb up the Hope Saddle, and a sharp run down, with very sharp turns. There is now a fine run down the Buller River, through magnificent bush and river scenery, the road hilly and narrow, with good surface, but very sharp turns to Inangahua Junction, where the Buller is left, and the motorists follow the Grey to Greymouth over a splendid „road, but hilly. From Greymouth there is a fine run along the coast to Kumara—-a perfectly level road. From Kumara to Otira the road runs through some beautiful bush scenery for a considerable distance, the road being fairly level with a good surface. The road up the Otira Gorge is fairly easy at first, but towards the top it gets very steep, and is. always kept loose for the coach horses to jfefc a footing, but very bad for motorists. There is splendid scenery coming up-the pass, and also at the summit. There is a good run down from the summit to the Bealey Flat with a few sharp up-and-down runs, but mostly short, and two or three creeks to cross. This is the terminus of the railway, where the tunnel works are proceeding. From here to Springfield nearly every motorist sends his car by train, as the roads are not fit for motors, but this party came through all right. The roads are very bid in places, with a lot of river beds, and some of them with considerable water in them. After getting to Springfield the journey is practically over, as the country is mostly level and roads good. Another two days saw tho party safe at home after travelling over 1400 miles, a lot of it over very rough river beds, strewn with big boulders, whioh needed a steady hand and a good look out, as some of the steepest roads were taken in the dark.