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retep
12-29-2005, 02:22 AM
I asked for some help with latern gears awhile back... Well, that help went to good use:

http://petertodd.ca/persist/2005-12-29/latern_gear.jpg

Pretty simple really. The pins are stuff I got from Active Surplus in Toronto. Not totally sure what they are, the look chome plated. In any case they measure almost exactly 3/32, .0937 Of course, my micrometer only measures to the tenth so... They stay in their holes by means of a press fit. A rather tricky operation since the closest thing I could get was a #42 drill, 0.09375... The next best I could do was a #43, but that was far too small at 0.0890 I experimented a bit and found that if I drilled my holes carefully, with lots of cutting oil, the drill was actually accurate! The top 1/8th of material was bellmouthed and the pins fit loosely, but the rest of my half inch long holes was fine fine and made for a nice light press fit. I was able to get two good sets of gears from each blank that I drilled by slicing it into sections on the lathe.

In testing I found the gears to work reasonably well, the spacing may be a little narrow, if they are any more than just touching the tops to each other they get caught up due to interferance, but otherwise they work well and run freely. For testing I just used my lathe as a jig, one on a spindle held in the chuck, one sitting on the cross-slide with an improvised vertical spindle. Good enough for a test.

One thing I should do is figure out what the equations are so I can calculate the path of the pins as they rotate and at what pitch/distance do they interfere. Fun bit of geometry that... (shudder)

[This message has been edited by retep (edited 12-29-2005).]

m_kilde
12-29-2005, 03:53 AM
Nice looking gears
Can't wait to see what machinery you will put it in, do send pics. when you get that far



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Mogens Kilde
www.wallenderengineering.com

Your Old Dog
12-29-2005, 05:13 AM
Interesting looking project and I'll bet you didn't knock that out in 10 minutes !!

Could you remove any interferance by simply grinding the tops off of only one of the gears? I can see in my minds eye how if you exagerated the length of the pins of one gear you could cause interferance so it stands to reason to me that you could eliminate it as well by grinding one of the gears down.

SGW
12-29-2005, 07:52 AM
Here's something I've been wondering about for a while. Would something like that work as an internal gear, mating with a regular spur gear? I'm trying to figure out a way to make a planetary gear set, but the necessary internal gear is a problem. It seems to me that if the pins were of a diameter equal to the mating gear's tooth thickness on the pitch circle, and spaced appropriately, it might work.

Probably the only way to know for sure is to try it.....

japcas
12-29-2005, 12:06 PM
Hey Retep, nice looking work. What kind of mechanism does that go in and how much load can they take? I am guessing light duty.

retep
12-30-2005, 01:26 AM
Well, unfortunately guys these gears are currently being made just to investigate gears. I haven't got a mechanism for them yet, I was originally going to build a little stand for them, but then decided that finally finishing the Z-axis of my CNC conversion for my sherline would be a better use of my time.

Time wise... Er... Actually I almost did knock 'em out in 10 minutes. Probably only spent about 3 hours on the whole thing, design to showing off, but then again, I've got the X and Y axis of my CNC'd sherline to make the drilling much less tedious and the pins were all pre-made. Almost my technique for the design was purely "guess and pray"


The interference could be reduced by grinding yes... However when yout think about it, that's the same as simply moving one gear farther away from the other. Stronger though as the lever arm would be shorter. Still like to do out the math, at least to feel that I really understand the problem.

Internal gear 'eh? Hmm... Well if I work out the math, figuring out how to do that should be simple! I think you'd need a fairly wide ratio so you don't get hung up on interference problems, but I see no reason why it couldn't be done... Nice idea.

Norman Warfield
12-31-2005, 08:19 AM
That's a good looking sample. I have seen these "gears" used on water wheels and windmills for transmitting horizontal rotation into vertical rotation,and also in large clocks.

For lack of knowlage we refered to them as "pin gears". Some of these are still in use at the "amish" country towns in Pennsylvaina.

Interesting... to say the least.



------------------
Norm'
If it's not broken, why do I keep trying to fix it....

pgmrdan
12-31-2005, 12:54 PM
Aren't each of those half of a lantern gear? Or maybe really tall crown gears?

CCWKen
12-31-2005, 08:16 PM
See here: http://www.du.edu/~jcalvert/tech/trochoid.htm

pgmrdan
12-31-2005, 08:25 PM
See here: http://www.du.edu/~jcalvert/tech/oldgears.htm