Saturday, July 28, 2012

An harmonograph

Ever since my last visit to the MSMEE exhibition, two years ago, I have been wanting to build myself an harmonograph.  Just after that exhibition, two years ago, I was cleaning out my shed and found some old curtain rods which I decided would be perfect for the project and leaned them up beside the doorway instead of throwing them out.  I was keen to build a design that I could pack away neatly so I made the box long enough to store the longest spars.  The gimbals are turned from aluminium and pivots made from M3 allthread.  The paper platform is simply some masonite glued to a wooden block with a hole in the middle so that is sits tightly on the spar.

One of the surprises has been just how much variability there is in the setup and how much tuning is required to get good pictures.

The finished harmonograph

Some of my best works

Gimbal detail from underneath. One set of bottom pivots fitted to the box and the components for the second gimbal ready to go.

Neatly packed away

Hours of entertainment

Whilst researching construction details I came across Wayne Schmidt's multi-topic site.  The site covers everything from kaleidoscopes to electric rocket engines and deserves a nomination to the tinkerers hall of fame.  

Saturday, July 14, 2012

Bread and butter boat

Almost six months ago I had a great idea to make a toy pond yacht from my windfall Sydney cedar.  I have never used "bread and butter" construction method but thought it would be ideal for a toy yacht because it should be fairly quick to carve out a small pilot cutter.  I started with a central board and cut the profile to include the keel and cut three additional boards each side.  It's not exactly to plan but the basic shape is right.

I made a point of keeping the hull length long enough to test buoyancy in the kitchen sink and found the hull floated slightly to one side and the stern sunk right down to the waterline.  I corrected the center of gravity with a 250gram block of cheese and estimated about 25ml of lead would do the job.

Wednesday, July 4, 2012


All that time in my workshop sanding, scraping, filling, padding and polishing I kept myself going with one thought.  By golly I'm going to heat this workshop by next winter.  Could my rekindled welding interest be enough to put together a Yukon stove by next winter?  Watch this space.

Can't place the tune on the Collaro Classic radiogram?  
It's an old 78 called "Parkin' in the moonlight" by Maurice Winnick and his band from 1923.