Crosley Engine Specifications

[earthstaraircraft]

Hi
I love to see this kind of discussion here!
The Joby motor I am flying is an out runner out put is 20 kW at 1950 rpm direct drive. Zero 40 kW motor is running at 4200 rpm max.
Electric power is really cool because it is smooth, quiet, and only costs a buck for an hours flight!
Happy flying
Mark

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[rahulchoudhary73]

Yes, thanks once again, Bruce; for the lovely instruction. wonder if you have worked with higher power/weight density motors, like 8kW/kg...

[bruce.markle]

Rahul –

I do have some smaller motors in that range, for example the Plettenberg Predator 37 which works out to 7.7 KW/Kg.

Here are some candidates:



Name

Joby JM1 – 7.3 KW/Kg Peak; 4.8 KW/Kg Continuous

Joby JM2 – 5.2 KW/Kg Peak; 3.5 KW/Kg Continuous

Joby 20 KW - ? (Mark, can you tell us the weight of the Joby 20?)

Joby 30 KW - ? (Mark, can you tell us the weight of the Joby 30?)



Plettenberg Predator 30 – 5.5 KW/Kg Peak

Plettenberg Predator 37 – 7.7 KW/Kg Peak

Plettenberg Predator 50 – 8.0 KW/Kg Peak

Plettenberg Nova 15 – 6.0 KW/Kg Peak

Plettenberg Nova 30 – 6.0 KW/Kg Peak



Flytec HPD10 – 3.4 KW/Kg

Flytec HPD13.5 – 4.0 KW/Kg



(numbers are from the data sheet on the gull forum photo section)

Zero 20KW – 1.5 KW/Kg

Zero 33KW – 2.4 KW/Kg

Zero 40KW – 2.3 KW/Kg



So there are some motors out there that are getting to 8 KW/Kg.



I have toasted a Predator 30 very quickly when operating at these power levels. So motors above arguably 5 KW/Kg are basically little toasters, and you really need A LOT of cooling air to keep them from self destructing. Some of this is pure specmanship, you can maybe pull the higher numbers for 5 or 10 or 30 seconds, but there is a much lower number that you can operate continuously at. I’m guessing you would want to plan on something more in the 2 to 4 KW/Kg range so you have something a little more reliable, unless you are trying to really push the envelope like with Racing, or VTOL flight.



The difference in weight between a 4 KW/Kg and an 8 KW/Kg motor is very small when compared to the aircraft gross weight, but the reliability difference is huge…



Please add data for any others you may know of…



By the way, looking for the weight of the 20 and 30 KW Joby motors ( I have held Mark’s 30; can’t find my notes on the weight…) to add to the list above, I see that there is some new activity on the Joby Motors Blog, which had been inactive for 2 years. Looks like Scott is doing more testing on the JM1 and JM1S. Good to see they are still doing things…



Regards

Bruce

[rahulchoudhary73]

the one i have in mind is yet to be generally avail able (so maybe i shouldn't talk about it yet); though it's been successfully deployed in the tail rotors of bell helicopters, that earlier used the main engine to run the tail as well

[earthstaraircraft]

Joby 20 kW 26 lb
Joby 30 kW. 36 lb. I just re weighed them.
Happy flying
Mark

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[bruce.markle]

Is it this one?



http://www.launchpnt.com/portfolio/tran ... ail-rotor/

[bruce.markle]

Thanks Mark,



So here then would be the Specific Power on the Big Joby’s

Joby 20 KW – 1.7 KW/Kg

Joby 30 KW – 1.83 KW/Kg

A friend of mine, Bob Wilder, who I met 2 weeks ago at an EAA meeting, has purchased a Aerolite 103 and is electrifying it (anybody want a used Rotax 447?). I have asked him to join the Earthstar group. He has extensive RC modelling and aircraft design experience and is an all around really nice guy. He has had some recent correspondence with Joby Motors, the 20 KW is available and costs $5K, still trying to see about the 30 KW. I’m thinking the 20 KW might be a little small for the [draggy] Aerolite, and am suggesting he’s better off adding the 10 lbs and getting the 30 KW. Plus I would rather derate the motor and run the bigger one for reliability.

It would be comparable to the E-Spyder as far as drag (the Aerolite has a shorter wing, and overall probably has an even worse L/D than the E-Spyder) and they advertise a 24KW motor.

Regards

Bruce

[earthstaraircraft]

Now that is really Cool!
Mark

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[earthstaraircraft]

Hi Bruce
I have been talking with him, trying to talk him in to flying it first with the 447 so that if he converts it he will not be a test pilot with no experience in type
One of me friends died in an aero lite thinking it would fly like his thunder gull.
I agree it needs 30 kW or more.
Happy Flying
Mark

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[rahulchoudhary73]

it is based on a principle of concentrating magnetic flux with novel arrangements of magnetics discovered by Klaus Halbach in 1979. (a bit like concentrated solar power in some sense). It made possible linear particle accelerators which have the maximum flux created by man in any machine today at 4.5 Tesla and Maglev trains to begin with. The dual Halbach magnetic arrangement nearly doubles the flux to 1.2 Tesla compared to usual motors which were based on back iron to magnify flux somewhat, but caused more than half the heating problems and losses through eddy currents in the iron. This uses carbon fibre, which how i came across it in the first place, trying to understand why motors use iron at all. they made a small demo for the light aircraft industry folks too a couple of years ago

So the great news is our world is well on its way to get a whole lot better; what i am still coming to terms with is such motors were already technically feasible at least two decades ago...
Rahul