Here are some ideas for a simple (ish) mount of a stepper motor to the sluare alu tube above it, lenghtwise:
What you say?
Not bad. But how do you plan to fixate the back bracket to the motor?
A simple ty-rap would be enough I think, and much easier.
@Rien_Stouten
Via the holes at the back. Are you talking about something else maybe?
So both brackets are identical, fixating the motor in the lower case holes while the middle holes are to receive a bolt that will clamp the square tube.
The holes in the back? Unless you have a special stepper motor I’ve never seen before, there are no holes in the back other than those that are used to hold the motor together. You could use longer screws to replace those already there, but I would not recommend that.
@Rien_Stouten
I was going to use the same holes. Why not recommend? On the other hand, the back bracket might not be needed at all, the forces on the motor shaft will try to tip the motor by forcing its back side into the square tube above…
So (as you say if I got that correctly) a ziptie at the back would suffice, unless lateral rotating forces are involved due to changing directions of rotation at the motor shaft thus moving the down force from one side of the GT2 pulley to the opposite side.
@Mark_Rehorst I was going to use that metal clamp on the idler side but for motor side I thought something stronger is needed. But why keep the back bracket only? The force on the motor is at the front, I’d rather keep the front bracket and put a metal hose clamp at the back.
Steel angle would be difficult to bent and control but ALU angle is quite thin and should be easily bendable. One may even score the ALU at the bending line.
Depending on the grade of aluminum, it may get very brittle and fatigue-prone after bending. Sharp bends are likely to crack sometime down the road. Might be fine if you keep the stresses low, just something to think about.
It’s fine to take screws out of the back side of the motor as long as you leave 1-2 in at all times so the housing/stator stack doesn’t separate. If the rotor loses position inside the stator, it will weaken the permanent magnet and you’ll lose some motor torque. Not the end of the world – it’ll still run – but not exactly desirable either.
Honestly, it’s better that you simply create another post anyhow, as older things move to the bottom. This ensures more visibility for your post. In forums, new activity will bump a post, but here on G+ it doesn’t.
Why not just screw the side part into the front of the motor to stabilize in side, without the middle short part. And use one or two clamps to clamp the motor to the square bar?
The clamp on the rear part of the motor might want some way of stabilization sideway though.
@ThantiK I sometimes wonder why are we using G+, it’s pretty crappy imho and with the power google has it could me muuuch better than anything else out there… yet is just as fragmented and confusing as the plethora of Android versions and updates levels out there … pfff
@ThantiK Just did (create new post) 
@Florian_Ford I prefer Google Groups to G+, personally… nice clean forums. 3D Printer Tips, Tricks, and Reviews has a good community. https://groups.google.com/forum/#!forum/3dprintertipstricksreviews
I used to go to reprapforums for 3d printiong stuff but tried google groups, just couldn’t understand the whole hashes thing and then some… well… I might revisit. I’ll go where i’ll be able to learn the most.
@Florian_Ford The different communities are good for different things, of course.
The 3DPTTR Group I linked above is good for sustained conversations about printer builds and business models and new tech. There’s a different set of people over there, eg a LITTLE less hate on closed-source designs than you get here. (No Makerbot love, but lots of former Makerbot users who know the printers well.) It’s big on CoreXY and other XY-gantry printers, running a lot of Sailfish and RepRapFirmware over there. Whereas G+ here is much more full of Mendel/i3 and Marlin/Smoothie users. Just different community sub-populations.
Likewise, the Deltabot group is a really good place to talk about deltas. Lots of calibration and design help and advice over there. https://groups.google.com/forum/#!forum/deltabot
For really technical discussions and running ideas by other 3DP nerds, I use the 3DP Ideas Group. It’s focused on technical signal/noise ratio – no newbie help, no printer purchase recommendations, no spam. Not super active but it’s worth a one-time read-through of the thread history if nothing else. https://groups.google.com/forum/#!forum/3dp-ideas
G+ comment chains aren’t a great format for actual discussions, but posted photos being visible from the feed is really nice for stuff like concept renders. And there’s a lot of community member interaction here.
OpenBuilds is good for build logs, of course.
The RepRap forums drive me crazy… I can’t stand the amount of bad technical info that gets endlessly recirculated, so I pretty much stay away. Can’t fix everything myself.
Reddit’s format and 3dp community just annoy me. Lots of people like it though.
Facebook has a fair number of 3dp people on it too, but it’s not a very technically-experienced community so I don’t have much interest in spending time there.
There’s more, of course.
My questions and interests at the moment revolve around the more visual side (CAD, mechanical,etc) so I need this kind of photo-centric communities. Once I’ll have the design settled I am sure I’ll run into different issues with electronics, firmware, etc and of course I’ll rely on more text-heavy communities… but once you get used to one it’s kind of difficult to keep track of everything you have spread around the web …
Not bad