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mekilljoydammit  
#1 Posted : Sunday, February 15, 2015 5:03:18 AM(UTC)
mekilljoydammit

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Well, so, and this isn't well documented, but I built a home foundry setup; it uses a hot water heater shell filled with homemade castable refractory, with an old fuel oil furnace burner for a heat source. So far I've done nothing of any significance with it, so why not change that?

Well, first we need something to cast. Previously I did some experiments with a home 3d printer setup and pseudo-lost-wax casting. Turns out the plastic burns out just as well as wax does, so you can go directly from a digital model to a physical one.

First stage is the digital model. I started by scanning an intake manifold gasket for an NA 13B on a flatbed scanner, then sizing it up in solidworks. A bit of messing around and I have this.

UserPostedImageNA 13B IM by killjoy_tseng, on Flickr

Basic idea is that it's designed to mate to a set of Artic Cat snowmobile throttle bodies - off the shelf with 48mm butterflies, injectors, etc. Goes to little boots to mate up. At some point I may have to add gussets or thicken up the casting walls or something, but this is more or less a proof of concept. This is intended to go on a Lotus 7 clone, so the fact that the throttle bodies are extending straight out the side isn't much of an issue.

Next step is to figure out how to get it to a size that fits on the 3d printer I have handy. Well, and take a tape measure to the frame and figure out what runner length actually fits. Right now it's something like 7" runners plus another 1.5-2" of runner length for the throttle bodies... so maybe high RPM oriented but oh well. I can always do a wraparound manifold if this doesn't work.
BoxedFox  
#2 Posted : Monday, February 16, 2015 12:55:34 PM(UTC)
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Wait, you have a foundry at your house? Screw the car stuff, I want to see THAT.
StudioVRM.net

I'm back! And causing trouble again...
mekilljoydammit  
#3 Posted : Monday, February 16, 2015 8:19:01 PM(UTC)
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Small foundry. It's a hot water heater shell lined with homemade castable refractory. Heat source is an old fuel oil furnace burner. Works pretty well for aluminum though; melts a couple pounds in a half hour or so.

I'll take pictures next time I fire it up - right now to use it I would have to wheel it out into the snow. It's kind of terrible looking, but on the other hand, I have maybe a hundred bucks into it.
mekilljoydammit  
#4 Posted : Monday, March 02, 2015 11:12:15 AM(UTC)
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UserPostedImageEProd Ported NA 13B IM by killjoy_tseng, on Flickr

Mk2 version; corrected wall thicknesses to something castable, corrected a few dimensions to fit the snowmobile throttles, and most importantly revised it for the E Production style porting on the pile of irons we have kicking around.

It was pointed out that doing castings when there's snow on the ground may not be wise; something about molten aluminum hitting snow and having steam explosions splashing aluminum around or something. Bah. Maybe I should start taking pictures of the Lotus 7 clone project this is for in the mean time, at least until I try to print it.
nickbetz  
#5 Posted : Tuesday, March 10, 2015 8:32:35 AM(UTC)
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Need pics, I want to see this...
mekilljoydammit  
#6 Posted : Tuesday, March 10, 2015 11:24:22 AM(UTC)
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Forgot to take a camera out tonight... actually was working on finding parts to build our 1st gen RX-7 roadrace car. Found a 13B that we didn't know we had and still aren't sure where it came from... but not sure we have enough good 12A bits for a good motor. Time will tell.
mekilljoydammit  
#7 Posted : Friday, April 24, 2015 7:48:08 AM(UTC)
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Okay, over the last month I built my own 3d printer. So I did a half scale print of this as a proof of concept. I'll post pictures tomorrow; can't get good light in here. Next steps will be to print a calibration cube and cast it (I know that shrinkage should be a known value but I want to be sure) and scale the design to that to have a dimensionally accurate final part. And some tweaking of printer settings, because this was literally my second print on this thing.
mekilljoydammit  
#8 Posted : Wednesday, April 29, 2015 9:22:05 AM(UTC)
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A couple days late. Oh well.

UserPostedImageDSC_6391 by killjoy_tseng, on Flickr

Half scale mockup; it's literally the second thing I printed, and I'm spending a lot of time improving print quality. And yes, the lighting is far from the best. Still.
M-P  
#9 Posted : Wednesday, April 29, 2015 11:03:10 AM(UTC)
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For your second print every that thing looks pretty good. It took me a good year using mine before parts came out nearly perfect 95-100% of the time. Got any details on your machine?
mekilljoydammit  
#10 Posted : Wednesday, April 29, 2015 11:15:10 AM(UTC)
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Machine is an Ordbot Hadron with a Smoothieboard for a controller. Hot end setup is something that seemed like a good idea to me - E3D V6 hotend with an EZstruder feeder driven by a planetary geared motor. Had to modify stuff a bit to make it fit together right, but works great so far. The other fun part is the bed... sandwich of cork, aluminum PCB heatbed, and an Ultem PEI build surface. PLA just sticks when it's warm, and then comes right off when it's cool, no muss, no fuss.

Right now I'm tweaking the temperature settings and building a duct to cool the prints - I have to knock the speed down from what it's capable of to have good quality, otherwise everything gets a little melty. Eventually I'm going to lengthen one of the axes so I can theoretically do something the size of an I4 cylinder head in one shot, but that's down the road.
M-P  
#11 Posted : Thursday, April 30, 2015 5:07:58 AM(UTC)
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Originally Posted by: mekilljoydammit Go to Quoted Post
Machine is an Ordbot Hadron with a Smoothieboard for a controller. Hot end setup is something that seemed like a good idea to me - E3D V6 hotend with an EZstruder feeder driven by a planetary geared motor. Had to modify stuff a bit to make it fit together right, but works great so far. The other fun part is the bed... sandwich of cork, aluminum PCB heatbed, and an Ultem PEI build surface. PLA just sticks when it's warm, and then comes right off when it's cool, no muss, no fuss.

Right now I'm tweaking the temperature settings and building a duct to cool the prints - I have to knock the speed down from what it's capable of to have good quality, otherwise everything gets a little melty. Eventually I'm going to lengthen one of the axes so I can theoretically do something the size of an I4 cylinder head in one shot, but that's down the road.


Very good machine (almost built one myself) and smoothieboard is suppose to be the shit. E3D V6 is prime (I run an E3D V5 on my Rostock Max, but also have Volcano, Chimera, and Cyclops sitting on my desk...just haven't got around to playing with them).

You really need to start playing with ABS and Nylon since you have a machine that is perfect for it (will help your melty problem too). Biggest recommendations I can give is start with slow printing speeds and don't skimp on material quality.

Happy printing!
mekilljoydammit  
#12 Posted : Thursday, April 30, 2015 6:39:42 AM(UTC)
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ABS and Nylon have their uses and I obviously didn't want to rule them out, looking at some of my selections. PLA is really nice for castings though; I get good dimensional accuracy and it burns out really well and non-toxicly. And a good portion of what I'm looking at doing is based around castings; eventually I want to get up to doing cylinder heads, bellhousings and transmission casings and such. Which I realize is ambitious, but hey, what the hell.
mekilljoydammit  
#13 Posted : Sunday, May 03, 2015 11:49:11 AM(UTC)
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Okay, cast a calibration cube today. Theoretical size was 40mm cubed - actual printed size was about 39.6x39.6x41mm or so. Size after casting... will be TBD. I want to use the same equipment to measure it that I did beforehand which means the sutff at work.

UserPostedImageFoundry by killjoy_tseng, on Flickr

Here's the foundry. Yes, it's very very hacked together. Shell is a hot water heater tank, and it's lined with homemade castable refractory. Lid has the same plus some rebar. Heat source is the burner on the lower right side; it's a fuel oil burner we had leftover from converting to gas heat. Hinge is a VW Rabbit clutch pedal with some stuff welded to it - hey, it was handy. Inside size is something like 12" ID by 18" tall. I haven't taken a precise measurement, but burning diesel, getting from room temperature to pouring temperature for a couple pounds of scrap aluminum takes all of about half an hour.

UserPostedImageCube by killjoy_tseng, on Flickr

This is the result. A few casting defects, probably because I didn't put any vents in or possibly because the aluminum temperature may have been a bit high. Or maybe I didn't let it burn out long enough. One way or another though, they're just surface defects and it should be close enough to let me establish a scaling factor.
smartbomb  
#14 Posted : Friday, August 14, 2015 7:05:19 AM(UTC)
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updates?
mekilljoydammit  
#15 Posted : Friday, August 14, 2015 9:33:34 PM(UTC)
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Yikes, it's been 3 months since the last update.

Basically I've had two things taking up my time lately, though I'm about ready to get back to this.

One, after borrowing a Spec Miata for a driver's school, my dad realized that what we really need is a stone dead reliable car to actually get some experience in. So he decided that since they have an RX-8 and an NC Miata, to build the Miata up for SCCA T4, which is annoyingly close to showroom stock plus a suspension package and a few other boltons. As an engineer, it bugs me, but I really do see the point - and it gives opportunity to actually shake out the RX-7 and do it right, rather than do a series of rush jobs. So that build's about done, aside from a mishap Thursday with a missing hood latch during a test drive (it's actually still street legal) First race is tomorrow if we can get the windshield replaced.

Two, I managed to get financing together and bought a house. It's hard to race a house, granted, but I not only have a garage of my own, but 4 acres and a barn, which is nice because it preempts what I've seen happen at most gearhead's houses where all the street cars end up parked in front of the garage. I'm also a lot closer to the race shop at my folks place too. No downsides, aside from 30 years of debt and all.

Anyway, plan is to try to print a full scale version of the intake manifold in the next week. I got some advice about sprues and gating from people who do castings for a living so hope to end up with less porosity than the test cube. Also, through work learned of a local place that does reverse engineering for reasonable prices. As an experiment, I'm going to take them a dead 12A rotor and see if I can come up with something printable and castable in the same way as the manifold. There's a castable metal matrix composite system that seems fairly easy to approximate - in research they just stir silicon carbide powder into molten aluminum, and if you balance everything right, the tensile strength and thermal expansion ends up about the same as cast iron. No idea if it'll work out like that in practice, but worth a try.
smartbomb  
#16 Posted : Wednesday, September 02, 2015 4:13:30 PM(UTC)
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keep us posted!
mekilljoydammit  
#17 Posted : Thursday, September 10, 2015 9:42:02 AM(UTC)
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All right, pictures to follow once I get around to it, but I finished printing a full size pattern. Hopefully I didn't mess any dimensions up - I didn't feel like printing a dummy for a fitment test. Now I just need to figure out the molten-metal-runners and stuff (there's technical terms I can't remember) invest it, cast it, and see if it fits.

Well, and throw together a mockup 13B; funny, the only one I have together right now is peripheral ported and thus not really relevant to this manifold.
mekilljoydammit  
#18 Posted : Monday, March 06, 2017 2:00:32 AM(UTC)
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Oh hey, remember me? I figured I might as well post some things, though I've gotten pretty hard into the "scope creep" side of things.

So, I mentioned a full size pattern - here it is!

UserPostedImage

The problem is, I realized that the EProd style intake port is a silly thing to use on a street engine that's not constrained to use the 6 port 13B irons. So I may not bother to invest and cast it. And besides, I'd need to tune it and other things.

In the mean time I decided to do a Fury Road themed Christmas present.

UserPostedImage

The foundry in action... for those of you in California, that white stuff is called "snow". It was about -20F out that night. Because of the mass involved, it took a long time to heat up.

UserPostedImage

Down the business end with the lid open.

UserPostedImage

The finished product! Pretty happy with how that came out.

But anyway, I realized that I don't have any good way to optimize the intake manifold, and I bought an NA Miata to build for an SCCA roadrace class where I can put a 13B into it, so I have a lot of interest in optimizing everything while I learn to drive by sharing the roadrace NC MX-5 with my dad starting in a couple months. And given I'm running (smaller) engine dynos all the time in my day job more or less every day, they're pretty thoroughly demystified... so I decided I'll just build my own engine dyno.

See what I mean about "scope creep"?
KP1  
#19 Posted : Wednesday, August 09, 2017 11:20:19 AM(UTC)
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Looks awesome! @smartbomb Did you see this?

Which SCCA class are you competing in with the Miata? How is that build coming along?
mekilljoydammit  
#20 Posted : Wednesday, August 09, 2017 10:20:08 PM(UTC)
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Whoa, weird, a response to this forum that isn't a spambot.

The NC MX-5 I'm learning what I'm doing in is built for SCCA T4 - sort of "showroom stock plus a bit" in that we're allowed a spec suspension package. Actually kind of clever - the shock setup came about from dynoing the Sachs dampers on the last generation pro cars with the clickers in the middle and valving Bilsteins to dyno the same.

I make no claims of expertise in driving, mind - I just got my competition license this year, so the NC is a great car to learn in.

The NA is sort of a "next" car and I figure I have time to do it right. It's being built for SCCA STU - in short I'm looking at a (big) streetport 13B breathing through a Weber IDA (rules requires carb or stock manifold and the carb's worth more power) with an Aisin 6-speed behind it. I have a theory that I can mix and match enough parts to put an RX-8 front section on a FR-S/BRZ centersection (possibly with MFactory 1/2 and 6th gears) and an NB Miata tailsection on it, and I found 5.38:1 rear ends which would give 5 reasonably decent track gears out of that transmission.

Of course, I get bored sometimes, so here's WIP of the thing after that.

UserPostedImage
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