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2024-05-06

Last modified: 2024-05-14 21:10:08

< 2024-05-05 2024-05-07 >

Machine building

Still todo is:

I thought I had already ordered shorter screws but I still don't seem to have them, need to chase up. It says they were meant to have arrived on Friday, I've messaged GWR Fasteners on eBay.

So let's start with assembling the Z axis.

Oops!

I accidentally drove the ballnut past the end of its screw, 3 of the balls fell out and the seal came off. I will have to reassemble this ballnut.

Well 3 balls came out but I'm having trouble getting any more than 2 back in. There doesn't seem to be room on the outer track for the 3rd ball. It must have come from this track because I can't imagine either of the other tracks got exposed. But maybe? The question is do I assemble it 1 ball short, or do I unscrew it further and see if I can get a ball in the middle track, but risk making it even more than 1 ball short?

I think risk it. I already know I've successfully rebuilt this ballnut once already.

Meh, too fiddly, I can't do it. I'd have to fully disassemble it and I can't be bothered. So I'm just going to assemble it 1 ball short.

That'll do.

Must remember: there is basically 0 tolerance for over-travel on the Z axis.

Next up: assembling the frame?

Looking good!

The uprights splay apart slightly, I think this is due to the inserts on the baseplate sticking out, so if you tighten the lower bolts more it makes the top move out, and if you tighten the upper bolts more it makes the top move in. Not sure whether I'll just live with this or whether I'll file it all flat. It might be helpful if I can use this property to square up the machine and have the gap filled with epoxy putty?

So next up is bolting the gantry to the uprights, which will require hole locations transferred to the uprights and then holes drilling and inserts gluing in.

Then once that is set and all bolted up nicely, I can fit the gantry back pieces. Although I'm not necessarily in a hurry to do that just yet, I can do it just as easily at any time before installing it in the laundry basket. Which, incidentally, I'm not sure how I'm going to do. It is very heavy.

Apart from the above list, things that still need doing are:

Deschanel Treatise on Natural Philosophy

There's an enormous amount of content in this book and I don't have time to read it all, so I'm going to first write down topics from each chapter that sound potentially interesting, and then work through the list.

What worries me is that I'm mostly picking out topics that I think are either new to me, or are likely to be presented in a manner unknown today. But there might be even bigger surprises in the topics that I don't expect to contain any.

Chapter 1: Preliminary notions:

Chapter 2: Mechanics:

Chapter 3: Constitution of bodies:

Chapter 4: Gravity:

Chapter 5: Laws of falling bodies:

Chapter 6: The pendulum:

(Crazy that there's an entire chapter on the pendulum. And it's a long one!)

Chapter 7: The balance:

Chapter 8: Hydrostatics:

Chapter 9: Principle of Archimedes:

Chapter 10: Application of the principle of Archimedes to the determination of specific gravities:

Chapter 11: Vessels in communication. Capillarity:

Chapter 12: The barometer:

Chapter 13: Variations of the barometer:

Chapter 14: Boyle's law:

Chapter 15: Air-pump:

Chapter 16: Upward pressure of the air:

Chapter 17: Pumps for liquids:

Chapter 18: Efflux of liquids:

(The first topic where I don't even recognise the name)

Chapter 19: Thermometry:

Chapter 20: Formulae relating to expansion:

Chapter 21: Expansion of solids:

Chapter 22: Expansion of liquids:

Chapter 23: Expansion of gases:

Chapter 24: Fusion and solidification:

Chapter 25: Evaporation and condensation:

Chapter 26: Ebullition:

(Another one where I don't even recognise the name)

Chapter 27: Measurement of tension and density of vapours:

Chapter 28: Hygrometry:

Chapter 29: Radiant heat:

Chapter 30: Conduction of heat:

Chapter 31: Calorimetry:

Chapter 32: Thermo-dyanmics:

Chapter 33: Steam and other heat engines:

Chapter 34: Terrestrial temperatures:

Chapter 35: Electricity: Introductory phenomena:

Chapter 36: Electrical induction:

Chapter 37: Measurement of electrical forces:

Chapter 38: Electrical machines:

Chapter 39: Various experiments with the electrical machine:

Chapter 39A: Electrical potential, and lines of electric force:

Chapter 40: Electrical condensers:

Chapter 41: Effects produced by the discharge of condensers:

Chapter 41A: Electrometers:

Chapter 42: Atmospheric electricity:

Chapter 43: Magnetism: General statement of facts and laws:

Chapter 44: Experimental details:

Chapter 45: Galvanic battery:

Chapter 46: Galvanometer:

Chapter 47: Ohm's law:

Chapter 48: Electro-dynamics:

Chapter 49: Heating effects of currents:

Chapter 50: Electro-motors - telegraphs:

Chapter 51: Electro-chemistry:

Chapter 52: Induction of currents:

Appendix: On electrical and magnetic units:

Chapter 53: Acoustics: Production and propagation of sound:

Motorbiking

I had my first enjoyable motorcycle ride so far this year. (The first time I got cold and wet, the second time the battery was flat and I had to take the car).

I had the idea to make a "motorcycling forecast", it will basically be a weather forecast but it draws a picture of a motorbike on days that will be pleasant motorcycling weather. I basically just want to be warm and dry. I also want dry roads, so it's no good for it to just not be raining, I'd rather it hadn't substantially rained in the last day.

Today it is apparently 17 deg. C outside and I was quite comfortable, I probably want at least 14? And do I need some sort of model of how long it takes roads to dry under different rain, temperature, and wind conditions?

ChatGPT said:

Let:

P = hours since last significant precipitation
T = temperature in Celsius
H = relative humidity (%)
W = wind speed (km/h)
S = sunlight exposure (hours)

Dryness Score=P+((T-10)/5)+(W/10)+S-(H/10)

And it says a score >15 indicates roads are dry, and <10 indicates roads are still wet.

What does that give us for today?

Let's say:

P = 12
T = 17
W = 15
S = 3
H = 74

Then dryness score is 12 + ((17-10)/5) + (15-10) + 3 - (74/10) = 12 + 1.4 + 5 + 3 - 7.4 = 14. That's actually not awful. The roads were slightly wet under the trees, so being just under 15 is probably fair.

I wonder if this formula is actually any good or if it's just a fluke? Maybe I'd rather display "mm of rain in last 24 hours" as that is then at least understandable.

It would be handy to have a dataset of historical weather readings and road wetness readings so that I could test out the formula, and improve on it.

There is also scope for a slightly different "microlighting forecast", that needs:

Sources of weather data:

Scraping the data from the Met office web page may be the best option. They block LWP::UserAgent's User-Agent string, but changing it solves it. Eventually I'll include a URL to where they can see my tool.

An hour is potentially good for motorcycling if the temperature is 14 deg. C or above, and the sums of percentages of rain probability in the last 6 hours and next 2 hours is less than 80. This would require us to store historical rain probabilities - however I think it is OK to just assume they were 0, because I can look out the window to see if the roads are wet.

I have a script to scrape the date off the Met office page, they make quite good use of data-... attributes which makes it easier than it could have been.

Made a start here: https://github.com/jes/weather - so far just ./grab | ./parse | ./motorcycling and it will print "good" or "bad" based on temperature only. I need to make it look backwards and forwards to see what precipitation looks like, and then do something similar for microlighting, and make it generate a web page and run it on cron. Probably also store all the grabbed HTML so that in future I will have a historical dataset.

Great success:

ChatGPT made the HTML template for me.

https://incoherency.co.uk/motorcycling-forecast/

Lawnmower

I tried the "Drop and Mow" on the top grass out the front, with this result:

The problem is that the stone has some grass/weeds on it so the camera still thought it was driving on grass all the way off the edge.

Solution:

< 2024-05-05 2024-05-07 >