[HN Gopher] MT-Propeller 11 blade propeller delivers 15% increas...
___________________________________________________________________
MT-Propeller 11 blade propeller delivers 15% increase in static
thrust
Author : voidmain0001
Score : 71 points
Date : 2023-01-06 19:29 UTC (3 hours ago)
(HTM) web link (www.mt-propeller.com)
(TXT) w3m dump (www.mt-propeller.com)
| [deleted]
| WalterBright wrote:
| The Wright Bros achieved 90% efficiency with their propellers.
| Adding 15% to that gives 103.5% efficiency, which I'm not buying.
| vasco wrote:
| You don't add them up like this. I can make a car use 50% less
| fuel an infinite amount of times, not just twice.
| rbanffy wrote:
| > I can make a car use 50% less fuel an infinite amount of
| times,
|
| At some point it'll be running on nuclear fission, as you
| won't be able to feed it a single whole atom. ;-)
| WalterBright wrote:
| Please rethink your statement. You cannot get more motive
| energy than the energy put into the propeller.
|
| > I can make a car use 50% less fuel an infinite amount of
| times
|
| No, you can't. Conservation of energy applies.
|
| P.S. I didn't "add" them, either. 90% x 115% => 103.5%
| rootusrootus wrote:
| Kind of related: Do the same efficiency dynamics that apply to
| wind turbines apply to a fan providing propulsion? I.e. if a one-
| bladed fan is the most efficient for capturing wind, would it
| also be the most efficient airplane propeller or boat propeller?
| Obviously efficiency isn't the only consideration, but I am
| curious and I expect there's going to be some fan experts in this
| thread...
| TylerE wrote:
| Due to much higher rpm, balance is imporant, and your diameter
| is constrained (you want the propellor as small as possible
| because you want to A: keep the whole thing underwater and B:
| Not bang the tips on the bottom.
| colechristensen wrote:
| With aircraft you can't just say "efficient" you have to point
| out what you're trying to optimize.
| Hendrikto wrote:
| Seems like 1 blade would theoretically be optimal, but due to
| requiring a counterweight, a two blade design is superior. [0]
|
| [0]: https://aviation.stackexchange.com/questions/23009/what-
| are-...
| swayvil wrote:
| Prime number so no harmonics? Therefore no... vampiric eddys or
| vacuum bubbles...? Just my first guess.
|
| How's 13? 17?
| rbanffy wrote:
| Obviously 13 would optimize for luck.
| travisgriggs wrote:
| For reference on more or less blades, aviation stack exchange has
| some great discussions on this subject. One of my favorites
|
| https://aviation.stackexchange.com/questions/23009/what-are-...
| emptysea wrote:
| Interesting so basically the more blades, the less efficient it
| gets but you get more thrust
|
| Sort of makes sense why drones have a couple blades so they can
| putter along for hours
| spullara wrote:
| Ok, how much better is 13 blades?
| buildsjets wrote:
| 2 better than a prop that only goes to 11.
| rbanffy wrote:
| It's luckier as well.
| [deleted]
| samwillis wrote:
| Somewhat related thread [0] from last month about the "tipless"
| Sharrow MX-1 prop [1] which achieves efficiency gains of between
| 9-15% over comparable 3-blade propeller designs. They started out
| working on an aircraft propeller but pivoted to a watercraft
| prop.
|
| 0: https://news.ycombinator.com/item?id=33949895
|
| 1: https://www.mby.com/gear/sharrow-mx-1-tipless-
| propeller-1101...
| post_break wrote:
| I immediately questioned cavitation and that link delivered.
| That's INCREDIBLE. The only issue is the price of course. That
| looks like a perfect candidate for 3D printing and then
| machining the final part vs billet.
| TaylorAlexander wrote:
| > That looks like a perfect candidate for 3D printing and
| then machining the final part vs billet.
|
| Now you need two expensive machines, not just one. Billet is
| not that expensive. I've seen people suggest this before and
| I looked on their site. They show a multi axis CNC machine
| making the parts. You would need exactly the same machine to
| post machine the 3D printed part, but now you have a second
| expensive and slow process to manage (the metal 3D printing).
| With billet a huge bar of material shows up, you slice each
| piece in a few minutes, mount it in your CNC and go. 3D
| printing feed powders have their own expensive processes they
| need to go through, so they probably cost much more than
| billet, reducing any potential cost savings on the material
| side. And the second expensive machine and process adds a lot
| of new expenses. Plus, you have to validate the product all
| over again instead of just selling them.
|
| I bet the high price is mostly due to patents and lack of
| competition. It is probably not inherently super expensive to
| make, beyond the need for a high end multi axis CNC machine.
| TylerE wrote:
| That makes it a great candidate for near-net casting. That
| way you save the 80% of tre billet you'd be turning into
| chips, and your fancy CNC gets more parts per shift.
| samwillis wrote:
| Ultimately I suspect if they wanted to make these in
| significant volume, die casting or loss wax casting then
| machining would be correct route forward. 3D printing metal
| is _expensive_ and the parts are likely to not be as strong.
| Most 3D printing (sintering) processes for metal result in a
| slightly porous part that needs sealing, those small gaps
| produce imperfections.
|
| https://en.m.wikipedia.org/wiki/Die_casting
|
| https://en.m.wikipedia.org/wiki/Lost-wax_casting
|
| Take a look at turbine blades in jet engines, they are
| incredibly complex with tiny air holes. They are made using a
| loss wax then machining process.
| foobarian wrote:
| I love how the stroboscopic effects in the video recording makes
| it look like the blade is spinning slowly like in videogame or
| anime show airships.
| hindsightbias wrote:
| What's the weight?
| stevehawk wrote:
| their 7 blade is ~225lbs.. so I'd guess at a minimum it's ~265#
| johntb86 wrote:
| Why are they only using odd numbers of blades?
| Cerium wrote:
| Generally odd numbers of blades are better for vibration.
|
| I know that in wind turbines they are favored because it
| reduces the effect of the blade crossing the tower. When one of
| the blades in a three blade wind turbine crosses over the tower
| the force on it is reduced (since the wind is already slowed by
| the presence of the tower). The other two blades are in maximum
| loading, but balance much of their forces against each other
| reducing the bending moment on the turbine shaft.
| JumpCrisscross wrote:
| Easier to balance; if everything is even, you need to balance
| two blades to counter one misbehaviour, and do so perfectly to
| avoid introducing new misbehaviours. (They're prime for
| resonance reasons. I don't remember what, specifically.)
| mannykannot wrote:
| Four years ago they were using a nine-bladed propeller, so
| while having a prime number may be desirable, it does not
| seem to be necessary.
| mhb wrote:
| Why would they be easier to balance?
|
| The hand-waving about resonance also pervades that reddit
| "explanation" thread which doesn't explain anything about
| what prime or odd numbers of blades have to do with resonance
| in a single propeller.
| lazide wrote:
| "Prime numbers are generally used to reduce the magnitude
| of resonances. These occur in a non-linear multi-frequency
| system when two of the frequencies o1:o2 match at a ratio
| p:q, where p,q are comprime integers."
|
| Per https://physics.stackexchange.com/questions/484288/why-
| choos...
|
| It's also matched by practical experience - engines which
| have simple low integer multiple resonances in moving parts
| (like opposing 2 cylinders, or inline 4 cylinder) tend to
| have large vibrations/ + resonances that need special care
| and work to handle, or require running at much lower speeds
| to avoid self destruction.
|
| Most propellers and fans have 3 blades because of this,
| plus additional tradeoffs efficiency wise.
|
| More blades will move more air/media per rpm but with more
| friction (reduced efficiency).
|
| Fewer blades (2 or the absolute worst, 1) causes more
| vibration and requires more work to balance + cancel
| resonances.
| mhb wrote:
| Thanks. The explanation there makes sense. Still, this
| must be a secondary effect since there are plenty of
| examples of even-bladed and non-prime bladed propellers.
| lazide wrote:
| Sometimes, the constraints make the extra work
| worthwhile. It's an engineering problem.
|
| Typically, you'll see more blades when you have a limited
| area you can cover with the blades (aka, low wings or
| stubby wings, or lots of engines relative to the wing
| size) and need more power/thrust. Adding more engine
| power is easy enough, if the decrease in overall
| efficiency and stronger airframe required are ok. It's
| not a super common trade off, but it's not that uncommon.
|
| If the 'more blades' math means it's an even number, then
| so be it. Balancing them more carefully, strengthening
| the airframe in problems areas more, etc. is all part of
| the equation. It is more work though.
|
| You'll see similar tradeoffs between something like a jet
| ski water impeller and a cargo ship prop.
|
| Jet engines have similar type of trade offs - max power
| vs overall efficiency, or efficiency at cruise vs
| efficiency during variable condition use. Or noise vs
| power.
|
| The type of engine used in a fighter jet makes very
| different tradeoffs than in an airliner.
|
| Adding ducting around a prop or fan also allows much
| higher total thrust for the given real estate, at the
| cost of weight and a bit of efficiency.
|
| 3 is usually the cheap and easy answer. Sometimes it's
| even the exhaustive and time consuming answer too!
| JumpCrisscross wrote:
| > _Why would they be easier to balance?_
|
| Have you balanced a fan? The wobbles aren't solely at the
| blade points. Having a blade opposed by nothing helps avoid
| a problem where one blade balancing throws another off.
| mhb wrote:
| It's still not obvious why this would be different for
| even vs. odd blade numbers or why changing one blade
| throws the others "off". If you have two blades and
| change one, you need to be concerned with the other
| blade. If you have three blades and change one, you need
| to be concerned with the other two blades.
| tus666 wrote:
| At what point does a prop become a fan?
|
| A 777 engine has 22 fan blades, twice this thing.
| mcarmichael wrote:
| The relevant conceptual distinction seems to be whether the
| aerodynamics of the blade(s) are conceptually independent, or
| interdependent. Better explained here:
| https://en.wikipedia.org/wiki/Propeller_(aeronautics)#Aircra...
| dmoy wrote:
| > At what point does a prop become a fan?
|
| Linguistically, a prop becomes a fan when you anchor it to
| something immovable, or attach it to something movable but
| without any intention of propelling it using the prop.
|
| Fan - try to move the air around, but not the thing it's
| attached to.
|
| Prop - try to propel the thing it's attached to
|
| Edit: I realize that might sound ambiguous given terms like
| "turboprop" and "turbofan" both of which are on planes.
|
| The turboprop uses air to speed up propellers to move the
| plane. A turbofan uses just accelerated exhaust from the
| engine, and the fans are just a means of feeding the engine
| combustion material (air)
| buildbot wrote:
| I am not sure this is really correct - turbojets (as in
| fighter jets) sound more like what you describe, turbofans if
| I remember correctly, get most of the thrust (>70%?) from
| bypass air around the combustion, and very little from actual
| combustion thrust. It just also feeds it's own combustion
| chamber air to keep the fan part going. Perhaps it is a fan
| if enclosed? Vs. a prop if not?
| justsomehnguy wrote:
| >Perhaps it is a fan if enclosed? Vs. a prop if not?
|
| Stipa Caproni
| rbanffy wrote:
| Dear Lord! Half of the lift is due to the repulsion Earth
| feels from it.
| imnotreallynew wrote:
| Most modern fighter jets have turbofan engines as well.
| polishdude20 wrote:
| That's not true about a turbofan. A large part of the thrust
| is actually from the fan itself. The bypass air that never
| goes into the combustion chamber produces most of the thrust.
| jonsen wrote:
| "A turbofan thus can be thought of as a turbojet being used
| to drive a ducted fan, with both of these contributing to the
| thrust.":
|
| https://en.m.wikipedia.org/wiki/Turbofan
| bitwize wrote:
| Back in the 80s there were experiments run with propfans --
| propellers with many stubby blades that offered near jet-like
| performance while consuming half the fuel. They never got
| anywhere because propfan engines were large and noisy and the
| dropping price of oil made the fuel economy concerns less
| urgent.
| rbanffy wrote:
| A think a lot of the noise was because the blades were
| counter-rotating.
| netr0ute wrote:
| > what point does a prop become a fan
|
| I don't know, because I think the whole purpose of a prop is to
| be a fan.
| lazide wrote:
| No quite. Fans == move air, relative to the thing the fan is
| mounted to.
|
| So a jet engine has fans, because it is moving air into and
| around the engine, but not using them to move itself around
| directly (It uses the jet of air created by the thermal
| expansion from the burning fuel and compressed intake air to
| do that, mostly).
|
| Propeller == moves something through air (or another media
| like water) directly.
|
| Semantics, mostly.
| hnburnsy wrote:
| for those wondering...
|
| https://www.reddit.com/r/AskEngineers/comments/g39s6s/is_the...
| mhb wrote:
| I read 80% of it and I'm still wondering.
| Scene_Cast2 wrote:
| I'd imagine that, just like in other industries, there are tons
| of metrics (or counter-metrics) that are also important. Some
| that come to mind are efficiency, noise, vibration, cost,
| maintenance, stall characteristics, RPM requirements, weight, etc
| etc. From some fiddling with RC quads, I remember that increasing
| the number of blades does increase thrust, but at the cost of
| efficiency and several other parameters.
| Ekaros wrote:
| My understanding as well. You increase on metric and make some
| other one worse. In the end it is complex process of finding
| some balance between these.
|
| Not that there isn't some improvements that can be made like
| have been done with improved materials(less weight), computer
| design and so on in more complex engines.
| AmVess wrote:
| The cost of this blade setup means no one will buy it. Very
| high cost to purchase and equally high cost to maintain for
| such a tiny benefit. I had a laugh at the noise reduction
| claim. Sure, it will reduce noise, but the open exhausts on
| planes are the loudest part unless some nitwit is screwing
| around with the pitch.
| stevehawk wrote:
| I can't say I have the numbers to dispute this. But the
| loudest thing on my Cessna is not the open, 1970s era
| exhaust. It is definitely the prop whipping through the wind.
| vlovich123 wrote:
| Would that change when using an electric motor?
| rbanffy wrote:
| I'd say the most favorable arrangement for noise would be a
| pusher configuration, with the engines close to the back of
| the plane instead of a tractor config on the front. This is
| done on the Piaggio Avanti. Not sure how well it works, but
| it looks like a spaceship.
|
| Eviation electrical plane recently changed their pusher
| design to a tractor, but kept the engines on the back
| (IIRC, they started with a central big one and two
| auxiliary ones on the wingtips for use during takeoff).
| stevehawk wrote:
| The big wins here are likely the increase in thrust and
| ultimately cruise speed, which makes twin props more
| competitive with very light jets, and the decrease in noise
| which may make more airports accessible to the aircraft in
| question due to local noise limitations.
|
| The big loss here is purchase price and maintenance price. But
| that's on a scale that's probably not bothering a person who
| can afford a brand new Beechcraft King Air or to completely
| refurbished a used version of the plane in the video (they quit
| making the Piper Navajo 30 years ago).
| MonkeyMalarky wrote:
| If you trade efficiency for faster cruise speed, is your trip
| being shorter a net win for fuel costs?
| TylerE wrote:
| No, because drag scales with v^2. Going 10% faster requires
| 21% more power (and thus fuel), but only reduces trip time
| by 9%.
| jcims wrote:
| Props with high blade count substantially reduce noise for drones
| as well
|
| https://youtu.be/1nk74KEIc2c?t=138s
| buildsjets wrote:
| I'm really not a big "fan" of MT's cheezy wooden propellers. They
| call them "Natural Composite" but it's really just
| densified/compressed wood with a thin fiberglass wrapping. Here's
| an example of what you can expect from in-service damage, a
| Jetstream 41 recently hit a bird, shed a blade, and it shot right
| through the passenger cabin. The hilarious thing is that the
| government investigation called it a "survivable accident"
| because no one happened to be seated in the row that it shot
| through. https://avherald.com/h?article=4f2a35e6
|
| I was involved in the evaluation of proposed repairs to a
| Beechcraft Bonanza with a 3 bladed MT prop that taxied into a
| vinyl traffic cone at idle speed. The Beech shed two prop blades,
| bent the engine mount and firewall. There was a slight cut in the
| traffic cone, but it was returned directly to revenue service.
| FullyFunctional wrote:
| Are the wooden construction essential to the new blade design?
| What are the Beechcraft Bonanza props made of?
|
| (As a complete layman, not even a pilot, I love the sound
| profile of the proposed props)
| buildsjets wrote:
| Normally, the prop on a Bonanza is made of aluminum. Based on
| observation of prior incidents, I would expect no or
| negligible damage to an aluminum propeller in the same
| circumstance. However, even if no external damage is seen,
| some engine manufacturers (and insurers) require a complete
| engine teardown and inspection in the event the propeller
| contacts an object while the engine is running.
| [deleted]
___________________________________________________________________
(page generated 2023-01-06 23:00 UTC)