Getting Loose fitting gears

[John T]

Hi Art,
This is probably backwards to what most people want from Gearotic, but here goes!

I make lots of gear combinati ons that if fit of 4" by 5" blocks I call them "Fidgets"  (I was making them years before the spinner fidgets came out)  For most of these Fidgets I can use my deputing gage to get a good "loose" mesh on the gears and they sell well to young and old at a Farmers Market.

One of the Fidgets I have trouble with is a block of gears.  I can make a block of nIne gears without too much trouble, however I'm trying to make a block of 15 and I can't get the meshing predictab ly loose enough that guarantee s that a child can work them.  Currently I'm using the boxing function to give me the arbor spacings and it works, but with cumulativ e errors and wood being what it is the finished product will not turn freely.

Is there a way to increase "backlash" to make them set looser?

[ArtF]

Hi John:

  Gearotic 1 used to move the shafts slightly, but Ive found the math
works better if you simply widen the tooth spacing, that allows a bit of slop in
all direction s.. Just change form 50% to 49% and see the effect in simulatio n.

(Nice looking block..

Art

[John T]

Hi Art,
I did as you suggested and changed the tooth width to 49% - I could not detect any differenc e in the simulatio n (maybe my screen?)  Anyway I changed it to 45% and then I could see a differenc e.  I cut a set of 15 gears and they work really nice and freely.

I took the old binding set and made the centre hole 1/32 bigger and now that one works as well - certainly not as elegant as your solution but it does work.

Here is a photo of the 45% set - kind of wildly coloured but will be a hit at the market.

Thanks for your help

[ArtF]

Hi John:

 >>Anyway I changed it to 45% and then I could see a differenc e.  I cut a set of 15 gears and they work really nice and freely.

  Good to hear. It is not a very sensitive adjustmen t as the additiona l backlash
is a cosine function of the tooth width so its slow to take off as you adjust
downwards in width, but I too find 45% to be about right for such projects
and when I do wooden gears I lower it to at least 47% just for wood swelling
and such over time. Glad to hear it worked out.

Art
 

[Mooselake]

We need a like button for the forum   Looks nice, John!  Is that only a 4x5" block?

Would the same type of project work with eccentric gears?

Kirk

[John T]

Yes the block is 4” by 5.25”.

I haven’t tried the eccentric as a block, so that is a challenge!!

[Mooselake]

I can simulate a 2x2 array with 4 sided gears, 3 sided was a bust.  I need to go back and review the doc videos to relearn how to get shafts exactly where I want them then give it a try with some 1/8" plywood that's sitting here going "Cut me, Cut me"

Kirk

[John T]

If it will simulate then boxing will give you the shafts