Drumhead fell off!!

[Dee]

Hi,

Purchased at auction last week a bit of a wreck of what was once a beautiful French drumhead clock comprising slate and marble.  Nothing particularly wrong with it other than the case has been painted with 'distressed' paint but can easily been wet sanded down and marblacked and re- polished and the works probably haven't been touched since it was made.  Someone has also taken the brocot arbor out as well! 

Main problem is the drumhead at some time has detached itself from the base and someone stuck it back on with bostick!!!  Needless to say it has come off again having sat in an auction room in this hot weather, not surprising really, whoever had it broke one of the straps that hold the works in and so glued the works into the case at the front with gorilla glue or some such like which I have successfully managed to get off and the back door was held on with silicone

The works are now out of the drumhead and I have started to renovate the head casing.  I have searched on the net but cannot find out how the drumheads were originally attached to their base.  Anyone here know how??

Many thanks

Dee

 

[wls1971]

Slate clocks  are held together with internal metal bars or hooks. The bars usually fit into internal holes drilled into the inside surfaces of limestone which are used as a backing to the black slate. On a drum head clock the metal bars are in the form of hooks one on each side of the clock the hooks are then coated with large amounts of plaster of Paris to secure them in place.

The problem with these clocks is that people try and move them by holding the top of the clock when they should only ever be lifted by the base.

I personally would not sand the surface of the clock can't you remove the paint with meths the surface underneath may be in good condition, if it is using small amounts of baby oil on a cloth and a bit of elbow grease can bring back a jet black finish to the surface this works on clocks that have gone very gray over time, the slate is very porous despite appearances and the oil penetrates the surface.

This pdf will give you a idea of how marble clocks are constructed

http://www.clockandwatchclub.com/articles/restoration/Marble Case Restoration.pdf

[clockboy]

A picture might help not sure what the drum head is. Slate clocks are normally made of Belgian Calcite which is a very porus material. Some of the parts can be re-affixed using tile cement. 

 

 

[oldhippy]

The movement is normally screwed to the bezel. Both are inserted by the front of the case, on the side of the bezel piece are two straps, which normally have been riveted to the side of the bezel. Some cases can be found with a thin metal inside with a cut out at the bottom for the pendulum to hang down in. These thin metal insides are normally used to hide the rough finish to the inside of the case. Inside the case there should be to protruding metal rings, one each side. You should have two long screws, these are fitted through the rings and then screwed into each straps, make sure you have the 12 o’clock on the dial centred and not too one side as this will make the movement out of beat, when you are happy with the position you tighten the screws so the movement won’t move when winding it up. If it has a back door you put the screws through first and tighten making sure the hinge is at right angles to the case. More than likely you will need to bend the crutch a little to obtain a good even beat.

I do not recommend taking any type of clock case apart unless you know what you are doing. These slate clock cases can be a nightmare.    

[Dee]

Thank you oldhippy, clock boy and wls.

The clock has sat in the garage since I bought it last week.  Had a closer inspection to see if the rods with the hooks, (see another reply), were still there to re-attach the drum head.  Regrettably they are not.  Judging from the inside of the case the base and drumhead have completely let go at some stage as the base has also been re-glued back on.  I do not know what with but it appears fairly stable and solid. It shows in the inside pics.  As the rods that held the drum head on are gone any ideas how I can put it back on.  Is it possible to make rods and use p of p to attach them?  Also the marble on the roundel is damaged and seems to be going powdery.  I attach some photos..  It has been beautiful at some stage.  The poor thing is a total wreck but I will get it looking nice again and ticking.  Unfortunately I am a sucker for these wrecks but it seems so sad to just throw them away without trying

[oldhippy]

What do you have of the bezel movement and back? Photos if possable.

[Dee]

Many thank yous for your help with this.

Photos attached.

The movement is large and heavy and is a Marti.  Again someone previous has tried to detach the dial from the works and only managed to lift one side so the works are loose on one side of the dial.  Both retaining straps are broken but looking on Cousins site they do replacement straps so that is a bonus.  The brocot arbor is gone and I have yet to find a place that do replacements.  The works are probably above my abilities and will have to be taken somewhere to be overhauled. The works when fitted into the drumhead will fit nicely once the straps are replaced, just getting it to stay on its base will be the fun part I think.

[oldhippy]

You need two new straps and screws. You fix them with rivets to the side just like the broken one you have. The straps come with screws. Then follow what I previous posted.You can increases the tightness by fixing nuts to the screws, but be careful you could pull the rivets through. I have seen many brocot stems on ebay. The movement should be held in place by steel pins.

 

What you have is a French rack striking on a bell movement with visible escapement, I expect it is of 8-day duration. I cannot see the numbers on the back very well. One lot represents the movement number; the pendulum should have the same numbers, if no it is not the original pendulum. The other set is the French measurement of the pendulum.   

[clockboy]

Cousins supply French movement straps not sure if those sold are suitable. 

https://www.cousinsuk.com/product/movement-strap

[Lenj]

Hi Dee,

I like the old drumhead clocks, and slates in general, Good sheet from WLS..I have stuck many a slate clock back together, and plaster of Paris is the only thing to use the best there is, just like it was originally done..No matter how hard you try with Epoxy resin you will always have some that spills out and the more you try to clean it off the more it penetrates the porous slate ruining it..

You need to get ALL that Bostic or what ever it is off, whilst in bits you should clean the rest..Everyone has their own way of doing things, saying that when you come to fit the parts together, make sure all are clean and the parts that you are sticking together are wet!! if you do this dry you will not have enough time to position the pieces, because has soon as you put them together the water in the plaster of Paris is suck out so quick, if not positioned right you will have a job getting them apart, trust me been there done that, and never again. Don't worry about making a mess with the plaster of Paris it comes off easily, unlike epoxy resin and the likes..Sometimes you have to sand down the parts with wet and dry if they are bad, finishing up on the finest..Here is a clock

that I restored and was very badly pitted and the slate greyed out in places..You used to be able to get an oil based "Slateblack" it was the best, but as most things they stopped making it now, I had the last tin From Meadows and Passmore and I sill have a drop left for when I need it.. Personally I don't like the Marblack if you put it on too thick it puts what's seems like a layer of carbon on the slate, anyway that's just me..As I say everyone has their own way of doing things..I hope you have fun with your slate clock.. 

[Dee]

Many thanks for your help in this,  some very useful tips I had not come across.

Lenj.  That clock looked absolutely beautiful and what a shine.  I hope I can live up to that with this case.  I am currently trying your method on one of my clock cases that is starting to dull down.

When I finally get the drumhead sorted out I will post pictures.  Won't be for a while yet though.  When it comes to it, I think I will try making new rods to hold the drumhead on and use p of p to fix them in place.  I would have liked to have given a go at taking the case apart and putting it back together but I am concerned that the marble on it is in quite poor condition and I have a sneaky feeling that once off it probably won't go back on except in small pieces!!  The roundel in the picture is very bad and is powdering and flaking away at one spot.  Oldhippy says it is something not to do if you don't know what you are doing.  At some stage I will pick up an old case that come up for sale and experiment on that, rather than completely wreck the drumhead case so it's completely useless.  At least at the minute it looks like a clock case!!!LOL

[Lenj]

Hi,

I agree with Oldhippy what ever you do try and take these clocks apart, I read somewhere that special jigs were used to make these slate clocks and to hold them together, something that I would not attempt. I have another old video that I did with the same open escapement movement. I say video, these were just photos that I took doing the clock and noticed in Picasa that you could make videos from photos, so this is not really a video..In this one there are some School/wall clocks that I made, all handmade except for the dial and bezel, the rest including the hands which I made from old broken French clock springs.. The Slate clock in this one was stinking and stained with tobacco smoke you can see on the Malachite how bad it was..

Here is the link