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Revolt electric paramotor


jjooeehunt1985
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Yeah, I'm not hot on their marketing angle of "this is a revolution in commuting!" Uh, no. No no no no no. When I talk to laypersons about PPG I get the same questions like "can I take off from my backyard?" "Can I fly to work?" "I can just fly around inside the city right?" "I can avoid rush hour traffic!" and I have to burst their numerous bubbles. 

I understand their desire to drum up interest from an audience that doesn't know anything about flying, but this may not be the best way to do it.

As for the actual mechanics, the only real thing holding it back is battery tech. Tesla recently declared an increase in range of their cars, but it was due to simply re-arranging the cells of the battery to fit more into the same space, not from an advancement in battery chemistry. I think perhaps lithium ion chemistry can't get much better, but other chemistries probably have more potential.

- A quadcopter with a broken prop or engine will still experience twisting and torque which software can try to manage. I'm not sure how advanced this company's software and sensor tech is should motor failures or prop failures occur in flight, but some drone companies seem to have this controlled to some degree. This is in comparison to something like an octocopter, or even better, one with a coaxial design, which more or less just experiences a loss of thrust in the event of a single motor or prop failure.

- Petrol engines, by virtue of being a heat engine, can only be ~65% efficient, AT MOST. Electric motors are about 95%. But again you have the energy density issue. Efficiency doesn't solve all the ills if the energy density of batteries simply isn't in the same league as chemical bonds.

- Batteries also carry around all their "fuel" all the time (ex. the Lithium, which simply moves between the anode and the cathode via the separator). The matter inside petrol gets combusted and released into the atmosphere (bad!) so the paramotor loses mass and weight to the outside world during flight. A battery does not. Your (heavy) launching weight is the same as your in-flight weight as is your landing weight.

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flight times are I expect as questionable and electric cars.

Take a decent electric car 250 miles at cruise is easily dropped to 150 or less with your foot down. Renault Twizzy on factory settings 30 miles, unleash its full power and you'll get 5 miles.

40 mins flight time on the biggest battery. Interesting but missing a few vital facts. How big a wing was the tiny 55kg pilot using ;) (I'm just speculating) Lets say at a constant 30kg thrust it gives 40 mins autonomy to be fair.

70kg thrust or I have heard 90kg is possible. Either way a few mins at 70 or 90kg will reduce the rest of the flight from 40 mins to 20 mins or less.

This is the real issue with electric, I have a leccy bike. To be effective you either need to be constantly mindful of your power inputs or need double the battery capacity you expect. Battery capacity is our current drawback till future improvements. 

Then I have a problem, 18kg paramotor with fuel for 3 hours is 25kg. Why then would I want to fly a 30kg machine for 40 mins. My 18kg machine with fuel for 45mins is still under 20kg. I can refuel and go again. 

 

Electric PPG, I hope so, one day, not yet though.

 

 

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I'm not sure that the perceived reliability of electric machines will survive the level of battery development required.

The battery is an energy store, like a fuel tank. In the IC engines fuel tank, we keep petrol, which is about 1/16 of the weight of the fuel/air mix which is burnt to produce power. The battery contains all of the fuel for an electric motor. In this way, it is more akin to the fuel tank of a rocket motor, with the potential to release all its energy in an uncontrolled manner. As the energy density of batteries increases, so will the potential for catastrophic failure and the requirement for mechanisms to prevent that failure. These mechanisms will be required to 'fail safe', will add complexity and will inevitably impact reliability.

Edit: I've just had a look at the Revolt kickstart appeal. There are some truly outrageous claims on there and with 15 days to go, they've only convinced 100 punters and raised 25% of their target.

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Put a small chute on it. At the end of the day it's little different to me chucking my non-steerable reserve. Except as you say it would be a small inescapable ball of lithium fuelled destruction. :-)

Oh also, I was looking at your Radial Engine project - totally amazing, any updates you can add to the thread ?

Edited by Hodders
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