Summary

Deployed and working happily on my 2nd Mendel :)

An alternative to using a piece of wood for your bed support.

To fit LM8UU and the heated bed PCB that's doing the Mendel rounds.

Instructions

Print, probably best in ABS.

Using the scad file you can set 'layerHeight' (currently 0.35) and 'thickness'. Setting 'explode' to 0 will show it all together. 'clr' sets the snap-join clearance.

I set the thickness to 5 or 6mm to test the whole idea without using too much plastic, 10mm is going to be more rigid.

Snap together. If it snaps together too easily decrease 'clr' and print again.

Pop in LM8UU bearings, push down firmly to ensure alignment, use ties to secure by ramming them into the slots and they should find their way out the other side.

Use long M3 bolts to attach to the heated bed, preferably with little springs.

The belt mount holes are 18mm apart. The centre three aren't used atm.

Might have to print just a couple of parts at a time, I'll put them up separately later.

I have printed but not yet tested on a printer, it's here in case anyone wants to play.

One pic shows the bearing holder bar printed to 10mm, which is what I'm guessing is about right for 'production'. It seems fairly sturdy anyway.

I'm considering mounting it upside down, under the smooth rods so the heated bed glides fractionally above them - should give a more usable Z range.

The bearings go into PLA printed holders more easily than they go into the ABS ones - I didn't expect that.
Keeping the rest the same, hub.stl, littleBeltClamp.stl, beltClampInner.stl and beltClampOuter.stl make a fixed and an adjustable belt clamp with tags on the hub to mount them and keep the two belt ends far apart enough to not crowd each other

Printable snap-fit Mendel Bed LM8UU