Having received some Stepper Motors along with the electronics, I was able to tackle some barcket design. I've started with the Y-Axis Stepper Motor mounting bracket. Had some 3mm aluminium sheet which I figure will be strong enough, and relatively easy to work. I did a drawing (below), then cut and drilled out the plate to meet the requirement. Here you go!
I've been working with 60mm between centres on the vertex joints, so you see that measurement employed again here. I positioned one of the stepper-motor mounting holes to the third corner of a equilateral triangle, and this set the motor spindle in a good position. The rest was just eye-pleasing geometry, no major science behind it. (These dimensions may not match Mendel printed parts exactly! They are my own interpretation.)
Aluminium is a nice material to work. I cut this with a hacksaw, cut the larger hole with a piercing saw, and rounded the external corners with a hand file.
Here's the bracket in place, with the stepper-motor mounted. It is very rigid once the nuts are tightened.
This view shows the purchased drive-pulley (mendel-parts). People fit that pulley the other way round also. I'm happy with it this way for now.
My washers are slightly oversized (40mm as against 30mm). Was all I could find. The old scrap piece of aluminium is a bit pitted also, but is going to serve me well I think!