It's time again to take a break from the Six Planet Genesis that I am currently working on to spend some time in the workshop teaching with my nephew as we work on our new small six planet orrery design. I really need to come up with a name for this new model. It is based on early 18th century orrery so perhaps I should start my search for a title their. I quite like Cassini, whom discovered four satellites of Saturn as well as many other astronomical discoveries based around the planets and moons featured on this orrery. In-fact as I write this I have decided to dedicate this orrery to the great astronomer Giovanni Domenico Cassini.
A cool Saturday was spent in the workshop cutting gear teeth into the blanks we turned the previous weekend. That's 2,308 teeth cut and Harry done really well not making one mistake, it's sometimes hard to believe that he is only 13. Whilst Harry cut teeth I turned the smaller gears that we did not manage to get round to the previous week.
The gear train for this orrery needs to be compact due to the base only being roughly 7" in diameter and the need to store the entire gear train within the base. We are using 40, 36, and 32 dp gears to achieve this using only 2 fixed pitches. I am proud to say that the error for the movements on this orrery is less than 0.01%.
Next weekend we begin assembly of the gear train. This will involve making the steel plates that house the gear train, cutting the planet tubes, and some turning. I will be back with an update.
Designing an orrery with my nephew
I hinted in my last post that I will be working on a new orrery that we can make in small batches.
I decided that this would also be the perfect project on which to bring in my nephew Harry as he has shown a keen interested and he can add to the skills that he has already learnt in the workshop. We are self-isolated together so why not mix things up a bit. It is also a good way to learn how to apply maths in everyday situation which is great as he will be entering into the first years of his GCSE in September, virus willing.
Above left is a prototype from 3 years ago. Only the gear train, base and the legs were completed. We will use this model to help us with the scaling of the orrery. The orrery will be scaled down so that the base diameter is approximately 7 inches. So proportions will be important.
The design will be themed on traditional orreries circa early 19th century. The photo above illustrates the style of the time. There will be six planets, Mercury to Saturn and no orbiting moons. I have not decided yet whether to turn the planets from steel or brass however there are some less common materials I will be trying out, so we will have to wait and see on that one.
The brass base will be engraved with the months and zodiac and I also want to get creative with illustrations that will suit the time period.
We will only be working on this project one day a week and I will document each day that we do.
Today after a quick briefing I had harry dismantle the gear train to count the teeth and work out their dimensions. The drawings for what I had completed so far where only scribbled down in draft form and had been lost so it was a case of retracing steps.
Once completed I had Harry practise on the lathe turning plastic discs these will be for a fixture for some work we will be completing on the mill. He done an outstanding job in machining the faces and bring them to size. Bravo.
That was it for today. A bit of practising for Harry and knocking about of ideas. I will get some technical drawings complete during the week to kick start the project. Please check back in with us next weekend.
There are 54 gears on our average Inner Planet Orrery. They range from 10 teeth all the way up to 120 teeth. I would guess the average tooth count at around 45. That is 2430 teeth. Each tooth is cut by winding the milling table one way and then the other whilst indexing round the dividing head.
Engraving takes patience and concentration from set up to finish, one misstep and I lose hours of work.
There are many skills involved in orrery making but by far the most time consuming part of building an orrery is buffing and polishing the brass. It is definitely a skill that probably isn't considered a skill but like any other skill, you can only get really good and really efficient at it after thousands of hours of practice. For best results it can only be done by hand. 10 grades of abrasive paper rubbed back and forth over the surface hundreds of times.
When I have had camera crews and photographers in for various media things to capture me working this part never makes it into the final edit.
No mater how refined the design or how mesmerising the movement an orrery will only be as good as the finish on the brass.
What better way to show of my skills with emery paper than looking at the finish using my brand new Canon camera. I uploaded a new video to Youtube of a finished Inner Planet Orrery...
Making the base for this orrery is featured in an earlier blog post.
Some people ask me why I have no sound in my videos. The answer.. because I am always contending with noise from outsde the house, inside the house, kids, cat, dog, washing machine.
The orreries are quite anyway, only a slight jangling of gears which are pleasant to listen to but hardly audible without volume on max..
Inspired by our recent video by the Michelangelo Foundation I decided to pep this videos up and wow, what a transformation. Some dynamic shots, music and editing bring the video to life.
Prototype for a new orrery.
Psst! I am working on a protoype for a new model, something that I can make in small batches. It is early days but I will keep you posted.
Thank you for stopping by.
Apologies in advance for the curt descriptions in this post. It has been a very busy and of course a very strange week. I am lucky in that the threat of Covid-19 has not impeded my work too greatly. Good luck to everyone in dealing with the virus.
I completed the work on the two orrery bases from the previous week. What was interesting about this process is how, due to their shapes, separate techniques were employed to reach the same results.
Skims on both the top and undersides of the bases are taken. The round base was then taken over to the lathe.
The diameter of the base is brought to size and then a grove is turned on the top face, this is to house the brass chapter ring. A profile is then turned on the outside edge. The last job is to sand the surface down to a smooth finish.
Over on the mill the edges of the square base are squared up and brought to size and the profile is added to the edge.
Various fixing holes are drilled and the grove for the chapter ring is chased out.
The square base is then sanded until smooth. Both bases are cleaned with white spirit in preparation for treatment. The square base is treated with Danish Oil, three coats over a 48 hour period. The round base was finished with a Rosewood stain giving a darker complexion to the wood. Once dry both bases are buffed with wax to bringing them to a shine.
I will be finishing these orreries off very soon. Here is a sneak peak.
I thought that some may be interested in our process in the workshop. Here is a brief description on how we make the wooden bases. This weekend I have made a start on two 10" Walnut bases, one is to be round and the other square. They are both for Inner Planet Orreries that I hope to complete by the end of March.
You may have noticed the way we make our bases is in sections rather then turn from one solid slab of timber. This is to prevent the inevitable rough end grain from appearing on two opposing sides of the base. It also gives the grain on top a nice pattern encircling the orrery.
I put this job off last week because the Mitre Saw is set up in the shed and it has been very cold out there. I bravely got to it on Saturday, first chopping six blocks at 30 degree angles for the round base and four pieces at 45 for the square.
These are only rough cuts, it is vital that each block is machined flat and parallel with each face perpendicular to the next. This means using trigonometry to set up parallels on the mill bed.
After all five faces are machined it was time to glue the blocks the together. I applied PVA glue to the edges and held them tightly together in our purpose made vice. The blocks went together very well. The pitfalls of not machining the edges perfectly square are gaps showing at the seams which would have meant starting again. Another issues I could have potentially come across would be not having the edges of the square base all meeting at the same distance which would not look right when the bases edges were eventually bought to size.
One busy orrery makers attempt at giving a peak behind the curtain of an irregular job in somewhat regular intervals.