No other choice than...
  • Hi everybody, I'm an astro-amateur... converted to clock making in "cloudytime". So, what other clock I could make?
    The H-1 inspired clock is perfect for celebrating the genius of Harrison with my first clock, and saying sorry for all the problems that the astronomers gave to him :-)
    At the same time, I'm reading "Longitude" by Dava Sobel, these are an excellent way to spend spare time I think, and I'm enjoing very much!
    My Sextus is still a baby, because I veneered the frame with carbon fiber, and I had to refigure the pieces and reopen all the holes. After two days of grinding, the bearings are on
    http://postimg.org/image/5skngqher/
    All the best
  • Like the carbon frame. I was thinking of having a go at carbon fibre gear wheels, then I saw the price of carbon fibre sheet!

    Yours looks good.

    Chris.
  • The quantity of carbon fiber I used is very low and didn't cost me much.
    I'd even like a carbon fiber escapment wheel but I can't veneer it as I had, I'd have to veneer a new plywood sheet and than cutting on CNC. At the moment I don't know exactly what could happen... carbon fiber isn't easy to cut rightly, and need special tools: normal cutting tools usually rip and ruin the fibers, while tools for carbon fiber (typically abrasive with industrial diamonds), don't cut wood...
    Even laser cutting isn't good because carbon fiber is a great electricity conductor and resin triggers burning!
    So... grindgrindgrind :-)
  • Agree with Chris: nice looking frame Lorenzo!

    I have almost completed the frame (from the kit, I don't have CNC nor I can sadly), and now its the prime/dye step. A pity that don't have a lot of free time, I would like to start it and finish it in a couple of sessions...

    Regards
  • Antaviana, I can understand you! I was very buzy when the kit arrived, but after beginning, I finished it in 10 days, loosing hours of sleeping! (crazy....)
    And I had many many extra-work than an usual sextus, as you can see here
    http://postimg.org/image/jy1hlgxi7/
    I admit that, close to the end, I was so agog of listening ticks that I had some problems.... so enjoy the making, but as Dave says, take your time.
  • Great looking Sextus Lorenzo!!

    How is the ticking finally? Sounds nice? I'm also thinking on the day I'll be able to hang it on the wall, but going step by step, I'm enjoying every single details of the building. And using only manual tools, even a manual driller for the wood holes. Sadly there is only a hole I will not be able to do it by hand, the one on the drive arbour. Perhaps may I use other kind of key to wind it, like square the end of the arbour and use a grandpa wall clock key. Of course, I'll have to extend the arbour to keep away of the dial, but I don't know if would be as comfortable as the nice Sextus key...

    Anyway, congrats for your great clock!
  • You can square the end of the arbour but you can't use a wood key because the square hole is so small that it would quickly become rounded. Before cutting the length of the arbour, I'd try to drill the hole: clamp the rod and mark the point with a burin and a hammer, than drill carefully. The hole won't be perfect, and probably larger than need. I simply glued the metals arbours...
    The Sextus ticks very well, sounds... a bit too much, (need felt), very accurate, less than 1 minute in 24h. I had problems with the left hook, I added a washer M4 as a counterweight and now it goes back better, it becomes noisy but the clock never stops till now.
    Final version http://postimg.org/image/q4ubanp9d/full/
  • II'll try to do the hole the way you said, I think it's the easiest way without the correct equipment.

    And your Sextus with its final weight looks really good! Oh, and I would love to be able to keep mine to a minute per day of precision, well done!
  • thank you, but I've to say the true: as I wrote "never stops till now"..... it stops! :-)
    Restart and after an hour, stop again... panic. The temperature increased 10°C in a day, and after two days of glory, big frustration. In this days I checked all the teeth of the wheels, every possible frictions, geometry of pallets, grinding some detail... but nothing! How is it possible?
    At the end, the last three screws... the frame. Well, the screws of the frame were loose! Two loops each, and when the weight was far from the wall, the frame deflects and the arbor clamps in the bearing. Now I'm confindent that I can hang it on the wall :-)
  • One thing to always watch out for when your clock stops after running fine for a few days is frame sag.
    As the drive weight pulls downwards on the frame it will sag, if the sag is too great it will pinch the arbors, this is especially the case if they are resting in ball bearings, as the tolerances are a lot smaller than with a hole in the frame.
    As the Sextus has approx. 2.9kg drive weight the downward pull has to be held by the frame, which is why I used through bolts and also big Dia. spacers that sit well in the frame. But as your experience has shown, if you do not tighten the bolts then it is just a question of time before your frame sags.

    Dave
  • I had another "strange" experience, after making up for the poor reassemblage of the frame: as the point of contact of the weight string moves forward on the barrel, timing become faster, than, close to the front frame, (and weight near the floor), the clock slows down again.
    Probably the bearings deflect under the weight, or they move a bit in the holes.
    I restrained the width of the rolled string (about 20-25mm) with two plywood rings , keeping the weight in the middle of the arbor as much as possible. After that I immediately had an improvement of timing, from -4min/day to -1minute in 2 days! I'm absolutely satisfied (even if it'd definitively become +-3min/day :-) )
  • I found that if I use the handle to wind the clock the frame moves and changes the timing each time I wound it. If i wind the string drum with my finger and thumb and use my other hand to hold the weight so the string winds to the back, the timing stays constant.
  • As I described on page 47 of the Sextus instructions, it can happen that the clock slows when the drive weight sits towards the front, but this is very much curable, one thing to watch out for is get those through bolts well tightened, loose bolts will cause more frame movement, and of course compensate for frame sag by making sure the arbors are thin enough to prevent clamping.

    @Ian Dunbar

    There will always be frame movement when you wind the Sextus, but it surprises me that it should have an affect on the timing. As mentioned above make sure the bolts are nice and tight. Another way to get your clock more stable is to glue the dowels into the back frame, but should not really be necessary.
  • I confirm Ian experience. Now I lift the weight with the hand and wind the string with a minimum of tension. My arbors are at least 4 centesimal thinner than holes and seem free.
    Right, I could glue the dowels to limitate the frame sag.... but, really, don't worry Dave, we can cohabitate peacefully
  • Hello Dave

    I wasn't complaining, i was just passing on my experience : ) I am very happy with the clock.