My name is Destin. This is Smarter Every Day. I did a video previously on this
channel about how a weed eater line breaks when you
go up against something like, I don't know, a chain link
fence or something like that. Aw, that's awesome. That's awesome. But today, I want to address
a couple of different things. What do you call this device? I call it a weed eater. A lot of people made
fun of me last time. This particular box store
calls it a string trimmer. But there's a ton of
different things you can-- oh what's this? What is this? Google Trend results. Just so convenient
that this was here. It looks like most
people actually use the same term I do. Weed eater. Interesting. If you're up in like, what? Michigan, Pennsylvania,
New Jersey, some of those little states,
you might say weed whacker. But if you're in
Australia or the UK, you might say strimmer
or something like that. Long story short. Most people call
it a weed eater, which is why I use that term. It's, you know, gener-a-sied. There was a brand
called Weed Eater. But anyway, for the
purposes of this video, we're going to call
it a weed eater. That's how I grew up saying it. And I think that's how
you should say it too. This is one of the most
overwhelming decisions for me when it comes to purchasing
products for my yard. So, if you think
about it, there's a really cool option here. You could get these things to go
in the head of the weed eater. Basically replaces
the auto feed head. These weed eater lines below. My question is, which
one should I buy? And there's a lot of
different factors like price, durability of the
line, things of that. The diameter of the line. I want to look at
what cuts best. Because my goal is to cut grass. So it only makes sense
to want the shape that cuts grass the best. And there's a bunch
of different options. You got this
triangular type stuff. You got this star
shaped pattern. You know, there's round. There's square stuff. So today on Smarter Every
Day, what I want to do is use a slow motion,
high speed camera to look at the very minuscule
macro view interaction between a weed eater line-- specifically different
shapes of weed eater line-- and one blade of grass. And we'll see if we can
see any difference at all in how they cut. Let's go get smarter every day. Goggle up. Except I don't know
where my goggles are. I'll find them before we
do science, I promise. We're in the garage. And we're going to answer
a very simple question. What line cuts best? So if you look right here, it's
really, really hard to see. But we've sectioned off little
pieces of weed eater line, and we've got them
under the microscope. I'll show you the
shapes in just a minute. That's really cool. But look at this. These are the old
oscilloscopes that I purchased for the oscilloscope video. It's an oscilloscope
music video. I think you'll dig it. When we made that, we
got this beautiful cart. And it's wonderful. I can't imagine what a boss
you would be like, in the 90s, if you had your oscilloscope
on a cart like this. But this is an old
Tectronics cart. It has now been converted into-- I know. I know. It's great. Yeah. It's been converted into a
weed eater approach-o-matic. And what we've got here. Let me-- well, I'll
show you the view. We have a macro lens on that
camera zoomed all the way in on a single blade of grass. That single blade of grass
has a set weight on it. As you know, grass blows
over with a weed eater. However, we wanted to have
a uniform amount of tension on the grass, so it's a
repeatable experiment. So what we're trying to do is
isolate all of the variables with the exception of the edge
interaction of the weed eater line with the grass. Trent, chief button pusher
for this experiment. Do not let me forget my goggles. That's important. So under the microscope, we have
sectioned just a little bitty piece of weed eater line. And we've got it on
the microscope slide so we can look at
the cross-section. I'm going to back light it. Let's see. Let's turn this on. Oh yeah. Look at that. OK, so this is the
first one I've got. It's a round line. It is a-- I think the manufacturer
calls it a razor core. It's basically
just a pure circle with a different density of
plastic in the center, right? OK. Let's go to the next
line we're going to test. This is around line that's gray. I think they call this titanium
or something like that. But clearly, there's
no titanium in this. You'll notice there's
a notch on this side. There's a really interesting
reason that that exists. I'll explain that later. All right, let's
go to the next one. So this is a triangular line. And this one's called
ugly twist, I think. So you can see that it's got
a different kind of plastic, or at least a different
color plastic on the edges. Let's go over here. Now, this one's interesting. This is a star pattern. I'm going to cut the
light off, see if we can-- yeah, look at that. Oh, that's cool. We got a weird artifact
in our lens there. That's interesting. What else we have? Oh yup. Here's the round square. I need to focus on that one. Or a dull square. Let's call that a dull square. It reminds me of a cartioid. But it's not a cartioid. And then the last
one we have here, this is-- we'll call
this a sharp square. Let me adjust-- yeah. Look at that. It's just like the
circular one, but it's got the little edges
on the outside. Now let's go do it. We're going for speed. I found my glasses. Thank you for remembering. So let's start off
with this stuff. Oh, we've got to open
the garage, right? So we don't have
carbon monoxide issues. OK. First line is what we
call the razor core. I already cut it. It was too far forward. I'm an idiot. Is it focused? MAN: Yeah, it's focused. OK, here we go! OK, slow that down and
watch one more time. If you look closely,
this is less like a cut and more like a rip. Each blade of
grass is different. So we did three
tests for each shape. Reviewing these shots one at
a time would take forever. So I think the
most efficient way to present this data to you is
to put all three on the screen and let you make your own
qualitative observations. Next, we went to the
gray, round line. Compared to the razor core,
the shape and the diameter's pretty much the same. So as you would expect,
so were the results. The first time we really
learned something interesting was with the triangular
cross section. The line is quieter. It's way quieter. The reason the twisted
triangular line is quieter is super interesting. If you've ever noticed,
some car antennas have a spiral winding on them. I've been told that this isn't
about receiving radio signals. It's about inducing
more turbulence, and thus reducing wind noise. The twisted triangle
has the same effect. And I assume that's part of
the reason the gray, round line has notches in it as well. Who knows, though? That might be just so it breaks
more and you buy more line. Anyway, listen to
the side by side of the round line and the
twisted triangular line and see how much quieter it is. Oh wow. I expected the triangular line
to have a cleaner cut because of the sharper edge. And that's what you see on
the first blade of grass here. But interestingly, not on
the other two in this shot. Yeah we learned something
on the triangle that time. So I've always thought,
man, triangle line must be great because it's got
that pointy side, you know? But I never thought about
one side being flat. And you would have
like, a big old smack. It's like, hitting somebody
with an open hand versus like, when it hits with the
sharp edge, it's like, not only does-- Oh! We need to do this back. Hey weed eater dude! You want to come check this out? Oh, we could not
have planned this. There's a guy that
weed eats around here. And he's on the street. He parks on my street. What's your name? ROBERT: Robert. Robert, I'm Destin, man. Nice to meet you. You running weed eaters all day? ROBERT: Weed eater
and lawn mower. DESTIN: So you're you're a
weed eater expert, Robert? I don't know about expert. DESTIN: How many hours a
day do you run a weed eater? Sometimes, 8-10
hours a day sometimes. DESTIN: You are an expert. I just made you an expert. OK. DESTIN: OK, so the question is,
what shape of weed eater line is best? Robert jumped right in and
reviewed the high speed footage and started making
comments right off the bat. He suggested that we weigh
each line in a certain length and calculate its
linear density. And he also walked
me out to his truck and gave me a piece of the
line that he uses every day. ROBERT: This is $18 a roll. You've got a sharp
square, is what you got. ROBERT: Yeah. You've got fancy sharp square. It's like a square that's
got a point on each side. Can you see that? We're going to call this
sharp, sharp square. And we also weighed a set length
of all the rest of the line. All that being done, it's time
to move on and test the star. This actually surprised me. As you can see,
the star line seems to create remarkably clean cuts. OK, this one's dull square. From what I can tell here, it
seems like dull square rips through the grass, causing it
to de-laminate and rip apart vertically rather than
cutting straight through it horizontally. Now we're going to test
the sharp square, which is the heaviest line and
also has the largest cross section, which
makes me think it's going to behave like the
flat side of the triangle. Keep in mind here, we're only
doing three tests per line. So this isn't really
statistically significant. But you can get a qualitative
feel for what's going on here. This seems to be
cutting better than some of the other lines, the
dull square, for example. But it also seems to be
ripping just a little bit. But with this much
weight behind the line, you would expect it to go
through a lot more cracks. So this stuff seems
to cut cleaner. But see, it's a
trade off, right? Because this stuff
clearly is more massive. So if I was going up against
brush and stuff like that, I would want the massive line. Let's try what the dude gave us. It's time to test the
sharp, sharp square, the line that Robert gave us. And I'd just like
to say that, it is interesting to look
at yourself performing an experiment. Because sometimes you can easily
see your own confirmation bias. For whatever reason,
I had already decided that the sharp, sharp
square was the best line. And you can tell that by
what I said immediately after cutting the engine off. Clean cut! That's-- it's the answer. Turns out the high
speed disagreed. There's a lot going
on with this one. It seems like it's both
ripping and cutting. But it also doesn't seem to
hit the same spot every time. This line seems
to be very stiff, to the point that
when it spins up, it doesn't completely
flatten out into a disk. One string goes high. The next string goes low. And as you can clearly
see here, this often causes it to strike a different
position on the grass blade with each rotation. Also, if you think
about the shape of the corner of
these edges, it's possible that instead of
going through the grass and driving through
it like a wedge and blowing the
grass apart, it might be pulling it towards
the center and making it hit the center of the line. Sure enough, if you look
at the wider slow mo shot, you can see that
every once in a while, it will pull away a little
plug of grass when it strikes. The star shape seems to be
doing something similar. But somehow, it still
manages to make a clean cut. I would love to hear
you in the comments tell me what you
think is going on. And I'm going to tell you about
the sponsor for this episode. And then I'm on to
tell you what shape I'm going to buy moving forward. And we're also going to
show the slow mo to Robert and see what he has to say. I hope you enjoyed this
episode of Smarter Every Day. It is sponsored by Express VPN. If you want to check
it out, you can go to ExpressVPN.com/smarter. Find out how you can get
three months for free. A VPN is a virtual
private network. And to have all these things
that it would be great if I told you, I'm sure. But what I'm going to
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screen here, Express VPN, I use it to shield
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service provider that you use can legally sell your
data to advertisers. In the UK and
Australia, it's required that they save your data. I don't like that. So I use Express VPN
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go to ExpressVPN.com/smarter. Find out how you can get
three months for free. I would greatly appreciate that. When you support
the sponsor, you're helping Smarter Every Day
helping me do crazy stuff with the weed eaters. And I really appreciate that. ExpressVPN.com/smarter. All right. Here we go. Time for the results. After running this
test, I realized there were things I
could have done better. For example, I probably didn't
push it in at the same rate every time. I probably didn't push
it in fast enough, which means I got partial
cuts occasionally. The blades of grass
themselves were different. Overall, this is just not
rigorous scientific research by any stretch. But it should arm you
with enough information so that next time you're
looking at this wall of options, you can make an
informed decision. For me personally, if
I'm cutting thin grass around the house, I'm going to
be using a star shaped line. It's the only one that
I saw that actually looks like it's cutting. Everything else looks like it
was ripping the grass to me. Also, the fact that it's
smaller seems like it would give me better control. If I was cutting
thick stuff all day, or maybe some brush
near trees or obstacles, I'd probably go with
the sharp square, because it seems heavier
and more durable. But it's not so stiff that
it doesn't track well. So yeah. I'm going to go with these two. I'll leave affiliate links
down in the video description. You can click
those if you'd like to order some line like this. Also, I thought it'd be
interesting to leave links to other people's tests
and what they think. To round out the video,
I'd like to show Robert the slow motion of
the star shaped line as well as the sharp,
sharp square he provided to see what he has to say. The sharp, sharp square? Exactly. He already knows-- he
already knows the lingo, man. I observe things. What do you think? I think this right here,
being a smaller in diameter is giving you the cleaner
cut, which I think possibly is creating a few more
revolutions out of the weed eater. Oh, because it has less drag. Yeah. Less drag. So it's faster. Maybe a little faster. Why don't we hire
Robert to make this video? I think you're right? And also the-- I think the bigger
stuff that you're using, I think it's tougher. I think you could like,
get in the bush with it. Yeah. Yeah we tear up some
stuff with that. So it's a trade off. So if you're like in
a dinky residential, like, I'm just going to do
this next to my flowers, you could probably use
something like that. Go really fast and just
like, more precise. But if you're getting in the
thick of it, use the big stuff. Yeah. If you're getting into some
stuff under some trees. I'd like to see it on YouTube. I mean I can just go
ahead and subscribe. It's called Smarter Every Day. I just convinced
Robert to subscribe. Did you subscribe? I subscribed. DESTIN: All right. ROBERT: And I will
like and share. Robert's with it, man. Yeah, is this it right here? That's it, yeah. OK. All right. Subscribe. I'm telling you, man. Alabama people are with it. Some of us are. I'll get a notification,
I guess, when you put-- Yeah. ROBERT: --something
new on there. DESTIN: You'll
get a notification if you hit the bell. ROBERT: Yeah. Let me hit the bell.
I love how kind Destin always is towards workers. He knows they know a lot about their stuff, he asks, listens and he learns from them. I just love it.
As Destin said, it was not a rigorous scientific study, but I would be interested to see how cutting performance changes with wear.
Wife: I dont care what we watch.
Me: I'm gonna watch a video about weed eater line.
Wife: ugh
17 mins later with the wife intrigued the entire time.
Me: you just watched an entire video on weed eaters.
Wife: why was that so fascinating? I didnt know there was so many shapes.
Thank you Destin for putting out another stellar video about a subject that did not interest my wife. You were able to make a video interesting enough that it pulled her attention in and never let go.
Weed-eater is totally right. Weed wacker would also be accepted
Whole family sat down and voted on which shape would cut best. Our kids had fun as the ensuing drama unfolded over who guessed correctly or incorrectly.
I wonder if the star shape functions similarly to the divots on a golf ball which help to induce turbulent flow or less flow separation due to the turbulent boundary layer such that it "slices" through the air (or grass in this case) with more efficiency.
Might be a stupid question, but was it mentioned why grass being cut cleaner was better? Was this assumed because it would make the grass look better? Or does it have to do with how grass grows better if it's cut cleaner?
I think adding a 2nd test with a real world example in a 1 sqare yard of grass would've been better. Adding weight to the blade of grass skews the results incorrectly. Also type of grass would be important as well. I'm sure a grass farm would be able to provide various types of grass and all equal sizes.
Something to consider is that the string's job isn't just to cut the grass, it also needs to throw it out from the trimmer to keep if from getting bogged down. There are metal saw blade style trimmer heads that I imagine cut grass really cleanly, but the grass piles up on top of the blade and jams it. The only one I've used that works well is the ones that are triangle or Y shaped, and those generally have a beveled edge, but are by no means sharp. You couldn't cut yourself on it if you tried.
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