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Electric VioFan
Patent Pending
1.
Fan and Stator design by career "Propulsion Engineer"
Lee Anderson.
2. Very secure and
accurately centered fan rotor retention.
3. Inlet lip is
relieved to accept F/G ducting for smooth airflow
transition.
4. Thin flange to
accept the Mylar tailpipe for smooth airflow transition.
5. Electronic Speed
Control additional cooling air inlet.
6. Streamlined
fairing for exit of E.S.C. throttle and power cables.
7. Motor and E.S.C.
cooling air exhaust.
8. E.S.C. is
located inside the carbon fiber aft center body fairing
for air cooling and no
interruption of airflow (shown
cut-away).
9. Machined
aluminum motor encasement with fins and troughs for
efficient cooling of motor
and provide entrance for E.S.C.
cooling air.
10. The mounting flanges are an
integral part of the injection molded carbon fiber
shroud. For
mounting access
convenience, the flanges are tilted up 5°
from horizontal.
Shock and minute vibration absorbing rubber strips and a
molded clamp enhance the
EVF mounting system.
11.
Injection molded carbon fiber and machined aluminum
construction.
The EVF is manufactured,
assembled, and test run at BVM's Florida facility.
Click on:
EVF System Pricing
For information and pricing
The BVM EVF instructions include additional information about Li-po batteries, proper use of the Thunder Power 1010 charger, and other useful information for anyone interested in electric powered jet models.
Click here to download the instructions.
August Air Testing
  We have had multiple opportunities lately to evaluate the Electric VioFan operation in rather challenging conditions.
A few outings at our Florida field, the Liberty Bell event in Pennsylvania, three days in Maryland, and twice again just recently in Florida were optimum opportunities. Ambient temperatures ranged from 97° in Florida, to 95° in Pennsylvania to a record breaking day of 102° in the Maryland area.
The intense heat and humidity proved more challenging to the human body than to the EVF system. While there is a slight deterioration in fan efficiency compared to a 70°-80° day, there were no issues with the motor or ESC operation.
Since the LiPo batteries are already at 90° or so prior to flight, we found it prudent to deduct 30 seconds from our usual flight time using the 5,000mah cells.
We have discussed flight profiles before and know it takes 10-20 flights to develop a strategy that minimizes the energy consumption. So, with this experience in our pocket, we constantly logged 5 minute flights on the 10S system and 5:30-6 minutes on the 12S system and did not exceed the target 80% battery consumption rule.
Field Charging
always in the shade
At the Liberty Bell event, we shared the use of a Honda generator with the Malchione "E" pilots to power the IOTA converter unit. A pair of BVM Cool Trays definitely helps to shorten the turnaround time. A single Thunder Power 1010C charger and balancer will handle the 10S system while the 12S requires 2 units.
Some Battery Numbers
We did field charge a few times at 1.5C after the "Cool Trays" did their work. It is important to note that the outer cells in the pack will cool faster than an inner cell. This is not an issue with the BVM 5S1P Saddle Cells™ but the 6S1P Saddle Cells™ will require a few minutes for the pack temperature to normalize.
The cycle time in this hot weather is about 1 hour; 15-20 minutes of cooling time and 40-45 minutes of charging time.
Be sure to check that the Saddle Cells™ are within .1 volt of each other after charging and prior to flight. We keep a volt meter handy and always check each pack prior to installing them in the model for the next flight.
If you have multiple sets of Saddle Cells™ it's a good idea to label them such that you can operate them in pairs.
Sometimes there is a stubborn cell or two that requires more time to balance. We have found that if the maximum difference between the cells in a pack is .02 or less, it is ok to fly if the flight profile does not push this pack to the limit.
NOTE: The Thunder Power charger/balancer allows you to read each cell voltage accurately to 3 decimal places.
Slower charging (1/2C) in your shop will allow the balancer to complete its work.
In summary, the BVM EVF products allow you to enjoy high performance electric jet flying in August which is usually hot anywhere in the U.S.A. Just follow the guidelines presented here as you gain some experience.
My thanks to Chris True, and the technical assistance people at Flite Power and Thunder Power for guiding us through this learning process. We will keep passing along this kind of operational info as we continue to gain experience.
Bob Violett
EVF Powered BVM Jets at the '07 Liberty Bell Jet Rally - Electra Jet's, F-86's and the F-16. The blue impulse Sabre and the Thunderbird F-16 were flown by the Malchione "E" team. More on these "reborn D/F models" in a later post.
Dave & Pete Malchione with there EVF F-86.
The Electra Jet with EVF power and a Spektrum radio for guidance are a great combination.
click to read more about Spektrum radio systems
The Electra Jet's (with EVF propulsion) introduction at Florida Jets '07 was impressive. So much so that many of our dyed-in-the-wool turbine customers want to add one to their arsenal of sport jets.
The utter simplicity, quiet operation, model field acceptability, easy transport, and the fact that it flies like its big brother "Bandit" are convincing qualities.
Impressive Performance
It's not a Viper or a Bandit but just the right in between size to absorb the 5+ H.P. we now have available for the EVF. We have learned a few things over the years and the inlet design reflects our experience in that area. The fan, inlet and tailpipe designs must have a determined performance point prior to executing the tooling. We believe that the design point we chose provides an excellent balance between take-off thrust and thrust available at 150mph. Enthusiasts at Florida Jets '07 or other recent flight demo's can attest to the wide envelope of performance of the Electra / EVF combination.
One really has to see it to fully appreciate it, but this video should help.
BVM's tooling processes allow us to produce the EVF with precision and in moderate quantities.
We believe that the flight performance, durability and quality of manufacture of the EVF is unmatched in the industry. In-the-field use will confirm this.
NOTE: The 25C 5,000mah 5S1P Saddle Cells™ from either Thunder Power or FlightPower are identical in cell format and capacity. BVM supports both manufacturers of these excellent Lipo batteries.
Power Usage & Charging
An energy efficient flight routine allows reliable 5 minute flights on the 10S system and 6 minute flights with the 12S system. Start the flight timer at the beginning of the take-off roll and allow 1 min for the landing pattern described below. The total flight time is noted at the end of the landing roll out.
Use full power for high speed fly-by's and zoom climbs. At the top of the climb, shut off the motor, glide down to a comfortable altitude, then use 1/2 throttle to cruise into position for the next maneuver.
Half throttle will produce about 7.5lbs of thrust and consume 36 amps (10S) or 28amps (12S) and about 90mph. Save enough battery energy for a high speed entry into the overhead "Pitch Out" (USAF) or "Break" (NAVY), chop the throttle and zoom into a landing pattern. Program the flaps and gear such that you cross the "Numbers" (approach end of the runway) needing just a little power to land.
It might take a dozen or so flights to get totally familiar with the proper throttle management.
The heli pilots that stay with the 80% rule are getting hundreds of cycles from these 5000mah cells.
For field charging, we set the charger at 5amps (1C) and are able to restore the 3800-4000mah in about 40 minutes. For in-the-shop charging we charge at .8C or 4 amps.
Remember, the batteries must cool down close to ambient temperature before they can be safely charged. The BVM Cool Trays™ greatly reduce the cool down time.
Click here
EVF System Order Form
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