Wednesday, December 15, 2021

The Newt and the Apple

This story was inspired by an apple I was putting in the girls lunches this morning. It's not very long...

Once upon a time there was a newt named Isaac who was very interested in physics. He used to spend hours mulling over the great, imponderable questions of the time, such as the motion of the heavenly bodies, or whether the chicken came before the egg, or the other way round. He was well known amongst the other physicists of the time, who would treat him with great respect and often referred to him as Sir Isaac.

At night Sir Isaac the Newt would go up to his observatory and train his telescope on the night sky, studying the stars and planets, and writing indecipherable notes on stacks of disorganized notebooks that littered his study. As dawn approached, he would move his telescope to focus on a neighboring farm, and spy on the hens as they performed their morning rituals.

The days, if the weather was fine, Sir Isaac would often spend sitting under a tree, reading and re-reading his notes, or simply lost in thought.

It was on a day such as this that an Evil Squirrel happened to climb the tree under which Sir Isaac was sitting. (Now, my astute reader, you are most probably saying to yourself that it’s a bit redundant to say “an Evil Squirrel”, like saying “a Large Elephant” or “a Wet Fish”. So let us instead say that this was an Especially Evil Squirrel.)

The Especially Evil Squirrel spotted the newt, sitting under the tree, seemingly transfixed, and hatched an Evil Plan. The squirrel found a large apple and rolled it along a branch until it was just above the newt’s head. Then he pushed it over the edge and waited, listening for the thump.

Now you might think that this would be an opportunity for great scientific discovery. But, dear reader, you are forgetting one important fact: Sir Isaac was a newt.

A newt, as you are no doubt aware, is much smaller than an apple. Especially a large apple.

Sir Isaac, I’m sad to tell you, was squashed flat. And, with his untimely demise, so too were lost the many great scientific and philosophical discoveries that he might otherwise have brought to the world.

Only the chickens at the neighboring farm were relieved, for they did not like being spied upon and were happy to regain their privacy.


Tuesday, December 14, 2021

Making a "Tintin" Rocket on Mini-Lathe and Mill

I've been making a series of model rockets on lately, using the mini-lathe and mini-mill. Most of them have been somewhat 1950's/Flash Gorday inspired, with either tritium inserts or miniature LED flashlights inside to make them glow in the dark.

I decided to make one inspired by the Tintin rocket a birthday present for my brother, since he liked the Tintin books growing up. (I read them too, but, at the time, prefered Asterix.)

Materials

Since I was planning to paint it anyway, I decided to stick with aluminium (6061). I used one piece of 7/8" rod for the main fuselage, 1/2" rod for the feet, and 2" x 1/8" bar for the legs. Also some 1/8" stainless rode for the antenna and some clear Alumite to fill the nose-cone.

The Fusalage

The main fusalage is made in two parts: the nose-cone which is about 1 1/2" long and has three portals, and the body, which is about 4 1/2" long and solid. (The portal are not a feature of the rocket in the Tintin books. If you want to be more correct, you can save yourself some trouble and make the fuselage as as single piece. But, as I said this is intented to be "inspired by" the Tintin rocket and not a replica).

First the nose cone was cut and faced. Then drilled out to a depth of about 1" and threaded with an M10-fine thread. (Sorry for mixing units, but those were dies and taps I had handy).

Next I started on the body. The section was cut about 1" more than the final length. I turned down a section about 3/4" long down to 1/2": this was to hold it by and got removed later. Then, on the other end turned and cut a screw thread a little over 1/4" long:

I put the two parts together, blued, and scratched in some reference marks. (I wanted the portals to line up with the mid-points between the legs.)

Next, I switched to the mini-mill to drill the portals. I used a rotary table in in to make them at 120 degrees to each other. Finished with a 5/16" end mill:

Then mounted the body on the mill and milled three slots for the legs, 1/2" long and 3/5" deep using the 1/8" end mill.

The two parts together:

Next, I wrapped the nose cone with tape and filled it with Alumite resin:


The resin needs at least 24 hours to harden. Fortunately I accidentally uploaded a photo of Winnie along with the photos from my phone for this project, so we have something to look at while we're waiting.

Done waiting. The nose is ready for the next step.


Next I drilled some holes in the acrylic to accommodate some tritium vials. In this case I decided to go with three smaller vials of different colours, one for each window.

At this point the two parts are put back together and go back to the lathe to finish. Most of the hard work is now done.

Back on the lathe, I drilled a hole 1/4 deep for the antenna.

Then I started a series of cuts, at different angles, using the compound. First cut at 40 degrees took the longest.

Then I started doing more cuts, reducing the angle in 5 degree decrements:

When I got close to zero degrees, I moved the body forward in the chuck. This is where the 1/2" end section came in. On the back half cuts were much shallower, in the range 1-5 degrees.

I finished off with emory paper and cut off the end stub. Finally I added the antena using a spot of green loctite.

Shock Absorbers

The shock-absorbers/feet were made in a similar way to the body of the rocket, though simpler and also more rounded on top.

First I cut three pieces of the 1/2" rod, faced them and turned down a 1/2" section in order to hold them in the chuck.

Next I milled the slots for the legs, 1/2" long and half the thickness of the rod:

Then back to the lathe for shaping. For the shock-absorbers I shaped the bottom first and then the tops.

Legs

The lets were made out or the 1/8" by 2" aluminium bar. I started by cutting three blanks, milled the edges to be square and parallel, and then glued the three parts together using four spots of superglue.

I used the mill to roughly shape the block of leg pieces with a series of cuts at different angles. (A vertical band saw would have been ideal here, but I don't have one and am running out of space.)

Final shaping was done with a file in the vice, before breaking the legs apart:

Then I did a quick pre-assembly to check that all the parts fit together and looked about right:

The legs were finished off with wet/dry emory paper and a Dremel tool. I also used the Dremel to round the top edges of the legs where they fit into the body, otherwise there would be a gap:

Assembly and Painting

At this point all the individual pieces were finished:

I assembled using "extra-time" appoxy and did a little more cleanup:

It was tempting to just do a little more polishing and leave it like this, but I stuck with the original plan to paint it.

I masked the antenna and portals and then gave it three coats of white enamel paint using an airbrush:

When it had dried thoroughly, I wrapped the rocket with several rings of 1/2" masking tape. Then cut six vertical lines in the tape, and peeled away alterntate squares:

Finally added several coats of red enamel, peeled of the remaining masking tape, and DONE!