Tobho's HT1-Inspired Cement Mixer Muller Build

Thanks J, I hope these will work ok. Since you asked, here are detailed pics and expalnations in the form of a video that shows pretty much everything about this upate from patternmaking to finished clamps.

Also included: a look at the furnace.



Jeff

 

Good tip, I'll keep that in mind when I eventually get around to building one...

Thanks again, I think the clamps are gonna work well.

Jeff

 

Nice work Jeff and always like to see tools making tools. I think you owe us a lost foam subforum thread

A couple questions for you. As I recall, you are using glass bead media for mold material. Is that correct? I was looking at those nice big pictures over at AA, and maybe it was the light, but it looked like there may be some mold media on the surface of the castings. Was there? Also, when you demolded, it looked like there was clumping of the mold material. Can you tell if this was break down of the glass bead media or just caused byproducts of vaporizing the foam?

I ask because I've looked at using blasting media for mold material (aluminum oxide in my case) because it is readily available in whatever mesh you might want, but it was always =>$1/lb, and I needed 100lbs of it which didn't sit well compared to free sand and mud. The other thing was I always get sand embedded in my castings when I don't use mud and that wreaks absolute havoc with cutting and machine tools, so even if I could achieve better finishes with abrasive blasting media without using mud, I'd have to think twice before doing so.

Best,
Kelly

 

Definitely some shimmery glass bits still stuck to the castings in the pix you referred to, that is correct. I'll take a wire wheel drill bit to it and it should come right off.

I'd use sand instead of the glass bead if I already had some that is as fine. It would be cheaper for sure. I had not yet found a source for the fine silica yet when I bought the bead medium a few years ago...

I haven't noticed sand in my lost foam castings, but I also don't have a lathe or a milling machine. My drill press and hand drill had no issues though, the bits I used to drill the bolt holes still seem fine. I thought about mudding the inside of the clamp where it would close up on the pipe, but I didn't want to wait for it to dry when it was finally good casting weather out...

I'll post something under lost foam, good point. Although people might be better off not learning bad habits from my "quick and dirty" approach...

Edit - the clumping is from repeated use for lost foam, I'm sure it's the vapours that got trapped in the "sand" doing that. It's been used a few times since I last sifted it and aired it out because my lost foam sieve and my sand scoop were missing all last year. Normally before that happened I would sift it all to declump it and let some of the vapour escape right after shakeout while the sand was still pretty hot. Seems to make a big difference, as the sand now seems to stick to itself more.

Jeff

 

For me, it's really more a matter of on the surface, not in the casting but even with wire wheeling the exterior, there still can be some imbedded sand that persists.....so fo now, I remain a mud disciple.

Best,
Kelly

 

I'm definitely not trying to talk anyone out of using mud, I've seen what you're able to do with lost foam, and if you watch the video you'll see I encouraged viewers who want to use lost foam for more precise applications to check out your stuff...

I'm just too impatient to sit around watching mud dry myself most of the time; for me LF is a technique I only for one offs (well, sometimes for 8-offs too I guess...), goofy fun stuff, and quick 'n dirty "has to work but doesn't have to look pretty or be particularly precise" jobs...

For the record, if I were making parts needing precise machining that I could not sand cast, I'd use the lost foam with mud method too.

Jeff

 

Well, I got one scraper installed long enough to check how it works with some loose sand in the muller. I wound up having to trim it a little to tweak where it was pushing the sand, but I had made it a little oversized for this reason. Seemed easier than building more adjustable holders for the scrapers, though I may live to regret that decision later if I end up having to rebuild parts. Technically it is adjustable I guess, but that would mean drilling some new holes.

A bunch of loose sand did leak underneath the wear plate when I tested the new scraper, took me a quite a while to get it to leak back out. I know when there's molding sand in there it will probably plug up the gap, but I was surprised how fast it was draining down past the plate... Anyone want to try and talk me out of trying to seal that seam somehow? Maybe with some silicone or epoxy or something? Billy Mays' Mighty Putty?

Here's a pic from when I was figuring out where to bolt the scraper on to the lost foam muller clamps, before trimming it down:



There's a thin gap between the scraper and the floor and wall.

Also, I was gonna go pick up the fine silica I ordered on Saturday to eventually make/mull some new sand with, but we lost power for 16 hours on Friday night, so after a late night spent bailing out my basement 5 gallons at a time, despite having a nasty cold, to try and save the new furnace getting flooded, until my phone/flashlight died and I gave up and stumbled through the darkness to my bed, we decided going out to buy a small generator to run the sump pump and make coffee would be a better use of our time... Something we should have done 15 years ago...

I'll be picking up the sand after work on Thursday instead, since the pottery supply place where I'm getting it is right around the corner from the office and my carpool partner isn't coming in to work that day, so I'll have my car. Hoping to to pick up the bentonite tomorrow, finally found place that sells it cheaper (as pond sealer) than the pottery supply place does. FYI the brand name I finally found is "benseal," in case that helps anyone else who's having trouble finding it. I don't know is if it's Southern or Western bentonite, but then neither did the guy at the pottery shop when I asked them about their far more expensive bentonite.

Jeff

 

Sounds interesting. When I make new sand I'll try to pay attention to keeping track of how much water as % weight I'm adding too.

Like I said I'm sure actual molding sand will plug that gap, I'm more worred about losing half of my dry powdery materials down that crack before it has a chance to really become molding sand. I can see the losing a significant amount that way. Only temporarily, sure, but in a way that would mean it's not as much fun to use for making new sand as i hope.

Jeff

 

Another word for word copy of an AA post I just made:

update: the Benseal product appears to come as 8 mesh granules, so perhaps not quite the fine powder I was hoping for.

And it is sodium bentonite, fwiw.

I may check with a feed & seed place nearby, I've read that people feed bentonite to their cows or some such, so maybe they will have the more powdery stuff, and/or maybe it'll be the calcium bentonite so I can use 50/50 of the 2 types as I've seen recommended before.

Jeff

 

I just found out the place that sells Benseal also sells QuikGel, made by the same company, which is 200 mesh sodium bentonite from Wyoming, same stuff just ground up nice and fine I guess. They are asking $16CDN for 50#, should be interesting to see what the feed and seed place wants. And which type it will be. If they have any. I looked into the brew-your-own beer and wine places a while back, they want like $5 or something for just a very small envelope that's meant to be used for clarifying homemade alcoholic beverages, as you say. Not a viable option for us, I'm afraid...

Jeff

 

See, now that is exactly the kind of quick 'n dirty telltale clue I was hoping people would post more of over in the "right amount of moisture" thread: http://forums.thehomefoundry.org/in...e-right-amount-of-moisture-for-greensand.232/

It's probably different for every muller, but now that I've read this I'll certainly be tracking any correspondence between the sand sticking to the wheel in certain ways with days when my sand seems to be working best. I might not have thought to take note of that otherwise, at least not right away. Thanks!

Jeff

 

Thanks. I already picked up a 50# bag branded "quik gel" the other day for under $20CDN including tax, from a company here called Canpipe. I think it is the stuff you're talking about, used/marketed as a drilling fluid. If the stuff that puffs out of the corners of the bag anytime I touch it are any indication, it's quite finely powdered.

Turns out the 'Benseal' I was considering is more like kitty litter consistency (and priced the same as quik gel). I thought it was funny when my friend who's used it to seal a pond told me that... I told her, "you know, it probably is kitty litter, that stuff is made of bentonite too." I wonder if they just put the same stuff into differently labelled bags?

I probably already mentioned this, but this stuff is sodium bentonite. Haven't found any calcium bentonite. Yet...

Edit - My carpool buddy is off today so I have my car at the office. So today is the day, I'll be picking up the fine silica on my way home, the pottery supply place I ordered it from is right around the corner.

Jeff