Converting a gas .45 trainer to electric
I want to convert a fixed tricycle (nose wheel) trainer that has aluminum tubing fuselage and plastic wings (similar to corrugated cardboard but plastic) about 130 cms wingspan. Weights about 2.7 lbs without .45 cc gas engine. What is the recommended e-engine, ESC, battery, and prop for the conversion to work?
I might have to convert it to a tail-wheeler
Thank you for suggestions
I assume you mean a GLOW engine of 45 size (7.5cc) ?
Simple .... check out Hobby King or any other general online site for 45 - 50 equivalent E-motors ... and the specs.
Direct swap in ..
60A ESC, 4 - 5S LiPo, ~13 - 15" prop ...
Personally I would be using a 5S pack and a 12" prop as a 45 Glow is actually not usually a big prop motor. The glow motor would probably be turning about 10,000 rpm on a 11x7 prop ? So you need to use at least 5S on the E-Motor...
A 60 sized motor if you want to be sure of enough power :
Needs 5 - 7S and 60A ESC, 14 - 17" prop.
Probably too much as the prop to load the motor is too big.
I've purchased a Hyperion motor that is very good quality, for reasonable price. The battery pack is a five cell A123 pack, or a good quality 2500-3500 four cell LiPo pack. The model is a 3D Hobby Shop Vyper, with 48 inch wingspan, 505 square inches, and 37 ounces without motor/battery/esc. Total flying weight is 57 ounces.
That Hyperion motor turns a 13X6.5 APC-E electric prop at 8300 RPM, pulling 40 Amps and 590 watts. That turns into 165 Watts per pound. Take off runs are 10-20 feet, and it will climb out vertical out of sight.
The only problem with this model is, when using full aileron control, that danged thing rotates 3-4 times per second, so I've got the 'triple rates' set to 50%, 80%, and 100% with lots of expo.
Here is the posting on that $49 Hyperion motor.
And, this is the Hyperion motor that I bought for $49.00
And, the model this motor went into:
EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
Calculators can be useful and convenient. Many motor makers provide them and there are general ones like Electricalc.
I often use this one as a first reference:
Once you start working with electrics you discover that saying what is the equivalent of a .45 you come to understand that that is the wrong question. The right one is what power to weight ratio do you want.
Planes will fly at 50 watts/pound and 75 is good for a trainer, slow fly or a glider. Most glow pilots are happy around 100 watts/pound.
Using this calculator for the Rimfire motors, you start with the weight and just fill in the blanks.
Guessing max prop size at 11" and a 4S lipo pack I get this:
Best Combination PerformanceSport Motor35-30-950 / GPMG4590 Gear RatioN/A Gear DriveNot Required Propeller10x5 in., Electric Battery1500 mAh, 14.8v
ESCSS-35 / GPMM1830 ESC Motor AdapterNot Required Motor MountMedium / GPMP1255 Current Draw22 amps Approximate Speed45 mph Approximate Thrust35 oz. Weight of Power System9.33 oz. Approximate Flight Time at Full Throttle3.6 minutes Watts per Pound120.74
Depending on the space in the plane you would probably use a 4S pack around 3000 mah.
Typically the biggest 2 problems converting a glow trainer to electric are:
CG and battery access.
finding an appropriate motor and ESC is pretty easy. www.nitroplanes.com Search for Tacon and you'll find they have a .40 glow equivilent. The Dynam/Detrum ESCs are fine. I'd get a 60 amp since its not much more than the 40 amp (which would probably be enough) and gives room for a bigger motor later.
(There are MANY sources for appropriate motors, ESCs and batteries)
Sky LiPo 20C 4000 mah 4S would be plenty and easily fit in most .40 class trainers.
For battery access I would cut in a hatch over where the glow expects the fuel tank to go. This is generally the best place for the battery when doing a trainer conversion.
The electric motor will weigh less than half as much as the glow engine it is replacing. Expect to need to add weight to the nose of the airplane. The plane will still have higher performance capability on the electric than it had with a glow engine.
I've got a Redwing Models MXS-R that was electricuted last October. This model is designed for a 30 cc gasser. Electric power is a Hacker A60-5S motor, and 10S2P A123 cells.
This model came out real tail heavy, until the two 5S2P A123 battery packs were moved as far forward as they would go. Nice thing about A123's, they can be left in the model, and charged in the model. Had the model been equipped with LiPos, it would have required lead in the nose.
This model has a dozen flights on it so far, and am waiting for decent weather to get it back in the air again this year.
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