I've had a go at some wheels, they failed,

I’ve had a go at some wheels, they failed, I shall be trying a modified design and ABS rather then PLA soon…

I was testing like a lunatic on cobbles though, and a damper also burst, so not feeling so down.

It’s hard to see from the photo how the wheel failed. Care to describe?

The front rim became separated from the rest of the wheel.

So the wheel split in half? The print de-laminated along the Z axis?

I like printing ‘real’ parts and am always curious about the failure modes and how to overcome them.

One would think that the tire would do a lot for buffering the wheel from sharp impacts.

Mind sharing the print details?

Pretty much, just very near the front face. It was a very narrow section. And with the Alleycat style the spokes don’t add strength. OZ WRCs wirh spoked right to the face would be better.

Hrmm… Interesting. I am guessing it’s a thin spot kind of like what’s on the wheel’s inside near the lip of http://www.thingiverse.com/thingiview:239883 ?

I am thinking that ultimately our printed wheels will have a bit of a different profile than injection molded wheels. We can do stuff with our printers that can’t be done with injection molding & we have this delamination issue that doesn’t exist for molded parts.

How does the mass of the printed wheel compare to that of the tire and foam insert? Just wondering if we want to make lighter wheels for less spinning mass?

Also, I am thinking that the front wheels will need to be stronger along that outside lip than the rear wheels.

Yea, it gets thinner where the tyre bead sits, I’m doing exactly what you suggest and I’m limiting the space I have for the spoke design a bit more by making the rim thicker. I think I’ll set Slic3r’s solid infill threshold up a bit so the thin areas end up a solid plastic, the new narrow area infill improvements will help a lot too.

I was just playing with slic3rs settings last night for the same effect. I think its going to be a very powerful tool for us making strong parts this year.

You try thinner layer heights with infill every few layers? I’ve not done actual strenghth test but I think thinner layers gives better bonding.

I printed a spool last night at 0.05 layer height and the color is darker than at 0,1 which tells me that the plastic was fused at a higher temp. I think the nozzle ‘bleeds’ more heat into the just printed layer, giving better bonding.

I also notice that my top few layers are lighter than deeper down. Could be a function of the slightly transparent grey I am using, or could be the heat & better bonding?