Hi all,
Er indoors has decided that I will build her a skeleton clock. (She came up
to Harrogate and saw one up there... that'll teach me...). I am looking for
any information. I don't want to buy a kit as that is not the same as
manafuacturing one. I want to add a little bit of uniqueness to it.
Anyway, I have been looking at past issues of Engineering in Miniature (I am
up to about vol7, though I have some vol6 missing). In there, I have seen a
longcase clock and a beginners clock. Neither of these are what I want. I
also have Model Engineer but have as yet to look through those.
Does anyone know if either of these to magazines has a skeleton clock, and
which magazines they will be in?
Alternatively, can someone recommend a book?
Can someone explain to me what "fusee movement" is?
Talking of skeleton clocks, I have just seen a magnificent clock on Ebay, of
York Minster, though going for about £2500.
formatting link
(I am not the seller.)
Thanks.
Dave.
~~
Customise your internet experience
Timekeeping is affected by variations in the strength of motive power.
As a spring runs down, the power available decreases.
The fusee is a grooved cylinder. with the cylinder reducing in diameter
(I suspect that the curve is exponential).
There is a chain which wraps around the spring barrel as the spring runs
down, and which pulls off from the fusee. The Fusee drives the clock.
When the spring is fully wound, the chain pulls off the smallest diameter
of the fusee. When the spring is unwound, it pulls off the largest diameter
of the fusee, with pro-rata between the two limits. The idea is that the
torque
(spring power X diameter) remains constant.
There is a parallel with the Derailleur gears on your bicycle in the ratio
of diameter between the pedal sprocket and the wheel sprocket, where
there is an attempt to keep the torque (required rather than delivered)
constant.
Model Engineer in 1972 vol 138 issue 3434 had an article on Skeleton clocks
running for 5 installments
Then in 1983 vol 151 and onwards there was an article on a Grasshopper
Skeleton clock that ran to 25 parts plus two extra in 1987
--
Regards,
John Stevenson
Nottingham, England.
Thanks John and Airy for your replies.
I have all the 1972 volume and am considering this. I have the first 3 of
the 1983 volume (I appear to be missing all of vol 152). I have shown 'er
indoors and she doesn't like the later one anyway, so it looks like the
earlier one.
Having looked through the mags, the main frame is made from BMS. Whilst I
could do it with this, is there any harm me making it from copper or brass?
(I am considering the use of a mixture of materials to get nice contrast.)
Also, in order to stopping the finished item tarnishing (forever polishing)
what would anyone suggest?
Thanks.
Dave.
~~
Customise your internet experience
I believe John Wilding has written books for the construction of such
clocks. Look at his web site
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A fusee is a device designed to even out the torque of the mainspring as it
unwinds. The spring is enclosed in a drum (known as a barrel) which is
connected to the fusee by a line or chain. The fusee is approximately
conical and has a groove cut into it to locate the chain/line. It also has a
gear (known as the great wheel) which connects to the rest of the train. A
fully wound spring has a high torque initially so the line operates on the
smallest diameter of the fusee, as the spring unwinds so its torque
decreases and the line operates on increasingly larger diameters of the
fusee. The slope of the fusee needs to be matched to the spring
characteristics to obtain a reasonably constant torque.
Cliff Coggin
Kent
UK
The message
from "Dave" contains these
words:
Dave.
John Wilding has a good book "The Construction of a crystal wheel
skeleton clock". His books are very informative and easy to follow.
Bill Lamond
Dave,
A brass "frame" is fine and more traditional (as well as being IMO more
attractive). I haven't seen the designs referenced here but I suspect that
BMS may have been used to keep the cost down. Skeleton clock frames were
usually made from brass (sometimes cast) and were typically around 4 to 8 mm
thick dependant upon the overall size of the clock. The frames need to be
thick if it is going to be a fusee movement as the springs required are
relatively large and powerful, and being 'skeletonised' there are a number
of weak points built in when compared with a non-skeletonised movement. Odd
as it may seem, brass plates do not need bushing (until they have been
running for 50 years or so).
I have never seen clock made in copper, I suspect it may be too soft and too
expensive.
Brass skeleton clock frames are often lacquered to keep the tarnish at bay
although, in my experience, if a clock is covered by a reasonably well
sealed dome or case, they only need repolishing every 5 years or so. Mostly,
unless ball races are used, the clock needs to be thoroughly serviced (and
therefore stripped down) every 5 years anyway, so it's not a big deal if you
don't lacquer it. If you do lacquer it, make sure the lacquer is removed
from the pivot holes.
If you're not already 'geared up' to build clocks, the things to consider
are:
a) How are you going to make the fusee? - If you have a CNC lathe or 4-axis
CNC'd mill then life is good, otherwise you will need to make or buy a fusee
cutter for the lathe (they are available to buy but they're quite pricey).
b) Does the design you're using require many gear cutters? Remember that
wheels and pinions need different cutters and each different module size
needs a different cutter - cutters can also be pricey. Single point cutters
are fairly easy to make but are no good for pinions. Lantern pinions may be
the answer in these circumstances. Multi-toothed cutters are a nightmare to
make and are seldom worth it for 'one-offs'.
c) You will need a depthing tool, again, they are expensive to buy although
some designs are reasonably easy to make.
I hope it helps. I have designed and built a number of clocks (including
skeletons) in the past, so if I can be of any help, feel free to ask any
questions.
Regards
Mark
Somebody must make fusee cutters in the first place, and surely
it is one of the strengths of we model engineers that we can turn our
hands to making anything?
18 Feb 72 Model Engineer has an article on a tool to cut the groove, once
the fusee shape (exponential?) has been cut.
The article is reproduced in Chapter 29 of "Tools for the Clockmaker &
Repairer", one of those John Wilding books that are photostatted and
edge bound. (OK - I admit to buying a couple of them!)
For a good general intro to clocks and watches, Adam Harris at
camdenmin.co.uk is publishing a facsimile of the 1914 edition
of Britten's "Watch and Clockmaker's Handbook Dictionary and Guide".
Dave wrote in message ...
There is an Alan Timmins design for a skeleton clock in volume 3 of EIM
(1981). is this any good for you. *somewhere* i will have these issues if
you need a photocopy.
regards
Bob
Can you throw some light on something that has bugged me in the past?
I recall reading the that the 'best' fusees- ie those the most accurate
clocks- had a curved slope, a "wasted parabola" was the description, as I
recall. Did the early clock makers have the knowledge, facilities, and
consistent quality materials (esp the spring) to determine the shape
mathematically or was it all trial and error?
I believe the slope was determined empirically i.e. almost trial-and-error.
Even if the slope of the fusee was not well matched to the spring, there
would still be a dramatic levelling of the output torque compared to a
spring without a fusee.
Cliff.
The message
from "Dave" contains these
words:
Dave
If you are thinking of getting any of John Wildings books, which I would
heartily recommend, try giving the BHI a ring.
British Horological Institute. Upton Hall, Upton, Newark, Notts. UK. NG23 5TE
Telephone (01636) 813795
They used to stock them, and recently they were selling them at a
reduced rate. At any rate they are, in my opinion, well worth while for
amateur clock makers like me.
Brian,
I have just had a look in Britten's, and we get the following .....
"To determine the shape of the fusee is much more complicated and
requires first of all that the mainspring output curve is determined."
I note also that there is an entry for 'Fusee Engine'. Here we read
..... "A form of screw cutting or threading machine for forming the
grooves in fusees; the shape of the fusee can be controlled by a guide
plate which has to be changed for each different fusee."
The Fusee was invented c.1450, perhaps earlier - it says.
Thinking about it, I suppose that when the spring is fully unwound the
fusee is of infinite diameter! :)
Mike
I don't agree with you. There's a lot of nonsense and silly taboo
in this country on an event that we shall all experience. There have been
300,000 further deaths throughout the world since the time of that
discussion,
deaths which have not stirred a tear in anyone's (from this NG) eye. Does
anyone
hear feel guilty that they did not shed a tear for each and every one
of those 300,000 corpses or their near relatives?
No, they didn't.
By the same token I did not shed a tear not experience any
emotional reaction from the OP and I said so, and dissociated
myself from the OP.
Perhaps there are those reading this Ng who dislike truth, or who
dislike truth about themselves?
This matter has its genesis in a discussion a few months ago
about driving stepper motors direct from PC's. I had some
commercial experience of this and so I shared it in all
sincerity with the NG.
John Stevenson did not understand the technical issues
involved and resorted to a series of rather silly and infantile
outbursts, getting more and more offensive with each of his postings.
Every one of those postings of his was out of place in a public
discussion forum.
I criticised him for the anti-social way in which he was posting to
a public discussion forum, but I did not realise that he was the leader of
a gang of escapees from the school playground. They all rounded
on me and have continued to do so ever since, on the slightest pretence.
My position in this NG has always been a technical stance, and a stance
for civilised and mature behaviour. I criticised a number of people
for their infantile and silly posts, and I stand by that criticism.
I can thoroughly recommend that book, as the name suggests, it is in
dictionary form but it covers a phenomenal range of horological subjects,
some are maybe outdated now with our modern machinery and materials but will
give you a pretty thorough knowledge base. It's a 'must have'.
There is also what is probably a companion to it, again by Britten, called
"Horological Hints and Helps" which is also very helpful.
Mark
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