Mechanically-sloped platform

emerson_amaya607

I want to create a platform that can raise and lower from 4 corners. I have made a few attempts but they don't seem to work. I have tried ball mates and cylindrical mates, they can raise and lower all 4 at once, but cannot "pitch" the platform.

doc link:
https://cad.onshape.com/documents/ecada354219c1722cab9b4cc/w/0b795d298ae6a2147689955f/e/7b02c3ac3b67e1951de598d3?renderMode=0&uiState=6255acd5aa34676ff2fa3075

SethF

I think the issue is that you don't have enough degrees of freedom in your design. With those four pistons all facing straight up, as you try to tilt the platform, you're trying to turn the flat treadmill into a hypotenuse, which of course is longer than the leg of the triangle it started as. So either your pistons need to tilt around, or move around in x,y directions, or you could get real fancy and make your platform expandable.

EvanReese

Seth is right, it's an issue with the geometry, not Onshape. Here's one solution, though it might not be what you're looking for, as it would want to fall over unless the ball joints have a way to hold still. Something I've seen for these applications is a Hexapod.

steve_shubin

@emerson_amaya607

Here is another way

This method keeps the pistons locked in the upright position, BUT, to do this,
you would have to alter the design of the J-shaped brackets so that they would work in some sliding motion

The sliding motion is only set up to work on the right side for now

The J-shaped brackets on the left are still FASTENED, in this GIF




I did it by putting a slider mate in the closest corner
And by putting a cylindrical mate in the upper right corner



The ghosted Items above (in the red box)  were not moving in sync with the rest of the platform,
so I just ghosted them

You will need to work on getting them to move with the rest of the platform

steve_shubin

@emerson_amaya607

https://cad.onshape.com/documents/5ced1dff79ae8f7c34c1b192/w/ca1ff0694bc0499012134604/e/3f730fac6f1f00d8580d3af9

This will allow for the deck to be at any angle in 3D space. Of course with respect to the limits of how far the pistons can extend or contract

BUT, at least 3 of the J brackets would have to be redesigned for this setup

All the pistons are locked in vertical position

One piston is fastened at the top

Another has a slider mate at top

The remaining 2 have planar mates and are parallel to each other

So this would allow for the same size deck and vertical pistons, but it would require different ways of connecting the pistons to the deck

steve_shubin

Using the above method, each piston can be set to a different height, with all pistons locked in the vertical position, and with the bottom of each cylinder also locked into position