Why Brass??

[MeunierParticipant @meunier]

Posted by John Haine on 24/03/2018 17:35:11:

Clock B has dural wheels and steel lantern pinions with the pins on small ball races. By the look of the photos even the escapement wheel is dural – but with a grasshopper escapement there isn't the same wear issue.

Many thanks for that link John, it led to an interesting diversion through Frodsham's site.
Now, if I only could win a lottery……
DaveD

[John HaineParticipant @johnhaine32865]

Posted by roy entwistle on 24/03/2018 18:53:45:

John Haine A clock with a recoil escapement actually does go in reverse every beat. Though not much

Roy

Indeed, but the gear teeth always bear on the same surfaces since the reversal is forced by the pendulum.

[Gareth Jones 9Participant @garethjones9]

Hello Brian, if you're expecting an error of 10 Nm when using a sextant, then something is very wrong. Last time I used one was on a crossing from West Wales to Ireland and comparing sextant derived latitude to the GPS latitude gave a difference of less than 1.0 Nm. I accept things might be different in a gale but this was in a force 5 to 6.

Gareth

[I.M. OUTAHEREParticipant @i-m-outahere]

Any thoughts on electrolysis and oxidation or the effect it could have on the bearing surfaces ?

[Bill PudneyParticipant @billpudney37759]

Clock B was/is stunning, thanks for the link. The al.alloy, in my opinion, (for what that's worth) looks beautiful. In fact that has decided me, that should my clock project go ahead, it's going to be al. alloy., not brass.

In a former obsession/hobby I spent about 20 years making model aeroplane bits out of carbon/epoxy. For about a nano second it was considered for "my" clock. I'm sure it would be possible, but the thought of all that epoxy and bits of carbon fibre convinced me that the concept should be left to someone else to enjoy! Why should I have all the fun after all?

I had a friend who used to own a business making dental implants from Titanium. Yes threads are really excellent and the material is not hard to machine, as long as you set up correctly for it, in terms of sharp cutters etc. A big advantage is that it looks beautiful, and can be anodised gaudy colours, which would exclude me from the Hallowed Halls of Horology forever!! For me, the material would be a bit of a leap too far though, maybe for my second or third clock, should I get that far.

As far as electroysis was concerned I have a picture in my head of a small pocket in the base with some silica gel there, hidden from view by a mesh screen. As for oxidation, developing my own anodising process shouldn't be too difficult, and as others have said might improve the wear qualities. In any event up here in South Australia the atmosphere is predominantly dry, unlike other parts of Australia where extreme humidity must be considered.

All I have to do now is get on with it!!

cheers

Bill

[jaCK HobsonParticipant @jackhobson50760]

Posted by John Haine on 24/03/2018 17:35:11:

I've often thought that it's odd that clock wheels have symmetrical teeth – it's not as if they go in reverse is it? There's probably a better tooth form if you remove that constraint.

A justification for the superiority of the dead beat escapement is that it doesn't drive the train in reverse. Other escapements do. Harrison argued that cycloidal gears driven in reverse gave very different resistance compared to driven forward – the screwdriver argument in the link (but nothing to do with coefficient of friction, just levers). Harrison used lantern pinions because they don't exhibit this difference (and the grasshopper isn't dead beat).

[John HaineParticipant @johnhaine32865]

Bill, Dick Stephen a UK clockmaker has used titanium for escape wheels, on the basis that being much lighter than brass its stored energy, all of which is wasted, is less and so the clock should need less driving weight. I'm not sure if it was successful. I think that there are places where carbon fibre could be used, especially the pendulum rod, as if the layup is longitudinal its tempco can be very low. It has been said that cf rods are susceptible to absorbed humidity, which varies the mass and therefor the effective length, but I checked with a cf manufacturer and the material can be sealed with polyurethane lacquer to minimise this. Anyway the rod mass can be made very low by using thin walled tube, taking advantage of the material's strength and rigidity, so the effect of rod mass variations should be small. It would be great if you decide to go ahead with your aluminium allow clock, do share some photos.

[Sam StonesParticipant @samstones42903]

Hi Bill,

I sent you a message.

Sam

[Martin King 2Participant @martinking2]

Hi All,

Re sextant position accuracy, having done 5 Atlantic crossings in small sailboats (43-66 feet) I got fairly good with a sextant but never ever got better than 3-5 or so miles, usually earer 7-10 miles. I was able to sometimes check positions on the early trips with the odd passing ship and later against GPS 1 mile out in a 5/6 is fanatastic accuracy!

Cheers Martin

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