matt_xb8r

My Feedback: (8)

could anyone recommend a good motor rated for 6s lipo for this plane? I already have several 6s packs that I use in other things is the only reason I ask. I've found a couple Scorpion motors that look like they would work great but just curious what other suggestions people have. Thanks!

cap10b

Matt,
I dont know if WH tested for a 6S motor on lipo, I think its flown 6S on A123 but not sure. I think your in uncharted waters. Better you tell us what 6S motor to use.

jds

rctom

True:

I already have talked to Matt. The original HD motor is spec'd to 4S Lipo, I've used it on 6s A123 successfully. But Matt fried his on 6s Lipo. The newest motors, the DYS 3548-5, is spec'd to 5s Lipo but I don't blame Matt for being unwilling to test the replacement at 6s. The ESC we supply is good up to 6s Lipo but not the motors.

TF

JonPa

Has anyone tested the DYS motor on this plane using a 5s battery? I had planned on 4s (3000) for this plane, but then I received this motor instead of the HD motor. I am sure it would be serious overkill, but......

matt_xb8r

My Feedback: (8)

Yeah the HD motor flew great on 6s.....for a few minutes....needless to say it would vertical forever and flew great once I got the battery placement/CG right. I'm kind of hesitant to ruin another motor so was just kind of looking for a suggestion. I've come across a couple that should work well but it never hurts to ask. Making a trip down south this weekend so may look and see what the hobby shops have along the way and decide if Iwant to pick up a motor or a couple 4s packs.

Tom - Thanks for the awesome plane! Got the DYS motor today. Imay borrow a buddy's 4s pack and see how it does on that while I'm shopping for a motor. I appreciate you sending the new one out so quick.

rcpilot_971

My Feedback: (50)

what 4s pack is everyone using on this Plane?

rctom

A 4S 3000 pack is overkill. A 5s is a waste of money.

I usually sell the eflite 4s3300.

TF

rightflyer

I have the HD35-42. I thought it was spec'ed for 4cell lipos, but now I am not sure. what is everyone flying?

rctom

Yes it is spec'd for 4s Lipo.

rightflyer

Great. What ma pack is everyone using? 3000ma?

Take2Flight

I had the same problem with my Slick 56 received last week: the canopy latch would not budge. I found that pressing down on the canopy and pulling back on the latch worked. I worked some vaseline into the latch plunger and its okay now.
Ash

stangman67

My Feedback: (1)

Hey Tom,

Is the exceed power 32 a good choice for this plane (13x6 prop most likely) ? I had a rimfire 32 I was going to use but it bit the dust a few weeks back.

Thanks,
Zach

stangman67

My Feedback: (1)

Also what color/brand is the yellow on the eslick?

matt_xb8r

My Feedback: (8)

Well opted to try to stick with my 6s packs and the DYS motor. The specs on the DYS are better, 770watts versus 600 on the HD, and rated for 5s versus 4s. Amp rating looks to be about 10 more from what I can find too. So I took a power meter and ran inline to see what the numbers were that Iwas pulling. If left with the end point all the way out it was pulling ALOT more than the DYS motor could handle, as was expected. Ikept turning the end point down till it came within the wattage specs. So with the end point sitting on 35, had to turn it WAY down, its showing just under 770w and about 36 amps static. In the air I figure it will pull a little less seeing that it will be unloaded. Haven't had a chance to fly it yet but should be able to by the end of the week. Anyway, just thought I'd give an update in case anyone else is in the same situation.

JonPa

From what I have heard and read, limiting the endpoints on the throttle is not a good way to keep the motor or esc from burning up. According to Lucien Miller limiting throttle does not really limit amps to the motor and you might still end up burning up the motor or esc. You are better off going to a smaller prop. I am no expert, but if you are interested there is a discussion on the power system corner component of the ATTF podcast.

ATTF#71 at 55:00 AMP ratings of ESC/system at partial throttle?
ATTF#84 at 53:39 Can you use endpoints to control/limit full throttle?
ATTF#148 at 1:07:30 Limiting throttle end point to limit amps

Jon

matt_xb8r

My Feedback: (8)

Hey Jon - I'll go check those out this evening.

I did A LOT of reading beforehand and seems there are mixed reviews on how you can do it. Had several conversations with an electrical engineer as well. Which is why I went to a power meter to see for myself how it was going to operate. I've seen it written both ways in that one thing kills the motor or this other thing kills the motor and then the argument ensues....blah blah blah. I'm afraid I'm just going to give it a shot and see how it goes. If it goes up in smoke then its on me. After a few days of reading there didn't seem to be a definitve answer and there are multiple opinions. I can tell you that turning down the end point DOES decrease the amperage that the motor pulls and that my whole setup sees going through it. It also slows the RPM enough to keep it and the wattage within spec with the given prop. Keeps the voltage going out of the esc to the motor within spec as well. If I change to another prop I just have to hook the power meter back up and would be able to increase/decrease the end point depending on the prop. The problem with changing to a lower pitch prop and not turning down the endpoint is that the motor sees higher RPM than its built or rated for and you start having other problems like bearing failure, etc. The only thing that is different at this point in my setup is the voltage being seen by the esc, which is rated for 6s. Well that and the fact that the amperage is significantly less than when its on 4s. I can post all the numbers later tonight if anyone wants to see them. I found it rather interesting when I got to messing with it. Didn't exactly react the way I expected but I'm going with the old theory of the numbers don't lie. My opinion is that the amperage is what will kill the motor the fastest as it can't dissipate enough heat and once it gets to a certain point it just snowballs and poof. We'll see how it turns out.

JonPa

Matt,

I will admit that I limit throttle on my slick to keep it from getting warm and it does work, but apparently not a good idea. The reason limiting throttle does not limit amps (peak amps, not average overall) is due to the way that the esc reduces amps/voltage to the motor by chopping out cycles of the esc.

Also, with regard to prop size. Glow is different than electric. Glow is a constant power situation. If you lower prop size, it spins faster. So if for example, you run up the motor without a prop it will attain an rpm high enough to blow apart the motor. However, electric motors are in a constant rpm mode, which is determined by the KV rating. So no matter the prop size, it spins up to a specific rpm regardless of the power output. So larger props draw more current, and can burn up the motor, and smaller props will draw less current. That means you can actually run up the motor to full throttle without a prop and not damage the motor. It just doesnt draw any current.

Jon

matt_xb8r

My Feedback: (8)

I'd have to say that I question the amperage issue. With my setup the higher voltage also allows the motor to pull less amperage and put out the same wattage. Understanding exactly how the esc works was rough and I still don't completely get all of it so I'm no expert on the chopping and cycle situation. But based on the readings I got, both average and peak, they were able to be lowered overall and they are low enough to stay within spec from everything I've found so far. It was enough to make me want to give it a try.

I agree on the prop issue up to a certain point. When you are running more voltage than the motor is rated for then RPM becomes an added concern if you aren't monitoring/limiting the other things. In other words if I propped it where the current draw was within spec and didn't limit the endpoint then the motor would be spinning fast enough to make other things a concern. I udnerstand the concept though.

JonPa

Matt,

Yeah, I dont really understand the esc chopping effect either, but I think it does really make more sense to go to a lower prop size. Keep in mind that that constant rpm of a motor changes with battery voltage. So for example, a 1000KV motor runs at constant voltage of 11,100 rpm at 3S and 14,800 at 4S, but they are constant values regardless of prop size.

With regard to amp draw, it increases at higher cell counts rather than decreases. Here is a quote from a back and forth email discussion I had with Lucien Miller, which I found very informative:

"the power rating of a motor is simply a measure of how much heat it can handle while it does its job spinning the prop.

If you keep the same prop on a motor, going from a 3-cell battery pack to a 4 cell battery pack will result in a large increase in current, and an even larger increase in power. This is a compound effect, because the faster you spin a prop, the more drag it has and the more load it puts on the motor. Also, when you increase the voltage, the motor pulls more current, so these two effects multiply together when you go up in voltage.

For example, if we look at the SII-3014-1040 motor we spoke of earlier, here are a couple of data points from the prop chart with an APC 10x5E prop.

Running at 10.5 volts, 3-cell Li-Po equivalent

Amps - 21.8
Watts - 229
RPM - 9,625
Thrust - 45.3 ounces
Pitch Speed - 45 MPH


Running at 14.0 volts, 4-cell Li-Po equivalent

Amps - 35.3
Watts - 494
RPM - 12,100
Thrust - 74.7 ounces
Pitch Speed - 57 MPH

Looking at these numbers you can see some mathematical relationships develop. The voltage was increased by 33.3% going from 10.5 to 14.0 volts. The motor RPM and Pitch speed increase as a direct relationship to the increase in voltage. Going from 9,625 RPM to 12,100 RPM is an increase of 25.7%. Because the prop load increases and its speed increases, the 33.3% increase in voltage does not correspond to a 33.3% increase in RPM. The actual mathematical relationship is the voltage increase raised to the ¾ power.

If you look at the amperage increase, it goes from 21.8 amps to 35.3 amps, which is an increase of 62% from a 33% increase in voltage. This is roughly an increase of the square of the voltage increase.

The total power went from 229 watts to 494 watts, a whopping increase of 116%, which is roughly an increase of the cube of the voltage increase.

Because the motor heats up more at the higher power levels, its efficiency does go down a bit, so the actual increases are multiplied by the lower efficiency and you get a bit less of an increase than you would expect.

So going back to your original question, you can see how much the current increases with the same prop when you go from a 3-cell to a 4-cell battery. If you did try to keep the same prop, you would need to increase the size of your speed controller. This is why you normally use a smaller prop on a motor when you go to a higher voltage battery.

Looking back at the prop charts, if you run the motor on a 4-cell battery, you would need to drop from a 10x5 prop to a prop around an 8x5 to pull the same current. However, even if the current is the same, the total power will go up by 33% because the voltage went up 33% and total power is equal to Voltage x current.

Hopefully I did not lose you too bad in the math, but that is the relationship between voltage, current and power when you change things in a motor."


Hope all this helps (rather than just irritating):-)

Jon

matt_xb8r

My Feedback: (8)

Jon,

HAHA...all the info I can get helps....it doesn't irritate me in the slightest to continue the discussion.

But here's something to think about that is a more along the lines of what I'm looking at.....with regard to your example above lets say you have a 3s setup and a 4s setup. Same motor, esc, and prop. Spin them at the same RPM or spin them both up till the wattage is the same. At that point what is the current draw on each? Icompletely agree that if you run them up to max throttle there is an increase in everything when the 4s is compared to the 3s.....but what happens when you choke the 4s down to meet the performance limits of the 3s? Its at that point that you should see where there is a decrease in current pull when they are compared side by side.

Matt

JonPa

Matt,

I agree that limiting throttle endpoint would lower RPM and the corresponding amp and wattage output, but the esc chopping effect (whatever that is-LOL) would suggest it is bad overall for the motor. It would seem to me based on the above information from Lucien that there is no downside to simply propping down until you get the amp draw and overall wattage that is safe for the motor. Power would be the same, but no extra wear on the motor and you get to use the full throttle range on the esc.

What do you think?

Jon

matt_xb8r

My Feedback: (8)

I think I'd still be worried about RPM using full throttle range but I understand the idea behind it all. Its hard to say with any certainty when I don't have a full understanding of the ESC and how it functions completely, as to how that would affect things differently than simply turning the end point down. There is lots of information out there but too much contradiction in what actually takes place, etc. I'm curious to see how different things affect the setup, how much heat is generated, what flight times are, etc. I have the setup now where its within limits using the end point "theory" so Ithink I'll try it like that for a few flights, measure everything and see how it goes. Then move to the prop and see how that works out and what the differences are. May end up going through another motor before I get it worked out but I'd be ok with that if it helps me get where Ineed to be and helps me get some real world results. Gives me some things to play with for a little while......HAHA. The weather isn't cooperating most days right now so I don't get much time to fly but I'll post results as I go.

Matt

stangman67

My Feedback: (1)

Just a quick PSA. the Exceed monster power 32 is indeed a great match for this plane. And for 22 bucks shipped from hobby parts, the price cannot be beat (specially since you don't have to wait for it to be shipped from HK) . It should be good for about 800 watts with a 14 inch prop on 4s. I will be running a 13x8/14x8 which should be good for 750/800 watts or so. Can you say rocketship?

BTerry

My Feedback: (8)

Zach, what is the kV on that motor? I might pick one up just for fun. Having the bigger diameter prop will help with 3D.

*edit* I found the answer, it is 770 rpm/V( http://www.hobbypartz.com/monsterpow...ess-motor.html ). One note of caution, they claim a max continuous current of 42A and 55A burst. 42A at 14V is 588 watts. However at that price it is cheap enough to risk burning it up.

stangman67

My Feedback: (1)

Its a 770kv motor. Right at home with a 14 inch prop

I've found that most motors are fairly underrated. The Infinite motor I am using for my mx2 is rated for 1600 watts and people have pushed it well over 2k watts without issue. I have no qualms about pushing this exceed past 700 watts, and if it quits on me, I'll just mail order an infinite. Its amazing how fast those exceed motors sell out. They were out of stock up until 2 days ago and now they are out of stock again.