Thread: Man fixes Land Rover with a potato.

The peculiar thing is a Potato won't act as a capacitor ("condenser"). It'll behave much like a voltage dependent resistor, and a highly non-linear one at that.

I suppose the role of the "condenser" in the old Kettering ignition is to quench/prevent an arc across the points, and a "variable potato" should perform that role as long as it remains moist and rather than returning the energy to the circuit as the capacitor would, turning it into heat. As a bonus if you drove far enough, by the time it was no longer viable it'd be about baked to perfection from the inside out.

Nice find.

Originally Posted by BradC

The peculiar thing is a Potato won't act as a capacitor ("condenser"). It'll behave much like a voltage dependent resistor, and a highly non-linear one at that.

I suppose the role of the "condenser" in the old Kettering ignition is to quench/prevent an arc across the points, and a "variable potato" should perform that role as long as it remains moist and rather than returning the energy to the circuit as the capacitor would, turning it into heat. As a bonus if you drove far enough, by the time it was no longer viable it'd be about baked to perfection from the inside out.

Nice find.

How do you know this stuff??
I’ll never look at a potato the same way again.
A voltage dependent resistor.......

Excellent. Until this the only mechanical uses I knew of potatoes was to use a cut one to wipe on my windscreen when the wipers packed up, and to shove up the exhaust of someone's car to bamboozle them when it stopped.

"Bamboozle"... * ka-boom *

Originally Posted by SeanC

How do you know this stuff??
I’ll never look at a potato the same way again.
A voltage dependent resistor.......

The same way as I won a bet for connecting a security system keypad to the panel using two pieces of wet string. Admittedly it was RS485 over string soaked in a strong brine, but that didn't make the scotch I won taste any worse.

The potato started out as a simple potato battery. A few beers later that turned into a "how long might it take to cook a potato by using it as a resistor?" leading into shoving 100V or so through it using a variable power supply. We noticed as the voltage went up, the current increased in a "faster than linear" fashion and the power supplies ran out of ergs far before they should have based on the resistance at 10V.

Beer often makes mundane things sound like a good idea. Not often the "knowledge" gained is particularly useful however.

That beats my story of setting the points on an old Ford Escort, with a piece of cardboard I tore off a biscuit box, that I had in my bag of shopping while walking home one day when I was young, ermm younger than I am now. I came across a couple of guys whose car had stopped beside the road and wouldn't start, I diagnosed that the points had slipped, but without a feeler gauge couldn't reset them, so used the thin cardboard to do so. They were really grateful and would thereafter often give me a lift to the shops and back whenever they would see me.

Originally Posted by RANDLOVER

That beats my story of setting the points on an old Ford Escort, with a piece of cardboard I tore off a biscuit box, that I had in my bag of shopping while walking home one day when I was young, ermm younger than I am now. I came across a couple of guys whose car had stopped beside the road and wouldn't start, I diagnosed that the points had slipped, but without a feeler gauge couldn't reset them, so used the thin cardboard to do so. They were really grateful and would thereafter often give me a lift to the shops and back whenever they would see me.

The top or bottom of a matchbox was the tool of choice for me.
Also, just in case you ever need it, the assembly clearance for the hydraulic tappets on early small block Chev motors, was equal to two hacksaw blades, (offset so the teeth are overlapping).

At an early age I learned that the normal spark plug gap was the thickness of a thumbnail!