Скачать или смотреть Effect of changing conrod length (rod/stroke ratio) sort of. Not a firing order video. 300RPM

Piston acceleration graph https://i.imgur.com/46TcJlz.png

Not a very informative video but I wanted to know the path the centre of mass of the connecting rod followed, and how connecting rod length affected this, don't have the necessary software so MDF and chipboard will have to do. I based the dimensions on a 4AGE (and a 4AC piston if you want to get technical)

Ignore the conrod poking out the top of the piston for the short rod versions :)

I checked the speed with my optical tachometer and the drill got up to about 300RPM on low speed. It flew apart on high speed, but the long rod held up to it OK.

I placed an LED at the centre of the big end, gudgeon pin and half way between the big and little ends of the connecting rod to trace the path of each point with a long exposure photo. It looked interesting but there was too much parallax error to be very useful, so I just traced the paths in paint.net and overlayed them on the video.

I've been working on a spreadsheet to plot the position, velocity and acceleration of a piston for a given crank angle, it ignores the effect of combustion and gas loading but I'm working a few things out, including why some of my ideas won't work. Lots to learn still.

Here are the equations if anyone wants to give them a go in excel, I was going to derive them manually but it got too hard fairly quickly so I adapted them from somewhere on the web, the graphs look about right.

E8 is the radius of the crank throw (half stroke) in metres
E9 is the centre to centre connecting rod length in metres
Column A is crank angle

Position = $E$8*COS(A12) + SQRT($E$9^2-$E$8^2*SIN(A12)^2)-$E$9

Velocity =-$E$8*SIN(A12)+ (-$E$8^2*SIN(A12)*COS(A12))/(SQRT($E$9^2-$E$8^2*SIN(A12)^2))

Acceleration =-$E$8*COS(A12)-($E$8^2*(COS(A12)^2-SIN(A12)^2)*($E$9^2-$E$8^2*SIN(A12)^2)+$E$8^4*SIN(A12)^2*COS(A12)^2)/(($E$9^2-$E$8^2*SIN(A12)^2)^(3/2))

If you are a mathemagician then good for you.