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CarForumPoster posted:If you've ever rolled down your rear windows and heard a pulsing sound, its called a Helmholtz resonance and heres a bit of info about it: The resonators that make the engine intake quiet use this effect too. I always remove the intake resonator that's outside the filter box because I am a manchild and I like the noise. Some vehicles have another that's between the MAF and the throttle body, you should leave that one.
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Dec 18, 2014 08:55
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Fucknag posted:If the engine/whatever it's driving are accelerating, there's a net force (torque in this case) being exerted; the engine is acting to accelerate the powertrain faster than various drag forces are acting to slow it down. If you're running at constant speed, yeah, power output matches load, but at wide open throttle there's a net torque on the output shaft, which is rotating; nonzero torque net * nonzero rotational speed = nonzero net horsepower.  You're putting the cart before the horse, dude. I think? you're saying that while accelerating the power the engine is producing outstrips the demand from resistances, which is true. What you're leaving out is that the balance still counts as load and is used to accelerate the vehicle. Nature ALWAYS balances her books. My credentials are that I'm a marine engineer who has worked on cruise ships for the last four years, dealing with very large engines (800kW a cylinder). I've made a few posts in the Awesome AI poo poo thread but it may be better for me to consolidate them here, that's not really the right thread for it. LloydDobler posted:Back to torque: My first day of statics class, the teacher (who was old, crusty, brilliant and hilarious) yelled out TORQUE IS THE FORCE TIMES THE PERPENDICULAR DISTANCE FROM THE POINT TO THE LINE OF ACTION. Then he made us repeat it like 25 times in unison. 24 years later and I've never forgotten it. Repeat it over and over and you will always remember it too. This owns. My older brother (also a marine engineer) told me about one of his classes where they were discussing the phenomenon of 'droop' as applied to governors. The teacher had one of the students walk back and forth in front of the class, then jumped on his back when he passed. Naturally he staggered, and the teacher said 'see, this is what happens when you apply a large, unexpected load to a running generator.'
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Dec 18, 2014 10:04
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Vanagoon posted:The resonators that make the engine intake quiet use this effect too. I didnt know that, good to know.
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Dec 18, 2014 10:19
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On that note....http://www.brighthubengineering.com/machine-design/84316-how-intake-resonators-improve-volumetric-efficiency/ Some one needs to do a big effort post on inertial charging. It'll be a good excuse to post old SHO intakes.
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Dec 25, 2014 07:50
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Vanagoon posted:The resonators that make the engine intake quiet use this effect too. Just to expand on this post a bit more, Mazda has some fairly interesting patents (1,2) which include a dyno graph that show the effects of the resonators on the engine performance. I am guessing Mazda did not do a great job with writing their patents, as Porsche has a patent for incorporating one into the intake system in order to smooth out the airflow through a air flow sensor. I did not really look at the claims on any of the patents I linked though, so hopefully they are the right ones.
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Dec 26, 2014 04:45
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Not sure how SA feels about TTAC but: Saturation Dive: Ford 10 Speed Transmission Power Flow http://www.thetruthaboutcars.com/2014/12/saturation-dive-ford-10-speed-transmission-power-flow/ Aaaahhh! 10 speeds worth of Automatic Transmission Witchcraft
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Dec 26, 2014 13:29
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Vanagoon posted:Not sure how SA feels about TTAC but: http://partsmanuals.org/spicerservicemanuals/Spicer-HD-14-&-20-Speed-Service-Manual.pdf
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Dec 26, 2014 16:50
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Over the next few days I'm going to be grinding away at a few engineering projects. I think it'd be fun to share the process for those that don't know about it and have people with more experience poke holes at it First one is just some simple brake caliper adapters
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Jan 15, 2015 23:28
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Given that you used the word simple, I am expecting about 11 pages of content.
torpedan fucked around with this message at 23:45 on Jan 15, 2015 |
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Jan 15, 2015 23:42
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I might get run out of here for this because the narration is in Japanese and I can't find it in English, but god this has some beautifully done engine animations in it. Boschua! https://www.youtube.com/watch?v=8Cak5r1l31A Edit: here it is in English. https://www.youtube.com/watch?v=LjJSbHxIvnM I'm leaving the original because I'm a nerd. Vanagoon fucked around with this message at 16:30 on Jan 17, 2015 |
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Jan 17, 2015 16:18
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I've been really busy but I'm going to get around to that post this weekend, I swear
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Feb 7, 2015 07:01
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~Designing Some Brake Caliper Adapters~ e30s have pretty small brakes. I decided I wanted to upgrade mine before I got it back on the road again. This is a small project, so you won't see an extremely involved design process I wanted a brake upgrade for my e30 that would have good brake balance, would be inexpensive in parts and consumables, and have a large selection of brake pad compounds readily available. It would be nice to lose weight in the process, but since I wanted to minimize cost I shelved weight as a big consideration. Wilwood calipers and 2 piece rotors with aluminum hats would be the next stage, and that setup should handle the weight constraint just fine. I picked e36 M3 brakes because they have a similar brake distribution, relatively cheap pads and rotors, and were easily accessible. I think I snagged the f+r calipers and a set of lovely rotors for mockup for like $300 total. Running e36 M3 rotors required 5 lug hubs, but I had found a cheap 5 lug solution. I had wanted 5 lug regardless for wheel options. The front setup used sleeves that pressed on the spindles to allow e36 front hubs to be used. As it turns out, Z4 rear hubs will press into e30 trailing arms with no modifications! The front gets a increase in offset by 12mm from the sleeves, and the rears see +2.5mm from the Z4 hubs. This will make a spacer needed in the rear, but that will come much later. The next step in this process was to remove the stock e30 hubs and do a LOT of measuring. I wanted to be sure this idea was viable before I reached the point of no return and pressed the hubs on, so I mocked up both the front and rear assemblies in Solidworks. Fronts were easy.    Rears were not.  Front:  Rear:   The next step is to see of course how the gently caress you can get the calipers to bolt on.   You can see there is some interference between the stock mounting lugs and the e36 M3 front caliper carrier. This is kind of lovely - it means either making a pretty big bracket that's going to be on the wrong side of mechanical advantage or modifying the caliper carrier. It only needed a small cut, so I decided to see how it would affect the strength of the part.  You can see the cut above highlighted in blue. To examine the effects of cutting some material on the caliper carrier, I did some basic math to find out what kind of loading the carrier bracket would see. For a very basic analysis - an e30 on hot slicks could see deceleration under braking over 1G. I chose 1.3G as a reasonable estimate of braking force for an e30 with no aero aid braking on hot slicks. Force = Mass x Acceleration. For an e30 with a driver, 3000lbs is a reasonable estimate. That's 1360kg. To decelerate at 1.3G, a total force of roughly 17000N would be required. Under braking, weight transfer loads the front tires considerably more than the rear. A 70-30 weight distribution is a reasonable estimate. The force decelerating the car ultimately comes from the interaction between the tires and the ground. Maximum braking force would be achieved right before the tire starts skidding - when the force between the tire and the ground exceeds the coefficient of static friction. For a simple scenario - in order to decelerate at 1.3G you would need to have a coefficient of static friction between the tires and the ground of 1.3. The sum of the forces acting on the vehicle in this simple scenario are the friction forces at each tire, and for the car to decelerate at 1.3G, the total frictional force would have to equal the earlier calculated value of ~17000N. F= ma = The sum of the frictional forces on the tires = m*g*mu where mu is the coefficient of static friction. To find the load at one of the front wheels, you apply the weight distribution of 70-30 and divide by two since there are two wheels with the force evenly distributed between them. The total load at the tire's outer surface is roughly 6000N at each front tire. That's the frictional force at the outer edge of the tire. We still need to find the reaction force at the caliper itself. The torque exerted on the wheel by this frictional force between the road and the tire must be the same as the torque exerted by the brake pads on the rotor. Since the rotor is much farther inboard than the edge of the tire, the reaction force on the caliper would need to be considerably higher than the force on the outer edge of the tire to generate the same torque. Using the diameter of the tire+wheel in question along with the distance to the center of the brake pad from the center of the wheel hub, we can calculate the net force on the caliper to produce enough torque on the wheel to slow the car at 1.3G - roughly 7600N. This force is distributed on the caliper where the brake pads contact the carrier. Solidworks has a pretty handy simulation component, and you can find out what this load will do to the modified caliper carrier pretty easily.  The distribution of stress in the part is color coded. You can see that for the most part, the stress on the carrier does not exceed 200MPA, though the yield strength of the material is much higher.  However, the above picture shows an area of stress concentration, where the stress in the part is at high enough levels to cause concern. However, this is mostly due to the constraints in the simulation - the mounting lugs here are fixed, and that can produce high stresses that the part won't actually see. Do note that you can't always disregard stress concentrations like this - if they weren't on the fixed geometry and were instead located somewhere else on the part, it would be cause for alarm. In a static part that doesn't see repeated loading often, some stress concentration is not a huge concern - as the material yields locally the stress will redistribute to stronger areas of the part. However, for a part (like a brake caliper!) that sees repeated, dynamic loads, stress concentrations can easily form cracks in the material. We are not really interested in the stress distribution of the part as a whole though - what we are most interested in is if the modification to the carrier has had a meaningful effect on the stress in the part. The cuts that were made in the carrier are far from the primary stress concentrations in the part and see very little loading, so we can see that this is a safe modification. The next part is designing the bracket itself, and going through the same stress analysis to determine its strength and safety. Here are preliminary designs for the front and rear caliper brackets respectively.   Since I don't have access to 3d scanning accurate enough for this scale, or a coordinate measuring machine, all measurements were done using some calipers and a straight edge. As such there is a LOT of room for error. I decided to validate my model by 3d printing some test brackets. It already saved my rear end once since I fudged a hole center to center distance on the front spindle.    The next steps are to 3d print the second iteration of the front bracket and the first iteration of the rear bracket to make sure I didn't fudge any other dimensions and the caliper is placed properly on the rotor. Once that's done, both brackets are going to need a couple of passes to both make sure they are easy to machine on a manual turret mill with the tools I have available to me on campus, are time efficient for production, and are strong enough and safe enough for the application. Party Alarm fucked around with this message at 02:43 on Feb 16, 2015 |
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Feb 16, 2015 02:37
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Party Alarm posted:~Designing Some Brake Caliper Adapters~ Nice work! You almost have me convinced I need a 3d printer, but I am trying really hard to not add another thing to fiddle with.
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Feb 16, 2015 04:15
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Oh hey look http://www.ebay.com/itm/231301357105?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT $320 e: Oh wow nylon and other high strength / neat materials http://www.taulman3d.com/news.html
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Feb 16, 2015 04:18
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ZincBoy posted:Nice work! You almost have me convinced I need a 3d printer, but I am trying really hard to not add another thing to fiddle with. You can also just use one of the lower in 3-D printing services too. When it comes to design work, it can really pay off to have something printed. Desktop printers can be pretty large time sinks.
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Feb 16, 2015 04:26
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BTW if anyone in Phoenix needs something printed, I'm pretty sure my printer is up to it and you can shoot me the stl.
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Feb 16, 2015 04:34
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I ordered that printer I linked, should get it at the end of the month. Gonna use it to print out the intake runners for the ITB setup I'm making for the e30. That's a whole 'nother post though 
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Feb 16, 2015 04:37
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I keep putting off buying one. I have a TAZ 4 at work I can print on if I really want something so that kinda cuts the legs off of buying my own.
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Feb 16, 2015 04:52
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Party Alarm posted:I ordered that printer I linked, should get it at the end of the month. Gonna use it to print out the intake runners for the ITB setup I'm making for the e30. That's a whole 'nother post though I'm dealing with FolgerTech right now. You should cancel your purchase, seriously.
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Feb 16, 2015 07:21
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If you need anything cmm'd let me know, I have access to faro arms and I can output any build info to a dxf or w/e file format works
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Feb 16, 2015 07:52
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Party Alarm posted:magic happening This is awesome and I love you for posting it, but did you take into account the fact that the brake caliper mounting bracket isn't coplanar with the brake rotor, which will result in that bracket seeing some torsion perpendicular to the rotational axis of the wheel? i.e. one caliper mounting ear will be pushed inward and the outer will be pulled outward. I've seen a few people do brake adaptation projects without taking that into account.
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Feb 16, 2015 17:54
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I don't remember if I saw the link on here initially or not, but EngineeringExplained did a video about the Volkswagen DSG: https://www.youtube.com/watch?v=mj1Vk7SE-TI I spent the past 5 years of ownership trying to explain to my dad that my car does not have a torque converter and isn't like a traditional automatic and he just either didn't get it or didn't believe me until I sent him the link to this video.
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Feb 16, 2015 19:45
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kastein posted:This is awesome and I love you for posting it, but did you take into account the fact that the brake caliper mounting bracket isn't coplanar with the brake rotor, which will result in that bracket seeing some torsion perpendicular to the rotational axis of the wheel? i.e. one caliper mounting ear will be pushed inward and the outer will be pulled outward. Wouldn't hurt to do modal analysis either.
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Feb 16, 2015 20:08
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insta posted:I'm dealing with FolgerTech right now. You should cancel your purchase, seriously. What happened?
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Feb 17, 2015 04:57
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Their stepper motors tend to be of shoddy quality (remember to change the driving current in the firmware, the instructions are for higher-torque motors and you'll overheat the ones they come with stock). That's not too bad, though. From what I've heard they work just fine but be careful. They supply the same ones SeeMeCNC supplies for their extruder, but for all of the axis. SMC uses higher-quality ones for the effector.
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Feb 17, 2015 05:04
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Geirskogul posted:Their stepper motors tend to be of shoddy quality (remember to change the driving current in the firmware, the instructions are for higher-torque motors and you'll overheat the ones they come with stock). That's not too bad, though. From what I've heard they work just fine but be careful. They supply the same ones SeeMeCNC supplies for their extruder, but for all of the axis. SMC uses higher-quality ones for the effector. We just picked up a Makerbot Replicator 5th Gen. I love it, except for the extruder jamming every other print.
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Feb 17, 2015 05:18
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CarForumPoster posted:What happened? They sent me some spectacularly lovely parts and are ignoring my support requests. I'm about to force-RMA it through eBay/PayPal.
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Feb 17, 2015 05:20
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CommieGIR posted:We just picked up a Makerbot Replicator 5th Gen. I love it, except for the extruder jamming every other print. Heh, I do have to wonder how poor their internal design and validation process is for them to have gone to production with their current design. The replicator 2X printers we have at work have the occasions jam but it's no where near as frequent and it just baffles me to think they managed to regress that significantly in such a short time.
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Feb 17, 2015 05:29
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I've never had a jam with my Rostock, with either the stock hotend or an E3D v6. I have had the nozzles clog up and have low output due to me not using a dust wipe for the first month of ownership, but I've fixed that.
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Feb 17, 2015 05:30
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torpedan posted:Heh, I do have to wonder how poor their internal design and validation process is for them to have gone to production with their current design. The replicator 2X printers we have at work have the occasions jam but it's no where near as frequent and it just baffles me to think they managed to regress that significantly in such a short time. Other than the jams and the occasional homing errors, I can't complain. But for the house, we'll probably go with a different model.
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Feb 17, 2015 05:31
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In a slightly different area that's probably of interest to AI, I build self driving cars for a living and can answer any questions from that perspective (I also have two mechanical engineering degrees and I mostly do software stuff  ) I can probably do an effortpost on the high level systems involved in what it takes to make a car drive itself at some point as well.
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Feb 17, 2015 05:45
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Geirskogul posted:I've never had a jam with my Rostock, with either the stock hotend or an E3D v6. I have had the nozzles clog up and have low output due to me not using a dust wipe for the first month of ownership, but I've fixed that. The vast majority of the jams I have with the TAZ I use are operated related or due to 3mm filament diameter issues. If I did not have a huge stack of filament I would convert it to run on 1.75mm to not have to worry about it. CommieGIR posted:Other than the jams and the occasional homing errors, I can't complain. I really like Makerbot's software approach and how simple their overall package is. It's a pretty big plus to be able to let the design team focus on making actual parts as opposed to having to tweak settings to get a part to print right. Really what I would like to do is find a way to get my bosses to sign off on a Fortus 250.
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Feb 17, 2015 06:07
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Frinkahedron posted:In a slightly different area that's probably of interest to AI, I build self driving cars for a living and can answer any questions from that perspective (I also have two mechanical engineering degrees and I mostly do software stuff What type of self driving car? Like intended for the street similar to what Google has confirmed and Apple is rumored to be doing?
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Feb 17, 2015 07:00
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SO do we have cars that can drive themselves in rain and snow now or what?
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Feb 17, 2015 07:03
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CarForumPoster posted:What type of self driving car? Like intended for the street similar to what Google has confirmed and Apple is rumored to be doing? Basically stuff evolved from these bad boys in 2007 (Google basically bought the team that came in first): https://www.youtube.com/watch?v=-xibwwNVLgg There's a lot of military work because the military doesn't have to abide by pesky traffic laws or really operate in rush hour traffic, so lots of on road and off road/cross country driving there. Commercially, lots of heavy equipment type stuff like construction and mining where there's elements of danger to a human operator. The vehicles have the ability to navigate themselves if the project calls for it or for a human to teleoperate it. On the not-autonomous side, a lot of companies/labs hire us to basically convert regular cars into giant RC controlled ones for their own controlled research and testing. Throatwarbler posted:SO do we have cars that can drive themselves in rain and snow now or what? Kinda.
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Feb 17, 2015 07:59
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CBD posted:I will assume the question is with reference to roller and ball bearings. Keep in mind unless you are really going on the outside envelope of an application, you're going to be buying the same bearing if you're running it at 50RPM or 5000 RPM (depending on the size/style of bearing of course). Your method of sealing and lubrication will almost certainly change though. People (generally a consultant or a young P.E. in design engineering) wants a specific HIGH SPEED bearing and throws a poo poo-fit when they find out there is a minimum order qty, 6+ month lead time and $RAPE$ so they settle for the catalog item which 99.99% of the time is more than appropriate anyhow. Also, it's a dirty little secret in the bearing industry, but SKF sells their steel to other bearing manufacturers.  Also, talking about plain and babbit bearings earlier, peoples minds get blown when you tell them you can still, to this day, buy wooden bearings. Typically used in material handling applications but they are still out there and have their place. I'm not a P.Eng. (although I'm married to one) but I am a Certified Bearing Specialist and have been doing this crap for going on 25 loving years now, although my stronger suit is mechanical power transmission. I would like to be stronger in fluid power (and pneumatic) as I find that interesting as hell.
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Feb 18, 2015 20:42
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I currently work in pneumatic power primarily. It's bearings we have trouble with. Finding small bearings that will be happy turning 100k RPM seems to be tough. One of our motors had to be redesigned to use a little bleed air to cool the bearing. Sadi fucked around with this message at 21:34 on Feb 18, 2015 |
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Feb 18, 2015 21:32
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How small? I have seen some pretty impressive rpm ratings with some ceramic hybrid deep groove ball but to be honest I haven't taken a hard look.
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Feb 18, 2015 23:41
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Party Alarm posted:To find the load at one of the front wheels, you apply the weight distribution of 70-30 and divide by two since there are two wheels with the force evenly distributed between them. The total load at the tire's outer surface is roughly 6000N at each front tire. This is true in straight line braking on a smooth surface where the really hard braking is most often done but there will be times where braking and turning in conjunction will load the outer wheel significantly more, also over uneven surfaces where spring compression will give the tire significantly more grip momentarily. The worst circumstance I can think of is braking too late and overshooting a turn. The car will experience hard braking with weight transferred to the outside wheel which will be loaded even more significantly as it crosses the curb. Although I don't know if the paint they use on those curbs lowers the coefficient of friction or not. Of course nobody is paying me to be an engineer so take this as you will.
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Feb 19, 2015 03:20
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slidebite posted:How small? I have seen some pretty impressive rpm ratings with some ceramic hybrid deep groove ball but to be honest I haven't taken a hard look. In the range of 5/8" OD, 1/4" ID.
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Feb 19, 2015 14:55
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