EVERYTHING about the CRANKSHAFT - Function | Manufacturing | Different types | Forged | Billet
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Published 2020-03-29
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How it works? All internal combustion engine crankshafts have main journals and rod journals. Here are the main journals, these are what the crankshaft itself rotates on and are held in the engine block by the main bearing caps. Rod journals, a.k.a. crank pins or big end journals are where the big ends of the conrods are connected to. Rod journals are connected to main journals via crankshaft webs.
Now, the distance between the main journal center-line, and the rod journal centerline is called the crank throw, a.k.a. crankshaft radius. And this measure determines the stroke of the engine. The stroke of an engine will be 2 times the crank throw.
At the end of the crankshaft we are going to find a flywheel flange, this is where the flywheel is bolted onto. The flywheel with it's heavy round mass smooths out the pulsation of the combustion inside the engine occurring at different times. On the other end f the crankshaft is the nose. This is where the crankshaft pulley is attached.
These are the counterweights. The operation of an internal combustion engine generates strong rotational forces, and the mass of the piston, piston pin and rings and the connecting rod moving up and down at high speeds generates a very significant force that is exerted onto the crankshaft. The counterweights have the task of balancing out these forces. We will talk about counterweights in more detail later in the video. The holes you can find in the rod and main journals are oiling holes. Oil coming thorough the engine block into the crankshaft and out these. Another very important design element of the crankshaft is the radius fillet. Engineers take great care when designing this, because a proper radius fillet is key to a crankshaft not breaking apart. The radius fillet is key because it spreads the load and relieves the stress in what would otherwise be an extremely common point of stress fracture on any crankshaft.
Crankshaft manufacturing process
There three main manufacturing processes for crankshafts are Casting, forging and CNC machining. Casting is the most cost effective processes and in general results in the weakest art. Cast parts are often more brittle, that is to say they have a lower tensile strength and lower ductility compared to forged and machined billet parts.
Forged crankshafts - the forging process of a crankshaft involves a large crankshaft sized billet being heated up to about 2.500 -2.700 degrees Fahrenheit and then put into giant presses with dies in them that apply anywhere from 150 to 250 tonnes of pressure to shape the heated up billet into a rough forging. The rough forging is then machined and heat treated to create the finished crankshaft. You can tell a crankshaft has been forged by looking for wide parting lines and signs of grinding on those lines. The main difference when it comes to forged crankshaft vs cast is that the forging process compresses the grain structure of the metal into a much more confirm one compared to a cast part which results in greater strength and ductility.
Billet crankshafts - when it comes to billet crankshafts there's no casting, or forging or anything. You take a big billet and machine away material until you're left with a crankshaft, that's it. This takes a lot of time, and a lot of machining is needed to make a billet crankshaft which is why billet crankshafts are often very expensive and often reserved for racing and other extreme applications. The great thing when it comes to billet crankshafts vs forged is that there are infinite design possibilities for billet!
Crankshafts also often undergo heat and surface treatments such as induction hardening, tufftriding (tuftriding). When it comes to lubrication we have two different types. Cross drilled crankshafts and straight shot oiling crankshafts. To combat drag created by crankcase windage, crankshaft counterweights are sometimes knife-edged
Here's a summary of crossplane vs flatplane crankshafts: Crossplane cranks are usually larger and heavier so they have a lower max rpm, but they make the engine run smoother, generate more torque and sound different. Flatplane crankshafts engines are more prone to vibration, but are also more compact and capable of higher max rpms.
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All Comments (21)
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Here we go again. This guy showing up in my recommendations teaching me good, usable stuff.
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this is brilliantly clear, comprehensive without being too long, and doesn't skimp on all those little details that people usually leave out because they assume you already know it. in short, you efficiently assemble all the information into a cohesive semantic network, like a knowledge bomb ready to be loaded into the human brain. ten out of effing ten
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I was feeling very cranky, then I saw this video, and now my head's spinning. The information is very eccentric, the big end is talking to the little end, the counter weight arguments are strong though. The forces are bearing down.
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Finally a series dedicated to engine parts!
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You're a great teacher and you're amazing at focusing on thw details we actually want to know instead of taking a pointless class at school that teaches usless info. Thanks for your dedication and work on our behaf
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I've been a rev-head for 65 years, but I've learnt more in the last couple of years than decades of tinkering, thanks to your excellent videos. Thank you! Keep 'em coming...
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As a Manufacturing Engineer from an automaker I can confirm that you videos are awesome! Brilliant job.
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All those thumbs down are those who think they know it all and could explain this manufacturing process better. Good video bro!!
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Years ago on a forum that I frequented, a member who had some basic knowledge of physics, but no practical knowledge of the workings of internal combustion engines proposed an idea: A solid tungsten crankshaft... He couldn't understand that, for one, you need an alloy to be able to withstand the forces on the crank, and two, the amount of power necessary to spin that mass would be astronomical. He also couldn't understand why you want a lightweight crank, thinking more mass meant more power - and while more mass does mean more stored energy, that stored energy wouldn't be useful in a street or race car scenario. It was a funny thread, it went on for a very long time and became quite a big joke, ultimately with ideas of cranks made from depleted uranium or even dark matter...😂 All that to say, fantastic video! I love how clearly and concisely you explain everything. It's a wonderful, easy to follow format. Thank you!
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Hello from POLAND, thhanks for every films you made.
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This has become my favorite YouTube channel. You provide more technical information in short time, without getting confusing or tiresome, than any car channel I’ve found so far.
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1 minor language nit: the -et in fillet is pronounced like the -et in bet, rather than the -et in ballet. The counterpoint for an outside edge is called a round. It is exactly right that both are used to distribute the stresses more broadly, rather than to concentrate them at the inside or outside corner of a 90 degree intersection, thereby avoiding a stress riser that overtaxes the joining point, leading to failure of the material composing the joint (in this case, the cast iron or forged steel of the crank journal). Very well done presentation - thorough, and well-explained. Nice job!
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Just ran across your video, I've built engines since I was 12, and I have to give you a very good kudos for this video. It's just detailed enough for the common joe, and complete enough for people to get a reasonable grasp without being too complicated. Great job, keep it up, I think you'll do very well !!😉
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One of the best YouTuber of the world..... knowledge... humour... unbelievable explaining most difficult things in the most easy way ..nice way to speak..no music that is distracting.. unbelievable various subjects of videos.. pictures videos that help understanding.... for the best for car subjects ... Hope you have enough time and money to give your fire...like Prometheus...
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I've randomly started getting tons of your videos in my recommendations. I think that means you're about to blow up. Keep it up, great content.
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A quick correction. Both cross- and flatplane V8s with a 90° bank-angle fires evenly four times per revolution, aka every 90° of rotation. Difference beeing the flatplane has even spaced power-pulses on each bank (so basicly two typical I-4s offset 90°) and the crossplane does not, it has an uneven distribution of pulses per bank. The total being the same. At short, the only thing the crossplane is better at is second-order vibrations. And no, the flat plane does not make less torque, displacement for displacement, all else being equal. Infact a flatplane makes more torque and power generally over the entire range, due to the even spaced (on each bank) pulses, giving better exhaust scavenging. (even exhaust scavange can be done on crossplane engines, but is very impractical due to exhaust header space constraints, and the runners becomes so long, that you get deminishing returns).
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How am I just now finding this channel?! Everything a car nerd is looking for 👏 here goes all my free time.
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I couldn't imagine that a chamfered hole will be so significant for an engine part. Excellent job!
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You are single-handedly keeping me sane! Keep'em coming!
