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I've half made my first clock :-)
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hugozair



Joined: 21 Apr 2015
Posts: 134
Location: near Penzance UK

PostPosted: Fri Jul 24, 2015 6:14 pm    Post subject:  Reply with quote

Well at least I should be able to post a picture next time ! Thanks for the explanation zero I've been away on holiday so have only one thing to report. On returning home I ordered a 1 metre length of 8mm dia. Invar and it arrived to day. I had to settle for 1 metre rather than 1030mm which is what I really wanted on account of the cost. 1 metre was 70 but to get a little more I would have had to buy 1500mm at 50% extra cost.
The whole business of the temp control in the case has not turned out to be very practical - or accurate.
I will use a slightly longer rating screw and hope that the upward expansion of the brass shelled bob will be cancelled out by the longer mild steel rating screw..I'm an optimist !!
Incidentally the invar rod I got is rather grey rather than shiny like the Invar in the commercial clocks I have.
I also have a string of family visits over the next few weeks so it may be a while before I can fit it. I'm keeping my fingers crossed about drilling and tapping the rod..Roger
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hugozair



Joined: 21 Apr 2015
Posts: 134
Location: near Penzance UK

PostPosted: Tue Nov 03, 2015 7:59 pm    Post subject: an update Reply with quote

It's been too quiet around here so I thought I might try and break the spell !
At 22.00 on the 2nd October By judicious fiddling with the pendulums of my Synchronome clock and the homemade cHip Toggle clock, I "zeroed" the clocks to a radio controlled wall clock.
Now, one month later, I can report the results. Now, at 22.00 last night (2nd Nov) my clock was !.5 sec early and the Synchronome was 1 sec early.
The lowest pressure seen during that time was 990 and the highest 1031. In general the pressure tended to be toward the higher. The two clocks didn't vary their rate in unison.
The greatest error seen was with the Synchronome on the 11th Oct with 2.75 sec early (while the DIY clock was 1 sec early). Throughout the 28th and 29th Oct the DIY clock was spot on while the Synchronome was 1 second early. Throughout the month the temp in the case was always close to 20 C
Just a snapshot of a months running with no fiddling.
Hope there are still folk checking in !...Roger
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Zero



Joined: 21 Apr 2015
Posts: 102

PostPosted: Wed Nov 04, 2015 5:12 pm    Post subject: Reply with quote

Thanks for the update, Roger.
You seem to be maintaining a very stable rate on both clocks.
With the Hipp holding a better rate, it seems.

Can you clarify whether you finished the Invar pendulum?
Any particular problems with working this "notorious" material?

How are you maintaining the case temperature at 20C after your mention of some difficulties in your last post?

It has been very quiet on all three 'electric' forums.
This one seems to be fielding most of the clock making interest.
An area poorly served on the other two forums. [From memory.]
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hugozair



Joined: 21 Apr 2015
Posts: 134
Location: near Penzance UK

PostPosted: Wed Nov 04, 2015 10:11 pm    Post subject: Reply with quote

Hi Chris..yes I.m pretty leased with the months running but I wouldn't claim that either clock is better than the other. The month in question was October which has been very mild and the whole house temperature hasn't changed much from 20 degrees throughout. Although I measured the temp inside the case of the c|Hipp clock it must have been pretty much the same as RT.

Back in the summer I did try temp control inside the case because on sunny days the room and case temp often went up to 24 degrees so I had to set the case heater thermostat to that temp.The results were not as good as the recent ones for some reason and it was abandoned.

One conclusion I.ve come to is that it may take a very long time to truly rate a clock that doesn't have the benefit of a sealed pressure tank !

The invar rod I bought was just one metre so I had to add 30mm of silver steel before connecting to the rating thread. I have a lathe and made the joints to the rod by careful drilling and taping for short 6mm studs at each end. Although it was tough going and needed much lubrication it went ok.

I found that monitoring barometric pressure to be confusing because it can take a while before a + or - timing error is seen..By then the pressure has likely changed again ! The lesson I have learned is not to be too hasty in adjusting the weights on the pendulum after getting it quite close.

The coming month will probably be colder and the house temp more changeable so it will be interesting to see if the October results can be maintained..I'll report again in due course....Roger
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Zero



Joined: 21 Apr 2015
Posts: 102

PostPosted: Thu Nov 05, 2015 6:10 am    Post subject: Reply with quote

Thanks, Roger.

It sounds as if you need an unheated cellar for a more stable temperature regime.
Though I imagine it would not be so much fun as to be able to see your clocks more regularly.
Atmospheric pressure variations are probably a larger cause of rate errors.

Is there any history of water "cooling" precision clocks?
A tall aquarium with a glass cylinder submerged within it for the clock?
This might be quite a talking point for the living room. [Fish optional?]
Perhaps it would be more trouble than it was worth in maintaining temperature stability?

Forget the water: Stick with sealed air:
Building a tall clock tank from thick window glass should be quite possible for an expert "glazier".  3/8", 1/2" and 3/4" are readily available.
Polished edges and modern adhesives would ensure it was "pretty" enough for domestic display.
The small dimensions of the glass should provide adequate strength to cope with atmospheric variation.

Thick poly-carbonate plastic could be solvent welded into a strong clock tank.
Attachment points for the clock and tank/wall interface should be made adequate for avoiding flexure.
Then all you need worry about is sealing the necessary wires.
Though a battery could be housed within the tank to avoid even that problem.
It all sounds quite easy, doesn't it?  Very Happy
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hugozair



Joined: 21 Apr 2015
Posts: 134
Location: near Penzance UK

PostPosted: Thu Jul 07, 2016 7:54 am    Post subject: H-bridges Reply with quote

I've got my diy clock running an alternate polarity dial, stepping every second. That's done away with the need for a divide by 30 section which was a temporary bodge anyway. Reason for this post is to extol the virtues of the ready made H-bridge modules which make running an alternate polarity dial a real snip. There are at least 4 different ones on eBay and they are so cheap.
I've only recently come across these things so apologies to all who already know about them. I've updated my cHipp Toggle blog and at present it's the last entry. Shows a simple dial mech drive circuit using one of them..
Roger

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