shd3920

What motor combo is best suited for the 46" wingspan Hobby Shack Real Thing?
I prefer a brushed setup so could someone hook me up with a motor, gearbox and ESC combo?
They need to be reasonably priced, perhaps from Hobbyking. And need to be compatible with a JR radio system (Max6 single conversion, positive shift)

Please include the links to suggested electronics.

Thank you;
Steve

aeajr

My Feedback: (2)

Why would you prefer a brushed set-up? Nobody puts in brushed systems anymore. That would be like putting an hand crank on your car.

Please include link to info about your airplane.

shd3920

This airplane is a 1970s kit and info links can not be located. Here is the only info I have.

• The Real Thing by Hobby Shack
• 46 inch wingspan
• 319 sq in wing area
• .049-.10 engines or electric conversion
• 2 or 3 channels-elevator, rudder and throttle

I am not firm on the brushed motor setup if anyone can point me in the right direction for a good brushless setup.

aeajr

My Feedback: (2)

Any idea about the all up weight?

shd3920

No more than 50 or 60 ounces I'd guess, but I see no mention of it in any details.

aeajr

My Feedback: (2)

OK, that helps.

The best way to size electric power is by watts/pound. So a 60 ounce target is about 4 pounds.

Depending on what kind of performance you want we then target

75 watts/pound - typical scale flight
100 watts/pound - Average sport aerobatics
150 watts/pound - Aggressive aerobatics and strong up-line
200+ watt/pound - 3D and all out pattern.

What is your target?

Next is amout of space in the engine area. you would probably want to use a motor in the 35 to 50 mm size range. What will fit?

Next is prop size - If you are going to fly this off a runway, what is the largest prop that will work or that looks right on the plane, if you are looking for a specific appearance.

There are a variety of calculators available that can help pick motors. This is the one from Electrifly and one that I find very useful.
http://www.electrifly.com/powersyste...tem-index.html

We are going to look at the Rimfire motor recommendations.
http://www.electrifly.com/config/index.php

We will use 4 pounds (64 ounces) Naturally you can change this.
I set a 10" span prop maximum - you can change this which may change other things.
I selected aerobatic for performance
The system is recommending an 18.5V 5S battery

This is what it suggested - 144 watts/pound
42 MM motor - will this fit in the engine compartment?

Flight times can be increased by reducing the throttle or by using two battery packs connected in parallel. Please note that the weight of the motor mount is not included in the system weight. The weight of the different mounts can be found on the ElectriFly web site.

shd3920

Typical flight, so something around 300 watts. Around 1200-1500 KV would you say???

aeajr

My Feedback: (2)

I changed the selection to 55 ounces
Flight type to sport
Prop is still at 10" max
Battery recommendation came back at 3S 11.1V

Now we get a 35 mm motor and 114 watts/pound - good sport recommendation.


Flight times can be increased by reducing the throttle or by using two battery packs connected in parallel. Please note that the weight of the motor mount is not included in the system weight. The weight of the different mounts can be found on the ElectriFly web site.

aeajr

My Feedback: (2)

Just examples but I have found the rimfire motors to be very good. Even if you don't care for Rimfire motors for some reason you can use the specs to go hunting for other brands, but Rimfire is a good one.

aeajr

My Feedback: (2)

Changed weight to 50 oz and this time selected 4S pack. new recommendation.

[h=2]Motor Recommendations[/h][TABLE]
[TR]
[TH] [/TH]
[TH]Best Combination[/TH]
[TH] [/TH]
[/TR]
[TR]
[TD="align: right"]Performance[/TD]
[TD]Sport[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Motor[/TD]
[TD]35-30-950 / GPMG4590[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Gear Ratio[/TD]
[TD]N/A [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Gear Drive[/TD]
[TD]Not Required [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Propeller[/TD]
[TD]10x5 in., Electric[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Battery[/TD]
[TD]2100 mAh, 14.8v [/TD]
[TD]Increase

Decrease
[/TD]
[/TR]
[TR]
[TD="align: right"]ESC[/TD]
[TD]SS-35 / GPMM1830[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]ESC Motor Adapter[/TD]
[TD]Not Required [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Motor Mount[/TD]
[TD]Medium / GPMP1255 [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Current Draw[/TD]
[TD]22 amps[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Approximate Speed[/TD]
[TD]45 mph[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Approximate Thrust[/TD]
[TD]35 oz.[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Weight of Power System[/TD]
[TD]12.03 oz.[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Approximate Flight Time at Full Throttle[/TD]
[TD]5 minutes[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="align: right"]Watts per Pound[/TD]
[TD]104.32 [/TD]
[/TR]
[/TABLE]

shd3920

I will not be doing sport, only typical beginner flying. There is no nose cowl pieces for this plane, just a flat firewall surface.
Max prop size according to plans would accommodate no bigger than 7".
According to the calculator you provided and these specs I put in (lower weight to 2 lbs by mods, 7" prop, trainer, and 11.1volts) this is the specs it came up with.

[TABLE]
[TR]
[TH][/TH]
[TH]Best Speed Setup[/TH]
[TH]Best Thrust Setup[/TH]
[TH]Best Combination[/TH]
[TH][/TH]
[/TR]
[TR]
[TD="align: right"]Performance[/TD]
[TD="colspan: 3, align: center"]Trainer[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Motor[/TD]
[TD]28-26-1600 / GPMG4535[/TD]
[TD]28-30-1450 / GPMG4570[/TD]
[TD]28-30-1450 / GPMG4570[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Gear Ratio[/TD]
[TD]N/A[/TD]
[TD]N/A[/TD]
[TD]N/A[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Gear Drive[/TD]
[TD]Not Required[/TD]
[TD]Not Required[/TD]
[TD]Not Required[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Propeller[/TD]
[TD]7x4 in., Slow Fly[/TD]
[TD]7x4 in., Slow Fly[/TD]
[TD]7x4 in., Slow Fly[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Battery[/TD]
[TD]1250 mAh, 11.1v[/TD]
[TD]1250 mAh, 11.1v[/TD]
[TD]1250 mAh, 11.1v[/TD]
[TD]Increase
[/TD]
[/TR]
[TR]
[TD="align: right"]ESC[/TD]
[TD]SS-25 / GPMM1820[/TD]
[TD]SS-25 / GPMM1820[/TD]
[TD]SS-25 / GPMM1820[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]ESC Motor Adapter[/TD]
[TD]Not Required[/TD]
[TD]GPMM3122[/TD]
[TD]GPMM3122[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Motor Mount[/TD]
[TD]Small / GPMP1250[/TD]
[TD]Small / GPMP1250[/TD]
[TD]Small / GPMP1250[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Current Draw[/TD]
[TD]17 amps[/TD]
[TD]17 amps[/TD]
[TD]17 amps[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Approximate Speed[/TD]
[TD]51 mph[/TD]
[TD]51 mph[/TD]
[TD]51 mph[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Approximate Thrust[/TD]
[TD]18 oz.[/TD]
[TD]18.3 oz.[/TD]
[TD]18.3 oz.[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Weight of Power System[/TD]
[TD]5.12 oz.[/TD]
[TD]6.72 oz.[/TD]
[TD]6.72 oz.[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Approximate Flight Time at Full Throttle[/TD]
[TD]4 minutes[/TD]
[TD]4 minutes[/TD]
[TD]4 minutes[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]Watts per Pound[/TD]
[TD]94.5[/TD]
[TD]94.5[/TD]
[TD]94.5[/TD]
[/TR]
[/TABLE]

With the motor suggested (link below) the maximum weight of the model should be between 2.5-3.4lbs
That is doable with building mods. Please let me know if something is inaccurate or otherwise wrong. Thank you for your help.

http://www.philshobbyshop.com/catalo...u?sku=GPMG4570

bhorton

My Feedback: (26)

I built 2 Real Things years ago. To give some info on how much a Real Thing weighs. One of mine had a heavy HP .21 4-cycle engine and weighed 46 oz. The other one had a Irving .20 2-cycle and weighed 40oz. Here are some pics of mine.

shd3920

Those weights are WITH the motors? What were the weights without (bare skeleton?) I guess I was way off with the weight. But its hard to guess the weight when nothing is mentioned in the specs.

bhorton

My Feedback: (26)

Yes those weights are with the engines. I don't have a weight for the planes without the engines. The HP .21 4-cycle instruction manual shows the weight as 300 grams or about 10.6 oz. That would put the weight of the plane at about 35.4 oz without the engine but including the weight of the motor mount and fuel tank. I would guess an electric setup would weigh 2lbs or less.

shd3920

That is a beauty of a plane horton. Looks like you did not use the stock landing gear (the ones that lay flat across the fuselage) and used your own to lift the fuselage front up more.

I do not like that with these motors, after a full 4-6 hour charge, all you get is 4 minute fly time. Any way to better that?

rgburrill

Single conversion? Can single conversion transmitters still be used?

aeajr

My Feedback: (2)

The weight that is needed for the calculators is all up, ready to fly weight. So the numbers provided by bhorton are very useful. Empty frame weight is not helpful in the calculations. We need to size according to what the aircraft will weigh ready to fly.

So he says between 40 and 46 ounces. Hopefully that includes fuel. That is a good target range.

aeajr

My Feedback: (2)

That is a good weight range. That motor seems to be a good fit for this plane given the additional information you have provided. Good fit! I would probably go to a 1600 - 2000 mah battery for a little more duration.

Mike06659

Park 480 & 30amp esc. Done! Couple of 2100mah lipos and fly all day
http://www.hobbyking.com/hobbyking/s...ner_850kv.html
http://www.hobbyking.com/hobbyking/s...ontroller.html

Mike

shd3920

The minimum size prop for that motor is 9. The max this plane can take is 7. A 7 would not work for this motor.

Mike06659

Extend the gear slightly which will give you the clearance needed and it will also help during grass field operation. The power and flight times would be well worth the 10min landing gear upgrade.

shd3920

It would need to be extended by about 3/4 inch. The only gears I have will raise it by 2 inches. I think that would be too much. and I would like to keep it looking as stock as possible. To keep the kit looking stock and still raising it couldn't I put 4 inch or even 4 1/2 inch wheels on it instead of the required 3 inch? That would raise it by 1/2" thus giving it just enough room for a 9" prop. Or would that look too stupid?

The other suggested motor (Rimfire) is 1450KV. The Hobbyking one is only 850. Will that difference matter much?

Mike06659

Longer flight times would probably be the only difference. 1/2-to 3/4 of an inch sounds like it would be in the ballpark. Take into consideration the height of the tail-wheel because that will also determine the stance. Honestly, there are a million combinations for these old airframes with today's technology. All the above will probably work fine.

shd3920

The higher the KV the longer the flight time?

bhorton

My Feedback: (26)

I didn't use the stock landing gear because the planes would not take off with the bottom of the fuse dragging in the grass. Unless the grass is very short the fuse almost holds the wheels off the ground. I made more conventional landing gear and flew them with it until I sold them.