Member postings for Clive Steer

I think noisy might be averaged out in a linear system, but because of circular error, there is a degree of non-linearity so would noise get "rectified" and produce a timing offset.

CS

That is certainly an impressive clock. However I'm surprised he's operating it at such a hard vacuum although this may have only been during degassing. Water vapour and other organic materials are a major issue hence the need to bake.

To get really hard vacuum you would need several pumping devices starting with a dry claw pump, backing a turbo pump with a cold trap using liquid nitrogen and an ion pump to get rid of the last few molecules. I don't know what the vacuum requirements are for the latest 3nm semi-conductors but I'm sure they will be expensive.

Many plastics are a no no in high vacuum because of outgassing and that includes PVC covered wiring.

You may be able to buy stock Pyrex tube from a scientific glassware manufacturer. There is one near me in Hastings that I visited where they had a lathe for making large bell jars and other vessels. An impressive manufacturing process to see.

CS

It isn't clear to me whether the Fedchenko suspension arrangement provides the desired cube law restoring force or made the pendulum bob track a cycloidal path.

Frodshams have lent me the "Harrison Decoded" and the "Woodward on Time" books to bring me up to speed on Pendulums.

One point made in the Harrison Decoded book is the importance of "The Hill test" . It seems the cycloidal cheeks are profiled to not only reduce circular error but to overcompensate for this at the proposed working pendulum amplitude. Beyond this amplitude the timing increases and below this amplitude follows a reduced circular error profile. I still need to understand precisely how this is used to balance the effects of buoyancy and aerodynamic drag.

CS

Although Fedchenko described his suspension there were no construction information or dimensions so replicating it would require a degree of experimentation . However he explains in his article a couple of other methods that, although not as effective as his design, could reduce the effects of circular error. The two that are relatively easy to construct area the cycloidal cheeks acting on the suspension spring and an extension coil spring acting on the pendulum rod to provide extra restoring force proportional to pendulum amplitude.

Cycloidal cheeks may only be effective for larger amplitudes as dimensional accuracy and suspension spring compliance may make things difficult. I think it may be possible to simplify the cheeks by using pins and if adjustable could be tweaked to get thee required result.

The spring method was used, very successfully on Bulle electric clocks to stabilise pendulum amplitude with variations in battery voltage and used a simple single rate extension coil spring. However the use of multi-rate spring may give better results.

Testing for an isochronous pendulum is quite simple in that one pulls the pendulum to one side and let it go and then log the timing as the amplitude decays.

CS

Hi Stueeee

Check your inbox as I might be able to help

CS

The final drive to the escape wheel was through a large wheel onto a trundle type pinion made up of two crossed out discs with 1mm trundle pins. On these were mounted 1mm bore x 3 mm OD ball races to act as a Harrison style anti friction wheel. There were gaps either side of the ball race and the discs which wasn't a problem providing the wheel ran true. However due to wear, handling or accident the wheel didn't run true and a engaging tooth would slip sideways off the race into the gap and jam. My solution was simply to use two races per pin to fill the gap between the discs. Swiss cheese effect in a bent tooth finding a race not exactly in the centre of a hunting tooth configuration.

CS

Michael

I did indeed go to the Frodsham workshop and spoke to the guys there. What I found out was that Burgess B completion was a team effort which also included inputs from Jonathan Betts and Martin Burgess himself. Unfortunately, David, the guy who did much of the work is away at the moment taking care of his elderly parents but I do hope to speak to him soon. After Burgess B was completed David made a minimalist "clock" with a fused quartz pendulum rod, grasshopper escapement and mechanical remontoire driving the escape wheel. This was built to explore the accuracy of a pendulum operating at a high amplitude. After initial testing of the clock using a weight driven arrangement to power the remontoire they decided to use an electrically wound remontoire to power the mechanical remontoire ie have two cascaded remontoires. I designed the electronics to control the electrical winding.

On installing the new winding system the clock would occasionally stop and naturally they blamed the "new" electronics. I retested its function but could find no reason for it being the cause of a stoppage. In the end I just needed to look in the right place more carefully and found the issue was caused by the mechanical remontoire jamming.

Sadly the project is on hold at the moment but the intention is to fully instrument it to measure environmental conditions, pendulum timing with optical sensors and a laser range finder for monitoring pendulum amplitude.

I'll post more info when I have it.

CS

I thought that this thread was started in order to discuss the techniques needed to achieve a precision pendulum.

Unfortunately, like many of the threads, this one has moved on to discussing where one might obtain a 7/32 milling cutter.

I think the reason the impulse pallet needs to be the shape is and how this shape contributes to pendulum precision would be more informative.

CS

As I understand it only the length of a pendulum rod and the restoring force exerted by gravity determine the frequency of oscillation of a pendulum.

Variations in rod length due to temperature can be reduced by using a rod of Invar, fused quartz or other slow thermal expansion materials. Variations in the restoring force acting on the bob mass caused by air pressure/density may be offset by a barometric compensator or operating the pendulum in a controlled atmosphere.

Both of these are both simple and effective to implement.

However for a simple pendulum the issue of circular error and the need to stabilise amplitude is a difficult issue to solve if the history of clock development so far and the discussions here are anything to go by. Numerous escapements, drive train improvements and increasing levels of pendulum detachment have been devised to help produce a stable amplitude.

Fedchenko side stepped the problem by using a suspension design that eliminated or at least substantially reduced circular error and therefore reduced the need to stabilise amplitude.

There have been several methods devised to reduce the effects of circular error such as the spring used on the Bulle electric clock that compensated for the reduction of battery voltage over time and reduced impulse energy.

Although this method doesn't reduce circular error to the extent the Fedchenko's design does it will go some way to reduce the need for highly accurate impulsing. Also on an electrically impulsed pendulum one can easily change the impulse energy to see if such a method makes the pendulum more isochronous.

CS

I think someone said "believe only half of what you see and none of what you read". It is a shame that we have to be so wary of everyone.

It reminds me of "adverts" that appeared on TV back in the 50's warning people about shady market dealers selling "real" bargains using auction like sales pitch . There were "stooges" eagerly "buying" the "bargains" to get unknowing punters to also buy what turned out to be box of rubbish when they thought they were buying a canteen of cutlery.

Nothing changes except the method of "The Sting".

CS

I bought a similar Boxford's some years ago and by myself took it apart and brought it home in the back of a VW Polo. So they are quite manageable when dismantled with the bed being the heaviest bit and the base cabinet being the most awkward to shift. Since your machine isn't an under drive type the job of getting the motor and countershaft system separated is not so daunting. I think it took me about an hour to take apart and get it into the car. However I was much younger then.

CS

John

Thanks for the link to your articles which I've just glanced at now but will read in depth later.

I'm going to the Frodsham workshop tomorrow and will see what info I can "extract" from the guys there that worked on finishing the Burgess Clock B. Of course they also made a replica of Harrisons H3 and finished Derek Pratt's H4.

CS

To make accurate thin spacers I use a bar turned to the correct OD and bored to the correct ID. I face off the front face and then part off a spacer thick enough so that the front face remains reasonably flat.

I then use superglue to stick the front face of the spacer to the lathe's face plate and then slowly face off the spacer to the thickness needed. I have a DRO so can zero the DRO with the cutting tool against the face plate surface so it effectively reads the spacer thickness. Thinning down does have to be done slowly so the spacer doesn't detach from the face plate.

A rather tedious process but if you only need to make a couple of spacers it works well enough. I release the spacer with acetone.

CS

Hi Dickie

Welcome to the forum and the mass of knowledge and experience it provides access to.

I think the Museum at Amberley, which is close to you, may do a course in blacksmithing. My son did a days introduction course there where he made a fire poker.

CS

Nicholas

Your watch dial doesn't use radium but uses the "milder" Tritium based luminescence indicated by the "T" either side of the Swiss Made legend.

CS

Robert

I'm sure there are numerous "Spitfire" and "Lancaster" aircraft instruments and particularly clocks sitting on collectors shelves. I'm not sure what level of radiation they emit and whether this would be harmful. One problem is knowing if an instrument/clock has radium or the later phosphorescent paint. Old radium watches may no longer emit light , not because the Radium is inactive but because the material used to convert the radium's radiation into light has been bombarded to death and usually goes black or dark brown.

CS

One can never be too careful with any radiation source. I found a Cyma WW2 military watch in a deceased watchmakers effects. This watch had Radium luminance and had been stopped for many years. What surprise me were the radiation "burns" clearly visible in the acrylic crystal where the hands had been "parked" for several years.

There has been various articles in horological magazines about the removal of radium from watches but no definitive procedure and particularly where it can bee safely disposed of.

Some horologists, believing the radium to be a "mild" source, have disposed of it in household waste assuming it would be quite safe in land fill. However doing this when increasing amounts of waste is going for incineration is very questionable if not illegal.

CS

The laws of Darwinian natural selection are still at work. However with regard to Homo Erectus the selection process has become less natural and more mechanised. What countries population would not be asking their leaders and military to do something when there's no food on the table or fuel in their tanks. With the rate of the world population growth at present we already have "Trouble right here in River City". We could handle the situation well but if history tells us anything the human race invariably handles it badly. A rather pessimistic view but none that have not already been portrayed in many Sci-fi films. If the views expressed on social media are a reflection of our society we are in for a bumpy ride.

CS

I don't think you can ignore the laws of physics in that the amount of energy in fuels being used daily within the UK by vehicles is enormous. If this is to be replaced by electricity our generation and distribution infrastructure will have have to be upgraded beyond all recognition. Hydrogen and fuel cells may play a part in closing the gap in range that some vehicle users may need and its distribution could similar to what we become accustomed to. For shorter of less frequent journeys current battery vehicles may be more appropriate. However there will never one model that fits all so predicting the future will be like predicting if VHS or Betamax would become the standard and many of use know how that turned out.

Going electric is one step towards improving the efficiency of transportation but trams and railways have had a 100 year head start so there's a lot of catching up to do.

One thing I think is needed, and modern GPS/phone tracking may help with is just what the average and deviation from average is for vehicle journeys. It may make interesting reading.

CS

Iain

RS components sell a number of measuring graticules for use on their magnifiers. The magnifiers are rather expensive but a cheaper option is to fit them to a standard watchmakers loupe or under a microscope.

CS