The point of this thread is to retrain your brain as to how you view a part that you need... "can I make it?" should be one thing that should come to mind. Anyways, I have an oddball old car that only had 2 hubcaps, and a few years of searching, only came up with one in decent condition. I thought about casting some from aluminum, or maybe brass, but they would be heavy and would need a good system to keep them on the wheel. The original caps on most all old wire wheels were a lightweight stamped steel base, but with a thin chromed brass, stamped "skin", that was crimped onto the base shell. Some restorers have the basic skin shaped by "spinning" a thin sheet of brass on a lathe of some sorts. Sounded like it takes a lot of skill. Plus, then the old small detailed emblems need to be cut out of old skins, then silver soldered into a precut hole in the new skin. Way to difficult to me. Here is what I had for caps, and the skin removed from the cap base shell.
I don't recall when I first heard about hydroforming. I looked on the web and youtube for hydroforming ideas. Not much out there in detailed info, but I did learn that hydroforming can be done with water, like a pressure washer at 2500PSI, or hydraulic oil pressure from a pump, and also, a piece of rubber that when compressed, acts like a fluid that can form parts in a die. The main point of the hydroforming with a die, is that only one die half needs to be made. If I were to press these skins like the factory did, I would need to make 2 perfect dies; male and female, slightly sized differently to make up for the material thickeness being stamped. So, I came up with an idea to make the female die I will need. I found 1/2" and 5/8" thick round steel plates at the local scrap recycle place. The "male die" will be hydraulic oil under pressure. The female die will be the 5/8" plate cut into on a lathe. I knew I would be almost cutting through the plate in the very center at the tallest part of the skin, so I thought about welding the smaller thicker circle to the 5/8" plate to beef it up...then grab the small circle with a lathe chuck.
Thinking a bit clearer, I decided that welding the small circle would be a bad idea, as I'd never be able to quickly "rechuck" the die in the lathe again in the same spot, if the die needed a bit more machining for some reason. I decided to use a 10" face place on the lathe, drill 4 holes in the faceplate, drill and tap 4 holes in the die. Then make an index mark on the faceplace and die, in case I needed to remount it later. Much more smarterer idea Now it is just machining the basic shape into the die, then polish with the lathe on high speed, with a 4.5" angle grinder with an 80 grit flap disc. I'm not a chainer with bucks..the lathe I got in trade for 3 hours of body & paint touchup on a friends wifes car ... and I already had the correct paint...so it was a good trade.
Ok, on to the plate that will cover the main die. It needs to clamp the sheet of material tightly, it also needs to seal the hydraulic pressure. I thought about a copper O-ring..how the hell could I make or find that? Then I thought about using the material in the same way that a copper brake fitting washer is used for brake fluid pressure. If it could possibly work, I would need to cut into one of the plates to make those concentric grooves or ridges. Too sharp might cut the material like a die cut, too dull might leak... So, it was just fly by gut when cutting the cover plate which is 1/2" thick.
I figured I was done with the die parts, so on to the pump, and test it.. The oversized Simplex pump was attached to a big 50 ton jack for dozers and heavy equipment. Found it at the scrap place 2 years ago for dirt cheap. I also had a Swiss made 3000 PSI hyd pressure gauge I bought on ebay years ago for one of my son's bucket tractors. I hooked the gauge dead-ended to the pump, and it easily went beyond the 3000 mark.. Good to go. so I thought, but thankfully I started thinking about the "total" pressure applied to the die bolts. It really is like a wood splitter or brake cylinder...meaning that the 3000 PSI needs to be calculated by the total square inches in the die "diameter". My car uses very large hubcap diameter compared to Ford or Mopar; mine are 7-1/4". I did the online calculator and was shocked to see that at 3000 PSI, the spreading force of the dies was 120,000 POUNDS! I originally planned on 8 bolts. Yea right. The size of those precut steel circles limited my bolt diameter to 5/16" max, so I had to get online bolt strenth charts to find out how many bolts I'd need for a huge cap like this. It was 24, with the grade 8 at about 5000 pounds each. Best place was Tractor Supply, grade 8 bolts and nuts by the pound = about $5.50 for 24 of each. Almost ready to give it a try... but what material?
I never had much confidence in working with thin brass, and we all know it cracks with age, is tougher to press than copper, etc.. So I searched around local for copper flashing. Home Depot has big rolls at $140, and the local scrap does not resell copper unless you are right there as it comes in. Too valuable to stock for fab customers. So online, I found BasicCopper, a good site. It had mini videos showing a person handling, flexing, and bending different thicknesses of copper sheets. I settled on .016 rather than the .022 thickest, as I was unsure of getting a sharp press detail if it was too thick. Got a sheet in a roll, enough for 7 skins for less than $50 shipped quickly. Made 7 newspaper patterns in one cutting, to get my best laypout on the sheet. They give you extra copper, as the way their machine rolls it, it leaves a kink at one end. I screwed up my first attempt at pressing so I had to use one circle that had a kink. Shit, that kink means nothing when hydroforming...as I found out
Start off with so .020 aluminum, like you'd find at H'pot...Then see how it goes, you might have to make the "mold" have sharper detail to get the metal to shape...
Back up a bit; I knew from the start, that the very tiny, well detailed center emblem was impossible to form with this method. I did reverse math on just one letter in the word NASH, at 1/8" square, one letter will only get roughly 50 pounds pressure on it! Strange how this PSI stuff works in reality. So, early on, I decided I'd need to make male and female mini-dies to mechanically press that emblem into a new copper skin that I hydroformed. But I really need some piece of the emblem shape in the main die, so that I can "feel" when both mini-dies are lined up in the press or bench vice. Well, I made a error. I tried to use one original brass emblem recessed into my main die. But how to support that thin emblem into a recess? I tried using fibergass resin gel, but apparently had many voids that crushed under hydraulic pressure later... Also, the oil pressure and gauge holes in the top plate were drilled in 2 spots where I could peek in there to see if the details were forming, without taking all 24 bolts out. Well, the main part of the first attempt is good, but the area around the emblem is distorted because of the voids in the resin.
Forgot to say we had some leaks at around 1300 to 1500 on the first try. Why? because of the massive spreading force, that top 1/2" plate was bowing up, and that lifts the sealing ridges. Very odd is that if it starts to leak, it drops pressure to a certain point where the seal starts to seal again, and the pressure will hold forever at the lower pressure...go have a coffe, and it will still be holding. That is weird. So, off to get another plate. Now we are up to damn near 1" thick...and that still bows at higher pressure! I finally stuck the whole deal in a leaky 20 ton press, to push on the center of the die, while trying for higher pressure...I only got to 2300 PSI. But I don't think it needs that much. I still have 4 to do, so I will see how they look at 2k PSI. Anyways, I removed that brass insert, remachined the die to leave just a faint outline of the emblem...and pressed these out:
Ok, lets get whack and make some emblem dies My son and I just installed a scrapyard wood boiler in the shop this winter, to heat the house and shop. (yes the boiler came from the scrap place)So I got me a place to melt metal 24/7 Well more mistakes. I tried to pour melted aluminum over another original thin emblem. It was too hot and melted part of it. So online charts said zinc is lower melt, so I tossed in some chopped up VW carb in the kettle Worked like a charm. made a male and a female die, then did some test stamping in the bench vice. (I did this step before I decided on copper)
instead of fiberglass resin, how about lead? couldn't you just melt it in there. I'm really diggin' this tech btw!!!
Here is the skin crimped onto the old shell, and on the car, ready for plating. I might try a "copy chrome" type plating, maybe. It is a legal home use electroplate, but subsitutes the hazardous chemicals with another safer one. I am thrilled with the project; I can't believe it worked so well. I can't believe I made a F'ng hubcap I forgot to take pics of the crimping. I thought it would be the hardest part. It was super easy. I held the cap upside down in my lap, held one side in place, and used a body hammer to "smear" or squish the edge over the old shell. Kind of a side swiping hit, like moving a high spot or stretch. You tinbenders know what I am trying to explain. It was easy and very neat appearing. That's it, I think. Oops, I forgot to say that I think I read where a handheld grease gun can do 2000 or a bit more PSI, if you don't have anything else.
^ McGurk; this process that I did is not at all dangerous IMO. I did worry about a high speed stream of oil coming out as I was planning, as well as bolts snapping.. But as far as bolts, it is all on the net; 3 tables for a bolt, Proof I think, is test strength without any permanant change in the bolt, Tensile? I think, is where it holds, but has deformed (not reuseable), and the Yield, which is where it snaps. I was well under the total working strength of the bolts at the Proof level, I was nowhere near the fail level. As far as a dangerous fluid leak; it did not ever come close to even anything over a dribble down the side. There is so little volume of oil in the die cavity, that even a few drips will drop the pressure by 500 PSI.
I have read up on hydroforming as its quite interesting to me... From what I've read one of the built in safeties of the process is that once a leak develops, assuming you're using a non-compressible fluid like water and not air, is that the pressure drops. You're much less likely to get an explosive sort of situation like you would with compressed air or steam.
been around some hydroforming in the past, great tech. A set of caps with HAMB instead of Nash would be very cool, probably have to ask permission first.
Didn't know a damn thing about hydroforming until now. That is really cool. Nice job, thanks for taking the time to share the process.
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