How do I make flexible track pieces

[matencio (Mike Atencio)]

I’m building a marble racing track. As the marble reached each corner, I found I needed the corners to be flexible.

The marble rolls downhill and the corners need to be higher going into the corner and lower going out.

I can use the cuts like the picture for straitaways but I can’t figure out how to make them work going around a 180 degree corner. Can anyone help?

[ednisley]

@matencio

how to make them work going around a 180 degree corner

If I understand the geometry correctly, a solid 180° turn looks like a flat U shape, but you need a U shape with a 3D twist and a change in altitude along it.

Perhaps eliminating the solid borders along the middle section of the U will allow the living hinge enough flex. The ends need solid borders (and maybe a solid end plate) to join the rest of the track, so you must splice / join / weld those sections onto the end of the bendy hinge.

I tried a quick-n-dirty hack by copying one section of a living hinge around a circle path, so this is twice as much curve as you need:

Getting enough flex along the outside without having the inside fall apart is left as an exercise for the motivated designer.

[parsec (FerAS)]

Maybe with your Bowing Pin or Diamond shapes.
Maybe something like this will work

to be able to close the interior more and with less stress on the pieces.

[matencio (Mike Atencio)]

That’s a thought.

[matencio (Mike Atencio)]

@ednisley

If I understand the geometry correctly, a solid 180° turn looks like a flat U shape, but you need a U shape with a 3D twist and a change in altitude along it.

Perhaps eliminating the solid borders along the middle section of the U will allow the living hinge enough flex. The ends need solid borders (and maybe a solid end plate) to join the rest of the track, so you must splice / join / weld those sections onto the end of the bendy hinge.

I tried a quick-n-dirty hack by copying one section of a living hinge around a circle path , so this is twice as much curve as you need:

Getting enough flex along the outside without having the inside fall apart is left as an exercise for the motivated designer.

I finally figured out how to copy the quote. Can you make a how-to video for us. I think this is something people look at and give up. I think if we did an offset around the edges, and then did the cut lines as you did, it would work. It’s just the cut lines going to the edges, and the no cut lines that go to the offsets lines but not to the outside edge will have to be manually scaled to make it work correctly on the inside and the outside edges. With the straight track pieces, that’s what I have to do, so I know it works, but I cannot figure out how to make them go around as you did in your image above - which, by the way, is really cool.

[ednisley]

@matencio

a how-to video

I’m a dead loss at video; I have a face made for radio.

Here’s the outline:

• Draw a circle of the inner diameter you want
• Scale the hinge so the width matches the roadway you want
• Rotate it to put the width parallel to the X axis
• Ungroup it until you can copy / duplicate a single repeating slice parallel to the X axis
• Modify the slice as needed
• Dock it against the right side of the circle
• Select it, then Shift-select the circle (the order matters!)
• Click the Circular array (a.k.a Radial Array) tool
• Twiddle the parameters until you get the spacing you need
• Ungroup the result as needed
• Delete any parts you don’t need
• Profit!

[matencio (Mike Atencio)]

@ednisley

I’m a dead loss at video; I have a face made for radio.

Here’s the outline:

• Draw a circle of the inner diameter you want
• Scale the hinge so the width matches the roadway you want
• Rotate it to put the width parallel to the X axis
• Ungroup it until you can copy / duplicate a single repeating slice parallel to the X axis
• Modify the slice as needed
• Dock it against the right side of the circle
• Select it, then Shift-select the circle (the order matters!)
• Click the Circular array (a.k.a Radial Array) tool
• Twiddle the parameters until you get the spacing you need
• Ungroup the result as needed
• Delete any parts you don’t need
• Profit!

I can do a video if I can figure it out. But it’s the skills part I’m missing. I’ll give it a try. Thank you.

[matencio (Mike Atencio)]

@ednisley I’m going to give it a try. Here we go. Check back in a few hours to see what I come up with.