has anyone ever tried this modification?

mew905

mew905

New Member
I'm looking for ways to lighten up the crank and broaden the "sweet spot", I figure the lighter the piston, the broader and lower (depending on the balance) the vibration free sweet spot should be. ANd I got thinking... What is the con rod made of? it doesn't look like aluminum, perhaps iron or steel? Anyway, I got thinking, has anyone ever tried removing the majority of the middle of the con rod (the part that resembles an I beam) or am I just being crazy? I figure with pistons this small and strokes so short, it shouldn't be an issue, but I could be very wrong, but it'll reduce the floating mass on the crank, allowing balancing to not only be easier, but take much higher RPM's to throw the balance out of sync. I figure with ~180lbs max upward or downward forces on the piston, if it's steel, it'll be more than strong enough, if it's aluminum, it may be questionable. My goal is not only to reduce vibration, but also the more RPM's I can get out of it, (my bearings are SKF high RPM industrial bearings, so dont worry), the more speed.

Has anyone ever tried it before? Does anyone know what the rod is made of? Would it be strong enough to hold up to the pressures if you remove the center of the I beam part? (essentially making it a = beam)
 
My guess is the effort wont be worth the results, it's some sort of hardened steel, it's even a weird colour, like copper.
Not only that but you won't be making the rod any stronger, but increasing the likelyhood of failure.

You got me wondering though was is the force in kg's or lbs this rod and piston endure, 180lbs,is that right?

Anyway, i've heard of guys on here wearing out drill bits (and themselves) trying to drill oil channel holes in this connecting rod.
 
180lbs max upward forces, downward is something like 176lbs. That should be nowhere near what the steel can handle, provided it is steel. I thought I read some stories about the con rods breaking but decent steel IIRC should be able to handle around 5000-10000PSI, assuming the con rod is only around 1/2 a square inch per lateral arm, that means it should be able to handle close to 2500 lbs of force without breaking, not just 200. But I'm no engineer, this is assuming the forces will be equal on all sides and such. Not to mention heat, but on the intake side the motor actually doesnt even get hot enough to melt modeling clay, its the explosion and exhaust that get hot (and by radiation/transferrence, the jug
 
Drilling holes in the connecting rod is a very bad idea.
The only mods I would consider would be shot-peening it for more strength, not less.
Messing with the rod is not worth the risk of failure. Balance the crank correctly and leave it at that.
 
ha! Do it and let us know the results! ;-)
actually I think the pressure on it is really high because of the pressure created by combustion.
 
Thats one thing im worried about is the blast power, the 180lbs is only from piston speed, then compression is 90psi, not sure what kind of pressures it'd be seeing with combustion though. Im thinkin it may not be worth it, as stated, the weight gains would be minimal and the strength severely comprimised, ill stick to cutting the piston, now that i have reeds
 
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