Two Barrel Carburetor

Discussion in 'Lost foam casting' started by Al2O3, Dec 28, 2019.

  1. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Although the ABS may flex I'd say this wax would likely adhere to it after it solidifies. It does to about everything else.....except silicone. Might work with release agent. The silicone is self releasing from most things. I use a compressed air stream to chill the wax, then slightly deform the mold so there is the slightest gap between the mold and wax and the compressed air pops them right out without damage. Then I heat some more wax in a soup spoon over my heat gun and pop the next one....couple minute cycle time usually. I still foul one up occasionally....back into the spoon those go.

    I let them sit and cool on a cold surface before handling them and try not to handle them too long because they can become soft and easily damaged. Without good release, I suspect the least bit of mold adhesion would just cause the wax to adhere and deflect with the mold when you tried to demold. Sort of a pain but it's really good material for lost wax directly on lost foam patterns. -All nuance but sometimes it's the little things that matter.

    I make the wax embossments from the Freeman fillet wax formulation for lost foam. It's very similar to the fillet wax I had sent you with a little lower melting temperature. In fact, I think you pointed it out to me because Freeman had more recently introduced it since I had purchased my fillet stock. This stuff gets sticky with a modest increase in temp. In fact, I used it to mount the SLA patterns to the backing board. I just held a tiny piece between my fingers for 10 seconds and could apply it by smearing on the back. Then I just waved it across the path of the heat gun a couple times, then press & stick. Easily removed when your done. -Not quite the bond of "sticky wax" the lost wax guys use to attach parts but plenty good for this. It doesn't readily come off your fingers without a little heat and pressure.

    Best,
    Kelly
     
  2. ddmckee54

    ddmckee54 Silver

    Kelly:

    I must have gotten lucky.

    I made a silicon boot for the hot end of my 3D printer using a tube of high temp silicon gasket that I got from NAPA. I only had to burn my hand on that hot end once to know that I needed something covering it. I know you can buy the boots, but where's the fun in that? My mold was a 6 part mold with a core, and all mold parts including the core were printed from PLA. I read somewhere on the ole Interwebb that the glycerin in KY Liquid made it an excellent release agent and actually helped to cure the silicon. So I painted that on the mold and the core.

    It must have worked because 24 hours later the cured boot popped out of the mold with minimal problems. I had provided a number of small vents to let any trapped air out of the mold; the excess silicon had to go somewhere so it oozed out of the vents. Convincing those 1/16" rods of silicon to let go of the mold was the hardest part of demolding the boot.

    The boot has been in use on my printer for more than a year now and is holding up quite nicely. This use includes a bunch of 8-10 hour prints, and a few 20+ hour prints. Plus I haven't burned my hand on the hot end since I made the boot.

    Don
     
  3. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I finished up the Air Horn Patterns

    118 Air Horn Patterns.JPG

    Got that pesky embossment mounted on them too

    119 Monted Logo.JPG

    When I dip coat the patterns, there is a strong buoyancy force and when coated they are a lot heavier until they dry. So I added the brace between the patterns for support.

    120 Air Horn Brace.JPG

    I had a couple stragglers so I thought what the heck….cast them up too.

    121 Catch All.JPG

    Supposed to be 60F+ Saturday and Sunday. If that forecast holds it’s gonna be CastaPaLooza!!

    Best,
    Kelly
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I finished up the Air Horn patterns:

    118 Air Horn Patterns.JPG

    Got that pesky embossment mounted on them all too

    119 Monted Logo.JPG

    When I dip coat the patterns, there is a strong buoyancy force and when coated they are a lot heavier until they dry. So I added the brace between the patterns for support.

    120 Air Horn Brace.JPG

    I had a couple stragglers so I thought what the heck….cast them up too.

    121 Catch All.JPG

    Supposed to be 60F+ Saturday and Sunday. If that forecast holds it’s gonna be CastaPaLooza!!

    Best,
    Kelly
     
  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    That's great Don. Silicones really are some great materials; great temperature and chemical resistance, easy to work with, and relatively safe....completely so after cured.

    Best,
    Kelly
     
  6. ddmckee54

    ddmckee54 Silver

    Kelly:

    I was think more along the line that using the glycerin based release agent might help with the mold curing problem you experienced. Worth a shot?

    Don
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    OIC now. I'll have to do a little more research on the subject of Glycerin and Si but releasing didn't seem to be a problem. I even used Polyvinyl Alcohol on one sample which forms a skin that is a barrier to just about everything and had the same inhibiting reaction and localized cure failure. Chemistry is definitely not my strong suit and I'm at about to become at risk of telling you more than I know, but even though they both have silicone polymer as base materials, I don't think any one part silicone in a tube and the Tin & Platinum catalyzed variants are the same animals when it comes to curing.

    The one-part silicones in a tube are often referred to RTVs but that's just a generalization for Room Temperature Vulcanizing. In fact, vulcanizing was the Goodyear invented process that introduced sulfur for hardening natural rubber and it started being used as a generic term for hardening other elastomers, but in the case of one-part silicones, I believe they actually do contain sulfur thus the typical odor and they tend to stick to most everything whereas the two part systems do not with a few exceptions and you usually need to introduce things that promote adhesion to get them to stick to anything but themselves. The curing agent in these two part mold silicones are actually catalyzed with Tin and Platinum. Catalysts increase the rate of the chemical reaction but catalysis is some strange juju and can be easily altered and not always for the good........and that makes me hesitant to introduce any additional substances.

    ......but thanks for the suggestion and I may need to do a little experimenting next time I make a Si mold.

    Best,
    Kelly
     
  8. ddmckee54

    ddmckee54 Silver

    I hear you, my last chemistry course was a LONGGGG time ago and it is more forgotten than remembered.

    Don
     
  9. rocco

    rocco Silver

    FWIW, one part RTV silicone is water catalyzed, normally it's just the moisture in the air that kicks off the curing reaction, that's why RTV normally cures from the outside in. You can make RTV cure quickly and evenly by mixing in a moisture laden powder, such as ordinary corn starch, through the RTV and you end up with a putty-like substance with about a 3 or 4 minute open time that you can use make a quick mold. It's not as easy to use as a two part tin or platinum based two part silicone but it's cheap and the components are readily available almost anywhere.
     
    Last edited: Mar 5, 2020
  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    As forecasted, the weather was great today. I had a good casting session. Same routine….

    Dipped and ready to go.

    121 Air Horns Dipped.JPG

    As they came out of the sand.....all good

    122 Air Horns As Cast.JPG

    Degated and cleaned up.

    123 Air Horns.JPG

    The embossments came out very well

    124 Air Horn Single.JPG

    I also had that one catch-all cluster. So here’s today’s total bounty. I made a couple accelerator pump covers and stuck them on that cluster.

    125 Days Bounty.JPG

    They are only about 1.5” square and 1/8” wall.

    126 Diaphram Cover.JPG

    They came out nicely. So I made 32 copies and stuck them all on a single tree……a 32-on is a first for me. It’ll either be a great one and done or………….?

    127 32 on Tree.JPG

    Best,
    Kelly
     
  11. Gippeto

    Gippeto Silver

    Some great looking unobtanium Kelly. Best of luck on one n done too.

    Al
     
  12. DavidF

    DavidF Administrator Staff Member Banner Member

    Show off. Lol :D
     
    Mister ED likes this.
  13. rocco

    rocco Silver

    It doesn't matter how many times I see your work, I'm gobsmacked every time!!
     
    Last edited: Mar 8, 2020
    Mister ED likes this.
  14. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I had a minor mishap last night when I dipped the 32-on tree. When handling it just after being dipped, the MDF button glued on top of the sprue split in half and the whole wet tree fell back into the vat of slurry in my dip coating rig. Four patterns broke off when it landed. Rats!! So I gathered and touched up all the pieces where I had handled them and let them dry overnight.

    128 Breakage.JPG

    This morning, I just scraped the coating off the affected areas, got out the hot melt glue gun and put humpty-dumpty back together again.

    129 Fixed.JPG

    Into the flask it went. I had to be very careful packing the flask filling it a quart cup at a time with a fine shower of sand so it filled and supported everything very uniformly. Then just vibrated as usual.

    130 in Falsk.JPG

    ….and I’m happy to report it’s one and done! As it came out of the sand:

    131 As Cast.JPG

    It’s kind of crazy looking, like a strange radio antenna……….and it rings like a bell.

    So if you’re going to cast something 32-on, you’d better have a good de-gating strategy because if that takes forever you haven’t gained much…..

    132 Degate.JPG 133 Degate.JPG 134 Degate.JPG

    Here they are completely de-gated and cleaned up.

    135 All Cleaned Up.JPG

    That’s all of the castings for this project……and I have to say, I’m a bit winded, but happy with the results. I need to heat treat them and send them to my partner in crime for machining. I need to think on it but I’ll try to do one more post for a project summary.

    Best,
    Kelly
     
    Tobho Mott and Mark's castings like this.
  15. You could have made a Ford style oval logo: "Kelly":D
     
  16. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Thanks fellas.....still cant believe this lost foam stuff works......:). At over 120 total castings made during this project, I think I satisfied my urge to make carburetor castings for a while. Sort of felt similar to completing my last bid dry-walling project..........that was 17 years ago.

    Ahh yes, and done in "Ford Font". Petee turned me onto that a while back. Maybe someday it will cause someone to pause and wonder what they really are.....automotive or driveway casting archeology.

    I tell ya what, my back sure knows the difference between eight 60-lb flasks and one. Each flask is filled twice; once to pack and and then dumped, classified/sifted and reused, or stored. So you end up throwing 1000lbs of sand in a day. That was Saturday. Sunday morning it was just that one flask with the 22-on pump covers. Saturday night Night felt completely different than Sunday night!

    I obviously took some liberties simplifying that accelerator pump cover. I was tempted to just accept the shrink, pull a silicone mold from the original, pop waxes patterns, and then block investment or shell them but it was so fast to do what I did in lost foam, I needed to complete the project and move on.

    But, in the future, I do think a precise reproduction of the accelerator pump cover is an ideal part for block investment as a net shape part in Zamak which is what the originals are. A 3D SLA printed master may be my first project when I get there.

    Best,
    Kelly
     
  17. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Besides the castings themselves I try to get something out of every project. Looking back, there were a total of 122 castings made:
    1. 5 different parts were developed, tooled, and cast
    2. 8 development pieces cast.
    3. 106 Production castings; 14 each of the Throttle Body, Main Well, and Air Horn, and 32 each of the Venturis and Accelerator Pump Covers.
    4. 8 extras cast from leftover patterns
    5. I only had one casting fail throughout the project and that was on the first development Throttle Body back in post #20. http://forums.thehomefoundry.org/index.php?threads/two-barrel-carburetor.947/#post-22077
    6. 149 pictures were posted to the thread.
    The project started the last week of December and completed the first week of March. I didn’t keep track of hours. It was just after work and weekends as I could. Here’s a picture summary of the project all in one place for posterity’s sake. If you are just visiting this thread, see post #1 for the purpose.

    136 Throttle Body.jpg 137 Throttle Bodies.JPG 138 Main Well.jpg 139 Main Wells.JPG 140a Air Horn.JPG 141 Air Horns.JPG 142 Venturi.jpg 143 Venturi Fit.JPG 144 Venturis.JPG 145 Accel Pump Cover.jpg 146 Accel Pump Cover.JPG 147.JPG 148.JPG 149.JPG

    I also was thinking about process development. What worked well, what could have worked better, and saved time. For the most part, I felt everything worked well.

    Foam Pattern (Re)Production:
    The Pin Router is pretty good, but a CNC router would be faster and more accurate overall. I think programming and tool development would be about a wash but to the extent this can be achieved, being able to be productive with other things while a machine cut patterns would be savings. One of the biggest savings could be avoiding having to add details by hand like gluing on features and applying wax fillets but this would require tool changes on a simple CNC Router. A net shape foam pattern directly from the CNC, ready to sprue and dip coat would be the best.

    Pattern Coating and Casting Feed System: I think I have my coating pretty well optimized for gravity feed aluminum casting. The combination of the coating permeability and the Offset Pouring basin really work well. All the pours were very tranquil and essentially no flame or burp back through the sprue. The metal just covered the sprue opening paused and then drew from the cup. The sprues and gates need to be strong enough to withstand the buoyancy forces of dipping, it is a very fast process as far as labor and dries overnight. Weaker patterns and feed systems can be coated almost as fast with the aid of a pouring cup or large spoon/ladle instead of immersion. This usually means the sprue and gates are much larger than they need to be compared to conventional open cavity sand casting but it doesn’t matter much because metal speed is dictated by the ablation rate of the foam not gravity or sprue runner cross section.

    Mold Packing: My flasks and molding rig are fast and work well. Casting orientation is important. Positioning to minimize overhangs and large horizontal surfaces under pattern surfaces. Other than this, the speed of lost foam mold making is probably second only automated production molding equipment. It is much faster than I could hand ram a sand mold and there is no sand conditioning required whatsoever other than shoveling it through a screen (or classifying as the industry guys say). I just position the pattern, pour in loose sand, vibrate for a couple minutes, done. Demolding is just dumping the bucket on my driveway. I have 300lbs of ordinary silica sand I’ve been reusing for several years since I started casting. I bought 7 bags at the big box stores. It cost me $28 total. Other than keeping it dry and passing it through a coarse screen when I shovel it back into the flask/storage bucket, I treat it with disregard.

    Melt Management: No need to go too deep into this because it would be the same for any casting process. I poured everything at 1475F-1500F. Lost foam (aka “Full Mold Process”) requires ~+150F compared to empty cavity conventional sand casting for the energy required for foam ablation. I use a carbon sheathed contact pyrometer to measure melt temperature but I’ve done so many melts now I can be very close with elapsed time. For all of these castings I used A356 ingot, with Strontium modifier TiBor refiner. Modifiers and Refiners were probably unnecessary, but I had both master alloys so I used them. You all know I use a resistive electric furnace. It is clean and melts as fast I can pack, cool, and demold two five-gallon flasks in between melts. The total duration of the casting sessions for the three separate 8-flask sessions was on the order of 2 ½-3 hours cold start to sweep up and finish.

    Best,
    Kelly
     
    Last edited: Mar 11, 2020
  18. DavidF

    DavidF Administrator Staff Member Banner Member

    Hmm, a couple of those would look pretty good sitting on top of my big flat head :D
     
  19. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    As a 700cfm 2brl, probably on the largess side for a flatty.......even with smaller throttle body and venturis in an independent runner manifold. For discussion's sake, what's the displacement and approximately power level at the corresponding rpm?

    Best,
    Kelly
     
  20. DavidF

    DavidF Administrator Staff Member Banner Member

    It's only 255 cid and about 200 hp @ 5k, so yea no way they would work out very well, but would look cool as hell sitting in a parking space.
    I have a couple stromburg 48's I'll be running on the big flatty, I think they are 170 cfm each..
     

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