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08-23-2020, 07:56 AM | #1 |
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Crankshaft Counterbalance Weight
I need your help again. It seems I have a lot of questions these days. Actually, I am working on presentations for my local club, so questions arise I never thought of before.
At this time I am building a presentation about engine vibrations which leads to this question. What is the weight of one crankshaft counterbalance weight before it goes onto a crankshaft?
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08-23-2020, 11:08 AM | #2 |
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Re: Crankshaft Counterbalance Weight
which style of counterweight ---i have some of the ford design shrink on ones i could weigh
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08-23-2020, 11:10 AM | #3 |
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Re: Crankshaft Counterbalance Weight
Thanks Kurt. Please weigh one for me.
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08-23-2020, 11:49 AM | #4 |
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Re: Crankshaft Counterbalance Weight
Early '28, so-called 'beaver-tail' cranks weigh 27 lbs.
Later A's weigh 29 lbs. B cranks, 39 lbs. C cranks, 46 lbs. BB cranks, 58 lbs. (pressed-on, 1" wide weights. So called because these were added by authorized Ford rebuilders when a 'B' engine was rebuilt, mostly on 'B' trucks. I may have some weights I planned on putting on a 'B' crank, I'll look for them. A & B engines have naturally occuring vibration points, at about 800-900, 1600, and 2300 (this from my menory) They are heard more than felt, in most engines they aren't noticeable, and usually when being driven, not sitting in your driveway. Last edited by Jim Brierley; 08-23-2020 at 11:54 AM. Reason: Added info |
08-23-2020, 01:26 PM | #5 |
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Re: Crankshaft Counterbalance Weight
Interesting inquiry, I found old picture of B-B counterweight drawing some years ago.
I then modeled up in solidworks, from a pretty bad sketch. I come up with mass of #4.87 per counterweight. As an interesting side note, the Miller racing engines found that you could not get enough counter weight to balance out the harmonics. If you look at pics of them, the counterweight is full radius and 180 degrees opposite the rod journal. John
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08-23-2020, 04:31 PM | #6 |
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Re: Crankshaft Counterbalance Weight
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also. crankshft turned 10/10 under weighs in at 24.8 with no counterweights. Second crankshaft also turned 10/10 under with the above weights added weighs in at 37 lbs. |
08-23-2020, 04:42 PM | #7 |
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Re: Crankshaft Counterbalance Weight
What exactly are the counterbalance weights for. What effect would it have on my engine if it was not counter balanced.
Gerry Birch Bay WA. |
08-23-2020, 05:23 PM | #8 |
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Re: Crankshaft Counterbalance Weight
Is it possible to “turn” a crankshaft as opposed to grinding.
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08-23-2020, 06:00 PM | #9 |
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Re: Crankshaft Counterbalance Weight
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08-23-2020, 08:13 PM | #10 |
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Re: Crankshaft Counterbalance Weight
From what I have heard, what ever you do to put counterweights on an A crank, you won't have the optimum. Right now, I don't remember the name of the guy who attaches shrink on weights to the crank, then puts more weight on the side of those. I think that setup would be heavier than the others and closer to ideal.
Clearly, shrink on weights will weigh more than the weld on ones because they go all the way around the crank flange without adding any more counterweight effect. I don't think we have enough information to properly answer this question.
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08-23-2020, 09:10 PM | #11 | |
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Re: Crankshaft Counterbalance Weight
Quote:
It would do well in parades. |
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08-23-2020, 10:29 PM | #12 | |
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Re: Crankshaft Counterbalance Weight
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08-23-2020, 10:49 PM | #13 | |
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Re: Crankshaft Counterbalance Weight
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A heavy total weight, crank assembly limits the performance of any car not only by total weight added to the car but MOSTLY because of poor spool up. This is usualy of little concern in a vintage street machine though. |
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08-24-2020, 08:46 AM | #14 |
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Re: Crankshaft Counterbalance Weight
Thanks Ken Parker. This is exactly what I asked for:
I have s set of counterweights from Berts. Bolt on then weld the ends. Set of 4. Each one weighs 3.1 lbs total weight of 12.4 lbs. They are the samee thickness as the counters on the crankshft - 5/8" thick. Also crankshft turned 10/10 under weighs in at 24.8 with no counterweights. Second crankshaft also turned 10/10 under with the above weights added weighs in at 37 lbs.
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08-24-2020, 10:32 AM | #15 | |
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Re: Crankshaft Counterbalance Weight
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08-24-2020, 10:41 AM | #16 |
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Re: Crankshaft Counterbalance Weight
Gerry Allen, counterweights increase the life of the crank & bearings. You will feel little or no increase in smoothness while driving.
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08-24-2020, 12:44 PM | #17 |
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Re: Crankshaft Counterbalance Weight
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08-24-2020, 10:50 PM | #18 |
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Re: Crankshaft Counterbalance Weight
What kind of lathe would you need to “Turn” crankshaft journals. How accurate finish can be obtained. Does anyone have more info and pictures?
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08-25-2020, 12:55 PM | #19 | |
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Re: Crankshaft Counterbalance Weight
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I have a Storm Vulcan 15 crankshaft grinder, -and my biggest lathe is a Howa 16" x 59". Both machines weigh around 4,500 pounds, yet the crank grinder is a much more rigid machine comparing the two. When trying to achieve a quality finish, rigidity is a must. So my point is you would need a very robust lathe to achieve a finish you could be happy with. Using a tool-post grinder on that lathe would be a plus. |
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08-26-2020, 02:04 AM | #20 |
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Re: Crankshaft Counterbalance Weight
Would this one be rigid enough? It is a 42 inch throw facing and boring lathe weighing 10.5 tons without the face plate shown. There is no tail stock on this type but another face plate or a precision steady can be mounted on the rear.
My son and I are just fettling and setting it up in our collection. I am just joking because I have no intention of machining a crankshaft in it. I have trued up several Model A rear flanges in another of our lathes, after straightening the cranks in a press. A crank grinder is something missing in our collection of machine tools. |
08-26-2020, 07:13 AM | #21 | |
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Re: Crankshaft Counterbalance Weight
Quote:
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08-26-2020, 02:50 PM | #22 | |
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Re: Crankshaft Counterbalance Weight
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We roughed the SAE6150 billet in the lathe. Left about .050 to finish in the crank grinder. After finish grinding to size we had the journals nitrided. While it could be done, it would take many hours to finish the journals to size in a lathe due to the slow rpm needed bacause of the billet weight and off balance situation. The engine was very successful for 2 race programs and then the block broke through one of the main webs due to lack of support from the cylinder bank we cut off. The engine had a half of a V8 Hilborn injector, a Racer Brown ST2 grind on the cam and a Corvette head. The engine was in a 1947 Kurtis midget chassis. |
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08-26-2020, 05:59 PM | #23 |
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Re: Crankshaft Counterbalance Weight
Brett, we did not get a tool post grinder with this behemoth. But there was one listed in the pre-war catalogue.
The machine has been "rescued" from the scrap heap so may never be used properly, but we may refacea flywheel etc just for fun. The 4 jaw chuck is too heavy for our 1/2 ton jib crane shown lifting the motor. SAJ in NZ |
08-27-2020, 08:35 AM | #24 | |
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Re: Crankshaft Counterbalance Weight
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It definitely is a monster, no doubt. I would love to have a big Monarch or ?? lathe like that however I just don't have the real estate to spare just to say I have one. |
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08-27-2020, 08:56 AM | #25 |
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Re: Crankshaft Counterbalance Weight
Counterweights, when properly positioned and sized, will reduce reciprocating and rotating vibrations to less annoying frequencies and severity (amplitude). Lightening the flywheel / pressure plate promotes vibration about the rear engine mounts, and may manifest itself in clutch chatter. The flywheel and pressure plate are a gyro with a 82 pound rotor, and they oppose changes in motion of the engine as a whole, and the crankshaft.
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08-27-2020, 02:17 PM | #26 |
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Re: Crankshaft Counterbalance Weight
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08-27-2020, 06:29 PM | #27 |
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Re: Crankshaft Counterbalance Weight
In reference to the comments about big lathes, my father worked in engineering all his life and on some big stuff. I saw a picture once (I don't know what became of that picture) of one of the lathes his company used. It was so big that the saddle had ladders for a man to access the cross slide and another to the top slide. The top slide had a hand rail around it to prevent the operator falling the considerable distance to the floor. I guess they had to use a crane to change the cutting tool and power to move the slides.
What they used something like that for, I don't know but I'd love to see it now. I guess it ended up making about 1,000 Toyotas!
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08-27-2020, 07:23 PM | #28 | |
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Re: Crankshaft Counterbalance Weight
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A steel Co. in this area had one similar back in the 50's. |
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08-27-2020, 07:38 PM | #29 |
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Re: Crankshaft Counterbalance Weight
Here is a lathe I ran at a tourist railroad for awhile. They had an even bigger one they used to turn drive wheels off of steam engines.
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08-28-2020, 04:03 AM | #30 |
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Re: Crankshaft Counterbalance Weight
Wow folks! I will never say "mines bigger than yours" again.
I will stick to challenging 90 year olds to arm wrestling in future. SAJ in NZ |
08-28-2020, 09:15 AM | #31 |
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Re: Crankshaft Counterbalance Weight
Cass Scenic Railroad, Cass West Virginia, 2019.
Last edited by GPierce; 08-28-2020 at 09:20 AM. |
08-28-2020, 01:47 PM | #32 |
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08-28-2020, 07:56 PM | #33 |
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Re: Crankshaft Counterbalance Weight
Turning propeller shafts makes sense. Come to think of it, I do recall dad talking of doing that and cutting gears for such like heavy applications. He served his apprenticeship during the war cutting gears for the military. Probably have to buy them from China these days and who looks like the most likely adversary???? What could go wrong, I wonder.
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