Slider Mate Error

arvid_hackelsjö

I am building a 4 cylinder engine but i have this problem, when i try to connect the top of the piston to the guide sketch i made using slider mate the piston moves up and out of place making the piston not spin on the axis. It worked before but i accidently deleted that and now when I'm trying to redo it it wont work. i need the piston to only move up and down.

glen_dewsbury

The piston wants a cylindrical mate with the cylinder in the block. No limits required for full motion. If the piston travels too far then you have mismatch of crank offset to cylinder height. add revolute mates at each end of connecting rods.

arvid_hackelsjö

https://forum.onshape.com/discussion/comment/116142#Comment_116142

I did try that but then the whole block starts spinning and not just the pistons going up and down

jnewth

@arvid_hackelsjö

1. Make your doc public, and post a link to it.
2. Your engine block is spinning because there is no mate (nor chain of mates) that secure it to a fixed reference frame. The way I usually solve this is by taking the part of the assembly that doesn't move like the engine block and adding a fastened mate from it to the origin. Now, whatever else happens, that block is not moving.

glen_dewsbury

Here is a sample with Block fixed and a cylindrical mate for the piston. Animate revolute 5 for smoothest replay.

https://cad.onshape.com/documents/dc45b7f3886e00ee4835c2fa/w/6f0fc43ae0332f30a049556a/e/7657e668357c9320a28d915d