Casting a Bearing Cap in Iron

"Treva" on AA contacted me to try to cast a bearing cap for him.

I am not in the foundry business, and only do this as a hobby, but I need some experience with iron castings, so I am going to try to cast this part for him.

Apparently he is big into line shaft driven machines.

As he states, he would make a new pattern for this cap, but he wants to retain the authenticity of the part with the numbers and letters on the top, and so we will try to use the original part for a pattern so we can salvage the numbers/letters.

Obviously we need Treva to join us over here on this forum, not to take anything away from AA, but I don't have access to AA, and I can't see any photos that are posted there, and don't have any way to interact with anyone there.

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Here are some photos of the original piece.

What I would propose to do is glue on some think plywood to the flat sides, and build up the curved top surface with spackling compound.

This approach would allow me to clean up the letters/numbers and salvage them.
All of the holes in the cap would be drilled after the part has been cast.

All the additions could be cleaned off the original part to salvage it as an original piece. although it is not very usable in its broken condition, and the welded repair is not really something I would rely on.





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I think I would just grind off the extra weld material. Epoxy on a piece of wood to replace the missing portion of the ear and ignore the hole in it as it would be easy to bore out later. Probably would fill the other ear hole and the other holes in the journal with epoxy too as the holes just add complexity. Use the resulting part as a pattern and just put it round side up on the table and ram up the cope. Then flip the cope and dig out whatever sand found its way into the journal and ram the drag. Add the needed runner and sprue and give it a go. Runner could fill from the drag through the ear bosses.

Cast it and bore out the holes.

Good luck.

Denis

 

I thought about that, but have never done anything like that, and I am not sure how that would turn out.

Yes, but that would make a casting that is smaller than the original part, and I want a casting that matches the original part dimensions.
Granted the shrinkage amount would be small, but if I am going to go to the trouble of casting it, I want it exactly the same size as the original, and I don't want the holes in the ears to have to be drilled in a non-concentric fashion.

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well, OK, getting the part to come out of the sand exactly on size with no warping and holes of correct size , draft free, and correct location with those thin sections of ear around the hole also pouring correctly sounds really hard to me.

If 40 thou undersize in greatest dimension (estimated as the part looks like it is about 4 inches in greatest dimension) is objectionable, maybe build up the long portions of the part with celastic, pasteboard, Bondo etc and the thin portions (.004 undersize) with a couple coats of spray paint?

I am sure you will be documenting this fully, so it will be interesting to follow this project.

Denis

 

The cap measures 3.43" long, so the pattern would need to be about 3.48" long.

If the cap is used as-is as a pattern, then the casting would probably come out about 3.38" long, if I am doing the math right.

Is that difference enough to matter to most people? Ans: No.
Is that difference enough to matter to me? Ans: Yes, just as a matter of principle, I don't use a part as a pattern without modifying it to allow for shrinkage.

Call me stubborn or whatever, but if I am going to make a replica of a part, it is going to have to measure the same as the original part, using a vernier caliper (vernier calipers are not terribly accurate, but accurate enough to get within any original production tolerances).

As far as the holes, I will fill them with something that is temporary and easily removable, such as spackling compound, so that the part can be cleaned, repaired, and reused if desired.
Most people don't want original parts modified regardless of the condition, since they are often one-of-a-kind pieces, and I understand that and feel the same way.

I should probably try the clay and epoxy thing, just so I can get the feel for it, but the letters are not particularly crisp, and so I don't want to lose any resolution on those.
I have never done any letters of any kind, so my confidence is just not there for me to try and copy the letters for this piece.

In a perfect world, I would put the piece in my 3D scanner, and pull it into Solidworks, then scale it up by 1.015, repair the part, omit the holes, and then print it on my high-resolution 3D printer.
Unfortunately this is not a perfect world, I don't have a scanner or a 3D printer; I make all my patterns by hand using wood and/or steel.

But the hand and eye can be surprisingly accurate with the proper training, and I like learning how to hand-make patterns, and like working with wood and steel.

Its all for fun, and I would not be trying it if I did not enjoy trying to match it exactly as possible.

Probably a couple of layers of card stock on either end, and on the bottom would take care of the shrinkage, along with a little filler on the curved surfaces and the top of the ears.

Edit:
It is possible that I could clean some of the rust/scale from the letters/numbers, and get a clean imprint of them, assuming the clay pulled off without sticking and/or deforming.
I am still contemplating at this point.
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Here are some photos of patterns for a bearing.
These are not my photos, but were publicly posted on ebay.

Gives you an idea of what are probably typical bearing patterns.
Nice self-aligning cap feature.
I am not sure why the patterns did not have core prints on the ends?
Perhaps the core was just laid in the cylindrical recess in the mold?



















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Here is another example.
Photos are not mine (from ebay).

 

I started cleaning up the bearing cap tonight.

Ground off the excess welding and cleaned up the letters/numbers a bit.
Glued on some tongue depressor sticks to give a little shrinkage and machining allowance.
















Traced out the pattern for the broken ear.




Found a piece of wood about the right thickness.




Glued on the wood and added some filler (wall patching compound).
Did the initial rough sanding on the filler.




Filled in the oiler hole.
I will tape over the holes that secure the babbitt in place.
The holes will have to be drilled in the new casting; I don't have a way to cast them in-place.




Added final layer of patching compound, most of which will be sanded off.



The wood and patching compound, wood and glue can all be stripped off if desired, if the old piece is to be salvaged some day.

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Could the core be suspended through the two perpendicular cores ton top via a strong back ?

 

I am only casting the cap, not the entire bearing body, so there is no need for a core.
I will just let the drag sand protrude up into the area where the shaft will be.

Here is an example:

 

Those are probably the core prints so they could go in the drag and position the core. I think this is for two separate castings that will be held together by bolts through the ears, since it would normally have a flat parting line if it were to be cast as one piece. Perhaps a follower, or a match plate that had the core prints mounted.

 

Here is the flask for the line shaft cap.
I started sanding on the filler on the cap and got it somewhat roughed into shape.
I still have more sanding to do, but I am getting there.

 

I agree, they would cast the cap and then the base, otherwise there would be no need to cut the intricate mating surfaces of the two parts.

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Pat,

Peanut gallery comments:

If I understand it correctly, in the above proposed runner layout you are first partially filling the cavity near the sprue and then metal rises to the level of the axle and then flows down into the far side of the cavity, fills it and finally rises to complete filling of the cavity. (In reality, flow rates may be great enough for metal to splash around enough to overrun the center from the start). If the pattern were turned 90 degrees, metal would fill each side of the cavity simultaneously and then rise to meet in the midline and continue until the cavity is full.

I tried filling my 18” prism in a “spillover” fashion with in a 50% failure rate due I think to turbulence. It would seem like rotating your pattern 90 deg to fill from both sides might be better. The drawn layout just might work too. FWIW.

Denis

 

A keen observation indeed, and I did not think about that.

This is sort of a quick and dirty casting, and not much attention to dead end runners and such, but I think it will work.
Back in the day, they did not use dead end runners in production shops, and I am aware of places that cast iron parts by the thousands, so obviously there is more than one way to do it.

I will rotate it.
I think you have a good idea.

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I am getting the mold making stuff re-orgainized (relocated), and set up for mold making.
Things had gotten a bit scattered when I added the portable garage and moved a lot of things out there.

Getting close to making sand molds.
I just need to decide if I want to use a resin-type bound mold, or a sodium silicate bound mold.

Its been raining on and off pretty much every day for the last week or more, and that hampers things.
I need some dry weather over a weekend.
At some point the stars and planets are going to align, and then we are going to have some new iron castings.

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The windmill gear is a bust.

I think I will go ahead and make the mold for the bearing cap, and then cast it and the windmill gear at the same time.

Man its hot in the outer shed.
Thermometer is reading about 92 F.


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