skull shifter update and lost wax casting info

i really haven't had much dross shrinkage. seems to be some of that happening in the main sprue, but the individual pieces turned out well. probably only 2 of the 97 shift knobs will take a good bit of work to make nice, and they really ought to come out well. if there is any slag or dross (that is the crumbly white and grey crap left behind and sometimes on top of the crucible, right) on top of the pot, i have a piece of flat stock on a handle to hold the crap back while i pour and have had decent success with it. first couple of pours i made last year, i skimmed the slag, until i read that it helps to keep the hydrogen out of the metal. i have also read about a substance that big foundries add to their aluminum to reduce hydrogen absorption, but haven't located a supplier or even a cost yet. i do know that temperature can do alot for you in aluminum casting. i pour between 1250 and 1300, but had poured alot higher than that in the past. it's amazing how much the temp can climb even after the furnace is shut off!

i had several pours today with very clean metal and it dumped nicely without using that paddle. i fill to the top of the cup to give plenty of head pressure, and the metal in most cases was almost a mirror finish. the sunset reflected off of them tonight when i went out to knock shells. a few turned out rough, but by and large it all worked well.

i hit directly, as straight down as i can, because if i do incur any gas porosity or shrinkage porosity, i want the screw up to be as inconspicuous as possible, and i sprue everything from the back. i cast shifter boot rings for skipstitch and have upfed them like you mentioned and have had problems with metal pulling away from the form and down towards the upfeed sprue pretty much screwing the part. early pours also appeared to have some gas porosity towards the top of the pieces.

i'm in the house at the moment, but i'm pretty sure we use rancosil products. i know i've seen that on the bags in the shell room. we order from ransom and randolph in maumee, ohio.

whatcha think, man? any tips you feel like sharing? i've had pretty fair success thus far, but if i can learn more and do an even better job, i'd jump at the opportunity. i've been able to read a few older books on aluminum casting, but they all are geared towards sand casting and aren't totally helpful to me. i've done a good bit of experience learning in the last year. like i said, though, the vast majority of my castings looked great today, even better than the last run of shifter knobs i made.

the pilots and firemen are all spoken for, upchuck, but the others are still available. drop me a PM if you'd like something and i'll get back to ya. thanks man!

 

Man oh man I wish I'd known you were making the firemen. Gotta get in on the next batch!!

 

spending the day knocking shell off and bead blasting, and i'm really happy with everything i've seen except for some wrinkled shrinkage on the surface of a few firemen. little to no gas porosity, 0 shrinkage and great detail everywhere. the few firemen aren't washouts, by any means, but will just take some work to make them pretty.

alot of people will say that ceramic shell casting can't get you the detail that traditional plaster investment casting does, but the folks that have my regular skulls numbered up to about 50 or so have proof that ceramic can get the detail in the form of part of a fingerprint left in the forehead when i sculpted the original skull and formed the brow.

for the WWI pair, i'm thinking about doing something different. the real spiked helmets were leather with metal hardware, and i am considering finishing some with the helmet itself painted black with the hardware and the like on it revealed in polished aluminum with the skull and monacle polished as well. if i do that, i may also paint a few of the doughboy's helmets OD green to follow the theme.

probably gonna leave that up to the customer, though. also up to the buyer is whether or not they want them cleared, which is standard. they can be had in bare polished metal if so desired. i'll post some pictures this weekend of the new stuff as finished pieces. i'm nuts about the WWI guys, alot of personality there...

some of you might have noticed in one of the above pictures that we used a shopping cart to hold the shell when we poured. usually that's not the case, but the bucket i use to keep the shells upright wasn't quite big enough for the germans with the spiked helmets. just about an inch to small in diameter to hold that shell, and we quickly grabbed the shopping cart that we throw scrap bronze im and wheeled it around and used it because we were in a pinch. those germans turned out excellent, though...

 

Any one who thinks that plaster investment is better than ceramic shell is nuts! The only advantages investment has over shell is it's quicker to invest and it cleans off castings with intracate surfaces easer. Aero space uses shell because with tight control of the process you can cast to tolerances. the detail is, as you say, much tighter and you are less likly to get a flash that you will have to chase. Much of the time with shell you dont have to do any thing to the piece but cut the sprews off.

I use shrink feaders in the vent system to stop the sprews from sucking the metal from the casting. I also pinch the gates just before the form.

 

Thanks for the article ChromedRat. It was very informative. I never realized how much work goes into making one of those things. You have my utmost respect! By the way, did I see my "Bunga-Bunga" s/n 30 in there somewhere? Can't wait to see it. I'm going to order another one cuz I have a new project arriving in the next few weeks. Excellent article and keep up the great work!

 

Remember to put me in line for a fireman....again, nice work!!!!

 

the work continues. i bead blast the shell off and use about a half a dozen dremel bits and wheels to get them looking right, and can get around 16 to 20 done in a day's work. here's the WWI guys. i dig the painted look, just enough to get the idea across and enough metal showing that it's clear that they're cast metal. the doughboys will probably be cleared with matte clear on top and gloss on the bottom.

 

wow you are talented..

i like the use of the stolen shopping cart...

 

ha, you know, i'm not sure where that cart came from. i think my grandpa got it at an auction years ago. i know we didn't go out and pick it up, just kinda never noticed it i guess. oh well, it worked when we needed it to! the germans turned out great... oh yeah, that backdrop i used, that's a real pair of WWI pants!

 

So do you use a mold for the original wax castings? Can you tell/show us some info about that process too? I find this absolutely fascinating!

Ben

 

sweet.
this is an absolutley awesome tech thread.

 

I got a pilot a couple months ago & it's damn near too nice to put in my car! In fact, I'm not even sure I want to drill it! haha! ;D

I might be interested in a fireman as a gift for my best friend who's getting married sometime soon...lemme know when you're doing the next round!

 

Thanks for the detailed description of how this process works. I'm sure that there are not many that have a clue as to what goes into a quality casting. I worked for a permanent mold foundry for a short time and one of our products was the intake manifold for the NASCAR SB2B Chevrolet engine (sand casting). Another permanent mold project was the handle for compound bows and we cast thousands of them.
I live just a few miles from the Grey Iron GM foundry here in Saginaw Michigan and the now defunt Nodular Iron foundry so I've had a small exposure to casing processes. It's facinating work and the basics are still the same as it was 100 years ago.
When I subcontracted work from Howe Racing enterprises they had the front spindles for their oval track cars investment cast. That was my first exposure to that process and it's amazing the detail you can get casting with this method.
BTW, I can't wait top get the Bomber/pilot knob I ordered.

Frank

 

Josh,

This is a great thread. I wondered how this process worked. Thanks for sharing. The work's fantastic.

Denny

 

Just Got My Pilot Skull Today .. Thxx Josh .. Killer ..

Now I Need To Order One More For The Mail Man ..

Ill Pm Ya

 

Pocket. I got a army the army dude with the cig hangin out of his mouth coming in the next few weeks. How do ya like yers that ya just got. KNUX!

 

army one ??? i aint seen that yet .. hmmm gonna have to order it up ..

ill have a hole collection pretty soon ..

 

He has one of a doughboy and one of a german soldier with the helmet that has that point on it from the top. Check out page 2 from his thread. KNUX!

 

Yep looks like USPS is hard at it.

Got my Firemen today! Going to drill them out tomorrow.
They are badass!

 

I got my WWII German skull knob today......HOLY SHIT!!!

Josh is a RULER!

The art is top-notch.....the metal-work is top-notch....... the paint it top-notch.........

Worth twice the price.........

Don't miss out!

 

Got my pilot knob today! Absolutely awesome! Thanks Josh!

 

Received my pilot skull yesterday, thank you so much Josh!

I even had to order the doughboy and heinie to round out my set. If they are as nice as the 1st 2 I know they'll be on the shelf for along time. They are TOO nice and detailed to drill! I also don't want some a**hole to rip one off out of my car!


jerry

 

info on how I can order mine? And prices please

 

thanks for all the compliments, guys. i've been hard at work and haven't had a whole lot of time to get on here. the pile of skulls keeps getting smaller! most of them are sold out in this run so far, though i still have about five doughboys and about 10 regular hatless skulls left.

grinder, and everybody else that wondered, if you want one of these, let me know. PMs work pretty good. the regular, hatless skulls are 35$ apiece and the "deluxe" skulls with headgear of some sort run 50$, currently. there's talk of propane costs going up as well as costs for ceramic material (zircon sand, actually, we use it for the first two layers of shell), and i hope it doesn't affect me too much. my rig for the most part is of such a size that my costs are fairly low, so i'm not too worried about it.

i'm going to start gearing up for another run soon and it seems like preorders are how i generally work! this pour will happen alot quicker as i'm on summer break from substitute teaching, too.

if anybody wants to make an order, go right ahead. i think everything i've done has been shown between this post and evil1's website (thanks man) at http://www.evil1customs.com/skull/skull.htm

oh and as far as the wax goes, up to where this post starts basically just involves using a rubber mold (brushed over the original sculpture and then allowed to set up into a silicon-like consistency) to cast wax replicas of the original, alot of which you've seen in this post. each one has to be gone over to fix little imperfections, then attached to the "tree." takes a long time. metal work has been flying by in comparison.

 

Josh,

Got my fireman knob in the mail today. Incredible detail dude!!! Your work is world class!! I PMed you to increase my order on your next run. Thanks again for taking the time to make the firemen. I'm totally stoked and grateful. You are the man!!!

aloha,
rustfarmer

 

got all four of mine today. very cool, im super happy with them and my brother (chromedRAT designed this one for him) and all his fireman buddys are going to love the fireman knob. i hope he sells a ton of em. the pics do not do them justice. i would recommend chromedRAT for anything he sells. he stayed in touch with me the through the whole process. shopping on the hamb is very cool. ive had many transactions without a single problem with any of them.

mark

 

These are awsome!!!!!