making a replacement pinion gear

[Alber]

I have a cement mixer and the pinion gear is not what it used to be. It is also very noisy. I know that there are probably better ways to do this but I have an idea that may help people who would not normally even consider cutting a pinion gear. People like me.

My idea is to cast it out of zinc.  I think zinc casting is an ideal next step for people with 3D printers. I have worked out a process that I call lost wax plaster shell casting. I can do it in my kitchen with plaster, sand, and a little fun with fluidized beds.

Once I get the casting that I like I can easily switch to sodium silicate/sand for the shell and make a little carbon arc furnace.

Thanks for reading this and I'm eager to hear what people think.

[tweakie]

Sounds like an excellent project - I shall be following with interest.

Tweakie.

[ArtF]

Ive seen it done at the shows.. Basically, cut the gear 2d from pink insulation foam..glue on another foam chimney
and bury it in sand with chimney level with top of sand. Melt zinc, put on foam, it disappears and the aluminum
(which was used) made a nice cast part in the sand.. foam evaporated....

Art

[Alber]

Yes, Art. Very similar.

I looked for in the forum under bevel gears and the stuff that I found was far more advanced than where I am with Gearotic at this point. Maybe I just searched the wrong terms but I was looking for a very simple example that I could adjust. What is the best place to look for tutorials? I did some searching but a lot of the youtube stuff was either old or too advanced.

I was able to get two bevel gears but I could not figure out how to adjust them the way that I needed.

Sorry to ask simple questions. Normally I would read a lot more before asking but I'm only getting stolen moments. I'm working with a group that is making PPE and designing and testing an innovative idea. If people are interested I could talk a bit about it in some off-topic forum.

Thanks for any help.

[Alber]

Ok so I measured the ring gear it is 66" in circumference and has about 80 teeth ( I will actually count) the pinion has 9 teeth and is about 6" in circumference.

I have attached a screenshot. No idea what to do next. 

[ArtF]

Alber:

  Your next step is to use the "Add to project" for both the master and pinion gears.
This will create 3d representations of them. From there though you hit the problem of how
to make them. The best way is to 3d print them as machining a bevel is near impossible.
 
  You can cast from a 3d print, but an 80 tooth bevel is likely too large for a 3d printer
at 66 inches. Gearotic will basically save the stl of the gears for you , but with bevels its
up to the user to find a machining solution..

Art

[Alber]

Thanks Art. I only need the pinion gear. So I will trya lost wax plaster she'll process that I developed for casting zinc molds for plastic injection molding.

[Alber]

OK, I think that I added them to the project.
-Do I need to do something with linkage?
-On the cement mixer, the teeth on the ring gear are radial, in the same plane, rotated 90 degrees? What angle is that even called and how do I rotate it in that way?
-The pinion also has to rotate so that its shaft is parallel to a spoke of the large gear.
-The pinion gear shaft is not in the same plane as the large gear.
-There are a lot of options under the Circular Gear Module tab like Tooth Form like under Wheel, Pitch Shift, Height Stub, Rack Shift, Under Type (i.e. Spur, ... Bevel)

Sorry to ask so many questions. Is there a better place for me to look for these answers?

Thanks in advance

[ArtF]

Hi Albur:

  What you have on the screen is a master and pinion spur gears. When the shafts exist at 90 degrees to each
other you use a bevel gear. Its a selection on the gears tab. When in bevel gear mode the shafts will mate at an angle to each other. In your case that angle is 90 degrees.

BUT, and its a big but. By your description what you have is a machine that has an unconventional
gearing. They have made circular tooth forms sticking upwards around a circle on the large ring
and then the pinion is a normal looking gear, flat in 2d, but with circular teeth? Is that the
scenario you face? Can you take a photo and tell me what your trying to make as replacement
in it?

  A non standard tooth form isn't easy to make but its doable, be easier if I could see what you have
and what your up against.. It sounds more like your dealing with a crown gear of some sort and
Gearotic doesn't make crowns as they some in too many varieties and each have their own
limitations.

Art

[Alber]

Art thanks for your time and help. I have attached some photos.

This is the back end of the cement mixer.https://photos.app.goo.gl/nxUv8bf2MtiSb2sL7

A closer look https://photos.app.goo.gl/FZJ4bTSXZfMJyGdL8

The profile of the teeth on the large gear https://photos.app.goo.gl/AeqqvqWzU3uuJ1yo7

The small gear held near where it goes https://photos.app.goo.gl/AeqqvqWzU3uuJ1yo7

Where it goes. https://photos.app.goo.gl/v4msMeddm2fxQ7Qo6

Some teeth on the small gear are very worn down. Almost to a point.https://photos.app.goo.gl/v4msMeddm2fxQ7Qo6

On the opposite side, they are only slightly worn. https://photos.app.goo.gl/JSV5TrXrjWraVU3t8I don't know if this is an indication of some sort of misalignment or just a case of once it starts in one spot that spot gets to the brunt of the wear.

It makes a lot of clanking noise when it runs. I figured that I would find a broken race or broken ball bearings but it looks like there are only bushings. Kinda makes sense. It never gets going very fast.

I hope the pictures help and thanks for any help.