Starting force of a falling object on a compound lever

[Builder89]

I just overlaid the free body diagram onto the bike for context.

What is wrong with the post #46 diagram? It is the same as in the bike diagram above. You mean you think it has wrong dimensions?

which of the connections in the linkage are free joints?

All points on the triangle are pivots.

Even if they are all free joints, the FR force is not constrained to act along the rod that goes to the rear wheel

You lost me here. I have no idea what you're talking about past this point. "not constrained to act along the rod"? generate force in "any direction"? make "110 degrees as unknown"?

FR confusion? FR is still the same, the force the right point of the triangle feels in the down,right direction.

 

[haruspex]

I think I simply don't understand your diagram in post #59. The way the load is transferred to the shock looks crazy. It couldn't work.
The confusion over F_R comes from the diagram in post #33, where it seems to have been used in place of F_A.

 

[JBA]

Is the overall length of the swing arm still 495 mm and the distance from the swing arm front pivot to FM 102 mm?

Just for my education, what is the primary reason/purpose for this linkage system?

 

[Builder89]

Sorry for the confusion. FR is not FA. FA is a vertical force applied from the ground on the wheel. FR = FS in the triangle model. (Force Right = Force Shock)

Yes, 495 and 102 are the distances from right end to left end pivot and FM mount point to left end pivot.

The purpose is to multiply the distance the shock is compressed. The right end of the triangle will move further than the FM mount point. The dimensions of the linkage can also be manipulated to create a non linear force on the shock through the wheel travel... for example becoming more stiff as approaching 100% compression or other patterns.

haruspex, I'm not sure which part is looking like it doesn't work. wheel pushes up on swing arm which rotates about the attach point on the left end. It pushes up on the FM mount point which pushes the triangle up. The triangle left side is held down by the linkage bar attached to it. The right side of the triangle rotates up and left as the bottom is pushed up and the left side moves more slightly up and to the left.

 

[haruspex]

Sorry for the confusion. FR is not FA. FA is a vertical force applied from the ground on the wheel. FR = FS in the triangle model. (Force Right = Force Shock)

Yes, 495 and 102 are the distances from right end to left end pivot and FM mount point to left end pivot.

The purpose is to multiply the distance the shock is compressed. The right end of the triangle will move further than the FM mount point. The dimensions of the linkage can also be manipulated to create a non linear force on the shock through the wheel travel... for example becoming more stiff as approaching 100% compression or other patterns.

haruspex, I'm not sure which part is looking like it doesn't work. wheel pushes up on swing arm which rotates about the attach point on the left end. It pushes up on the FM mount point which pushes the triangle up. The triangle left side is held down by the linkage bar attached to it. The right side of the triangle rotates up and left as the bottom is pushed up and the left side moves more slightly up and to the left.

I don't think I am going to understand that latest diagram unless you indicate on it which intersections of lines are actual joints (rather than one member passing behind another) and which of the joints are pivots. While you are at it, please assign a label to each joint to aid discussion.

 

[JBA]

One general comment on your plan to " lengthen the stroke of the shock" since the shock and spring are operating in parallel you should realize that the force that you lever applies to the spring for a given FM will by reduced in proportion to the amount that you increase the lever length (if the lever length is doubled relative to the wheel travel; then, the force it applies to the spring/shock connection is 1/2 of the that of the shorter lever); and as a result the spring compression length for a given load will also reduce proportionally; and you will find that there is no actual additional shock/spring travel provided by your lever mechanism at all.