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Re: Reinventing a Synchronome

John Haine
 

Thanks for the comments Roger - my programming skills will be tested to the limit pretty soon!  I've seen your results on your website and as you say barometric pressure has a big effect.  Have you tried compensating it?  Douglas Bateman has made a clock rather similar to yours and fitted an aneroid capsule with good results - I think it's described in HJ relatively recently, and there was certainly an article by someone else in the last year or so. 

Alternatively, and something that I may investigate when/if I get this thing going, it turns out that there is a specific amplitude where to a first order the rate of any pendulum does not vary with atmospheric pressure.  If the pressure rises, the bob gets lighter and the clock slows down.  But also, the increased air drag reduces the amplitude which increases the rate - at the right amplitude these can be made to cancel out.  This is what John Harrison probably discovered, and it is one of the major reasons why "Clock B" at Greenwich is so good.  There's a guy in the US, Doug Drumheller, who has worked out the theory and suggested a way to make measurements to predict the required amplitude.  This is one reason why I am going to make the number of swings between impulses variable, so the average amplitude can be adjusted to see if I can get this working.  I'll check with Doug and see if it would be possible to post copies of his articles here.

I don't have high expectations that the timekeeping will be wonderful, but I'm hopeful!  Mainly I'd like it to be quieter.  Yes, my bob is supported on a "ledge" halfway up its bore, but there is a short length of threaded adjuster between the bottom of the rod and the nut.  I've got a couple of ideas about how to compensate the pendulum's actual variation, but want to get it going first!


Re: Reinventing a Synchronome

RICHARD ADAMEK
 

I didn't grasp the comparison either but from the steam world, it is not widely realised that the scotch yoke produces simple harmonic motion as opposed to the crank and con rod, where there is an uneven angularity effect which dogged designers of valvegears. Probably not relevant but might come in useful for somebody someday.

Richard in the wild and windy Boglands of Norfolk



On Wednesday, 13 March 2019, 13:28:34 GMT, John Haine <john.haine@...> wrote:


Thanks for the observation Stuart.  Please could you explain why you think this, and also why the comparison to a Scotch yoke?  


Re: Reinventing a Synchronome

wwwrogerj.codotuk@...
 

Hi John..Firstly I'm very envious of your mechanical, electronic and programming ability..I'm sure your 'Nome clone will turn out to be a work of art !
I have a couple of questions...First HJ develeoped the 'Nome over a number of years with enormous resources at his disposal. The result is that a 1936 'Nome is already an exceptionaly accurate  timepiece when set up correctly. I did see on this forum a suggestion that the "shock" of the resetting gravity arm worried someone but of course, at the time it was instrumental in HJ's plan to perfect the problem of sharrp, clean contact that did not rob the pendulum of energy..Such interferences to the pendulums motion that do exist are exactly repectitive, time wise.

In my own DIY  optically sensed and Hipp Toggle style, magnetically impulsedd clock I've found that the random external influences - temp and barometric pressure - are the final challenge and I've yet to proove that its timekeeping is any better than a standard 'Nome..Mine is regularly compared with Mike's 'Nome,( another forum member), using his Pi monitoring system. This is in spite of currently running a test with the temperature inside the case regulated to 22C..It is so frustrating to see the drift changing all the time in sync with Barometric pressure..Storm Gareth passing thru for instance and the much worse deep depression a few days ago..

So the first question. Any prediction (or even aspiration ) about how much better your ingenious design will be at timekeeping than a standard 'Nome ?
The second question is about the carbon fibre rod with near 0 temp coef. I have long held the opinion that the small coef of T of the Invar rod (+ the mild steel 4Ba threaded section)  is compensated in a 'Nome by the upward expansion of the bottom supported bob...What do you think and are you planning on a bob supported by a shoulder at the middle of its height ?
Roger


Re: Reinventing a Synchronome

John Haine
 

Thanks for the observation Stuart.  Please could you explain why you think this, and also why the comparison to a Scotch yoke?  


Re: Reinventing a Synchronome

Dr Stuart Harrison
 

Dear John,
Thank you for your notes on your project. I think you will have difficulty lifting the gravity bar  reliably with what is effectively a 'Scotch yoke'.
I have tried to upload a file of my ongoing development of two Synchronome clocks but are having difficulty.
Kind regards,
Stuart Harrison


New file uploaded to synchronome1@groups.io

synchronome1@groups.io Notification <synchronome1+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the synchronome1@groups.io group.

File: Synch Rev.pdf

Uploaded By:

Description:

You can access this file at the URL:
https://groups.io/g/synchronome1/files/Synch%20Rev.pdf

Cheers,
The Groups.io Team


Re: New Member

highpwr@...
 

Steve,
I'd like to maintain the scratch built theme and I have already purchased the steel for the back plate so will continue on with my own design.  Thank you for the offer.
I am sure I will be back here looking for help as I attempt to complete the build and get it running.    
Larry


Re: Thanks for the invite.

wwwrogerj.codotuk@...
 

.Hi Bob..I think you must be S*****r from another forum ? I've not done a lot of posting or even lurking for a while although clock fiddling has gone on unabated ! Mostly with the DIY clock - which is still not finished..However as I said in my starter post I'm starting on another similar one...Roger


Re: New Member

Steve Berger
 

Hi Larry,
I have an extra casting available if it might help your project along.
Best regards Steve
AZ, USA



On Mar 8, 2019, at 7:44 AM, highpwr via Groups.Io <highpwr@...> wrote:

Thank you for the invite to the group.  Residing in the USA there is not much local activity in Synchronome collecting and restoration so I decided that building a Synchronome from scratch would be a worthy and interesting project.  I have not done much on the project lately but did manage to build a gravity arm, solenoid parts, turn a pendulum bob from cast iron, acquire invar rod and a working synchronome slave dial.  I am now waiting for a resurgence in my interest level (too many other competing projects and hobbies).  Maybe joining this group will help me restart my Synchronome build.

Larry <IMG_20141229_130635_190 _3_.jpg>


Re: Reinventing a Synchronome

John Haine
 

Oops on the diode - thanks.

Actually the on-board Arduino pullup is 20k, so the effective pullup will be ~12k, giving a wetting current of ~0.5 mA.  We'll see how that gets on.


Re: Reinventing a Synchronome

neil
 

Hi John,
                Looking at your clock pulser - a couple of suggestions:
 the diode D1 across the clock dial is back to front.
I would suggest 1k pullups in place of the 22k at R6 and R7, because the 22k will only give you about 0.2mA of switch current which is too low.
A protection diode across the LM7809 is a good idea and will protect it from reverse polarity if the input supply goes below the volatge on C3.

cheers
Neil
On 10/03/19 1:27 AM, John Haine wrote:

To avoid making the thread very long with photos etc I've created a folder over in "Files" called iSynchronome, and to get the ball rolling uploaded the initial schematic for the electronics which I now need to get on and build.


Re: Reinventing a Synchronome

Darren Conway
 

Hi

It seems to me that you are using so little of the original clock you could have done it without a donor clock.

--

Dazz

Virus-free. www.avast.com


Re: Reinventing a Synchronome

John Haine
 

To avoid making the thread very long with photos etc I've created a folder over in "Files" called iSynchronome, and to get the ball rolling uploaded the initial schematic for the electronics which I now need to get on and build.


Re: New Member

James Kelly
 

Hi Larry

welcome to the group, looks like you’ve made a good start, hopefully you’ll feel inspired to finish you’re project.

ATB

Jim


New Member

highpwr@...
 

Thank you for the invite to the group.  Residing in the USA there is not much local activity in Synchronome collecting and restoration so I decided that building a Synchronome from scratch would be a worthy and interesting project.  I have not done much on the project lately but did manage to build a gravity arm, solenoid parts, turn a pendulum bob from cast iron, acquire invar rod and a working synchronome slave dial.  I am now waiting for a resurgence in my interest level (too many other competing projects and hobbies).  Maybe joining this group will help me restart my Synchronome build.

Larry


Re: Reinventing a Synchronome

John Haine
 

That's what I'm hoping!  Time will tell.


Re: Reinventing a Synchronome

Rob
 

Thanks John,

Good old Araldite, sticks anything to anything else :-)

Regards

Rob

On Thu, 7 Mar 2019, 21:15 John Haine, <john.haine@...> wrote:
Rob, the CF is 10 mm OD tube, 8 mm bore.  There is a 25 mm slug of 8 mm aluminium rod araldited into the bore at each end.  At the top there's a 3 mm cross hole with a bolt through it that holds the rod into the lower chops of the suspension.  The bottom slug has an M4 rating screw tapped and loctited into it.  As the inside of the bore is quite rough, and I believe the CF is laid up with epoxy, I'm hoping that the lower joint will hold but may drill another cross-hole for a pin just in case.  


Re: Reinventing a Synchronome

John Haine
 

Rob, the CF is 10 mm OD tube, 8 mm bore.  There is a 25 mm slug of 8 mm aluminium rod araldited into the bore at each end.  At the top there's a 3 mm cross hole with a bolt through it that holds the rod into the lower chops of the suspension.  The bottom slug has an M4 rating screw tapped and loctited into it.  As the inside of the bore is quite rough, and I believe the CF is laid up with epoxy, I'm hoping that the lower joint will hold but may drill another cross-hole for a pin just in case.  


Re: Reinventing a Synchronome

neil
 

Hi John
I have also been working along similar lines, but all home made. Hopefully yours will be running before mine is.  I have 3 optos ( as seen in the pix) to sense the BTD of the pendulum but also to detect when the amplitude falls off to a preset point, when i will impulse the pendulum again magnetically. ( an electronic Hipp toggle if you like)  The coil is on the LHS with the LED across it is the impulse electromagnet, which "sucks in" the steel rod.  I'm using an Atmega micro, not the Arduino, but same thing. Just different language.  The bob is a massive chunk of cast iron on a brass sleeve for temp compensation, on a 3/8 invar rod. The suspension I built along the lines of the recommendations in Matthys book Accurate Clock Pendulums, but in hind sight it could be better. I have had it running, but other things have got in the way, and at the moment its a project still. 
Neil
New Zealand.
On 08/03/19 8:16 AM, Rob wrote:

Hi John,

 I am interested in this project. I was wondering how you are going to connect the bob onto the carbon fibre rod. I have been interested in cycling for many years and there it has always been a task to bond carbon an steel or aluminium together. I would be interesting to see how this project ends up

Regards

Rob Lockyer


Re: Reinventing a Synchronome

Rob
 

Hi John,

 I am interested in this project. I was wondering how you are going to connect the bob onto the carbon fibre rod. I have been interested in cycling for many years and there it has always been a task to bond carbon an steel or aluminium together. I would be interesting to see how this project ends up

Regards

Rob Lockyer

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