How Lawn Mower Blades Cut Grass (at 50,000 FRAMES PER SECOND) - Smarter Every Day 196

How about a robomower company sponsorship? I think some of those use a different spinning cutter design.

Benjamin S. Scarlet

Do a scythe for comparison. Slicing, but no opposing blade.

Benjamin S. Scarlet

I was always scared of getting my feed stuck under a lawn mower....not sure how I feel about knowing how it works :D Thanks for the video thou!

Sharkphoria by Johanna Kohler

That’s so cool! Would be a fun little DIY project during free time

David Cichowski

My ram pump has been running for 20 yrs. 24/7 . I design, sell and install them... <a href="https://www.youtube.com/watch?v=yHqDkd7KdPg" rel="nofollow noopener" target="_blank">https://www.youtube.com/watch?v=yHqDkd7KdPg</a>

Heard somethin scary about PVC the otherday. <a href="https://www.livestrong.com/article/125022-health-risks-plastic-water-pipes/" rel="nofollow noopener" target="_blank">https://www.livestrong.com/article/125022-health-risks-plastic-water-pipes/</a> emphasizing the primary ingredient being a known carcinogen, manufacture/disposal toxins, and burning releasing hydrochloric acid.

Growing up, I remember watching my father tinker around with a homemade device called a hydraulic ram pump in the yard. He would use it as a way to pump water into a large container without having to use any electricity. I found it pretty fascinating because the design was really simple and yet very effective. He would only gather PVC and a few parts and pieces from the hardware store and the result was a pump that was powered solely by gravity. I'm not sure if this device would fit in with your lawn tools series, however I think you would find the physics of this device quite compelling. I've only read about the science involved but couldn't quite wrap my head around the concept. It would be pretty neat if this pump was explained in a way I could better understand. Anyway, thanks again for yet another awesome video!

David Cichowski

It would be interesting to have dust or smoke around the mower blades so you can see what the air currents are actually doing. I am skeptical that the vacuum has much effect on making the grass stand up straight to be cut. I suspect the tabs on the back of the blades are more for helping the clippings out of the mower.

diyVT

Hey, Destin! I would love to see a Weed Whacker work in slow motion. If a lawnmower works by creating lift, and putting tension on the blades of grass, then a weed whacker has no such mechanism. It would work by spinning very, very fast compared to a lawnmower. I suspect that the twine of a weed whacker hits a blade of grass so fast that the grass cannot overcome its own drag, and move out of the way fast enough. If this is true, then if a weed whacker is JUST fast enough to cut grass in normal atmosphere, I suspect it would not work under a vacuum.

Pizza Guy

This kind of video would be great. I would like to see how ball affects with all forces that are on it. Slow-mo clip of hitting ball would look amazing

Jakub Urbanski

<a href="https://www.youtube.com/watch?v=xflY5uS-nnw" rel="nofollow noopener" target="_blank">https://www.youtube.com/watch?v=xflY5uS-nnw</a>

Hey Destin, always enjoy your videos. Just wanted to reach out as I manage a private golf club in Nashville TN. Would be happy to have you up later in the year if you'd be interested in comparing the differences in residential mowers and commercial mowers that we use. Also, I've always thought a smarter every day video on physics and actions of the golf club and how it interacts with the golf ball would be cool as well. Let me know if you'd like to explore either. email me at mbgt72@gmail.com

Weed eater... There's a ton of fertile ground there at high speed. Interaction with various surfaces/shapes (sidewalk edge, Woody weeds, fence posts, ant beds)

Dillon Allen

No vacuum system like a riding mower, but these can cut grass very effectively. My dad called them a "yoyo" but they seem to be known as grass whips. <a href="https://www.youtube.com/watch?v=6Gq1gNVZNnI" rel="nofollow noopener" target="_blank">https://www.youtube.com/watch?v=6Gq1gNVZNnI</a> You can get them at places like Walmart. P/N 551508900 Might make for interesting high speed, and safer than power equipment.

Rod Lane

In addition to the comments about reel mowers, many commercial manufacturers advertise about how much suction their deck has compared to the competitors. The front of a Ferris commercial deck is angled at 45 degrees. Supposedly this allows the grass more time to stand up before it encounters the blades. Slow motion footage of a chainsaw would be awesome. There’s a lot going on with the cutting edge alternating with a chip clearing tab. Also, I’ve heard that large tree harvesters cut with every link, whereas handheld tools cut with every other link. Loppers would make a good video on mechanical advantage. You could use load cells to compare the effort for a simple pivot vs a four bar linkage. I also second the suggestion for a slow motion string trimmer video. 2 stroke vs four stroke could also be a good topic along with how 4 stroke trimmers oil themselves (dry sump, splash).

Tim and Chrissy G

It’s not officially lawn equipment, but I would LOVE to see a bailer knotter in SloMo.

Tim and Chrissy G

These are also called reel type mowers. Many people believe they are healthier for the grass and give a better cut. Small ones often operate the reel via the wheels (ground drive). Sports fields, especially golf courses favored these over rotary mowers for many years ( and may still).

Tim and Chrissy G

Legit questions: #1 If you put some kind of clear cover over the cut-off section of the push mower, could you see what's going on inside without changing the air flow? #2 With my discharge chuteless mulching push mower, if no (or minimal) air is going out, how can more air come in and keep sucking the grass up? Or is it the same(ish) air just going up and down like a torus and that's what keeps the cut grass moving inside of the deck allowing the blade to chop it up super fine? Ok nevermind I just answered my own question, just got smarter twice in one day..

Check out sidebar sickle hay mowers on a farm. They use the scissor effect. (hedge trimmers are based on the same idea) Hay mowers don't beat the grass up as much as a lawnmower or a bush hog mower. String trimmers would be interesting to see in slow motion as well. In fact, something like the knotter on a hay baling machine would be super interesting to watch in slow motion. They are VERY interesting how they work.

KC

When you get done with lawn tools, come out to my tug boat. It's physics heaven here. Mass, acceleration, tension compression, friction, buoyancy etc.

Chris nailed it, The phenomena that you documented only occurs with a rotary mower. As Chris stated a reel mower cuts just like scissors. Then there are flail mowers, sickle bars etc.

Dude. Did you just say that lawnmowers don’t have a proper scissor cut? Well, let me show you the wonders of the cylinder type, mower blades - they’re cool AF &amp; have a fixed, straight blade (at cutting height) &amp; a cylinder with 3 or 4 spiral-shaped blades, facing out, that as the cylinder turns, mate with the straight cutting blade. Here’s one (well, 5 units in a tractor-towed array) in glorious action <a href="https://youtu.be/6VqpxDYMYRs" rel="nofollow noopener" target="_blank">https://youtu.be/6VqpxDYMYRs</a> and here’s the kinda thing I had to use, as a kid <a href="https://youtu.be/p_E9v0RP3oU" rel="nofollow noopener" target="_blank">https://youtu.be/p_E9v0RP3oU</a>

Chris Phillips