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Old Feb 10, 2013, 08:13 PM
Not as Good as The Kid
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Dead... The APC spooled up faster and just lost it at WOT when Tom jammed it to full open. I don't have a full handle on what is happening because it's a little different than what I first expected a year ago, when we were discussing timing issues. But this is what we were able to observe. Keep in mind the test data charts from December 2010 where the APC showed higher power readings at most of the throttle curve until the Xoar took over near the top end. Also remember that when everything was new, including the batteries, all props lost timing at WOT, and that's why Tom set the endpoints to 88%.
  1. The Xoar lagged in throttle response, like a low start. No problem with timing.
  2. It was more noticeable when we flew the MXS with the 16x8 Xoar and the Talon 90 to an unrestricted 1622 Watts on the same DM4315-480.
  3. Two weeks ago, I put the APC back on when I was practicing harrier landings. I broke one and didn't want to waste the two I had left.
  4. I immediately felt a quicker spool to a higher RPM, and more speed, taking more momentum into maneuvers like pop-tops. For me on the Edge, they were never so crisp.
  5. I rarely go from idle to full without sliding the throttle a little easier than Tom.
  6. Yesterday, I got two flights on the Edge while Tom was flying Frank's plane and his 50cc Godfrey, again, with no timing issues.
  7. He decided to fly the Edge, and on take off, noticed a timing squeal. He then duplicated it a few times in the air, then landed.
  8. I put my feet in front of the stabs, and tried to duplicate the squeal on the ground, and did, right away, by jamming WOT.
  9. I changed the prop back to the Xoar, and was not able to duplicate the issue, which was no surprise since we had been flying it this way for about 14 months.

Right now, I'm thinking that the HK ESC was never able to interpret the motor RPM on quick acceleration. Now that the batteries are sagging a bit, the switch-over to the lower load of the APC meant a noticeable return to a quicker acceleration and the HK's ESC's inability to keep pace. Returning to the load of the Xoar meant a slower spool-up and an easier interpretation for the ESC once again. That's all I got so far.
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Old Feb 15, 2013, 04:28 PM
Not as Good as The Kid
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South Pasadena, FL
Joined Sep 2009
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I'm picking up another Ice2 HV120 tomorrow... I'm going to start putting some things together for the 87 MXS so it's not as painful when the plane becomes available.

I'm thinking about the Q80-7M with a 21 or 22 inch 3-blade, either electric or not. The motor can swing a 24x10TH 2-blade, so the 21x11.5 narrow (N) 3-blade CF Mejzlik should be an easy alternative, and lower the Amps and Watts to what I'm looking for... 3500 to 3800 Watts and 95 to 100 Amps.

It's going to be an expensive prop test, but I need to know what the motor can do before I waste the power on a plane that can't clear, and certainly doesn't need, a 24 inch 2-blade. I'm guessing about the power trade off, but static thrust calculators show 4000 Watts on a 21x11.5 3-blade spinning 6300 RPMs, which could be close.

The motor is already mounted with an HV160 so there should be no harm, other than the $92 wasted expense if the prop doesn't work out. If not, I should at least get the data I need to decide what's next. If it turns out that it can handle more Amps, I'll try the 22x10 3-blade Xoar PJI for glow engines, at $75.

Anyone have any 3-blade experience with electric setups, or know someone?
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Old Feb 15, 2013, 06:05 PM
Yin & Yang
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Hey Aeroplayin, You did mean 78" right?
I want it bad but I just don't see me doing it with Electric. I'd need a whole new set of lipos to fly with. I'm nervous enough with the 20+ lipos I have now. And that is only the 4S and 6S. I don't see 8S working with 2700mah batts. Any thought on 12S 3300mah? Wife want me top get a gasser and I admit I have always wanted one. I was hoping to see the DA 35 out by now though. Decisions Decisions
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Old Feb 15, 2013, 06:14 PM
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United States, AK, Anchorage
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Quote:
Originally Posted by Liberty10 View Post
Hey Aeroplayin, You did mean 78" right?
I want it bad but I just don't see me doing it with Electric. I'd need a whole new set of lipos to fly with. I'm nervous enough with the 20+ lipos I have now. And that is only the 4S and 6S. I don't see 8S working with 2700mah batts. Any thought on 12S 3300mah? Wife want me top get a gasser and I admit I have always wanted one. I was hoping to see the DA 35 out by now though. Decisions Decisions
If I get the 78" MXS I am gonna setup with as a 12s (2 x 6s 3300s).
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Old Feb 15, 2013, 06:51 PM
Yin & Yang
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Quote:
Originally Posted by bryansifsof44 View Post
If I get the 78" MXS I am gonna setup with as a 12s (2 x 6s 3300s).
I wasn't sure if that would work. What motor ESC give me more I want to know. If I could use the same lipo as I do on the 60" airframe it might be too tempting to not go electric.
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Old Feb 15, 2013, 06:57 PM
Not as Good as The Kid
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South Pasadena, FL
Joined Sep 2009
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Quote:
Originally Posted by Liberty10 View Post
Hey Aeroplayin, You did mean 78" right?
I want it bad but I just don't see me doing it with Electric. I'd need a whole new set of lipos to fly with. I'm nervous enough with the 20+ lipos I have now. And that is only the 4S and 6S. I don't see 8S working with 2700mah batts. Any thought on 12S 3300mah? Wife want me top get a gasser and I admit I have always wanted one. I was hoping to see the DA 35 out by now though. Decisions Decisions
Yes, the 78 is 87 with the tips on so I'm not sure what to call it, like the 60, errrr... 64 MXS.

My Q80 is a 210 Kv 10S motor, so 6S batteries are out of the question.

The only problem I see with the 3300 to 3500 6S batteries is that at 3500 Watts and something like 3.72 volts per cell (44.64v), we're going to need 78 Amps. It's a bigger plane so there's no way we're going to get the same 450 mAh per minute capacity usage we get on the 60 EXPs.

We're using 670 on the 78 with 10S now, and I'm guessing a 12S setup with do 580mAh per minute at 3500 Watts on a 180Kv. Although the 5000mAh batteries go 6 minutes on 10S, and the 12S setup on 5000's will do 7 minutes, the 12S setup on 3300's will only do a few seconds over 4.5 minutes -- all on the same 22x10 prop.

As for gas, I'll probably not go gas in this size again unless the DA35 is just absolutely outstanding and can swing at least a 21 prop to around 7000 RPMs, which is entirely possible, I think. 50 to 60cc is where I'd go gas because 5 minutes of flight time is becoming less fun. The DA50. R-50 (Revolution), DLE55 (with a few replacement parts including a Bowman ring), BME 58, DA-60, or DA70 would be engines to think about.

I would typically not consider a DLE55 because it is the only one that can't swing a 24, so it would be my last consideration. The Revolution, BME, and the DA, are expensive, but for good reasons. The R-50 is a 52cc engine that can swing a 24x8 to 7000 RPMs, and is very light, like the BME, which is one of Frank's favorite engines.
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Old Feb 15, 2013, 07:08 PM
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I currently run a custom wound Motrolfly 4330-216 in my 71" slick to 3100 watts peak and for me would be plenty of go for a 78" IMO. I would however get it wound slightly lower to allow for a 22" prop for a 78". This may not be viable for some in a warmer climates though as I got the ok from Ken to run the 4330 that high in the Alaskan climate. However I heard that Ken does rewinds on other motors, and a slightly bigger hacker re-wound to handle 12s and a 21-22" prop may be a option for you guys in warmer climates. I really like my 12s setup in the slick running 2600mAh batts I share with my 500 pro heli. All I need for a ESC is a little ice 80HV to handle the 67 amp peak I am seeing with my setup.
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Old Feb 15, 2013, 07:17 PM
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Originally Posted by Aeroplayin View Post
Yes, the 78 is 87 with the tips on so I'm not sure what to call it, like the 60, errrr... 64 MXS.

My Q80 is a 210 Kv 10S motor, so 6S batteries are out of the question.

The only problem I see with the 3300 to 3500 6S batteries is that at 3500 Watts and something like 3.72 volts per cell (44.64v), we're going to need 78 Amps. It's a bigger plane so there's no way we're going to get the same 450 mAh per minute capacity usage we get on the 60 EXPs.

We're using 670 on the 78 with 10S now, and I'm guessing a 12S setup with do 580mAh per minute at 3500 Watts on a 180Kv. Although the 5000mAh batteries go 6 minutes on 10S, and the 12S setup on 5000's will do 7 minutes, the 12S setup on 3300's will only do a few seconds over 4.5 minutes -- all on the same 22x10 prop.

As for gas, I'll probably not go gas in this size again unless the DA35 is just absolutely outstanding and can swing at least a 21 prop to around 7000 RPMs, which is entirely possible, I think. 50 to 60cc is where I'd go gas because 5 minutes of flight time is becoming less fun. The DA50. R-50 (Revolution), DLE55 (with a few replacement parts including a Bowman ring), BME 58, DA-60, or DA70 would be engines to think about.

I would typically not consider a DLE55 because it is the only one that can't swing a 24, so it would be my last consideration. The Revolution, BME, and the DA, are expensive, but for good reasons. The R-50 is a 52cc engine that can swing a 24x8 to 7000 RPMs, and is very light, like the BME, which is one of Frank's favorite engines.
I think you may be under estimating the runtimes of the 3300mAh batteries... with 12s 2600mAh on a 70" airframe I have my time set to 6 minutes and with telemetry usually fly a bit longer. With a 78" plane and 12s 3300mAh, I should be able to see at least that and maybe more. Now Tom... he most likely will have slightly less runtime then me. With my flying style, I am not the hardest on the throttle, but I am definitely not the softest either.
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Old Feb 16, 2013, 09:57 AM
Not as Good as The Kid
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Yes, I definitely tend to be conservative when doing flight time estimates since it all has to do with Amps, and that's a subjective thing that takes the pilot into consideration, as well as the setup. I get at least one minute more out of the same plane than Tom. But I've also found that the usage goes up with size, just like Amps, and it would be interesting to come to a solid understanding about mAh/min.

For us, the 48's use mid-300mAh's per minute, the 60's use mid-400's, the 78 uses mid-600's and the 50cc uses mid-700's unless flying big-sky IMAC routines, where it's possible to use mid-800's. From what I saw from Herc's review of the 70, it looks like mid-500's for him. This seems like an interesting pattern, but make sense because in physics, power and work are related by mass, time, and distance. Think about the old word problem about how many kilocalories does it take to move an 80kg fireman with 30kg of equipment straight up a 20 m ladder in one minute? This is energy expended to move a mass over distance and time under resistance. Same for airplanes, cars, trains, or anything under power and in motion.

Anyway, if there is a direct relationship between Amps, prop size, plane size (resistance), and weight, which there should be, then this could mean you will use about another 100mAh per minute moving from the 70 to the 78.

So if you are using 75% of your 2600mAh battery in 6 minutes, then you are using 325mAh per minute. If it is true (may not be, just don't know yet) that you will use 425mAh per minute in the 78, then 75% of the 3300mAh battery will be used in 5.8 minutes.

This works out for the planes we fly, and how we fly them, but if you fly bigger planes differently, then this can all change, so it is just too subjective to nail down from one pilot to another.
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Old Feb 16, 2013, 10:49 AM
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What is the weight of the batteries that you guys are running in the 78"? Also all up weight? I know you gave this info before, I just can't remember.
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Old Feb 16, 2013, 11:01 AM
Not as Good as The Kid
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I thought about this a little more and put together this chart to illustrate what I'm talking about, and to clear it up in my own sick mind....

We have the wingspan and weight of several EF planes. The third column represents a relative Watts reading of 250 Watts per pound. I did this in order to power all of the different size planes in a relative manner, close to what we can actually do with the motors we have discussed. I threw in the relative HP just for kicks. I then displayed the cells, and volts, then calculated the Amps relative to the volts and relative Watts.

I then assigned a real battery capacity of my choosing in order to obtain a 6 minute flight at 40% of the discharge rate. I then calculated the capacity if we were to use 75% of the batteries capacity for all setups to keep things relative. I then calculated the Amps if we were averaging 40% of the WOT Amps throughout each relative flight, again, to keep things even.

I then calculated the discharge rating C, then calculated the amount of time in minutes to discharge the 75% of full capacity. The last column represents the mAh's used per minute for each setup.

Values will certainly vary from one plane to another, and from one pilot to another, but this is the relationship between all setups, if we used a computer to fly the planes under the same conditions at exactly the same throttle setting.

When the popup opens, you can click on the graph and it will expand in a new browser window, making it easier to read.
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Old Feb 16, 2013, 11:30 AM
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Now how does it compare when you come in at in at 11.5-12lbs with the lighter 4330 motor and the smaller 12s 3300mah batteries? 11.5lbs is the lower end of the recommended weight for the 78" extra.
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Old Feb 16, 2013, 12:04 PM
Not as Good as The Kid
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Now how does it compare when you come in at in at 11.5-12lbs with the lighter 4330 motor and the smaller 12s 3300mah batteries? 11.5lbs is the lower end of the recommended weight for the 78" extra.
Going from 2x 5S 5000 40C Sky's to 2x 6S 3300 30C Sky's will drop a half-pound... 8.32 oz. If I make the weight adjustment in the chart (12.98 lbs instead of 13.5), the flight time changes from the 6.5 minutes to 6.8 minutes, which is 18 seconds. What'a the motor weight for the 4330 with mounting and prop hardware?

My Hacker, prop hardware, and the A60MM mount and hardware is 32.64 oz. If your setup comes in another 6 oz lighter, then 12.60 pounds means 7 minutes, or 30 seconds more relative flight time.
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Old Feb 16, 2013, 12:12 PM
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But the problem is that you may not be able to get the relative 3375 Watts out of the 4330, or it may not be recommended to try. A smaller prop may mean you're on the throttle more, for longer bursts, so we begin to lose the relative aspect of the comparison.

Edit... actually it's 3150W at 12.6 pounds, but we will have to achieve this power level to keep all things relative. Otherwise, it could mean less flight time because of the more Amps used trying to keep up with the easy 3375 Watts the A60 can deliver on 10S.
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Old Feb 16, 2013, 03:22 PM
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The 4330 is 560g or 19.75oz all up weight of the motor. I wouldn't push the motor past 3150W peak. BTW, Chris only recommends 2600-3000 watts for the 78" Extra so I think 3150W should be plenty of power for the 78". Nothing like Tom's setup, but on the lower end of Chris's recommended all up weight. In comparison to gas my 4hp on the 4330 is more then the 3.85hp of the O.S. GT33 or the 3.7hp of the DLE30 and the 3.6HP that EME 35 says in their specs. I am interested to see the performance of the DA35, but most I am almost sure I wouldn't go gas until 50CC and that probably still will be electric.
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