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From a study I was helping do research for, that actually doesn't sound all that much worse than the accepted normal rate of injury.
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Mar 24, 2016 23:00
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Saga posted:Head tube on a Trek mountain bike, presumably 6000 series Al. Possibly putting a rigid fork on an 18 year old frame was not the best idea but at least I found out the right way. ... that makes me reconsider the idea putting a rigid fork on my 10 year old aluminum Trek. Is that one of the hybrid ones or what?
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May 31, 2016 19:48
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Saga posted:Not a hybrid, it was their normal base model aluminium MTB frame. It was also 18 years old and well used, so you probably have another decade to go on yours! Oh, I'm just riding on asphalt and bike trails and stuff, so screw it, proceeding to not worry.
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May 31, 2016 21:30
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Fun fact - you can actually do a DIY metal disintegration machine with a tombstone stick welder, cheapie hand engraver, and some plumbing fittings. It's the single scariest tool I own though.
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Jun 2, 2016 18:19
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Production car rotors used for racing just kinda do that sometimes. It's not "bad" metallurgy, per se, but a lot of steps applied to racing brakes that aren't bothered with for production stuff. You have a huge amount of heat input and maybe there's unrelieved stresses in the cast iron, or stress concentrations from machining or something ... nothing that would show up at temperatures seen on public roads, but pushed hard, there ya go. What's really loving scary is some cars like 1st gen RX-7s where the bearing carrier is part of the same casting as the rotor. One SCCA roadrace class called E Production ends up with slicks, widebodies, reaonably good power NA... and stock calipers and rotors, so everything pushed pretty drat hard. After A couple incidents where cracks from rotors made it to the bearing carrier and made the wheel depart the car (saw one at Road America at turn 5) they legalized stock sized but 2-piece rotors.
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Jun 20, 2016 17:22
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Boaz MacPhereson posted:
Yeah. EProd rules give me a headache. 2250 pound car (with driver) making about 230hp at the wheels through a dogbox, with about 10" of tread width of honest-to-god slick on the track... with 10 inch rotors and stock cast iron calipers. Then again, it always provides a point of perspective for all those people who go on about the absolute necessity of big brake kits. BlackMK4 posted:This happens to race rotors over time too Oh sure, but you have to admit the odds get a bit better when the parts are intended for their use.
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Jun 20, 2016 20:02
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jamal posted:2-piece floating rotors are a good idea for a track car. A solid rotor will want to kind of dish out due to thermal expansion. A lot of 2-piece rotors are just bolted together and don't allow any float between the disc and hat, so sometimes this happens: For some reason, I find it kind of funny that it was the cast iron rotor that failed instead of the aluminum hat. But then maybe the hat was effectively heatsinking into the wheel...
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Jun 23, 2016 23:34
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Slavvy posted:How about a traditional taper bearing that, instead of being pre-loaded by the locknut, is instead pre-loaded by a shim of specific thickness which sits between the two bearings? Cause that's what a kia rio has! I've actually heard of that as a bandaid fix for lovely spindles in roadracing on little British cars - idea being that if you set the preload with shims you can torque the nut to the point where the spindle is in tension. Kia, employing racing fi... I can't even finish that sentence.
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Jul 11, 2016 14:10
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Ferremit posted:What the gently caress kind of suspension setup is that even TRYING to be? Its not 3 link, Its not triangulated 4 link, its not 5 link. Not to take away from the general awfulness of that, but it sure looks like a triangulated 4 link to me...
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Aug 12, 2016 14:32
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Having opened rotaries looking like that, yep, that's a flood victim. *quickedit* For bonus points, that's an S3 13B. mekilljoydammit fucked around with this message at 02:08 on Aug 23, 2016 |
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Aug 23, 2016 02:05
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Enourmo posted:I seem to recall they were all done that way until the various series started requiring they be mounted to the chassis instead. There were a lot of early attempts to use wings mounted direct to suspension that were... not adequately strong. *quickedit* CAT INTERCEPTOR posted:TBH, I would not be surprised that in 10 years time, the whole Chinese Crap will be nothing more than a racist footnote, given the speed of Chinese development and the sheer amount of highly educated and motivated individuals China has a huge supply of. It's not all industrial espionage that is fuelling China's development. ... working for a small engine / generator company that does our production in China and dealing with the results of their engineers trying to solve problems... I'm... less sure than you seem to be. mekilljoydammit fucked around with this message at 23:41 on Aug 29, 2016 |
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Aug 29, 2016 23:38
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BloodBag posted:... I've already spoken on magnetic shocks in this thread... I missed this, does it boil down to "gently caress magnetic shocks"? Because from research I've been doing trying to come up with good shock solutions, gently caress magnetic shocks.
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Oct 9, 2016 17:41
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kastein posted:They are cool great technology until they fail after the warranty is up and you have to blow 4 figures on replacing them. According to a shock guy at Penske, they couldn't get them to hold to professional racing style tolerances for a whole race because of wear - it's pumping an abrasive liquid around and just eats the pistons. For OEM use they apparently just put up with it and possibly just fiddle things to compensate until it gets too bad.
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Oct 10, 2016 01:26
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30,000 miles? Interesting, that's even shittier than I expected.
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Oct 10, 2016 13:53
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Seat Safety Switch posted:The big downside with Macpherson struts from a performance driving perspective is that as you compress them, the arc forced by the single control arm forces them to gain camber (jack up your car and watch the wheel trace an arc instead of going straight up and down). Most of what you wrote is right, but on this it's the other way around, actually. Macphereson struts, the angle of the tire relative to the chassis doesn't change much compared to wishbones - so when the body rolls during cornering, the outside tire, which is doing most of the work, heels over onto the outside edge unless you put a bunch of static negative camber on it. Wishbones you can tune so that the camber changes as the body rolls, keeping the tire in the orientation you want under cornering while not having to sit on the inside edges of the tire while going straight.
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Oct 14, 2016 14:33
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I wish I could post poo poo from work, because in the R&D arm of a small engine maker, you see a lot of horrible mechanical failures - on the order of "... ok, the Chinese factory won't ever make it to the right specs, so how can we engineer around that?" Ugh. One that took the cake was a test engine a week or two ago. Guy who graduated in the spring with a Masters degree built it. "Uh, this thing isn't running right at all..." head bolts weren't more than finger tight. "Are you sure you torqued everything *else* on this?" "100% sure, no problem." "Are you actually sure?" "Yes, just run it." Two hours later it windowed the block because one of the controd big ends had the bolts back out. Yeah, last time I trust that guy with anything.
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Nov 5, 2016 15:35
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Plinkey posted:This is why you don't give design engineers tools. He's supposedly a test engineer. Despite having no background in engines at all. I suspect nepotism.
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Nov 5, 2016 23:51
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The problems are sort of two-fold. Number one is the corporate culture in China is that they'll change suppliers at the drop of a hat, so you get the whole "... well yes, I know we had perfectly functioning parts from the old supplier that were within tolerance and worked properly and the new supplier is making parts that don't work, BUT THE NEW SUPPLIER CUT PRICES BY A TENTH OF A CENT! Oh and no we won't tell you we changed suppliers, so good luck diagnosing why stuff suddenly doesn't work." thing. Number two is that culture is such that workers will move across the country for ten cents an hour raise, so every holiday something like 60% of the work force just won't come back. So good luck building up any expertise. The test engineer guy is ... look, he needs an entry level position, and we're too small to handle that. Before him, I was the only one that hadn't worked at two or more other engine companies, and I faked it by doing race engine stuff and obsessively studying the subject. Oh well.
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Nov 6, 2016 00:47
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the spyder posted:*stuff* Ha ha ha ha ha ha ha gently caress sequential turbos.
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Dec 2, 2016 01:20
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Weird thing is that those VW jacks are kind of the standard old school rally car jack.
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Dec 18, 2016 15:11
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jamal posted:Fine, right? Except they did a version with poly bushing at the front, which sits on that vertical pin. OEMs do a bushing like that, where bushings flex with control arm movement instead of rotate, but it's always a soft and flat part that can articulate easily. But these guys decided to put a stiff bushing on a rod end, so this happened to some guy driving down the highway within a few months of having the arms installed ... jesus, it's almost like companies selling suspension poo poo like that should actually hire engineers...
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Mar 9, 2017 15:24
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EightBit posted:I wish. My Jeep has a load of these, known as Johnny joints, in the control arms. Greasy loving mess, each one. http://www.spcalignment.com/component/content/article?id=291 Relatively new.
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Mar 10, 2017 17:05
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the spyder posted:Bookmarked. Those are awesome. I like that they have a size that will fit in FB trailing link locations, with a thread that will accept standard stock car swedged tube sizes. Not that I have a specific use in mind or anything.
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Mar 10, 2017 19:30
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Drilling into the aluminum control arm for the shock pot doesn't make me thrilled either...
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Mar 11, 2017 13:54
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jamal posted:Update: loving shitheads. Chalk that up for another business to never do business with.
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Mar 13, 2017 19:34
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bolind posted:Wasn't there also some 4WD BMW that had the front driveshaft run through the oil pan? In fairness, lots of stuff does that.
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Jul 21, 2017 14:19
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Memento posted:Crosspost from the OSHA thread. "We've struck oil! Wait, 5w20?"
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Aug 3, 2017 15:42
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IPCRESS posted:No? Holding displacement and engine technology constant*: You need longer crank throws to get more torque. Uh, you need to keep adding asterisks to make any of what you said true enough to be useful. Friction losses are basically an insignificant driver of powerband shape compared to a buttload of absolutely critical aspects you didn't mention at all. Here's a hint - BSFC (torque per displacement) has a lot of determining factors but is mostly focused on efficient combustion, and powerband shape (more or less torque than HP) is going to be mostly affected by gas flow and whether combustion is efficient at high RPM. If you hold cylinder head port design, camshaft timing, intake and exhaust tract tuning, combustion chamber shape/volume and heat rejection (off the top of my head) constant, then the friction differences from piston speed might start being important.
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Oct 22, 2017 19:34
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Combat Theory posted:... (effective middle pressure) ... Out of curiosity, where did that terminology come from? I understand fully the concept but I've never heard that part of the equation referred to as anything other than Brake Mean Effective Pressure.
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Oct 23, 2017 12:28
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Fo3 posted:It's also about how many power strokes per rev. Which is why I mentioned 6s. You are never going to do as well with a 4 cyl no matter the crank stroke. ... it's not as long as you're comparing 4-strokes to 4-strokes... smoothness yes, sure (if you want think of it mathematically, the deviation from mean torque) but actual torque (average over all engine cycles) no, cylinder count doesn't automatically matter. Now, in a real pragmatic sense, there's a lot of evidence to support displacement of around 400-650cc/cylinder for best BMEP with "modern" 4-valve/cylinder heads and combustion chambers - much smaller and you start paying for displacement with friction (why you don't see many small bore V8s anymore) and much bigger and you start running into combustion issues. So you run into things where a smaller bore 6 can have better combustion efficiency than a 4 of the same displacement, but it doesn't have squat to do with number of power strokes. And this is where you pull out examples of 6s making more torque than 4s, I pull out counterexamples, you say "but that one's more efficient than that one!" and I say "... well, yes, it depends on other factors than power strokes was my whole point." Just to save us both some time. 
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Oct 23, 2017 14:15
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Combat Theory posted:I blame going to a German University. Most of the terminology for individual parts we learn in English automatically, but the scientific stuff is very colored by language. That makes sense - I haven't delved into German language technical papers so haven't come across that.
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Oct 23, 2017 16:17
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DogonCrook posted:So how do you add horsepower without adding torque? Like whats the most effective way to make that trade when rebuilding an engine? BlackMK4 posted:RPM Short answer, that. Longer answer, at higher RPM you have less and less time to get air into the engine - double the RPM and the valve is open for half the time (measured in seconds not degrees). So to have more air flow in at higher RPM you increase how long the valves are open (cam duration) and ideally make it easier to flow in (ported head ports). But having the intake valve open longer means that at lower RPM your effective compression ratio is lower, so you up that. And intake manifold and exhaust manifolds are tuned (think pipe organ) for various speeds so you increase the pitch by shortening them. Things like that - that's the basic, it gets to all sorts of follow-on effects. *edit* Well, Combat Theory beat me to the punch. There's actually all sorts of really interesting details with cam lobe design that mean you may or may not need stiffer valve springs! But I'm pretty sure nobody wants to hear the calculus there. mekilljoydammit fucked around with this message at 20:51 on Oct 23, 2017 |
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Oct 23, 2017 20:46
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The Door Frame posted:So that's why big, low revving engines produce hilarious amounts of torque, despite producing low HP relative to their displacement. It makes perfect sense, and I knew that HP was a function of torque and RPM, but it never clicked in my mind that that was why engines built for torque didn't like to rev Yeah. I mean if you think about the side-effect of having the valve open longer (cam duration) ... at high RPM, the air (ideally) has enough inertia to keep going in despite that the piston is moving upwards now. At low RPM though, it just means you're pumping air back out. In the end, everything is about getting air in the cylinder, keeping it there, burning it efficiently, and getting the exhaust out. All the optimizations get to about what RPM it does those things well. Also loving LOL at electric cars... electric cars are easy as long as you're willing to put up with lovely ones and ignore where the electricity comes from.
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Oct 23, 2017 21:55
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Combat Theory posted:
Oooh, shaker rig! That's coooooooool. I'm in the engine development side - small engine maker but automotive stuff recreationally. InitialDave posted:Ahaha, no, not displacement. That would be potentially sensible. Bore. It was a theory for a while that piston speed was a hard limit, so it was considered that the only displacement variable that mattered for power was bore. Funny reprecussions like that.
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Oct 23, 2017 23:15
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DogonCrook posted:So on the torque thing my problem is i have a 72 318 with real low compression. With new heads intake exhaust manifolds i could easily get 250 to 300hp but then id have like 500 to 600lbft of torque and im trying to stay mostly stock because its just a cruiser but anything i add to hp side is just gonna poo poo out gobs of torque. I know the real answer is a 340 or 360 swap but its a survivor car and i cant bring myself to do it. Im gonna see what can be done with a tuned exhaust and cam but i was wondering if there is anything i can do geometry wise to effect that ratio. Its very airflow restricted so adding better flow is a must but then all im doing is uncorking a shitload more torque. It hits at like 1,000 rpm too so its pretty drat hard to get a fast shot of fuel in there to handle it. If anything funky at all is going on in the carb or it isnt perfect itll starve for a sec, not enough to missfire but you can feel the hiccup if you stab the throttle. You're probably not going to be literally at 500ft/lbs of torque on a 318 because that's tricky - a lot of compression and good efficiency. The more cam you throw in the more it's going to shift the powerband to high RPM in short but also the more lumpy the idle and the less anything operating on vacuum works.
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Oct 23, 2017 23:51
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Sure, but you're going to reach a limit to how much torque you can make at a given displacement. Put it this way, 500ft/lbs of torque is a higher BSFC (torque per displacement, a measure of combustion efficiency) than NASCAR Cup engines, which are some of the most highly developed naturally aspirated pushrod engines in the world - NHRA Pro Stock eclipses them but they only have to do so for a few seconds at a time. In stock form the 318 doesn't breathe well but has a small cam... so yeah it's running out of breath at high RPM but it's doing well at low RPM. More compression and everything else will pick the torque up some yes, but you're not going to double it, just make it at higher RPM.
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Oct 24, 2017 00:05
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I don't claim to know my way around standard domestic 4-barrels so I won't take a guess about tuning the things. Maybe I've been playing Automation a lot lately but it's not unrealistic to think about most of the basic variables as kind of tradeoffs. More cam duration starts shifting the torque peak (RPM it hits) upwards in the powerband but sometimes costs you magnitude of what the peak torque you're getting - head ports can be the same way, ignoring stuff where it's just plain better design. Single plane manifolds end up having more plenum volume and shorter runners so (usually) lean towards shifting torque peak higher than dual plane manifolds. Compression affects BMEP - all else being equal increasing compression will increase torque per displacement, up to the point where the engine is detonating.
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Oct 24, 2017 01:51
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SNiPER_Magnum posted:Can you explain this? Because I've always heard of BMEP being torque per displacement, and BSFC being completely independent of displacement. Lol whoops, that was a brain fart on my part, good catch.
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Oct 24, 2017 05:36
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`Nemesis posted:I’m just glad no one sperged out and posted the bullshit about that the car was super rusted or didn’t have a drive train, both of which are false. I worked at a crash test facility for a while and we'd get abandoned cars to run the side impact sled into for calibration. Ha ha ha ha ha holy poo poo does the rust from those suckers go everywhere
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Oct 27, 2017 14:44
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A lot of the crash testing standards are designed to simulate specific scenarios. The side impact test is designed to simulate someone pulling away from a stop light getting hit by someone running a red light in a city.
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Nov 1, 2017 20:26
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