Gear forms

[MuellerNick]

I just wanted to add a few things:
Gears in clocks don't run that fast. Or do you call 2 revolutions per day fast? They also do not change direction, so noise is no concern. In the old days, they had no cliue about gear shapes, but the clocks still worked. No speed, no load, just a merry go round. They even filed the gears and they worked. Crude gears but intelligent mechanics.

So keep it simple. It is no rocket nor a F1 gear box.

Nick
And a happy new year!

 

[don-tucker]

This is the results after all the help I had from this forum

Pleased with them and glad to get them done a bit tedious.
Another couple of months should see the clock finished then my next project ,an overcrank twin clinder job.
Don

 

[chipenter]

for cycloidal cutters I would use indexable TCT tips if the radius matches .

View attachment gear cutters.pdf

 

[chipenter]

Just did a search and found this .
http://www.hessmer.org/blog/2012/01/28/cycloidal-gear-builder/

 

[Simon0362]

Don,
I have a strong suspicion that we are building the same clock....

For reference (since you seem to have made a perfect set of wheels) and for others searching, my method is as follows which uses the tools that I have available:

• Download GearBuilder - this allows any wheel/pinion to be modelled and subsequently saved as a STL (??) file.

• Download Inkscape, use it to open the Gearbuilder file and save as a .dxf file

• Open the .dxf file in your favourite CAD

GearBuilder lets you define the number of teeth and the module and in tuyrn draws a cycloidal gear as well as a lot of useful information including tooth height and all of the pitch diameters.
I drew my 96 tooth wheel, opened the file in CamBam and deleted everything apart from a single gap between 2 teeth. this was then set as the lathe profile and a G-code file developed.
I have recently bought an Emco Compact 5PC CNC lathe so I used the G-code file to machine the profile on a 25mm silver steel blank. This was then transferred to the 4th axis on my CNC mill and 16 slots cut followed by another 16 cuts to generate cutter teeth. No attempt was made to create any relief - life is too short!

After that, it was a case of standard silver steel hardening and a pale straw tempering on the teeth.

I did 6 cutters as a batch - for the 96, 50 wheels, 2 more for the pinions (which I have not used yet) and another 2 for the ratchet wheel and the escape wheel.
The big wheels worked perfectly on attempt #2. Version 1 presented one of those really silly errors that happen from time to time - I built the 4th axis and had trouble calculating the steps per degree and eventually entered approximate values until I found the correct one - roughly 17.7 steps per degree. Irritatingly, I forget to set it to the precise 17.77777.. so my 1st version of a 96 tooth wheel had 95 perfectly cut and spaced teeth...and one less than perfect tooth rather larger than all of the rest. Enter one scrap wheel for test purposes...!

Good luck - I have made the frames, the pillars and all of the main wheels apart from the ratchet which is being a pig at the moment. The pinions are next which may be more of a challenge.

Simon

 

[don-tucker]

Simon
It is the Parslow skeleton clock,it is coming on quite well with gears pinions frames ,gears ,spring drum and dial plate done.
Why is the ratchet giving you problems.
Don
PS Hope you didn't cheat and use a cnc for the frames

 

[Simon0362]

Don,

Yes, as I suspected - as serialised in Model Engineer several years ago.

I have so far cut 3 ratchet wheels, the first, I cut too deeply and the next two have not had the wheel tightened sufficiently on the arbor and they have moved ever so slightly during the cutting process - looking at the 45° cutter and its action on the wheel, all the forces are in one direction and this has caused the wheel to slip.
My next attempt will involve the use of Loctite followed by a little heat to remove it - but that will probably have to wait until the weekend.
Frames.....? CNC.....? Me......? Whatever are you thinking of..........

Simon

 

[don-tucker]

Simon,Are you flycutting the ratchet?I did and it came out well.
CNC, come on own up
We will have to keep in touch via email,we don't want to bore all these engine men on here.
Don