|
MRC48B posted:Some mechanical engineer tell me why you cannot just put an insulating spacer around the outer race of the bearing, or between the inner race and motor shaft. You absolutely can, you just have to make sure it’s designed for it. Micarta has a compressive strength of 100,000 psi, so it’s very strong. The entire rotating assembly on a vertical hydro generator typically hangs from a thrust bearing that is insulated by a sheet of micarta to prevent this exact problem.
|
#
?
Jul 7, 2019 00:09
|
|
|
|
| # ? May 12, 2024 02:48 |
|
|
I hope that was a dedicated pulling truck.
|
|
#
?
Jul 7, 2019 20:57
|
|
|
thebigcow posted:I hope that was a dedicated pulling truck. most trucks are dedicated pulling trucks.
|
|
#
?
Jul 7, 2019 21:48
|
|
|
With cylinders that huge, I always wondered if you could have a turbo hooked onto the exhaust for each one, or if it would be more efficient to do more traditional turbo set ups It would be a god damned mess to sort the piping, but man, it would be cool
|
|
#
?
Jul 7, 2019 22:48
|
|
|
Not really because then there are discrete exhaust gas pulses going into each turbine vs a smoother, more continuous flow when they are all combined into 1-2 collectors. Plus, generally I want to say that one single larger turbo is more efficient than two smaller ones at the same total airflow and pressure ratio. E- multiple, smaller turbos tends to be better for response and low-mid range power but that's not what these things are going for. jamal fucked around with this message at 23:06 on Jul 7, 2019 |
|
#
?
Jul 7, 2019 22:59
|
|
|
Turn it into a huge mess. Exhaust - > turbo - > intercooler to act as a charge cooler and boost storage, like in single cylinder turbo applications, straight into each cylinders own intake. It'd be tall and need a lot of supports, but each cylinder would turbo itself and be relatively easy to pop off the whole assembly cylinder by cylinder to fix whatever breaks.
|
|
#
?
Jul 7, 2019 23:01
|
|
|
The Door Frame posted:With cylinders that huge, I always wondered if you could have a turbo hooked onto the exhaust for each one, or if it would be more efficient to do more traditional turbo set ups https://www.aliexpress.com/item/32973154851.html If ITBs are good, ITBs on ITSCs must be the best.
|
|
#
?
Jul 7, 2019 23:04
|
|
|
charliemonster42 posted:You absolutely can, you just have to make sure it’s designed for it. Micarta has a compressive strength of 100,000 psi, so it’s very strong. The entire rotating assembly on a vertical hydro generator typically hangs from a thrust bearing that is insulated by a sheet of micarta to prevent this exact problem. That is what we do on our large generators (875 Mw) You can get stray currents from several places on a big generator. The magnetic field of the rotor and stator are not always perfectly aligned with the center of the shaft. There are also static charges that occur in large steam turbines that can result in large DC voltages on the shaft. So we have the bearing on the end of the generator mounted on a huge Micarta block and then use insulating materials on all the oil piping so that that end of the generator is floating. The rest of the bearings on the set are normal and there are a set of copper brushes that keep the shaft voltage low enough to not cause problems in the bearings. Our large frame motors are built in a similar fashion and we regularly check that the inuslated bearing is in fact insulated.
|
|
#
?
Jul 8, 2019 01:50
|
|
|
Powershift posted:
I will have you know I buy Mitsubishis and Chrysler products while not enjoying Taco Bell. Please do not lump me and my peers in with the people who like Taco Bell.
|
|
#
?
Jul 8, 2019 02:24
|
|
|
Powershift posted:most trucks are dedicated pulling trucks. Bravo.
|
|
#
?
Jul 8, 2019 03:48
|
|
|
helno posted:That is what we do on our large generators (875 Mw) Static buildup and discharge is a huge problem on any large rotating machinery with plain bearings, it can buildup to thousands of volts and arc across the oil film, causing small pits in the bearing surface, until that surface is no longer smooth enough to support the oil film, then you wipe your bearing. Fortunately it is a well solved problem with shaft grounding and whatnot, but it's kinda cool MRC48B posted:Some mechanical engineer tell me why you cannot just put an insulating spacer around the outer race of the bearing, or between the inner race and motor shaft. To elaborate on what others have said, it's doable, but costly, your stator-to-rotor clearances are measured in thousands of an inch (or other unit), and it's very difficult to find something strong, rigid, and insulating all in one, definitely doable for a 20MW turbine with a 50 year service life, but not so much on your 10 grand motor, and proper grounding is an easier and cheaper solution that obviates coming up with a different one. Honestly you just don't see radical bearing wear like that in most small motor applications, so much so I'm really glad Slidebite posted those photos since that's borderline porn for me. Also to be clear, the damage caused in his photos is full on current flow, like measured in amps, not microamps like static, I work with VFDs a lot, and don't see that failure mode, I would be fascinated to see if this becomes more of an issue, with VFDs being the Second Coming in the land of making things rotate with electricity.
|
|
#
?
Jul 8, 2019 04:29
|
|
|
I agree with everything that's been said. It's possible to insulate a low voltage/HP motor, but it's really just cost/benefit. These things are basically a commodity. While quality certainly has its place, a lot of it still comes down to "If this 5HP is $25 cheaper than this other 5HP motor, I'll go with the cheap one  "Regardless if the $25+ motor is just a better all around product. And to be fair, this really isn't super common and fairly easily rectified after its identified. Of course, it's already been through a failure at that point. e: Here is a better pic of the fluting 
slidebite fucked around with this message at 05:01 on Jul 8, 2019 |
|
#
?
Jul 8, 2019 04:56
|
|
|
All of the motors i work with are below 100 horses, or vfd rated or both, so that explains why i dont really run into this problem much. Neat to see that failure mode in the wild though.
|
|
#
?
Jul 8, 2019 05:06
|
|
|
slidebite posted:I agree with everything that's been said. It's possible to insulate a low voltage/HP motor, but it's really just cost/benefit. These things are basically a commodity. While quality certainly has its place, a lot of it still comes down to "If this 5HP is $25 cheaper than this other 5HP motor, I'll go with the cheap one I really hope you can save that piece and keep it on a shelf somewhere.
|
|
#
?
Jul 8, 2019 05:18
|
|
|
MRC48B posted:All of the motors i work with are below 100 horses, or vfd rated or both, so that explains why i dont really run into this problem much. Neat to see that failure mode in the wild though. TBH, other than specialty or true commodity "farmer" motors, VFD rated is basically the norm here. Midjack posted:I really hope you can save that piece and keep it on a shelf somewhere. Its on my desk, about 6" from where I took that photo. The client retained the other half for his collection 
|
|
#
?
Jul 8, 2019 06:01
|
|
|
I want to see a megawatt engine with jewel bearings.
|
|
#
?
Jul 8, 2019 07:57
|
|
|
My coworker tried cutting some DIN rail with a pair of small diagonal wire cutters. I told him he should maybe ask if he can borrow a hack saw next time. On a related note, who makes a really nice small wire cutter that I can replace this one with?
|
|
#
?
Jul 8, 2019 18:38
|
|
|
Really nice? Swanstrom, knipex, etc. Acceptable and very cheap? Hakko. This is assuming micro electronics usage.
|
|
#
?
Jul 8, 2019 18:48
|
|
|
Any of the $10-20 flush cutters on Amazon are fine. And punch your coworker for ruining your tools like that (I see those nicks in the remaining blade too!), and don't let anyone touch the new ones once they arrive.
|
|
#
?
Jul 8, 2019 19:16
|
|
|
Get Hakkos.
|
|
#
?
Jul 8, 2019 20:31
|
|
|
To be fair, I'm reasonably sure the company bought these cutters, not me personally. To also be fair, I'm probably responsible for some of the nicks in the blades. I'm using this as an excuse to order two pairs of hakkos and probably to justify a large pair of knipex while I'm at it.
|
|
#
?
Jul 8, 2019 20:57
|
|
|
The CHP series are an amazing value. They're not the quality of the high dollar cutters, but you get 75% of the performance at 10% of the price. Kinda like the HF 44" toolbox vs SnapOn.
|
|
#
?
Jul 8, 2019 20:59
|
|
|
I wasn’t familiar with DIN rail and was thinking “ok, so really crappy wirectutters cant handle some kind of single row header???”. Then I googled it and was enlightened. Who tries to cut that stuff with that tool? Wrong thread though, the horrible failure wasn’t mechanical
|
|
#
?
Jul 8, 2019 21:08
|
|
|
Going to guess seat heater safety failure, but Taco Bell comments are also relevant. Powershift posted:https://www.aliexpress.com/item/32973154851.html I kind of hate you for letting me know these exist <eyeballs lawnmower>.
|
|
#
?
Jul 8, 2019 23:23
|
|
|
Darchangel posted:Going to guess seat heater safety failure, but Taco Bell comments are also relevant. The good news is that my rear end is no longer cold.
|
|
#
?
Jul 9, 2019 00:36
|
|
|
This is pretty mild and uninteresting for this thread, but my friend asked me to help him figure out why the rear end of his brother's car feels like it's not planted on the ground at all. I think I found the problem? My favorite part is the damage at the top of the trunk. Paradoxish fucked around with this message at 02:43 on Jul 9, 2019 |
|
#
?
Jul 9, 2019 02:41
|
|
|
That's an interesting failure.
|
|
#
?
Jul 9, 2019 14:49
|
|
C-Bangin' it 
|
Paradoxish posted:This is pretty mild and uninteresting for this thread, but my friend asked me to help him figure out why the rear end of his brother's car feels like it's not planted on the ground at all. https://www.youtube.com/watch?v=-h5j_mAEEdw
|
|
#
?
Jul 9, 2019 15:48
|
|
|
What kind of car is that? That’s one of the more amusing failures I’ve seen. 
|
|
#
?
Jul 9, 2019 17:02
|
|
|
I'm curious where the car spent its time.
|
|
#
?
Jul 9, 2019 17:06
|
|
|
Saw this one on my way home for lunch and snapped this from the other side. It broke in the left lane and left a scar as the truck drug the belly across the road to the shoulder. What causes a trailer to snap like this? 
|
|
#
?
Jul 9, 2019 20:09
|
|
|
Overloading and/or rust, probably.
|
|
#
?
Jul 9, 2019 20:29
|
|
|
Whoops https://twitter.com/abc/status/1148729178310791168
|
|
#
?
Jul 10, 2019 02:51
|
|
|
Man that probably fell out when they pitched down to land, too. I hope it didn't hit anyone.
|
|
#
?
Jul 10, 2019 03:08
|
|
|
Darchangel posted:Overloading and/or rust, probably. That'd wake you up.
|
|
#
?
Jul 10, 2019 03:08
|
|
|
Seat Safety Switch posted:Man that probably fell out when they pitched down to land, too. I hope it didn't hit anyone. I think the plane is going to fast for it to fall out.
|
|
#
?
Jul 10, 2019 03:10
|
|
|
MrYenko posted:What kind of car is that? 2009 (I think) Aveo. Driven pretty regularly over the roads in Waterbury, CT by someone who is far from being a careful or, uh, good driver so I'm sure that helped it along.
|
|
#
?
Jul 10, 2019 04:00
|
|
|
The rust is strong in that part of the country, right after they salt the roads it turns 50 and raining to really help speed the corrosion process and evenly coat all metal surfaces, I can't imagine Daewoos have good rust proofing, or that the owner of an Aveo would ever care enough to regularly wash their car.
|
|
#
?
Jul 10, 2019 04:48
|
|
|
Elviscat posted:The rust is strong in that part of the country, right after they salt the roads it turns 50 and raining to really help speed the corrosion process and evenly coat all metal surfaces, I can't imagine Daewoos have good rust proofing, or that the owner of an Aveo would ever care enough to regularly wash their car. People wash cars even if they're not selling them?
|
|
#
?
Jul 10, 2019 05:17
|
|
|
|
| # ? May 12, 2024 02:48 |
|
|
The Door Frame posted:People wash cars even if they're not selling them? Well yeah. Sometimes you gotta hose the mud and poo poo off the underside, otherwise it falls in your eyes and mouth while you're working on them.
|
|
#
?
Jul 10, 2019 07:04
|
|
