Why is it that chainsaws need a pull cord to start? Couldn’t they just be turned off or on with a switch?
In: Engineering
You could build in an electric starter to your chainsaw but then you’d have to haul around the electric motor and the battery, which adds a lot of weight and bulk (and cost). An engine that small is easy enough to start that getting it going by hand usually isn’t an issue, so it’s not worth the headache that a self-starting unit would have.
I see all the stuff about electricity, which is true, but also a switch can easily be accidentally flipped or flipped by an unsupervised child.
In order to do that it would need to have a battery, an electric starter motor, and a coil to generate electricity to recharge the battery, all of which would add a bunch of weight which you don’t want with a handheld tool.
The pull cord on a chainsaw (or a lawnmower, for that matter) starts turning the engine over, which produces the energy needed to kickstart the engine into motion.
If you had a switch…you’d close an electric circuit, but where would the electricity come from? What would make the engine turn on to produce the electricity?
It takes more effort to start a motor than to keep it spinning.
The pull cord is so you can get it going and it doesn’t add any extra weight except for the cord and handle
An engine that runs on gas or gas/oil mixture is generally one that explodes that fuel to drive one or more pistons, etc. You can’t start such an engine just by applying electricity to it, you have to get process of firing the spark plug to turn the crank started. If you fired a spark plug when the piston mechanism was in the wrong position, the piston would drive the engine in the wrong direction.
So the way to get such an engine started is to move the whole mechanism a little bit in the proper direction while electricity is available for the spark to fire at the correct time. Really old cars had a crank; manual transmission cars can still be started by turning on the ignition, pushing the car forward at a mile or two per hour with the clutch pedal pushed in, and then releasing the clutch suddenly (to move the pistons, etc.).
In order to start with a switch, the chainsaw would need some equivalent to an automobile’s starter motor: something that would take stored electricity (like a car battery) and jerk the motor forward. Such a mechanism would increase the weight, cost, and complexity of the chainsaw mechanism, so they don’t normally do it. Chainsaws have to be small and light enough that they can be manipulated while working, so increasing weight is likely the biggest factor.
To add to other answers, in the beginning cars didn’t have starters either, and had to be crank started. This was dangerous since once the motor started, the crank would turn with it…
My battery powered chain saw does just that, with WAY less maintenance than my previous gas powered (and somewhat more powerful) chainsaws. 🙂
If you are trimming/maintaining a not large property (3-4 acres) 3-4 times a year, a good battery powered saw and 2 batteries is about all you need. If you are clearing land, and/or using a saw frequently, more power is worth it.
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