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Simplicity in Carburetter Design.

7th January 1909, Page 19
7th January 1909
Page 19
Page 19, 7th January 1909 — Simplicity in Carburetter Design.
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A Description of an Extremely Simple yet Effective Carburetter which has introduced by the Doherty Motor Components, Limited, of Coventry. been

Since Krebs introduced his automatic carburetter, and set out his views on the action of that device in roof, numerous inventors have endeavoured to produce carburetters which would give the highest possible efficiency so far as fuel consumption is concerned, but it is to be regretted that many of these inventors have worked along lines that have led to the production of complicated and delicate mechanisms that are totally unsuited to the conditions under which the average motor vehicle is compelled to perfdrm its functions. The addition of auxiliary air valves, with their attendant :ontrolling springs, although intended to effect a saving in he amount of petrol consumed, is frequently the cause ot ;rent trouble, involving loss of time which costs far more han any amount which may have been saved on the fuel For that reason, therefore, there are many engineers who prefer the old hand-regulated type of carburetter, which, vhilst possibly less efficient from the point of view of conumption, is far more practical and suitable for employment fl commercial vehicles; at any rate, many of London's aotorbus engineers seem to think so, and they certainly now what does, and what does not, give rise to trouble.

An entirely new form of carburetter, with a variable jet, as recently been introduced by The Doherty Motor Comonents, Limited, of Coventry, and this device is absolutely evoid of anything in the nature of a spring. The device is lustrated on this page, and it may be seen that its construeion is delightfully simple. It is operated by means of a ingle lever, and a clever form of adjustment is provided in rder to what the carburetter, without a lot of tedious tting and adjustment, to any particular engine. in the tajority of hand-controlled carburetters, two levers are emtoyed, one for the regulation of the supply of air, and the ther for the throttle valve.

In this new component, the same result is obtained by Iteration of the size of the opening of the petrol jet, at the ame time, and with the same lever that actuates the arottle valve. This valve is arranged quite close to the !t, and is of the rotary type with a " V-shaped " port. By ins arranging the throttle opening close to the jet outlet, w former acts as a choke tube and determines the velocity the air as it passes the jet. As the throttle valve opening

is reduced the amount of air which passes through it does so at a higher velocity, a n d, i n order to prevent the mixture's becoming too rich, the amount of fuel delivered from the jet must be proportionately reduced. This is effected by the coupling of the plunger (A) to an eccentric pin on the throttlevalve spindle by means of a short connecting 1 i .1he plunger (A) has a tapered shank, which .projects through the hole in the top of the fixed jet (B).

in V1 hich the plunS2436 ger is guided by an enlarged portion. When in its lowcst position, the tapered -hank completely prevenls the passage of any petrol between the hole in the jet (13) and the plunger spindle.

In order to adjust the relative positions of the throttle valve and the plunger, the eccentric spindle may be rotated independently of the throttle valve, thus altering the lift of the plunger; the eccentric spindle and throttle valve must then be locked together by the small set screw (E), the whole operation of adjustment occupying but a few minutes. This Doherty carburetter is the neatest and simplest carburetter we have had the pleasure of examining, and its behaviour in actual use has more than justified its introduction. Its price is low by reason of its simplicity. Section tInough the jet.

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Locations: Coventry, London

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