Saturday, June 11, 2005


Carriages from Polymorph

My friend Keith was round, kindly offering to make up a wooden base for the new prototype here in New Zealand. It was during the process of explaining what we wanted it for that I tried to demonstrate a carriage mechanism, and walloped a saddle together out of Polymorph that sat around a ground steel bar. It worked beautifully. The low friction and close fit formed the perfect saddle on the carriage guide bar.

The trick was to slit the underside of the encircling Polymorph so that it would slide freely on the bar. Chopping out a bit of the centre section further reduced friction. As you can see from the photos, we also melted a Meccano bolt into it, and can remove it to attach various fittings. The insertion was best done by warming and pushing the bolt in with a soldering iron.

This method has the added advantage that, as long as the carriage bars are parallel, it does not really matter what size they are. Polymorph supplies permitting, we'll try to build an entire carriage mechanism based on Polymorph and Meccano - which we can replace with manufactured components as we progress.

We've also produced a detachable 0.32mm solder nozzle made from a couple of bits of M6 bolt and an M6 nut. The nozzle part is soldered to the M6 nut, and PTFE tape ensures a leak-free join onto the main bolt. We did use mostly lead-free solder here (melting point 220C), but it would not tin the brass and we had to resort to 60/40 solder to do that.

Vik :v)

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