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Author Topic: Bevels and Boxing  (Read 138 times)
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rimell
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« on: April 14, 2019, 11:19:50 PM »

I've been trying to design a wooden geared toy.  More as a way to learn Gearotic than anything else.  The idea is to have a box with a crank on the outside that turns and moves some gears.  I would like to have the crank on one side that is connected to a bevel gear inside the box so the gears are 90 degrees from the crank (horizonta l gears, crank on the side).  Since bevel gears are rather difficult to machine on a 3-axis CNC I thought cage gears might be the solution.  It doesn't appear that Gearotic currently supports bevel cage gears (not sure if that's actually a term, just made it up) so I've been trying to come up with a workaroun d.  First I create a bevel gear and pinion on the screen with 30 and 15 teeth respectiv ely.  Then I go to the Cage gear setup and create a wheel with 30 teeth and pinion with 15.  I place the wheel on the same shaft as the bevel wheel right on top of it and then delete the bevel wheel.  Then I go back to the Cage screen and switch the values of the teeth so the wheel now has 15 teeth.  I add this wheel to the shaft of the bevel pinion and then delete the pinion.  At this point Gearotic starts to behave badly with the pins on the pinion gear spreading out across the X axis. The Z axis gets huge and trying to rotate the model does some pretty strange stuff.

Kind of a long winded way of asking if you could add the ability for bevel cage gears.

Some other things I noticed:

1. The boxing routine doesn't seem to create holes for the pinion shaft on bevel gears.  Front and Rear sides have holes, Right and left don't.
2. In one of my test projects I created some spur and logarithm ic gears and then added a bevel wheel and pinion.  The pinion didn't have a shaft.  Tried clicking the, "add shaft" button but didn't seem to work.  If I create the bevel gears first, both gears have shafts.
3. Is there some way to flip bevel gears upside down so the pinion points the other direction?

Thanks,
Rick
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ArtF
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« Reply #1 on: April 15, 2019, 06:17:34 AM »

Hi Rick:

    You can reverse a bevel, once the master is placed, right click it on the project menu
and you can select "Reverse orientati on" which will reverse the normal on that gear. The pinion
will place to the new normal and be reversed direction as well.
    Sorry for the boxing error, I hadn't noticed and its been a long while since I used boxing. Ill
take a look to see what repairs can be done.

  >>Since bevel gears are rather difficult to machine on a 3-axis CNC..

  This has always been the trouble with developme nt of bevels. Their very hard if not near
impossibl e to machine in less than a hobbing machine. Its always been a holdup in their
developme nt. Truthfull y, their hard to make even as a normal 3d stl model for printing
with any accuracy.

  For a "bevel cage gear" were you picturing something like the attached photo? Or
were you picturing something more like a flat plate with pins rising up from it? I to
am trying to come up with a better way of getting 90 degree drive for hobby
projects and built the enclosed recently as a test. Of course any solution for bevels
is a question of how much power and torque they will handle and as yet I have no
real good solution.

  Thx for the note on the shfting of the pinion, I will look into why that can happen
as well.

Art









* ninetydegree.jpg (1472.9 KB, 3096x1741 - viewed 39 times.)
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ArtF
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« Reply #2 on: April 15, 2019, 07:07:56 AM »

Hi Rick:

   The boxing error has been fixed and any bevel holes will show up. This is only useful in this case
if the shaft is 90 degrees to the x, though any angle over 45 degrees will make a hole , but the user would
have to bevel the hole afterward s as the software wont bevel it on creation.

  I will include this in an update in a week or so.

  It turns out for some reason occasiona lly the display of a bevel shaft fails. The gear actually has a shaft
which is why pressing add shaft doesnt work. It knows its already there in terms of database. Shafts
which dont display will still create boxing holes as of next version. I did find that deleting the
bevel pinion and then recreatin g it often then shows the shaft.

Thx
Art
 

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rimell
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« Reply #3 on: April 15, 2019, 10:33:20 AM »

Wow, that was quick.  Thanks for the rapid response.

I found the reverse orientati on for the bevel gear (doh, slaps forehead)

As far as the cage bevel thing goes I have attached a couple of images I found on the web.  I guess they're calling them peg gears.  Since this is just going to be a hand cranked toy it won't be high speed/torque so I would think this kind of gearing would work fine.  I'm going to try cutting out some cage gears later today and see if my method of creating two pegged wheels works.  I'm hoping that with the fix to the boxing routine I might be able to create the box with standard bevel gears and then use the cage gears in the actual assembly.

I have also attached the gth file showing what it looks like when I replace standard bevel gears with cage wheels.  Thought you might like to see what I'm trying to do.

Thanks,
Rick
 


* LanternGears.jpg (45.25 KB, 320x240 - viewed 31 times.)

* PegGears.png (41.18 KB, 200x212 - viewed 30 times.)
* CageBevel.gth (12584.34 KB - downloaded 30 times.)
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