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  #16 (permalink)  
Old 05-28-2008, 09:57 AM
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Quote:
Originally Posted by Riot Racing
I decided to take some crappy pictures with the camera on my phone. The lighting wasn't too great so they came out bad.

The holes you see drilled in the counterweights came like this when i purchased the crank. The crank is damaged which can't be seen. There is scoring where the rod journals would be. I may repair this in the future, again as practice. I think a grinder is needed for the rod journals.

View#2
Looking at the counterweight which has the drilled holes pointing up in the air. This is the edge I was planning on knife edging. Does that make sense? This seems like the edge which has the most mass. AND in the case that the crank hits the oil, this seems to be the likely side to hit the oil.

View #4 & #5
Are to demonstrate the practice machine work I have done. This was done on a manual lathe. The material is extremely hard. If I were to conintue to machine this area we are talking .010" cuts at a time, maybe .015" cuts.

ALSO, in these views you can see a metal ball which was likely pressed in. What the heck is this for?

View #1


View #2


View #3


View #4


View #5


View #6
[img]
http://img2.putfile.com/thumb/5/14722411032.jpg[/img]


What do you guys think?
I am beginning to see that your concept of knife-edging is a little skewed from the actual and literal practices that are done. Keep in mind that the material around the metal ball is all you have to work with to compensate for the material you take away from the counterweight. It will be very easy to take off way too much couterweight in the method you are using, than you have material to offset that with around the metal ball to bring it back into balance. Also, the face of the counterweight, as you are cutting in your lathe, is not the surface that is knife-egded. It is only the side edge of the leading and trailing edge of the counter weights. Look at the Crower website to get more of a visual as to the methods that are currently being used by the racing industry. The metal ball in the crank is to block off the oil passage where the rod and main journals were drilled at the time of manufacture. So, the material you can remove from that end of the crank to balance is some what limited. If the crank you are actually going to use has this ball as well, care must be taken not to losen or remove this ball, because lose of oil pressure and engine failure will result. Many people assume, as you also said yourself, that the crank rotates through the oil standing in the oil pan. It can never contact or "slap" the oil. The level of oil in the pan isn't even close to touching the counterweights or rotating assembly. At racing engine speeds, severe engine damage can and will occur if the crank or rotating assembly is allowed to "slap" through the oil. I've seen some racers try to create a budget high capacity oil pan, and just added 3 more quarts of oil, instead of installing a deep sump pan for more capacity. The results were very destructive. Many people have come to believe that is the reason for knife-edging, but it isn't. It mostly is to make the square and blunt edges of the counterweights, "cut" the air and reduce windage inside the crankcase cavity it is in. Much like an airplane wing. Crower actually makes the leading edge of the couterweights on their crankshafts rounded, and only the trailing edge comes to more of a point....hope that helps with your project!

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  #17 (permalink)  
Old 05-28-2008, 12:57 PM
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crankshaft......

HI,the little ball you see,is actually MALLORY METAL,its a very heavy dense metal,its used when a crank is out of balance,used on the lighter side of crank throw.......
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  #18 (permalink)  
Old 05-28-2008, 04:06 PM
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Quote:
Originally Posted by boatbob2
HI,the little ball you see,is actually MALLORY METAL,its a very heavy dense metal,its used when a crank is out of balance,used on the lighter side of crank throw.......
If he will shine a pin light into the oil hole in the rod journal, he will see a hole intersecting from the rod journal to the main journal. That hole is drilled from outside the crank rod journal to the main. The ball seals the hole from loosing oil pressure beyond the journal, other manufacturers use a pipe plug to seal the hole. If he continues to knife edge his good crank in the manner he is using in the photos, and removes way too much material from the counterweights than he can offset with in the rod pin area, he will soon be very familiar with the use of Mallory metal and how much just one piece costs to install....
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  #19 (permalink)  
Old 07-04-2008, 12:55 PM
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Quote:
Originally Posted by CNC-Dude
If he will shine a pin light into the oil hole in the rod journal, he will see a hole intersecting from the rod journal to the main journal. That hole is drilled from outside the crank rod journal to the main. The ball seals the hole from loosing oil pressure beyond the journal, other manufacturers use a pipe plug to seal the hole. If he continues to knife edge his good crank in the manner he is using in the photos, and removes way too much material from the counterweights than he can offset with in the rod pin area, he will soon be very familiar with the use of Mallory metal and how much just one piece costs to install....
I can tell if you are being a Smart ***** or not. So I will go ahead and assume you are not, cause being a jer behind a computer screen is pointless.

I milled out a section of the counter weight in order to remove the ball. It is now out and one less thing I have to worry about.

Now, I have been trying to machine the counter weights flat on a lathe for some time now. Obviously this material is very hard. I think I could machine about .005" off every cut. More than that, and the cutting bit moves and the crank being held in a three jaw chuck slips.

So SINCE I AM JUST PRACTICING. I don't have to worry about destroying this crank or removing too much metal. I am just getting use to machining this item. So machining things flat is the easiest way so far.

How do pro shops knife edge a crank? Are they grinding or machining? If they are machining how are they doing this? Does anyone actually know?
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  #20 (permalink)  
Old 07-04-2008, 07:22 PM
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Quote:
Originally Posted by Riot Racing
How do pro shops knife edge a crank? Are they grinding or machining? If they are machining how are they doing this? Does anyone actually know?
Static balancing the crank on knife edges is the correct terminology. The crank will be static balanced when you can place it on the knife edges and it will not roll regardless of where the crank is positioned.

Removing weight to get the balance is NOT done by setting the crank in a lathe and removing material (weight) from the side(s) of the counterweights. This is what it appears you are doing.

Weight is removed as shown in your own photos #1 thru at least #3 by using a drillbit on the outer diameter of the counterweights. If weight needs to be added, then a hole is drilled in the outer diameter of the counterweights and filled with Mallory metal that is much heavier than the material that was removed by the drilling.

Note: CNC-DUDE was not being a smart*** as you thought. He told you correctly.

I give you a lot of credit for your desire to learn something new and for asking for info from fellow enthusiasts. Many won't bother to try to learn anything or (shudder) to ask for additional info. There are many very knowledgeable folks on this board that are more than willing to help.
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  #21 (permalink)  
Old 07-05-2008, 05:15 PM
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Quote:
Originally Posted by Frisco
Static balancing the crank on knife edges is the correct terminology. The crank will be static balanced when you can place it on the knife edges and it will not roll regardless of where the crank is positioned.

Removing weight to get the balance is NOT done by setting the crank in a lathe and removing material (weight) from the side(s) of the counterweights. This is what it appears you are doing.

Weight is removed as shown in your own photos #1 thru at least #3 by using a drillbit on the outer diameter of the counterweights. If weight needs to be added, then a hole is drilled in the outer diameter of the counterweights and filled with Mallory metal that is much heavier than the material that was removed by the drilling.

Note: CNC-DUDE was not being a smart*** as you thought. He told you correctly.

I give you a lot of credit for your desire to learn something new and for asking for info from fellow enthusiasts. Many won't bother to try to learn anything or (shudder) to ask for additional info. There are many very knowledgeable folks on this board that are more than willing to help.
I hope I wsn't rude to CNC rude. Maybe I am overly sensitive...

I am not tryignt o balance the crank by machining it. By machining the sides I was testing the material hardness to figure out how machinable this item is. After the help of the forum members I feel confident about how to balance the crank shaft.

NOW i need to figure out the best way to machine it. This is what I am looking for help with now. Do you think I should start a new thread to make things more clear?
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  #22 (permalink)  
Old 07-05-2008, 05:42 PM
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Quote:
Originally Posted by Riot Racing
I had posted a similar discussion to find anyone who has kinfe edge their crankshaft on their own.

I have a two cylinder crankshaft from a motorcycle that I am experimenting with. It is trashed so I dont mind messing with it and IT WILL NEVER BE INSTALLED.

I wanted to practice machining the crank to see how difficult it is. What I need to know now is:

HOw are the crankshafts balanced? Are the counterweights weight equalt to the weight of the entire connecting rod assembly?

In order to fine tune the weight balancing I have seen them drill holes into the counter weights then cap the holes off. Is this the best way?

I want to understand how the balancing process is done in order to determine how much I want to remove from my counter weights.
I want to have a well balanced crank in the end.
This is your post #1 and clearly states that you wanted to understand how the balancing process is done in order to determine how much you want to remove from the counter weights.

Quote:
Originally Posted by Riot Racing
I am not tryignt o balance the crank by machining it. By machining the sides I was testing the material hardness to figure out how machinable this item is. After the help of the forum members I feel confident about how to balance the crank shaft.

NOW i need to figure out the best way to machine it. This is what I am looking for help with now. Do you think I should start a new thread to make things more clear?
Ok. You have a new question.

Since you are trying to remove material from the face of the counterweights and have the crank in a lathe; use a carbide cutting tool (either brazed on or insert style will work). You have already determined that you are unable to remove more than about .010-.015 from the face at each pass. Some of this is due to the material being cut. The RPM and the feed rate could be work hardening the material making the machining even more difficult. Some of this may be due to your cutting tool. Some may be because of the chuck you are using, as you stated that you have 'spun' the crank in the chuck. Some may be due to the drive mechanism of the lathe. If it is a lighter duty belt driven lathe you can stall the spindle easily. You may be attempting to remove too much material at each pass (depth of cut) or the feed rate may be too heavy.

I would ask, what's the rush? You will be able to remove the material you wish using what you have. Tighten the chuck better. Continue with light cuts. Slow the feed rate some. Definitely use a carbide cutter. A negative rake on the cutting edge will also help. If you are using a carbide lathe tool that has replaceable inserts; try using ceramic inserts.

Next best way is to forget using the lathe and use an OD grinder with coolant.
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  #23 (permalink)  
Old 07-06-2008, 02:24 PM
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Quote:
Originally Posted by Frisco
Ok. You have a new question.

Since you are trying to remove material from the face of the counterweights and have the crank in a lathe; use a carbide cutting tool (either brazed on or insert style will work). You have already determined that you are unable to remove more than about .010-.015 from the face at each pass. Some of this is due to the material being cut. The RPM and the feed rate could be work hardening the material making the machining even more difficult. Some of this may be due to your cutting tool. Some may be because of the chuck you are using, as you stated that you have 'spun' the crank in the chuck. Some may be due to the drive mechanism of the lathe. If it is a lighter duty belt driven lathe you can stall the spindle easily. You may be attempting to remove too much material at each pass (depth of cut) or the feed rate may be too heavy.

I would ask, what's the rush? You will be able to remove the material you wish using what you have. Tighten the chuck better. Continue with light cuts. Slow the feed rate some. Definitely use a carbide cutter. A negative rake on the cutting edge will also help. If you are using a carbide lathe tool that has replaceable inserts; try using ceramic inserts.

Next best way is to forget using the lathe and use an OD grinder with coolant.
I don't have access to an OD grinders so I will keep trying with the lathe I have.

I am goignt o try some different inserts and some different styles of inserts to make this work.
Any recommendation on the type of insert that you think is best for Hard material?

Also, because the counter weights are a circle there is a gap between the cuts that occurs. This puts stress on teh cutting tip.
I'm goign to try to dump lots of coolant and change my cutting tool.

Ill update next weekend.
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  #24 (permalink)  
Old 07-07-2008, 12:13 AM
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Whew!

I am hoping that you know that knife edging a crank is totally useless from a power standpoint...but whatever.

The crank is either cast iron or cast steel if its small two cylinder engine, the machining process is done between vee blocks on a tool type milling machine with a long series cutter. The head is angled on the mill so you can get the correct angle with the milling cutter.

Doing this on a lathe would be a pain in the butt, but possible with a two cylinder crank. I would love to see your cross slide clamping setup for doing this on the lathe, must be interesting.

Balancing the assembly is done with specialized equipment but with a two cylinder crank with 180 degree throws you could do it with a knife edge roller balancer as someone posted.

I'll say it again...you do know that knife edging a crank is a waste of time from a power standpoint...ummmm nevermind.
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  #25 (permalink)  
Old 07-07-2008, 09:51 AM
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[QUOTE=Riot Racing]I hope I wsn't rude to CNC rude. Maybe I am overly sensitive...

Naw cuz, were cool.....

Last edited by CNC-Dude; 07-07-2008 at 04:12 PM.
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  #26 (permalink)  
Old 07-08-2008, 12:27 AM
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Quote:
Originally Posted by 4 Jaw Chuck
Whew!

I am hoping that you know that knife edging a crank is totally useless from a power standpoint...but whatever.

The crank is either cast iron or cast steel if its small two cylinder engine, the machining process is done between vee blocks on a tool type milling machine with a long series cutter. The head is angled on the mill so you can get the correct angle with the milling cutter.

Doing this on a lathe would be a pain in the butt, but possible with a two cylinder crank. I would love to see your cross slide clamping setup for doing this on the lathe, must be interesting.

Balancing the assembly is done with specialized equipment but with a two cylinder crank with 180 degree throws you could do it with a knife edge roller balancer as someone posted.

I'll say it again...you do know that knife edging a crank is a waste of time from a power standpoint...ummmm nevermind.
I know there is no power gain. Engines aren't only about more power! I need faster revs and less rotational mass is a big help.

How would you properly hold the crank in a vise if it were on a mill?
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  #27 (permalink)  
Old 07-08-2008, 12:29 AM
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[QUOTE=CNC-Dude]
Quote:
Originally Posted by Riot Racing
I hope I wsn't rude to CNC rude. Maybe I am overly sensitive...

Naw cuz, were cool.....
What do u think about 4 jaw chucks post?
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  #28 (permalink)  
Old 07-08-2008, 10:16 AM
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[QUOTE=Riot Racing]
Quote:
Originally Posted by CNC-Dude

What do u think about 4 jaw chucks post?
You can tell in just a few sentences if a person responding to a question is speaking from experience and knowledge, or is just trying to jump into a discussion to hear themselves on the forum with no real helpful or additional input. He is absolutely correct on all the points he has given to you. There is little, if any HP gain to be seen from knife-edging,and,or lightening the crankshaft. However, most aftermarket crankshaft companies feel that there is some benefit to it because they offer there cranks with this feature on request. The most benefical modification for your autocross application(in my opinion), would be to lighten the crank as you have already mentioned. No HP gain with that either, just quicker acceleration out of the turns. A second off of your lap time here and there will add up. Using your lathe to remove some counterweight around the circumference of the crank is perfect for this. As you have already discovered, the crank is very hard. A slow RPM and carbide inserts will need to be used. The production of aftermarket billet crankshafts uses CNC lathes that have "live" tooling that is capable of machining in 4-5 different axis' at the same time, creating the knife-edged couterweights and sculpted shapes that they have. Your lathe only has 2(3 if you count the cross slide), which will make using it for knife-edging impossible. As 4 Jaw mentioned, a mill would be more practical for knife-edging. A V-block fixture will bolt to the table of the mill. The crank will rest with the front and rear mains setting in the V. This will allow you to rotate the crank as needed to machine the desired counterweight. Also, you will need to rotate the head of the mill to the angle you have chosen to create. Carbide tooling also will be helpful. A second alternative is a 6" angle side grinder to cut the angle on the counterweights(very tiresome and labor intensive), but it works just as well. Having said all that, I will say this in closing. Their is a fine line in how much counterweight you can remove and still have enough material left in other places to rebalance the crank, without having to resort to using mallory metal to fix it! Proceed cautiously....

Last edited by CNC-Dude; 07-08-2008 at 10:22 AM.
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