Wikipedia:Reference desk/Archives/Miscellaneous/2021 November 16

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November 16

Engine rotation direction

Is there an agreed convention about the direction of rotation of automotive engines? I've been watching various tv shows about custom vehicle builders where they seem to almost arbitrarily mix engines and transmissions and nobody ever says anything about whether they have a clockwise engine and anti-clockwise transmission or vice-versa. Roger (Dodger67) (talk) 20:53, 16 November 2021 (UTC)

If you take an engine block and rotate it by a half turn (180°) without changing your own point of view, clockwise rotation becomes anti-clockwise. If the design of the engine block is symmetric, you can mount it either way.  --Lambiam 09:54, 17 November 2021 (UTC)

I'm not sure this is relevant today, but I can recall when it was often necessary to use a starting handle, and (because most people are right-handed) they always went clockwise (as you face the front of the vehicle). I assumed this convention was continued.--Shantavira|^{feed me} 10:13, 17 November 2021 (UTC)

Is there a reason why clockwise would generally be better for right-handed people? I'm mostly right-handed (but also left-eye dominant - don't know if that is relevant), and tend to find it easier to crank or stir things anti-clockwise when using my right hand (and clockwise if using my left). Iapetus (talk) 13:11, 17 November 2021 (UTC)

I believe that when writing a figure 'eight' 80% of people start by moving the pen anticlockwise. I could be wrong as I'm not sure how they write it, being one of the 20% who write it the other way. 86.6.4.102 (talk) 13:59, 17 November 2021 (UTC)

Starting a figure eight anti-clockwise means the pen moves away from the hand at the beginning, which is easier for right-handed people. Cranking clockwise means that right-handed people can get their weight onto the crank-handle on the down-stroke, which helps. No citations for either, but obvious to anyone who's ever done either. DuncanHill (talk) 14:14, 17 November 2021 (UTC)

Clockwise is better because it reinforces that you start by pulling the crank up, not pushing it down. When doing it, you walk up and grab the crank with your right hand (because you are right handed). Then, you step to the left and rotate the crank is in front of you and the car is to your left. If you imagine trying to rotate the other way, it is difficult. You have to grab the crank in an unnatural way. Now, with the car on your left and the crank in front of you, you start it by pulling up, not pushing down. You rotate the crank until it is at the bottom. Then, you pull up quickly. Hopefully the engine starts. Pulling up from this side of the crank is easier than from the other side because on the other side you have to reach over the center of the crank. Finally, "why" do you have to pull up? It is for safety. Sometimes, the engine will fire and jerk the crank in the opposite direction. If you pull up and it jerks back down, it is an annoyance. You might fall forward. But, if you push down and it jerks back, the crank can spin right into your chin and cause severe injury (even death). Therefore, in the end, the engines rotated clockwise. 97.82.165.112 (talk) 18:35, 17 November 2021 (UTC)