Casting a windmill gear in grey iron

Ok, I'm back from California. Sorry I did not reply, it was a very busy week.

ESC - Those look very nice. One question though, how are you registering the 2 (or 3) parts?

 

I'll use the assembled patterns, then drill register holes with a carbide drill. I can use wooden dowels since the mold will be put together with core paste.
I had originally cut register divots, but the rings were so flexible that the core half of the mold changed shape when separated.

 

OK, someone had asked to see a pic of the driven gear on the windmill. I was out putting things together today and actually remembered to snap a pic. I am still waiting on a couple castings to come back from Tomahawk Foundry (I had another guy send his original parts). Still have to make a couple linkages and put key ways for all 4 gears and the hub.
Looking from one side. The pinions go roughly between the Deykem lines.
View quartering from the front. The wheel goes on the cone shaped hub, to the left of the pic below.

Another pic from the front, a little more straight on (looking through the wheel, if it were on). The shaft for the small gears (first pic) runs all the way thru the end of the hub.

 

I am starting a separate thread on heating a PLA pattern to facilitate removal from a sodium silicate mold. My rationale for doing so is in the preamble to that thread and won't be repeated here [it wasn't that great the first time! ;-) ]

Here is a video from that thread just to give you an idea:


http://forums.thehomefoundry.org/in...itate-removal-from-sodium-silicate-molds.808/

The pattern bits that were roasted to look like a SMORE candidate was a previously heated and thus non-usable pattern supplied by MrEd.

Denis

 

Well, I veered off into the other thread while specifically working on a melt-out of PLA from silicate. But I think I should post here that I poured the mold today. I appeared to pour well as the amount of iron left over indicates the mold filled with an apropriate amount of metal. But did it fill all the nooks and crannies and are there shrink defects, big sand boogers, or incomplete filling of gear teeth. I guess I will have to wait til tomorrow AM to find out. Comlicating things a bit I had a couple of non-foundry guys out to watch. Nice to have friends around but can be distracting. Maybe they got some good video. Don't know.

Anyway, I'll be posting results tomorrow AM. Fingers and toes crossed...

A few pics:


For size reference the srue is 5/8" diameter.

 

I puled the casting out of the sand today. The results are as good as I could hope for.



Well, there you have it. these results are better than I was able to get with green sand casting this pattern.

Denis

 

Wow, congrats Denis, That gear looks really good.

 

One of my friends got a good video of the pour and the other provided a helpful assist as I forgot to open the retaining clip on the trolley before I began transferring the the crucible to the trolley.



It looks to me like it took about 6 or 7 seconds for the mold to fill. I poured a bit longer than that, but part of that was filling up the (overly large) pouring basin.

Denis

 

Awesome pour. Is that the noise suppressor on your furnace for your crabby neighbors? Is that crucible getting thin the more you use it?

 

Thank you, Jason.

The muffler is, indeed, for the “noise-sensitive” neighbor. Given the choice, I would not have it on the furnace, however, I do like the decreased general noise.

Yes, the crucible has decreased in thickness, they always do in my experience. It is good for quite a few more melts, though.

Denis

 

Those tongs and lifting mechanism are pretty slick!!

 

Thanks.

They have worked very reliably and conveniently. I like being able to safely lift the crucible out of the furnace solo.

Denis

 

Very nice Denis!!

 

Here are a couple of vids of the gear on my lathe. I am just making some initial cuts that are pretty well concentric with the gear teeth. I was able to get them to be within .008" or so of running true measuring from their as-machined surface. So there was minimal deformation of the gear as cast.

This video is a brief shot of me turning down the gate which I am leaving in place as I think it will be convenient as a work holding featrure when Ed does the final machining.


Here is the gear spinning on the lathe in Slo-Mo if it will come across that way here. It may not as I have had problems with slo-mo playback here previously. In any event it will indicate just how nicely this gear will run after machining as it is pretty good right now.


Adding a few pics.




I think it is time now for me to put these in a box and send them to Ed. If he is patient and wants to do so, I think he can tweak them in a bit more on his four-jaw chuck using some shims. That might be guilding the lily, though.

Denis

 

The gears from Denis arrived today, and all I can say is that the pics don't do them justice.

 

Did he send you the bill with them?

 

I emptied the box very carefully, I did not see anyone named Bill in it.

 

Impressive molding work/gear castings by all.
That is a tricky thing to cast for sure.
Very nice.
.

 

I owe you guys some pics and an update on these gears. Denis already posted some pics of the gear on his lathe, so I will not show them on mine. I machined the first gear on the vertical mill with an involute gear cutter (missed getting pic) and all went OK. I couldn't get quite as low rpm as I wanted, but since I was really just cleaning up (not hogging out) it worked.

Over the course of the last three weeks I ended up picking up a Rockwell horizontal mill, so I cleaned up the second gear on that machine. The increased rigidity and slower rpm was readily noticeable.


And here is a pic of both gears in place on the mill (not sure why the pic will only go sideways):


I will have to remember to take a pic of the gears themselves, after I break the mill down again. They work very nicely and mesh very well with the bull gears. Keep in mind that I reversed the bull gears and will be running on the (nearly) unworn side of each bull gear.

Things I learned:

• Was it worth casting the blank, vs hogging the gear from a solid mass? I think so, certainly saved on time to cut the gear to final dimensions ... not to mention increasing the life of a high dollar cutter.
• Because this was a gear with an odd number of teeth, it was a pain to measure and turn the OD to proper diameter. With a solid blank you would turn the cylinder to size first. (no DRO on my lathe)
• Aligning the dividing head, cutter and gear was a bit of trial and error, basically it was "get it the best you can".
• If I were to do this again, I would add more machining allowance ... even a bit more than the last pattern that Denis used.

I really have to thank (in no order) Pat, Denis, Andy, David, and everyone else that attempted and or contributed to this thread. I imagine that almost anyone reading this thread could learn something from the ideas and techniques that everyone shared.