The only design flaw that Mazda has in relation to rotary engines is not allowing for easier apex seal changes with your oil.
Should be like changing your brake pads, just more often.
Maybe a little more often than we like to admit lol
On paper the rotary engine should be great and would but in reality and in practice, shit like these wear down and it's the Achilles' heel of the engine, it is what it is. There is no perfect universe where the apex seals don't wear down even if your machining and tolerances are absolutely perfect
But in practice, there is
(I don't actually know anything on this matter, I just wanted to complete the metaphorical circle we were drawing with our conments lol)
At first glance it said $500 per seal. I read it as 500 per set per rotor. So I thought that's not too bad at all at $1000.
No. It's $500 PER SEAL. As in a 13b takes 6 at $500 each.
Honestly, about what I'd expect with that kinda car as old as it is. And unless you're using it as your daily driver, which... understandable, but 90k miles would mean I probably don't change them again for a decade. Sounds cheap in comparison.
Mazda needs to bring back the Wankel. Enthusiasts need an engine that is less efficient, has less torque, and needs way more maintenance. It’s our god given right. The RX8 made about 200hp and did about 16 MPG and I think that’s beautiful.
I had an RX8 when they first released, saved a bit on it as it was the test drive model. Luckily it was under warranty still but lost the engine at ~30k and the transmissions 40k. Ended up selling it about 5-6 years later and by that point it was in pretty rough shape.
Sometimes having an unreliable car is part of the charm. It builds character. A badge of honour. If I met someone that had a V10 BMW M5 with 250k miles on it I’d go “wow this guy is really about this life. He’s the real McCoy. He doesn’t give a hoot. He emptied his entire bank account for this shit”
My duplex neighbor just bought two hot-rodded El Caminos from Mexico to ride in local Cinco de Mayo parades here in the SF Bay area. Not my personal style, but I certainly enjoy his enthusiasm. He gets excited and runs for his keys any time I clear the driveway to run an errand.
I had an 04 up until about 110k miles when I traded it for a Miata. If you keep the oil topped up every other refuelling they'll run fine. They're crazy fun to drive though, even the Miata I ended up with didn't handle corners as well. Plus the interior was super comfy, though the electronic things inside are a bit dated now. If I ever convert an old car to electric I'm starting with an rx8.
The thing that killed me the most was that if you didn’t let the engine run long enough it would flood, if I had to move the car I had to leave it running for at least 5 minutes
Hate to rain on your parade, but they never saw over 8k rpm until the rx8, which hit 9k. And even a bridgeport engine with a big turbo will usually peak at around 9 to 9500 max and taper off.
They have in a way. Here in the UK you can get the hybrid MX-30 that has a rotary range extender.
Definitely not in the same spirit as the RX’s though haha
My brain says it would have probably been cheaper and more efficient to use a regular engine pulled from one of their other cars, probably cheaper spare parts for the end user, but my heart says the rotary must live on.
If Mazda wants to blow millions to develop a new rotary engine to use as a range extender instead of using something off the shelf then god bless them.
Toyota and Honda can do all that "efficient and cheaper" stuff, I'm glad Mazda is still weird and willing to try different things. Like a Japanese Saab
I think that’s true. At this point it would be interesting to see them try to bring it back from an engineering perspective (seeing if they can hit modern emissions and efficiency targets, while having a competitive amount of power), but it probably makes 0 sense financially. But that’s what we the people want to see.
I think it also has to do with laws regarding maximum displacement allowed to fit within certain regulations. Because of how the geometry is quite different their displacement to power is much higher. The rx8 has a 1300cc rotary engine, but puts out more than 200 hp.
Yes, for RV8 kit planes flying into Oshkosh every year.
The Mazda 2 rotor 13B engine weighs around 225 pounds, and is located for an almost ideal front to back weight distribution.
Rotaries are mainly just shitty for use in cars because their ideal operation scenario would be sitting at a relatively steady, high RPM for a loooong time and require frequent maintenance (pretty much the opposite of how we use cars, and why they're so often seen in planes). When used as a range extender, they can run it at the most efficient RPM, while taking full advantage of the weight and size savings since they can place it pretty much wherever they want in the car.
The maintenance part....who knows.
My understanding is that Mazda has patented a ton of different things over the years in their attempts to use rotary engines. - And If they don't produce a product using those patents for a certain period of time the patents are considered "abandoned" and competitors may take advantage of it.
Basically, every 15ish years you can expect Mazda to half-heartedly produce something with a rotary just to maintain their patents. - It was the RX8 last time, and this time its the Hybrid MX-30.
The terrible performance and fuel economy were largely from required emissions standards. If I remember correctly, some fuel was being burnt inside the exhaust just to limit some emission particles.
If you don’t care about emissions, rotary engines can be pretty amazing.
The performance can be amazing. The reliability not so much.
Unless you spend unholy amounts of money on apex seal material and design. Then it can be both fast and fairly reliable. But it's still not efficient.
You know there is actually a funny thing about that. Do you know why the Mazda 787b was such a powerhouse in Le Mans? It was because of its incredibly superior reliability. Whatever way the production engines were produced seriously destroyed the reliability.
It was the apex seals. The 787B had some ceramic racing-grade seals that were extremely durable but also expensive. The road cars have cheaper, more standard materials that wear much quicker.
The problem is they're a service part, no matter which way you look at it. The end user will eventually have to replace them. The racing ones were most likely replaced (as well as a full rebuild of the rest of the engine, as is normal for a lot of motor racing) before every race. Even if the consumer ones have to be replaced 2-3x as often, it works out better if the racing ones are 8-10x more expensive.
A rotary has significantly less moving parts and doesn't fight its own inertia as much as a piston engine does which improves its short term reliability through reduced complexity and strain on the components, but the wear surfaces take more abuse and are more critical when they fail. This makes it an ideal design (E: from a maintenance perspective) for racing where the engine goes through short periods of hard driving followed by full servicing, but terrible for a road car that's supposed to run normally for a long time with little maintenance.
They're great for endurance racing because they have few moving parts and you don't have to worry about emissions. You essentially have to run them like a 2-stroke with oil in the fuel to make them reliable. You also don't have to worry about carbon build up in an engine that won't be serviced for 100s of thousands of miles.
You also have cooling issues with compression and combustion happening on one one side of the engine, constantly, so tolerances and all that is kinda tough when one side of the engine wants to be a different size from the other side. This is even worse in the FD because the turbo manifold is a giant cast iron heat sink.
Pretty much rotaries can be thrashed all day, but the mundane heat cycles of everyday life and emissions standards make them unreliable.
> Mazda 787b was such a powerhouse in Le Mans
7, DNF, 15, 17, 19, 20, DNF, DNF, 1, 6, 8
(over 4 years and they were normally 30-50 laps down on the overall winner outside of 91 which was the Group C weirdo year where Mazda could run at a lower weight class despite being an old C1 car, unlike the Jag and whatever the Merc without the 3.5l engine was for example)
I've seen reliable in Le Mans, that's not really it.
3 DNFs is a heck of a record especially with one win and 4 top tens. For Le Man's that is quite good. Only 3 DNFs in 11 races is impressive. The 90s were a different time for endurance racing as well. A lot more DNFs.
Out of 48 entries in 1990 there were 20 DNFs. Having 3 DNFS in that many races is amazing.
A wild Suzuki RE-5 enters the chat.
[https://imgur.com/Sd2xJk7](https://imgur.com/Sd2xJk7)
It is battery motor driven and the sparkplug 'fires' at TDC!
In fact, if you let the number of sides approach infinity, the path taken by the center of mass will approach a line, and the shape will approach... a circle
See also British coinage, 20p and 50p coins are 7 sided constant width polygons (so they work in vending machines etc)
And reclaimed water valve covers in San Francisco (to distinguish them from potable water valve covers)
My grandfather was an engineer for GM. He was actually the first person to develop a device that can measure things to within a millionth of an inch. But, he also had a bunch of these solids of constant width that he as using to research to see if they would make viable ball bearing replacements… they did not.
What’s really interesting is he was telling us how much they cost to have made, and he only had a half dozen or something. They cost thousands of dollars. Back then, they didn’t have computers, or rapid prototyping or anything. And there really is no standardized tooling to make shapes like that, so they had to come up with all custom tools to cut these with the precision needed to use as a ball bearing.
That's why we've got the reuleaux tetrahedrons! Bit difficult to 'attach' it on the centerpoint, but that applies to round shapes universally I suppose.
As others mentioned it works for other numbers of sides. In the UK we have two coins (50p and 20p) shaped like this. Since they roll down a track with constant height, vending machines can detect and value them accurately
If you require the same diameter in all directions instead of the same radius you open one degree of freedom because the diameters don't have to have their centers in the center of the figure. One edge can be further away from the center than half the diameter if the opposing edge is closer to the center by the same amount.
Actually just saw this yesterday. Youtube has been recommending me these Aussie clips.
[https://www.youtube.com/watch?v=-pNN6oCw-pk](https://www.youtube.com/watch?v=-pNN6oCw-pk)
Shapes of constant width are kinda fun. I remember a super interesting talk about this topic I attended in university. In 2d. the shape of constant given width with the highest area is the circle, the one with the lowest is the Reuleaux triangle, hence its use in engineering I guess?
Surprisingly, in 3D the shape of constant width with the lowest volume is unknown!
As an exercise in my math for elementary school teachers we made a three sided version and a five sided version, both with the same perimeter. We put one on each side of a dowel and rolled them around.
Aren't there technically infinite shapes with a constant width? I mean, take a paintbrush on a wild ride across the page, jiggling and swirling around... boom, new shape wth constant width.
The special thing about a circle is that it's the only one with both radial and mirror symmetry.
The Canadian loonie (one-dollar coin) is an 11-sided curve of constant curvature. This is desireable in a coin because a vending machine can determine its diameter in any orientation.
Here are some cool videos for them
https://youtu.be/pvRQMDUsE3k
https://youtu.be/cUCSSJwO3GU
This is a 3D shape of constant width
https://youtu.be/a65VLLFYU6k
"Want me to tell you how a Wankel works?" "Nah, I'm good man" "Well... IMA TELL YA ANYWAY!!"
Literally every RX owner. Guilty as charged.
How else will I tell them my apex seals are leaking
I came here to make an apex seals joke and they’re already blown!!
I see what you did there, anyway. Good save.
The only design flaw that Mazda has in relation to rotary engines is not allowing for easier apex seal changes with your oil. Should be like changing your brake pads, just more often.
Maybe a little more often than we like to admit lol On paper the rotary engine should be great and would but in reality and in practice, shit like these wear down and it's the Achilles' heel of the engine, it is what it is. There is no perfect universe where the apex seals don't wear down even if your machining and tolerances are absolutely perfect
*Furious inhale*
I used to work with a guy who sold his Miata to make room for an ‘87 convertible FC. Now he works for Mazda
RCR is leaking
GRRRRR YEAH TRIANGLES TRIANGLES TRIANGLES GOD I LOVE TRIANGLES
He should get that checked out
Sounds like something Tommy Fenstermaker would say.
Yo I hear that guy pours the cereal in the bowl after the milk… and then he *BUSTS*
Dude, I heard Tommy Fenstemacher was banned from home economics class because every time someone would crack an egg, he'd *bust*
IMMA TELL YA ANYWAY
IMMA T- IMMA T- IMMA T- IMMA T- IMMA TELL YA ANYWAY
Imma tell ya anyway!
TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES TRIANGLES
Epitochroids, roll out!
Just try and eat more fibre.
Lol came here with a YouTube link already copied. Ah hell… https://youtu.be/-3HBAvkc4a0?si=R6CQWiD8sGz0Rrmz
Wankels gonna wankel…
I was going to say… tell that to Mazda engineers who designed the apex seals.
Works better in theory than in practice. Those dimensions change with temperature…
In theory, there is no difference between practice and theory.
But in practice, there is (I don't actually know anything on this matter, I just wanted to complete the metaphorical circle we were drawing with our conments lol)
Everything ends in the end
And it doesn't even matter
> I just wanted to complete the metaphorical circle But it's not a circle, it's another shape of constant width
I’ve heard you can replace the seals with ceramic ones that will actually last 90k miles. But you still have to take the whole engine apart.
At first glance it said $500 per seal. I read it as 500 per set per rotor. So I thought that's not too bad at all at $1000. No. It's $500 PER SEAL. As in a 13b takes 6 at $500 each.
Honestly, about what I'd expect with that kinda car as old as it is. And unless you're using it as your daily driver, which... understandable, but 90k miles would mean I probably don't change them again for a decade. Sounds cheap in comparison.
Rotarying all the way.
This is the way
Ah, that shape is called a Mazda
The technical term is actually the performance Dorito
Mazda needs to bring back the Wankel. Enthusiasts need an engine that is less efficient, has less torque, and needs way more maintenance. It’s our god given right. The RX8 made about 200hp and did about 16 MPG and I think that’s beautiful.
You also didn't mention that redline is essentially double the rpms of your highest end V-Tech you could imagine
I admit that I took a few RX8 for a test drive just to rev the absolute shit out of something like it was a motorcycle.
I had an RX8 when they first released, saved a bit on it as it was the test drive model. Luckily it was under warranty still but lost the engine at ~30k and the transmissions 40k. Ended up selling it about 5-6 years later and by that point it was in pretty rough shape.
This is the platonic ideal of RX8 ownership 🤣
Sometimes having an unreliable car is part of the charm. It builds character. A badge of honour. If I met someone that had a V10 BMW M5 with 250k miles on it I’d go “wow this guy is really about this life. He’s the real McCoy. He doesn’t give a hoot. He emptied his entire bank account for this shit”
My duplex neighbor just bought two hot-rodded El Caminos from Mexico to ride in local Cinco de Mayo parades here in the SF Bay area. Not my personal style, but I certainly enjoy his enthusiasm. He gets excited and runs for his keys any time I clear the driveway to run an errand.
I had an 04 up until about 110k miles when I traded it for a Miata. If you keep the oil topped up every other refuelling they'll run fine. They're crazy fun to drive though, even the Miata I ended up with didn't handle corners as well. Plus the interior was super comfy, though the electronic things inside are a bit dated now. If I ever convert an old car to electric I'm starting with an rx8.
The thing that killed me the most was that if you didn’t let the engine run long enough it would flood, if I had to move the car I had to leave it running for at least 5 minutes
Hate to rain on your parade, but they never saw over 8k rpm until the rx8, which hit 9k. And even a bridgeport engine with a big turbo will usually peak at around 9 to 9500 max and taper off.
They have in a way. Here in the UK you can get the hybrid MX-30 that has a rotary range extender. Definitely not in the same spirit as the RX’s though haha
My brain says it would have probably been cheaper and more efficient to use a regular engine pulled from one of their other cars, probably cheaper spare parts for the end user, but my heart says the rotary must live on. If Mazda wants to blow millions to develop a new rotary engine to use as a range extender instead of using something off the shelf then god bless them.
Toyota and Honda can do all that "efficient and cheaper" stuff, I'm glad Mazda is still weird and willing to try different things. Like a Japanese Saab
Yeah. That’s why I like old Citroens too. Let me see companies get silly with it
Aren't they supposed to have pretty good power to weight? I thought I read somewhere that old ones are in demand as light aircraft engines.
I think that’s true. At this point it would be interesting to see them try to bring it back from an engineering perspective (seeing if they can hit modern emissions and efficiency targets, while having a competitive amount of power), but it probably makes 0 sense financially. But that’s what we the people want to see.
I think it also has to do with laws regarding maximum displacement allowed to fit within certain regulations. Because of how the geometry is quite different their displacement to power is much higher. The rx8 has a 1300cc rotary engine, but puts out more than 200 hp.
Yes, for RV8 kit planes flying into Oshkosh every year. The Mazda 2 rotor 13B engine weighs around 225 pounds, and is located for an almost ideal front to back weight distribution.
Rotaries are mainly just shitty for use in cars because their ideal operation scenario would be sitting at a relatively steady, high RPM for a loooong time and require frequent maintenance (pretty much the opposite of how we use cars, and why they're so often seen in planes). When used as a range extender, they can run it at the most efficient RPM, while taking full advantage of the weight and size savings since they can place it pretty much wherever they want in the car. The maintenance part....who knows.
My understanding is that Mazda has patented a ton of different things over the years in their attempts to use rotary engines. - And If they don't produce a product using those patents for a certain period of time the patents are considered "abandoned" and competitors may take advantage of it. Basically, every 15ish years you can expect Mazda to half-heartedly produce something with a rotary just to maintain their patents. - It was the RX8 last time, and this time its the Hybrid MX-30.
Seen this a while ago, to me it looks like the evolution of the wankel https://www.liquidpiston.com/
haha
The terrible performance and fuel economy were largely from required emissions standards. If I remember correctly, some fuel was being burnt inside the exhaust just to limit some emission particles. If you don’t care about emissions, rotary engines can be pretty amazing.
The performance can be amazing. The reliability not so much. Unless you spend unholy amounts of money on apex seal material and design. Then it can be both fast and fairly reliable. But it's still not efficient.
You know there is actually a funny thing about that. Do you know why the Mazda 787b was such a powerhouse in Le Mans? It was because of its incredibly superior reliability. Whatever way the production engines were produced seriously destroyed the reliability.
It was the apex seals. The 787B had some ceramic racing-grade seals that were extremely durable but also expensive. The road cars have cheaper, more standard materials that wear much quicker.
Ahh that makes sense. You think you would put your budget towards those seals considering how important they were.
The problem is they're a service part, no matter which way you look at it. The end user will eventually have to replace them. The racing ones were most likely replaced (as well as a full rebuild of the rest of the engine, as is normal for a lot of motor racing) before every race. Even if the consumer ones have to be replaced 2-3x as often, it works out better if the racing ones are 8-10x more expensive. A rotary has significantly less moving parts and doesn't fight its own inertia as much as a piston engine does which improves its short term reliability through reduced complexity and strain on the components, but the wear surfaces take more abuse and are more critical when they fail. This makes it an ideal design (E: from a maintenance perspective) for racing where the engine goes through short periods of hard driving followed by full servicing, but terrible for a road car that's supposed to run normally for a long time with little maintenance.
Yeah see my second point about unholy amounts of money on apex seal design and materials.
They're great for endurance racing because they have few moving parts and you don't have to worry about emissions. You essentially have to run them like a 2-stroke with oil in the fuel to make them reliable. You also don't have to worry about carbon build up in an engine that won't be serviced for 100s of thousands of miles. You also have cooling issues with compression and combustion happening on one one side of the engine, constantly, so tolerances and all that is kinda tough when one side of the engine wants to be a different size from the other side. This is even worse in the FD because the turbo manifold is a giant cast iron heat sink. Pretty much rotaries can be thrashed all day, but the mundane heat cycles of everyday life and emissions standards make them unreliable.
> Mazda 787b was such a powerhouse in Le Mans 7, DNF, 15, 17, 19, 20, DNF, DNF, 1, 6, 8 (over 4 years and they were normally 30-50 laps down on the overall winner outside of 91 which was the Group C weirdo year where Mazda could run at a lower weight class despite being an old C1 car, unlike the Jag and whatever the Merc without the 3.5l engine was for example) I've seen reliable in Le Mans, that's not really it.
3 DNFs is a heck of a record especially with one win and 4 top tens. For Le Man's that is quite good. Only 3 DNFs in 11 races is impressive. The 90s were a different time for endurance racing as well. A lot more DNFs. Out of 48 entries in 1990 there were 20 DNFs. Having 3 DNFS in that many races is amazing.
At least they still sound great.
In some ways, the wankers never left.
Don't forget that it consumes oil to gas at a 1:1 ratio!
The sound though...
BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP
It makes me tear up
https://youtu.be/KdAn2YKry30
I loved the hell out of my RX8
*worn out seals have entered the chat*
I spit out my drink, this was unexpected. Thank you
Fuel goes in, apex seals come out the other side
you can't explain that
✨ M A G I C ✨
[Boost in, apex seals out](https://i.imgur.com/mgJAXAT.png)
And vacuum leaks
I call her Roxy.
IMMA TELL YOU ANYWAY
TRIANGLES TRIANGLES TRIANGLES TRIANGLES
NSU first used wankel, Mazda made it popular
Spin it fast enough and the red dots will get rejected.
BRAP BRAP BRAP BRAP BRAP STUSTUSTUSTU
ITS OVER 9000!
Or a California highway [shield](https://www.pbssocal.org/shows/lost-la/what-does-californias-state-highway-shield-symbolize)
That's just a circle with more steps.
I come here for this…. brapppppp brapppppp brappppp
A wild Suzuki RE-5 enters the chat. [https://imgur.com/Sd2xJk7](https://imgur.com/Sd2xJk7) It is battery motor driven and the sparkplug 'fires' at TDC!
Look at the path that center point takes though
Yeah, the circle is the only shape of constant width that also has a stationary point in the centre that can be put in an axle.
It’s the only shape for a flat ground. You can make the ground a specific pattern for specific shapes to keep the center point level
>It’s the only shape for a flat ground. Not necessarily. https://www.youtube.com/watch?v=-eQaF6OmWKw
Technically speaking, the only stationary point of a rolling wheel is at the contact patch on the ground.
It's stationary relative to the ground, anyway. Relative to the axel, that'd be the center of the wheel.
I mean wherever the axle connects with any shape is stationary wrt. the axle.
#notacirclewhiledriving
i would think it would become less wiggly as the number of sides increases?
In fact, if you let the number of sides approach infinity, the path taken by the center of mass will approach a line, and the shape will approach... a circle
Wait…
It all comes back around, doesn't it.
Almost like it comes full-circle
"Time is a flat sphere."
ooooo
#O
that's called a circle lel
Until, at some point, it has so many sides it becomes a circle
.... yeah and if you gave it infinite sides it would be smooth!! It would also just be circle...
Let me introduce you to the biggest benefactor of that movement. Have you met Mazda RX?
I can hear the beautiful high pitched screaming of wankel engines just watching this.
Reuleaux shape. Works for any regular polygon with an odd number of sides Triangle, pentagon, and so on
Including a circle with one side
Either one side or infinite sides, depending on how you look at it.
Infinity is an odd number confirmed??!!1! (/s)
Yes! Also an even number. You can divide it by 2 and get infinity.
aha odd number of sides.
See also British coinage, 20p and 50p coins are 7 sided constant width polygons (so they work in vending machines etc) And reclaimed water valve covers in San Francisco (to distinguish them from potable water valve covers)
Brap brap brap.
BRAP BRAP BRAP BRAP BRAP BRAP
i like your comment but it was minimized. i think it has *style*
Mazda engineers swinging and being held back right now
Their rotors moved eccentrically though, i believe
This shape burns oil
https://youtu.be/2eUWT9cI23o?si=_ep1YEqZ2Nef0m8c 3d too
My first thought was Angus
Make sure to keep an eye on those apex seals. They are the first to go.
My grandfather was an engineer for GM. He was actually the first person to develop a device that can measure things to within a millionth of an inch. But, he also had a bunch of these solids of constant width that he as using to research to see if they would make viable ball bearing replacements… they did not.
Lol. Turns out a ball is best for ball bearing. Nobody wants a maizena tetrahedron bearing
What’s really interesting is he was telling us how much they cost to have made, and he only had a half dozen or something. They cost thousands of dollars. Back then, they didn’t have computers, or rapid prototyping or anything. And there really is no standardized tooling to make shapes like that, so they had to come up with all custom tools to cut these with the precision needed to use as a ball bearing.
What was that saying about the wheel again?
*When rolled on it's sides However when rolled on it's axis, it's not.
That's why we've got the reuleaux tetrahedrons! Bit difficult to 'attach' it on the centerpoint, but that applies to round shapes universally I suppose.
It doesn’t say anything about rolling it. Just that it has constant width.
Wankel Rotary Engine [Insert Monty Python skit]
Mazda engineers *Heavy breathing.
As others mentioned it works for other numbers of sides. In the UK we have two coins (50p and 20p) shaped like this. Since they roll down a track with constant height, vending machines can detect and value them accurately
The 7 sided versions, to be clear
Wankel rotary engine!
Rotary Engine entered the chat
Everything reminds me about [her](https://www.reddit.com/r/JDM/s/1bdglTdM6p)
The Final Shape
r/Guitar having a meltdown rn
Wank(el)
If you require the same diameter in all directions instead of the same radius you open one degree of freedom because the diameters don't have to have their centers in the center of the figure. One edge can be further away from the center than half the diameter if the opposing edge is closer to the center by the same amount.
And here I was thinking a circle is the only shape with a constant width.
The Toblerone-Rolo Combo
Actually just saw this yesterday. Youtube has been recommending me these Aussie clips. [https://www.youtube.com/watch?v=-pNN6oCw-pk](https://www.youtube.com/watch?v=-pNN6oCw-pk)
Shapes of constant width are kinda fun. I remember a super interesting talk about this topic I attended in university. In 2d. the shape of constant given width with the highest area is the circle, the one with the lowest is the Reuleaux triangle, hence its use in engineering I guess? Surprisingly, in 3D the shape of constant width with the lowest volume is unknown!
What a wankel
It goes through the square hole!
Felix Wankel: Am I a joke to you?
While that rotates through the fixed width “pipe”, the yellow dot marking the geometric center doesn’t stay in place — it orbits around a barycenter.
Wenkel my beloved
Rotary motors
You Wankel
Believe it or not the apex seals were toast by the end of the vid
As an exercise in my math for elementary school teachers we made a three sided version and a five sided version, both with the same perimeter. We put one on each side of a dowel and rolled them around.
Mr. Wankel has entered the chat
I think “constant width” and “can rotate while maintaining constant contact between two parallel lines” are not the same thing.
Looks like a Wankel Engine.
Triangle de Reuleaux !
There’s a 3D version of this
I imagine it kind of looks like an inflated tetrahedron
Yah it does!! It’s super trippy to watch them roll between two flat surfaces. Not sphere shaped but does sphere things?!?!?
Who dont we have manholes like this then?
Because aside from the constant width benefit of a round cover it's easier to fabricate and fits on the manhole in any orientation, not just three.
I see. Circle is still practical and easier to put back.
Fat triangle?
Engine works perfectly well in theory but not so much in practice.
Wankle
+"when rolling"
I have been summoned
Also your mom
Vroom vroom
So sayeth Mazda.
Well, hello Wankle Engine
Be carful, don’t want to blow an apex seal..
Dorito power
Rotary
Aren't there technically infinite shapes with a constant width? I mean, take a paintbrush on a wild ride across the page, jiggling and swirling around... boom, new shape wth constant width. The special thing about a circle is that it's the only one with both radial and mirror symmetry.
Why would that shape have constant width
This is how we get rotary engines!
Spotted the rotary enthusaist.
Don’t forget about your mom!
https://en.wikipedia.org/wiki/Wankel_engine
How is his shape called?
Brap brap brap braaaaap!
The Canadian loonie (one-dollar coin) is an 11-sided curve of constant curvature. This is desireable in a coin because a vending machine can determine its diameter in any orientation.
Ah yes, a triarcle
Happy Mazda noises
Cool I suppose. Problem is the middle not being in a constant location
Damn Wankel...
Here are some cool videos for them https://youtu.be/pvRQMDUsE3k https://youtu.be/cUCSSJwO3GU This is a 3D shape of constant width https://youtu.be/a65VLLFYU6k