Help Broken pendulum

klocken

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Feb 25, 2011
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I am going to have to make a replacement wood pendulum for a weight driven Vienna regulator probably from the 1920's. Does anyone know what the best wood to use for this replacement would be? Cherry wood maybe? I have the woodworking tools to carve it but I have never made one before. It measures 25 1/2". That is the wood itself but the hook and rating assembly not included in that measurement. How do you figure out the weight with the bob and does that need to be considered when choosing the wood?

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Willie X

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Feb 9, 2008
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They are usually made of close grain pine. I would stay away from any kind of hardwood, mainly because the extra weight will make your pendulum come out longer. Now, if you have an extra inch or so at the bottom, a heavier wood would probably be fine. I usually paint them dull or flat black. That' a lot easier and always looks better than trying to match the old finish. Good luck,. Willie X
 

shutterbug

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There are a lot of Vienna's that have been taken apart and sold for parts. You might keep an eye on the auction sites and find an original.
 

NEW65

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Yes, the wooden pendulum sticks painted black , remind me of the James Stewart long case clocks from Ireland. Their clock cases were excellent quality , truly fantastic manufacturer.
 

klocken

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They are usually made of close grain pine. I would stay away from any kind of hardwood, mainly because the extra weight will make your pendulum come out longer. Now, if you have an extra inch or so at the bottom, a heavier wood would probably be fine. I usually paint them dull or flat black. That' a lot easier and always looks better than trying to match the old finish. Good luck,. Willie X
I am going to use the hook and rating assembly from the original pendulum if I can take the rivets off of the rating assembly. I am planning on grinding off the old rivets and installing new wire and pinging the new rivets on hopefully without scratching up the old parts. I have never done that before. I am not sure what wire to get to use as rivets but I am looking at the parts houses to see what's available.
 

tom427cid

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I am going to use the hook and rating assembly from the original pendulum if I can take the rivets off of the rating assembly. I am planning on grinding off the old rivets and installing new wire and pinging the new rivets on hopefully without scratching up the old parts. I have never done that before. I am not sure what wire to get to use as rivets but I am looking at the parts houses to see what's available.
Hi,
If you choose to use Pine I would suggest that you find a well seasoned piece that has a very straight grain, I have made quite a few of these and I prefer Beech, stronger, tighter grain, and easier to color.
Because these are very thin and therefore fragile I have made a couple of planning supports. Quite simple actually, a piece of Poplar that I planed concave to match the curve of the original stick. I then take whatever specie of wood I have selected for the pendulum stick and plane the first curve. Convex. I use a block plane (weapon of choice) also easier to manipulate. The support also acts a guide for the curve. When that side is done I rip the strip off(give yourself a little extra) and set it in the support with a small clamp and match the first side. At the same time you can also adjust the thickness. Should take less time to do than it took me to write this!!!!!! Good Luck.
Hope this helps.
tom
 

svenedin

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I read somewhere about why wooden pendulum rods were chosen for the Viennas (probably I read this in the clock museum in Vienna). It was to do with temperature effects. Some of the Viennas had Harisson's gridiron pendulum and others the mercury compensated pendulum. These were expensive and difficult to make. It was found that wood had a low coefficient of thermal expansion and so kept good time even with fluctuating temperatures and of course was much cheaper. The problem was that moisture did have an effect on wood so the rods were fashioned and then soaked in oil to prevent changing moisture levels altering the length. Later they were painted black "ebonised" which presumably has a similar effect. I do not know what type of wood was traditionally used.

The period of a pendulum is related to the centre of mass of the whole assembly (rod and bob). Usually with a light rod and a heavy bob that centre of mass is going to be somewhere on the bob but yes, the weight of your rod will affect the length needed to keep correct time. That difference may be negligible though given that the rod is much lighter than the bob.Unless there is a gross disparity between the densities of the woods I would make your replacement rod the same length as the original and any adjustment required can be taken up by adjusting the bob rating nut.
 
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Willie X

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I would make it about 1" longer and go from there no matter what kind of wood you use. Hardwood is generally about 50% heavier than pine. Most sticks are simply stained and varnished, nothing special or unusual.
Note, all the suppliers sell 3/4" pendulum sticks for modern clocks. This is a good replacement for most Vienna style wall clocks. I would order two of three, that way you will probably get one or two nice straight ones. The not so straight ones can still be used in shorter case clocks. Willie X
 

bikerclockguy

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If you have table saw with a rip fence, you could cut one off the side of a dowel or broom stick.
 

shutterbug

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Corner panel slats make pretty decent pendulums too, without too much work.
 

klocken

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Sorry I haven't posted for the past week. We were dealing with no power for a few days and one broken pipe. i appreciate the suggestions about how to fix this broken pendulum and I will be attempting this fix soon. Thank you
 
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Rod Schaffter

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Glad you are OK. I lived in College Station for 4 years and we had a couple of cold snaps, but nothing like the past couple of weeks.
 

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