Honda D Series Forum banner

tungsten crankshaft

18532 Views 185 Replies 42 Participants Last post by  007
so i understand that people are using tungsten balance weights for internal balancing of the reciprocating / rotating assembly. has anyone ever heard of a tungsten alloy or pure crankshaft? has anyone ever heard of anyone using tungsten cores inside the counterweight section? the idea here is that, the more weight you have spinning the more torque the engine will produce. tungsten weights 19.25 grams per cubic centimeter. any thoughts anyone?
1 - 20 of 186 Posts
from what I've read so far, they use tungsten because it is extremely dense, hence small pieces of the metal can be used allowing for greater precision.

a full tungsten crank would be extremely heavy. I don't think that will mean more torque. it is the same as a light / heavy flywheel in that the crank will not *create* any torque; merely store momentum when it is being accelerated, do nothing at steady speed and release said momentum when it is being decelerated. it is going to be a bitch to accelerate.

a fixed amount of torque will impart a fixed momentum. momentum = mass * velocity.
if you increase mass and keep momentum constant, velocity has to decrease. so for ever unit of fuel burnt, a hypothetical tungsten crank will rotate slower than a steel crank.
Ive never seen tungsten used for anything other than a weight or used on something that gets super hot. I know its has a super high melting point.
If Im not mistaken it is very hard, but I think its also brittle.

But yeah, that would make for one heavy ass crankshaft, which would make for a slower car.
Lets say you have a 4 banger with a 30 lb steel crank. The same crank made instead out of pure tungsten would weigh 75 lbs... lol
This is so stupid it's hard to believe it's not a troll.

How on earth can crank mass, which is rotating mass, influence power or torque. If it did, we would all run super heavy flywheels and wheels instead of cut down steel or aluminium parts.

Tungsten is very hard and quite brittle. Brittle cranks are not nice.
I have a tungsten watch. Heavy bastard, I get a little nervous if I'm wearing it around water-I'm going straight to the bottom if I fall in.

I'll tell you, tungsten is some really hard metal, I can't scratch it-it did chip(I dropped it), but its never been scratched.
  • Like
Reactions: 1
It's used in light bulbs as a fillament and yes its really heavy and expensive. I work with it everyday because of its high melting point.
good news everyone! i have come up with a way of explaining this in terms you might understand. so consider the following, lets say you have a projectile like a bullet and the bullet weights 40 GR or grains and its moving at 1200 feet per second when it hits the target the 40 Grain round expends 128 foot pounds of energy into the target. now lets say you have another projectile that weights 400 grains and is moving at 1200 feet per second it would expend into the target 1287 foot pounds of energy. so what does this have to do with a motor? so the projectile is the crank shaft, the feet per second is the engines RPM and the Grains would be the weight of the crank shaft. now here is the catch. a crank that weights more than a stock crank would not rev up as fast as the stock crank, if you had the same amount of air/fuel and the same compression ratio. however it would make more torque or turning force. its some really basic physics... the more weight or mass you have spinning the more torque the motor is going to produce. as for tungsten being very brittle, it has a ultimate tensile strength higher than most carbon steels. i have talked about this very subject with someone who is ASE L1 certified and we are both in agreement.

keep in mind that all the centrifugal mass after the crankshaft is going to be parasitic and cause a loss of torque and HP. not to mention the loss do to friction.
See less See more
good news everyone!
I see what you did there! :shifty:
What I would be worried about is what all that extra weight would do to the crank bearings.
I understand what your trying to say. I also understand you are wrong in fact. Higher inertia does not increase torque. Higher inertia can carry the crank over between power strokes to give a smoother delivery of power, but this is hardly a problem with a 4 cylinder engine that idles at 800 or more rpm.

It was a problem with 1 and 2 cylinder engines that peak reved at 1500 and idled at 40 or 50 rpm. They fixed it with a steel or iron crank and a very heavy big dia flywheel
Extra mass, thus inertia will not create more torque from an engine. It will however, reduce transient power output. Steady state will not be affected, technically. Torque as measured at the output shaft is created by the throw of the crankshaft and the pressure generated in the cylinder.


The F, force, is generated by the pressure in the cylinder times the piston crown area. The r, radius, is the crankshaft throw or 1/2 the stroke of the crankshaft.

Your use of the projectile analogy is incomplete. If you take two bullets with different masses given the same muzzle velocity, yes, you will have a greater impact energy with a bullet that has a higher mass. Think KE = m * v^2. The problem lies in that it takes a greater amount of energy to accelerate the higher mass bullet to the same muzzle velocity as the lower mass bullet.

There is simple physics, then there is oversimplifying physics.
so if we have a 30 lb crank shaft spinning at 3000 rpms and the exact same crank but double the weight, 60 lb crank spinning at 3000 rpms the 60 lb crank will produce twice as much torque... to as for the weight of it giving hell to the bearings, a fluid is not compressible and the crank, con-rods, piston, camshaft, valve stems, rocker arms all ride on a thin film of fluid that's always circulating.
Sure. You're right. Do it and prove the establishment wrong.


Sut is also the only metric needed to judge whether a material is suitable for use as a crankshaft as well.
of course you would need a larger "bang" to accelerate the heavier crank shaft at an equal velocity to a lighter crank shaft. but the heavier crank would impart more torque or "turning force" to the wheels.
There is simple physics, then there is oversimplifying physics.
good quote
yeah it's not even the spinning of the crankshaft that generates the torque so much as the explosions forcing it around. just so you know. it would work well in a flywheel powered car though. and that might be what they use.
i like how everyone is so quick to be like Aww fuck its rusty again with is trollish questions... trollish only because you don't have a decent answer.
flywheel powered car? you mean a rotary engine?
i did take this into consideration, but there is absolutely no physical reason for it, unless it would be used i a giant stationary piston generator type thing. no one likes race cars to have any more mass then they need too. end of story.
If you can't explain it simply, you don't understand it well enough.
Albert Einstein

^ good quote, from a REAL scientist
  • Like
Reactions: 1
flywheel as in a regenerative flywheel that captures energy while breaking and out puts it when they accelerate. quite an ingenious idea there is a couple video's of a some type of race car that uses one along with a normal piston engine.
possibly the future for racing
that and the delta wing hopefully

if you can explain it simply but don't know the more complex theories and don't take into account the major variables you will not get any useful data.

this isn't hard core theory that needs is being over thought.

it's good to know that people on here are thinking and for that i'll give rep to you, but sometimes you have to realize that you made a mistake. i have made many but don't let it stop you from coming up with idea's just let it continue to other area that it might be more useful in.

note for all you newbs: riding a dirtbike with a broken thumb not a good idea
  • Like
Reactions: 1
so if we have a 30 lb crank shaft spinning at 3000 rpms and the exact same crank but double the weight, 60 lb crank spinning at 3000 rpms the 60 lb crank will produce twice as much torque... to as for the weight of it giving hell to the bearings, a fluid is not compressible and the crank, con-rods, piston, camshaft, valve stems, rocker arms all ride on a thin film of fluid that's always circulating.
You will have more STORED energy due to the weight. If the engine is a steady RPM unit this is not bad once started. If it is a power plant that sees a 4000 rpm powerband, not gonna rev very well.

patprimmer, you thinking of the one hitters that powered farm equipment and pumps?
1 - 20 of 186 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.