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Hopperdhh(at)aol.com
Guest

Posted: Sat Mar 18, 2006 3:18 am Post subject: Connecting rod/bolt balancing questions

I am in the middle of overhauling a Lycoming IO-360-A1A for my  RV-7A.  It 

has come to my attention that there are 2 different rod bolts  that will work in 

the LW10646 connecting rods.  One has a small head and a  later bolt has a 

larger head.

 

First question -- Is there anything wrong with using the small headed bolt  

(these are the ones I bought from Aircraft Specialties about a year ago)  

PN75060?

 

Second question -- What is the weight difference between the two  bolts?

 

I have weighed the rods (big ends and small ends), and could possibly use  

the heavier bolts to get a better matching set to improve the engine  balance.

 

Speaking of engine balance, what is considered good enough?  Is 6  grams at 

the big end of the rods really bad, or good, or what?  It  looks like I have 

about 3 grams worst case on the recip end.  The crank is  good (under 1 gram), 

and the piston/pins are only a couple of tenths  apart.

 

Thanks,

 

Dan Hopper

Walton, IN

RV-7A N766DH Flying 144 hours.

archie97(at)earthlink.net
Guest

Posted: Sat Mar 18, 2006 4:27 am Post subject: Connecting rod/bolt balancing questions

Balance criteria on any component is dependent on application parameters.

I personally maintain 1/5 of a gram on statics, and .01 in/oz on dynamics

(or better), for aircraft.  Racing engines better than that.

Why not? If you are there working anyway, why not do the best, or close to 

it?

(a dollar bill weighs one gram)

Archie

--

Hopperdhh(at)aol.com
Guest

Posted: Sat Mar 18, 2006 6:39 am Post subject: Connecting rod/bolt balancing questions

Archie,

 

I took the rods to a shop to be weighed.  I didn't want them to remove  any 

metal until I had a chance to analyze the weights.  Actually, I didn't  want to 

risk the damage they could do!  I don't have the equipment or  facilities to 

do the job myself, or I would do as you say.  Since they  were much, much 

worse than the values you gave, I wonder if there is really  anything to be gained 

by getting so "perfect."  I overhauled a  Continental O-200 a few years ago 

and got a very smooth running engine  by putting the heavier parts opposite 

each other, and matching heavy  rods with lighter pistons, etc.  The final 

assembly was not near as close  as you would have done.  The Continental Overhaul 

Manual states that  pistons opposite each other should be within 1/2 ounce -- 

that's about 14  grams.

 

I know that you will say to send the rods out to be balanced, but I  still 

want an answer to my original question from those who know from  experience.  I 

once read that "good enough is perfect."  Being a  perfectionist myself, I 

often have to use that philosophy to move projects  along.

 

Thanks,

Dan

 

 

 

In a message dated 3/18/2006 7:28:24 A.M. Eastern Standard Time,  arc

hie97(at)earthlink.net writes:






Balance criteria on any component is  dependent on application parameters.

I personally maintain 1/5 of a gram on  statics, and .01 in/oz on dynamics

(or better), for aircraft.  Racing  engines better than that.

Why not? If you are there working anyway, why not  do the best, or close to 

it?

(a dollar bill weighs one  gram)

Archie

archie97(at)earthlink.net
Guest

Posted: Sat Mar 18, 2006 7:25 pm Post subject: Connecting rod/bolt balancing questions

As you indicate, it is better to spend a little time and money now,

than to wish you had.

There is no substitute for perfection........... None!



The factory recommends 1/2 ounce?

Well, keep in mind these are the same people that give us oil burners,

AD's on an engine that has not changed for over 60 years, 1/2 hp per cu. in.

And they still do not have it right.

They essentially have a captive following that buys this.

If they did not have that, they would have folded long ago.



How would you like to be buying a new car and the salesperson told you

you must run plug gaps of .016 because magnetos will not support more,

It will burn oil, Is subject to AD's which you will forever pay for,

Has poor fuel economy, Blow-by, and 1/2 hp per cu in?

Would you find these attractive? Would you buy this car?



If a small hole in the wall shop like mine can correct most of these,

why can't they? Why do they have engineering if the most basic of problems

have not been corrected? Bean counters tend to run these companies, and

quality, plus R&D have fallen dormant.

I have somewhat evaded a succinct reply to your last post, but am thoroughly

miffed with the beaurocratic ineptitude, greed, and propagandists that seem

to be the root culprit hampering any progress.

Sorry about the long wind, but I have only started, and will quit now

to cool off.



==================================================

 	  Quote: 	
		   I took the rods to a shop to be weighed.  I didn't want them to remove 

 any

 metal until I had a chance to analyze the weights.  Actually, I didn't 

 want to

 risk the damage they could do!  I don't have the equipment or  facilities 

 to

 do the job myself, or I would do as you say.  Since they  were much, much

 worse than the values you gave, I wonder if there is really  anything to 

 be gained

 by getting so "perfect."  I overhauled a  Continental O-200 a few years 

 ago

 and got a very smooth running engine  by putting the heavier parts 

 opposite

 each other, and matching heavy  rods with lighter pistons, etc.  The final

 assembly was not near as close  as you would have done.  The Continental 

 Overhaul

 Manual states that  pistons opposite each other should be within 1/2 

 ounce -- 

 that's about 14  grams.



 I know that you will say to send the rods out to be balanced, but I  still

 want an answer to my original question from those who know from 

 experience.  I

 once read that "good enough is perfect."  Being a  perfectionist myself, I

 often have to use that philosophy to move projects  along.



 Thanks,

 Dan



 In a message dated 3/18/2006 7:28:24 A.M. Eastern Standard Time,  arc

 hie97(at)earthlink.net writes:



 



 Balance criteria on any component is  dependent on application parameters.

 I personally maintain 1/5 of a gram on  statics, and .01 in/oz on dynamics

 (or better), for aircraft.  Racing  engines better than that.

 Why not? If you are there working anyway, why not  do the best, or close 

 to

 it?

 (a dollar bill weighs one  gram)

 Archie

glcasey(at)adelphia.net
Guest

Posted: Sun Mar 19, 2006 5:20 am Post subject: Connecting rod/bolt balancing questions

I'll cautiously take what is probably the unpopular side of the  

discussion..

I don't understand the emphasis that gets placed on engine  

balancing.  These engines run relatively slowly and the perceived  

vibration in airframe is usually dominated by the propeller.  The  

propeller imparts vibration from a number of sources - one is its  

balance - the blades are at such a large radius that the slightest  

variation will result in more vibration than can be expected by the  

rotating parts of the engine.  Second is the pitch variation from  

blade to blade.  Again, the slightest pitch error operating at such a  

long lever arm will have a big effect on airframe vibration.   

finally, the airflow into the prop is not uniform around the  

circumference since it is affected by the airframe behind it as well  

as the mounting angle of the engine.



The balance of either the reciprocating or rotating parts will have  

essentially no effect on the durability or output of the engine -  

combustion loads overwhelm any possible mismatch in weights.  A  

couple of anecdotes that add evidence, but of course don't prove the  

point - a friend used to win drag races by building "dual  

displacement" engines - the inspectors would always check the  

displacement of the #1 cylinder so he would make the first crank  

throw a shorter stroke than the other three - engines ran great.  I  

while back I helped one of my teenagers rebuild his turbo Chrysler 4- 

banger.  He didn't have any money so we scrounged the parts and  

picked the best of the bunch to build the engine.  Some cylinders had  

different connecting rods than others (a LOT different), others had  

different compression ratios.  Ran smooth with good power for a long  

time after that.  Another anecdote (urban legend?) - when Continental  

was trying to beef up their engines they introduced pistons with iron  

top ring glands, certainly heavier than the all-aluminum pistons they  

replaced.  They approved  servicing a single cylinder with the new  

pistons even though it would upset the balance - at least they didn't  

think the balance issue was a big one.  Using what Continental does  

as the guideline is, of course, a risky thing.



Certainly no one can argue that poor balance is a good thing, but I  

just don't think the emphasis that seems to be put on balancing is  

justified.  What would I do?  Certainly pick the rod bolts that are  

supposed to be the most reliable (whichever one that is) regardless  

of weight.  I would match up the other parts the best I could with  

the tools I had and then I would bolt it together and go fly.



Just another irreverent comment - a "good" aircraft engine will put  

out about 200 hp from 360 cu. in. displacement, or 1.08 ft-lb per cu.  

in. torque, and they are rated at the minimum power, not the average  

of the population.  That is very good and very close to what a good  

automotive engine will produce.  It is compromised because of the  

compromises necessary to meet all the other requirements:  The idea  

is to build an engine that weighs the least, burns the least fuel, is  

the most reliable and lasts the longest while being built for the  

least cost.  If I were starting from scratch there would be some  

things I would change, but it wouldn't deviate a lot from the  norm.



Gary Casey

 	  Quote: 	
		  

 I am in the middle of overhauling a Lycoming IO-360-A1A for my   

 RV-7A.  It

 has come to my attention that there are 2 different rod bolts  that  

 will work in

 ....

 Speaking of engine balance, what is considered good enough?  Is 6   

 grams at

 the big end of the rods really bad, or good, or what?  It  looks  

 like I have

 about 3 grams worst case on the recip end.  The crank is  good  

 (under 1 gram),



 and the piston/pins are only a couple of tenths  apart.



 Thanks,



 Dan Hopper

 Walton, IN

 RV-7A N766DH Flying 144 hours.

gary.stiffler(at)kroger.c
Guest

Posted: Sun Mar 19, 2006 8:51 am Post subject: Connecting rod/bolt balancing questions

 	  Quote: 	
		  The factory recommends 1/2 ounce?


	


 	  Quote: 	
		  Well, keep in mind these are the same people that give us oil burners,


	


 	  Quote: 	
		  AD's on an engine that has not changed for over 60 years, 1/2 hp per cu.

in.
	




 	  Quote: 	
		  And they still do not have it right.


	


 	  Quote: 	
		  They essentially have a captive following that buys this.


	


 	  Quote: 	
		  If they did not have that, they would have folded long ago.


	


 



They have the same design and a captive following because the FAA along

with our legal system makes competition unprofitable. 



 



Gary AA1B 160



Cincinnati OH

Hopperdhh(at)aol.com
Guest

Posted: Sun Mar 19, 2006 10:18 am Post subject: Connecting rod/bolt balancing questions

Good points Gary,

 

You got me to thinking!  I'm an engineer, I ought to be able to figure  this 

out!  (Never mind that I'm an electrical engineer!)

 

I calculated the imbalance force due to 3 grams at 2.177 inches (1/2 the  

stroke of an IO-360) at 2700 RPM to be 2.98 pounds.  This is the  centrifugal 

force which would cause the engine to vibrate.  This comes from  P=mv

2/r (from 

my college physics book) after making all the conversions to  metric and back.

 

Now, if I'm cruising at 2300 rpm at 60 percent of 200 HP, the average force  

which must be exerted on the crank throw at 2.177 inches is 1510 pounds.   (In 

a 4 cylinder there is  a power stroke every 180 degrees.)   Actually the 

pulses probably go to 2 or 3 times this number.  This pulsing  is what makes the 

engine vibrate, or shake.

 

Your point is well taken.

 

Dan Hopper

RV-7A

 

 

In a message dated 3/19/2006 8:21:19 A.M. Eastern Standard Time,  

glcasey(at)adelphia.net writes:






I'll cautiously take what is probably the  unpopular side of the  

discussion..

I don't understand the  emphasis that gets placed on engine  

balancing.  These engines  run relatively slowly and the perceived  

vibration in airframe is  usually dominated by the propeller.  The  

propeller imparts  vibration from a number of sources - one is its  

balance - the blades  are at such a large radius that the slightest  

variation will result  in more vibration than can be expected by the  

rotating parts of the  engine.  Second is the pitch variation from  

blade to  blade.  Again, the slightest pitch error operating at such a   

long lever arm will have a big effect on airframe vibration.    

finally, the airflow into the prop is not uniform around the   

circumference since it is affected by the airframe behind it as well   

as the mounting angle of the engine.



The balance of either the  reciprocating or rotating parts will have  

essentially no effect on  the durability or output of the engine -  

combustion loads overwhelm  any possible mismatch in weights.  A  

couple of anecdotes that  add evidence, but of course don't prove the  

point - a friend used to  win drag races by building "dual  

displacement" engines - the  inspectors would always check the  

displacement of the #1 cylinder so  he would make the first crank  

throw a shorter stroke than the other  three - engines ran great.  I  

while back I helped one of my  teenagers rebuild his turbo Chrysler 4- 

banger.  He didn't have any  money so we scrounged the parts and  

picked the best of the bunch to  build the engine.  Some cylinders had  

different connecting rods  than others (a LOT different), others had  

different compression  ratios.  Ran smooth with good power for a long  

time after  that.  Another anecdote (urban legend?) - when Continental  

was  trying to beef up their engines they introduced pistons with iron   

top ring glands, certainly heavier than the all-aluminum pistons  they  

replaced.  They approved  servicing a single cylinder  with the new  

pistons even though it would upset the balance - at  least they didn't  

think the balance issue was a big one.  Using  what Continental does  

as the guideline is, of course, a risky  thing.



Certainly no one can argue that poor balance is a good thing,  but I  

just don't think the emphasis that seems to be put on  balancing is  

justified.  What would I do?  Certainly pick  the rod bolts that are  

supposed to be the most reliable (whichever  one that is) regardless  

of weight.  I would match up the other  parts the best I could with  

the tools I had and then I would bolt it  together and go fly.



Just another irreverent comment - a "good"  aircraft engine will put  

out about 200 hp from 360 cu. in.  displacement, or 1.08 ft-lb per cu.  

in. torque, and they are rated  at the minimum power, not the average  

of the population.  That  is very good and very close to what a good  

automotive engine will  produce.  It is compromised because of the  

compromises  necessary to meet all the other requirements:  The idea  

is to  build an engine that weighs the least, burns the least fuel, is  

the  most reliable and lasts the longest while being built for the  

least  cost.  If I were starting from scratch there would be some   

things I would change, but it wouldn't deviate a lot from the   norm.



Gary Casey

 	  Quote: 	
		  

 I am in the middle of  overhauling a Lycoming IO-360-A1A for my   

 RV-7A.   It

 has come to my attention that there are 2 different rod bolts   that  

 will work in

 ....

 Speaking of engine  balance, what is considered good enough?  Is 6   

 grams  at

 the big end of the rods really bad, or good, or what?   It  looks  

 like I have

 about 3 grams worst case on  the recip end.  The crank is  good  

 (under 1  gram),



 and the piston/pins are only a couple of tenths   apart.



 Thanks,



 Dan Hopper

 Walton,  IN

 RV-7A N766DH Flying 144 hours.

Hopperdhh(at)aol.com
Guest

Posted: Sun Mar 19, 2006 11:45 am Post subject: Connecting rod/bolt balancing questions

When I read my listing as it came over the internet, I see that the carat  

symbol was deleted making it seem that I got the formula for centrifugal force  

wrong.

 

I'll spell it out:  centrifugal force equals mass times velocity  squared 

divided by radius.

 

Dan

 

 

In a message dated 3/19/2006 1:19:22 P.M. Eastern Standard Time,  

Hopperdhh(at)aol.com writes:




Good points  Gary,



You got me to thinking!  I'm an engineer, I ought to be able  to figure  this 

out!  (Never mind that I'm an electrical  engineer!)



I calculated the imbalance force due to 3 grams at 2.177  inches (1/2 the  

stroke of an IO-360) at 2700 RPM to be 2.98  pounds.  This is the  

centrifugal 

force which would cause the  engine to vibrate.  This comes from  P=mv

2/r (from 

my  college physics book) after making all the conversions to  metric and  

back.



Now, if I'm cruising at 2300 rpm at 60 percent of 200 HP, the  average force  

which must be exerted on the crank throw at 2.177  inches is 1510 pounds.   

(In 

a 4 cylinder there is  a power  stroke every 180 degrees.)   Actually the 

pulses probably go to  2 or 3 times this number.  This pulsing  is what makes 

the  

engine vibrate, or shake.



Your point is well taken.



Dan  Hopper

RV-7A

In a message dated 3/19/2006 8:21:19 A.M. Eastern  Standard Time,  

glcasey(at)adelphia.net writes:






I'll cautiously take what is probably  the  unpopular side of the  

discussion..

I don't understand  the  emphasis that gets placed on engine  

balancing.  These  engines  run relatively slowly and the perceived  

vibration in  airframe is  usually dominated by the propeller.  The   

propeller imparts  vibration from a number of sources - one is  its  

balance - the blades  are at such a large radius that the  slightest  

variation will result  in more vibration than can be  expected by the  

rotating parts of the  engine.  Second is  the pitch variation from  

blade to  blade.  Again, the  slightest pitch error operating at such a   

long lever arm will  have a big effect on airframe vibration.    

finally, the airflow  into the prop is not uniform around the   

circumference since it  is affected by the airframe behind it as well   

as the mounting  angle of the engine.



The balance of either the  reciprocating or  rotating parts will have  

essentially no effect on  the  durability or output of the engine -  

combustion loads  overwhelm  any possible mismatch in weights.  A  

couple of  anecdotes that  add evidence, but of course don't prove the   

point - a friend used to  win drag races by building "dual   

displacement" engines - the  inspectors would always check the   

displacement of the #1 cylinder so  he would make the first  crank  

throw a shorter stroke than the other  three - engines  ran great.  I  

while back I helped one of my  teenagers  rebuild his turbo Chrysler 4- 

banger.  He didn't have any  money  so we scrounged the parts and  

picked the best of the bunch to   build the engine.  Some cylinders had  

different connecting  rods  than others (a LOT different), others had  

different  compression  ratios.  Ran smooth with good power for a long   

time after  that.  Another anecdote (urban legend?) - when  Continental  

was  trying to beef up their engines they  introduced pistons with iron   

top ring glands, certainly  heavier than the all-aluminum pistons  they  

replaced.   They approved  servicing a single cylinder  with the new   

pistons even though it would upset the balance - at  least they  didn't  

think the balance issue was a big one.  Using  what  Continental does  

as the guideline is, of course, a risky   thing.



Certainly no one can argue that poor balance is a good  thing,  but I  

just don't think the emphasis that seems to be  put on  balancing is  

justified.  What would I do?   Certainly pick  the rod bolts that are  

supposed to be the most  reliable (whichever  one that is) regardless  

of weight.  I  would match up the other  parts the best I could with  

the tools  I had and then I would bolt it  together and go fly.



Just another  irreverent comment - a "good"  aircraft engine will put  

out  about 200 hp from 360 cu. in.  displacement, or 1.08 ft-lb per cu.   

in. torque, and they are rated  at the minimum power, not the  average  

of the population.  That  is very good and very  close to what a good  

automotive engine will  produce.  It  is compromised because of the  

compromises  necessary to meet  all the other requirements:  The idea  

is to  build an  engine that weighs the least, burns the least fuel, is  

the   most reliable and lasts the longest while being built for the   

least  cost.  If I were starting from scratch there would be  some   

things I would change, but it wouldn't deviate a lot from  the   norm.



Gary Casey

 	  Quote: 	
		  

 I am in the  middle of  overhauling a Lycoming IO-360-A1A for my   

  RV-7A.   It

 has come to my attention that there are 2  different rod bolts   that  

 will work in

  ....

 Speaking of engine  balance, what is considered good  enough?  Is 6   

 grams  at

 the big end of  the rods really bad, or good, or what?   It  looks   

 like I have

 about 3 grams worst case on  the recip  end.  The crank is  good  

 (under 1   gram),



 and the piston/pins are only a couple of  tenths   apart.



 Thanks,



 Dan  Hopper

 Walton,  IN

 RV-7A N766DH Flying 144  hours.

archie97(at)earthlink.net
Guest

Posted: Sun Mar 19, 2006 12:06 pm Post subject: Connecting rod/bolt balancing questions

Gentlemen;

This topic is far more complex than you believe.

I will not go into the finer details, but you are superficially bouncing 

numbers

and quotes but not doing any correcting.

"good enough" is not good enough, "perfect" is.

Although not analogous, would you want a heart surgeon telling you:

"while I am in there, will do the least required"



When teaching machinery dynamics as part of my physics course, the text

was Machinery Dynamics by Holowenko.Check it out, and be surprised.

As far as durability is concerned, how long do you think an electric motor's

bearings will last if it was not in balance, or your aircraft gyro.

Forget RPM, it is either right or wrong, although geometrically progressive.



Vibration was mentioned. That is only a resultant indicator.

A number of factors can cause vibration, such as compression imbalance.

(just pull a spark plug lead while an engine is running)

Many other causes are culprits also, but too involved to discuss here.

If you are not going to do a perfect dynamic and kinematic balance to your

engine, why seek a way to avoid it?

No more from here.......

Archie

Hopperdhh(at)aol.com
Guest

Posted: Sun Mar 19, 2006 12:29 pm Post subject: Connecting rod/bolt balancing questions

Archie,

 

Is this subject so complex that only you can understand it?  You asked  

several questions in your post, but you are not interested in the answers.

 

First of all, what is your definition of perfect?  It must be the  accuracy 

or resolution of your equipment.  Apparently your scales only  weigh to .01 

grams.  What if I needed my rods balanced to .001 grams,  isn't that closer to 

perfect than what you could handle?

 

Good enough is not perfect and neither is your work.  You are very  naive if 

you think anything in this world is perfect.  There is a very good  reason why 

Lycoming has built thousands of engines which were terribly out of  balance 

yet give perfectly (ha) satisfactory service in the field.  That  reason is 

that they don't need to be perfect, only good enough.

 

Dan

 

 

 

In a message dated 3/19/2006 3:06:47 P.M. Eastern Standard Time,  

archie97(at)earthlink.net writes:






Gentlemen;

This topic is far more  complex than you believe.

I will not go into the finer details, but you are  superficially bouncing 

numbers

and quotes but not doing any  correcting.

"good enough" is not good enough, "perfect" is.

Although not  analogous, would you want a heart surgeon telling you:

"while I am in  there, will do the least required"



When teaching machinery dynamics as  part of my physics course, the text

was Machinery Dynamics by  Holowenko.Check it out, and be surprised.

As far as durability is  concerned, how long do you think an electric motor's

bearings will last if  it was not in balance, or your aircraft gyro.

Forget RPM, it is either  right or wrong, although geometrically progressive.



Vibration was  mentioned. That is only a resultant indicator.

A number of factors can  cause vibration, such as compression imbalance.

(just pull a spark plug  lead while an engine is running)

Many other causes are culprits also, but  too involved to discuss here.

If you are not going to do a perfect dynamic  and kinematic balance to your

engine, why seek a way to avoid it?

No  more from here.......

Archie

edchmiel(at)mindspring.co
Guest

Posted: Sun Mar 19, 2006 4:31 pm Post subject: Connecting rod/bolt balancing questions

Hmm, this should be good .  Think I'll grab a beer and watch...



Ed in JXN





---

glcasey(at)adelphia.net
Guest

Posted: Mon Mar 20, 2006 5:44 am Post subject: Connecting rod/bolt balancing questions

Okay, just for the fun of it let's keep this thread going.  I think  

there is no substantial argument that can prove that improved balance  

can help durability.  The combustion pressure pushing on a 5.25 dia.  

piston results in a force of about 17,000 pounds, certainly orders of  

magnitude more than any likely unbalance.  However, the engine  

balance can have an affect on accessories - notably alternator  

mounting brackets.



How good does the balance have to be?  Is perfection the only logical  

goal?  I don't think so - it should be good enough so that engine  

imbalance doesn't add noticeable vibration to the airframe.  Even if  

it were perfect to imply that rotating imbalance will go to zero is  

incorrect.  A 4-cylinder opposed engine has a quite high secondary  

yaw couple that can't be balanced.  Even the 6-cylinder engines are  

only balanced in first and second order modes - higher orders may not  

be balanced (I don't know as most people stop analyzing after the 2nd  

order).  It's all a matter of priorities and I would put my efforts  

somewhere else.  Getting a dynamic prop balance after the engine is  

running always seems like a good idea, although my last Cessna was  

very smooth without it, so I never bothered.  On the Cessna before  

that I had dynamic balancing done whenever we had anything done that  

could affect balance and even then it was never very smooth.



Gary Casey

Wes Bunker

Joined: 10 Jan 2006
Posts: 5
Location: Lincoln, CA

Posted: Mon Mar 20, 2006 8:33 am Post subject: Connecting rod/bolt balancing questions

Archie, I have to point out that pulling a plug wire will not change

compression of that cylinder. It will certainly change the combustion

pressure, which does increase the amount of vibration. A few months back my

O-320 swallowed the #4 exhaust valve head. Whole lotta shakin' goin' on, I

can tell you! Careful balancing of reciprocating parts in any piece of

machinery contributes to longevity of the bearings as well as any

fatigue-sensitive parts. Engineers may be able to tell us the specific

numbers related to this, but any old backyard shade-tree race car bulder can

tell you the facts of reality.

 

Wes

_________________
Wes
N7337G
C172K

gary.stiffler(at)kroger.c
Guest

Posted: Mon Mar 20, 2006 9:35 am Post subject: Connecting rod/bolt balancing questions

 	  Quote: 	
		  Hmm, this should be good .  Think I'll grab a beer and watch...


	


 



 	  Quote: 	
		  Ed in JXN


	


 



Wow! I agree, this is interesting.



 



 	  Quote: 	
		  First of all, what is your definition of perfect?  It must be the

accuracy or resolution of >your equipment.  Apparently your scales only
	


weigh to .01 grams.  What if I needed my rods >balanced to .001 grams,

isn't that closer to



 



 	  Quote: 	
		  perfect than what you could handle?


	


 



I have a few questions and I mean no disrespect I am just curious. If what

was necessary was .001 and you only had equipment that measured .01,

wouldn't you get different equipment? 



I think in one of the original posts the balance question was brought up

because the shop that was doing the work was not trusted to remove metal

from the parts. I have not seen that in today's comments so my next

question assumes that it is not an issue. If you were balancing anything

on something that rotates what would be the reason to not balance it as

well as your equipment will allow? The result may not be perceived by your

senses but it could not have a negative effect on wear. You may not

achieve "perfection" but why set out to half-ass it? 



 



 



 



 Gary AA1B 160 N952GS

Hopperdhh(at)aol.com
Guest

Posted: Mon Mar 20, 2006 11:08 am Post subject: Connecting rod/bolt balancing questions

Gary,

 

I have done business with this shop before!  I only wanted the weights  of 

the rods -- big end and small end, I didn't want to risk having them grind  

strength away in the wrong place or otherwise ruin the rods.  Search some  on the 

web and you'll see that several sites advise against removing weight from  

Lycoming rods.  My thinking was that I could match up the rods opposite  each 

other in the best pairs and not have to risk ruining them.

 

In my first post, I wanted to know what is considered good enough.

 

clip ---

Speaking of engine balance, what is considered good enough?  Is 6  grams at 

the big end of the rods really bad, or good, or what?  It  looks like I have 

about 3 grams worst case on the recip end.  The crank is  good (under 1 gram), 

and the piston/pins are only a couple of tenths  apart.

---

 

Archie says that nothing less than perfect is acceptable.  I know that  

perfect is impossible to achieve, so I still want to know what is considered  "good 

enough."

 

Dan Hopper

RV-7A Flying (working on 2nd engine)

 

 

In a message dated 3/20/2006 12:36:42 P.M. Eastern Standard Time,  

gary.stiffler(at)kroger.com writes:

I  think in one of the original posts the balance question was brought  up

because the shop that was doing the work was not trusted to remove  metal

from the parts. I have not seen that in today's comments so my  next

question assumes that it is not an issue. If you were balancing  anything

on something that rotates what would be the reason to not balance  it as

well as your equipment will allow? The result may not be perceived by  your

senses but it could not have a negative effect on wear. You may  not

achieve "perfection" but why set out to half-ass it?  



Gary AA1B 160 N952GS

archie97(at)earthlink.net
Guest

Posted: Mon Mar 20, 2006 2:40 pm Post subject: Connecting rod/bolt balancing questions

Am still reading the thread, but will not comment any further regarding 

this.

I will say that I own three balancing machines capable of weights of 1500lbs

to several ounces. I also have two analytical systems for checking and 

locating

imbalance of rotating parts.

You are correct in bracket cracking, (also exhaust cracking), where proper

balancing of all rotating parts, (including alternator) contributes to 

reduction

of such. Also, the propeller, correctly indicated earlier, is a major 

culprit.

An interesting fact many may not be aware of, is that once everything is 

perfect,

a simple removal and replacement of the prop will show a slight imbalance,

which would not be noticeable, but the instruments have picked it up.

BTW, I do not believe I mentioned that pulling a wire changes static 

compression.

Obviously that is fixed. It will change resultant pressure due to lack of 

combustion.

I cover all these aspects in my presentations to race shops, and EAA 

chapters.

BTW, I am also a retired industrial engineer, college professor, currently

building racing engines.(with three world records), and have raced for over 

thirty years.

Nuff said, no need to turn this into a novella.

Happy flying...

Archie

---

archie97(at)earthlink.net
Guest

Posted: Mon Mar 20, 2006 2:57 pm Post subject: Connecting rod/bolt balancing questions

One last one:

Yes, one of my static scales has the ability to read .001



On a V-type engine the weight of oil in the crank throw

passages is incorporated in the bob weight formula.

Then there are certain instances when an engine will be overbalanced,

but that is another application...................

End of semantics...........

s_korney(at)hotmail.com
Guest

Posted: Mon Mar 20, 2006 3:06 pm Post subject: Connecting rod/bolt balancing questions

Snip



" BTW, I am also a retired industrial engineer, college professor, currently

building racing engines.(with three world records), and have raced for over

thirty years."---------------------------------------

Just out of curiosity Archie.... What World Records do you personally 

own...?



Best... Steve



----Original Message Follows----

From: "Archie" <archie97(at)earthlink.net>

Reply-To: engines-list(at)matronics.com

To: <engines-list(at)matronics.com>

Subject: Re: Re: Connecting rod/bolt balancing questions

Date: Mon, 20 Mar 2006 17:37:19 -0500






Am still reading the thread, but will not comment any further regarding

this.

I will say that I own three balancing machines capable of weights of 1500lbs

to several ounces. I also have two analytical systems for checking and

locating

imbalance of rotating parts.

You are correct in bracket cracking, (also exhaust cracking), where proper

balancing of all rotating parts, (including alternator) contributes to

reduction

of such. Also, the propeller, correctly indicated earlier, is a major

culprit.

An interesting fact many may not be aware of, is that once everything is

perfect,

a simple removal and replacement of the prop will show a slight imbalance,

which would not be noticeable, but the instruments have picked it up.

BTW, I do not believe I mentioned that pulling a wire changes static

compression.

Obviously that is fixed. It will change resultant pressure due to lack of

combustion.

I cover all these aspects in my presentations to race shops, and EAA

chapters.

BTW, I am also a retired industrial engineer, college professor, currently

building racing engines.(with three world records), and have raced for over

thirty years.

Nuff said, no need to turn this into a novella.

Happy flying...

Archie

---

glcasey(at)adelphia.net
Guest

Posted: Tue Mar 21, 2006 5:39 am Post subject: Connecting rod/bolt balancing questions

Dan,

In all the fun we all ignored your original question - "how good is  

good enough?" - for which there is probably no answer.  At one  

extreme you could just bolt the parts together and get what you get.   

At the other extreme is perfection, which you won't get.  I'm  

certainly not an expert as to where you can remove material from  

connecting rods, but I would suggest not removing material unless you  

are sure there is no stress at that location.  Regardless of what you  

do, I propose that the difference between putting the engine together  

with existing parts just matched as best you can (two heaviest rods  

opposite each other, etc) and going for perfection will be  

imperceptible.  And it will have no effect whatsoever on power,  

reliability or durability.  Search for perfection someplace else.   

Just my opinion.

Gary



 	  Quote: 	
		  

 In my first post, I wanted to know what is considered good enough.



 clip ---

 Speaking of engine balance, what is considered good enough?  Is 6   

 grams at

 the big end of the rods really bad, or good, or what?  It  looks  

 like I have

 about 3 grams worst case on the recip end.  The crank is  good  

 (under 1 gram),



 and the piston/pins are only a couple of tenths  apart.

 ---



 Archie says that nothing less than perfect is acceptable.  I know that

 perfect is impossible to achieve, so I still want to know what is  

 considered  "good



 enough."



 Dan Hopper

 RV-7A Flying (working on 2nd engine)

jlbaker(at)telepath.com
Guest

Posted: Tue Mar 21, 2006 8:08 am Post subject: Connecting rod/bolt balancing questions

 	  Quote: 	
		   In all the fun we all ignored your original question - "how good is 

 good enough?" 


	




Not to be the puryevor of doom and gloom, how about...

    Crankcase cylinder deck height variations 

    between banks 

    Crankcase cylinder deck height variations 

    between cylinders 

    Crankshaft stroke variations between 

    journals 

    Connecting rod rotating weight  (already 

    discussed)

    Connecting rod reciprocating weight 

    Connecting rod length  (pin CL to CL)

    Piston weight 

    Piston dome volume 

    Piston wrist pin height 

    Wrist pin weight 

    Cylinder head volume 

    Cylinder intake and exhaust port airflow 

    Cylinder - installed height of intake and 

    exhaust valves



Courtesy of the Mattituck site (too lazy to type it myself). There's just a lot 

more than rod weights to consider. Of course, all this may be overkill. 

Shoot, give 'em a call at 800.624.6680 and see what tolerances they 

use. May be enlightening....or discouraging. Your pick.

Jim Baker

580.788.2779

'71 SV,  492TC

Elmore City, OK

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