horology Archives - Page 4 of 6

March 26, 2019June 30, 2020

Clock Wheel Cutting Adaptation of a Tormach Saw Mandrel

I am slowly building up to being able to cut wheels on the Tormach PCNC440 with two possible methods.

The first is using Gearwheel Designer which is mentioned elsewhere on my blog.

The second route is more conventional using a PP Thornton or similar cycloidal tooth cutter and a dividing device on a rotary table. This later method is how wheels are traditionally cut in a lathe and there is a lot of information available on this.

In order to use the cycloidal cutters I need some form of arbor to mount the cutter in the Tormach spindle. I could simply turn a piece of steel bar to suit and mount this in a ER collet in the spindle. The downside of this simple approach is that every time the arbor was fitted into a collet the cutter would be at a different height from the table. I really wanted something a bit more repeatable as the centre line of the rotary table will always be the same so why not the cutter centering.

When I ordered the Tormach PCNC440 I also ordered the Tormach small rotary saw arbor (which to date I have never used). Pondering this last night I sketched up an adapter in Fusion 360 to allow an involute cutter to be fastened to the end of the saw arbor.

This is shown below. It is made from a piece of 19mm AF hexagonal steel bar with the hexagonal flats going to be used as a tightening it in place in the Tormach arbor. My Myford Super 7 when used with a 3 jaw self centering chuck is not bad on concentricity but for really accurate centering I swap the chuck for a collet face plate instead. This job was going to need both.

First operation was to turn the hex bar end that would screw into the arbor. This was done in the lathe chuck. It was a simple turn to a diameter and drill and tap the end with M6 to match the arbor mounting. The only pain was the arbor has a slightly protruding lip so I had to undercut the mounting face for this. Rather than trying to be clever I did it by hand using a graver.

While the hex stock was still in the lathe I roughly turned down the other end of the adapter to the primary diameter and slightly oversize for the cycloidal cutter bore diameter and then cut off the stock so far.

It would be important to get the cutter mounting running as square as possible so I swapped the lathe chuck for the collet plate and mounted the arbor end of the adapter in the collet. I carefully turned the shoulder for the cycloidal cutter diameter and then reduced the remaining length ready to cut a M6 thread.

Here are a couple of images of the finished adapter.

Tormach TTS saw collet with my adapter and a typical clock wheel cutter

I am pleased to say the idea went almost to plan and it runs very true in the Tormach spindle.

I was a bit over enthusiastic with the graver but this is of no consequence.

With hindsight the shank between the cutter and the hex section ought to be longer as this will restrict the diameter of the wheel that can be cut before the blank catches the hex section peaks.

One step closer to trying this method. The next experiment is to work on a sub routine in GCode to move the cutter back and forth while cutting and with the ability to easily program the number of cuts.

Similar or related subjects : –

March 2, 2019March 4, 2021

Microset Clock Timing Instrument Upgrade

Mumford Microset Clock and Watch Timer

Some while ago I bought a Microset Timer from Bryan Mumford. This is a lovely device that allows you to monitor all manner of parameters on clocks and watches. It has an acoustic sensor to listen to the beat of the clock or watch and an optical sensor that creates and detects a beam of light that is chopped by the pendulum. From these simple accessories all manner of diagnostics can be done on the clock under inspection. If you want to know more I suggest you log into Bryan’s site. Bryan also has some videos which you can find on YouTube. You might also want to download and read a pdf collection of articles written by Chris McKay in the Horological Journal about using the Microset to fault find on Turret Clocks.

Microset Timer from Mumford Micro Systems

The Local Church Clock

If you are a regular reader of this blog you will know that I have got involved with the local church clock which is a Cooke of York movement. I have been working with a fellow engineer in the village to try to bring the clock to time and we are slowly getting there. Our last major breakthrough was finding the fly was lose on the gravity escapement arbor. Since tightening the fly the clock has been much more reliable.

There is a weight tray on the pendulum which has an assortment of coins in it where someone historically has been fine tuning the pendulum swing. Because the clock has been running fast by a few seconds per day we have been slowly removing the coins one by one to bring it closer to time. I think it is now at a point where we need to monitor it long term with the Microset.

Microset Upgrades

Bryan offers an upgrade to the Microset that allows a temperature sensor to be added to the recorded information. There will almost certainly be temperature changes in the clock tower so it seemed like a good idea to upgrade with the temperature option. This was ordered and duly arrived from Bryan and is now fitted. There is also an upgrade to allow the Microset to record data into internal storage in the Microset rather than depending on having a PC connected. I would be more comfortable leaving just the Microset in the church pendulum cupboard rather than my portable PC so I also ordered this upgrade.

It took me about an hour to do both upgrades on the Microset. The memory upgrade involves a chip change inside the device and the temperature monitor needs an additional 3.5mm jack socket fitting and wiring to accept the new temperature sensor. Neither is a difficult task but clearly need to be done carefully so as not to do any damage to the Microset. Bryan’s instructions are well written and illustrated.

Since the upgrade I have been running the Microset on the bench with a Smith’s clock movement. (It is actually the one I stripped down, cleaned and rebuilt on my ‘Clocks 1’ course at the BHI). The new Microset facilities seem to work well and as expected.

Microset optical sensor monitoring a Smith’s clock mechanism

A New Sensor Needed – 1st Attempt

To implement measurements on the church clock the supplied optical sensor as shown in the picture above is not totally ideal. It has a very narrow gap between the transmit light source and the receiver detector diode which on a turret clock is not easy to use.

It is possible to get round this my fitting a cocktail stick or similar to the pendulum bob and using this to break the beam but it is a bit messy. I had picked up a bag of laser diodes and detectors at a local ‘ham’ radio junk sale and I decided these might form the basis of a new sensor which might be more useful to a large pendulum assembly. Bryan is a really helpful guy and although he does offer a larger laser sensor he was more than happy to help me with the required electronic interface to the Microset. The one proviso is that the amount of current drained from the Microset 5V power supply must be kept below 30mA.

I set to and made the most elegant and over engineered solution for my laser sensor. This is shown below. The black mountings were designed in Fusion 360 and 3D printed on the Sindoh 3DWOX.

First ‘elegant’ laser detector for Microset timing instrument

The spacing between the emitter and detector is adjustable by sliding the transmitter along the steel rods. The power to the laser is also carried down the steel rods. A small DTC transistor provides the interface to the Microset and the 5V supply provided by the Microset is dropped via two diodes to power the laser. It works really well ….. but … when I went round to the church to install it I realised I should have checked one or two things first. The rating nut at the bottom end of the pendulum (used to make course adjustments to the pendulum length) was almost touching the floor of the pendulum cupboard. My wonderfully elegant laser detector would not fit under the pendulum to monitor the swing. A serious re-think was needed. The gap was so narrow that at best I will only be able to get a piece of 16 SWG aluminium sheet or PCB underneath the rating nut.

A New Sensor Needed – 2nd Attempt

I did say I had a bag of laser diodes and detectors so a new version would be possible and I could then save the posh one for more public facing activity.

As mentioned above I decided to use PCB as the base board. This is shown below.

Mk11 Laser Detector Specific to local church clock with little clearance from rating nut to floor

This has the advantage that I can use the copper surface to mill tracking into it to aid the wiring. The downside is that it is quite flexible and therefore possibly not stable enough to keep the laser aligned with the detector diode. To resolve this I soldered strips of nickel silver (could have been more PCB) either side of the centre line as shown but leaving a gap for the pendulum swing.

I designed a common holder for the laser and detector diode in Fusion 360 and 3D printed two of these on the Sindoh 3DWOX.

The finished detector assembly still had a tendency to flex so I stuck some old pieces of credit card on the lower surface, one at each end before the mount and a large piece in the middle. This seemed to cure the problem without adding significantly to the base thickness.

Microset Display

When plugged into the Microset all seemed to work well. Here is a typical PC display of the Microset data.

Microset Data Display showing the data from a Smiths clock mechanism and also the green line showing the temperature

I now need to get it installed in the church tower.

Similar or related subjects : –

January 10, 2019January 10, 2019

It’s Horology but not as we know it Jim

If you visit any car boot sale / brocante /yard sale you will almost certainly come across old mechanical clocks that probably have a wonderful history if they could only speak. Their previously loving owners have ‘passed on’ and the inheriting family probably don’t like the looks of the timepiece or just can’t be bothered to wind it up or it simply no longer works which is a big problem with a rapidly diminishing fraternity that know how to fix them.

Now what follows is going to disturb the purists so they should look away.

When I find a specimen that has some character or aspect that appeals to me and has no historic value I will offer the few coins being asked and give the clock a new life. Not by repairing them in the true sense but by fitting a modern time code based radio locked mechanism. Here in Europe we have DCF in Germany and MSF in the UK. DCF in particular has an astonishing geographic range for its signal.

The time code locked mechanisms are available from a number of sources and vary from a basic straightforward hours minutes seconds mechanism to ones with higher torque and some with a pendulum. The pendulum is quite independent of the time keeping but does add character. As supplied the radio locked mechanisms require you to set the hands to either 12 o’clock if you are on European time or 11 o’clock if on GMT and then you pull out a locking pin on the rear of the mechanism and install an AA battery. The mechanism will twitch momentarily and then the hands will start to rotate from the setting position to a set hour position and then hold until the mechanism gets an update from the radio signal. Once locked to the radio signal the clock will be very very accurate. You can check them against time.is and as would be expected they are spot on. When clocks need to be seasonally change the mechanism automatically updates. When the battery dies you simply put a new one in and the clock resets itself to time.

I have modified many clocks in this way and gifted quite a few to friends and family. I try wherever possible to retain the original hands and sometimes this involves a little lathe work to modify the mounting bosses.

There are two examples below including my latest find, an ex British Air Ministry office clock dated on the back as 1951. I am quite pleased with how this one has cleaned up and it is now heading to France to hang in my workshop out there.

So next time you see an unloved traditional mechanical clock gathering dust give some thought to giving it a new lease of life.

dcf clock mechanism in traditional clock — 1951 Air Ministry clock modified for DCF radio control

rear view of dcf clock mechanism in traditional clock — Rear view of ex Air Ministry clock showing new DCF radio controlled movement

example of DCF mechanism in a traditional clock case — Modified clock with DCF radio linked clock module

Similar or related subjects : –

November 2, 2018November 15, 2018

Clocks all Change – Reading Memorial Clock

The last weekend in October is clocks change here in the UK with a one hour shift back to GMT. For those that remember to do it, this delivers an extra hour in bed but it is a pain to change traditional clocks one hour back. This is even more so with Turret Clocks such as those on churches and ancient buildings. The easiest solution is to stop the mechanism on Sunday and come back to it on Monday one hour earlier to restart it. While this is the easiest method it does upset these ancient mechanisms that have just had 6 months of stable running. The alternative is to wind the mechanism forward 11 hours and drive those in earshot scatty with all the bell chimes one after another.

I was very fortunate to be invited by David Pawley to help him reset some of the clocks on his maintenance list and one in particular impressed me. This is the Memorial Clock at Reading University. The clock tower was built circa 1920 as a memorial clock to all those associated with Reading University that had not returned from the Great War. There are some 101 names recorded from WW1 and further names from WW2 and latterly from Afghanistan. It is a beautiful clock and a fitting memorial. The only sad aspect was that its enormous bell is muted these days so as not to disturb patients at the neighbouring Royal Berks hospital.

Similar or related subjects : –

September 3, 2018March 4, 2021

Tower Clocks and Cooke of York

We live in a small village and the local church has a tall spire with a tower clock movement. Some while ago my friend Dave and I were invited to have look at the workings of the clock which was quite interesting. The clock is still hand wound twice per week and it does not have any added technology to maintain the time keeping accuracy. This was some time ago and I thought nothing more of it.

Church clock movement by T Cooke of York in the village church

I am a member of the British Horological Institute (BHI) and attend the local meetings once per month. Earlier this year the subject for the monthly lecture was the Tower Clocks of Cooke of York. This was particularly poignant for me having spent my early years growing up in the York area. To my surprise that evening I discovered that the clock here in the village was a Cooke clock. For those interested the presenter of the talk, Darlah Thomas together with her husband have produced a book on the Cooke family containing a listing and description of the known Cooke clock installations and indeed the optical devices the company produced. It is a splendid volume worthy of any coffee table collection.

ISBN 978-0-9573733-3-4 — Turret Clocks of T Cooke of York by Steve and Darlah Thomas

So back to the story …. the village clock, a Cooke clock and I was living in its shadow.

At the meeting I met David Pawley who spends his life maintaining tower clock movements throughout the south of England. You can read his website Tower Time here. I mentioned where I lived and he asked if I would mind helping him with some maintenance on the village clock here in my village. He had been waiting for the striking mechanism to wind down so the weights were fully dropped and the time was rife to lubricate and check the strike pulley system. We spent a pleasant morning doing the necessary work and I enjoyed the experience.

During the activity David asked if I could further help him to remove the dials from another tower clock in the local area. The tower was on a farm estate and of wooden construction. The woodwork was in need of repair which necessitated a temporary removal of the dials and motion work. Dave (my friend) and myself duly turned up on the day to help David Pawley and had yet another interesting time working on and removing the items in question.

What impresses me is that these clocks have run for years and years. The technology available when they were designed and built was basic yet here are movements that keep to seconds accuracy after all these years.

I would not be offending David Pawley if I say he is not young and I would compliment him by saying that he carries an enormous accumulation of knowledge and skills. One day his knowledge and skills will pass into history and I do not see a new generation filling that gap. There are a lot of tower clocks in the UK and I can’t see a new generation coming forward to fill the need for maintenance.

Similar or related subjects : –