Pistons
- Thread starter PAINFULRM
- Start date
Yep, one or the other
Well now Rich, I believe your answer is somewhat short sighted. There are other piston manufacturing methods that have been successfully employed. There are a large number of experimental pistons machined out of a solid block of material. There have even been wooden pistons! Carbon composites have been tried as have carbon carbon pistons. Iron (yeah I know it was cast) was used as was machined steel. A small engine such as the 50cc one in question would, in my opinion be a perfect test mule for new designs. I'll be willing to bet that a competent machinist could fabricate a functional piston out of materials at hand. Even welding is not out of the question (ask me how I know!)
Yeah, yeah I know some of the mentioned materials were used in 100 RPM engines and some were for steam. However that does not change the fact that one could machine a piston out of readily available materials. The choice of alloy may allow thinner and lighter designs. One of the problems (in the past) with cast pistons has been the tendency to crack. Years ago, the problem was so bad piston manufacturers resorted to steel inserts!
Chris
I forgot to mention that pistons are not perfectly round or true. The top gets hotter and expands more, so is generally smaller in diameter. The piston pin area generally has more and thicker material, causing greater expansion as compared to the thinner areas. These areas are generally smaller in diameter also.
Yeah, yeah I know some of the mentioned materials were used in 100 RPM engines and some were for steam. However that does not change the fact that one could machine a piston out of readily available materials. The choice of alloy may allow thinner and lighter designs. One of the problems (in the past) with cast pistons has been the tendency to crack. Years ago, the problem was so bad piston manufacturers resorted to steel inserts!
Chris
I forgot to mention that pistons are not perfectly round or true. The top gets hotter and expands more, so is generally smaller in diameter. The piston pin area generally has more and thicker material, causing greater expansion as compared to the thinner areas. These areas are generally smaller in diameter also.
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endosports
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- Jan 10, 2002
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That would be way to easy!;)
Yeah I guess I must have missed the part where he said he wanted to reinvent the wheel. I probably should read more carefully. :silly:
When you look at the number of great advances that have come that way you can't discount it as a possibility. Given the high levels of complexity that come with piston design it seems unfair to goad someone into burning money and time for our amusement when the Wiseco catalog has an inexpensive and completely workable solution today.
While I don't doubt there are advances still to come in piston design, the general lack of change over the past 50 odd years tells me that the basic designs we have are doing pretty damn well. :thumb:
Moto Squid
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- Jul 22, 2002
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the good ol' Rich no b/s post strike again :scream:
If you just feel like making pistons wanna make two for a '74 Ski-doo RV340?? Seriously though...that PW50 piston has got to be available in a catalog, probably kinda cheap too. It's not as if you've been left with no other options but to make one.
- Oct 13, 1999
- 2,807
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Here's a perplexing question along the same lines. Liqui-Forge and Squeeze-Cast are the same manufacturing methods, but is the finished product a forging or a casting?
To add some more info, it sounds like Family First wanted to make a piston from billet. Since billet is nothing more than continuous-cast bar, the piston would be made from a casting.
I wonder if the piston he is trying to produce is cam-ground?
To add some more info, it sounds like Family First wanted to make a piston from billet. Since billet is nothing more than continuous-cast bar, the piston would be made from a casting.
I wonder if the piston he is trying to produce is cam-ground?
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Painful,
I believe the expansion characteristics of the material would have to be considered to size it for your bore. (low silicon cast expands less, high silicon forged expands more & takes a bit longer for thermal equilibrium to occur). Ever played with head designs?
you must work the graveyard shift too!
I believe the expansion characteristics of the material would have to be considered to size it for your bore. (low silicon cast expands less, high silicon forged expands more & takes a bit longer for thermal equilibrium to occur). Ever played with head designs?
you must work the graveyard shift too!
I suppose billet would be the only way to machine a piston from aluminum without a mold. Ever notice the grain in a forged piston? You would have all kinds of stress risers if the raw materials had a grain to it. I know- make it from a small chunk of titanium, port, pipe,carb the top and balance the crank so it spins like 12000 rpm reliably. LOL Maybe you should just call a Wiseco dealer. Actually this brings up an interesting debate. I've seen forged pistons crack skirts more than cast. They expand way more so they run loose. Cast pistons are set in a pre-expanded mode so they run tighter. Hypereutectic pistons have as much silicone and scuff resistance as forged with cast type expansion. [Aren't Pro-X pistons all hypereutectic?]Given the power characteristics of a 50cc weedeater sized engine whats better?
All metals have some type of grain structure. A forged piston is shaped from a billet of aluminum that was cast. During forging the high pressure and heat allows the grain to "bend" and compress, this is part of the reason a forging is strong. Billet starts with the same chunk of aluminum and then machines it, cutting the grain and creating stress risers. In bends and curves the grain of a forging compresses together. In a billet piece the grain structure is uniform, but this means the curves and bends are much weaker because the curves are cut into the grain. A cast part has a grain structure that "flows" relatively evenly through the part. This is also why a cast or a billet part will expand less than a forging.
A billet part will never be stronger than a forging of similar material. Depending on the casting techniques used the geometry of the part (and the quality of the billet that was used in the billet part), a cast part can often be stronger. The main advantage of billet parts are cost to make low quantities(it's cheaper for most as you don't need a foundry) and the ability to make intricate shapes that a casting or forging couldn't make. Billet machined parts move quickly from a CAD station to a machining center. Billet can also give a nicer finish.
That's probably more than you guys wanted to know....
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A cast piston beats a forged piston when it comes to tolerance control, and how much it grows with heat. A forged piston has residual stresses in it that make it enlarge and possibly "warp" more than a cast. It also rattles more on start up, as the bore has to be machined to a larger size to allow for the greater expansion. There are also the ring sealing issues due to the dimensional instability. The upside is that a forged piston will always be the strongest.
I don't know much about Pro-X other than what I see on their website. They may or may not be a hypereutectic piston. If it is a hypereutectic, the dowside is that a hypereutectic piston is more brittle than a forging and is therefore very sensitive to detonation.
But pricing doesn't always reflect cost of manufacture or technological superiority, it just might be paying for a larger marketing department. :debil:
I don't know much about Pro-X other than what I see on their website. They may or may not be a hypereutectic piston. If it is a hypereutectic, the dowside is that a hypereutectic piston is more brittle than a forging and is therefore very sensitive to detonation.
But pricing doesn't always reflect cost of manufacture or technological superiority, it just might be paying for a larger marketing department. :debil:
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