SlowCo
1 MW
[youtube]AQV-Ia5Cx9E[/youtube]
Awesome!
Awesome!
Joby eVTOL
- Thread starter SlowCo
- Start date
ZeroEm
1 MW
Range 150 miles. :thumb:
Hillhater
100 TW
Get real !…There is nothing silent about any prop driven aircraft !
Even Owls and Bats make a racket when they take off !
liveforphysics
100 TW
They are crazy quiet for a propeller craft. More quiet than being near a busy highway.
So much love and respect to Joby and there incredible team of premium engineers and scientists to come so far in perfecting EV VTOL.
Joben has been a major inspiration and influence in the path my life has taken, I'm so grateful!
So much love and respect to Joby and there incredible team of premium engineers and scientists to come so far in perfecting EV VTOL.
Joben has been a major inspiration and influence in the path my life has taken, I'm so grateful!
PaPaSteve
1 kW
Hillhater said:Get real !…There is nothing silent about any prop driven aircraft !
Even Owls and Bats make a racket when they take off !
The modern prop driven aircraft that most of us know is powered by a internal combustion engine with no muffler system on the exhaust.
Most of the prop noise is generated by the speed of the tip dancing in the region of subsonic.
Around 2010 ~ 2012 JOBY and Makani Power had a cooperative working relationship.
Makani put considerable effort designing props with the aim towards reducing noise while improving performance.
8,000 computer runs were done looking at the possibilities.
After the CAD model was done I made the molds, did the composite work, balanced the props, and performed the stress / noise testing.
I see slight changes in the current JOBY props mostly in the overall size and tip profile.
Makani project, owned by Google was shelved in 2020.
BTW ... Google founders Larry Page and Sergey Brin both have have their own similar projects.
Chalo
100 TW
For what it's worth, ordinary fan blades built for low noise are less efficient than those built for thrust.
When I see a new design for a million dollar flying car, I see the collapse of civilization move a step closer. It feels like the stage just before someone comes up with a rich-bastard vehicle that burns honest working people for fuel.
When I see a new design for a million dollar flying car, I see the collapse of civilization move a step closer. It feels like the stage just before someone comes up with a rich-bastard vehicle that burns honest working people for fuel.
Hillhater
100 TW
Actually i was thinking more obout all the electric drones that are becoming common..
…nothing silent about those.
And those turbine powered helecopters that you hear the blade beat way before they are close enough to see or hear the low wine of the turbine.
I can understand that this is “less noisy” …
…..but silent it will not be !
ZeroEm
1 MW
They said they are building blades/props to test. I'm sure they don't want to give up efficiently or thrust for decibels. Maybe looking for a balance of the two.
No matter what anyone thinks, this is moving forward. :thumb:
No matter what anyone thinks, this is moving forward. :thumb:
PaPaSteve
1 kW
Hillhater said:
Have you viewed the video in the opening post ?
The contemporary helicopter blade has a single profile for the entire length so the real pulling power mostly happens at the tip which must be held under sonic speeds to prevent destruction and obvious noise issues.
Blade profile on these modern electric props are designed to pull at the same amount regardless of diameter where each profile resides. i.e. inside diameter pulls the same load as the tip.
Blade speed is reduced as much as possible which maintaining enough lift.
Tip is also designed to reduce sonic disturbance.
Typical small drone spins the blades much faster.
Chalo
100 TW
PaPaSteve said:
That's been the design intent of aircraft props since the Wright Brothers got distracted from making bicycles. If you hadn't noticed, they're still very noisy. So much so that jet engines are a quieter alternative.
PaPaSteve
1 kW
Chalo said:
Sure it was a design intent.
They just didn't have the modern computer tools to perfect the process.
Nor did they have the much quieter electric propulsion.
BTW ... My response was addressing Hillhater's helicopter comment.
red
10 mW
- Joined
- Mar 28, 2009
- Messages
- 34
Chalo,Chalo said:
IIRC, the Wright Brothers tried then abandoned the research for an ideal prop, saying the problem may not be resolvable. Now we have the ability to get the design right, with computers.
The Un-Ducted Fan (a modified turboprop with counter-rotating blades) is reported to be significantly quieter than the normal airliner.
I believe that the UDF propulsion design, powered by outrunner motors, and fed by hydrogen fuel cells, could produce a clean, quiet airliner using renewable fuels. The fuel cells from a few of the Ballard fuel-cell transit busses might do the job. A reasonable battery pack could be used to provide good take-off power, if needed.
Chalo
100 TW
red said:
One of their props was tested at 77% efficiency, compared to 85% for a propeller today. So they were doing pretty good with intuitive engineering.
Well, noise was one of the reasons that development of unducted fans was discontinued.
https://apps.dtic.mil/sti/citations/ADA223687
https://www.flightglobal.com/commercial-engines-open-rotors-struggle-with-noise/84246.article
I recall Joby has the highest-quality laminations, and they were using ones that are 0.20mm.
I don't know what the current standard is, but if you make laminations thinner and thinner to reduce eddy current waste-heat, there is a point where the thickness of the insulating shellac adds up in a lamination stack to the point where a thinner lamination actually results in less steel per stack of lams.
Because this was for aircraft, and Joby was investing in extreme efficiency, I suspected that 0.20mm is the thinnest practical lamination. I am very impressed by the improvements in the Leafbike hubmotor using 0.35mm lams compared to the common 0.50 in cheap hubmotors.
I don't know what the current standard is, but if you make laminations thinner and thinner to reduce eddy current waste-heat, there is a point where the thickness of the insulating shellac adds up in a lamination stack to the point where a thinner lamination actually results in less steel per stack of lams.
Because this was for aircraft, and Joby was investing in extreme efficiency, I suspected that 0.20mm is the thinnest practical lamination. I am very impressed by the improvements in the Leafbike hubmotor using 0.35mm lams compared to the common 0.50 in cheap hubmotors.
Hillhater
100 TW
Yes, of course.PaPaSteve said:
But unlike some who may have a dog in the fight (?) , i noticed how the recording was carefully produced to minimise any sound from the craft, and explanations about the sound was from the chase aircraft !
And yes, i saw the sound charts..convincing that the noise is REDUCED….
…but still not silent as stated in the title !
PS , prop design did not stop with the Wright brothers, and Computers are not only just being applied, .
I see you accept that the prop design is a compromise between performance (efficiency ?) and sound generation..
…[ assume you ment “whilst” rather than “which” ?]
PaPaSteve
1 kW
This will be the end of my contributions to the prop discussion as I don't recall what the Makani prop efficiency was.
Probably was above average but that would be assumption not actual first hand recalled facts.
The test stand thrust test did see better results when compared to the first prop provided by an outside "expert" source.
Lighter and more reliable too.
The primary design goal was reliability ... 3 aircraft in a row were lost to prop failures.
Failures happened so quickly after launch and destruction so complete it took 3 flights to understand what happened.
The secondary design goal was noise reduction and in that respect the design and engineering staff was quite pleased.
Overall, the testing procedures and data recording improved significantly because of the failures.
Probably was above average but that would be assumption not actual first hand recalled facts.
The test stand thrust test did see better results when compared to the first prop provided by an outside "expert" source.
Lighter and more reliable too.
The primary design goal was reliability ... 3 aircraft in a row were lost to prop failures.
Failures happened so quickly after launch and destruction so complete it took 3 flights to understand what happened.
The secondary design goal was noise reduction and in that respect the design and engineering staff was quite pleased.
Overall, the testing procedures and data recording improved significantly because of the failures.
liveforphysics
100 TW
Wright brothers props were efficient only because they were spinning 350rpm with 6hp going into a large disc area.
Huge respect to you PaPaSteve, I don't know if we ever met in person at Joby, but the propeller is 95% of the design magic in a VTOL being practical to use in urban environments. I remember the hours spent on the prop dyno scratching my head at the grams of thrust/watt numbers, and how some efficient props were surprisingly loud, despite wasting that extra energy in noise. Achieving both low noise and great thrust efficiency and peak thrust numbers is one of the most formidable design challenges humans have tangled with.
Huge respect to you PaPaSteve, I don't know if we ever met in person at Joby, but the propeller is 95% of the design magic in a VTOL being practical to use in urban environments. I remember the hours spent on the prop dyno scratching my head at the grams of thrust/watt numbers, and how some efficient props were surprisingly loud, despite wasting that extra energy in noise. Achieving both low noise and great thrust efficiency and peak thrust numbers is one of the most formidable design challenges humans have tangled with.
PaPaSteve
1 kW
liveforphysics said:
Mostly spoke with JoeBen Bevirt when he visited Makani circa 2008 ~ 2012
Makani was trying out his early motors ... I think there was cooperation on the controllers. Makani guys were strong in that area.
I did attend the holiday parties at the magnificent Joby timber building a couple times 09 ~ 10 ?
Back then he was also designing a crosswind kite generator not too different from what Makani was doing.
He had permission to a testing site just north of Ana Nuevo which was shared with Makani.
Last time I saw him was maybe 2016 when he stopped in at Otherlab to see Saul.
I do follow Joby progress on insta.
Perhaps you know Josh Land ?
speedmd
10 MW
Looks like they passed the NASA sims.
verticalmag.com
Joby, NASA simulation demonstrates up to 120 air taxi operations per hour in busy airspace
The simulation evaluated how air taxi operations can be integrated into today’s airspace, including at busy airports, using existing air traffic control tools and procedures.
verticalmag.com
speedmd
10 MW
Looks like they are installing chargers at several airports for them now. Interesting looking system.
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