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Hey there folks! New poster with some engine questions

Old 02-16-2009, 09:53 PM
  #1  
KrunkSplein
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Talking Hey there folks! New poster with some engine questions

Hey everybody! It's been a busy year so far, so lemme get you up to speed:

-I got a HobbyZone SuperCub for Christmas
-I had horrible interference issues, so I upgraded to a 6-channel RX/TX setup with new servos, a new ESC, and some tape reinforcement where appropriate
-Flew fantastically for a few weeks

At the same time, my Dad began getting into the hobby, going with a great balsa trainer (whose name escapes me - upper wing, ailerons, glo powered). When we would go down to the field, I would also fly this plane.

At this point I intended on upgrading the Cub to a brushless motor/esc, but I instead talked myself into getting a new plane.

I sort of jumped a few steps ahead and went with a Mini Super Sportster from GreatPlanes. Everything purchased was what had been recommended, except I went for a LiPo with a greater mAH rating at a lower weight.

I've flown the sportster twice now, and absolutely love it. I'm still relatively new to all of this, so I keep it flying a few 'mistakes' high just to be safe. One thing I noticed is that I botched the assembly of one of the ailerons - there isn't quite enough distance between the control surface and the wing itself. So what happens is that after a right turn, the plane will tend to veer right until I move the ailerons to the left (which unsticks the control surface). That being the case, I went to Tower Hobbies with the intent of getting:
a) a new wing
b) a second battery
c) my own charger/balancer setup so that I don't keep having to borrow my Dad's

There are two other things I have been considering as well, which is why I need your guidance. The easiest modification I have planned is the addition of a tail wheel. It doesn't even have to be steerable, I just want something small to make landings a bit easier. Can anyone recommend any walkthroughs or threads discussing this sort of modification?

Secondly, and this is not urgent by any means, is an upgrade to the motor. As it stands, it uses a 400-size brushed motor and a preassembled 2.4:1 ball-bearing gear box. It comes with a prop adapter as well, with the stock prop being 10x4.5. This is not something I intend to do right away, but I do intend to begin research into the process of upgrading now. I am a total neophyte when it comes to the installation of electric motors and mounts. I have a masters degree in Electrical and Computer Engineering, so I understand how the motor works, just not how the mounting is handled. For example, I believe the stock motor/mount combo has a slight downward & rightward tilt. I have no idea why this is the case, nor do I understand how I would replicate this if I went to a brushless motor. Any advice here would be much obliged.

Sorry there aren't any links to the plane or parts in question, but this is my first post so it won't let me add them.

Thanks a ton!
Rob
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Old 02-16-2009, 09:58 PM
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Figure.N9ne
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i dont really have any advice for the motor, but where is the aileron binding? it is just on the inside against the wing? you cant trim it down a bit to stop the binding? its a shame to spend money on a whole new wing if you dont have to
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Old 02-16-2009, 10:27 PM
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birdDog
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I agree with Yaniel, you should be able to save the wing and use the money for MORE BATTERIES!!!!!
Can you post a pic of the bind?

About the motor, try looking around at http://www.headsuprc.com/servlet/StoreFront, He's got a TON of info on every motor he sells. You should be able to come up with a perfect match for your weight of plane, batteries you own and flying style. You will need a brushless ESC as well. $2 shipping!

WOW! He's got an even cooler page!!!!! http://www.geocities.com/jefforyr/bmguide.html
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Old 02-18-2009, 08:08 PM
  #4  
KrunkSplein
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Okay, I did my research and found a common replacement engine used when upgrading my Mini Super Sportster to a Brushless motor.

Here's the plane itself: http://www3.towerhobbies.com/cgi-bin...?&I=LXHSR6&P=0

Unfortunately, there isn't a lot of information regarding the stock motor of the plane, but here's the link anyway:
Motor: http://www3.towerhobbies.com/cgi-bin...?&I=LXJFD3&P=Z
Gearbox: http://www3.towerhobbies.com/cgi-bin...?&I=LXJFD2&P=Z

And here's the battery I will be using in both setups (a 3-cell 20C LiPo - 11.1V, 20C): http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXMDN3

Now for the new stuff:
A 35-30-950 outrunner engine, also from Great Planes: http://www3.towerhobbies.com/cgi-bin...?&I=LXLWT9&P=V

And the accompanying ESC: http://www3.towerhobbies.com/cgi-bin...?&I=LXKSY5&P=V

The recommended prop is still the standard 10" x 4.5", so not a lot of work to be done there.

What I'm wondering is - am I missing anything? I think that covers everything I need, but I'm left with a few questions regarding the mounting. For instance, how do I ensure that the new motor+mount has the same pitch/offset as the original? How do I even find out what the pitch/offset of the original is?

Basically, I'm well outside my realm of expertise here, and could use a hand. This isn't really about choosing the power train, but implementing the one I've purchased.

Any help would be much obliged!
Rob
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Old 02-18-2009, 10:22 PM
  #5  
birdDog
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The only difference I see is the difference between $104 and around $35 from headsuprc.
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Old 02-18-2009, 10:43 PM
  #6  
Leo L
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Hi Rob,

E-flite makes a terrific mount for brushless motors. It consists of 2 pieces. One attaches to the motor and can be attached to a "stick". The other is a matching "stick" attached to a flange that can be screwed to a fire wall. If you need to offset the motor, use different amounts of washers between the flange and the firewall. The amount of off-set does not need to be exact. Estimate it the best that you can, then do a test flight. If the plane pulls constantly to the left, add more right offset. If it pulls to the right, reduce the offset. I'm surprised that you plane has down off-set, which is usually not needed on mid-wing aerobatic planes. If you find the plane trying to climb, especially as you increase the throttle, add a little down off-set. If you find that you need to constantly use up elevator, even to fly level, reduce the down off-set.

http://www.horizonhobby.com/Products...rodID=EFLM1915
http://www.horizonhobby.com/Products...rodID=EFLM1916
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Old 02-19-2009, 03:05 PM
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KrunkSplein
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Thanks Leo. I am unsure what the offsets on my current plane are - there very well may be no vertical offset. I've double checked my manual and there is no mention of axis offset whatsoever. I'll check online to see if there is any sort of repository of offset information, but I think I may just have to break out a protractor and do some best-guessing.
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Old 02-19-2009, 05:58 PM
  #8  
flydiver
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Rimfires are 'passable' motors that cost more than they are worth.

Take a look at the Suppo from LightflightRC.com. He has links to great specifications from Dr. Kiwi. My buddy has one in his Mini and it works fine. You don't need a 20A motor-too much. You are running around on less than 10A now.
That said a problem with upgrading that plane is the design is for the weight of the brushed (like 90g) motor and NiMh battery (heavy) up front. It can be problematic getting the CG right with lighter gear. My buddies' Suppo is lighter and he needed to add lead to the front.

Usual starting offset is down and R ~ 3 degrees. This counters the pull and torque of the motor. You can do this with washers and shims, depending on how you mount things. Experiment. Where you end up depends a LOT on the power and prop. The more excessive, the more offset needed.

DO NOT buy the ESC. Download and read CAREFULLY the LVC information on them. NOT lipo friendly. You want MINIMUM of 3.0v/cell LVC. Dinosaurs, behind the times. Don't buy GWS ESC either, similar problem. Tower has a lOT of stuff but they also sell things that aren't so hot and make them out like they are superior products deserving of a good price.
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Old 02-19-2009, 07:25 PM
  #9  
KrunkSplein
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Originally Posted by flydiver View Post
Rimfires are 'passable' motors that cost more than they are worth.

Take a look at the Suppo from LightflightRC.com. He has links to great specifications from Dr. Kiwi. My buddy has one in his Mini and it works fine. You don't need a 20A motor-too much. You are running around on less than 10A now.
That said a problem with upgrading that plane is the design is for the weight of the brushed (like 90g) motor and NiMh battery (heavy) up front. It can be problematic getting the CG right with lighter gear. My buddies' Suppo is lighter and he needed to add lead to the front.

Usual starting offset is down and R ~ 3 degrees. This counters the pull and torque of the motor. You can do this with washers and shims, depending on how you mount things. Experiment. Where you end up depends a LOT on the power and prop. The more excessive, the more offset needed.

DO NOT buy the ESC. Download and read CAREFULLY the LVC information on them. NOT lipo friendly. You want MINIMUM of 3.0v/cell LVC. Dinosaurs, behind the times. Don't buy GWS ESC either, similar problem. Tower has a lOT of stuff but they also sell things that aren't so hot and make them out like they are superior products deserving of a good price.
Sadly, I ordered both the motor and ESC yesterday. I've double-checked the ESC LVC versus the battery's minimum discharge voltage, and sure enough the LVC is .063 volts lower than the minimum.

What really frustrates me is that the components I listed above are *exactly* what Great Planes recommends when performing a brushless upgrade of the Mini Super Sportster: http://www.electrifly.com/powersyste...nversions.html. That's why I was so quick to actually place the order.

I'm new to the hobby and I feel like I just got scammed because I don't know enough to choose my own power system. Even now, looking at the different Suppo motors, I have absolutely no idea which motor I would choose for my mini. All I really wanted was a more efficient power system and maybe a little more power when flying in the wind.
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Old 02-19-2009, 08:12 PM
  #10  
flydiver
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You didn't get scammed, you just had a learning experience. Almost everything you learn in this sport will be the hard way.

Of course Tower recommends those products-it's their line. The system will work fine for you. This is a pretty damn complicated sport actually, so give yourself time to figure it out and some slack to make mistakes because you will make a LOT of them. If you have the time reading in the groups is your friend. I've learned to research EVERYTHING. Takes time but it usually pays off.

FWIW, except for the poor LVC the GP ESC will work fine. I use Castle (similar expense but MUCH better) after struggling with crap Towerpros for awhile. They are cheap, and not so hot but you'll find folks that love even those BECAUSE they are cheap----until they have to try to stick program them, then they are not so happy. Most folks have no idea what the ESC is really doing. If it makes their motor go around they are happy.

Fly your plane by time. Most experienced fliers do that anyway. Start conservatively and measure the voltage after a few minutes of flying. You want at LEAST 3.7v/cell RESTING voltage. Do NOT go below that or you start stressing the lipo and shortening it's life. After awhile you'll get a feel for it. Some transmitters have timers, some folks mount a small timer, some use a cellphone timer, etc.

The motor will be fine-the extra weight will be useful in this case. Compared to a TowerPro suggested for $10-15 you'll end up liking it. The TP motors are very inexpensive, work fine, have noodle shafts that bend if you look at them cross ways, and wires that break almost as easily. If you use a prop saver + shortened shaft and glue the exit wires down, they are OK. For a system like the Mini-S that needs the extended shaft out the cowl you would have been upset after awhile with the stupid shaft. You would have felt 'shafted'.

Believe it or not a properly geared brushed system can be as 'efficient' as a low end brushless. It's just heavier. Don't necessarily believe every other newbie that parrots the 'efficiency of brushless' without even knowing what that means. There are some brushless motors (TowerPro) that are not very efficient. What they are is cheaper, lighter, and more powerful than a similar brushed motor. So, what they really mean is light, cheap, powerful. Cheap doesn't often equate with efficient (power in vs. power out).

FWIW- a similar motor to what you picked would be the Suppo 2217-09 (weight, KV, and power output).
You would have been fine with a 2212-15. I think that's the one my buddy uses.

Pick an ESC that is at least 5-10A larger than the highest Amp draw of the motor.

Make SURE you prop it right. Motors have a narrow range of best props. Too small and you lose power, too large and you burn things up. In your case it might be best to go on the smaller side since you have got plenty of motor.

Funny story-a buddy crashed a similar plane and wrecked the motor. So he got a new one about like the one you are putting on. He told everyone to come watch THIS BABY! He punched the throttle >>>> it took off like a scalded cat, did a complete roll 3 feet from the ground while everyone's eyes popped and chins dropped and slammed into a tree. This all happened in 2 seconds. He never even reacted after he punched it things happened so fast.
So-take warning. Make SURE you have that CG RIGHT, everything trimmed, and be a bit easy on that first take off.
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Old 02-20-2009, 02:40 AM
  #11  
KrunkSplein
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I'm essentially a coward when it comes to takeoffs and landings, so there's no worry there. Your post actually brings me to a couple of really generic questions about testing and setup that I have been meaning to ask.

First off, measuring voltages. I gather that you simply use a Digital Multi-Meter (DMM) to read the voltages, but where do you place the leads? I understand that you can simply use the sockets on the dean plug to get overall voltage, but what about per-cell?

Secondly, pull strength. I occasionally see reference to airflow coming from the prop at WOT, but the only way I can see of measuring that is with an anemometer, which are generally more expensive than an entire plane. Is there something I'm missing, or is this simply a measurement that we don't need?

Anyway, it's time to read the instruction manuals that came with my charger and balancer! If there's one thing I DO know, it's not to mess around with LiPos.
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Old 02-20-2009, 03:30 AM
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flydiver
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You can do the majority of measuring you need to do with one of these:
http://www.rcgroups.com/forums/printthread.php?t=311574
Probably the most useful tool in my 'box'. I'd be in the dark without it.

For individual measurement (and charging) I use my FMA Cellpro 4S:
http://www.fmadirect.com/products.htm?cat=45&nid=4
It tells me the % left after use, the individual cell voltages, charges and balances it all at the same time. Great product. Highly recommended.

With a multimeter you stick the probes on the little tabs on the side; one pair, shift over to the next pair, etc. BE CAREFUL! Even a tiny short here will be nasty. There are also little probes you can get that go in the balance tap and tell you. If you have a balancing charger don't' worry about it, just go for the total from the main tap.

Thrust is measured with a thrust stand. You pretty much have to build your own. Mostly reserved for the interested or dedicated. You can get the data you want with the wattmeter. That's all I use. Amps or watts is similar to horsepower and you can measure those without a thrust stand. Swap props, test, you get new numbers. Most motors have amps/watt capacity specified-get familiar with those #'s. But you have to learn that most of the specs are also BS (Rimfire, cheap Chinese motors, ESC, batteries, electronics in general). They promise much but deliver, in general, about 75% of that. Down grade specifications at least 20% unless proven otherwise.

You may find it worthwhile doing some reading here:
http://www.ezonemag.com/pages/faq/index.shtml

Edit-Here's some better and more objective info on the Rimfires. Better results than I would have led you to believe. See, trust but verify....easy to say, harder to do.
http://www.rcgroups.com/forums/showthread.php?t=739722
Stuff by Dr. Kiwi is worth reading. I try to see if any motor I'm interested in has been tested by him, or someone.

Last edited by flydiver; 02-20-2009 at 05:01 AM.
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