Balanced Crank?

[Deleted member 12676]

 

[Street Ryderz]

Just as I thought.
That crank is mine and is balanced.
Now I will answer the question for you as to what to do using your model T Ford method.
115 grams is the reciprocating weight and so .6 (a typical balance factor) times that is 69 grams.
So with a bob weight of 69 grams hanging from the hanging con rod the 9mm hole would need to be bored out to 13.6mm to have a static balance.
That is basically 16.6 grams needlessly removed.
Both too little and too much causes vibration.
Using this stupid method designed for 90 degree V8's the engine would end up with needless vibration.

If any of you all want to rescue yourself from any of your idiot predecessors and become truly informed just go to my site and read up on this subject as well as many others. Beware all the con artists like Sleezy Rider (Street Riderz). They have a low IQ and have a dangerous amount of knowledge, not much but just enough to inflate their corrupt ego's. Just as I destroyed his crude beliefs about crank balancing I can do the same about porting, compression, squish bands, ignition timing, expansion chambers, carburetion, etc.
Here's why I infrequently visit this forum or any other: http://www.dragonfly75.com/motorbike/forums.html

Iwas busy you didn't wait long before jumping all over it though huh? I all ready told you the factor of the above diagram and good luck with that! I stated above that there's no perfect balence and that I find and alter the factor to balance the crank witch is exactly what it does! Did I say that it takes into acount for the cylinder pressures or anything else NO! It is what it is and doesn't take much more than commen sence to do and some tools.Your childish attacks and insulting my intelligence doesn't bother me a bit just help's show every one else the real you right?Btw I like how you describe me as a con artist that's pure jokes! how do I stand to gain from freely offering information LOL smh.

 

[Deleted member 12676]

You don't even realize how you start conflicts.
I'll start a post in a very neutral manner just offering information and you'll jump in beginning each response with LOL (lots of laughs) which is clearly derogatory and incendiary and then after you get me really pissed off I start blasting you then you call me out as having "childish attacks".
Yes they are childish but what a F'ing hypocrite you are by intentionally pissing people off and then calling them out for being pissed off.
Why don't you grow up and stop picking fights to begin with?
I can prove you wrong on almost any 2 stroke subject with or without fire bombs. Take your choice.
I'd rather silence you in a mature way. But I think you like pissing people off.
That's got to be against the forum rules. You should be thankful the moderators don't care to enforce the rules.

 

[Deleted member 12676]

These graphs illustrate what a crummy method using a balance factor is. CrankCalc is the spreadsheet used to calculate balance for the first graph.

(If it don't show then go to www.dragonfly75.com/motorbike/images/6balancefactor.gif )

 

[Street Ryderz]

In order achieve a good understanding of the principles involved in engine balance is first necessary to understand the concept of balance factor, as it applies to the primary forces of a single cylinder engine. Figure 6 LHS shows how the piston applies an upward force on the conrod, at top dead centre, and also how when close to mid-stroke (RHS sketch), the piston moving at maximum velocity produces no in-line primary force. As shown in the LHS the addition of a counterweight can be used to cancel the force from the piston. Unfortunately, this simple idea is not the answer, as we can see when the piston is at mid-stroke. The counterweight will still produce a centrifugal force, but which is no longer balanced by that from the piston. So all we have done is replaced an in-line reciprocating force with a lateral alternating force of the same peak magnitude. When the counterweight exactly balances the primary reciprocating forces at TDC or BDC like this, we say that we have 100% balance factor. If no attempt is made to balance the piston force, that is; the crankshaft is in static balance after allowing for the mass of the rotating part of the conrod. We say that we have a zero balance factor. Factors between zero and 100% give rise to a combination of rotating force and reciprocating force. Fig. 7. shows plots of the primary inertial forces throughout a complete crankshaft revolution, for balance factors of 0, 50 and 100%. Inline and lateral forces are shown, as well as the magnitude of the resultant of these two forces and the direction in which it acts at any particular crankshaft angle. The lower set of plots drawn on polar axes gives a different perspective of the resultant and its direction. The upper row shows the magnitude against the range of crank shaft positions, and the lower row shows the same magnitude plotted against the angular position relative to the orientation of the cylinder.Fig.6 The LHS and RHS sketches show how fully balancing the reciprocating mass at TDC only creates an equal primary alternating force acting at 90°. The central sketch shows the actual situation with a real conrod. With the crank at approximately 77° there is no piston force and the full counter weight force acts as shown. This force varies in magnitude and direction throughout a rotation. Fig. 7. The upper three sets of plots show the primary inertial forces throughout a complete crankshaft revolution, for balance factors of 0, 50 and 100%. The lower set shows the resultant magnitude re-plotted on polar coordinates giving a different perspective to the same data. Let us study these graphs in more detail because they illustrate some interesting aspects of engine balance. The zero balance factor case shows that we have a sinusoidal in-line force but zero transverse force through the range of rotation. In other words the unbalanced forces vary in magnitude but always act up or down in-line with the cylinder. The bottom right plot shows the force direction to be 0° (360°) or 180° from TDC. The lower polar plot also shows the inline nature of the forces whereas the upper one shows how the magnitude varies with crank angle. The 50% factor case is quite different. Firstly, notice that the peak value of the in-line force has reduced to half of the previous value due to the counter-weight force. Secondly, note that we have now introduced transverse forces, also of the same magnitude, but shifted in phase by 90° of crankshaft rotation. The resultant of these two forces always sums to a constant value pointing radially outward from the crank axis. The polar plots also show this nicely. This constant radial force actually rotates in the opposite direction to that of the crankshaft rotation, as shown in figure 8. This balance factor also gives the least magnitude of the resultant of all balance factors, being 0.5 times the unbalanced peak reciprocating force. Looking at the 100% balance factor curves, we see that the direction of the forces has simply switched from in-line to transverse with the same magnitude. At TDC and BDC the reciprocating forces are perfectly balanced by the counter-weight, which then leaves transverse forces only. The polar plots easily show that this case is just the same as the zero factor situation except that everything has shifted through 90°. Balance factors other than these three values will give rise to resultants of between 50% and 100% of the unbalanced reciprocating force, and with force directions being a combination of linear and rotational, depending on the actual BF. We now understand the effects of different balance factors.For the graphs they can be found at.
www.tonyfoale.com/Articles/EngineBalance/EngineBalance.pdf for free of course LOL.

 

[Stoneman]

from http://www.onallcylinders.com/2016/03/17/the-basics-of-crankshaft-balancing/

Machinists and engine builders have long been taught that, when balancing a crankshaft, its counterweights should equal the weight of the rotating mass, and equal half the weight of the reciprocating mass. Machinists have used this formula to calculate bobweight for decades.
While this technique works extremely well for most street and race 90-degree V8 engines, the truth is it’s nearly impossible to balance a crankshaft perfectly. That’s because the balancer cannot account for variables like cylinder pressure, ring drag, rod length, counterweight phasing, engine rpm, stroke length, bearing friction, secondary vibrations, rocking couples, and static mass.
All of those factors play a major role in engine balance, yet the traditional mathematical formula used for calculating bobweight completely ignores them. Instead, calculating bobweight is based strictly on measuring rotating weight and reciprocating weight, which is a gross oversimplification of the actual dynamic forces at play inside an engine that affect balancing.
In other words, the traditional method of balancing a crank is, at best, an imperfect science. In fact, it’s not based on any real science or mathematics at all. It’s simply a technique based on trial and error that happens to work well in most 90-degree, cross-plane V8s.

Not that I know but this makes complete sense to me.

 

[Street Ryderz]

You don't even realize how you start conflicts.
I'll start a post in a very neutral manner just offering information and you'll jump in beginning each response with LOL (lots of laughs) which is clearly derogatory and incendiary and then after you get me really pissed off I start blasting you then you call me out as having "childish attacks".
Yes they are childish but what a F'ing hypocrite you are by intentionally pissing people off and then calling them out for being pissed off.
Why don't you grow up and stop picking fights to begin with?
I can prove you wrong on almost any 2 stroke subject with or without fire bombs. Take your choice.
I'd rather silence you in a mature way. But I think you like pissing people off.
That's got to be against the forum rules. You should be thankful the moderators don't care to enforce the rules.

Dude you came on this thread and proceded to put down a method used by many to this day I dont care what you say!and you did so to plug your calculator so if I pissed you of in my responce so be it I'm intitled to my opinion and just because it differs from yours to bad!I analize many an opinion before fourming my own and I'm sure am not the only one like that LOL oh sorry I put LOL again didn't mean to upset you again!with such a derogatory term.

 

[Deleted member 12676]

Yes it is used by many to this day but this is 2018 and its time to leave off fred flintstone methods and enter the computer age.
Yes I plug my calculator but it is as much a mission of mercy than anything. There are only two that I know of and the other one is 20 times the cost of mine. At $15 it is practically a give-away.
Yes you are entitled to your opinion but you can disagree and share it without being insulting by laughing and telling others that their ideas are a joke.
Your insincerity at the end is very telling.
You are a crude insensitive modern caveman and you think you have a right to fart in anyones face, hell yeah thats practically an American right.

When I participate in forums based in Europe I never encounter crude assholes like you. NEVER!

 

[Street Ryderz]

 

[Deleted member 12676]