Terminology problem - meaning of neutrally balanced - Page 3 - PeachParts Mercedes-Benz Forum

panZZer · #31 01-24-2012, 05:25 PM

Quote:

Originally Posted by Army

I think panZZer means they didn't mark the crank and flywheel past about 1981 not that they weren't balanced. My 1981 OM617 doesn't have factory balance markings on it - I remember a few people on the forum saying that they hadn't ever seen these marks... so it does indeed seem as though they just disappeared.

i meant everything after 81 seems to be neutral balanced--They got their act together.

If someone can get R Leo's thread "automatic to manual conversion has begun" theres pics of some off balanced witness marks in crank and flywheel I seem to remember the search link wont bring it up--- hey ROY....

Stretch · #32 01-25-2012, 03:23 AM

Here's the thread that panZZer's talking about

Auto -> Manual Transmission Conversion Has Begun.

Thanks for bumping it up Roy.

The pictures are here:-

Stretch · #33 01-25-2012, 03:30 AM

Quote:

Originally Posted by vstech

OK, as a former race engine builder... there are three types of balancing being discussed.

Internal and external, with neutral being tossed in for added confusion.

internal balance refers to the engine crankshaft being balanced to the exact match in the books based on the exact weight of the rods and pistons with rings weight for a smooth reciprocating engine.
external balance means for whatever reason, the crank is balanced with either the harmonic balancer and or the flywheel with added/removed weight on them to get the piston packs to balance in the engine.

if the engine is internally balanced, a neutral balanced flywheel and or harmonic balancer is needed.

Thanks for the input John, but that's as clear as mud to me.

For the internal balance where you say "exact match in the books" - do you mean to the manufacturer's specifications? If so that could mean anything couldn't it? It might even mean don't bother balancing!

whunter · #34 01-25-2012, 05:54 AM

Quote:

Originally Posted by Army

Thanks for the input John, but that's as clear as mud to me.

For the internal balance where you say "exact match in the books" - do you mean to the manufacturer's specifications? If so that could mean anything couldn't it? It might even mean don't bother balancing!

Asking for the correct flywheel mounting position is a clear question.

Attempting to clarify terminology fifty two+ years after engineering is difficult, confusing, and often impossible to have an accurate answer.

The entire topic is confusing, most engineers have little or no understanding of the historic misuse/abuse of the term in automotive technical material.

The field of internal combustion engines has gone through many generations of change, growth, with incomplete, contradictory, confusing supposedly authoritative technical information.

Here are a few horribly abused automotive terms:
* Balance.
* Design, is NOT engineering!!!
* Engineering, is NOT design!!!
* Harmonic.
The understanding, definition, and application was almost useless before WW2, and remained sporadic to miserable until SAE standards became industry standards.

Read the full document for a few examples of generational changes.
Engine balance - Wikipedia, the free encyclopedia

My favorite example is an acquaintance who bought a 1920's Rolls Royce, rebuilt the totally original engine to modern main/rod bearing 0.003 tolerance with fresh babbitt bearing (no other alteration).
He has forced it to run half an hour before failure several times, and is currently rebuilding it for the seventh time in fifteen years.
Several dozen experts have tried to explain, he fails to understand.

.

t walgamuth · #35 01-25-2012, 06:16 AM

I continue to be fascinated by the action here surrounding exact terminology.

Since I am neither Engineer or Attorney exact wording often matters little to me as long as I understand what needs to be done and can communicate to someone who I am asking to do a job for me in language they embrace.

I only care about getting the job done correctly.

BTW, my witness marks on the 84 280e flywheel and crank were not like the ones shown in the picture. I don't have a picture though so this comment is worthless!

vstech · #36 01-25-2012, 09:21 AM

Quote:

Originally Posted by Army

Thanks for the input John, but that's as clear as mud to me.

For the internal balance where you say "exact match in the books" - do you mean to the manufacturer's specifications? If so that could mean anything couldn't it? It might even mean don't bother balancing!

yup. clear as mud.
sorry...

basically, it's an indicator of the design of the crankshaft.

exact match by the books, meaning the books the machinist uses to compute the crank balance in a specific motor. in other words, (in a race motor at least) the PRECISE weight of the combined weight of the rod/wristpin/piston/ring pack is input to a device for balancing the crank, then the crank is spun by the machine, and it tells where to add or remove mass on the crank to get it to spin without vibration at the RPM the motor is designed to spin.
on a race motor spinning 10K plus RPM, internal balance is a must, or the flex of the crank can be explosive.
for a street car, the RPM is usually under 4K, or only that high for a short burst, and external balance can be OK, but internal is still best.

IF the crank is internally balanced, the bolt on spinning mass on either end of the crank (harmonic balancer/Flywheel) need to be neutral balanced.
if the crank is NOT internally balanced, the bolt on mass needs to be MATCH balanced.

I'll go ahead and toss in an additional balance item in a motor...
that's FIRING order balance... it has little to do with the mass of each part or the crank/piston relationship, it's related to the power stroke/intake/exhaust stroke of each piston and the balance of the others on the crank... inline 6's are naturally FO balanced, 5 cyl's are close, v-8's and v 6's need balance shafts sometimes to throw weight in opposing directions to the FO shake to achieve a smooth chassis...

Stretch · #37 01-25-2012, 10:12 AM

Quote:

Originally Posted by whunter

Asking for the correct flywheel mounting position is a clear question.

Attempting to clarify terminology fifty two+ years after engineering is difficult, confusing, and often impossible to have an accurate answer.

The entire topic is confusing, most engineers have little or no understanding of the historic misuse/abuse of the term in automotive technical material.

The field of internal combustion engines has gone through many generations of change, growth, with incomplete, contradictory, confusing supposedly authoritative technical information.

Here are a few horribly abused automotive terms:
* Balance.
* Design, is NOT engineering!!!
* Engineering, is NOT design!!!
* Harmonic.
The understanding, definition, and application was almost useless before WW2, and remained sporadic to miserable until SAE standards became industry standards.

Read the full document for a few examples of generational changes.
Engine balance - Wikipedia, the free encyclopedia

My favorite example is an acquaintance who bought a 1920's Rolls Royce, rebuilt the totally original engine to modern main/rod bearing 0.003 tolerance with fresh babbitt bearing (no other alteration).
He has forced it to run half an hour before failure several times, and is currently rebuilding it for the seventh time in fifteen years.
Several dozen experts have tried to explain, he fails to understand.

.

I think I get what you're getting at - what I'm trying to ascertain is what people mean by the term "neutrally balanced". Unfortunately other terms have been introduced to the disscussion here that is at times confusing. Not that that's anyone's "fault" how else can you talk about the subject?

Thanks for posting the link there's some nice information in there.

I did almost spit my tea out when I read the last paragraph about blueprinting though

Engine balance - Wikipedia, the free encyclopedia

As far as I am aware blueprining is not about improving specifications - merely "returning" worn specifications to the specifications of the original design.

So it seems there are conflicting terms everywhere.

But we can at least agree upon the terms here - like we have for left hand and right hand side. Here on this forum (as you know!) left or right is taken as though you are sitting in the car looking forwards. That's great news it stops confusion.

I kind of hope that if we can all agree that neutrally balanced means parts balanced independently from each other then we have at least some common ground from which to discuss things further (if necessary).

Stretch · #38 01-25-2012, 10:19 AM

Quote:

Originally Posted by t walgamuth

I continue to be fascinated by the action here surrounding exact terminology.

Since I am neither Engineer or Attorney exact wording often matters little to me as long as I understand what needs to be done and can communicate to someone who I am asking to do a job for me in language they embrace.

I only care about getting the job done correctly.

BTW, my witness marks on the 84 280e flywheel and crank were not like the ones shown in the picture. I don't have a picture though so this comment is worthless!

Yep - sorry to be pedantic.

I have learnt, however, that often communication isn't as clear as one might hope. As an architect how many times do you think a customer has actually "changed his mind" compared with how many times communication between customer and whoever (I don't want to point fingers!) has failed?

Stretch · #39 01-25-2012, 10:21 AM

Quote:

Originally Posted by vstech

...

IF the crank is internally balanced, the bolt on spinning mass on either end of the crank (harmonic balancer/Flywheel) need to be neutral balanced.
if the crank is NOT internally balanced, the bolt on mass needs to be MATCH balanced.

...

Now that's what I thought was going on - thanks!

whunter · #40 01-25-2012, 01:15 PM

Quote:

Originally Posted by Army

I think I get what you're getting at - what I'm trying to ascertain is what people mean by the term "neutrally balanced". Unfortunately other terms have been introduced to the discussion here that is at times confusing. Not that that's anyone's "fault" how else can you talk about the subject?

Thanks for posting the link there's some nice information in there.

I did almost spit my tea out when I read the last paragraph about blueprinting though

Engine balance - Wikipedia, the free encyclopedia

As far as I am aware blueprinting is not about improving specifications - merely "returning" worn specifications to the specifications of the original design.

So it seems there are conflicting terms everywhere.

But we can at least agree upon the terms here - like we have for left hand and right hand side. Here on this forum (as you know!) left or right is taken as though you are sitting in the car looking forwards. That's great news it stops confusion.

I kind of hope that if we can all agree that neutrally balanced means parts balanced independently from each other then we have at least some common ground from which to discuss things further (if necessary).

FYI
Left, Right orientation is set by SAE standard.

I spent fifteen years working automotive R&D, Durability, Managed development/preproduction/production fleets, worked full build prototype, etc.

Balance type, specification, quality was/is frequently dependent upon application and/or minimum customer requirement.

# Stationary maintenance engine.
# Marine application.
# Heavy equipment.
# Military.
# Commercial truck.
# Automotive.
# High performance/racing.

.

Stretch · #41 01-26-2012, 03:11 AM

SAE standards are great as are standards set by the society of this or the institute of that...

The problem is that they are not made publicly available. These organisations are mostly exclusive organisations - we here, however, are inclusive. We don't charge money for our knowledge we give it freely to help each other out.

If "we" choose to go along with the same convention as the SAE then that's fine by me. We could have, however, just have easily decided to (do a rather silly thing and) make reference to every point on the car with reference to the position of Mecca!

Don't forget we are free men with a few free women here...

t walgamuth · #42 01-26-2012, 06:07 AM

Quote:

Originally Posted by vstech

yup. clear as mud.
sorry...

basically, it's an indicator of the design of the crankshaft.

exact match by the books, meaning the books the machinist uses to compute the crank balance in a specific motor. in other words, (in a race motor at least) the PRECISE weight of the combined weight of the rod/wristpin/piston/ring pack is input to a device for balancing the crank, then the crank is spun by the machine, and it tells where to add or remove mass on the crank to get it to spin without vibration at the RPM the motor is designed to spin.
on a race motor spinning 10K plus RPM, internal balance is a must, or the flex of the crank can be explosive.
for a street car, the RPM is usually under 4K, or only that high for a short burst, and external balance can be OK, but internal is still best.

IF the crank is internally balanced, the bolt on spinning mass on either end of the crank (harmonic balancer/Flywheel) need to be neutral balanced.
if the crank is NOT internally balanced, the bolt on mass needs to be MATCH balanced.

I'll go ahead and toss in an additional balance item in a motor...
that's FIRING order balance... it has little to do with the mass of each part or the crank/piston relationship, it's related to the power stroke/intake/exhaust stroke of each piston and the balance of the others on the crank... inline 6's are naturally FO balanced, 5 cyl's are close, v-8's and v 6's need balance shafts sometimes to throw weight in opposing directions to the FO shake to achieve a smooth chassis...

v6's with sixty degree angle are naturally balanced. if they are nintey degrees you are correct about needing shafts.

any flat engine is naturally balanced.

v12's with sixty degrees are naturally balanced too.

t walgamuth · #43 01-26-2012, 06:25 AM

As far as I am aware blueprining is not about improving specifications - merely "returning" worn specifications to the specifications of the original design.

To me, blueprinting may or may not have anything to do with wear. It is taking the factory tolerance, which is a go no go dimension or weight, such as the piston might have a factory tolerance of one ounce, meaning it could weigh from 20 to 21 ounces, and making sure every part is exactly matched to its common parts, as in the piston example all pistons in a racing application would be matched and taken to the lighter end of the factory spec.

Communications? My dad did not go to college but was a really smart fellow and canny about human interactions. He stressed to me as a child to always communicate on a level that would be understood by the other party you wish to communicate with.

I doubt my dad knew it but Winston Churchill said about communication more or less "Use the simplist word possible to make the point and if possible use the most familiar word". Churchill's speech and his written word is elegant and easy to understand. He may have been the best ever communicator, and as a child stuttered. Perhaps the impediment made him more sensitive than most folks.

In any profession we tend to have our jargon. When dealing with a contractor or a client or a supplier of materials I am careful to include an explanation of the professional jargon in the sentence. Such as the Elevation of a building is a "front view" or a side view, as viewed from a point situated to look straight at the side of the building.

If a contractor or supplier uses their own jargon, I am not shy about requesting the meaning of it.

I make it clear with folks that I am not interested in impressing them with flashy words, I just want accurate communications.

Still, there is always mis-communication. If you are communicating you will have it.

I think more often with my clients I have had trouble with them actually changing their minds.

vstech · #44 01-26-2012, 03:16 PM

Quote:

Originally Posted by Army

SAE standards are great as are standards set by the society of this or the institute of that...

The problem is that they are not made publicly available. These organisations are mostly exclusive organisations - we here, however, are inclusive. We don't charge money for our knowledge we give it freely to help each other out.

If "we" choose to go along with the same convention as the SAE then that's fine by me. We could have, however, just have easily decided to (do a rather silly thing and) make reference to every point on the car with reference to the position of Mecca!

Don't forget we are free men with a few free women here...

I prefer to orient myself in relation to whats closest to the earth 's core

tangofox007 · #45 01-26-2012, 04:53 PM

Quote:

Originally Posted by Army

If "we" choose to go along with the same convention as the SAE then that's fine by me. We could have, however, just have easily decided to (do a rather silly thing and) make reference to every point on the car with reference to the position of Mecca!

Here is what I do not understand:

A person will stand at the front of the car, facing aft, and, all of a sudden, left magically becomes right and right turns into left. If, however, you were to suggest to that person that the headlights just turned into tail lights, they would think you were off your rocker.

If one insists on engaging in asinine practices, at least be consistent about it.