weightless crankshaft

[AWD-TSI]

So like the title says, Has anyone had any experience with or has used them? Im gonna build a 2.1 destroker and was wondering if anone has anything good or bad/ pros and cons to say about these. The ones i have seen are from jacks transmission.

www.jackstransmissions.com



Thanks again

 

[BogusSVO]

looks good, never used one, doubt it be much good for the low end or to be used in a Daily Driver.

Not alot of spinning mass to get you off the line, but, if your building a race only car, for AutoX, scca or along those lines, it ought to work well

 

[AWD-TSI]

ya its strictly for a drag setup. im gonna run big boost and lots of revs. I have a HX-55 Holset waiting for this build. Just wondering if any one on tis forum had used one. Ya figured my torque down low would be non existent.

 

[Jeff99GS]

If it is strictly a drag car then it should be okay. The counter weights help the engine keep up momentum of the revs. So with NO weights the engine will REV fast, and also DROP revs fast. Similar to the way a Formula one Race car revs...but not so extreme. Also a Lightened Flywheel and Removing the Balance shafts will help the engine rev faster.

Revving fast is a good thing, however dropping revs fast is NO good for street driving. It makes it much harder to shift. Sometimes the revs can drop so fast that the engine will stall.

F1 cars rev fast due to an incredibly short STROKE as well as lightweight pistons/rods/crank/flywheel. They also have Pneumatic Valve springs!! Yes thats right...they use AIR powered valves springs!! Anyhow...
I say go for it as long as your not planing on any street driving.
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/R1jkrRsCuDU&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/R1jkrRsCuDU&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

 

[red_devil]

Going off topic but I belive that F1 cars no longer have a flywheel at all.

 

[Jeff99GS]

Going off topic but I belive that F1 cars no longer have a flywheel at all.

Probably not haha

 

[AWD-TSI]

alright thanks for the info. if any one else has any info or experience please feel free to post.
thanks again

 

[Darkmood]

Jack's a good guy and I know there are plenty of people that swear by his work. He's on here as "JackM". He's also really great at getting back to you if you have any questions for him.

I'd definitely say go for it on the crank if you don't mind losing low-end torque. I know there are a few Colorado guys running them and they seem to like them.

 

[pboglio]

Never used one. However, an article in racecar engineering talks about this. Not good for main bearing wear since by doing this you are eliminating a counterweight and now the main bearing(s) have to take the inertial load instead of the counterweight helping to offset it. F1 cars have counterweights last I saw. My subaru does not though the configuration is a flat four and the opposing pistons/rods are the counterweights. I wouldn't do it.

 

[JayRolla]

Jack has ran one in his road track car on a 16g I believe. He never had any bearing wear issues and it worked out great.

 

[AWD-TSI]

so you think there might be premature wear on my main bearings?

 

[Jeff99GS]

No I dont think there will be. I would Trust Jacks Transmissions. If he says he had NO premature bearing wear then I would take his word for it.

Like the one guy said, its NOT a V8 that would need counter balancing to stop vibrations. As Long as You get everything balanced and within clearance, I would think you'd be okay.

 

[AWD-TSI]

ok cool. Thanxs again for all the guys.

 

[Defiant]

Well, their first statement is about completely incorrect:
"A crank with no weights will vibrate like crazy. FALSE! Anyone that says this has no clue how an inline 4 cylinder works. An inline or opposed 4 cylinder engine is a naturally balanced engine. This means that you have two pistons going up and two going down. The weights on 4 cylinder cranks are there for low end torque, not balance. On an engine with a V configuration this would be true as the weights in V style engines are there for balance and are counter weights. Since our engines are not a V style (like a V8) you don't need them."

An inline 4 is not naturally balanced. You don't get that until you either run a flat-4 with interleaving connecting rods, or a straight six. Inline fours are subject to secondary imbalance, which is what the Mitsubishi-patented, Porsche-licensed Silent Shafts are to combat, and why inline fours don't make it to 3-liters.

I'll be curious to hear how these pan out.

 

[JayRolla]

This is not something new. Its been done before. The first one I saw was at his shop and it was over 4 years ago.

 

[jdombrow]

bringing up an old post but has anyonehere tried them or can anyone who has leavesome feedback, I was looking to get one on a street car for easier revs, would this be like a lightweight flywheel, more hp from less rotating weight,

 

[4g64fiero]

I would never run a crank that couldnt account for the forces the pistons and rods put on it.

Eagle Specialty Products, Inc. - Do I need to balance this crank?

 

[jdombrow]

that has no effect, do a little reasearh, were not a v8.

we have naturally balanced engines one thing goes up another goes down. as long as all rods and pistons weight the same its considered balanced as far as crank goes ours dont need them like jack's said and there a very well known and reliable vendor and hes been selling these for awhile so I would trust his work. just hoping for a review

 

[4g64fiero]

Ahhh yeah I got mystified by that moving jif but I see now. Those weights are just for drivability.

 

[spoonman]

I am glad that some one brought this thread back, I want more guys to discuss this topic.

The counter weights are not in place just to keep the engine turning at low RPM's but to neutralize the effects of torsional vibration caused by the engine's combustion stroke. Although a crankshaft feels tough and certainly looks strong it does flex and bend. Every single combustion stroke twists the crankshaft ever so slightly and then it untwists. In an inline-4 engine the counterweight is in the exact opposite position as the torsional vibration energy from combustion. The acceleration of the counterweight's mass counteracts the twisting of the crankshaft. Without this opposing mass from the counterweights the crankshaft will actually try and jump out of the main caps. This unbalance will KILL bearings, your block might crack, exploded crankshaft anyone. Another point to be made is that this could actually hurt power. Why? Because an unbalanced rotating assembly does not want to rotate! it wants to reciprocate!

They don't put on counterweights just so your butt dyno doesn't feel it, the proof is that they are producing V-6 and I-4 engines.

Lets see some engineers, machinists, and wisemen in here!

 

[Defiant]

we have naturally balanced engines

No. Inline fours have secondary imbalance. That's why we have Silent Shafts.

The counter weights are not in place just to keep the engine turning at low RPM's

That's the flywheel's job.

but to neutralize the effects of torsional vibration caused by the engine's combustion stroke.

That's the harmonic balancer's job.

Although a crankshaft feels tough and certainly looks strong it does flex and bend.

Ask a shop to let you watch how they straighten cranks. You'll be amazed at how little it takes. That's why we have five main bearings.

Every single combustion stroke twists the crankshaft ever so slightly and then it untwists.

Which the harmonic balancer combats.

In an inline-4 engine the counterweight is in the exact opposite position as the torsional vibration energy from combustion. The acceleration of the counterweight's mass counteracts the twisting of the crankshaft. Without this opposing mass from the counterweights the crankshaft will actually try and jump out of the main caps. This unbalance will KILL bearings, your block might crack, exploded crankshaft anyone. Another point to be made is that this could actually hurt power. Why? Because an unbalanced rotating assembly does not want to rotate! it wants to reciprocate!

I don't know that it'll be that extreme, but it will increase bearing loads.

They don't put on counterweights just so your butt dyno doesn't feel it, the proof is that they are producing V-6 and I-4 engines.

Wot?

Lets see some engineers, machinists, and wisemen in here!

Well, we try.

 

[91talon27]

I would run this in a street car but only if I balanced the pistons and rods which I always do anyway when I build a engine.The counterweight is there for just that purpose to counteract and cut down on engine vibrations while the rod and piston are moving, as are the balance shafts.There will be a slight increase in bearing wear as well as a slight increase in engine vibrations.It wont be enough of an increase in vibration that would be noticeable.For the record I am a Machinist for Honda of North America.

 

[spoonman]

Defiant is correct, as usual.

But here is my Rebuttal


Maybe I did not go enough in depth the first time. Not trying to be an A$$ but I believe this a horrible idea!

Torsional Vibration is the primary vibration created when the torque from the combustion stroke flexes the crankshaft, when the majority of this torque dissipates into kinetic energy the crankshaft unflexes, creating the Torsional Vibration.

The harmonic balancer is designed to absorb and then dissipate this harmful vibration which will damage your bearings as well as the crankshaft and block. Torsional Vibration needs to be removed form the engine because the crankshaft has a Natural Torsional Vibration frequency (like a guitar string) If these two frequencies coincides the vibration is amplified by a occurrence called resonance.

Torsional Vibrations are not transmitted out of the engine because the crankshaft rotates in the bearings and does not move against the crankcase.

The counterweights or pendulum absorbers, are in place to help hinder the torsional vibrations. It is the acceleration of the counterweight's mass that counteracts the twisting motion of the crankshaft. For and engine to be balanced, the vector sum of the inertia forces must be equal at zero. The mass of the counterweights oppose the force of the reciprocating assembly. This means that the counterweights are there to give the crankshaft Dynamic Balance: (balance due to the action of inertia forces, modifies the distribution of mass so that the center of mass is about the principal axis of rotation.) The mass of the counterweights absorb kinetic energy which causes the crankshaft to see less Torsional Vibration, the mass of the counterweights is a positive thing because the kinetic energy is actually stored in the mass of the counterweights and released when the crankshaft rotates.


Morgan Marr
Replacement Racing

 

[spoonman]

That's the flywheel's job.

I was being ironic, maybe you are too.

That's the harmonic balancer's job.

True but it can't absorb and dissipate it all.

Ask a shop to let you watch how they straighten cranks. You'll be amazed at how little it takes.

I have straightened crankshafts, I am not as ignorant/stupid as I sound.
spacebarspacebarspacebarspacebarspacebarspaceba^
spacebarspacebarspacebarspI always forget which one means 'Lacking Knowledge'

I don't know that it'll be that extreme

This is a little extreme but I trying to scar these kids straight.

Wot?

I actually donut understand what this means.

 

[flinguist]

Well, their first statement is about completely incorrect:
"A crank with no weights will vibrate like crazy. FALSE! Anyone that says this has no clue how an inline 4 cylinder works. An inline or opposed 4 cylinder engine is a naturally balanced engine. This means that you have two pistons going up and two going down. The weights on 4 cylinder cranks are there for low end torque, not balance. On an engine with a V configuration this would be true as the weights in V style engines are there for balance and are counter weights. Since our engines are not a V style (like a V8) you don’t need them."

An inline 4 is not naturally balanced. You don't get that until you either run a flat-4 with interleaving connecting rods, or a straight six. Inline fours are subject to secondary imbalance, which is what the Mitsubishi-patented, Porsche-licensed Silent Shafts are to combat, and why inline fours don't make it to 3-liters.

I'll be curious to hear how these pan out.

Actually, the Porsche 968 has a 3 liter in-line 4 cylinder. The Porsche 968