jayseas

I am totally blind when it comes to electrical stuff, so i need some advice.I would like to build a electric C/L Ringmaster Jr. But have no idea on what size motor to use.I don't want to spend alot so so try and keep this in mind when giving your advice.I want the plane to fly at a good clip not real slow, want it fly fast enough to do the stunts.Any and all advice welcome.Would something like this work.

http://cgi.ebay.com/ws/eBayISAPI.dll...AMOTORS%3A1123

mikeainia

My Feedback: (1)

The motor you referenced is similar to what you need, but too small to fly the model you want to get going.

OK - here is the 'e-stuff' I used to get my Grandson's going - the model was an own-design, roughly the same size as RM-Jr.

Motor - Suppo 2217-6 (A brushless, "outrunner" motor)
ESC - Suppo 30 Amp. (The ElectronicSpeedControl - you need this even if you only want to run at one speed)
Battery - 3s1p, 1500 mah LiPo (lithium polymer battery, 3 cells of 1500 mah and at least 15C)
Timer - Will Hubin timer

Assuming you don't know what all that is or where to get it here are two suppliers that have this stuff at reasonable prices:

www.lightflightrc.com
www.bphobbies.com

Email Will Hubin at:
[email protected]

They have the specified motor (though BP Hobbies calls it a BP 2217-6) and the speed controls (Again, BP or Suppo brand - same speed control). The motors are about $20, the ESC's are also about $20.

Both places will also have the batteries - you will want two or three as you cannot 'fast charge' these cells like Nicads. They are available cheaper from some Hong Kong based shippers but you will need to know what you want and how to order it - you will also need a Paypal account for just about all of the above (or a credit card). I can't tell you how much these will cost but roughly $20 each, delivered is a ballpark figure.

The "Timer" is the device that lets us fly these systems control-line and not need an RC receiver/transmitter - in it's most basic form, it turns the motor on for a specified amount of time and then turns it off again. The time is adjustable generally from about 1 minute up to about 7 minutes. Most have some other features and Will Hubin can actually custom program a unit to do exactly what you want it to do. It costs about $20 delivered also. There are other brands but the Hubin Timers use a small screwdriver to set the various parameters, while the others you have to get into "Programming" mode and learn how to set the program to do what you want.

The above system will allow about a 4 minute flight per battery (charge) or as I did to get the boys trained, a couple of shorter flights per battery. There is higher end stuff available, but this is about the minimum as far as expense and performance goes to fly that size plane. The batteries are the real heart of the system and they are getting better and less expensive.

In addition to the above, you will need a "Balancing Charger" for LiPo batteries and some kind of power supply to run it off of - again, you will find it easier to charge batteries at home and take them to the field - fly them - and bring them home to recharge. We have done some field charging, but it is more hassle than it is worth. The chargers are available (for smaller batteries like these) for about $25-$40 but be sure that it is a "Balancing" charger or that you get a separate "Balancer" - this is necessary to protect the batteries. The power supply for the charger should also be available from the same place you get the charger - I know that LightFlight RC and BP both have the chargers and power supplies and usually some kind of package deal.

I realize that the above represents a fairly hefty initial outlay (Somewhere around $150 probably) but once you have the above in hand, you won't need to buy fuel or glow plugs and you will have the power to do basic maneuvers on 52-55 foot lines.

Hope this helps - Feel free to ask any follow-up questions

mikeainia

My Feedback: (1)

Scrounged up a picture of the models I described above - As stated, the wingspan is about 32" - the motor/battery/timer (s) are visible in the pictures. The ESC's are hidden in the wings. By the way, the motors will turn an 8-4 prop at over 11000 RPM on 3 cell batteries so the power is adequate!

jcralley

Mike's advice is on the mark. Here is a similar combination from Hobby King in Hong Kong:

TR2209/26 $16.95
Turnigy 2209 26turn 1130kv 15A Outrunner


Spec.
Kv: 1130rpm/v
Operating Current: 4A ~ 13A
Peak Current: 15A
Suggested prop: 9x4.7
Suggested Battery: 1300~1700mAh 3S1P
Weight: 46g
Dimensions: 27.6 x 28mm
Shaft Size: 3.175mm

Kit includes full accessories, including gold bullet connectors, prop saver, mount, spare rubber rings, shrink tube and screws.

TR_B18
TURNIGY Basic 18A v3.1 Speed Controller

Basic 18A v3.1 Brushless Speed Controller
The Basic series ESC are a very good quality controller. It is designed for customers who dont want alot of fuss and bother in setting up a BESC, who dont need a huge swiss army knife range of features but want something reliable and simple to use.

Cont Current: 18A
Burst Current: 22A
BEC Mode: Linear
BEC : 5v / 2A
Lipo Cells: 2-4
NiMH : 5-12
Weight: 19g
Size: 45x24x11mm


$12.79
User Programmable, both via controller and optional programming card. The programming card is an excellent item as it instantly tells the user the current settings and with a few simple clicks of the buttons, the user can change the settings and have graphical reassurance of those changes.

Z15003S20C $11.25
ZIPPY Flightmax 1500mAh 3S1P 20C

Zippy Flightmax batteries deliver full capacity & discharge as well as being the best value batteries in the hobby market today!

Spec.
Capacity: 1500mAh
Voltage: 3S1P / 3 Cell / 11.1v
Discharge: 20C Constant / 25-30C Burst
Weight: 138g (including wire, plug & shrink wrap)
Dimensions: 100x34x21mm
Balance Plug: JST-XH

APC8x4-E $1.00
APC style propeller 8x4-E

Will Hubin timer:

[email protected]

jayseas

Thanks guy's for your info and advice.When i get something together i will post pictures, might be awhile have home projects going on also.
Thanks again Jim

jayseas

mikeainia, What are the demesions of the plane you are showing here, ws, fuse length.
Thanks Jim

jayseas

Hello guy's would something like this work by just looking at the spec's?I'm trying to get a grasp on what all this means.

http://cgi.ebay.com/RC-Model-3650-KV...d=p3286.c0.m14

mikeainia

My Feedback: (1)

That motor has WAY too high a Kv - without going in to a huge post on permanent magnet motor theory, I will just say that for the model we have been discussing, you want to look for a motor that has a Kv of 1200-1500. The motor that I described is 1500, but you can get it in other - lower - Kv's. One of our club members bought the same motor but the 2217-7 model which has a Kv of 1200 - his motor will need a somewhat larger prop to get the same amount of power, but will draw slightly less current. <By the way, I would personally stay away from the Hong Kong dropshippers that advertise heavily on Ebay - they don't know what they are selling and can't support it. I have bought (accidentally won, really) a LiPo battery from the very 'store' you pointed to. The battery was TOTALLY worthless - described as a 20C, 4000 mah battery it would run a motor with a very small prop for about 30 seconds at an unflyably low RPM, then the voltage would sag to almost zero and it would be uncomfortably hot. The shipping to return it would be about what I paid for it, so it is basically a paper weight. Even throwing it away is more effort than it is worth, so it sits on a book shelf in my shop.> If you MUST use a Hong Kong supplier, HobbyCity/HobbyKing is good, but the shipping costs are high enough that much of the savings disappear. Our local hobby shop is now a HobbyKing dealer, and has many of the items that they supply right here in town. His prices are reasonable and I buy what I can from him. I have dealt with both LightflightRC and BP Hobbies and I can recommend them. They don't always have the items in stock, but neither does Hobby King.

When choosing or evaluating a motor, I look at the weight of the motor and the Kv. The weight is mostly the metal and the copper windings, so it gives you a general idea of the amount of power the motor can handle. The Kv will give you an idea of the prop and batteries that will perform in the range you want it to.

The 2217-xx motors weigh 80 grams and as I said, a Kv of 1500 will turn an 8-4 at about 11000 RPM, drawing about 20 amps. On the 1500 mah batteries I mentioned, this will get you about 4 minutes of useable flying time.

I have another model with 'the next larger' size motor - a 2814-6. This motor has a Kv of about 1400 and weighs about 100 grams. This motor will turn a 9-6 at over 12000 RPM, drawing about 30 amps. On the 1500 mah batteries, this would only equate to roughly 3 minutes of flying time, so I run it on 2200 mah batteries (about 30% 'more fuel'). This then gets me back over 4 minutes of flying time.
Again - the weight of the motor is 30-40 percent more than the 2217, so it will handle 30-40 percent more power.

There really isn't any magic or secret formula's - once you have flown something, you will have a much better idea of what results come from the various things you can change. Frankly, these motors/esc's are VERY easy to adapt to changes. If you want to run a larger prop on the same battery, you will get less RPM but more power (up to a point). If you can't quite get it to pull through a wingover, go to a slightly larger prop (yes, larger! - or more pitch) and you will really feel the difference. If your speed is slightly too high for a comfortable stunt pattern, you can dial it down by way of the power setting from the timer. In fact, when you really get into it, you will want to fly at less than full-power, so that your timer or ESC can adjust for a sagging battery voltage as the flight progresses.

The best forum on electric C/L, IMHO, is at Stunthanger.com. You will need to register using your real name, but don't let that scare you away - no spambots or virus carriers will find you because of that. Then you can read the electric forum where people have listed very detailed descriptions of just what equipment they use on various planes. Very interesting threads on everything from airframe to propellers. An education in itself.

The TnT-3's that I posted are about 32" span and maybe 250 sq. in. I can measure them when I get home from work tonight. I was originally building them for glow .15-.19 's, but got into this electric stuff and decided that they would make better trainers for the boys as electrics - for various reasons, they were very successful. Those are 8" props in the pix, if it helps you to visualize their size. They are foam wings with external bellcranks. Originally were to be tricycle gear, but came out a little too tail-heavy so I swung the mains around and mounted them on the front - instant tail-dragger that balanced correctly. <Both boys solo'd on their 2nd flight>

I suppose I better get back to work ....

jayseas

Thanks for responding, I have some c/l scratch built planes i fly one is a 32" w/s with a fox .15 that uses a 8x4 prop.Just wanted to know size of plane you posted to compare to this c/l .15 powered i fly.

You say that the latest motor i posted is to big, you say to look for a 1100 to 1500 kv.I'm alittle confused now, my original posted i ask about a motor with 2200kv and was told it was to small for the aplication i was wanting to use it for.Confused

mikeainia

My Feedback: (1)

Kv doesn't have anything to do with physical size of the motor - that is why I also look at the weight of the motor. Kv has to do with the magnet strength and the actual windings.

The original motor you posted weighed about 50 g. and had a Kv of 2200 - that is the exact same motor that I use on my 1/2a size stunter, which is about 30" span and weighs about 13 oz. ready to fly. It turns a 6-4 prop at about 12000 RPM on TWO cells instead of the 3-cell batteries I mentioned above. It draws about 12 amps. The latest that you posted is the same diameter and a little longer - I am guessing that it would weigh about 65 grams but that very high (3650) Kv - means that it is likely wound to use in a helicopter, where they typically have a gear driven rotor. In our direct-drive c/l planes, even a little 5-2 or 5-3 prop would be drawing 40 or more amps and the ESC shown (a 30 Amp rated one) would burn up unless the motor burned up first!

The motor that I listed first - weighs about 80 g. and has a Kv of 1500 - turns an 8-4 at 11000 as stated, drawing about 20 amps. The planes weigh about 24 oz. RTF, and about 250 sq. (ie: about .15-19 size). I also mentioned a sister to that motor that has a Kv of 1200, but the motor still weighs about 80 g. It would fly the same plane but the 8-4 would turn less than 11000 (on the same battery) - you would need to move up to an 8-6 or 9-3 or 9-4 - It would turn any of those about 10000, probably but the power out would be about the same.

Then I mentioned a 2814-6 with a weight of 100 g. and a Kv of 1400 - turning 9-4's to 9-6's at about 30 amp.

Note - the weights are going up, the Kv's are different but not related to weight. The CURRENT draws are also going up because the power handling capabilities of the motor (due to it's increased weight) also goes up.

(All of the above setups mentioned 3 cell batteries - just like in a flashlight, the batteries add up in voltage so 1 cell is about 3.5 volts, 2 cells ~ 7.0 volts, 3 cells ~ 10.5 volts, etc.). Power is voltage multiplied by current. Voltage is about 10.5, current in my TnT is about 20 Amps so power is ~210 Watts. Current in the 2814-6 is about 30 Amp - so power is about 300-315 Watts.

The "Rule of Thumb" is for aerobatic performance, you want about 125-150 Watts per pound of Plane Weight. My 24 oz (1.5 lb.) models would be pretty aerobatic at 175-225 Watts. They will fly around in trainer mode at say 125 Watts but not be capable of much in the way of aerobatics. And your original motor question is flying on 2 cells (7 volts) at about 12 amps, so 85 watts. It is less than a pound - call it .75 lb. so we would (ideally) be at about 90 watts (125 W. per pound).

Oh, and one final question for you - You DID mean the Ringmaster JUNIOR, didn't you? The .15-19 size plane? If you meant the Baby or 1/2A size, then your original motor would work pretty well.

mikeainia

My Feedback: (1)

Just measured one of the planes -

Span - 32"
Root - ~ 9"
Tip - ~ 7"
Length - 23"
Weight - 22.5 oz.
(Ready to fly, with
battery installed)

I'm guessing that these are a little larger than a RM - Jr, though the power package would be fine on either.