Friday, December 9, 2011

Nixie Tube Clock


For Sale  $250!!!
Here is the last of my Nixie Tube clocks for sale.
This is $70 cheaper than all of the others I have sold, but this is not numbered, dated and/or personalised.
Very accurate, totally cool and mows laws. What more could you want!
Email me if you would like it!   r.batten@optusnet.com.au




This clock is quite safe with the open circuitry, but is not suitable for a position/home where children can get to it.

Tuesday, December 6, 2011

Breakthrough after breakthrough!

Its been a week of break-throughs, I am pleased to announce.
1. A winner gear tooth profile.
2. Double safety measures for the recently made, yet to be named electric clock.

The first being a new gear tooth profile, has got me grinning from ear to ear. I have spent around 3 years now trying to come up with a tooth profile that works Super efficiently. Basically put, its really easy to make a gear tooth profile that works, and they will work in varying degrees of efficiency of energy transfer from the gear tooth to the mating pinion tooth (smaller of the 2 gears).

 The place where the efficiency is most needed is earlier in the drive chain where there are large amounts of pressure on the teeth. And especially where the next 2 teeth start to engage. What tends to happen with a badly designed tooth profile, is that the newly engaging tooth tends to 'crash' into the face of its mating tooth. This causes a drastic decrease in drive pressure and much more often than not, this is when/where your clock will stop because there is not enough torque to turn the escapement wheel. The trick is to get the 2 new mating teeth to smoothly slide together, like on a tangent. This I have managed to do fairly well in the past with certain gear ratios, but I have found that once the ratio changes the gears don't tend to mesh as well.

This occured to me recently on the Gravity Escapement clock (the one that is a bit like a 4 leaf clover) Gear ratio 64-8 meshed beautifully, but I had to change it to 64-16 to get the drive weight down, and it didn't like it at all. Also some escapements accuracy is dependant on the drive pressure being constant...and a drive pressure that fluctuates up and down as teeth engage is not good. I have 2 of the same clocks sporting different teeth profiles and the different accuracy between the clocks is VERY evident.

So after around 5-6 different gear tooth profile designs and studying many others over a period of around 3 years, I am pretty sure I have cracked it! ...No actually I know that I have cracked it!! Sorry, but I am going to have to keep it a secret on how to reproduce it. :) Whats more, I think that they are quite pretty looking to!


BREAK-THROUGH #2
Not being an electrical engineer by any account, I have been quite worried about running the clock with no supervision. I have once gone upstairs at home for 15 minutes, only to find on my return that the clock had stopped, because the mercury switch got stuck inverted. This has left the coil of the solonoid energised and upon investigation, it was found that the coil had heated up to 67 degrees celcuis! Actually not at all dangerous at that temp, but it can burn skin! The wire will melt at over 300 degrees C and the enamel will burn somewhere between 130 and 300... The coil will most likely reach equilibrium way below that temp (that means energy coming in equals energy going out, or heat from the power to the coil is equal to the heat radiating to the air). BUT I am not keen to try it.

I have tried many types of fuse values and makes, but have not found a solution. Upon talking with a family friend (Tony Roe), who IS an electrical engineer, I found 2 other types of components that I am sure will have it sorted out. Only time will tell, as they are now added into the circuit. The first is a resettable temperature switch. This is mounted on the back of the coil itself, and cuts the circuit if the coil measures a temp in excess of 60 degrees and reconnects the circuit at 45 degrees. The other component I have put into the circuit is a PTC or a "polymeric positive temperature coefficient ". Put simply, its a fuse that when current is drawn through it above its rating, the polymer inside it melts and stops conducting electricity. The current of the coil draws 250 mA for periods of about .7 of a second. The PTC internals melt when a current of over 100mA flows for around 7 seconds...and stay melted untill the current is turned off. Which is actually better than the temp sensor, because the temp sensor will oscillate between on and off as the circuit turns on and off!

So its been agreat week of breakthroughs.
See ya round like a rissole!