Carb 101: The Design

The design of the carburettor is quite interesting in itself and came about to overcome some problems in using the chainsaws (although the roots of the problem go back further still). Find out more after the jump...

The early chainsaws could be operated by blokes that could scale tall trees in a single bound, rip up sizable trees straight out of the ground with their bare hands and thought nothing of cycling 30 miles to chop down a tree with just an axe and then tow it back home (before chopping it up to use as firewood). Apparently.

In fact, if you are one of those very people who used those early saws, drop me a line via the comments as I'd love to hear of your exploits with those chainsaws.

Anyway, the early chainsaws used engines that had to be kept upright, and so they made use of an arrangement that allowed the bar to rotated from a vertical position to a horizontal one - whilst the engine remained upright.

When you think of the angles that the climbing saws get used at, you wonder what changed to make this possible. Answer: the carburettor.

Those early engines used carburettors fitted with a float chamber, as the fuel filled the chamber up the float would close the needle so restricting flow. It worked well - as long as the saw remained upright. Once the saw got used at an angle the float didn't work as it was supposed to, with the result that the saw didn't run smoothly (or at all).

The design of the carburettor had to change, and it did. The float chambers went out, and in their place came the new diaphragm carburettors that allowed working at any angle. Using 2-stroke engines also helped as lubrication to the engine is supplied via the fuel, so now a saw would run properly and receive adequate lubrication irrespective of what angle the operator used it at.

As we go through Carb101 we'll be stripping down a diaphragm carburettor and seeing how it works.

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