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They use those kinds of tractor pulled mowers at the tallgrass prairie preserve I work at, usually in areas where they can't do a controlled burn for some reason (too close to structures or a cornfield or something). The ease with which they plow through shoulder height growth is pretty cool, and if you walk the field after they're done it's endless half-inch thick twigs that got shredded down to about four inches tall. They do about 200 acres in a day.
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Apr 28, 2020 15:31
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this is my favorite mower https://www.youtube.com/watch?v=I3D4FN5cdZk
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Apr 28, 2020 15:57
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StormDrain posted:Could you imagine trying to wear a flip flop if it was permanently split like that? He'd need a custom Tabi sock, I'll tell you what.
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Apr 28, 2020 15:59
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xzzy posted:They use those kinds of tractor pulled mowers at the tallgrass prairie preserve I work at, usually in areas where they can't do a controlled burn for some reason (too close to structures or a cornfield or something). The ease with which they plow through shoulder height growth is pretty cool, and if you walk the field after they're done it's endless half-inch thick twigs that got shredded down to about four inches tall. They do about 200 acres in a day. Ever had any boar go through them?
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Apr 28, 2020 16:03
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kastein posted:Lost fingat at hostpital post mote later? Same. A few close ones (like many things. I've been incredibly lucky at times) but no damage so far. I wear shoes to mow, but not usually steel toes. Reconsidering that. Imperador do Brasil posted:All I’m saying is I work in trauma surgery and you guys are lucky to have all your poo poo relatively intact... Don't I know it. Just thinking about stuff like that makes me cringe in sympathy. Sagebrush posted:this is my favorite mower ....  Mother of God.
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Apr 28, 2020 16:49
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LifeSunDeath posted:Ever had any boar go through them? No boars up here but I can imagine a muskrat or two have had a really lovely day.
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Apr 28, 2020 16:55
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Sagebrush posted:this is my favorite mower Holy gently caress. Talk about spinning death. The noise that thing makes is insane.
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Apr 28, 2020 17:01
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Sagebrush posted:this is my favorite mower
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Apr 28, 2020 17:01
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xzzy posted:They use those kinds of tractor pulled mowers at the tallgrass prairie preserve I work at, usually in areas where they can't do a controlled burn for some reason (too close to structures or a cornfield or something). The ease with which they plow through shoulder height growth is pretty cool, and if you walk the field after they're done it's endless half-inch thick twigs that got shredded down to about four inches tall. They do about 200 acres in a day. Nahh, for that sort of job you want goats. Lots of goats. Not as fast maybe, but a lower carbon footprint and less capital intensive. The campus where I work is very hilly, so in the lead up to grass fire season we bring in goats to clear the grass. They get it right down to bare dirt, which grows back. They're also quieter and cuter than mechanical mowers. http://www.rentaruminant.com/goats-for-land-clearing.html
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Apr 28, 2020 17:23
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Sagebrush posted:this is my favorite mower Props are so old school! Why not get with the times and use a turbine engine like the rest of us?
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Apr 28, 2020 17:29
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It's a prairie preserve and goats aren't native to Illinois.  They prefer to manage with fire because everything native to the region is adapted to recover after a fire, but sometimes you can't burn a spot so the lawn mowers gotta suffice. They do have a bison herd on site that I think would be cool to let them graze the fields, but for some reason it's not done.
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Apr 28, 2020 17:34
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I wish I had taken some pics of the carnage our Bobcat mower attachment has been through.LifeSunDeath posted:Get one of these badboys, no grass is safe Holy crap, I worked on the engineering team that designed the previous version of that!
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Apr 29, 2020 01:36
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Unfortunately I have no pictures, but we had someone make a very impressive (and expensive) noise at work by backing a running turboprop into a ladder. Apparently the ladder was under the wing for maintenance, and a ground crew was going to reposition the airplane by taxiing it, and failed to see the ladder before they pushed the airplane back with an engine started. At idle, the propeller isn't spinning terribly fast (maybe 400RPM), but it's 13.5' in diameter, so the blades still have a lot of energy behind them. When the prop hit the ladder, it drat near launched bits of the ladder into orbit (since the blades move upwards on that side), accompanied by large chunks of a propeller blade that had shattered when it whacked into the ladder. The propeller was a total loss, but since the propeller gearbox isn't directly attached to the power section of the engine, they just had to swap the gearbox instead of pulling a $1.3 million engine for overhaul.
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Apr 29, 2020 03:31
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Joe Mama posted:I wish I had taken some pics of the carnage our Bobcat mower attachment has been through. Slugworth fucked around with this message at 03:57 on Apr 29, 2020 |
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Apr 29, 2020 03:54
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Sagebrush posted:this is my favorite mower Every time I see this video I wonder about the tip speed of that blade. It's got to be pushing like, high caliber handgun velocity right? It sounds insane. Speaking of which: azflyboy posted:When the prop hit the ladder, it drat near launched bits of the ladder into orbit (since the blades move upwards on that side), accompanied by large chunks of a propeller blade that had shattered when it whacked into the ladder. 13.5 feet at 400 RPM is just under 200mph of tip speed which is on par with a commercial mower.
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Apr 29, 2020 04:39
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Sagebrush posted:this is my favorite mower It even sounds demonic.
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Apr 29, 2020 06:31
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Previa_fun posted:Every time I see this video I wonder about the tip speed of that blade. It's got to be pushing like, high caliber handgun velocity right? It sounds insane. I loaded the video into Audacity and counted the peaks in the sound, assuming that each one represents a blade passing the camera:  I counted 100 peaks in 4.81 seconds, which equals 1247 peaks in 60 seconds or 624 RPM since there are two blades. I estimate that the blade has a radius of 8 feet, meaning the blade tip sweeps out an arc ~50 feet in circumference 624 times per minute or 37,440 times per hour. That gives us a tip speed of 354 miles per hour.
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Apr 29, 2020 07:00
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Sagebrush posted:I loaded the video into Audacity and counted the peaks in the sound, assuming that each one represents a blade passing the camera: How does this thing not fly?
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Apr 29, 2020 07:18
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It's not on a treadmill.
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Apr 29, 2020 07:22
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GnarlyCharlie4u posted:How does this thing not fly? It weighs a lot and the blades aren’t shaped to provide significant force perpendicular to rotation.
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Apr 29, 2020 07:23
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Sagebrush posted:I loaded the video into Audacity and counted the peaks in the sound, assuming that each one represents a blade passing the camera: GnarlyCharlie4u posted:How does this thing not fly?
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Apr 29, 2020 12:57
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azflyboy posted:The propeller was a total loss, but since the propeller gearbox isn't directly attached to the power section of the engine, they just had to swap the gearbox instead of pulling a $1.3 million engine for overhaul. By "power section" do you mean the gas generator section? My layman's understanding is that the power turbine is what powers the propeller gearbox. I'm not criticizing your terminology, merely trying to wrap my head around it. You actually work on the drat things so please forgive any ignorance or lack of understanding on my part, I merely watch a lot of AgentJayZ 
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Apr 29, 2020 14:01
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Power turbines, the part attached to the transmission and prop, have their own shaft not connected to the rest of the jet engine, or as it's properly known, gas generator. So a sudden stop of the power turbine won't ruin the gas generator. The purple bit is the power turbine. Green is the gas generator. um excuse me fucked around with this message at 14:26 on Apr 29, 2020 |
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Apr 29, 2020 14:23
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um excuse me posted:Power turbines, the part attached to the transmission and prop, have their own shaft not connected to the rest of the jet engine, or as it's properly known, gas generator. So a sudden stop of the power turbine won't ruin the gas generator.  just step a little closer, it's perfectly safe.
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Apr 29, 2020 14:37
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Beach Bum posted:By "power section" do you mean the gas generator section? My layman's understanding is that the power turbine is what powers the propeller gearbox. I'm not criticizing your terminology, merely trying to wrap my head around it. You actually work on the drat things so please forgive any ignorance or lack of understanding on my part, I merely watch a lot of AgentJayZ It basically works like a torque converter between the turbine and the gearbox. There's no physical connection, think of one fan blowing on another fan.
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Apr 29, 2020 14:37
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chrisgt posted:one fan blowing on another fan. Trekkie convention all over again
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Apr 29, 2020 14:48
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chrisgt posted:It basically works like a torque converter between the turbine and the gearbox. There's no physical connection, think of one fan blowing on another fan. Just wanted to say honestly a thank you for the simple explanation. Now it all makes sense. Of course raises the question in my mind, a torque converter has fluid in it and how does that compare with superheated air.
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Apr 29, 2020 15:28
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C-Bangin' it 
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Colostomy Bag posted:Just wanted to say honestly a thank you for the simple explanation. superheated air is just another, thinner, fluid.
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Apr 29, 2020 15:52
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Colostomy Bag posted:Just wanted to say honestly a thank you for the simple explanation. There's a hydraulic connection there. Like any fluid, it isn't a rigid interaction. Two halves of the converter just pass a fluid back and forth to each other using centripetal force. If one half is spinning and the other is not, the fluid is spun up by the moving half and it's momentum is transferred to the stationary half when the working fluid gets passed onto it, generating torque on the output. In a very basic way it's still just one propeller pushing a fluid onto another.
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Apr 29, 2020 16:07
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Beach Bum posted:By "power section" do you mean the gas generator section? My layman's understanding is that the power turbine is what powers the propeller gearbox. I'm not criticizing your terminology, merely trying to wrap my head around it. You actually work on the drat things so please forgive any ignorance or lack of understanding on my part, I merely watch a lot of AgentJayZ Yeah, I meant to write "gas generator, but had a complete brain fart and typed something else. My bad.
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Apr 29, 2020 16:18
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um excuse me posted:There's a hydraulic connection there. Like any fluid, it isn't a rigid interaction. Two halves of the converter just pass a fluid back and forth to each other using centripetal force. If one half is spinning and the other is not, the fluid is spun up by the moving half and it's momentum is transferred to the stationary half when the working fluid gets passed onto it, generating torque on the output. In a very basic way it's still just one propeller pushing a fluid onto another. So if the power turbine is stopped suddenly does the resulting reduction in fluid(air) movement not still get transferred back to the compressor parts and cause them to suddenly slow due to the reduced flow? (or is this slowing just buffered enough by the air/fluid and the design of the blades on everything such that it prevents damage?)
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Apr 29, 2020 18:40
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now I'm wondering if there is a common term for air-hammer like water-hammer, or if compressibility makes that not a thing
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Apr 29, 2020 18:55
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There's a theory that a air-hammer type event was responsible for so much of Aloha 243s roof blowing off.
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Apr 29, 2020 19:05
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taqueso posted:now I'm wondering if there is a common term for air-hammer like water-hammer, or if compressibility makes that not a thing Bomb?
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Apr 29, 2020 19:18
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Tomarse posted:So if the power turbine is stopped suddenly does the resulting reduction in fluid(air) movement not still get transferred back to the compressor parts and cause them to suddenly slow due to the reduced flow? Depends how the system is designed. Bleed valves may take that surge of fluid and route it outside of the engine (this is what a wastegate literally is). However fluid dynamics isn't consistently intuitive. A stopped turbine will produce less stress on the generator than one that is spinning and driving something like a propeller due to the way that a fluid stalls on air foils. taqueso posted:now I'm wondering if there is a common term for air-hammer like water-hammer, or if compressibility makes that not a thing Surge, typically.
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Apr 29, 2020 19:48
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um excuse me posted:Surge, typically. https://youtu.be/mgp19QhrlqU
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Apr 29, 2020 20:11
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How are there no youtube videos of really big turbos barking
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Apr 29, 2020 20:18
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Tomarse posted:So if the power turbine is stopped suddenly does the resulting reduction in fluid(air) movement not still get transferred back to the compressor parts and cause them to suddenly slow due to the reduced flow? It does, but since air compresses and the engine isn't a sealed container, the compressor blades slow down (relatively) gradually, so that alone won't cause damage. However, disrupting the airflow through the compressor is a good way to set off a compressor stall or surge, and depending on how hard the engine is working at the time, the resulting spike in temperature (since airflow isn't going the right way), compressor speed (which accelerates because the stall suddenly removes a lot of load from the turbine), and vibration (due to disrupted airflow inside the engine) can easily cause serious damage if the FADEC system doesn't cut back on the fuel flow quick enough.
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Apr 29, 2020 20:22
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The time attack car i used to work on didn't have a bov. https://www.youtube.com/watch?v=_MIYc3CjY-4 so that chirp between shifts is surge. Turbo is a gen 1 gtx3582, think peak boost was 38psi and it made 747whp? The engines blew up a lot but the turbos seemed to hold up fine. To contribute to the thread this happened the next morning on the first hot lap https://www.youtube.com/watch?v=g6v76JXWlIc hmmmm  whoops  
jamal fucked around with this message at 19:33 on Apr 30, 2020 |
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Apr 29, 2020 20:41
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um excuse me posted:Power turbines, the part attached to the transmission and prop, have their own shaft not connected to the rest of the jet engine, or as it's properly known, gas generator. So a sudden stop of the power turbine won't ruin the gas generator. Well poo poo, I always assumed it was a physical connection.
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Apr 29, 2020 20:44
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