# Question about engine reaction torque from gas forces

in the figure below the reaction torque equation is given by Fg41.x trying to rock the ground plane about the O2 pivot due to gas forces . My question is if the piston with the cylinder whole assembly were shifted down by a distance L as shown in figure , will the horizontal (Fg) force contribute to the reaction torque equation ? Because this gas force was not creating a moment in the first case since its moment arm was passing through the pivot , but now after shifting L distance, a moment vertical arm is in present i.e. (T12 will now become = Fg.L+Fg41.x) , is that true?

Edit

In this case in the figure with an offset length=L won't the gas force acting on the wall of the cylinder (Fg41x * L) generate a moment about O2 pivot which will try to rock the cylinder ground link 1 around this O2 pivot? and thus the total gas torque would be the torque in the first case (were the Fg41x moment arm was passing through the pivot and thus produce no moment) + the new generated moment from Fg41x?

I think the component force ($$F_H$$) is responsible in producing the torque.

• yes that is true r13 , but i am talking about the shaking moment which will tend to rock the ground plane 1 about the fixed pivot O2 . Here it was assumed to be equal with the torque at the crankshaft but what would happen if the distance L was in present will The Fg on the ground also produce torque? May 13 at 22:28
• No, Fg produces work (F*x) by moving linearly in the cylinder housing, it is responsible to produce the thrust but does not involve in producing the torque about O2 directly. Maybe I've some misunderstanding. Why not provide a hand-drawn diagram to express your thinking.
– r13
May 14 at 2:34
• I have just uploaded an answer with a drawn diagram to express my thinking for you ........ you can now see it if you want to help :) May 14 at 3:08
• No, as I said before, Fg has no direct link to O2, though it helps to produce the thrust in rod 3, it does not involve the rotation directly. Note T = Fg*L will be valid only if there is a direct link between C & O2.
– r13
May 14 at 3:35

@r13 here is a figure that may help you understand me see here in this case in the figure with an offset length=L won't the gas force acting on the wall of the cylinder (Fg41x * L) generate a moment about O2 pivot which will try to rock the cylinder ground link 1 around this O2 pivot? and thus the total gas torque would be the torque in the first case (were the Fg41x moment arm was passing through the pivot and thus produce no moment) + the new generated moment from Fg41x?

• Don't provide additional information as an answer. Include it as an edit to the question & then notify who ever you want via a comment directed to them by place an @ before their id name.
– Fred
May 14 at 7:22
• I've made the edit, see if it is what you want.
– Fred
May 14 at 7:28