First clock suggestions

.

John,

Yes, that ^^^ is an excellent page ... I make no claim to priority, but it's the one that I was pointing Sam towards when I wrote earler:

[quote] There is some very interesting reading on [and linked from] this page. [/quote]

MichaelG.

.

Sam (aka Denis) : you really should sit down quietly some time, and read it.

I read 'the lost science ... of harrison' by Laycock and came away with the conclusion that Harrisons prime concern for gear teeth was for the friction to be consistent in forward and reverse which allowed him to dismiss concern about recoil in the escapement design.

The book also shows in detail the problem with depthing errors, as suggested in the excellent linked page above, and further suggests that the usual depthng technique tends to introduce depthing errors (when driven forward, gears tend to feel better at slightly larger depth distance than therory).

I may have remembered that wrong.

The biggest trouble with a clock train is that you have a large wheel driving a small pinion all through the train Apparently this is the least efficient and why friction has to be kept to a minimum

Roy

Michael, it's on the same website but a different page! I found this link ages ago and it still works, though it isn't actually linked on the csparks site itself. This is an article by a guy very experienced in mass production of clockwork fuses on how cycloidal gears caused huge problems and why involute ones were much better.

(Actually just checked and it is linked right at the bottom of the page I think you pointed to.)

Edited By John Haine on 30/03/2016 09:22:23

.

John,

This isn't worth debating, but ... I wrote "[and linked from]"

... Which it is:

"Finally, I would like to mention a privately published monograph by my gear-expert friend, Richard Thoen."

MichaelG.

.

Edit: inserted quote from web page.

Edited By Michael Gilligan on 30/03/2016 09:26:58

OK Michael, But it had better be good!!!

Only joking and thanks for your persistence.

Yes, sure, sorry!

.

It is !!

John and I agree

MichaelG.

Nice looking clock Brian. I have recently completed the month going version and am in the process of making the case. Metalwork is much easier though!

Russell.

I'm surprised no one has mentioned the advantage that cycloid does have - freedom from undercutting at very low tooth counts. The involute answer to that is stub forms however animations can be found for 2 tooth cycloids. The sort of thing that might be used in a pump. Undercutting in practice means weakening of the tooth as this animation can show. I have seen suggestions that it means can't be cut.

**LINK**

Then there is the lantern pinion aspect, A red herring in this discussion but does have it's features.

In practice the various arguments by pundits miss an important point. The curves are both based on zero clearance between mating parts. Involute are reckoned to be better in that respect and do offer better performance when there is clearance.

Somewhere at the back of my mind is the pressure on the shaft carrying the gear aspect. Mentioned some where long ago and forgotten so can't remember how that went but suspect involute won but then comes the tooth count problem.

Interesting comment on shadow graphs on the site. He doesn't seem to have used on that is so big it's been built into a room so people sort of actually go into it.

There seems to be little on the web concerning cycloid gears other than this which is using them for another reason.

**LINK**

John

-

.

Lantern pinions are to be greatly admired ... and hardly a 'red herring'.

MichaelG.

Michael G – I truly appreciate your help.

Although I haven’t read the whole article or tried to come to terms with the mathematics, I was feeling pretty smug when I read the paragraph in Hugh Sparks’ gear design article –

**LINK**

i.e. Friction: - where his sentence begins - Because some sliding contact occurs in all gear designs,

It was a ``Phew! moment for me.

Then I read the fourth paragraph under the heading The Goal where he says …

perfect rolling action is only possible in cycloidal gearing when the pinion has ten or more leaves.

Now I’m even more confused.

I then watched the animation … **LINK** where it is clear to me that sliding is taking place.

I suppose I should study more closely, the various loci methods along with their positive and negative attributes!?

Could you imagine Jim C, that your thread would cause an old codger like me to end up with his `wellies’ stuck in the mud?

Sam

The trouble is that you can't easily make perfect cycloidal tooth forms, they are generally approximations using circular arcs. I'm not even sure that anyone knows how big the errors are. Involute gears can be generated by hobbing so they can be more accurate. They also work when the depthing is too big.

On the question of undercut, one way to avoid this is to use non standard pressure angles when you need a low tooth count pinion, if you are making your own cutter. For a given tooth count to can calculate a pressure angle that just avoids the undercut. Once I get my computer back I'll try to remind myself how it's done.

I don't think the undercut would matter in a clock John H. Power transmission yes. I have come across comments suggesting that undercut means that they can't be cut with conventional cutter rather meaning thinning at the roots which is what it generally means.

The csparks site is unusual as it mentions that there are standards that involve departures from the ideal and are compromises. Actually I think this also applies to hobs.

I'd also say beware of the web. As time goes on there is more and more need to check what can be found on it.

John

-

.

Roy,

I can explain:

John Reynolds' series was also published in the Horological Journal [ahead of the EiM], and is now complete. The clock does indeed have a seconds pendulum; 60 teeth on the escape wheel; and a Brocot escapement ... which do combine to give a 120 second rotation of the seconds hand.

When you get to Part_9 you will see the dial design.

MichaelG.

Just my input to the OP original question.

I attempted Colin Thorne's Skeleton Clock but when I was young with no machining experience let alone an understanding of clock mechanics. I did have his book on clock making for the model engineer which is excellent however, it was not good enough to allow me to build the clock from scratch with my limited understanding. Basically, I ended up with a set of plans and book - it just wasn`t clear enough! I`m in no doubt some of this was my lack of skill and inability but as a "first clock" - it was too hard for me on too many counts. Mainly the lack of any written text to follow with the plans at that stage of my understanding of clock making.

I own a large collection of John Wilding's books and have read over these. Now I`m not necessarily keen on the clock designs but the books are excellent and match the machining techniques clearly. The same with John Parslows Skeleton Clock which is another exceptional clock and build.

As it happens, 5 years after failing with Colin Thorne`s clock (due to my age and lack of knowledge and understanding) I picked up John Wilding`s - Dr Woodwards Gearless Clock. This has already been mentioned and I must admit, although it was my first clock and another user has mentioned it in this post, I would NOT choose it for a first clock if I had the option again. The number of emails I get with people saying they can`t get their clock to run is incredible and to be honest, I struggled like hell to get mine to run reliably and made many modifications from the original plans. I contacted John Wilding but he no longer makes modifications and edits to his books but I did get a kind reply back.

I`d personally go with one of John Wilding's other clocks or John Parslow`s Skeleton Clock - all have good written instructions and explanations and there are plenty of people who have built them. Just my advice based on the stack of clock making books and plans I have.... good luck and which ever you go for, I am sure you will enjoy building!

I have never made a time piece in my life but would like to combine my other hobby of astronomy with metalworking and make a mechanical sidereal clock. Is it as simple as making the hour hand go round once/24 hours instead of twice? (and timing it to the sidereal day) or am I kidding myself?

.

Essentially ... YES

MichaelG.

Curiously Jim (C),

Mark Frank and Buchanan have been working on the sidereal and solar sections of their masterpiece quite recently, see links. However the mathematics may be buried somewhere earlier in their notes.

If you haven't been to this site before, be prepared for a sobering experience. I go there when my ego needs to be brought down more than a peg or two.

It's worth a visit anyway.

Regards,

Sam

http://www.my-time-machines.net/astro_01-16.htm

http://www.my-time-machines.net/astro_02-16.htm