01:40:30am, Saturday, May 04, 2024
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counterweighted crank
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ds
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wondering if weighting an IH 414 crank is needed on lss. If so who is best and who are my options |
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Re: counterweighted crank
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Twister 07
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Are you running deisel or alcohol? Deisel should not need to be counterwaited. I would do it to an alky. |
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Re: counterweighted crank
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Registered: 03/23/2010 Posts: 46 |
How about the dt360 cranks say to about 4500-5000 rpm?? |
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Re: counterweighted crank
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ds
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any peticular reason. what is the actual gain |
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Re: counterweighted crank
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cranky student
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Please refrain from giving anymore poor advice. Both diesels and alkys need to be checked for correct counterbalance. Even stock cranks where you use all stock everything including RPMs can have counterweight issues. Its not always what's best for the crankshaft sometimes its what's best for prodction costs. |
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Re: counterweighted crank
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ds
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what do you recommend on a IH 414 crank with aluminum rods |
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Re: counterweighted crank
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Twister 07
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A 414 or any of the IH crankshafts when using light rods and or pistons would benifit from counterweighting. If you are running heavy rods and pistons like a deisel would be, a 414 and 436 should not need it. I do think the 466 crank runs much smoother being weighted. When you lighten the rotating mass I am told is when weighting is most benificial. Cranky student is correct in his claim that every crank should be checked for balance. Although the question was about counterweighting and not balancing. I do not know if the dt360 must be counterweighted to run those rpm's but I know of one that runs much smoother with the weights. |
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Re: counterweighted crank
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Twister 07
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If you have more questions about counterweighting I would call Terry Blackbourn as he is one of the best in the buisness with an IH engine. He use to run a 300 series as well so I know he would be able to help with advice on that as well. |
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Re: counterweighted crank
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Meeting?
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Hey twister07. See ya Sunday. Now you should know who I am. lol |
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Re: counterweighted crank
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cranky student
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Please reread what I said. You evidently don't get it. I said the counter balance must be checked. Counter balance is achieved by adding or removing counterweight. Only two ways on an inline 6 to do this: calculation or computer simulation. You are right. Best thing to do is go to a builder who knows what they are doing. Do any of them know what they are doing? Good question. We have found that there is not physically enough room in a block to add enough counterweight, but 80 percent sure beats 30 percent. All our research has been on a diesel. |
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Re: counterweighted crank
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engine guy
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I wrote this a while back for the same question so here it is again.
Typically each pin on a crank is balanced to 100% of the rotating mass (rod big end, 2X bearing shells, rod bolts, crankpin) and 50% of the reciprocating mass (piston/pin/rings/small end of rod). This offers the best compromise to packaging weights on the crank and acceptable reliablity of the crank itself. The purpose of the counterweights is to cancel the centrifugal force of unbalanced rotating mass on the pin, and this reduces crank bending, which takes load off the main bearing shells. And the centrifugal force goes up with the square of the RPM.....so a crank that was designed to run at 1800 RPM, will have high bending (meaning high deflection especially in the center mains) and low bearing life at 5000 RPM. Older stock tractor cranks were not counterweighted since the RPM was low (meaning centrifugal force was low enough that it didn't effect main bearing life), and main pins and crank pins were very large making the crank stiff enough so bending and torsional modes were completely out of the operating RPM range. There are 2 issues with adding counterweights to a stock inline 6 tractor crank. The first issue is that any mass added to the crank may lower the natural frequency of the crank in torsion and bending. It could lower it enough that it occurs in the operating RPM range of the engine. If the engine RPM and the natural frequency line up on each other, the deflection is greatest and could destroy the crank and/or main bearings quickly. Also reducing the recip mass, and the flywheel/clutch mass is a big help here too. The second issue is that adding weights to a stock crank adds stress risers everywhere, which means many more places for cracks to start. To properly balance a crank, you need to have your piston and rods figured out with proper masses for each. And an idea of your peak RPM. If you go to a shop and they don't ask you for that data, find a new shop. And crank balance doesn't care if it's diesel or alcohol. The argument that a diesel doen't need balancing makes no sense. In fact a diesel is more important to balance since the recip and rotating mass are typically much higher than the equivalent alcohol parts. |
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Re: counterweighted crank
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Scott Muller
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Engin guy is correct but as far as most industial engines go it is not possable to add enough counter weight to run at high engine rpms. like stated above, 80 percent is better than none. as far as the stress risers there are ways to eliminate most of them with proper treatment of the crank. I have worked with counter weighting cranks for many years and can tell you if properly done the engine will run smoother and have virtully no bearing issues caused by balance. this does not fix poor assembly, wrong tolerances or any other issue you may have but it will not be the cranks fault. |
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