pigeon timer

Way back in 2008 the conversion of a Toulet Imperator pigeon race timer into a conventional clock was described in ME.The time has come to actually do it, another one off the bucket list!

The motion work is arranged to give a 24 hour clock, so the ME article advocated dumping it and substituting a daisy wheel mechanism. Just to be different I want to modify the motion work. It's time to find out about gear cutting.

The existing set up is 26:52 and 6:72. If I replace the 26:52 with 39:39 I get the desired result. As near as I can measure the centre distance is 21.26mm. Not easy to measure, so might be a bit off. The gears appear to be cycloidal

If I use divide 21.26 by 39 I get a module of 0.545mm which doesn't sound right, but if I try 40 dp I get a centre distance of 24.76, which is equally unlikely. Can anyone point me in the right direction?

Clock wheel and pinion cutters are made in increments of 0.05 module so 0.55 is what you are looking for. You can buy them on line from Meadows and Passemore.

Russell

Thanks Russell, I've been on M&D website, at nearly £90 I think I'll revise my plan and go for the daisy wheel, or I might have a play with magnetic gears

Yes they are expensive for a one off job. You could try making one yourself. As you are not meshing with an existing wheel you could use involute gears I seem to remember John Stevenson published a method for making cutters some time ago.

Meking cycloidal cutters is described here at length: making-clock-wheel-pinion-cutters

Russell

Update:

A forum member very kindly offered to make a pair of 0.8 mod 26t gears but slightly oversize to suit the centres I'd measured. I reckoned I'd better have another go a measuring the centres, so I've made 2 blanks exactly 21mm diameter, the idea being to then use a feeler gauge to get the exact distance. Guess what, I can only get a 0.05mm feeler between, so I would say 21mm will do. This opens up commercial gears, 42t 0.5 mod, 28t 0.75 mod or 21t 1 mod. Not stunningly expensive, or I can get a set of cutters 0.5 mod including arbor for just over £100.

The wooden base is only temporary, honest. What the existing gears are is anyone's guess.

Progress:

I chickened out and bought a pair of 28t 0.75 module gears. They fit very nicely. However, not all straight forward. The minute shaft (is that what you call it?) turned out to be tapered. If I'd read all the original article I'd have known that, but I didn't. The author suggested using a tapered broach, or boring out the sleeve which fits over to suit. well I haven't got a tapered broach, and are they all the same taper anyway? Boring a hole 4mm diameter by 20mm deep to some unknown taper is for the supermen, not me, so I set up in the 4 jaw on my little lathe and skimmed it parallel. I suppose I could have made a tapered D bit. Then I found that the hour pipe is also bored tapered. That was a lot easier to sort out, set up in 4 jaw again and bore it parallel. The original second gear in the train (the bigger one on the layshaft) I sawed through the spokes, set it up and turned the stubs concentric with the pivots, then bored the new gear to slip over. Currently held together with double sided sticky tape to test it out, I'll go and buy some JB weld shortly. It now all goes round rather sweetly, just a trace of backlash full rotation. Need to find a light spring for the friction drive. The gears came from HPC, Reliance now have a £250 minimum order charge

Final big gear omitted so you can see the first pair

I've since made the chapter ring, only the hands to go now

Edited By duncan webster on 06/05/2021 18:18:05

More progress:

Now need to find a nice piece of mahogany or similar for the base and buy a glass dome. The printed dial would be better on card rather than paper, it wrinkled with the glue.

The hour pipe is free on the minute pipe(?) until I put oil on it, then it gets a bit sticky. I might need to relieve the bearing surface so it isn't as long, just fit at the ends, but let's see how it goes. I've had it running for days with just the new pair of gears, so that isn't a problem