Mate connector for slider mate for tube roller on configurable diameter tube

alnis

I've been scratching my head over this for a bit now, so I thought I'd ask about a particularly weird case for defining a mate connector. Here is the part I'm importing: https://www.servocity.com/0-250-acetyl-press-fit-tube-roller.

Here is an image of a similar part (with built-in ball bearings) as an example of how the part sits on tubing:


What I'd like to have would be a mate connector for a slider mate with the tube which the roller sits on where the mate connector's position is defined by a configuration variable for the tube's outer diameter. Here is a document in which I mock up part of the target behavior: https://cad.onshape.com/documents/6569ec2e7e44e8d68bc3e677.

A simple slider mate is probably good enough in this situation because the roller may slip, so modeling a relation between its rotation and translation along the tube wouldn't be mechanically meaningful (and would add complexity/difficulty). The current document's demo assembly is configured with a table with different mates for each of the diameters of tubing. However, the goal is to have just the roller and mate connector with a configuration variable for the tube diameter so that it can be "dropped in" and used with any diameter pipe (within the 1/4" to 2" limits of the part).

Sorry if this question is a bit wordy/unclear, and thank you in advance for any help!

NeilCooke

Composite Curve will still consist of 3 segments, so a spline is the best approximation (I think it is accurate enough).

kevin_o_toole_1

FeatureScript Unified Spline will take multiple lines and arcs, and create a single spline through all curves which you can use for e.g. sketch tangent constraints. This has all the benefits of @NeilCooke 's solution, without the need for approximation.

john_mcclary

I usually create a sketch of a circle tangent to the wheel, then plop a mate connector on the center of the circle.
Then a simple slider is good.

You can configure your sketch to have different diameters and that's it.

alnis

Thank you for your response!

This is a bit of a trickier situation because the profile of the roller is an arc, a line, and another arc, so a single circle cannot cover all diameter cases with a single tangent constraint as far as I know. As the diameter grows, it comes into contact with different geometry.

Sorry if I'm not articulating this well!

NeilCooke

The easiest thing to do here would be to eyeball a spline over the roller profile and make the circle tangent to that.
https://cad.onshape.com/documents/585135a07a22a6cf2a538a57/w/84f2e412f5bce7f65d55a23d/e/1db576bed76718b866aa9189

john_mcclary

If all the faces are tangent, maybe add fillets. Could you just composite curve instead of eyeball spline?

NeilCooke

Composite Curve will still consist of 3 segments, so a spline is the best approximation (I think it is accurate enough).

alnis

Thank you for your time and responses!

I think that in the end, I'll try to create a one-off FeatureScript because it will provide an exact solution and it will be good practice. Alternatively, if that doesn't work out, I might just go with a clunkier configuration table (with ranges for the diameter to select the circle/mate connector) and configuration variable (with the exact diameter of the tube).

Thanks again!

kevin_o_toole_1

FeatureScript Unified Spline will take multiple lines and arcs, and create a single spline through all curves which you can use for e.g. sketch tangent constraints. This has all the benefits of @NeilCooke 's solution, without the need for approximation.

alnis

Thank you so much! That is exactly what I needed!

EvanReese

kevin_o_toole_1 said:

FeatureScript Unified Spline will take multiple lines and arcs, and create a single spline through all curves which you can use for e.g. sketch tangent constraints. This has all the benefits of @NeilCooke 's solution, without the need for approximation.

This is a very useful feature. Can it work for closed splines as well? I was having trouble