It’s been a couple of months since I last did any real work on the Bonsai RepStrap. My money’s allways close to the line, and most of it’s been tied up in T-shirt stock. However tonight I bit the bullet and ordered the next batch of parts. So I now have on their way to me:

  • 30x Miniature bearings, 3x10x4mm
  • 10x M3 flanged nyloc nuts
  • 40x M3 10mm stainless pan-head machine screws
  • 50x M3 15mm eye-bolts
  • 50x 0.7mm double-barrel crimp sleeves

Now, a lot of them may sound like pretty generic parts, but I’ve done my research to get just the right ones. The crimp sleeves for example aren’t the plain crimp tubes used in jewellery, but the sort used in sea-fishing. They’re double-barrelled so wires don’t get crossed inside them when crimped and get damaged and weakened. Small (and light) bearings at a good price were also a trick to find. But not as hard to find as the machine-thread eye bolts. While some place do them down to maybe M6, I could only find a single shop providing them with an M3 thread, and only in bags of 50.

To be honest, I’d prefer to have used M3 hook bolts, but couldn’t find anywhere that did them at all. Maybe later something will turn up.

They’ll be used in the wire tensioning system along with the flanged nuts and wire crimps. The crimps will hold secure loops of 0.7mm nylon-coated steel cable. Those loops will be fed through the eye bolts. The eye bolts will be retained in a recess by the flanged nuts. The recess will stop the bolt from turning as the nut is adjusted, pulling the bolt further into the recess and putting more tension on the drive wire that runs around the geared capstan.

That’s the theory anyway.

Until they turn up, back to casting and designing T-shirts.

Off to Focus in the morning, looking for some specific storage boxes and some 12mm mouldings. In turn to build the new cargo hauler around, and tidy up the rough Bonsai frame.

Took a momment out to update the RepRap wiki entry on my printer project.

http://reprap.org/wiki/Bonsai_RepStrap

I think some of the connections I made at the convention at the weekend may be a great deal of help in building them too.

I’m wondering that when the first few machines are working, that I might loan them out to a few artists to see what they can do with them. See what less hardcore engineering purposes they can find for them.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Reprap prototype PSU is done and ready for the stepper controllers to arrive now. All boxed up nicely. If memory serves, it didn’t have a fan when it was in the fax machine, so should be fine in the enclosure. At worse I might have to drill it some extra air holes.
Mains lamp, some (vintage) terminal posts, switch and IEC C14 socket.

Even took the engraver to the front panel to mark out the various terminals and added a couple of ferrite beads to the lines to be on the safe side, and used some cable wrap to keep the wires tidy.

Today I also finally removed the piston and cam off the old compressor pump, and filed down a pully to fit. I’ve hooked this up to the 3rd party headstock from the Black and Decker extruded aluminium wood lathe I found last year. It’s meant to be run by a type of drill they no longer make, so the compressor motor should be easily powerful enough. Currently getting a head speed of about 3200rpm, so it’s currently about twice as fast as it needs to be. Will see about swapping the headstock pully for something larger (I have one, but getting the old one off will be a pain).
It’s not urgent, but it’s sitting around and there’s a friend who should be able to use it once it’s basically working.
Also made a control box for it, currently a simple latching safety power switch (see background of first image) from a broken garden shredder and an old RS project box. If I find a spare suitably rated rheostat I may add a limited speed controller.

Also the sewing for the set of “Navi” wings was mostly done today, but one of the blue plastic rods snapped while trying to flex it into it’s “pocket”.
After some considerable swearing and therapeutic angle-grinder time (see above compressor pump), I will tomorrow attempt to construct a coupler out of clear perspex rod and use it to join the two broken ends, as the stress on them will likely be more than any other repair would take. this may mean purposefully breaking and repairing the opposite wing to match.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Some progress with inventory today, but got a bit sidelined into working on the old fax machine PSU, which puts out 5v and 24v, and should be powerful enough to run the stepper control circuits.

Boxing it up is fairly important, especially if there’s the chance of metal filings wandering around.

Using an old comms relay box of some sort and making a new front panel out of some aluminium plate from some Dell drive tray blanks.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

Spent most of today creating inventory templates for workshop stock. After unexpectedly running out of materials yesterday, I’ve realised I need to manage it all much more actively.

I also have an order of electronic sundries on their way to me, including some Darlington transistor arrays and stepper-driver ICs. This should be enough to get prototyping of the Bonsai Repstrap to the next stage.
Comparing the price of dedicated driver ICs, I’m wondering if I couldn’t make quite a saving (on cost and part-count) by using a Sanguino rather than direct Paralell-port control.
The Reprap still uses stepper driver ICs as well, but could a Sanguino drive the Darlington array directly? It sounds like it would have enough processing power spare to manage the sequencing.

Anyway, time to see how the castings are doing in the heated cabinet, and get some inventory done.

[20/06/2010: Amalgamating old posts from “Dreamwidth Creative Blog” into sci-fi-fox.com to re-purpose DW blog account.]

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