HELP with piston animation

[Stanley91]

Hi

I'm Completely lost in trying to get this animation of a piston I have set up working properly

I want it to move in the same ordination as a mechanical piston would but its not

piston.xlsm

Could someone help please been stuck on it for weeks

Thanks

[protonLeah]

I didn't have much time to look at this, but I didn't see where you were calculating the coords of the left end of the piston as an offset of the left end (point_1) of bar_1 + the length of bar_1...

[Stanley91]

Ah yeah sorry I was messing around with the piston off set and forgot to change it back here it is working properly.

piston.xlsm

Any idea how I go about calculating the motion of __bar_1 (connecting rod). That is where I'm completely lost

Thanks

[protonLeah]

Some thoughts.
1. I think that the connecting rod, _bar_1, should be pinned at the center of the left end of the piston; that pin should be the center of rotation of the bar, moving only horizontally.

2. As the small bar rotates through a full 360^o, the connecting rod only varies through a total angle about 72^o, i.e. about 36^o (Sin^-1(60/100)) on either side of horizontal.

3. With both rods horizontal, small rod at 0^o and connecting rod at 180^o, as the small rod rotates clockwise down to -90^o (270^o?), the connecting rod rotates downward, counterclockwise to its maximum, about 215^o.

As the small rod continues upwards to 180^o the connecting rod also rotates clockwise upwards back to 180^o. The small rod continues its CW rotation up to 90^o and the connecting rod reaches its maximum clockwise at 145^o.

4. I'm not sure where you calculate your angles, or what you consider positive and negative rotation angles/directions.

[Stanley91]

Thanks for the help with this. Didnt get a chance to follow what you said until this morning. Been working on it since then and have it working now. Thanks again

[protonLeah]

Can I see??

[Stanley91]

yeah sure ill attach it now

[Stanley91]

Keep in mind that is a "roughwork" excel sheet I use, to test new mechanisms for a much more advanced worksheet I'm building with many mechanisms. So the worksheet is a bit messy :p

[protonLeah]

Sorry, the attachment is invalid...

[Stanley91]

Not sure what happened there, should work now?

piston.xlsm