Looking good Kelly. The ears on the main well came out great. Bummer with the throttle body, but the change in sprue length should fix that.
Thanks ESC. I guess I can see a short pour for all the reasons I previously mentioned but to not even make it into the actual casting it must have been some cold metal too. I melted inside, pulled the half full A10 at 1450F, and then had a slightly longer walk to the mold than usual but even so, it was just a few steps and probably only 10 seconds instead of five from furnace to pouring cup. I think the real culprit is it being the second pour from the crucible which probably allowed another 20-30 seconds to elapse, and even though pouring a nice thin continuous stream is good foundry practice as far as bifilm theory goes, I think that thin stream can really lose a lot of heat, especially in a cold Midwest Winter breeze. Oh well, enough excuses. -The things we take for granted. I have a few other things to sort out before production parts. There is a venturi/choke that nests in the bores of the Main Well. It was a net shape part with a tapered fit for the die cast parts. There's enough machine stock in the sample part to accommodate but I may take a stab at some refinement of this feature before I tool the venturi. I'll have to tackle that while I'm sorting out the throttle body.....but back to the day job for now. Best, Kelly
Got home from work tonight, marched straight to the shop, and poured the second round on the Throttle Body. Registration of the bosses looks good. .....'Ya can’t keep a good man down. Best, Kelly
So true. I enjoy the development work more than the repetition....still have a little development to do and want to machine at least the interface features on the castings before spitting out copies. I do kind of like treeing up multiples and getting multiples per pour......risk reward equation changes the thrill factor a bit...lol. Best, Kelly
My dad used to say that the beat way to to do a long boring job is as fast possible, making it less boring and over quicker. He was an electrician and once was wiring a long row of identical houses by himself. As he worked he thought about ways to speed it up. On the last day he wired 3 houses! The upside also was he was being paid by the house, not the hour.
I machined most of the carb features to check fit, position, and ensure the castings were metal rich everywhere they needed to be. I didn’t machine the bores for the throttle shafts or some of the fuel passages that would have required more elaborate fixturing…..but it’s starting to look like a carburetor. Main and idle circuit components Float and metering valve... Idle.... ….and shown here with the original castings. I also did some fine tuning on the tooling and work on the venturis…..more on that later. Best, Kelly
You just know that in a hundred years time, this carby is going to cause some major arguments amongst automotive historians.
Before it's done, I may add a few other features to confound the automotive archeologists. I made an obvious machining error that I didn't notice until I posted the pictures to this thread. When I made the second throttle body, I added a web to the casting to keep it stiff and stable through heat treating and machining with the intent of removing it. Problem is, I machined out the wrong side. Doh! The other side is what needs to be removed to provide clearance for the spring that connects the levers on the throttle shaft and accelerator pump diaphragms. It's just a set up part but silly error. Best, Kelly
There's a 5 gram weight saving right there.. Vizard would be proud How will you clean up the 'funnels' and such?
Funnels? Assuming that refers to the ejector (we call'em boosters), the ID gets machined and the OD as cast but could benefit from some light cartridge roll work. There is a second machined part with radius and reduced ID that generates the low pressure zone to draw fuel through the down-leg. It gets pressed/staked into the bottom of the booster. ...........and I am a David Vizard disciple! Best, Kelly
Thanks, appreciate you have trunks rather than boots and bonnets are worn on heads, lets not do the pants thing ... Vizard enspired me and still does. Keep posting, love watching the progress!
Wow, great work Kelly! I'm more and more impressed with what can be made with the lost foam method. I'm also impressed with the pattern making, and like Rocco would love to see the actual making of the foam patterns with the pin router. In your spare time of course
Thanks kisoia. There is definitely some learning curve in the mold prep and casting side of lost foam but after you get past that, it's all about the pattern making. The quality of the castings will never be any better than the quality of the patterns. The links below aren't for these carb parts but they do contain some imbedded videos of pin routing patterns. If you'd like to see the carb patterns being cut, I'll see if I can do that when I make the production patterns. http://forums.thehomefoundry.org/index.php?threads/chainsaw-cylinder-head.268/ http://forums.thehomefoundry.org/index.php?threads/machining-xps-foam-patterns.14/ I also started this thread some time ago on the Pros/Cons of the process. I should probably do some updating on this thread. http://forums.thehomefoundry.org/index.php?threads/lost-foam-pros-cons.120/ I finally broke down and ordered a hybrid CNC router & plasma machine. It'll be a while for that yet but I certainly don't feel too constrained by my present methods and most anyone with some woodworking skills could make patterns like I'm presently doing it. Best, Kelly
Thanks for those links, they're a good explanation of the process. Are you happy with your dust collection system?
It's a big improvement over no dust collection, makes clean up much faster, but some operations will still eject foam out of the hood onto the floor and surroundings. The foam tends to develop a charge when cut and clings to surfaces (and me!).......but it vacuums right up or can be blown into the dust hood quickly with compressed air. Best, Kelly
Managed to get some shop time in this morning. The Throttle Body and Air Horn tools are ready to make production parts. The main well needed to be adapted to receive the venturis, and the venturi tools need to be made. The mod to the main well didn’t require anything more than cutting the bores with 3-degree tapered bit but that meant the plugs that mounted it on the pin router template also had to be tapered to match along with small step at the top. Here are those completed mods along with a sample part. The Venturi tooling took some doing. There were four operations starting with a fixture to make a cylindrical blank that measured 2.625” OD, 1.75” ID, and 1.69" Tall. I made a round MDF socket that the fit the blanks that I could spin on a simple fixture to cut 7.5 degree taper on the lower portion of the ID, and radius on the upper portion of the ID, and then finally a plug fixture that matched those features so 3 degree taper could be added to the OD. Each of those operations are shown below. If you follow all that, the Venturis come out of the fixture like this. Here are the main well and Venturi along with the same from the original carb. So with all that, the Ventuirs nest and seat into the Wain Well, transition the inlet air around the booster, and expand to the throttle plate diameter. The idea for the Venturi, like the original carb, is to have a net shape part (or very near net shape) that will install into the Main Well as cast. The Venturis are a bit fragile and fitting parts to a 3-degree taper is a pretty tall order for the precision of these processes. We’ll see how it works out. Now comes repetition. Best, Kelly
That looks really good!, it just occurred to me that you might be able to solvent vapour polish the styrofoam to make it smoother, like the 3D printer guys do. It would be difficult to do on styrofoam however.
