Pendulum spring steel hangers

[Mick B1Participant @mickb1]

I've done some work on clocks as volunteer for the railway, and now they've given me a pendulum to fix, and a pretty substantial one in my view. It's nearly 1,20 M long and probably weighs more than 5 kg. It has a hanger bar with turned ends at the top and the whole of the rest of the mass is suspended from 2 spring steel strips 7mm wide and 0,19mm thick (say .0075" ). They're 30mm or 1 3/16" long, with 2 holes 3,5ish or 9/64" diameter and 19mm or 3/4" apart.

One of these strips has broken (age or fatigue) and they'd like me to replace both. The steel feels pretty hard and springy on the remaining unbroken one despite its thinness.

My questions are:

• Are railway master clock pendulum suspension strips a standard component, and if so, where if anywhere could they be bought?
• If not, what might I get away with as a substitute? I have some 10-thou shim somewhere that I could cut and drill to suit. Not sure how critical the deflection-per-unit-force might be.

 

Edited By Mick B1 on 19/09/2021 16:30:45

[Mick B1Participant @mickb1]

[David NobleParticipant @davidnoble71990]

Ian Cobb is your man. PM me if you can’t find him.

David

[Martin KyteParticipant @martinkyte99762]

Try and stick to the dimensions of the original as far as possible. Slightly thicker wont matter much. Source the material from either shim stock, feeler guages or take a look on the Cousins or Meadows and Passmore sites. Your best bet for creating holes is punching. Make a simple tool comprising a couple of pieces of steel plate doweled together with a nicely drilled and reamed hole/holes to take a silver steel punch. For one off use dont bother hardening. You will get a nice hole without raggedness or burrs to create failure points.

best of luck.

regards Martin

[Mick B1Participant @mickb1]

Posted by Martin Kyte on 19/09/2021 16:45:41:

Try and stick to the dimensions of the original as far as possible. Slightly thicker wont matter much. Source the material from either shim stock, feeler guages or take a look on the Cousins or Meadows and Passmore sites. Your best bet for creating holes is punching. Make a simple tool comprising a couple of pieces of steel plate doweled together with a nicely drilled and reamed hole/holes to take a silver steel punch. For one off use dont bother hardening. You will get a nice hole without raggedness or burrs to create failure points.

best of luck.

regards Martin

Thank you very much, Martin. Helpful advice, and the websites are quite an education!

[Mick B1Participant @mickb1]

Posted by David Noble on 19/09/2021 16:39:59:

Ian Cobb is your man. PM me if you can’t find him.

David

Thanks to you too. I guess what I'm after is 'suspension spring steel' as on Ian's website.

[the artfull-codgerParticipant @theartfull-codger]

When I used to repair clocks I used an old steel tape measure taken to bits & the spring at the back of the measuring tape was just right for the ones I repaired, I've wound the local town hall clock up for 29 yrs[ A Gillet & Bland Turret clock] it has a wooden pendulum rod & a large cast iron bob, The suspension spring broke & the rating nut made a nice hole in the floor[still there] it was about 14 thou thick,I had an old panel saw in the workshop so I bent the blade to the handle left & right & it went back perfectly straight so I cut a piece off making sure it was longways machined it up & linished it down from18 thou to 14 fitted it with my sons help,& smeared it with grease to prevent rust & it's been on ever since about 25 yrs!! I mentioned it to a local colleague & he said that it would be good spring temper steel [He's a local prominent clock maker & repairer & one of the finest if not the finest in the country]

[Mick B1Participant @mickb1]

Posted by the artfull-codger on 19/09/2021 19:00:32:

When I used to repair clocks I used an old steel tape measure taken to bits & the spring at the back of the measuring tape was just right for the ones I repaired…

Hi Artfull, if Ian Cobb's still selling suspension steel, that'd be easier and cheaper than trashing a tape rule. Anyway, mine keep being taken by gremlins…

Guess I'll be finding a feeler gauge set if there ain't no other option.

[duncan webster 1Participant @duncanwebster1]

I've got the return spring from a retractable dog lead here. It is 0.2mm thick * 8mm wide. If It's any use pm me your dirt mail address and I'll send it to you

[Mick B1Participant @mickb1]

Posted by duncan webster on 20/09/2021 00:22:02:

I've got the return spring from a retractable dog lead here. It is 0.2mm thick * 8mm wide. If It's any use pm me your dirt mail address and I'll send it to you

Thanks very much, but I don't know whether the spiral set and possible work-hardening would be an issue, or how well I could correct it if it is…

Hopefully Ian Cobb will return a quote shortly for the strip material they sell.

Edited By Mick B1 on 20/09/2021 11:15:40

[Bob StevensonParticipant @bobstevenson13909]

Old feeler guages where the blades are broken are a good source……I used these in my first clock and don't plan on using anything else…..except, there are some nice stainless steel stocks now that have the added benefit of being rustless.

[Roger WoollettParticipant @rogerwoollett53105]

If all else fails search ebay for "mainspring 7mm" I fouind one 0.20mm for £8.99. About the right size and would give you lots left over for another time.

[John HaineParticipant @johnhaine32865]

I use beryllium copper CuBe shim for my suspension springs. I tried to get some a few years back and managed to find a UK supplier and agreed with their sales guy that it would be easier for them to supply a free sample rather than invoice for the minuscule amount needed. The sample came as several metres of 2 inch wide stock on a foot diameter reel! I have enough for the world's pendulum clocks for the next century I think…happy to donate a few inches.

IIRC it's 0.1mm thick.

Edited By John Haine on 20/09/2021 12:18:45

[roy entwistleParticipant @royentwistle24699]

You can ( or could ) buy individual Starrat feeler gauge blades. They will need to be narrowed.

Roy

[Mick B1Participant @mickb1]

Well, thanks for the advice everyone. I went with David's suggestion and got 150mm of 1/2" x 0.008" suspension spring steel from Ian T Cobb, £5.75 including postage, which arrived this afternoon – excellent service!

Subjectively, it feels similarly springy to the original.

Seeing as I had enough for more than 1 attempt, I cut 2 strips 30 x 7mm with tinsnips, then put together one of my teeth-grinding setups, using two slightly longer strips of 1/16" thick alli to sandwich the spring steel in a pair of toolmaker's clamps:-

My hope was that the alli would support the drill and the spring steel and allow me to drill the 2 x 3,5 mm holes with a clean breakthrough – and this definitely worked:-

The upper, rust-spotted strip is the unbroken original; the lower 2 are my copies. OK, so the holes aren't laterally central, but I don't see that that'll matter much because it's the clamping force of the upper and lower blocks that holds the strips, rather than the screws in shear. Anyway, the original is offcentre too. What probably does matter is that the hole spacing is the same as the original and identical for the 2 strips, which it is.

I'll put this together, and I think it'll work. If it doesn't, I'll make another pair more precisely.

Edited By Mick B1 on 22/09/2021 21:47:16

[David NobleParticipant @davidnoble71990]

Glad to see you got there Mick

David

[Paul LousickParticipant @paullousick59116]

I see your problem has been solved.

For your info, there are lots of clock springs available on ebay of different widths and thicknesses.

Paul

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