I recently came across this idea:
and I was wondering why you never see them "in real life" (rather than as a novelty).
It seems to have one advantage over a crankshaft: the assembly can be narrower (perpendicular to the direction of linear motion) than the length of travel, whereas a crankshaft has to be slightly wider than the length of travel.
Any alternative technology has to be so superior to 'what's out there now' that the inevitable problems and issues with it are worth tackling, unless you get a government subsidy and a legal mandate that every one has to use it.
Boring IC engines are simply developed to the max. Their efficiency is close to theoretical maxima, especially with ECMs.
And all the government dosh is going to EVs.
Go figure.
No advantage over a Scotch Yoke?
(I didn't have internal combustions engines in mind when I asked the question.)
I see two advantages of the reciprocating R&P: you can put an axle all the way through it, instead of using crankpins [1] offset from the axis; and it can be narrower than the length of travel. I can only guess there are no real-world applications where those are important.
[1] I think you could have several yokes side by side using crankpins between wheels, a bit like an engine crankshaft, but I don't think I've seen such an arrangement.
Reading on this it looks as though both this and the scotch yoke won't last as long, nor be as efficient, as a plain old crank and conrod.
Andy
Initially I thought it had snapped a tooth, then I saw it was made with several partial teeth, maybe that was just poor implementation?
With the rack and pinion - if the rotary part turns at a steady speed the back-and-forth part has to go from steady speed one way directly to steady speed in the other, so you will have a violent, jerky reverse of momentum twice every revolution. With a crank the piston part slows and accelerates sine-wave fashion: much better.
Good point! (The Scotch yoke is also smoother at the ends.)
Have something to add? Share your thoughts — no account required.
Ask the community — no account required