So Jim, whens the book comming out?JimGreek wrote:The select few Barry, the select few!
Jim K.
-
la_strega_nera
- Platinum
- Posts: 494
- Joined: Tue Feb 21, 2006 10:05 pm
- Location: Sunny Euro-Brisney
SEARCH the forum you lazy user!!!la_strega_nera wrote:So Jim, whens the book comming out?JimGreek wrote:The select few Barry, the select few!
Jim K.
moahahaha, finally.
Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
-
terminator
- Silver
- Posts: 25
- Joined: Sun Aug 07, 2005 9:35 am
Unfortunately, true factory figures were never public regarding this matter, fuelling all kinds of speculation. Widely different opinions even within the specialty community (none of which qualified in engineering terms)have justifiably given engine balancing the 'black art' fame. I urge anyone seriously interested in the subject, to analyze the forces involved in a simple single cylinder engine. Everything will then become clear.
Jim K.
Jim K.
Im in the progress of building a racing 3.0 24v engine, im searching for the correct balance factor, for me the mentioned 33,3333% looks wrong:
for any V-engines you take at first 100% weight of the rotating mass - thats the lower end of the rod including bearing/bolts.
From this its obviously, that at first you not only have to bring the rods to same weight, but you have to bring all the 6 lower ends to same weight ( and consequently the small ends ) If you look at stock rods, you can see, that they have done it at factory the same way, because they have on the big AND small end castings, where you can grind weight away.
Thats all for the rotating mass and is very clear ( always 100% )
The second to be added amount of weight ( to the total weight of the bob weight ) is for the reciprocating mass what means:
small end of the rod & complete piston assembly
Now this is exactly the percentage, for which we all are looking for. Sadly the V6 engine cannot be balanced 100% perfectly, because of the basic construction, so a compromise has to be found, what means that the used %tage is balancing the engine for the used rpm range only.
Therefore it would be best to know the factory balance factor.
Im looking for this factory balance factor, anybody out there does it know ?
For example, all v8s with 90degree crank throws ( not the 180 degree ones ) and some american v6es use generaly 100% rotating and 50% weight of reciprocating mass, but some racing applications use, what is called "overbalance" with 52-54% weight. When "overbalance" of only 2-4% is used, the running engine tends to vibrate around 3-4000rpm, but have no vibration around 8000 rpm, where it would destroy the racing engine. So for a stock v8 is used 50%, because this engine doesnt run to 8000rpm, and on the other side the racing engine doesnt run in the 3500rpm range, but needs to be vibration free higher up.
Please mention, that for higher rpms, MORE weight is used, contrary to what has been stated here.
Please mention too, that in discussions are percentages between 30-50 %, suggested, but only 2-3% more or less can allready make a big difference.
I was researching for the right balance factor of our v6engine the net for weeks without results, but have found a lot of datas for v8 engines, they dont state numbers from 40-60% ! So obviously the numbers between 30-50% cannot be right, and 33,3333 % from the WHOLE assembly sounds totaly wrong.
I believe that there exists an exact number for the specific alfa v6 engine, it could be even slight different for 2.5s and 3.0s and that for racing applications that number can be slightly higher ( or lower, contrary to v8s ? )
I believe that this % was found by the factory by search and discovery, until they were satisfied with the smoothnes of the engine for the used rpm range.
Probably one of the professionals here ( Jim Greek ? ) could help us here out of misery ? First if all i stated is correct and the %age he knows of ? ( 100% rotation & ??% reciprocating mass = bob weight ) How much have you used on yours ?
When searching the web and specially for the alfa v6, a lot of wrong info is out there. Like that the crankshaft has to be balanced allways together with the flywheel and pulley. This is wrong and right. At first you balance the crank on its own, with bob weights only, BECAUSE the alfa v6 crankshaft is 100% internally balanced opposite to believe.
This balancing leaves the engine balanced, until you RUN THE ENGINE.
If you run the engine, the power delivered to the Crankshaft by means of pressure to the pistons introduce further vibrations.
The flywheel and pulley have countherweights, which are exactly 180deg on the opposite side together and they represent exactly the same amount of mass, when divided by the radius they are mounted, that means: the smaller offset weight on the flywheel sits on a larger radius then the bigger weight on the front pulley, where the radius is much smaller . Statically the flywheel/crankshaft/pulley are balanced, but on a dynamic balancer, they will cause an inbalance on 1.st and 4th main bearing, which have to be: exactly the same amount, exactly 180 degree opposite together. The reason for this added imbalance lies in the construction type of the crankhaft. The v6 is basicaly a 2x 3 zylinder straight construction and because when cyl 1 is up, on the opposite side no. 2 and 3 are down and vice versa(3 up, 2 and 1 down). This would cause a strong vibration when running( the crank would like to go up and down in front and back. This is no rotational vibration, but fore and aft. Against this vibration the imbalance on the pulley and flywheel acts like a balance shaft on some 4zyl engines.
This is also the reason, why the weights are on the external flywheel and pulley, if they were on the crankshaft, you couldnt balance the crank at all.
From this its easy to see, that before lightening a flywheel and pulley, it should get zero balanced by their own and brought back to this balance after lightening. Very important is also the position of this imbalance in relation to the middle of the crank lenghtwise. Look at the imbalance position of the 3.0 Alfa 75 pulley and the 3.0 164 pulley, the weight is on the 75 pulley way more in the front - this affects amount and position of the weight of the flywheel imbalance ! This same counts for the longitudinal position of the flywheel imbalance on a 2.5 and 3.0 flywheel.
This explains also why you must heavy modify the 75 3.0 flywheel in combination with the original 24v 3.0 pulley when using a 24v engine in a 75 car.
Hope the given info makes sense for you all and im not far away from truth.
I hope to get some comments on this posting especially from you hardcore guys, who have allready done some balancing ( your bob-weight % ???? ) by themselves.
for any V-engines you take at first 100% weight of the rotating mass - thats the lower end of the rod including bearing/bolts.
From this its obviously, that at first you not only have to bring the rods to same weight, but you have to bring all the 6 lower ends to same weight ( and consequently the small ends ) If you look at stock rods, you can see, that they have done it at factory the same way, because they have on the big AND small end castings, where you can grind weight away.
Thats all for the rotating mass and is very clear ( always 100% )
The second to be added amount of weight ( to the total weight of the bob weight ) is for the reciprocating mass what means:
small end of the rod & complete piston assembly
Now this is exactly the percentage, for which we all are looking for. Sadly the V6 engine cannot be balanced 100% perfectly, because of the basic construction, so a compromise has to be found, what means that the used %tage is balancing the engine for the used rpm range only.
Therefore it would be best to know the factory balance factor.
Im looking for this factory balance factor, anybody out there does it know ?
For example, all v8s with 90degree crank throws ( not the 180 degree ones ) and some american v6es use generaly 100% rotating and 50% weight of reciprocating mass, but some racing applications use, what is called "overbalance" with 52-54% weight. When "overbalance" of only 2-4% is used, the running engine tends to vibrate around 3-4000rpm, but have no vibration around 8000 rpm, where it would destroy the racing engine. So for a stock v8 is used 50%, because this engine doesnt run to 8000rpm, and on the other side the racing engine doesnt run in the 3500rpm range, but needs to be vibration free higher up.
Please mention, that for higher rpms, MORE weight is used, contrary to what has been stated here.
Please mention too, that in discussions are percentages between 30-50 %, suggested, but only 2-3% more or less can allready make a big difference.
I was researching for the right balance factor of our v6engine the net for weeks without results, but have found a lot of datas for v8 engines, they dont state numbers from 40-60% ! So obviously the numbers between 30-50% cannot be right, and 33,3333 % from the WHOLE assembly sounds totaly wrong.
I believe that there exists an exact number for the specific alfa v6 engine, it could be even slight different for 2.5s and 3.0s and that for racing applications that number can be slightly higher ( or lower, contrary to v8s ? )
I believe that this % was found by the factory by search and discovery, until they were satisfied with the smoothnes of the engine for the used rpm range.
Probably one of the professionals here ( Jim Greek ? ) could help us here out of misery ? First if all i stated is correct and the %age he knows of ? ( 100% rotation & ??% reciprocating mass = bob weight ) How much have you used on yours ?
When searching the web and specially for the alfa v6, a lot of wrong info is out there. Like that the crankshaft has to be balanced allways together with the flywheel and pulley. This is wrong and right. At first you balance the crank on its own, with bob weights only, BECAUSE the alfa v6 crankshaft is 100% internally balanced opposite to believe.
This balancing leaves the engine balanced, until you RUN THE ENGINE.
If you run the engine, the power delivered to the Crankshaft by means of pressure to the pistons introduce further vibrations.
The flywheel and pulley have countherweights, which are exactly 180deg on the opposite side together and they represent exactly the same amount of mass, when divided by the radius they are mounted, that means: the smaller offset weight on the flywheel sits on a larger radius then the bigger weight on the front pulley, where the radius is much smaller . Statically the flywheel/crankshaft/pulley are balanced, but on a dynamic balancer, they will cause an inbalance on 1.st and 4th main bearing, which have to be: exactly the same amount, exactly 180 degree opposite together. The reason for this added imbalance lies in the construction type of the crankhaft. The v6 is basicaly a 2x 3 zylinder straight construction and because when cyl 1 is up, on the opposite side no. 2 and 3 are down and vice versa(3 up, 2 and 1 down). This would cause a strong vibration when running( the crank would like to go up and down in front and back. This is no rotational vibration, but fore and aft. Against this vibration the imbalance on the pulley and flywheel acts like a balance shaft on some 4zyl engines.
This is also the reason, why the weights are on the external flywheel and pulley, if they were on the crankshaft, you couldnt balance the crank at all.
From this its easy to see, that before lightening a flywheel and pulley, it should get zero balanced by their own and brought back to this balance after lightening. Very important is also the position of this imbalance in relation to the middle of the crank lenghtwise. Look at the imbalance position of the 3.0 Alfa 75 pulley and the 3.0 164 pulley, the weight is on the 75 pulley way more in the front - this affects amount and position of the weight of the flywheel imbalance ! This same counts for the longitudinal position of the flywheel imbalance on a 2.5 and 3.0 flywheel.
This explains also why you must heavy modify the 75 3.0 flywheel in combination with the original 24v 3.0 pulley when using a 24v engine in a 75 car.
Hope the given info makes sense for you all and im not far away from truth.
I hope to get some comments on this posting especially from you hardcore guys, who have allready done some balancing ( your bob-weight % ???? ) by themselves.
-
Greg Gordon
- Verde
- Posts: 1552
- Joined: Mon Nov 29, 2004 7:06 pm
The 33.3% is way off.
It's not fair to ask Jim K. to give out those numbers for free. He has spent a lot of time and money coming up with the optimal numbers, and I know for a fact his numbers are perfect.
We should all buy Jim's book. I seriously doubt he has a chance of coming out even financially on this project, and I think he is coming out way behind with the time factored in.
I have found that most balance shops seem to default to a bob weight number that's right for a G.M. V6. This number results in a minor vibration between 2000 and 3000rpm. Otherwise it's smooth. The numbers from Jim result in a perfectly smooth motor from idle to 7000rpm which is as high as I have tested.
Greg
It's not fair to ask Jim K. to give out those numbers for free. He has spent a lot of time and money coming up with the optimal numbers, and I know for a fact his numbers are perfect.
We should all buy Jim's book. I seriously doubt he has a chance of coming out even financially on this project, and I think he is coming out way behind with the time factored in.
I have found that most balance shops seem to default to a bob weight number that's right for a G.M. V6. This number results in a minor vibration between 2000 and 3000rpm. Otherwise it's smooth. The numbers from Jim result in a perfectly smooth motor from idle to 7000rpm which is as high as I have tested.
Greg
Hear Hear!Greg Gordon wrote:
It's not fair to ask Jim K. to give out those numbers for free. He has spent a lot of time and money coming up with the optimal numbers, and I know for a fact his numbers are perfect.
We should all buy Jim's book. I seriously doubt he has a chance of coming out even financially on this project, and I think he is coming out way behind with the time factored in.
Greg
Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
Thanks for the help Greg, I hope future readers can appreciate the point.
Rosso, I would like to say a few words re. our V6 rotating assembly: the crank is the externally balanced type, meaning part of the counterweights is placed in the flywheel and pulley. The reason this is done is to be able to have smaller crank counterweights in order to fit in the specific crankcase internal dimensions. This 3-part assembly is thus indivisible. There is a way to convert it to an internally balanced type as routinely done in the US for some big V8 similar assemblies. In that case, you can use any light flywheels and pulleys independently of the crank. An important point to note is to never put the crank by itself on the balancing machine and try to balance it, unless you happen to be a couple of bus stops away yourself!
Jim K.
Rosso, I would like to say a few words re. our V6 rotating assembly: the crank is the externally balanced type, meaning part of the counterweights is placed in the flywheel and pulley. The reason this is done is to be able to have smaller crank counterweights in order to fit in the specific crankcase internal dimensions. This 3-part assembly is thus indivisible. There is a way to convert it to an internally balanced type as routinely done in the US for some big V8 similar assemblies. In that case, you can use any light flywheels and pulleys independently of the crank. An important point to note is to never put the crank by itself on the balancing machine and try to balance it, unless you happen to be a couple of bus stops away yourself!
Jim K.