Yesterday we learned about how to calculate the diagonal distance between two walls in a house. We had to use something called squares and square root. Squares are easy, you just multiply a number by itself. Square roots are a little more difficult. There is a process that is similar to long division that Issac Newton developed.

First, let's do an approximation of square root to one decimal point. Then we'll get into the nitty gritty of how to do it for any number.

Believe it or not, but this is exactly how your calculator does square roots inside itself.

School House Rock Tyrannosaurus Debt

Right down to brass tacks-- how to make pottery out of mud.

Primitive Technology: Firesticks
Making fire sticks primitively from scratch, making a fire using the sticks and making and firing a small pot to test clay from the hut.
The species of wood used for the fire sticks is 'Abroma mollis'. In the hibiscus/cottonwood family (Malvaceae).

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https://www.youtube.com/shorts/vd2OWxvsg2M

Two strokes are used with oil mixed in the gas because they might be run upside down in chain saws and weed eaters.

Many small engines in chainsaws and weed eaters require "mixed gas". This means you mix oil into the gasoline. In the diagram above, you can see that air is pulled into the bottom of the crankcase and some of that oil and gasoline hits the crank. This lubricates the moving parts. Then that gas/oil/air mixture is sucked around into the cylinder to be burned.

Common mixes of gas and oil are 50 to 1 (50:1). This means for every 50ounces of gasoline you mix in one ounce of oil. It will give the gas a greenish tint. Too much oil and the engine wont run as strong and will smoke.

Did you know that a german man Rudolf Diesel invented the diesel engine? But he didn't intend for it to run on fuel from oil as we know it. he designed it to run on vegitable oil! There are people today who collect used frend fry oil from restaurants and filter it to run in their trucks and tractors.

The only problem is when it is really cold the vegitable oil is too thick to run. So you start and stop the car on diesel fuel and switch to veggie oil once it has warmed up.

The operating principle of a diesel relies on the fact that when you compress air quickly, it gets super hot. While the air is compressed and really hot, you spray in high pressure oil in a mist. The oil instantly catches fire and burns in the cylinder.

Early cotton gins ran on Lister engines. A lister is a one cylinder diesel engine that runs on veggie oil or kerosene. I have a friend in Germany who runs his lister engine off hydraulic oil from tractors and elevators. All he has to do it heat up the oil so it flows easier. So he stops and starts his engine on diesel and uses the exhaust of the engine to heat up the oil.

https://www.youtube.com/shorts/ngtrcUst-_0

This engine tops out at around 600 RPM. Most car engines idle faster than that!

How to start a lister engine. https://www.youtube.com/watch?v=jjkfaxEfSos

The last category of old farm engines I'm going to cover are "hit and miss". These engines are slow turning and never run at a steady speed. When they make power they speed up, and once they reach a certain speed, a mechanical device opens one of the valves on the head and they coast. When they slow down, that mechanism allows the normal compression and ignition cycle to work again.

When my father was a child in the 1950's a local cotton gin had a hit and miss engine that ran on kerosene with an 18foot diameter flywheel. It would run one or two seconds every 20 seconds.

These engines are not efficient at all because they do not shut off fuel when they aren't running. They continue to suck in air and depending on the model they may or may not shut off the fuel injector.

https://www.youtube.com/watch?v=fYKxwno6QUY

And to end the week, here are some facts about Diesel , Gasoline and LP gas.

Diesel fuel is actually quite difficult to catch fire at normal temperatures. You see diesel, unlike gasoline does not want to evaporate at normal temperatures. As long as diesel is below it's flash point of 125F 52C, it does not turn to vapor. You can store diesel fuel in an open top container for years at a time. A tank will be labeled "combustible". This means the flash point is above 100F.

Gasoline on the other hand starts turning to vapor at -45F -43C. So any time the temperature is above -45f, gasoline is evaporating and must be kept in a closed container. A tank will be labeled in-flammible. This means the flash point is below 100F.

LP gas boils at -44F -43C. If it is colder than -45F, you can open a bottle of propane and it will stay liquid. There are some places in the far north like Finland where they can't use propane because it gets too cold for the liquid to boil off to a gas. Liquid Propane likes to be at about 120psi at normal temperatures. If you compress it to more than 120psi, it reforms into a liquid. So if you pick up an LP tank and swing it around you can feel the liquid sloshing back and forth inside.

Here's propane in an open top bottle at less than -44F.... it's just a liquid and does not evaporate.

https://www.youtube.com/shorts/y-BXHI6yG-g