Answers to Queries.
Page 17
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Our readers will be informed by the Editor on am•Y ,Points connecied with the construction or use of commercial -motors, . Where a direct reply is desired, a stamped and addressed envelope should be enclosed if a request for privacy is not specially made, any query and answer may..bepublithed.
The Fitting of Piston Rings in Steam Engines.
" P.T." [1,303] writes :—" Newly-fitted piston rings never give as good a compression as when they have been in use for a time. The cylinder walls are burnished by the piston reciprocating in the cylinder, consequently, the surfaces Of the new rings, no matter how carefully they are fitted, do not accurately coincide with the bore iot the cylinder and it takes a certain length of time before sufficient wear has taken place to bed ' the rings and to give the maximum Compression. The slit in the ring should just close and no more when the ring is pushed into the cylinder ; if a gap is left between the ends of the ring, there will always Le a possibility of a leakage past the ring."
What Power is Wanted ?
" A.T.M." [1,3o41 writes :—" Do you consider that an engine which is capable of giving out only 6h.p. should be powerful enough for a traveller's car for a fairly-hilly district—some grades of i in so? The car in question will have to carry drapery samples, averaging about i cwt., in addition to our traveller and the driver."
ANSWER.—A car of this description would be decidedly under-powered, even had it an unusually law gear with An engine of the power named by you. There are many well-known makers of motors who specially cater for the class of work you mention, and the powers of the motors range from 8h.p. upwards.
Live" and " Concentric " Back-axles.
" M.S." [1,305] writes Will you kindly inform me of
the difference between an ordinary 'axle, and one of the
concentric ' type, both of which forms I have seen frequent]y referred to in your columns?"
ANSWER :—The essential difference between the two forms is that the ordinary " live " axle notonly propels the back
410145. of-the vehicle, but it, also, has to bear its share of the total toad. In the " concentric " type of axle, the " live " axle proper rotates in a sleeve, the outer ends of which form bearings for the road wheels ; the necessary connection between the wheels and the " live " axle is accomplished by some form of " dog " or " star" drive. The latter form is much superior to the former, inasmuch as the " live " axle proper is subjected only to torsional stresses, whilst the sleeve upon which the wheels run takes all the bending strain and shocks from the road, thus dividing the work • equally between the sleeve and the inner axle.
Life and Working Cost of Tr-car. "
A.S. " [1,306] writes :—" The agent of a firm of motor tri-car builders called upon me recently to offer a light delivery van which, he assured me, would only cost about id. per mile to run (exclusive, of course, of the boy's wages)_ At the same time, he stated that the tri-car would be capable of running Lso miles per day, and would last for at least TO years. Do you consider that the above statements can be taken as a fair estimate of the cost of running and the life of such a vehicle?"
ANSWER.—We are afraid the representations in regard to this matter have gone a little too far. Tricycle-carriers have proved themselves very useful in certain parts of Paris, and in other cities where the roads are exceptionally good, but they have not been successful in cities, like Manchester, where the road surfaces are bad. The construction is generally too light for the vehicles to stand up to their work for more than a few months, let alone ten years, and in no case do we consider that such a vehicle wouldbe serviceable for more than five years. Our correspondent does not furnish any particulars; of the weight, engine power, or transmission, and we cannot' reply more fully unless we are put in possession of some facts about these points. The cost of d; per mile is in any event prepoSterotisly low.