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Thursday, 7 February 2013

BB - briefly exhumed

When I ceased to be Barrett Bonden and became Lorenzo da Ponte, two if not three commenters told me I would always be BB to them. I assumed they meant the high falutin' music stuff was an aberration and that nuts, bolts, Aston Martins and VHF oscillators would continue.

So here's BB being atavistic (hope you like that five-dollar word).

You don't pour petrol (US: gas) into a car engine, you supply it as petrol vapour and air. Now fuel injection does the mixing via controllable, not very interesting electrical pumps.

This effect can also be achieved more ingeniously (and cheaply) with a carburettor (US: carburator).

Imagine a narrow tube - a jet - with a tapering bore. A needle with a matching taper sits in the jet. A cable raises the needle from the jet, allowing petrol to flow through the space now created.

But we don't need a pump to urge petrol flow. The jet/needle works inside the carburettor body containing the sucking action which occurs when the engine cylinders descend. Thus petrol is sucked through the needle/jet gap.

A hole in the carb body leads to the outside world. As the needle/jet rises an attached tubular "trapdoor" also rises allowing more and more air to be sucked in through the hole via a widening slot in the trapdoor. Mixed petrol and air are then burned in the engine.

Difficult to explain but admirably simple. The driver's need for power is conveyed via the cable and the tricky bit - mixing - is done proportionately and automatically with two sliding parts. Cast in pot metal and costing tuppence.

Fuel injection is more efficient, less polluting. Carburettors are limited these days to small motorbikes and mowers. But they’re still an elegant solution.   

9 comments:

  1. My exterior thermometer is measuring minus 30 at the moment. I need to use the car and hope the petrol is not frozen. Was told to keep the tank half full at all times in winter. Not sure it is.
    I have remote starter but have to dress full gear and step out to see if car started. Price to pay for overlooking garden and woods instead of parking lot.

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  2. Ellena: Gives me an opportunity to wheel out an anecdote about my own personal displacement. I moved to the USA in very late December 1965. Very shortly afterwards I heard a bit of meterological news and read an ad in a magazine which - combined - proved that the UK and the USA don't really share the same planet. The weather news revealed that the temperature in International Falls, Minn, had hit -47 deg F while the snowfall in Oswego, NY, had amounted to 103 in. Meanwhile (as we writers of fiction love to say) the ad, publicising either Hertz or Avis, mentioned that the rental cars at Green Bay airport, all parked outside, had their engines continuously running throughout the day (and presumably the night). Turn an engine off and , after 30 min or so, the car woudn't start.

    Have you considered having a heating element installed in your car sump with an external socket into which you can plug in an electric power line from the house? If not, why not?

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  3. That post has erotic qualities.

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  4. I thought at first it was a meat mincer...

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  5. Sir Hugh/Lucy: I feel like Blondel, wandering among seemingly empty castles with my lute, singing my lonely technology song, hoping against hope I'll hear the echo of of a response, knowing it won't happen. Perverts and people tied inextricably to kitchens don't count.

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  6. Meant to say how about a post on cam shafts.

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  7. Joe: Is that a faint echo from one of those tall towers in Austria? Ah, my Richard.

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  8. Never fear R.R. (B.B?)your "lonely technology song" was thorougly appreciated by me!

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  9. Avus: Appreciate your response. Of course I was also singing to myself. Was it possible to explain the carburettor's quimtessence in 233 words (the introductory bit didn't count). It's something you yourself might consider, say, for your bike's electric motor. But it's quite a discipline. Note the word "slide" doesn't appear in my post. A matter of keeping the words to an absolute minimum.

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