How Lawn Mower Blades Cut Grass (at 50,000 FRAMES PER SECOND) - Smarter Every Day 196
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- เผยแพร่เมื่อ 30 มิ.ย. 2018
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#lawnmower - วิทยาศาสตร์และเทคโนโลยี
At 6:03 my stepdad walked in and told me to go mow the front yard
Hey Smarter Everyday. I really Hope you will find my comment. I need ya to rewatch your Rolling. shutter video and consider how is it 4D. I made a comment but it drowned in thousands of others so I will just past IT here. I know you will get what I mean.
"SMARTER EVERY DAY, we think similar, I know you can analyse this topic well so PLEASE do:
Consider this. This is actually badly made 4D video. Assumimg that time is the forth dimension we as the 3D creatures can see only points (like frames or pictures). Like stick is a never ending road for an ant (like time for us). There is infinite amount of dots (points) on the line but only when you see all of them at the same time you can spot the line. The same thing with time. These videos show you not only where the string was at this specific second. It also shows you where it was at every other milisecond. This is an actual 4D !!!"
*Thanks for reminding him
This is no surprize though, i pooped while writing this comment and didnt sign a press release. Get real man! 1.3 million people watched this video so far. It was bound to happen to someone.
Seemed rubbish explanation, seems just brute force.
ZetPerson mmm
walks into barbershop
Destin: you know lawn mowers?
Barber: say no more
i was the 100th like.. youre welcome
I was 323rd, you're welcome
i was not 420, you're not welcome
I was the somewhere between the 76,000th and 77,000th like. And nobody cares 🤷♂️
651st like and very ambivalent
Your sound guy did an awesome job on this one!
Gordon from A Shell In The Pit Audio is amazing. Did you know you can follow him on Spotify? I'd love it if you did. My favorites are "Mountain" and "Rings in Rings in Rings"
open.spotify.com/artist/0HIiXblDOFPXxkuI35wOMx
yeah, ever since that video where he showed how the sound is made, ive appreciated the sound design a lot more in the slowmo videos :D
Great job!! My fathers old gravely walk behind had horrible air flow. 60 years old with years of brush hogging. When we straighten up the cowlings around the perimeter the cut improved tremendously.
@@gregkinney2565 glad it's not just me who noticed that
Destin: Mowers don’t cut like scissors.
Reel mowers: Am I a joke to you?
The first thing I thought of when I saw this video last night. I wonder if he is aware of this since making the video.
Haybine.
Beat me to it!!!
Obviously many people thought the same as me. The neighbor across from my parents mows his acre with 5 reel mowers he pulls behind his riding mower that is just pulling. He says it cuts sharper and straighter and from how manicured it always looks I'd have to agree. I think some golf courses use these as well.
@@johnjornod6429 Fairway and greens- Reels..cut more evenly and closer to the ground. Rough - Rotary. The reel mower blades are harder to sharpen and require more overall maintenance from what I have been told.
My barber can't even cut my hair, let alone give me physics lessons.
My barber get mad Bc idk what tapper means
I only got barber stories from my barber
Just don't let him run a lawn mower across your head and you'll be a-okay
I'd love to see how a scythe cuts grass. Does the curvature of the blade help or is it just for shape ? What's the technique etc
Not sure how the curve helps, if at all. I do know scythes need to be much sharper than a mower blade, like kitchen knife sharp. They also need to be honed very often while in use
the curve is because you kind of swing it around yourself and because your arms draw a curve the blade has to be that too
the grass is getting cut due to the slicing movement
grassynole07
Speed is the key, blade to ground speed.
Fast and consistent, it’s an inertia tool.
Of course the blade should be razor sharp, done with light strokes of a fine grade stone every 4-5 minutes of cutting time.
An impressive tool in the right hands, and the movement is all in the knees and hips.
whatthewhat11
A scythe is slicing tool, like a Katanga.
The curve is so that the scythe blade hits the grass blade at a very small angle, about 10degrees, and slices it.
The cut swathe is less wide than the scythe blade.
It is not an inertia tool: an experienced user can move the blade quite slowly.
This is quite different from the rotary mower blade, which hits the grass blade at about 90degrees and so depends on speed and inertia. The cut swathe is as wide as the blade is long.
I was taught to use a scythe by my father, who (65 years ago) used it for mowing hay, and by the gardener at the Manse who used a scythe to mow the squire’s lawn (A British lawn; grass 0.5 inches).
Don’t think it was invented for cutting lawns .
That intro was kind of “Mythbusters” Esque... I like it!!
A Glimpse Inside I think that was the point
That legendary guitar riff!
And the welded plate
Esque
Aubrey Hoes Thank you I made the change. Appreciate it
“Don’t modify your lawn mower”
Project Farm: *heavy breathing*
he even replaced engine oil with banana 🤣
Lol
@projectfarm
Yes 😂😂😂
I understand that reference
This also shows why it's important to having a sharp blade while mowing, ie; cutting the grass. Great series BTW!
I'm glad I saw this near the top. Those blades were embarrassingly dull and rock pitted.
I sharpen my blade at the beginning of the season, and then a couple times during.
Yea Destin is a smart engineer, and he has a workshop to boot, i'm surprised he didn't sharpen his blade for the video xD
Came here to see/say this... some of that grass looked sad post-cut...
10:00 pm : just one more video
3:00 am : how lawn mower cuts grass
So you have the UTC Timezone
Currently 9:57pm. I know that you've just described my night
@@pags5zonda623 currently 2:56 am est just clicked on this video, the prophecy is true.
Try turning a blue light filter on your device and turning the volume to the lowest setting you can with out making it too hard to hear.
5:01 whoa wait... 5 I thought it's 3. By, I'm going after just this one
I love how Destin can turn something as simple as how a lawnmower works into a fascinating hands on science experiment
Because IT IS a fascinating hands on science experiment!
Simple? I think its ex scythe ing!
I just wanted to comment that, things we dont even think about are amazing.
Who said it's simple? You just don't understand the complexity of the world created around you.
@@Luka-xx5ve - it's like someone else did all the thinking and we were just amazed. yea, it happens.
This is the most dad video I've ever seen
I concur
I feel attacked. 😄
That's why I'm here. This is awesome.
Wait until you come across Reel Low Dad
You can learn from anyone if you are humble enough to ask. Great job showing this!
Heck , just come watch me mow the grass , it's always in slow motion , I'm 60
Haha.
I hope I have even half the humor you have when I get there..
😂💯
LOL
shure46 sucks to be you old man hahaha!
I want to see a chainsaw. It wouldn't be cool in wood(because wood is opaque) but maybe in clear plastic. I have always wanted to see the blade in slow motion tearing away wood chips
A circular saw would be cool too, especially if you could see how each tooth cuts from a different side.
Bigfoot And Bananaman for some insight. I would not say that chainsaw tears away the wood. It's more of a wedge that shaves the wood. Each tooth on the Chain just shaves a little more off as it's pulled through the wood. Similar to a wood plane shaving wood off. Circular saws do the same thing.
I rarely bother to comment on TH-cam videos, but I came down here to also request chainsaw footage.
I agree with the chainsaw, including circular saws. My question would be about different chain types (not so common) or different circular saw blade types (more common). I know saw blade types are for rough cut (fast ripping) vs smooth cut (usually slower). I imagine there is a trade off between how much material you can knock off with each tooth VS bogging down the motor and loosing RPM & efficacy.
I also want to see a chainsaw, a real nice gas one and maybe a comparison to a decent battery powered one. I'm curious about a few things.
No wonder why it’s harder to mow when the grass is wet. The blade can’t lift the grass up because the water/dew adds up to the weight. This is very educational. Thank you for posting this video. I highly appreciate it!
Mine appears to cut fine. I have to stop often to clean the under side or empty the bag and clean the chute. Letting it grow too long between cuts can add to this problem or even be necessary for this to be a problem.
The scythe deserves its own segment...I’ve seen people mow a field faster than a weed eater can be fueled and started .
One guy wasn't a guy. Yikes. Hope you're still with us.
The scythe is remorseless
Collaborate with Mr Chickadee on the traditional scythe.
Nothing like a razor sharp, just peened scythe... love mine!
YES
It's true. Neighbors must mow lawns whenever a camera is rolling. I don't know how that law got on the books but it is what it is.
edit: Also, as a former landscaper: you can get high lift blades for your mower that cut way better than your standard blades.
Where would you find those high lift blades?
Jackson Kotecki Your local helicopter store of course
fuckgoogleplus lmfao
NightHawkInLight hey dude, love your channel
I wonder if it will help my lawn mower not get clogged all the time.
Lets do a collaboration on a stump grinder. We can show how the teeth disintegrate the wood as they grind the stump away. That would be perfect for a slow mow sequence. I have a brand new one we can use. I've done a few heavy equipment videos like that and have plenty of gear to test out.
Also your retaining wall videos saved my backyard.
yes please
That would be awesome
Would be awesome
Throw in a Chainsaw and hedge trimmer as well, while you're at it. :)
“You’ve spent a ton of your life on a lawn mower”
New Yorkers: am I a joke to you
New Yorker: what's a lawn?
Grass? isn't that something you buy
I like in NY on a farm and mow 10 plus hours a week
Gavin Kvinlaug NYC
@@alejandrosalazar6975 ok but u didn't specify
Yea dont lump the rest of the state in with the "California of the east" (nyc is its own mess that ruins it for the whole state.)
Anyone ever "mow" or "weedeat" with a stick as a little kid?
My name's not important: like in the lines of the driveway?
@@noahshaw8247 yeah, or just tall grass next to an old building 😂
Had to be kinda tall, so on the sideways didn't work the best
yeah i learned how to actually weed eat because we have a landscaping business
I like beating weeds with sticks
I had fencing wire for that! Mainly bigger weeds. Then I sharpened some steel flat bar to do the same thing.
i love you Destin. Your personal hype for figuring stuff out is infectious. These videos, for many reasons, are some of the best pieces of content on the internet.
Hey Destin look into reel mowers, they work just like scissors , the best way to cut grass
I'd love to see that footage again with the tabs bent down to a neutral position. 😀
It would still cut, the tabs simply create air flow to move the clipping out of the deck. It’s just speed, same how a sword cuts. This video is false.
Well, the most obvious thing to study next is the weed wacker, but I'm curious about the garden hose sprayer. You know, the one with the dial that you can use to switch between spray options like, shower, jet, and mist. I'd like to see an explanation of how the water breaks up and spreads out as it travels through the air.
You most likely put more pressure for jet with a different pattern and less pressure for mist with a different pattern
I agree - the weed whacker (also known as a line trimmer or whipper snipper) would be a great second edition to this series.
Not exactly. Spray Systems does the science behind sprayers. The shape of the cavity is very carefully designed to get different spray patterns. A lot more to it than just pressure like turbulence and flow regimes.
Jonathan Tash I want to see the weed wacker
You always study whackers
Hey for fun you should so a slowmo to see if dandelions actually duck under the blade when you mow the lawn 😁
i agree it's weird how they always survive
@@okaylars3248 Try pulling your mower backward over them. They disappear. It's weird but it works.
@@juansolo1617 ... illuminati confirmed
@@okaylars3248 lol it took me a second but that actually sounds perfect.
@@juansolo1617 ahahaha
Lawn series: Does a drop spreader spread more fertilizer when it's full (compared to the last quarter before empty)?
Why do some garden hoses kink and others don't?
Does a sprinkler apply water evenly, or more in some areas?
Is a reel mower like a pair of scissors?
How does an aerator really let the air flow in, although the holes are far apart?
How can you reduce evaporation on your lawn?
How does cutting your awn to different heights affect evaporation, spreading of grass plants, wear resistance, weeds...
Ok two things if you ever think about revisiting this. You should set like a control where you get blades without the tab and see what kind of difference there is and also I wanna know how the old push mowers work the ones with the spiral blade
I just watched a 10 minute video about mowing grass and didn't get bored. You know how to make a good video!! @smarter every day
JakerMB I did tho
A weed whacker has no vacuum so I wonder if the speed of the strings makes up for the need for a vacuum by just hitting the grass blades extremely fast. Also an analyzation of different weed whackers in slow motion would be awesome to watch
The purpose of a string trimmer is to be portable but for small areas. The line wears out, but will not cut your shoes...
That is the trade off
The OTHER aspect of it is that a weedeater can get into DETAIL spots where you CANNOT drive or push a mower easily
So it is truly for trimming. This is why commercial outfits use a big mower - but generally have a team of followers trimming the walks and edges
Finally a video about how the blade looks when actually cutting the grass I was trying to find a video like this for.....well years😂
Excellent video to show how important it is to keep your mower blades sharp.
The blade does create 'lift' (read airflow) but it's not required to cut the grass, or else line trimmers wouldn't work. The grass breaks when the blade speed is high enough that the grass can't get out of its way (inertia). The bent blade is a fan that lifts & blows the cut grass into the catcher or out a chute. That effect stops when the bent bit wears out.
Cylinder mowers (called reel mowers in the US) have opposing blades. One is fixed to the frame, the other is wrapped around the cylinder (usually 5 or more separate blades) and as they rotate they shear the grass between them selves and the fixed blade. They make a much neater cut, and for that reason are used on fine lawns, putting greens, tennis courts etc.
Spencer Wilton my first mower. No ethanol!
I was going to say the same thing. Reel lawnmowers have been around, I'd say, for more than 100 years. No, I can't provide a citation. They typically have a grass catcher on the back. For a push type lawnmower the reel is driven by the wheels via a ratchet system of gears so it can continue to spin even when the wheels were stopped. The sound of the ratchet was a sure sound of summer many years ago.
Even today, the grounds keepers for golf courses use reel type lawn mowers on the greens. A rotary blade just wouldn't do, maybe on the fairways but not the greens.
oooh. thank you!
They also get wracked but non-grass (sticks, rocks, toys, etc.) running through them more easily and more labor intensive, is also why they are better suited to highly manicured small areas.
Also sickle bar mowers and similar used for harvesting hay (just drops it instead of pulverizing).
Have you ever seen a Hover Lawn Mower? I think they came around some Where in the 60's. The lawnmower basically hovered over the grass, like floated over the grass & cut the grass @ the same time. Super maneuverable when it's running.
I didn’t know I needed this video in my life. 🤔😂
I learned something today too... your lawn mower blades are super dull lol
I noticed that to.
It is kinda interesting... at one of my first jobs, the guy I worked for had me use a lawn mower which was later found out to have the blade upside down. It did not cut well, but it did... far better than I ever expected it to.
@@tonysmith5077 *too
I just wanted to kiss those blades with a bench grinder. Or a file. For real.
@@paulstandaert2042 I thought you were me lol
Lawnmower blade, blade of grass
Mowing is actually a sword fight with nature
I’d love to see a deep dive into scythes.
High speed, showing how experienced cutters hold their angle, etc…
Another great video, thanks. At 7:23 if you look close at the left over grass (or shorter old grass) after the cut, your blade is ripping the grass because its a dull blade. Thats how the grass gets the brown jagged ends because of a dull blade which opens the door to grass disease and harder / longer to heal, so your causing unhealthy grass as well. Professionals may carry several blades with them and even switch them out during the busy day of mowing if they see this effect.
Oh you have to do how a chainsaw blade!!!!!! Please please please do a chainsaw blade!!!love this series idea.
Daniel Bisagni that was my first thought too
Daniel Bisagni going with the grain, vs against
Especially looking into cutting edge angles and cutting depth and why they should be adjusted for the type of timber being cut.
A saw chain is an intricate mechanism made of many moving parts - that having been said, there are many videos on how to sharp a chainsaw chain - it is complex and I will not detail it here because it has been talked about elsewhere, most notably by "Swedish Homestead" at YT
Tanner Beverley they cut trees down across grain I belive
You know what you have to do. Make your own blades without the lift tab. Check the slow mo and see if the grass doesn't stand up. Shouldn't be too hard it's just a flat slab of steel.
VicMorrowsGhost better to just heat and hammer the lift edge down. Balance is very important for those blades, mainly for the integrity of the blade deck. The vibration of an unbalanced blade will eventually rip the pulleys out of the deck.
Symmetrically grinding opposing blade faces across a central axis is as difficult as it sounds. Add into that keeping it balanced as the previous comment noted does not make it any easier.
VicMorrowsGhost you can buy mulching blades like that. No tabs. I've had stupid employees put blades on upside down and could barely tell a difference. Rpm fast enough to still cut.
Just go buy some
He also should make a clear deck to let it do it's thing properly. Opening the hatch like that will effect the upward flow, wouldn't it?
Just watching that first clip of the mower cutting grass in slo-mo was well worth it. Amazing work, as usual!
Reminded me of the 'honey I shrunk the kids' movie.
I love this series! If you want more info on this I can take you to the engineering department of Toro and take you behind the scenes. We could also do a series on Heavy equipment with Volvo.
volvo sucks.... cat is better
Thank you DMZ!
This would be neato
I was just going to comment that he should contact folks that manufacture lawn mowers and talk to a mower design engineer. Quit guessing and ask the people who already know.
Please, make this happen!!
Remember the old trick where you unfold a newspaper and lay it across half a ruler. If you hit the ruler fast enough you could break the ruler in half. The speed you hit the ruler at was just too fast for the newspaper to lift up, so the ruler broke. This is how lawnmower blades work. It's speed, not lift. I mean, the lift does help in various ways, but it's certainly not a pivotal part of the process. Please do a video with perfectly flat and straight blades and see what happens. I bet you it'll cut grass pretty well.
Destin, I think you got this one wrong. I agree with Chrispm84. I assert that this is a turbulence + momentum phenomenon. Not a suction one.
The little blades of grass are whipping around in the turbulence and eventually get hit by the mower blade. The mower blade is moving so quickly that the grass can't move out of the way (due to momentum) and get chopped.
I would also suspect that some grass blades require two or more hits before they are chopped down to the mower blade's height.
david garlisch I think Destin is over thinking this. Where I live we don't use lawn mowers but grass cutters. It's basically a high speed fan on a stick that spins a thick nylon(can use steel blades but nylon strings are safer since you arent in danger of a blade chipping) very fast to cut grass and it cuts pretty well. No suction, no wind.
I'd also point out that when using larger farm equipment (good ole bush hog), those blades are elongated chunks of iron swiveling around under a shroud. I don't think there is much of any lift in that equation. It's more like bludgeoning the grass until it short.
Yeah I think it's more of an inertia effect
Chrispm84 Well yes, but what I believe the lift does beside help a little with the cut is eject the grass so is "clean" enough to keep cutting without interference. Thought I've seen mowers with straight blades.
I'd like too see a reel mower like they cut golf greens with.
Great video! Awesome camera work and love the slo-mo the best. Finally got to see how the blades of grass get sucked up then sliced. Mystery solved. Thanks a lot.
You have just confirmed my theory which I have thought about once a week every week from March through November for about an hour since I was 12.
Clay Thomas same
Haha yea
Anyone else wanna see a weed whacker in slow motion?
Yes
Yes
Yes
Jup, with wire and blade please :)
Not just wire and blade but there are two types of wire, round and the twisted square type. Why is one better then the other?
"If you're like me, you've spent a ton of your lives on a lawn mower..." On a lawn mower? Boi i gotta push my lawn mower i aint that privileged 😂😂😂
Mcr and Green Day are life. Dont question it. I got a half acre that I cut with a weed eater due to roots and it’s on a slope.
Stfu emo
I haven't used a lawn mower in years. Lived in an apartment before I moved to where I am now and I pay somebody to cut my grass now.
He could be referring to a lawn tractor, or riding mower.
Christian Basulto that’s the same thing isn’t it?
Twelve years ago I bought a replacement lawn mower blade that was supposedly optimized for "mulching". Behind the regular blade edge with the upward tab, there was a notch, then a second blade mounted higher and angled downward. When I installed it, I noticed two things immediately: 1) the mower was significantly quieter; and 2) cut quality was exceedingly poor.
That's when I learned about the vacuum created by a mower blade - which was cancelled out on this blade by the extra downward-facing cutting edge. The aerodynamic changes related to the lack of vacuum were also apparently responsible for the reduction in noise. I took the blade back for a refund and have used standard blades ever since.
Another fun fact: The tab on the rear of the blade can eventually wear down from friction against the grass clippings it's pushing upward. I've gone through two heavily used blades that, in addition to having a lot of material worn off the front from repeated sharpenings, had the rear tabs (which gently curved upward) worn down to a knife-edge.
Why didn't you use smoke to show the airflow?
NINJABDUDE probably too much turbulent air around the mower from ambient wind, not to mention he's shooting the video at home so what would he use for smoke? He would probably have to use smoke balls which would get sucked up into the blades unless anchored. The grass does a well enough job at showing airflow.
NINJABDUDE yea, or put babypowder or something in the grass and see it get lifted out.
I was going to suggest explosives and rupert gum drops.
NINJABDUDE that's a cool idea but perhaps Hunter is right.
Yeah Destin, why didn’t you make a better video?!?
It's not to "pull the grass up." The lift is designed to expel/discharge the clippings, unlike mulching blades, that have less of the lifting force and are designed to make secondary cuts.
That “tab” is not to suck the grass up. It’s for lifting the grass into the area above the blade AFTER it’s been cut, to allow it to be chopped up into finer pieces. It does not suck anything up.
Sorry I worked landscaping for 20 years. Yes it does. You can buy high lift blades which absolutely create more lift and suction. We ran them on our scag mowers. Airflow increased due to higher lift angle. Made a smoother cut and threw the grass farther. You can watch it suck more air into the deck when you have side by side. We fully tested and verified results from both standard and high lift blades. Night and day difference. But deck design helps too. If there is nowhere for additional air to go it has no benefit. Commercial mower decks are very spacious as far as that is concerned and the better mowers have figured out the best ways to help increase airflow and suction. For example a typical residential mower has a deck that is almost bubbled out for the blades to run. A pressed steel deck. Commercial mowers have a welded box like deck to maximize volume. They then add baffles and lips to further increase and maximize airflow near the blades. Look at underside of scag or exmark mower deck and look at most homeowner mower decks and you can see the difference. I could go on and on
0:23 " i'm just E X C I T E D - LETS DOIT! " - that was infectious and made me smile for quite a while 🙃
I'm not entirely convinced that the upward force from the lawnmower blade plays an especially significant role in the cutting part of mowing. Certainly it's useful overall, since it's what lets the lawnmower collect the grass in a bag or in the case of mulching mowers, suck it up so it gets hit by the blades again and again until it's shredded into little pieces. However, an object moving at 200 MPH will rip or cut through grass regardless of airflow. There's just too much friction against the edge of the blade and inertia making the grass fold over onto the blade as it moves past for there to be any chance of it somehow whipping back around and sliding under the blade intact.
I'd like to see a control test with the curved lifting portions cut off to give a flat blade. Also, what if you installed the blade upside down so that it provided down force? A comparison of the quality of the lawn cut under these conditions would be very interesting! This would test the assumption that the lifting blade pulls flattened blades back up straight again so they're cut to the same length as all the others. If this is the case, doing a comparison immediately after mowing might be a mistake since any blades that were flattened by the mower may still be laying flat. Better to give it 24 hours after mowing for the wind to straighten them up again first.
As far as I can tell, the lifting lawn mower blade is a relatively new invention. Before this, blades were presumably flat, though sadly I can't find pictures of old lawn mower blades anywhere on Google. Apparently there are no antique lawn mower blade collectors for some reason.
Now, what about cylinder blade lawn mowers? The geometry on those makes no sense to me. How do they work?
cylinder blade lawn mowers' paddles/blades push grass into another blade and operate like sissors in that respect.
I can tell you as a Lawn Maintenance Provider that the lifting tab on the back of the blade makes a HUGE difference as to how well that blade will cut. If I use a "Low" lifting tab type of blade, the grass doesn't get cut as evenly or I have to make several passes over the lawn. The "High" lift tabs allow me to make a single pass. Also note that the "High-end" Commercial mower have tall decks (5"+) to maximize airflow under the deck to provide that perfect cut. Great video as always!
The old rotary mowers cut like a pair of scissors as he explained in the video (cutting blade and bed knife blade), but there are commercial mowers that are in the Flail Mower category. They have a ton of little blades on a shaft/drum that spins and cuts grass like a knife cutting paper pretty heavy duty machines.
i don't necessarly agree but i upvoted it for visibility.
it is interesting to answer these questions in more depth.
7:15 doesn't look like it cuts the grass right now.
also the cutting efficiency heavily relies on the bility of the cut thing being able to move away. if you jus a grass blade from the side it will be way easier.
Yes it is. Actually one of the most important aspects besides sharp blades. Yes it will cut, but cutting ALL the grass is the end game. And airflow will provide that. If the grass blades aren't lifted up they will just lay down never making contact with the mower blade. 26 years commercial mowing experience here.
I can’t believe I just watched a 10 minute video about mowing. I also can’t believe I was intrigued. You sir are my favorite hillbilly in the world 😂 and the world needs more of you.
Roll Tide.
How wonderful! As an engineering student, I always wondered what was going on under the lawn mower engine. Thanks for the remarkable video.
lol I thought I was crazy trying to research the science behind how lawnmowers cut grass. Nice to know someone else out there is doing the same. This all started out because I was trying to figure out what the best grindangle would be for cutting the lawn. It would be nice to have a video on The different angles and how it affects cutting the grass. Thanks keep up the good work
A chainsaw blade/chain seems like it has some interesting science behind it. Any thoughts?
RumbleLab
Really fast sharp thingies 👍
RumbleLab link the time
RumbleLab it does. It cuts on the top not the side of chain for 1. Teeth alternate so cuts straight and not pull to the side. Ramps in between teeth so chain only cuts what it can handle without digging in and jamming. Plus chain has to remove the debris as you cut. Low kick back chains have higher ramps so you can't cut as much with each pass and won't jam as hard if it does get caught. That's based on my understanding. Sorry if I mis spoke about something
Yeah it would be interesting to watch the material being pulled out
Joe Smith isn't there a link that "slices" followed by a link that "digs" almost like a knife and a chisel?
Also this one is called - SlowMo-wing.
Damnit
Kris Bendix i see what you did there 😃😂
Get out.
why do people hate puns? I love them
Definitely earned my subscription..I love the "How things work" ...never knew that and I've been cutting for years
Cool video. Always thought the bent up tabs at the back of the blades were to help expel the grass. Now I know better, thanks!
Slow-mo starts at 7:13
Whew, Thank you ~ can't believe it took that long, all that yapping
you have to watch the whole think if you want to appreciate the science of it
thankyou.
MJM Productions I agree 100%, but sometimes I like to watch the slow mo first so I can think about the footage while he discusses it throughout the video.
*Slow-mow.
You just went with your assumption that your hypothesis was correct; that the blade wing is what makes it work. You never tested it without.
Yes that is what I thought. Please cut the wings and compare the results to show the effect. At 5:50 I thought the grass could also be lifted by its own stiffness.
He doesn’t have to because it’s not an assumption, it’s fact.
Then show me.
Highstranger951 that is not how science works. Hypotheses are considered potentially factually true after empirical testing, not before.
Forssa1 do your research guys.
As a follow up to this, it would be interesting to see this compared to how some people just cut their lawns with a scythe... Like completely manually. There's lots of videos on the internet of people doing it, but not many showing the mechanism of what's going on there.
I took delivery of my first reel mower about a month ago. This video confirmed why I was doing it wrong my entire life.
Currently cutting at 1” and thinking of going lower. Yard has never been healthier. Grass doesn’t want its blades bludgeoned to death.
Also I don’t need to cut the front end off to see how it’s cutting. Slowing it down to watch it would be cool to see though.
I learned that mowers pulled the grass up from "Honey I Shrunk the Kids"
HaunterOfKanto that’s a good movie 🍿
Great point, well recognised! And a fun example too :)
It cuts because the grass is wet and sticks to the super fast blades. Flymo lawn mowers blow the grass down.
Same 😁
Slow mow
That is one awesome comment!
Bwhahahaha! I see what you did there.
Not as slow as 343,000, which I've seen
No.
lawrence offley Yes.
I saw a video years ago that talked about what LENGTH of the mower blade needed to be sharpened for the actual cutting of the grass. The answer was, the OUTSIDE 2 inches as this did the majority of the slicing of the standing grass. The reasons for sharpening the rest of the length of the blade, were to aid in the chopping up of the grass AFTER it was cut off, AND to maintain blade speed by reducing blade friction against the air, moisture, and grass particles. I have mowed commercial and residential properties for sixteen years, so this video was extra interesting too me. Thanks for sharing.
I love SmarterEveryDay, but I challenge this one. I suspect the tab on the mower blade is more about pulling the loose clippings up and channeling them out the discharge. I think it is more likely that the grass is being cut because the mower blade is moving sufficiently fast enough that the grass blades can't bend fast enough and they break. String trimmers are also very effective at cutting grass and there is no suction pulling the grass up.
Use a sharp blade and it doesn't have to be moving so fast. Always use a sharp blade. The tabs act just as they do on a snowthrower - they throw. The grass is being bent AWAY from the mower as your approach because the air-pressure from the spinning blades is OUTWARD, but this pressure is highest just as you reach the edge of the deck, then it drops away once you are under the deck and the grass can spring back up to be cut (or bludgeoned) by the outermost edge of the blade. The uncut grass experiences no lift.
Reel type lawn mowers do shear like scissors....
They have rotating blades that shear against a bed knjfe....
Okie Male hahahaha I was thinking the same thing when he was talking about it....... he lost his point right away in the first minute 😂
Cool video en sound effect btw
They also make sickle mowers that work like barbers clippers.
Okie Male , and boy! do they do a good job.!
I was thinking the exact thing about reel mowers when he was talking about that
I felt itchy for you... 0:30
Justin Schmidt hahe
I'm allergic to grass and all I could do is cringe and scratch lol
Lol
Yes
Grass makes me itch like crazy. I think it may be because of the pollin
I’m 25 and younger than both you and your barber and I knew that about lawnmowers from a fairly young age. I’m glad you’re still learning and finding new information without being embarrassed in any capacity about little facts you may not have considered because that’s what I aim to do when I’m your age and beyond.
This isn’t a condescending comment either, I’m both surprised I knew something you didn’t and also inspired by your motivation to keep learning even though your career and studies have left gaps that you’re still figuring out. Keep it up, I love seeing these videos because I don’t know everything either lol
My dad taught me this when I was first learning how to mow my lawn cool to see someone having the same questions I had
A grazing cow will also lift and chop the grass leaving a nice short lawn. Thank goodness they don't spin at 200 mph.
anasmrright what, are you afraid of lawn mowers?
ROFL!! 😂
If it did, make sure to dump buckets of chocolate over it first
anasmrright , You ain't ever been in a twister, have ya!? 😁
Twister (1996) Anyone? Cows do spin in the air. Sometimes multiple times. (The 200 mph moo)
Lawn mooers
Scythes.
Sven Servette i was literally looking at if I could buy a scythe in the next tab lol x
like cutting tomatoes. its a slicing motion instead of a chopping motion. Just watch a video on them and watch the way it moves through the grass and the way the taper interacts with the grass.
Cheesus Sliced what's the difference between those two? Genuine question
Tori Ko between slicing and chopping? Slicing uses the sharpness of blade with minimal force to cut the material with an extended motion. Sliding the edge of the blade across something, all the energy being applied parallel to the cut. When chopping, the energy is applied perpendicular to the direction of the slice, and its a weight or force applied directly to the knife to push the blade through something, using only one part of the blade. Axes chop, scythes slice. In terms of food again, you can chop through bones with a meat cleaver, or slice it from the bones with a boner knife
Edit: a way to think of the kinetic energy difference is pulleys. If you use a series of pulleys, you achieve the same lift with less force but longer motions, while without the pulleys its shorter motions but more force for the same lift
Cheesus Sliced thanks!
A big factor is the sharpness of the blade. Not discussed in this video. A newly sharpened blade cuts the grass cleaner and quicker. The mower is more efficient as the blade has less resistance moving through the grass.
You’re such an interesting, intelligent TH-camr. So fun watching all your videos.
I would be interested in seeing a video(or segment) on the old school rotary style lawn mowers(the sort of barrel shaped ones with no motor.)
I used to do lawn care(fertilizer, pesticides, etc.), and every class I took(often from people with post grad degrees in agronomics) and all my bosses, and everything I've ever read claimed that those are actually superior to the tradition walk-behind/ride-on spinning blade mowers.
supposedly they cut the grass much cleaner, as opposed to tearing the grass the way rotary mowers can do(if you look closely in this video, you can see the blades of grass are often raggedy at the ends after being cut(though this could possibly be due to a dull mower blade.))
this is bad because it hurts the appearance of the lawn(the tips are stringy and discolored), and also because it causes the plant to use more energy fixing the "wound", does more damage to the cells, causes a greater loss of moisture, and in particular makes the grass much more susceptible to disease(just like how getting your hand cut off by a shark, or chainsaw is more likely to become infected(due to the much larger surface area of exposed tissue) than getting your hand cut off by saw, a single clean slice by a very sharp samurai sword.))
however, I do not know why the rotary mowers cut more efficiently. I doubt they cause much of the suction you refer to in this video, and I can't help but think the blades are traveling far slower. it also seems like each section(or even blade) of grass would only have one chance to get cut with a rotary mower, whereas the rotating blade mowers(even though the cutting surface of the blade is only a few inches long at the extreme end of each side of the blade) has several chances to cut each blade(depending on how fast you are going) and thus is less likely to leave little "mohawks" of uncut grass behind.)
I suppose it could be due in part to the fact that the blades on rotary mowers are moving more or less straight in into the grass(almost like a scythe) whereas the blades on the type of mower in this video are rotating in an angular fasion, and may be more likely to "rip" the blade as opposed to making a clean cut, but since the blade is moving so fast, and the moment of contact between the blade and any individual piece of grass is so incredibly brief, I can't help but think that the direction/way the blades are moving would make no difference(if the blades were cutting right near the center of blade, where the linear velocities would be lower, then maybe.)
the only other thing I can think of is that maybe the blades on drum style rotary mowers are sharper(please sharpen your mower blades regularly people), possible due to them being just simple pieces of think stamped metal(at least I think they're stamped, i could be wrong.)
wow. god bless whoever took the time to read that ridiculously long comment about lawn mower blades. lol.
The reel-type mower works exactly like scissors, by trapping the grass between the blades on the spinning reel and a fixed cutter bar.
ooooooh. lol. you'd think I should have known that. no wonder it works so good.
"No Grass is harmed during this video?"
Kedar Nimbalkar that's funny
Tell that to my ripped meat eating friends that dont like u messing w there food’s food
Just stumbled across this video. That tab on the back of lawn mower blades was invented much later. Mower blades were just flat before the grass bag came into play and the clippings had to be lifted and blown into the bag. They also served a dual purpose of mulching by shutting of the exits but keeping the clippings airborne inside of the mower deck long enough to chop them over and over again. What cuts the grass depends on the sharpness and momentum of the mower blade and the weight of the grass blade. “Come on Man”
This is what turned me on to reel mowing! Reel mowing is a clever way of "scissor" cutting grass using a spinning reel cylinder with blades, referencing against a bed knife. You can imagine this method is better for the grass because if properly "tuned", the reel mower avoids (or minimizes) tearing of the grass blade. You're probably aware of this already, and the rotary method is certainly more interesting to investigate! But I hadn't seen this mentioned yet.
lawn tool series... a slow-motion video of one of those hammer-type sprinklers! I know it's fluid dynamics and the force of the hammer that moves the sprinkler back and forth....but man, i would love to see how that looks in slowmo!
Phoenyx 787 you stole my words. That will be a really cool video.
Or better yet, one of those giant water cannon sprinklers they use on farms!
What about a manual lawn mower with no engine?
Matthew Shultz that uses the same principle as scissors or the two blade method
That's a rotating scissor/shear at work there.
Do you mean like an old fashioned push mower?
Here’s a video of mine cutting paper th-cam.com/video/qxDO6aSbSGM/w-d-xo.html
They're called reel mowers. They have a back edge and work like the scissors do.
I use reel mowers at work.( golf course). And it’s an amazing thing you should look at closer. We have a bed knife and a rotating reel witch has multiple blades on it. They interact like scissors and give you an amazing cut
Love your videos. I am old enough to remember that in the early 1960s, rotary mowers had flat blades because they didn't have catchers. In fact I flatten mine with a sledge hammer so there is less drag on the motor and less grass choking up the chute where the catcher isn't attached, and they still mow fine. Furthermore whippersnippers use just inertial cutting. So I don't think the suction thing is that important. Maybe it gives a cleaner cut at lower speeds?? But those old mowers with flat blades cut just fine.
This guy over complicated the matter. He quotes some simple law of physics tried to makes us think he got some higher academic achievement.
Try a manual push mower with rotary blades, they are scissor action. Newer ones are actually a lot easier to use as well.
Golf courses primarily use "reel mowers", basically ride-on push mowers. Pretty cool
I use one of the new ones. It's very easy to push, and good exercise. Biggest drawback is if the lawn puts up seed heads. They get too tall and I need to attack them with a machete.
Reel mowers cut like a pair of scissors, you could go to a golf course and get high speed video of them mowing a green.
I think he's too young to know about reel mowers. 🙂
Reel mowers are still very much a thing.
My uncle has a couple antique ones too
BW Tractors They are practically extinct. Only in a few specialized applications like golf courses and often used by the Amish.
LTVoyager they're also often used on pro ball stadiums with real grass. They're not extinct, just specialized. Because specialized places are the only ones with the training and maintenance department to keep them running effectively
BW Tractors I call that nearly extinct. You can still by buggy whips also...
Blade lift is to move the clippings away to prevent recutting them. A side benefit of the lift is that it causes the grass to be cut somewhat more evenly. The grass is not actually cut or clipped but shattered/exploded at the point of impact. This is nothing remotely like cutting. Think about cutting the playing card with the AK-47. High velocity does some amazing things!
I did a fair amount of green work at a lawn tennis club here in the UK. You're effectively describing the difference between ripping your grass, and actually cutting it. In a rotary blade, it rips the grass and this doesn't end well in the long run. What you do actually want is the 'cutting' scissor type of grass cutting. This is fair better for the grass.
1.7K blades of grass have disliked this video.
They are very edgy, it seems.
Nah, they are just being grass.
lol
939+
I think there are so many cow watching this and dislike it.
How does a weed wacker work because it’s just a plastic wire spinning really fast without any lift tabs.
Og Dumpling and how does it break? It’s deigned to hit grass, and somehow it always fails hitting grass. 🤔
If you're talking about push mowers and edgers that use string, I believe they work simply but applying a lot of pressure to a small area, resulting in shredding.
It's not hard to simulate, if you hold a flat sheet of paper up perfectly flat and get a clean hit on it with lawnmower string, it will slice the paper.
individual grass stems and leaves are much weaker and or thinner than paper, so they get shredded.
it's more akin to the grass being pulverised you could say, as you can look at the deck of a weed eater and see the remains of shredded grass splattered against it.
Also a more dark way to look at it, of you were unfortunate enough to get your leg clipped by one, it would most definitely draw blood and slice clean through the skin even though it's not 'sharp.' It doesn't have to be sharp to cut.
To grasp this you just have to grasp the physics of cutting. Cutting is applying enough force to break the bonds that hold a material together. Sharp objects do this by focusing the force over a small area, which increases the pressure, however you can also achieve it by increasing the amount of force you use over the same area.
Can you cut a block of wood with a dull kitchen knife? There's 2 ways you can do it. Sharpen the knife until it's rediculously sharp, or swing the knife with a rediculously amount of force. The later is how an ax basically works. If you feel an ax blade, it's not exactly going to cut you. But if you swing it, there is so much force behind the swing it plows through whatever it hits regardless of how sharp it dull it is.
That is sort of what is happening with the weed eater string. it's being swing around so fast it doesn't matter that it isn't sharp. It has enough force concentrated in a small enough area (force / area = pressure) that it can 'cut' the grass it touches.
As for why the string breaks. Well, the string is still plastic and being subjected to huge amounts of abuse. Like everything else made of plastic it will give out, especially if you try to cut something with it it wasn't meant to cut or cannot cut that well, such as really thick patches of grass, or if it gets clipped by a stump or a fence or a piece of metal.
Basically the same wacking motion without the lift.
The grass can't bend out of the way so it gets torn
I've also gotten clipped from the weed whacker before. Didn't break skin, but left a REALLY sore welt. This was also a commercial-grade 28.9cc beast, so I was fortunate that I didn't have it at full throttle at the time (it was spinning down).
BlackEpyon I got a weed wacker on my ankle it drew blood
This video illustrates the reason for a sharp well designed blade. As well the need for a well designed deck. I have had a number of lawn mowers over the decades. My 15 year old Ariens has the best suction, pick and even cut.
Huntsville Landscaper here:
Look at String Trimmers.
Commonly known as a weed eater, this versatile tool utilizes helicopter-rotor-like physics to do anything from obliterate weeds to fine tune edges.
Note the gyroscopic effect the spinning head has, resisting tilt and providing steadiness. Most notably with a dual string head.
Note that (for a Counterclockwise spinning head) the left side provides a finer cut with the string "bouncing" off the grass. The right side provides a coarse cut that digs into the grass.
Heavier string makes a huge difference in performance as well. And IS THERE A DIFFERENCE IN THE SHAPE??? There's so so many types of string: round, square, hex, and various twists and plastic hardness.
I better stop or I won't...
Oh, and the direction you swing from in addition to the angle of the head all makes a difference.
AND ANOTHER IMPORTANT THING: can you PROVE that the guard actually helps??? I know it sounds preposterous to even ask, but too many "professional" landscapers take them off.
Stopping for real now.
... for now.
Smartereveryday please try reversing the flap direction on a lawn mower blade in order to see the cut difference between the two blades.
This may seem like a simple one, but you should do a vid on the power of leafblowers. It's always amazed me that a tiny little motor could move so much air. Love your vids and keep up the great work 😍👏👍🖖
I watch one video about how mowers work and now TH-cam is trying to sell me massive industrial mowers
Could you do an examination of whether your lawn will look better mowing fast or slow? Same if the grass is wet or dry?