7/28/2019 Experiences with a 3hp twin.

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MAY i^th, 2919. 4S7

The writer's 3 h.p. Enfield. Note the carrier box, which protects a small leather travellingcase, also the handle-bar muffs,; they proved very cosy.

EXPERIENCES WITH A 3 h.p. TWIN.An Appreciation and Some Criticism of an Interesting Mount, based upon a Year'sAil-weather Riding.O combine a general averagespeed of 30 m.p.h. with

petrol consumption of 105i.p.g. is not the rule witli light-\veights, yet this can be statedwithout exaggeration to be theregular behaviour of the 3 h.p.

twin Enfield, which the rideras used constantly for a mileagef four thousand. The machinewas used for week-end journeys ofabout one hundred miles each way,with occasional business runs.

It was purchased early in 1917,and its first run was on snow-co^-ered roads with a return duringthe subsequent thaw o\ex half-looded roadsa rough test throughwhich it behaved excellently. Atfirst it promised to be a mud-slinger, which was partly due to the speed30 m.p.h.riding for long through water)- slush is bound to pro-duce a very dirty machine and rider, but the machinealways held the road in grease exceptionally well; notthe slightest tendency to side-slip was experienced dur-ing the whole of its use.

These journeys were kept up at intervals of twoor three weeks for some nine months. Several timesthe run of ninety odd miles was made without a stopivi approximately three hours, and never did thejourney occupy longer than four hours. The onlyinvoluntary stops were through comparatively triflingthings, a broken throttle wire being the most trouble-some ; lack of power w'as noticeable only once or twice,and on one occasion the nuts securing the magnetodrive casing and magneto platform worked loosethrough vibration.

Speeds.The highest speed recorded (and the speedometer

has proved to be verj' accurate) was 46 m.p.h. Nodoubt if ';periillv tuned for speed, it would exceed

50 m.p.h. It wasnot this goodfigure which wasthe chief attributein speed ; it wasthe steady way inwhich it wouldkeep humming at3 to 35 m.p.h.There was an un-obtrusiveness atthis speed whichoften caused therider to suspectthat the speedo-meter was record-ing inaccurately,but a good totaltime for the jour-

The weight of the magneto and itsplatform, with' the driving chain covers,is carried by three bolts on the timingcase, and a support in front.

ney always dispelled this doubt. A repeated averageof 30 m.p.h. on a hundred mile journey, whichincludes eight to ten miles of town traffic, is anexcellent performance for a 3 h.p. machine.

Petrol Consumption.105 m.p.g. is not a careless computation, but theamount of petrol purchased divided into the mileage

-without any allowance for waste. This was obtainedwithout any special fitments except the substitution,for the original air inlet, of a curved intake serratedto fit between the fins of the back cylinder. Allpossible points of air leakage in the induction pipeand carburetter were carefully wrapped with insulatingtape. < .No freak hill-climbing was attempted, but the enginehardly ever required second speed on ordinary mainroad hills ; therefore I shoiild say that the machinepossessed excellent hill-climbing abilities.

It was very light on tyres, but the back tyre wasrenewed after 2,500 miles by reason of a bad gashwhich rendered itnearly useless.The consump-tion of lubricat-

ing oil was notchecked verycarefully, but itwas somewhere inthe neighbour-hood of 1,800m.p.g.

I have nothingbut praise for thewell - known En-field gear andshock absorberthe latter wasparticularly effi- J^g hot air intake. Observe the tape-cient; and, to my wrapped carburetter joints.

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4S8 MAY 15th, igig.Experiences with a 3 h.p. Twin.surprise, when recently dismantled for examination,the rubber blocks showed no sign of wear or loss ofresilience.The engine was not touched until some 3,000 mileshad been covered ; there was practically no sign of'wear and no unusual amount of carbon deposit.Now for some points of criticism, which are intendedin a spirit of friendly opinion and in no sense expressing

dissatisfaction.Starting.On very cold mornings, it was extremely difficult

to start; exactly why this was so, I was unable toascertain. Certainly poor quality petrol was part ofthe trouble, but not all ; a pair ofParker vaporisers fitted in the induc-tion pipe gave some little improve-ment. Once started there was nofurther difficulty.

Comfort.I cannot entirely recommend themachine for a tall rider (but then,

very few lightweights are suitable forpeople over six feet), but the mediumor short rider should find it quite ascomfortable as most machines with-out spring frames. The best posi-tion I could find produced discomforton a long run, but the fault liescliiefly in my own 6ft. 2in.One point of detail which needs alteration is thefiller cap of the glass oil reservoir; being about ^in.diameter and only projecting about lin., it is verynearly impossible to pour oil directly into it fromthe ordinary can. I suggest that the diameter beincreased to at least two inches, and it should projectmore and be formed with a cup as shown in theadjoining illustration.

Undershield.An efficient undershield and magneto cover are badly

needed, and I w^ould recommend a complete redesignof footboards incorporating with them, in one unit,an undershield, leg-shields, and magneto cover, havinga short extension backwards under the driving chain;

In place of the small oil hller capprovided, a suggested alternative isshown.

the front wheel has an annoying way of spraying mudon the imderside of the countershaft sprocket.. '

KicK Starter.The forward position of the kick-starter and

direction of push is distinctly awkward, and I gave upthe use of the kick-starter and almost invariably startedby paddling off in low gear. I think a new type ofstarter should be fitted behind the engine with anaction which will enable the rider to employ his weightto better advantage.

Magneto Staging.The method of carrying the magneto on an ex-

tension of the driving chain covers is not so good asit might be. Only three of the fivesmall bolts carry the weight, andthey in turn take their support fromthe timing case cover ; the hingedsupporting strut under the magnetoplatform is of very little use. Whenthe outer cover plate is removed, thewhole casing and the magneto on itsplatform sags over for want of lateralsupport. The cover plate should beremovable without affecting the sup-

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port of the magneto in any way, andthe magneto platform should havelugs to clip it to the down tube ; theinside half of the magneto drivingchain cover should be cast in onewith the timing case cover.The question of control wires inside or outside the

handle-bars has been ofttimes a bone of contention.I am not personally enamoured by the Enfield methodof enclosing the Bowden wires or the fixed lugs tocarry the levers, though both these are neat.

Despite the points indicated, I shall still take anEnfield before many other makes, when I require afast, reliable, solo lightweight ; and I retain memoriesof many enjoyable runs on this interesting machine.

F.A.S.[The magneto fixing has given no trouble on a similarmachine in our possession, and as regards thewriter's trouble in starting, this is certainly curable.Only the combination of frost and No. .^ war spirithas caused sluggishness in our case. Ed.]

->-f-STAINLESS

IT is only a question of time when the entire motorcycle industry will recognise the enormous usethat can be made of stainless steel, and it may

be expected that many makers in the future will useit for valves and exposed metal work.

Stainless steel is a chromium alloy steel, with thecomposition of 12.5% chromium and very low, .28%,carbon, the rest being iron and the usual impurities.Its outstanding peculiarity is that it is perfectly im-pervious to atmosphere corrosion.As regards its mechanical properties, it can be givenany desired tensile strength (and so hardness) from 40to 100 tons per square inch by suitable heat-treatment.It also shows a remarkably high resistance to fractureby impact upon it; in the well-known Izod impacttesting machine it required eighty foot-pounds tobreak a notched test piece.

STEEL.From these data much can be gathered. Enamelwork can be dispensed with, and, if desired, an entire

frame be made with it, as it can be readily drawninto tubing. It can be pressed into rough or accurateshapes for control levers and nuts. Spokes and rimscan be made of it wth the greatest of ease. Ofcourse, its greatest work can be done for valves,scaling is unknown with rustless steel valves.

Its great fault is that it cannot be easily cast owingto its high melting point (about 1,400"^ C), thusit is out of the question for cylinders and crankcases.

Probably the present cost of this steel, which, owingto the high price of chromium, is large, will prohibitits use for frames, but, otherwise, there is no reasonwhy the rest of the machine should not be manu-factured from it. - Arthur Goffey.