Casting Windmill Parts from Original Cast Parts. Celastic for Adding Draft

Discussion in 'Sand Casting' started by Melterskelter, Jul 12, 2020.

  1. Ed is restoring a hundred-year-old windmill and needed some parts cast. He had originals from a similar windmill motor to use as patterns and just needed duplicates of those parts. The total weight of the parts was about 10 pounds. Sounds easy enough, right? I mean the originals were castings, obviously, so, you would expect that with just some cleanup and painting they would be good patterns with proper draft and shape and then could be simply packed up into a mold and away we go. That proved not to be the case. I suspect that they must have been heavily ground by the manufacturer after casting to make them look better and perhaps to remove some surface defects.

    First off, the two larger and more complex parts were broken in shipping. That's not so bad for me (Ed was pretty bummed) as the pieces could easily be glued with Cyano glue and once again should make usable patterns. I chose cyano glue as the glue drying time is so fast and it is quite strong. Plus the parts could be hand held in proper position feeling the grains interlock when they were just right. Epoxy glues being thicker and slower would have made it harder to feel the messing of the fine grain. I just held the pieces in position and my sweet wife dribbled some glue into the crack and then spritzed the glueline with kicker. Voila! That was easy. Part1.jpg Part2.jpg

    The original Ed had were pretty rough when he got them and the one piece had four fingers of iron that looked tricky to mold. He had cleaned up the parts by sandblasting them, filled in the space between the fingers with two-part filler and applied filler to the major pitting to smooth up the parts.

    Then the fun began. I started looking for dings and pits, filling them with bondo. Part3.JPG Part4.JPG Part5.JPG



    Part21.JPG Part7.JPG
    You can see where I added almost 1/4" of light green bondo to this area of the "rake." I also had to relieve the other side 1/16" to zero over 3/8 inches to allow parting this portion of the rake.
    Part8.JPG

    Here is an assortment of parts Ed sent. I spray my patterns with white lacquer as it really helps me see defects in the pattern surface. Flat and transparent sprays tend to not aid in seeing defects.
    Part9.JPG
    Here is the part line for the rake.
    Part10.JPG
    See the relief on the outside of the rake.
    Part11.JPG
    Part12.JPG Part13.JPG part14.JPG Part15.JPG
    Here I have drawn on a part line that I will use for coping down on the pattern. This part is somewhat complicated with respect to establishing a parting line. You can see I used my pattern-maker's square all over the part. I had to add back the draft in nearly all areas.
    Part16.JPG

    Ed provided a core box and made a core print in the piece where there is supposed to be a rectangular depression in the part. The lined area is where the core will go. Its design is somewhat atypical in that the core will need to be pinned into the mold using 2 4" pieces of tig filler wire. The cores are made with sodium silicate, coal, sugar, and 100 mesh olivine. The boxes had no draft in the straight inside portions. So, getting the core out without breaking it was touchy business. There was lots of draft on the reference surface of the boxes.
    Part17.JPG
    Part19.JPG Part22.JPG Part23.JPG
    Ready to mold, or so I thought. But this part had one more trick up its sleeve. Where the long arm of this wishbone meets the main portion of the part two surfaces had draft to the part line but those two surfaces actually diverge. I learned that a couple hours ago when I rammed up a mold with the part in this orientation in the cope as I rammed it up. When I went to draw the pattern, the sand insisted on fracturing right at the point where the longest side of the long arm met the part line. Little did I realize that because the part was actually of greater dimension an inch and a half down into the sand than it is at the p[art line---the counter in this case.
    Part24.JPG

    So, here is where I got tripped up. I have some Celastic coming tomorrow that was supposed to be here on Wed of last week. I will use it to add draft to the pattern so that it can be drawn more easily on the next molding session.
    Part25.JPG
    Drawing that long arm out of the sand required my concentration!

    Tomorrow I will mold the rake and the little rectangular box both of which use cores.

    BTW, I love that little Starrett square. It is so hand for this kind of work. When someone gave me one many years ago and well before my interest in casting, I wondered about it utility. Now I get it.

    Denis

    These parts look pretty simple at first glance. But, I am learning they are actually quite complex.
     

    Attached Files:

    Last edited: Jul 12, 2020
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  2. It's certainly an interesting topic: one of the guys who got me interested in foundry work learnt his trade at the Toowoomba Foundry where Southern Cross windmills were made in Australia (and exported to South Africa) from the 1870's onwards. Laurie the engineer who built the furnace in the foundry where I help out at, did his trade at the Toowooma Foundry. His brother Wally was the general manager there for years and is still alive although in his 90's now. The Southern Cross irrigation business was sold and then the family that owned the foundry sold it to a larger concern in 1987 before it closed in 2012.
     
  3. Mister ED

    Mister ED Silver

    Mark, Southern Cross mills are pretty cool with some unique features ... and still made today.

    The windmills I am working on are IXL brand. The interesting thing is that there was an IXL windmill in the states (Phelps and Bigelow Co) 1880 - 1920 and Australia had an IXL brand as well made by the Fortesue Co. 1910-1940's. Absolutely nothing similar between the two brands except the name, and the sometimes very similar letters/symbols I*X*L on the vanes (tails).

    Denis is right, seeing those parts broken really got me down (my fault, I should have wrapped them better). And then I feel real guilty that Denis had to add draft in a bunch of places. When cleaning them up, I just figured that they came out of sand once ... they should come out again, LOL.

    But on the good side, these two mills are really cool and worth the work. Made 120 miles down the road, probably 1890-1910. One is a back geared mill (hmmm ... there could be another thread right there:)) and the other is a direct stroke version (no gear). The IXL backgeared mill is pretty uncommon to find ... somewhat rare. The IXL direct stroke ... uncommon is an understatement, no one in the windmill community knows of another in existence. I have seen online pics of 1 other ... but was unsuccessful in finding the owner.
     
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  4. It should be possible to make a good repair of those broken pieces with silver solder to wick into the narrow cracks and the usual cast iron brazing repair techniques like preheating and burying in sand to cool down. I see IXL still have a foundry in Geelong: http://ixl.com.au/
     
  5. No need to feel guilty, Ed. The idea that these parts were cast some time in the past would seem to require that they have draft. I made the same assumption. And, I suspect they did have adequate draft at one time. For reasons that make no sense to me they had to have been deeply ground at some point after they were cast.

    Looking at the bottom of the wishbone I can see that the shape could have been and, likely, was symmetric in the pattern but later was ground away. Was there some casting defect there? Evidently we will never know unless you get extremely lucky and are able to compare the same part on another motor.

    I did get the Celastic LT today. It is interesting material. According to the guy that sold it to me at Atlas it is a combination of a nylon matrix into which a "polymer" has be injected or woven. the nylon is unaffected by solvents but the polymer partially liquifies when exposed to acetone or MEK. The texture when dry of the Celastic is similar to the pasteboard backing on a common pad of notepaper. After soaking the recommended 30 secs in acetone it becomes softer and more flexible and mildly sticky. That is when you mold it into place. It pretty well stays where you put it following gently curving surface and compound curves. I was able to lay up six layers of of Celastic LT in less than ten minutes just freehand cutting strips and padding them into place. 4 hours later essentially all the acetone has evaporated as the material is click hard and there is only a faint odor of acetone with it right under your nose. I think I will leave it overnight and then just dribble on some water-thin cyano glue to permeate the whole thing and make it even stronger and rock hard. I am not sure that it actually needs the cyano treatment, by the way. Then out comes the sanding disc on my Foredom and hand files to contour it as needed. So far, I am quite impressed that the Celastic LT is quite easy to work with. Earlier today I used it to provide some draft on the rake piece where the rectangular recess gets a core and it adhered well on its own, sanded well with the Foredom right down to a feather edge. After sanding it was just a bit fuzzy, but after a coat of lacquer, that disappeared with light 220 grit sanding.

    I think it is worthwhile to be careful from whom you buy it. The guy at Atlas said they have theirs formulated to their specs. You will see on YouTube that some folks complain that laminations of material they have bought will not adhere to each other. When I was buying this stuff I asked the salesman about that. He correctly reassured me theirs does stick to itself and also advised me that prolonged immersion in solvent is not advantageous. (So YouTubers advocate prolonged soaking.) I see they also list Celastic XT which may not be self-adhering.

    I am sorry if I am belaboring this draft issue, but on looking a bit more at the part and visualizing it being drawn, I think the angle that determines ability to draw is determined by the long side of the wishbone arm, not the short side as I previously stated. That angle is a few degrees less than the short side seen as the right side in the photos below. It does make some difference meaning that the material to be added needs a few less degrees and therefore less layers.

    Draft.JPG Draft2.JPG

    Here are a couple pics of the layup.

    Celastic1.JPG Celastic2.JPG Celastic3.JPG

    The stuff is so hard I can not press my thumbnail into it. Feels like plastic.

    I think this layup was so much quicker and easier than trying to get a thick layer of Bondo on there.

    This came as a large sheet about 30" by 50" and cost roughly 40 bucks. It comes in many thicknesses to 2.0 mm. I got 1.5. I suspect that will fulfill my needs for the foreseeable future.
    https://www.atlasortho.com/Celastic-LT_p_1476.html

    Denis
     
  6. Progress report: This morning I went out to the shop and faired up the added-on Celastic. It behaves a lot like a medium hardness wood that has no grain. I used my Foredom with a small cylindrical carbide bur and a half-round medium file to smooth it and blend it into the piece. It took only about 15 minutes to get it ready for the next step which I think should be application of Bondo to fill in a few minor voids. To achieve adequate hardness, the material needs no added cyano glue which last night I thought I might want to add.

    564D95CD-A3DC-4412-BC8B-2C6CB1F9C5CE.jpeg 35722845-63B6-4672-9069-4A7BC2CFF8EC.jpeg B6A61BFE-5E5C-4487-94A7-86D1685E8FF2.jpeg

    Added: DA0FDF43-36A1-44C5-B551-E4975C30AAC5.jpeg
     
    Last edited: Jul 14, 2020
  7. Mister ED

    Mister ED Silver

    That stuff is pretty cool Denis. I can imagine using it just building up an even thickness on a part/surface ... easy peasy. I always have trouble just putting filler on a surface and trying to sand it smooth and even so that you are leaving 1/16 or 1/8 on the entire surface.

    Heck, on that part ... a little reinforcement right there will be a good thing. If I remember correctly, that is where the old cast iron weld was.
     
  8. HT1

    HT1 Silver

    Dont beat your head too Much, that part may not have actually had proper draft, and may have been formed using specialised cores, like kiss cores or ram-up cores , there are some serious advanced ( Now old School techniques ) that allowed parts to be made with extra detail, which was often backdraft. or to limit cleanup


    V/r HT1
     
  9. Oh, there was a weld there! That might explain some heavy grinding in that area. Starting to make sense, now. Sanded and filed the Bondo and hit it with a coat of shellac to reduce fuzz.

    19E9D24B-3427-4CFE-B44F-8509AFB72681.jpeg 7AF4D3A3-D96D-435E-AFC4-013470018C57.jpeg 43EFE249-6DA0-466D-ADD2-1A71A4E6D957.jpeg
     
  10. Billy Elmore

    Billy Elmore Silver

    We use Tuffill for fillets on every pattern and building up worn or damaged parts. Only use it for short runs as build up as our machines will blast it away rather quickly, but on the old hand floor we used it all the time and it held up very well. You can feather edge it and work it very well too. I found that it builds up nice and have made some layers over a half inch thick at a time. Cure time is around ten to twenty minutes depending on the weather.
     
  11. Billy, I looked up Tuffill and it looks like this is a company that makes many products that have the first name TUFFILL but then numbers after that to indicate which product one is actually looking at. They say that they are thermoplastics if I get it right and that makes me wonder how they’re used do you have any notes on that? How applicable is it in the home foundry set up? Are they something like hot glue?

    Denis
     
    Last edited: Jul 14, 2020
  12. I looked for more info on Tuffill and found that Freeman makes a line of Tuf-Fil products that, like Bondo, uses a polyester base and then adds various fillers to provide a range of material hardness from something like pine to mahogany and a high temp application as well. https://www.freemansupply.com/video/products/tuf.htm

    Incidentally, I have been modifying Bondo viscosity some for various applications. It naturally tends to lose some It’s polyester base over time and becomes thicker. To overcome that, I add back some polyester resin (laminating resin available in hardware stores) to get it back to original thickness. A paint stirrer in my drill motor works well for mixing. Of late I have been thinning it in small batches further to make a final skim coat that flows like a good quality latex paint. That saves a lot of sanding and smoothies out to a very thin feather edge.

    Here is the padded out area that will get one more sanding prior to final application of lacquer. It is probably workable as is. But one more hit takes only a couple minutes.
    image.jpg

    image.jpg

    Denis
     

    Attached Files:

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  13. rocco

    rocco Silver

    I do the same. I learned that trick from an old body man.
     
  14. Billy Elmore

    Billy Elmore Silver

    Looks good!
    Yup...Freeman product. It is two part...just like bondo. I have only used bondo a hand full of times and it did not do so well for me. Possibly because I had already began using Tuffill and did not do it correctly. It is very simple to use but is very sensitive to heat...if it is hot in the workshop you will need to do small batches as it will set up very fast. In the cold winter months you may have to wait a little while or apply heat to get it fully hardened. Do not know the cost of it now but it used to be relatively cheap. Looks like you got it right from the pics and may not want to change your process but for us it is much faster and easier. Just saw one of my guys build up the whole side of a runner with it....which will not last in our process and he knows this.LOL
     
  15. HT1

    HT1 Silver

    question that may not have an answer "here"
    I'm sensative to something in bondo! makes me pee blood, so pretty serious.
    is this product something I might be able to work with???

    BTW I currently use Durhams or plaster, both are brittle compared to Bondo


    Thanks in advance

    V/r HT1
     

  16. Thanks, Billy. Which of the various formulations do you use?

    For something tougher than the Bondo /Tuf-Fil filled polyester resin products, you might want to look at the Celastic LT. Because it is fiber-reinforced it resembles fiberglass in fracture resistance. That said, if I had a long runner to pad, I would definitely consider using 1” glass tape (bigger or smaller if needed) and laminate it with polyester resin. As you may know, the cure rate is very controllable by varying the amount of catalyst added. Anything from 5 mins to a half hour. For thick layups excess heat has to be guarded against. But the result is mighty tough and has great tensile strength and elasticity. Bondo and Tuf-Fil are simply polyester resins with powder rather than fiber in them.

    Denis
     
  17. rocco

    rocco Silver

    Glass fiber reinforced bondo is widely available however, it's not quite as nice to work with.
     
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  18. Yesterday I fired up the furnace (at long last) and poured the wishbone and rake patterns. I batted .500. Unfortunately, the wishbone had a shrink defect in its long arm and located adjacent to the riser. But, the rake came out quite well yes, I could have done a bit cleaner job of coping down, but it will clean up easily. And I think I know the fix for the shrink defect.

    Ed included a core print in the rake with a corresponding core box for the rake. Technically, I think the print and core could have been omitted, but they were there and I wanted to try them using a pinning technique for securing the core in the print. To pin it in place, after making the core with sugar, sodium silicate, coal, and 100 mesh olivine, I drilled it with two diverging 1/16” holes. The I dropped it into the print and used two 4” long tig wire each with a kink in the end to secure the core. The wires held the core securely with no wiggle. And after the pour the core broke down easily and scraped out with just a few pushes of a screwdriver.

    The wishbone filled nicely but I had not counted on the mid shaft of the long arm freezing last and developing a shrink defect. In retrospect, the generous riser in close proximity to the arm along with the large pouring basin ( with tumblehome BTW) overlying the arm resulted in a lot heat concentrated in that region. Next time the riser will go on the short arm side. That way the confluence of the arms where there is the most mass should freeze off last. That was the area I was worried might have a vacuum defect on yesterday’s pour.


    I’ll be pouring the rake again as Ed wants two sets and the wishbone will get poured twice—-hopefully those two pours will provide good parts.

    Coping down and core partially pinned
    1D2946F2-33C9-440B-A21A-55F8911F0E20.jpeg

    pinned with blind riser Pattern base seen to right.
    4D87ECA6-5323-49A3-8AB7-884EBD810C6F.jpeg

    Bent stubs of tig wire shown
    D211EC30-7F28-40EC-8A96-70B974404E20.jpeg
    The aftermath with core dumped out but wire incorporated into the iron
    AA062890-EEB4-41B2-99BE-7C519804B1B7.jpeg
    Bottom of the rake showing pouring basin, runner, riser and some flash where I coped down too far and cope sand fracture due to undercut. Learning...
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    Shrink defect adjacent to collapsed area of riser on wishbone both indicating location of hottest area.
    0E61B08F-E994-42F3-A637-EFC5F46CA487.jpeg 14258774-7478-4C15-976C-912D48ECD35F.jpeg 18049378-5A47-4F8E-9CE0-2EEEDC948D16.jpeg
    Long arm is up in this picture. See all the iron concentrated on that side.
    D65CA10C-8A76-47B2-B2EC-2F4C0ADD0EEC.jpeg

    Denis
     
    Last edited: Jul 15, 2020
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  19. Billy Elmore

    Billy Elmore Silver

    I honestly could not tell you but we do have a guy in the shop that says bondo messes with him and he has no issues using Tuffill. I do not know to what extent messes with him means but I will ask and see if it is a similar situation. I think you would like it better if you can use it. It works really well and is not so brittle. You can mix it with more or less hardener and effect the rigidity of it...too much hardener makes it spongy and soft and too little will make it harder...but will take much longer to cure. After you get used to it you can mix it to the ratio you feel will work best for whatever you are doing. We switched to some other type of plastic once before...I think it was BBC or something along that line and it was awful...would have hard and soft spots and would crumble as you sanded it. It lasted til the first can was gone and we never ordered it again.
     
  20. Billy Elmore

    Billy Elmore Silver

    On a hand floor or loose piece molding I could see a real benefit to that. It has no real application for us here though...currently. We dont typically do jobs with any type of large build up material. Our patterns have to withstand years of abuse. We have tooling still in use that was made in the 70's. We counted molds on one shallow job (9OG griddle) and stopped counting after 1.5 million molds. Still use it today and that was about 15 years ago. Those flat pans will last forever. The deeper pots and such will not last but a couple of hundred thousand molds. We are currently beginning to have our gating machined from tool steel. We have implemented tool steel gating with fillets and such built into the gating so no maintenance is required. I am in a new process now of having them 3D printed out of plastic first and then being converted to tool steel after they are proven out in foundry. We will be looking at purchasing a 3D printer if this proves to be successful. I am also considering a metal printer or a sand printer. We will probably just go with the cheapest first until we see a real cost savings to anything else. Sorry I strayed from the topic and am rather chatty this morning.LOL
     

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