I’ve been making some parts along the way but it’s been a while since I posted, so here’s my current project. I had a fella contact me that wanted to run Dual Inline Autolite Carburetors on his Pantera, and since I have a Pantera and do a lot with the Inline Carbs, I took on the project. He had a number of rather unique features he wanted to incorporate, most of which I wouldn’t do for myself, but hey, we all have our own wish list I guess. I’m starting to get a decent library of the pieces that go into making several engine series so I figured it was a good opportunity for me to test my ability to customized some of my CAD/CAM models for one-offs…….. So, off we go. I solid modeled (in Alibre) the 3D machined parts and did the 2.5D stuff in CAM (CamBam). As an aside, I try to do everything I can in 2.5D because it's so much faster on the CAM end, and also because I’m not quite as adept at sketching in Alibre as I am in CamBam. This is mostly because of what it takes to completely define and constrain sketches that will be used to solid model, but I know enough to get what I need and am learning the rest as I go and projects require it. I’ve already done the layout work for interface dimensions with 335 series Ford engines long ago, but once you position the intake flanges at the correct 3-space location, everything else can easily be placed. Most of the pattern fabrication process is captured on a forthcoming video but here’s some of the highlights. There are 5 different and 31 one total pieces that get assembled into the lost foam pattern. Here’s the “kit” and how the pieces came off the CNC Router. I machined each of the runner halves, eight at a time, then hot wired them out of the machining frame……all two-sided 3D machining with a single tool. The carburetor flanges four at a time…one side 2.5D machining The intake flanges one at a time, but could easily become two…..one sided 2.5D/3D machining. The valley pan, one at a time……all two sided 2.5D machining. I have several fixtures to assist in the sequential assembly of the pieces into the completed pattern. My favorite glue fixture………packing tape! I made adjustable (width) MDF base fixture to hold the intake flanges and valley pan in place. I CNC’d a two-sided foam fixture to position the runners and carb flanges. Since I already had the geometry from the piece parts, it only took a couple minutes to knock out the registration fixture and it worked very well. The pieces get sequentially glued together. First the intake flanges to the valley pan. Then the runners to the intake flanges. Then the carb flanges to the the runners. All aided by 35lbs of lead to apply some squeeze and get tight glue joints. So when the final glue step sets up, you have something that’s looking like an intake manifold. It always sort of freaks me out when I handle the assembled patterns because they are feather-light, but surprisingly rigid for a handful of air. From here I’ll add the gating and some structural support features to keep it dimensionally stable during molding and casting process. I’m going to need some cooperation from Mother Nature. -10F (that's ambient temperature not wind chill boys!) and snow this morning with 50mph wind gusts. I need dry pavement in order to keep my LF sand dry because I don’t have a pan large enough to catch 400lbs of sand? Maybe in a week or two? Best, Kelly
That is an amazing assembly of patterns Kelly, thanks for taking us through all of the steps. My back hurts just thinking about 400# of sand... Just a couple quick questions: -What glue(s) are you using with extruded polystyrene? -Will you be adding the lettering shown on the paper? Is so, how? -Will you be making one for yours?
It goes in one shovel at a time but I built my molding rig based upon a 30 gallon barrel with flask extensions, wheels, and mounted on a pivot so it can be dumped for demolding. -This old back can still feel it at the end of the day. My New Lost Foam Casting Rig | The Home Foundry Mostly low melt temp hot glue and Polyvinyl Acetate (white glues, but especially Arlene's fast grab tacky glue variety), but occassionally Poly Vinyl Alchohol, and Shellac. Sometimes, two sided tape. Here's a couple discussion threads. Polystyrene foam gluing techniques | The Home Foundry Confessions of a Lost Foam Caster, 5 Years on. | The Home Foundry (scroll down to glue section). Yes. Doing that this morning. Will post a picture when complete. No, but I do have four more intake projects in the queue. Best, Kelly
I made the mold on my CNC Router. It could be 3D printed. I cast the negative in silicone. The letters are ~.375” tall and .046” thick. I picked and placed these by hand, but sometimes I make a thin backing plate so it’s all one piece. I could have done either here but just wanted the look of individual raised letters. They don't need to be drafted since it's lost foam. In other projects I've taken molds from existing artwork to make ornamental appliques. I don't know what the limit is on size, but this amount of wax is a drop in the bucket for what's going on during the pour and the amount of wax I've used in the past. It gets evaporated and escapes the same way the foam does. I use a wax formulated for lost foam casting, melt it in a spoon, pour it in the mold, then strike off with a hot blade after the wax freezes. It takes a cycle or two of the mold to get good pieces. Once you have the mold, letters are cheap. Then flex the mold, remove with a pick, lay them in place on the pattern….. Then pick and apply glue with a toothpick to the backside (very sparingly), and place them individually……. Best, Kelly
Awesome as always Kelly! What brand of filleting wax are you using? I'm giving up on machining fillets!
Freeman Master Bond Fillet. I used their regular wax fillet for a long time (before they offered Master Bond) on my foam patterns and it seemed to work fine but nothing else I've tried even comes close to the Master Bond Formulation. It's also good for filling/sealing small cracks/defects on your foam patterns. Freeman have a large product offering with similar names so make sure it's the one that states in the product description that it's formulated to melt at the same rate as 1.1lb/ft3 density foam. It can be sort of hard to find at their website. You need to set up an online account to see pricing and order but once you do, you can price and order any product. I use the smallest #2. It's sold in 2lb boxes in 24" strips. 2lbs of #2 = 1152 feet.....a lifetime supply for most hobbyists! The website indicated $43.68 for the 2lb box this morning. Here's a link. FMSC - Master Bond Wax Fillet - Boxes (24" Strip Lengths) (freemansupply.com) https://www.freemansupply.com/produ...ster-bond-wax-fillet---boxes-24-strip-lengths You'll need ball fillet tools and scrapers. Freeman's are very nice. I've had mine for 30+ years. FMSC - Fillet Tools (freemansupply.com) They are sold individually at about $15/each for #1 - #3. The large #4 is expensive. FMSC - Fillet Shapers (freemansupply.com) $51 for set of all sizes. I must say, these work well. The edges are nicely deburred/radiussed so they don't damage your pattern work. Thanks to the art/clay sculptors, you can buy the ball fillet tools inexpensively on Amazon. The scrapers are a little harder to find but they can also be made. You'll need an alchol lamp or heat gun (I prefer) to heat the tools. There's definitely technique for laying wax fillet but with a little practice, it goes pretty fast and definitely produces more professional appearing castings. You know you're a casting nerd when you can write that much about wax fillet LoL! I try to machine fillets where ever possible, especially the larger radius variety, but sometimes for small fillets it's just not practical or worth the effort. Best, Kelly
Thanks Kelly! The fillets I'm not going to machine anymore are where two pieces intersect. The gearcase to the midframe specifically. I either have to trim the parts so the fillet is on the gear-case or the midframe. Each of these cause problems. Eliminating the fillet and placing it after the fact should work better.
Gated it. The long runners/gates on the bottom fed by the Y to the sprue would have been sufficient (in fact preferred) to feed the casting, but the pattern needed additional support to keep it from flexing across the cylinder banks so I added the top spider. The solid web connecting the Y to the top of the intake is also for added strength so the pattern is strong enough to hang after being dip coated without potentially breaking the Y. Otherwise, I don’t think either are necessary to feed and cast the part. I could have used a piece of sheet metal as those supports but I thought it may as well be foam and part of the feed system. After I dipped it and let hang to shed some slurry, I got it horizontal onto its support feet for drying which is always a relief. Although the pattern is feather light, I can assure you it certainly is not when dripping wet with slurry and hanging from that 1.5 x 1.5 in cross section of foam………creates more than a little pucker! It’s substantially stiffer now that the coating has dried……which will help dimensional stability during molding. After a week of being in the deep freeze it looks like a week of above normal temps.......could be the perfect casting weather window. You guys know what comes next! Best, Kelly
After a week in the deep freeze, it was 45F on New Years Day…and I had to take advantage of the warm day. So I cut up some ingot….. Charged the A60 Crucible……. …And had to break out the big furnace and gantry to handle the A60. https://forums.thehomefoundry.org/i...ble-handling-equipment.1703/page-3#post-39125 Molded it. It was a Happy New Year….. It needs to go into my heat treating oven for a day. I left the gating on for added stability while I heat treat it. Best, Kelly
Thanks fellas. It's always nice when the casting turns out looking just like the pattern After hanging out in the oven for 9hrs I didn’t turn it into a puddle, and it still looks like it went in. Introduced it to my mill to remove the gating. While I had it on the mill, I indicated it in, laid out, drilled/tapped the carb mounting holes. The top gate spider did its job holding things in place. They really landed nicely in the centers of the bosses. 1.3% shrink is working very well for me. A video of the project........... Onto finishing it up…… Best, Kelly
Excellent casting all the way through! Keeping it simple and sticking with 2.5d is a really wise choice for time savings too. Machine, flip, glue. ...Those are some really nice rotaries for your knee mill by the way.
Very inspiring, Built my own home Very inspiring, what method do use to calculate over size for the pattern? I'm going to attempt to reproduce a motorcycle set of cases, but my question would pertain to location and sizing for crank centerline and bolt pattern relations . I'll probably cast and learn the hard way but asking first couldn't hurt. Thanks for any help. Tim.
For aluminum casting I increase the scale 1.3%. In CAD, that means just select everything and enlarge by 1.3% or 101.3% of original size. If doing it manually, increase the XYZ dimensions/locations of everything by 1.3%......that's .013 in/in, or .013mm/mm.....etc. Best, Kelly
Tanks, this question I was going to ask soon Nice that it's so easy with CAD. When you use a Sand core, do you oversize the core too? I Think that would not be necessary for the core, because it stays at it's dimensions...