You know, I can't remember actually. You gotta be careful that the glue you use doesn't melt the styrene though. We might have used weather strip adhesive or rubber cement, but I could be FOS on that score. It's been damned near ten years now since I took that class. Some of the details are getting fuzzy.
I used my wifes hot glue gun. Hot glue was recommended on one casting sight. I saw no evidence of it afterwards in the pour. This boring bar fixure on my lathe is what i made. The texture was good. Best i have ever had actually. A few minutes with a file trued up the surfaces . It is quite a large piece. Biggest I have ever poured. I almost didnt have a big enuf pot. I have had the intake manifold (318 Poly cross ram)thing on my mind too. First I need to make a foundry ruler to account for shrinkage. I wouldn't be able to pour it here as I cant melt enuf but the local foundry would pour it for me . I figure I would set it all up in a wash tub and truck it over. I even thought of pouring the bottom with standing walls then pouring the lid the intermeshed with the free standing walls then welding it up. But that willl have to wait. I have more than enuf to do now. Don
Wow, fascinating stuff, I guess I will use propane; did not want to in the first place, but I have a large cylinder, and your melter/furnace is simple enough Don, I will wait and get a few other things "on the road", so to speak, but the foam method really intrigues me! Yes in reference to vacuuming up HOT stuff, I did that about 20 years ago, was cleaning up around the fireplace, been a day or two since I had built a fire, and all of a sudden a tiny red coal goes up the hose, I shut the thing off, opened the lid and the bag was already starting to smoke, threw it outside, close call!! LOL!! Now here's a question; I have a 429 motor, '69 Merc, for what its worth, and the original pistons look good, tight and all; is there anything I can do to ensure they will live, I probably won't crank this motor much above 5,000, BUT I want it to live, I will use a high-tech coating on the skirts, but what do you think, yeah I know old pistons, but they are CAST pistons, LOL!! (And we were talking about CASTing, right)? Thanks to all! Mike.
Well first they are not really cast like I am making. They are more diecast and are stronger than dirt! (proper name is Autothermic)For myself when flogging a combo I often build with off the shelf cast pistons first. Like when i did the 460 from a 400 mopar that was cast as they are called and we still have those pistons. The 400 cheapie I built is cast. Is cause it is still alive despite several years of hard racing. My slant six dragster has cast pistons. In fact I dont ever recall busting a piston in 40+ years other than from a dropped valve etc due to an over exuburant burnout on the part of one particular driver and that was after about 9 years of such abuse. You know we worry about things that we shouldnt have. All of us , every mother's son, remember when we had some of our first cars and how badly we beat on them. How many ever broke a piston? Not many. Even with pistons like i am making , if wall thickness is proper they are as strong as forged just maybe a wee bit heavier. The strength in pistons is largley due to their alloy . Forged are nice but not necessary till we start squeezing above 7000 and even then I am sure lots of folks have pushed the limits without trouble. If you are the type who has to have all top dollar stuff and bragging rights then ok go for it but i know you are not. Like me you figure out "what do i need , what can I afford and what am I gonna do with this?" Certainly at 5500 you will be 150 years old before you bust one. The only thing they dont like are being too loose and I don't mean an extra thou of clearance but say 010"or.015" clearance (worn out block)they will crack due mostly to excessive heat cause they cant get rid of it because the walls are to far away. . But then no one in their right mind would not know better anyway. Sometimes in this busines being hard of hearing can be an asset. I once did a Ford 300 with six 390 Ford pistons. (050" oversize almost 10 to 1 compression . pin size is the same and they weigh EXACTLY to the gram the same as a stock 300 piston) I heard from all the EXPERTS at the track who have never built a decent fire let alone an engine how dumb that was except he sold that block to another racer after several years of racing and nothing was wrong with it. In fact when i built his new forged piston long rod block it really made little if any difference other than the "cool" factor.That engine was in the top 5 points at the track for several years. Don Don
As soon as I found out these cost $1850.00 a set for the /6 I got out my knife and glue gun. Will pour it tomorow if all goes good. Don
You're a mad man, Don. A MAD MAN!!! IMO the forged piston is really only necessary when you're turning the snot out of the motor, and not because the cast piston is too weak, but because the cast piston is too heavy. The last hot oval racing motor I had built has two ring JE forged high dome pistons in it. They're ridiculously light, something like 390 grams, IIRC. A Keith Black cast piston of the same dome size is almost 500 grams. At 8000 rpm (which is where we ran that motor), that makes a big difference in rod life and also how quickly the motor revs. However, unless you're turning those kind of rev numbers, or you've got some kind of rule mandated induction system choke point (like a restrictor plate or a 2 bbl carb), the lightweight pistons are pointless (and expensive).
I was checking out a set a Mahle pistons today. very light! Yes I think exactly so. With a 4.12 stroke I limit rpm to 6000. With the 3.68 stroke if I ever find a crank I think I could push 6800 to 6900 safely. With the extra stroke I can run a zero deck and still get decent compression and a good burn as well. I think these pistons will stand that in a drag car. I have been working a bit at the mold fixing the last little bugaboos. Yesterday I had a mishap on the slipperey snow and so have not been able to go to the shop except to hobble in while my wife was away for a few minutes. One of the problems running a slant six I think is that the piston with the 4.12 stroke moves a lot faster per degree than a more conventional engine. I know from my days looking after a engine from time to time for a SS/E 428 mustang these engines wanted a very different cam than say a more conventional motor. They are also RPM limited like the slant six is in 225 form. Neither really want to go above 6000 as piston speed in ft per min is above 4000 and into the maybe zone. For some engines that isnt a big problem because there are lots of super duper parts and such available. The slant six isnt real lucky there so I like to make the power with my current engine under 6000 if possible. I need the valve to follow the piston down the bore as fast as possible till it hits full lift and I want that to occur just before the rod is at right angles to the crank throw (max piston speed) Since I am rpm limited I am also duration shy so I have to make the most of all that is availble. One way to improve is to up the rocker arm ratio. These are about 1.65 I think if this casting comes good. I will not know for sure till i make one and check it. Then make a fixture to make sure all the rest are identical . This may help power. I know from experience that is not always so. Sometimes the cam is designed for 1.5 ratio and is already optimized for that and fooling with the ratio upsets the apple cart instead of producues more power. I fooled a lot with rocker ratios in the mid seventies on BB Mopars. I have a hunch the slant six is a different deal and might like it. These rockers I found listed used to sell for $450 which is no wonderful deal but are now listed at $1850.00. Not from me. Not possible. I had toyed with casting a rocker anyway. I explored a lot of lost foam casting last week. I found lots of info from BMW. Even pics of how they make the foam core with guides and seats already mounted in the foam. I found from my own casting of my adapter from a foam core which was vertical in the flasks that the stuff does not move around but where there is sand it stays where you put it despite gravity etc. So I reasoned that is how they get away with mounting all these parts in the foam then pouring it. It is just how lost foam works. On top of that my distant cousin whom I know well in Deutschland is married to a BMW race engine design engineer who is a real neat guy. I have had many conversations with him since I met him. I could ask him a general question if i get in a jam. He wouldnt tell me any secret stuff but he did already have my book in his office when I met him the first time.(first meeting of our two family lines (North American and German) in 292 years) So with that in mind I went to my pals shop today and got a bushing of the right size to fit the rocker shaft and mounted it in the foam core. Tomorrow i will add a smoked adjuster. (Blackened or smoked keeps it from sticking ) and a wear tip for the valve end. I will glue on a sprue (big one too) an a riser at the far end . Then pack and pour. I have two fiddle gigs tomorrow. One in the morning and one at suppertime. (Gotta play for my turkey supper) so everything will have to click to get er done. If not there is saturday. I am going to use piston alloy for this as I have the idea it is better stuff. Malsehen as they say in the old country. (time will tell) Don
7075 is very hard to find the only ppl that use it are aircraft and bicycles I tried to find some while working for a rowing shell company never had any luck the only supply I could find was buying a 1000lb mill run from china alittle more than we needed at the time, not sure what it would be like for casting all I looked at was extruded. Don could prolly melt down an old bike frame or two to get some to try, not sure how the temper would be done after. I think 7075 work hardens ok just don't know how long it takes its been a few yrs since I looked into it. way cool Don keep up the cool work would love to come see you do your casting Paul
The 6000 and 7000 series alloys are solution hardening, which means that without extensive heat treating, they are worse than useless. You can't just melt any old alum and expect it to perform like it did when it was solid. Remelting cast pistons is a fairly safe bet, though I'm still on the fence about how well these rockers will fatigue over time, since he's not going to be able to heat treat them in any meaningful way. Melting any of the wrought alloys is a non-starter though, they simply cannot be handled in the same fashion. Most rockers of this sort are saw cut from extruded profiles and then finish machined. I've seen them made from 6061 T-6, 7075 T-6, and 2024 T-6, all of which are solution hardened and artificially aged. Those are processes that Don just isn't going to be able to undertake. That's not a dig on Don either, nobody short of a commercial short run heat treater is going to be able to undertake such a project. I say try the cast piston material and see what happens. Worst case, he breaks one and the valve snaps shut. A broken rocker is another one of those non-catastrophic failure modes, where he's got some leeway before he does any real damage. It's not like a broken valve spring, where it will lead to a bent valve at the very least, every time.
Don : Have you tried last wax? There are special waxes that are machinable (slowly). That would enable you to make cores on your lathe / mill. My dad maintained molds for a mil-spec foundry that used the process for all kinds of nifty stuff .
Not sure I agree with that last statement.. OK, I don't I've done a lot of lab work with a small oven and a very precise temperature control to heat treat Aluminum with very good results. At the time I was doing research to build a large (250ft+) extrusion heat treatment setup. With a decent oven, maybe a powder coating oven? a good thermometer and a clock you can achieve remarkable results and seeing what Don has achieved so far, I wouldn't put this past him. Within a few miles of my house I've got a die shop and an aluminum extrusion plant, both of which have the small scale setup I describe above and I've used both of them to help me do some heat treating, just ask around, there are more of these setups around then you might think.
I buy it all the time from the local aluminum supplier near Cleveland, Ohio. It is usually in plate form, but they cut what every you want. I just ordered 3pcs. 3/4" x 3" x 30" 7075 for $50 each. Clinton Aluminum, 1-800-497-8421
Only when you look in the wrong places. Since he only needs a small amount: http://www.onlinemetals.com/alloycat.cfm?alloy=7075 http://www.speedymetals.com/c-8361-7075.aspx
According to this page: http://www.steelforge.com/alloys/?alloy=7075 <style>.clear-both { clear: both; }#rfq-btn { background: url("../images/rfq-btn.png") no-repeat scroll left top transparent; width: 130px; height: 34px; display: block; text-indent: -999em; float: right; margin-right: 47px; margin-bottom: 10px; overflow: hidden; }#rfq-btn:hover { background-position: 0pt -33px; }</style> Aluminum 7075 Principal Design Features The 7075 alloy is capable of high strength as developed by heat treating. Applications Commonly used in the manufacture of aircraft and other aerospace applications ... Machinability It is best to machine this alloy in the annealed condition. Machining capability is good and oil lubricants should be used. Heat Treatment This alloy may be solution annealed at 900 F for 2 hours at temperature, followed by a water quench. The alloy may then be given a precipitation hardening (aging) heat treatment. -- see "Aging". Annealing The temperature for annealing AL 7075 alloy is 775 F, holding at temperature for 3 hours. Controlled cooling at 50 F per hour should then be used down to 500 F from which it can then be air cooled. Aging Precipitation strengthening (aging) is done at 250 F for 24 hours and air cooled for T 6. The T 73 temper requires heating to 225 F for 8 hours followed by 24 hours at 325 F and air cooling. Tempering Not applicable. Hardening Hardens by precipitation heat treatment -- see "Aging".
Herb Kephart (ebtm3) posted a pic of the rockers he made for his '28 Chevy 4 on the Chevy 4 thread- I believe he milled his. Every once in awhile I see a set of used roller rockers at a swap meet and wonder if it would be worth picking them up to rob them of their bearings. Any thoughts?
Well I tried it. there are the pics. It has a few issues but I think i can fix them One is I need a riser or vent underneath as as I have a gas bubble void. That is minor . I can add that in a hearbeat. Also my core being made from two pieces sandwiched does not have the integrity I would like so i may buy some thicker stuff or glue it together with clamps. The wear tip stayed put as did the bushing as I predicted. however I need better fit in the bushing holes as the ragged edges were reproduced in the casting. Strengthwise. I think I am ok there but maybe not. A slant six rocker which is actualy a fabricated rocker (welded together) doesnt give trouble so I suspect this is stronger. Yes i had though about machining an extruded length and sawing it up. However you should know that a friend of mine is a prototyper and made the rockers for the Indy cars when they were using the Olds four cylinder based engines. They were CAST at Ceremet in Wellington about 12 miles from me. Investment castings. Anyway I need to re-engneer this a bit. Don
Every day is a new adventure at Don's This is great. When is the aluminum v-12 block casting being done?
Here are some better pics. The two voids are visable in the photos. They are caused be the need for venting or risers in that area. I can deal with that. I want a better quality casting now. What looks great for a lathe part looks like crap for an engine part. Anyway i cut off the sprue and riser and gave it a quick clean up. I weighed it against the steel stocker. It is 6 grams heavier. I was surpised there was any relationship. I am reading and absorbing what you are all saying. i read the aging deal for the trick stuff. i could do that here easily. The annealing would be tougher. You all know a lot more about this stuff than me. Extruded cast etc etc? I dont understand whats the big difference. Is not extruded just cast and cooled through a forming die in a semi moltens state.. Isnt plate just cast anyway. Dont laugh . I dont know. BUT I am gonna find out. If this didnt have the void in it I would finish hone the bushing and pop it on my motor for a real life test. I havent tried lost wax or machineable wax. I am new to this casting thing remember. With my pistons I explored a lot of stuff but I have decided the permanent mold with the baked sand core is the way I am going. It is so close to what i want and the castings are very good i am not going to change. i wish I had a permant steel mold for this.I have a couple of options . One is cast these a bit oversize and machine them to final size more that will give me an unbroken surface. I dont share your concerns about strength. Maybe I should but having swung wrenches for 45 years I have seen some pretty wierd stuff that never gave a seconds trouble. This piece is like a Mack truck in comparison to my thinking anyway. Still I am absorbing as much as I can. Don
Here at work, ( in the aircraft bidness'), we heat treat a bit of 7075, mostly in sheet and plate form, ( thicknesses up to .250), and our procedure is to solution heat treat, in a 920 oven, for up to 75 minutes. Followed by a cold water quench, ( the material is then considered in "w" or "wrought" condition), followed by precipitation heat treat, at 250 degrees, for 24 hours. Barring any problems, it will hardness test immediately after reaching "room temp", to the "T-6" condition. I should point out, that this material, starts out in the " O" condition, which is quite malleable, and after the "quench", it may not be the shape you started out with!!!! We have to sometimes leave a "stiffening flange", in place on your part, then cut it off after the final heat treat, to get your desired part! Got an oven around, capable of a stable 920 degrees???..................You can heat treat your own T-6 aluminum!!!
The 920F steady would be hard (Although not impossible with a bit of thought and construction.) but the precip is doable. I retired early because I was shareholder in a Certification lab. We had a lot of testing stuff there for electronics. Some of which was cross use adapted to our needs. Heat chamber was one I remember trucking in. At the time I wondered what anyone would use something that could go that hot for. We sold that company to a Lab in England. It is now owned by Philips in Europe I think or was at last check. I retired from my own trade (I owned the original corporation but never worked at the lab) and have been spending their money on fun ever since. Now 13 years later the well is beginning to dry up thanks to a bad stock market mostly but i am not complaining. What Gas Pumper said is for me not far off the mark. Or as Vern puts it" The Adventure continues. "
Don: I've got a digitally controlled Kiln you can use. It will hold all your pistons easily. 920 F is not a problem, compared to melting glass.
OK. Anyway I have to be careful. I am easliy sidetracked. I am going to think this rocker arm deal over for a bit. In looking closer at the rocker and the void it apprears to be cause by something in the bushing as the bushing is bad there too. I thought "I bet it isnt bronze but alumibronze." I may have to make some real ones from solid brass. I am tempted to go copper. Stockers are just steel on steel. I could go aluminum steel too. Anyway it was fun intersting and gives me something to mull over. I have to be able to make them all exactly alike. That is my biggest worry. Don
No. Not yet. have some irons in the fire but nothing yet. I can get one at spring carlisle next year but that is the only one so far. Oilite might be good. I think they have graphite in them. I am still working away on the piston mold and stuff. It is so close to perfect as i want it I am happy with the idea. Just a couple of low areas I am hand filing on.
Oilite is sintered bronze that has been vacuum impregnated with oil. This would be a very bad material to attempt casting anything around, as the heat will drive the oil out and contaminate your pour. You could press them in place after the rocker has been cast though. Size the OD for a tight press. Press the bushing into the casting and then hone them to final ID afterward. If you're worried about them walking sideways in the casting, you can key it into place by cutting an OD groove on the bushing and driving a pin or set screw inserted through the rocker and into said groove from above (perpendicular to the bore). If you're dead set on casting the bearing in place, I'd pop for a cored stick of C932 bearing bronze. It's a standard copper/zinc/tin/lead bronze, and should bear the casting process OK. I would still probably bore and then hone to size after casting, so you can true up the bore square to the axis of operation. Another option could be to press ball or caged roller bearings into the castings after they're finished. Might be easier than trying to machine a dozen identical bronze bushings from scratch. Something like THIS perhaps, with a hardened washer on either side for thrust loads and to keep it centered in the casting. Might be worth a look.
The Jalopy Journal
