3D-Printed Titanium vs. Forged Aluminum: Brutal Crank Arm Test With Hydraulic Press
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Welcome back to Hydraulic Press Channel - the place where metal meets its match! In today’s high-pressure episode, we’re meshing the realms of advanced 3D printing technology with the robust world of cycling. Witness the clash of the titans as topologically optimized bicycle cranks go head-to-head with their traditional forged counterparts. 🚴♂️💥
Using cutting-edge 3D printing and state-of-the-art topology optimization, we’ve engineered cranks that are built to withstand the ultimate test. Our 150 ton hydraulic press and 240 ton force sensor are ready to challenge the limits of materials science, and you’ll get to see if these next-gen cranks can outperform the classics in a battle of strength and endurance.
Will these optimized wonders revolutionize the way we think about bicycle crank durability? Tune in to see the power of technology push past the conventional, and discover why topology optimization could be the future of cycling components.
Hit subscribe to join our stress-test adventures, smash the like button if you enjoy witnessing the crush, and drop us a comment on what you’d like to see defy our press next.
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Do not try this at home!! or at any where else!!
Music Thor's Hammer-Ethan Meixell
First crack was a broken weld on the test rig!
Was looking for this comment found it
The 600kg give on the first test is the top weld on the test rig breaking you can see it pop at 2:37.
good catch
Exactly what I wanted to say.
Including a quality component as a base line against the 3 variations of the experimental crank was very worthwhile. Great video
I've sometimes been slightly concerned about the cranks and pedals when standing up on my bike on bumpy ground. This shows me there was never any reason to worry.
Ya - me too. Just recently started pedaling hard while standing up.
if you stand up and it feels bad it's usually the frame flexing rather than the cranks, but it's still nothing to worry about.
worry about the calcium apatite/collagen composite structural components .
@@PaulG.x I hear they are the hardest and most expensive to replace.
While the pedal itself will not break under the weight, I've had some bikes pedal mechanism utterly fail and cause a sudden violent release of stress
Jeffrey Hoogland just broke the 1 kilometer record at just over 55s (standing start, 70x15 gearing). In training he was doing 3000w starts, reportedly about 500nm of torque. Assuming a 175mm crank that's about 285kg. His coach has said he's snapped just about every piece of equipment on his bike at some point.
Insane, but that dude still never broke a new crankarm. Impossible…but yeah, still can imagine he goes through a lot of material. Would be interesting to know after what milage they change the chain on the spint training bike. Guess every week, chain snaps are very very unpleasant. And the BBˋs are a problem for that power. But anything else. Maybe the headset, but, cˋmon, those are the same headsets you use on a freeride bike with a 180mm fork 65 head angle and doing 15m drops. No way he destroys that. Maybe he made some bad experiance with chainrings folding, but also not likely. They ride the best stuff and the bike is checked every day. Even the lightes track chainrings usually only brake when bolts are not tight and chain is offset.
That top weld on the stand was what snapped during the aluminium crank test at the start. If you watch around 2:17 you can see it break.
When I was in my teens and 20s, the cranks were never an issue, but I destroyed the crank bearings over a couple weeks and snapped chains regularly and also broke the wheel hub sprags all the time. About 10 years ago I found UK online bike seller on ebay since there was nothing for BMX upgrades in Aus, and they had a splined 3 piece crank kit that used adapters to convert the bearings to standard industrial/automotive bearings. Then I also got a half line chain and never had any failures since. The wheel, I got a good shimano sprag and that's held up fine too.
No fire truck or ambulances needed for this vid. Impressive!
Did they need such things in recent videos?
@@weeksy79 He just recently bought a fire truck. Should figure prominently in some future Beyond The Press videos. 👍
2:15 Looked to me like the first break was on the weld joint of the fixture.
Yes, you can see the whole pedal fixture shift. The aluminum and titanium were about equal in strength, but the titanium I'm guessing is a bit lighter
To be specific the visible spot weld at the 12 o'clock position on the fixture was the break point, later discovered by Lauri but attributed to the steel test piece.
I'm looking crooked or the first snap in the first one was on the holder, not the part? looks like the top welding spot came loose from front perspective
I thought about the same but I think it was the crank since it didn't make any sounds after that. It just gave up after that first snap. Didn't spot that when filming nevertheless. Camera sees everything so much better than slightly scared human from 4meters away :D
2:35 shows the upper welding spot snapping.
@@michaelXXLF - You're right but it happened at 2:17
I LOVED this! One of my favorites of all time, right up there with the bridges competition :)
The aluminium part did not break at 600 kg, it was the top welding point on the test assembly. It seems that the aluminium part started to deform rapidly at ~1000 kg
The Force Sensor doesn't know (or care) who the sponsor is. Prrritti Guud.
Mostly likely both :D
@@HydraulicPressChannel I'm pretty sure the Press didn't care either. 😂
The first welds popped at the very first press
It hat looked like something in the mount had cracked initially on that Aluminum piece. But from the front perspective it's hard to say/see. *8:18 that's probably it, a partial failure initially.
The design makes sense if you want to minimize flexing of the crank arm, not resistance to failure where it meets the crank.
Lots of comments seem to missing this point. It's a complete design, not purely strength to weight in this specific test.
It's really good that you have the facility and equipment to test these in a safe environment so that no one had to smash their balls on the bicycle frame.
I really love the "back to basics" approach to the videos that you are doing these days.
What material was the bottom axle made of? I guess looking at the damage the steel crank did that it was about the same steel as that crank.
The most interesting is how neither of you noticed the backplate snapping.. It gave away on the alu crank, and really messed the results with the steel.
Where?
@@Boogie_the_cat In the video you just watched.
@@Boogie_the_cat it's 2:12, and the slow motion video just after you can see the weld snap.
I don't think it would effect the force result very much, but obviously the setup is not quite the same for the tests so you can't compare them to eachother and the simulation will be a bit different.
@@albr4 It creates more twisting forces, but i doubt it changes the results significantly... maybe 10% or so. Usually Lauri has a keen eye on these things, i was very surprised he didn't notice.
So satisfying to see the simulations match up to reality.
Would like to see carbon fiber and other retail crank arms. This was one of your best!!
Wow that is a cool experiment
I would have liked to see you test a carbon-fibre crank, alongside all the others.
I'm really interested into the computer simulation software you used for the stress test. What is it? a proprietary software from one of the companies linked in the description? Great video as always.
Hooodralic Test Channel upload! Yes!
The backplate is what failed at 600kg, not the crank. All of the cranks failed around the same force. 1,100 to 1,200 it seems.
It's really interesting these are what the computer came up with. The point where they broke seems like a very obvious weak point. Maybe the stress along the rest of the part is really high as well, but it seems like the main body could have taken a lot more force. Even looking at the stress calculations, though I am not entirely sure that I am reading them correctly, it looks like for aluminum some places took around 5 times more force than others. And the peak in some of the really narrow areas was close to 10 times the force. And for titanium it looks even worst at 30times more at the connecting pieces where it failed.
I wondered the same thing when editing the video. I think they were optimized for stress test so maybe they need different type of structure for that?
Never thought I’d see an Etteplan powerpoint template on this channel - cool beans! 😃 (Last company I worked for before retiring.) Getting my hands on that level of a metal 3D-printer these were made with is right up there on my list of things to do when I win in the lottery.
Designing a real part to have uniform stress throughout its entire structure during a test like this would have bizarre consequences to its geometry and its function. Stress distribution through a part is specific to the orientation of the load and restraints. Care needs to be taken when trying to compare the stress results shown for both materials. The gradient scales are not equal, there is no mesh information, there is no deflection information. In fact, HPC, if you can provide a linear readout of the ram's position throughout the tests, that would be very interesting
That's what I was thinking right from the beginning when I saw the computer modeled part right away. The joint is way to weak in comparison to the main body. Of course you want to have a defined break point for safety but the main body, just by looking at it, is more than 5x stronger as the joint where the main force is acting. What's the point in having the main part so much stronger? Imho I think the designer had a faulty requirement wanting the main body have a strength to resist x Nm of force and forgetting the joint requirement to be around 0.5 (factor is debatable) times that force. That's insuring the joint to be the designed break point and still in proportion the the main body. So the main body would not need to be that chunky. And following the biomimetic/biomimicry designs it would be easy to spare out parts of the main body which are not useful to the stress resistance when using a 3d printer. Which also give it a way cooler look than just a whole ellipsoid chunk of metal.
Unless you beef up the connection point it will fail where all cranks fail (if they ever do) at the same amount of force based on material thickness doesn't take a mechanical engineer to figure that out
TO is such an underrated field.
2:18 If you focus on the weld and contraption behind it, you van see it looks like there was also some failure there...the distance from the weld to the edge got a bit bigger, look for it in the clip..(the steel weld on the top on the backplate.)
Would be interesting to see how Cane Creek eeWings stood up (being titanium), along with SRAM's X0 transmission cranks, which were born out of a similar iterative/generative computer model.
problem with eeWings is they are welded. Ive seen them snap at the welds and also crack where they mount to the spindle from use.
The steel one was interesting. Even though it was a 3d printed part, it still had a high degree of malleability compared to its aluminum and titanium counterparts.
Steel is the most flexible option for structural materials. Aluminum can achieve similar strengths with much more rigidity which is why it’s used in aerospace. Titanium has the rigidity and strength of aluminum but the strength of the same cross section of steel, but costs more than the other two combined
I wonder if that's an intended failure mode for these. You would rather the crank arm break instead of the axle twisting, and if it breaks you want it to break in an obvious way that is also not too dangerous.
just a quick comment your english is very good. You're better spoken than some of my friends who only speak english. Cheers from Edmonton Canada!
I snapped a few cranksets when I was a teenager. Never a pleasant landing. Back in the mid-90s, there was a crankset on the market known as Sweet Wings. They were a 4130 hollow elipse with a beefy unified bottom bracket. Downside was they cost more than my bike was worth, but the upgrade after burning through 3 sets of Shimanos, a set of Kookas and finally getting the Sweet Wings... If I would have just bought the Sweet Wings to start with I would have eventually saved even more money.
The first snap was your weld my dude
Pretty cool, but I don't think I could put those weird looking cranks on my bike. I'm not generally into appearances, but couldn't they at least make some nice looking cutouts through the overly strong area in the middle?
I used to race bikes when I was younger and I've broken a lot of things on my bike but the never the crank shaft. This includes breaking several rims and the front fork. I have come down hard in a way that should have put significant force on my cranks but what happened instead is that the force caused my foot to slip off of the pedal and for it to rotate around forcefully only to embed the spikes on my pedal into my leg just under my kneecap. I have the scars to prove it from multiple such events even though it's probably been 30 years since this last happened to me. The weakest link in a bicycle crank shaft is always going to be the human ankle, which will respond to the force by your foot slipping off of the pedal and coming around again to hit you in the shin. Even if one's ankle wasn't the weak point, the crank is going to dislocate tendons or ligaments or even break a bone before it's going to fail due to any forces exerted upon it by even extreme use of a bicycle. I do think that crank design looks really cool, though and that shape is certainly stronger in the shaft. If they wanted to make it stronger, it would be useful to add a bit more bulk to the places where the crank meets the axle and where the crank meets the pedal. The idea about that shape being stronger was certainly right though.
I was very impressed with the results from 3d printed, sintered metal. Much more efficient to do additive manufacturing. Apparently plenty strong for the application too!
Yeah I think people assume a lot when they say forged parts are stronger. Seems that there's no disadvantage here with the aluminum part. Obviously the shape is different, but that's the point of the 3D printed metal, isn't it?
Check behind to see if there any cracks she started to laugh 😂😂
I’m pretty sure the best reaction would be your girls reaction, she about popped herself there! 😂
I got a question. What is your press cylinder made of? @hydraulicPresschannel
Steel
Had to watch this as I have FSA Gossamer cranks on my bike. Good to know that my “massive” power output is well within the stress limits 😅. That era of Gossamer is at least 10 years old as well.
I guess i'm changing to FSA Gossamer on my Enduro bike 😀
I don't get this shape. Momentum of force is highest at axle, so momentum of inertia of crosssection should be highest there, not in the middle, this is not a bridge?
Was it me or was that first snap with the Aluminum actually from the spot weld on top pulling off of the jig?? spot welds are and can be strong but with over 1 ton on it plus leverage it can be a lot. (Edit) at 10:54 you can see that side shot and you can see that the top spot weld is not attached at all. How much does that defect affect the results? You can also see for the Molded test that he added a spot weld to the bottom of the Jig but didnt notice the top was not attached at all which is not a easy spot at all.
The crank bolt is a self extracting nut so leave the outer cap on and extract the 8mm nut it'll pull the crank off so no need for the hammer. 👍
I would love to see the same test with a set of 48 spline BMX cranks. The mountain bike spline system has always been the weakest point. Keep up the great work 👍
Yeah I rode BMX for many years of my life and I never broke a crank. I broke my front fort and several rims though.
thanks Lauri :)
Awesome. 😊
I would really like to see the exact shape of the forged aluminum one printed in those 3 materials tested
I liked seeing how well the finite element analysis compared to the real world. These were nice failures. I had two catastrophic failures, both times it was the pedal axle (steel?) snapping completely off. Once was while trying to get across a busy highway when an oncoming car was going faster than I first thought, and when it broke I thought I was going to be road kill. I'm not sure if that was the time I somehow ended up halfway under a car without having been run over or if that was from slipping on wet (greasy rainwater) paint. But both times the sharp stub of the axle cut my lower leg deep enough to get a nice anatomy lesson. I doubt I was exerting a ton of force even though I was pulling myself down with the handle bars so I assume it was a manufacturing defect or ...crap forgot the word...from repeated stress over time. So it is interesting to me that in the video the crank broke instead of the pedal axle. I didn't pay $1000's for the bikes but they weren't cheap either.
"Metal fatigue" is the term you were looking for. And, yes, that seems likely. If you still had the parts, you could easily tell -- fatigue causes small cracks to grow slowly and so the fracture surface is hard and grainy, almost like a broken rock. Normal failure causes the metal to bend first, so the surface ends up stretched a bit and sort of smeared. Often you get a combination of both; the material cracks until what's left is too weak and then it bends.
test the chain strength on the hub
Best part is that practically speaking, they're optimizing for a 70ish kg person riding a bicycle. Even if you double that to accommodate a fat American (I'm from the South, if I can see it and live with it, I can say it), you're still well under the failure point for a rider cranking on that pedal with full body weight. In competitive cycling, they min-max the weight, so I'm sure some genius could shave a few grams more for competitive advantage (and to sell a bike for $1000 more)! Love what you guys do! Don't stop crushing things!
But, I think a person can impress a downward force above his weight if standing up and pedaling, or if taking bumps while standing on the pedals?
Hannah's Yelp is a perfect audio indication of point of failure moment.😂
Looks like there's plenty of room for further mass optimisation since those parts are all way stronger than they need to be. I wonder how the aerodynamics of the generatively-designed parts compare to the traditional? Also, great demonstration of why high-end suspension in cars is done with forged aluminium parts!
The amount of dynamic torque that a rider can put on a crank is a lot higher than you'd think. Someone above said Jeffrey Hoogand puts 285kg of force on his cranks during launches. Now imagine he's doing that and the front tire hits an obstacle. People still snap those forged aluminum cranks that take 1100kg before yielding BTW.
Ooohhh.... You might be on to something interesting with this... You could start testing engine connecting rods. Test their compressing strength, and also their pulling strength (tensile?? or whatever). See which one(s) are best! Mind you, there's *_so many_* brands, and different alloys, different designs... It could therefor get expensive... _However,_ you'd tap into a new viewer market as well, and that *could* work to your benefit! 🤷♂️☺️
Sure come a long ways since the 90s... i bent quite a few cranks on hard hills back in the day.. Looks like maybe the forged ones stronger than leg bones these days. dunno how i feel about these weird ones..
Yep, I remember bending and snapping cranks and bbs back in the day. Modern ones I really don’t worry about hurting. They’re so strong.
Mrs hydraulic press is the first lady in history it seems who likes being in hubby's workshop. Keep up the great posts to you both!!!
wooooooooow, its fantastic 😀
You are a very good KZheadr.
Topology... I've been speaking english (poorly) my whole life & I'm just learning that word now 😂 Language is hard! Neat video as always, sending love from Boston Massachusetts!
the first crack at alu test, was the top wielding that hold the axel :D and not the arm it self
And to think 3-D printing in metal didn't exist until just a few years ago! 🤔
I wish Lauri did test a Shimano 12S M7100/M8100 crank. I bet it would snap at 300kg at the pedal insert. I've destroyed two of those cranks already in 2 seasons, no more Shimano for me. Saints won't work as I need less than 32T chainrings for cranking uphill on a 29-ner
Now that’s a strong bottom bracket
I’d imagine if you could put 2400lbs of force on a bicycle pedal you could easily power a semi truck 😂
If we assume these were 2/3rds of a foot long then it's the equivalent a 1600 ft lb engine dyno reading. That's a healthy Cummins diesel engine.
All your tests AFTER the aluminium are void due to the top weld breaking on the backing plate. I'm surprised you didn't see it, as it was still broken on the factory pedal test. This would have been giving you twisting force, not just a rotational force on the shaft.
9:26 ish Your english is getting more accurate. I wont say better cause I like the "ed" at the end rather than the native spoken "'d" Great video. More science, more better :) more screams
Speaking as an engineer: it doesn't make any sense to have part of the crank with so much cross sectional area and so much moment of inertia that it's stressed way less than the failure point. That means you've got excess capacity that you're not making use of. Why not shape them so the whole thing is close to the failure stress all the way throughout?
As an engineer myself, I know that you need to have the design criteria before being able to properly evaluate a design. This looks like it was designed for stiffness rather than just for strength in this one specific test.
Yayyyyy Finland 🇫🇮
Wow! Thanks so much. But I think the $10 pedals I used to buy were a bit cheap. By the time I was half way healed from snapping one pedal off, ild get slammed into street by a another broken pedal. After being shown a bad time by the asphalt enough I saved my money up and bought a $100 pair of pedals. I believe they had lasted 10 times longer at the time my crank broke at the pedal. Later some mountain bike crank outlasted my pedal. Ah, teenage memories. Such good times. Except when it felt like a car would come up out of the street to meet me. I guess it was a car.. I used to excercise in the gym with 1500 pounds on the leg extension machine. It's nice to know I could apply more force than what I worked out with with just one leg. By the way, did anyone know one can get scraped up being slammed straight down into the asphalt? I lost more races that way. I only lost races that way.. I think I'll shift down from the highest gear if I should ever get to relive my teenage years and eliminate some of those single bike accidents.
The failure at 10:48 is interesting. Is this crank a plastic coated forging or hollow design? It looks like the internal arm section of the crank failed.
I think the pedal just slipped on the end of the press tool somehow, and the crank arm was suddenly twisted a bit more.
Not sure, would be nice to see the band saw mod on that one. @@jjohnston94
just go to show that manufacturers of cranks, can go further to losing more weight on their cranks, no one puts out even 700kg force pedalling, nevermind 8 to 900kg.
I wonder why they are testing Ti cranks that are not popular or available. How about testing the Ti 3D printed EE Wings cranks?
I love your accent. Sounds like Peter Sagan
How about a carbon fiber crank?
i'd love to see these parts cast out of iron, steel, and aluminum so we could see the strength difference between cast metals and 3d printed/forged parts.
i'd bet that the shock of the weld popping damaged the aluminum. bet it could go higher.
The first crack on the aluminum crank was something in your test rig snapping, not the crank. You can see it move when you show it from the back side.
Yeah after watcing the whole video I can tell that the rig snapped on the first test. It broke the rest of the way on the steel crank, but the aluminum one started it off. I think the aluminum 3D printed crank might be the strongest given this detail.
Great testing...but this makes me realize that cranks are overbuilt. What's the maximum transient force an elite cyclist can apply to a pedal? 200-300 kg? I'm guessing it isn't much more than that. A considerable weight savings is apparently achievable. Damage from obstacles might need to be addressed.
You are using Altair software to display the FEA results and their free for makers software Inspire also includes topology optimization features that anyone can use. But you don't mention this and you remove the logos from the software.. hmm why?
It's a Crank Bro! 😂
Really, strenght test and the equipment is only tag welded on few spots. Just why, why?
Is it not completely wrong what the computer design came up with? Sharp stress points but the middle of the arm is completely solid. I think the stress model should show pretty even colors, then it would be the lightest design possible. In my opinion this crankarm looks a bit like a solution in search of a problem...
I don't think they're solid. Look at the longitudinal sections at 0:38. You can see voids with reinforcement. It's possible that this is a first iteration in finding the optimum shape. But I agree.
These are not a product for sale I think, but rather a university exercise done in collaboration with the 3D printing company who sponsored the video.
This is also only testing in a single plane of stress. There could also have been a stiffness requirement in the optimization that would drive material in places where it may not be necessary for strength.
@@jjohnston94 You are certainly right. I meant "solid" as "sturdy".
"If voracious brute force was not the answer, you did not use enough of it." It worked for Mom, and it has never failed me. (Her cooking was used to interrogate prisoners.)
I love how brilliant of an engineer Lauri is almost gets lost in English 😆👌
Repeated stress around 250Kg would represent a realistic loading - with my mass! 😆
Now put them all under the really powerful press & flatten them or use the worm tool for a real mess
every one of those withstood far more torque than a cyclist could ever put on them. These tests basically determined which would hold up best in a heavy crash!
I can't wait to see the new press just demolish everything
So the moral of the story is optimised forged aluminium for the win
Forged aluminum cranks win!
Std crank wins for me!
No human weighs that much, so i'm comfortable knowing my crank arms aren't going to snap off (I use a tricycle, and the crank assembly is a one-piece), or in my case, split in two! 55-57 kg ain't heavy enough to do that (and I don't pull up hard on the handlebars when hill climbing).
Test carbon cranks!
"Probably forged"... there are glued ones out there under a worldwide product warning. 🤭
At those pressures, breaking the cranks is the least of your problem. Your real problem will be the frame of the bicycle bending and cracking.
The students definitely made some questionable boundary conditions in their topo optimization FEA. Or some weird keepout zones.
Agreed, it's obviously tough to judge it without knowing thier optimization criteria.
@@kjdude8765 sure. It might have been "it must look like a fat leaf" and "it must have very uneven stresses" lol
Ma conclusion c'est que ces manivelles de pédalier sont sur dimensionnées. Il y a moyen d'enlever de la matière et donc du poids.😊
Takes few years of training to be able to break those actual pedals during a race 😁
If you manage to do that you'll be asked for a blood, urin and saliva sample on the spot.