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retep
12-17-2005, 05:13 AM
Well school's over for me until new years so I figure I'm going to try my hand at making some gears. I seem to remember a very simple type of gear used in some clock movements, consisting of a "cage" made of round bars supported between two disks and a pinion consisting of a round disk with round holes cut in the perhiphery. If that description is accurate it sounds like a perfect project to do on my mill, no rotary table required, just some minor CNC stuff to make it go faster. For the life of me though I can't remember what it was called, and dispite a few hours of searching google and what not I can't find any references.

Anyone got any hints on what I'm thinking of? Sure hope so, 'cause I'm worried I'm getting alzheimer's and I'm only 20. http://bbs.homeshopmachinist.net//smile.gif

John Stevenson
12-17-2005, 05:28 AM
Lantern Gears.

http://www.du.edu/~jcalvert/tech/oldgears.htm
or
http://lostbiro.com/Wood/skein_winder.html

I believe Harleys use these at timing gears, sounds like it anyway.

Sir John.

[This message has been edited by John Stevenson (edited 12-17-2005).]

Your Old Dog
12-17-2005, 07:29 AM
David must be busy.

bobbybeef
12-17-2005, 08:01 AM
Yes they are lantern gears but are usually only used in the driven position.Exactly the same principles apply as to toothed wheels.
I might suggest you use the term elementary gear making rather than simple.Best of luck.
bobby.

dicks42000
12-17-2005, 10:18 AM
Sir John & Bobby beat me to it, but yes they're called lantern gears....As stated, usually only used as the driven gear, mostly in clocks, low powered drives or horribly old stuff like windmills.
The stress distrubution in a gear like that is a nightmare. See Ivan Law's book for a bit of an explanation of the geometrey. It'd be cool to see one made on a CNC, though.
I still think making the little index attachment & single-pointing gears on a 6 inch Atlas lathe is simple too. The silly things we do when it gets cold.
Rick

Allmetal
12-17-2005, 11:03 AM
My dad used to repair old clocks and also referred to lantern gears as squirrel cage gears. Bob

barts
12-17-2005, 03:45 PM
Lantern gears are what you see in old Dutch windmills;
the driving gear has wooden pegs (usually some sort of
ultra-hard woold, lignum vitae or the like) that mesh with
similar cylindrical "teeth" in the lantern gear.

Sounds really cool in a stiff breeze, but given the high
amount of velocity change (due to the effective diameter
changing during engagement) these are _low_ speed gears
only.

- Bart

gvasale
12-17-2005, 06:38 PM
properly, they are "lantern pinions" and they work very well for their intended purpose.

larrys
12-17-2005, 08:35 PM
Odd coincidense, Just got Ivan Law's book, Gears and Gear Cutting in the mail today and read about lantern gears. I've seen them in old grist mills, but did'nt know what they were called. Larry

dlsak
12-18-2005, 04:20 PM
Where did you order the book?

larrys
12-18-2005, 07:22 PM
Thru Amazon.com. Larry

Paul Alciatore
12-19-2005, 01:10 AM
Yes, lantern gears. Yes, they should be the driven gear. That works out well in a clock where the spring (clocks used to have springs that had to be wound) was at the slow (hour hand) end of the gear train and drove the faster gears that lead to the minute and second hands and finally to the escapement. The power came from the spring at the slow end of the gear train so the large (slower) gears were the drivers while the smaller, faster (lantern) pinions were driven.

The thing is, clock gears were often cycloid rather than involute shaped. A form of cycloid gear can properly mesh with a lantern pinion. The round pins of a lantern gear do not properly mesh with involute gears of any PA (pressure angle) or pitch. Can it be made to work with an involute gear? Possibly, but only at Very light loads and slow speeds. With any signficant power transmission, the wear will be significant. Also the motion will not be uniform as an involute gear will only have a uniform velocity when properly meshed with another involute gear of the same specs so with any but the slowest speeds, there will be gear noise and also accelerated wear.

Many early gear systems did use this kind of construction. I have seen pictures of grain mills (water or wind powered) that used wooded gears with lantern and pin type construction. They did work. I am sure they needed constant maintenance due to the wear. And they ran dead slow. Just a few RPM or less.

Paul A.

retep
12-19-2005, 12:56 PM
Great info guys! Looks like a simple thing to try would be two "half-latern" gears at a 90-degree angle with round pins on their faces... Very simple, 8 pins each. That'll make a configuration that won;t require a dividing head or rotary table to make.

I'll post some photo's when I'm done.