Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: Electric motor?

  1. #1

    Join Date
    Aug 2019
    Location
    Tahoe City, CA
    Posts
    5

    Question Electric motor?

    I was wondering if anyone had put an electric motor in a Kitfox?
    I was thinking that it could work well in a Kitfox since it would be lighter, require much less maintenance, be less susceptible to mechanical failure and could offer enough range for average use.
    I am not a pilot but have been intrigued by the Kitfox as a simple, fun aircraft and this might motivate me to try to build one. In reading this forum, it seems that the major problems with flying the Kitfox are due to the engine. Lots of problems there. Electric motors are very simple and very reliable. Same for the batteries and control systems.
    An 80 to 100 HP electric motor would weigh 100 to 150 pounds and batteries are about 50 pounds per 5 kWh storage it seems to me replacing the motor, cooling system fuel tanks and fuel weight with an electric system could result in a lighter aircraft. Electric motors, of course, don't suffer loss of efficiency with altitude. They also have nearly constant torque over their entire speed range.
    So, is this idea crazy?

  2. #2
    Senior Member PapuaPilot's Avatar
    Join Date
    Nov 2013
    Location
    Nampa, Idaho
    Posts
    1,225

    Default Re: Electric motor?

    No, it's not a crazy idea. You are correct in wanting to find a light airframe like the Kitfox to convert to electric. Siemens already has a 120HP electric motor that only weighs 57 pounds, which is being tested on the Sun Flyer 2 all electric aircraft. The biggest challenge for any electric aircraft will be batteries and getting enough energy density to be able to fly for an acceptable amount of time.
    Last edited by PapuaPilot; 08-03-2019 at 04:17 PM.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  3. #3
    Senior Member rv9ralph's Avatar
    Join Date
    Aug 2014
    Location
    Greenleaf, ID
    Posts
    618

    Default Re: Electric motor?

    It looks good on paper. However... the Pipestrel Electric program for flight training in Fresno, CA is a place to look for practicality. The program manager for this endeavor spoke to an EAA meeting I attended about the program. The details are the issue. 45 to 90 minute flight times with reserves, then need to recharge (must have a charging station at the destination airport to charge for return flight.) The battery unit replacement/spare is $70K. Even though you don't need fuel, as fuel burns off the aircraft gets lighter and performs better... batteries stay the same weight regardless of charge level.

    Electric flight is possible eventually, but I don't think it's time is right yet. At least for practical use.

    Ralph

  4. #4

    Join Date
    Aug 2019
    Location
    Tahoe City, CA
    Posts
    5

    Default Re: Electric motor?

    Interesting to hear about the Fresno experience with the Pipistrel.
    I looked at the Pipistrel Alpha Electro. It's also a light two seater frame and focused on flight training since the cost to operate is just a couple of dollars an hour for electricity.
    They use a 50 kW electric motor (about 65 hp) with 106 kg of Tesla style (18650) batteries which should give them about 25 kWh of power. They state an hour of flight time with 20 min reserve. (They also say they can regenerate up to 13% of the power when descending)
    You can buy Tesla battery packs for about $1300/5.3 kWh so about $6500 for 26 kWh batteries. Electric motor would be $3000 to $5000 plus controller.

    As far as "range" goes, just like with electric cars, it depends on your use. I believe that most flying in this type of airplane is short distance, short duration. I saw a survey that that found most pilots for these light sport aircraft fly less than an hour at a time. Cross country travel (to Oshkosh!) would require frequent stops for charging. Pipistrel says an hour of charging for an hour of flying... so this would be slow.

  5. #5
    Senior Member efwd's Avatar
    Join Date
    Jun 2015
    Location
    Yorba Linda, CA
    Posts
    2,817

    Default Re: Electric motor?

    Don't forget the reserve.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  6. #6

    Join Date
    Aug 2019
    Location
    Tahoe City, CA
    Posts
    5

    Default Re: Electric motor?

    I was thinking that most electric motors wouldn't be designed to withstand the large lateral and horizontal push pull forces from having a propeller attached. It probably would be best to have a gear mechanism that was designed for these forces which would have as an input the motor shaft. I've looked at governors which are designed for these forces but seem very complicated and do know that a governor is needed. A front gearbox would be good. Do these exist as a 1:1 gearing? I don't think any speed reduction is necessary.

  7. #7

    Join Date
    Jan 2020
    Location
    Portland, Oregon
    Posts
    4

    Default Re: Electric motor?

    Quote Originally Posted by efwd View Post
    Don't forget the reserve.
    What about the idea of a hybrid? Light weight ~80hp gasoline engine generator, small battery bank as a buffer, used Tesla motor to drive the prop?

  8. #8

    Join Date
    Aug 2019
    Location
    Tahoe City, CA
    Posts
    5

    Default Re: Electric motor?

    Using the specs from the Pipistrel which has a 65 hp motor and 25 kWh of batteries, you could probably get by with a much smaller generator. If you consider that most of the battery drain and power would be used in gaining altitude, you could probably get by with a 20 hp or so generator (10 to 15 kW). The battery would provide most of the power when climbing and the generator could top off the battery when cruising. Also have the potential to regen the battery when descending.
    Also, could probably get by with a 65 hp or so electric motor. Much smaller than a Tesla motor.

  9. #9
    Senior Member Dorsal's Avatar
    Join Date
    Sep 2008
    Location
    Central, MA
    Posts
    1,511

    Default Re: Electric motor?

    Quote Originally Posted by mspohr View Post
    Interesting to hear about the Fresno experience with the Pipistrel.
    I looked at the Pipistrel Alpha Electro. It's also a light two seater frame and focused on flight training since the cost to operate is just a couple of dollars an hour for electricity.
    They use a 50 kW electric motor (about 65 hp) with 106 kg of Tesla style (18650) batteries which should give them about 25 kWh of power. They state an hour of flight time with 20 min reserve. (They also say they can regenerate up to 13% of the power when descending)
    You can buy Tesla battery packs for about $1300/5.3 kWh so about $6500 for 26 kWh batteries. Electric motor would be $3000 to $5000 plus controller.

    As far as "range" goes, just like with electric cars, it depends on your use. I believe that most flying in this type of airplane is short distance, short duration. I saw a survey that that found most pilots for these light sport aircraft fly less than an hour at a time. Cross country travel (to Oshkosh!) would require frequent stops for charging. Pipistrel says an hour of charging for an hour of flying... so this would be slow.
    I think it is an issue of range. It is fairly typical to cruise at 75% power (very different than car), not sure how you get more than about 30-45 min flight time from the example above. While it maybe true that many flights are less than an hour I can't imagine owning a plane with that fundamental limitation. As others have stated it is getting closer but not there yet in my opinion. One place this does work is small booster motors for motogliders.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  10. #10

    Join Date
    Aug 2019
    Location
    Tahoe City, CA
    Posts
    5

    Default Re: Electric motor?

    I was just wondering... what is the range of the Kitfox with a Rotax or similar engine?
    Fuel consumption gal or pounds per hour?

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •