engine lightening

[Wh33lhop]

Technically, you should have exact same peak hp as without the lightening, but you'll have less drag on the motor, hence more area under the curve... right?

That is not really how it works. Lightening rotational mass/flywheels will get rid of a fixed amount of load. Basically, the faster your car is revving up, the more effect lightening rotational mass will have. So, if you're in 5th gear at WOT at top speed and you're not gathering revs, no difference will be noticed. But, if you're in first gear and gathering revs quickly, you'll notice a difference since the rotational mass/flywheel inertia is a significant amount of the load, and you reduced the mass and therefore inertia of said rotating assembly. If you're in neutral, the only load on the engine will be from rotational mass/flywheel inertia, and you'll notice a big difference.

Like a flywheel. Mebbe not.

Exactly like a flywheel.

[JJ1]

Aside from using the mass to dampen or absorb harmonic vibrations in the cap, I would think that the thicker portion of the cap resists deflections when the engine is at tdc. The inertial forces of the piston flying upwards will be resisted almost entirely by the rod cap. By reducing the depth of that metal mass on the cap, you are also reducing its moment of inertia about its major axis of bending. Because the maximum bending moment is at the center (mid-span) of the cap, I would not remove mass from that area. Instead, remove from each side (right next to where the cap becomes very thin). You would effectively be making a beam of varying moment of inertia (Ix) having the greatest Ix at the point of greatest load (mid-span) and the smallest Ix at the point of smallest load (supports).

So round off the cap as opposed to just milling the end. Right? Sounds good.

[structured]

Like this:

[structured]

i really thought about it. but i coud not get a straight answer from anyone as to how important the blocks were or what their exact purpose was.
absorbing harmonics to a point is what i was thinking.
i would welcome any actual answers as to the purpose of the giant freekin block at the base of the rod caps.

i might see if i can mill .100 or so off and see what happens.

Aside from using the mass to dampen or absorb harmonic vibrations in the cap, I would think that the thicker portion of the cap resists deflections when the engine is at tdc. The inertial forces of the piston flying upwards will be resisted almost entirely by the rod cap. By reducing the depth of that metal mass on the cap, you are also reducing its moment of inertia about its major axis of bending. Because the maximum bending moment is at the center (mid-span) of the cap, I would not remove mass from that area. Instead, remove from each side (right next to where the cap becomes very thin). You would effectively be making a beam of varying moment of inertia (Ix) having the greatest Ix at the point of greatest load (mid-span) and the smallest Ix at the point of smallest load (supports).

[der affe]

Technically, you should have exact same peak hp as without the lightening, but you'll have less drag on the motor, hence more area under the curve... right? Like a flywheel. Mebbe not.

Beautiful work btw...very, very thought provoking.

sort of, it will take less HP to move the lighter mass, but it more importantly will make it rev faster to make the hp faster and be able to put you into the rpm range you want (powerband) quicker.

not talking huge hp#'s. mostly it makes the engine more enjoyable to drive and twist up.

so yes it is like a lightened flywheel in a way, but a lightened everything.

[der affe]

as long as they are peened after then itll be fine. what about the fat square balancing chunk on the cap? if i remember correctly, back in school we removed some of this to lose the weight as well. Also i think it was my machinist who was explaining that at 2000rpm a 1/4oz weight on the end of a crankshaft can multiply to 15 lbs, and at 7000rpm its like 150lbs.

since i didn't do a stroker i used s50 rods, which were 100g lighter per rod than the stock m20 and eagle rods. Ill tell you the engine revs so much faster and is relatively more "responsive". couple that with an al fly and the engine will respond crazy haha.

anyhow, good work!!

i really thought about it. but i coud not get a straight answer from anyone as to how important the blocks were or what their exact purpose was.
absorbing harmonics to a point is what i was thinking.
i would welcome any actual answers as to the purpose of the giant freekin block at the base of the rod caps.

i might see if i can mill .100 or so off and see what happens.

[M3 euro ltw]

...
add all the rotational parts being lighter (crank, flywheel, rods, to a very small degree pistons) and balanced to zero, you end up with a smoother running, faster reving, long lasting motor. that makes a little extra hp because it is moving around less mass.

Technically, you should have exact same peak hp as without the lightening, but you'll have less drag on the motor, hence more area under the curve... right? Like a flywheel. Mebbe not.

Beautiful work btw...very, very thought provoking.

[chris00]

In picture number 3 it looks as if the rod is bent? Is it just the angle of the picture? Good work by the way, it looks like its taken a few hours!

[lennon]

good to see those pistons going to good use. im doing similar stuff with the rods and pistons on my 24v motor (slowest build ever)

[blueapplesoda]

as long as they are peened after then itll be fine. what about the fat square balancing chunk on the cap? if i remember correctly, back in school we removed some of this to lose the weight as well. Also i think it was my machinist who was explaining that at 2000rpm a 1/4oz weight on the end of a crankshaft can multiply to 15 lbs, and at 7000rpm its like 150lbs.

since i didn't do a stroker i used s50 rods, which were 100g lighter per rod than the stock m20 and eagle rods. Ill tell you the engine revs so much faster and is relatively more "responsive". couple that with an al fly and the engine will respond crazy haha.

anyhow, good work!!

[dr.gonzo]

This is the first time I have ever heard of someone doing this. Is it because the rods are so overbuilt?

[delatlanta1281]

Awesome man! i am impressed.

[der affe]

went from 601.4 grams to 563.7 grams witha little more hand finishing to do. i am hoping with balancing and the final hand finishing i will end up 30 grams lighter. that may not sound like alot of weight, but multiply it by 6 and realize that it is rotating mass which is more responcive to weight loss.

add all the rotational parts being lighter (crank, flywheel, rods, to a very small degree pistons) and balanced to zero, you end up with a smoother running, faster reving, long lasting motor. that makes a little extra hp because it is moving around less mass.

[dr.gonzo]

Great build, how many grams are you able to remove?

[Stephen]

Wow, awesome. Id love to do a build like that