El Beast - Initial design phase, comments and critique welcomed!

**Zeeflyboy** · 24-05-2018

Decided to re-vist my original plans for a belt tensioning system.

I whipped up this design

And then set about making it. The idler I made from alu tubing which I turned down and bored out for the bearing pockets.

I also needed to make the upright piece which the whole assembly rolls around. Turned this from silver steel:

Final part that needed turning was the little rotating piece through which the threaded rod will go... Made a small jig to make sure I drilled it centrally, which could also then be flipped and guide the tap straight through.

I decided to try 3D printing the main parts in the CF composite material I use for functional parts and I must admit I was amazed at just how strong it's come out. I upped the infill percentage and used extra perimeters to beef up the part even more and the result feels like it could survive being run over by a truck... my backup plan was to make the frame parts from alu plate but it won't be needed.

Even more surprising is that I modelled the M6 thread in the bearing tube mating part and it printed fully functional... didn't even need to run a tap through it. That's the smallest thread I've tried printing so far and I'm suitably impressed :)

Final bunch of parts:

And test fitting

Untensioned:

Tensioned (can't fully tension for two reasons - screw thread isn't long enough, and the smaller pulley pulls in towards the bigger one without the top bearing counter plate.... but it gets the gist across):

Pretty chuffed with that little bit of design I have to say... worked out nicely. Still need to make a knurled knob and order some m6 threaded rod to make the proper tensioner adjustment, and I also need to make the little collar that goes on the m5 standoff to help capture the rod end.

**routercnc** · 24-05-2018

It is very OTT but you look like you are having fun so go for it!

How about 3D printing the adjuster knob - put an internal thread in it and secure with a lock/jam nut.

**Zeeflyboy** · 24-05-2018

Originally Posted by routercnc

It is very OTT but you look like you are having fun so go for it!

How about 3D printing the adjuster knob - put an internal thread in it and secure with a lock/jam nut.

A lot of what I do in life could be described as OTT lol...

I've done 3D printed knobs before, in fact the 3D printer is rocking one. Not quite as pretty as a nice knurled alu one though.

**Chaz** · 25-05-2018

Originally Posted by Zeeflyboy

A lot of what I do in life could be described as OTT lol...

I've done 3D printed knobs before, in fact the 3D printer is rocking one. Not quite as pretty as a nice knurled alu one though.

Very nice stuff, wish I had such a creative mind.

**Snapper** · 25-05-2018

Originally Posted by Zeeflyboy

A lot of what I do in life could be described as OTT lol...

I've done 3D printed knobs before, in fact the 3D printer is rocking one. Not quite as pretty as a nice knurled alu one though.

Its a very nice knurl you pulled off on the last one, how many goes did that take to get right?

**AVF** · 25-05-2018

This is all looking very nice and a really wonderful build!
Would you care to share the Fusion files of the Z-axis only perhaps...? :-)
Cheers - Ard

**Nickhofen** · 25-05-2018

Zeeflyboy this Z axis is a masterpiece, what is the travel of it?

**Zeeflyboy** · 25-05-2018

Cheers :)

It has a total travel of 178mm

AVF - not yet, but I may make files available later.

**Zeeflyboy** · 25-05-2018

Originally Posted by Snapper

Its a very nice knurl you pulled off on the last one, how many goes did that take to get right?

Just the one attempt actually! I did use a knurl calculator to arrive at a suitable diameter for the knob, so that probably helped a little. I'd actually like a coarser Knurl, need to buy some 1mm wheels for my knurling device.

**Zeeflyboy** · 29-05-2018

Sorted out the ball nut greasing arrangement... So obviously I didn't fancy stripping down the whole thing every time the ball screw needed a bit of grease. I came up with this solution:

Made a small hex piece with an M6 thread on the lathe

3D printed a plug with m20x1 thread (to match the hole in the face plate) in my new PA-CF nylon/carbon fibre material and added a 4mm hose barb.

Added a hose barb and 90 degree connector to the ball nut (locked in with hydraulic sealant to the position required) and a silicone hose to connect the two pieces. This picture gives an idea of how the arrangement works:

And done: