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Old May 26, 2007, 10:37 PM
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I.C.O.N.'s Avatar
Twin Cities, MN
Joined Feb 2006
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Great to hear you had a successful Maiden!

Sounds like you have some good power going. Can't wait to see the vid!

I think you would be surprised at how far the stryker has been pushed.

Have you read The Dark Side Thread over on RCU?

Those guys don't call it fast till they hit 110+! But they do mod the airframe to stabilize it.

Have Fun!
Andy
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Old May 27, 2007, 09:11 AM
Gone Flying.
ChrisWNY's Avatar
Western NY
Joined Nov 2006
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Andy -

Yes, I have skimmed the "dark side" thread, just haven't read into it in detail. I could probably get more top speed by propping down to a 7x6, but love the thrust and maneuverability that I get out of the 7x7 Graupner.

I modded the Stryker airframe to take the higher speeds (and to prevent wing warping) by running a hollow c/f spar through the rear, underneath the motor mount area. The c/f spar is completely embedded inside the fuselage; I used a small dremel bit to route a channel from one wing tip to the other, dropped in the c/f spar and Sumo glued it in there. Then I slapped some strapping tape along every spar on the underside of the airframe to really lock things in place and to add extra durability.
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Old May 27, 2007, 06:00 PM
Crashing planes since '05
EP Dean's Avatar
Burnaby, BC, Canada
Joined Sep 2005
211 Posts
Propping the stock motor/esc.

I've been through the thread in its entirety today looking for "the" prop. I now know what to prop if I was running the Mega or an eflite 6, but I dont seem to see anyone playing with repropping the stock inrunner. Is there anyone out there still running the stock, and if so what are you propping it with?
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Old May 28, 2007, 01:15 PM
Live, Die, FLY
Kalispell, in the Rocky Mountains
Joined Jul 2006
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I still run stock. The prop I use is just parkzones brushless prop for it. I cant think of the dimentions off hand. Check there site.
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Old May 28, 2007, 01:35 PM
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Burnaby, BC, Canada
Joined Sep 2005
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Not really looking for the same prop. Was more wondering if anyone has tried to push the motor/esc combo by repropping to a different pitch or diameter to eke out a little more performance.
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Old May 28, 2007, 05:33 PM
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Western NY
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EP Dean -

The stock prop is about 5" or 6", you can measure it just to be certain. I'm not sure of the pitch, but I believe it is fairly low pitch, I'd guess around 4". A number of 5-6" APC electric props should work with the stock Stryker brushless motor, but I'd recommend keeping the pitch in the 4-5" range. You don't want to install a prop that will push the stock motor beyond its current/load capacity, as it could burn out. I'm assuming you are using a stock F-27C (brushless w/LiPo), and not the F-27B brushed version. If you're using the stock brushed motor, the prop would be smaller in both size and pitch than my "guesstimates" above.

I don't think you will get a definitive response on exact prop to use with the stock Stryker motor. It would be best for you to try a few different props (i.e. a 6x4, 5x4.75, 5.5x4.75, 6x5, etc.), and pay very close attention to the motor and battery temperature during some static bench testing. In other words, don't just install a new prop, throw your Stryker in the air, and roll the dice. Some have claimed that Graupner speed and/or CAM props draw less current than an APC of the same size/pitch. Take a look at the following link for a large variety of props, both APC and Graupner varieties - http://www.hobby-lobby.com/elecprop.htm

Graupner props are about 2x the cost of an APC, but they are well-made and VERY light-weight. I run a 7x7 Graupner speed on my custom F-27B Styrker with the Mega 16/25/4 and CC 35 ESC (2200mAh 4S LiPo), but that would be way too much prop for the stock motor.

I'm also not sure of the shaft size on the stock brushless inrunner motor. APC props come with adapters in order to accommodate various shaft diameters. Graupner props tend to be 4mm, 4.8/6mm, or 8mm, and do not include adapters.
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Old May 28, 2007, 07:50 PM
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West Chester, Ohio
Joined Nov 2006
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EP Dean, the stock prop is a 6x4 (at least with mines). I'm currently running that prop with my eflite 6, 40amp esc, and TP 2070extreme. Although it's definately faster and stronger than the stock setup, it's still not fast enough. I measured the static numbers yesturday and was quite surprised that it's only pushing ~ 27-28amp and 280 watts. So now I'm thinking to either prop up, go to 4s bat, or even go up in motor size. What props have you guys tried in reference to the eflite 6? I have tried some of the smaller (4.75x5.25 and so) higher pitched but not good results. Eric
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Old May 28, 2007, 09:03 PM
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Western NY
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Nice...my guessing work on the Stryker stock prop size was more accurate than usual...

I'm only pulling about 21-22 Amps with my Mega 16/25/4 setup (7x7 Graupner speed), but at ~310-320 watts WOT on the 4S LiPo. The Mega 16/25/4 turns the 7x7 Graupner at ~18,000 RPMs at WOT.

Missle - if that eflite 6 is rated to handle watts > 300, you might want to try a 4S battery. If you're looking for a significant increase in speed, it'll take a lot of extra watts to gain the extra mph. If you step up your prop and battery, the main concern becomes the load capacity of the motor.
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Old May 28, 2007, 10:21 PM
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Burnaby, BC, Canada
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thanks guys, time to stock up on some props and drive the wifey nuts with some high pitched bench testing
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Old May 28, 2007, 10:29 PM
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West Chester, Ohio
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rcnewb, thanks for the info. Actually it's rated for constant ~ 400 watts (40 amps) with peaks in the 42-45 range. Being that 99% of my motors are eflite, i'm not familiar with the numeric designations of your Mega motors. What king of limits do you have with the ones you've mentioned?
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Old May 29, 2007, 07:20 AM
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Western NY
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Missle -

From what I've read, the Mega 16/25/4 can spin a prop up to 55,000 RPMs - according to Mega's website, the motor has a max capacity of 25 amps. Espritmodel.com has more details on their product page - the max power for the 16/25/4 is 360 watts.

Here are the detailed specs on the 16/25/4 motor from Mega's website -
http://www.megamotorusa.com/BrushlessNew/ACn16-25-4.htm

In order to hit that 55,000 RPM mark, I'd probably have to toss in a really small prop and a REALLY large battery (> 6S) to stay within the amps limit. Since the Mega 16/25/4 has a fairly moderate amp limit, a 4S LiPo battery or larger should be considered a requirement when running this motor - technically, on a 6S battery, at 20 measly amps, you'd be pushing well over 400 watts into that motor, which is beyond its capacity.
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Old May 29, 2007, 11:00 AM
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West Chester, Ohio
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rcnewb- now the light bulb has finally gone off. I now understand why going to > 3s batt can really help (other than obvious higher voltage). The bad thing is that it really makes my delima that much more foggy. So, if the eflite 6 2700kv has a max amp of 40, it would seem better to try going up in prop size as opposed to going to a 4s batt. Im thinking this because the current TP2070E with the eflite 6 and a 6x4 prop is only pulling ~ 28amps @ ~ 10volts which means there's plenty of room to go up in diameter or pitch. The fog comes in when considering that the 4s would up the volts by ~ 2volts which would = a max increase of 5400rpm and therefore speed. Oh this is becoming too confusing. Should have stuck with the simple plug-&-play, but no had to have more speed!
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Old May 29, 2007, 11:37 AM
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West Chester, Ohio
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To add to my last post, I've taken a APC 7x6SF and cut it down to 6x6 (because the LHS didn't have any 6's > 4) so that I get more thrust (speed) without slowing down the prop (like I would with a 7" diameter). Motocalc calculates ~ 43amps at 400watts with a prop speed of 104mph. What do you guys think?
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Old May 29, 2007, 01:39 PM
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Western NY
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Missle -

You also have to account for the fact that a higher kv rating means much more current draw with a large prop. Motors with high kv ratings are typically more suitable for smaller, "racing" props used by pylon racers and combat planes. The high-kv version of the Mega motor that I have is the 16/25/3 - if I propped that motor up to a 7x7, it would probably melt down. The 16/25/4 has a kv rating that is on the lower end, and more internal resistance, so it'll turn a larger prop and use less current.

Considering the higher kv rating of your eflite 6, it is probably best to run a smaller prop for very high RPMs/top speed (unless you use a gear box), probably somewhere in the 5x5 range, give or take 1/4".
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Old May 29, 2007, 05:15 PM
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West Chester, Ohio
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rcnewb,
Let me start by thanking you for your kind assistance with this mess i've created. So I just got back from testing the above setup using a 6x6 prop (remember power readings were 40/400) of which she flew several passes (aprox 2 min) with some good speed (the best as of yet). I brought her in to test if motor was too hot of which she wasn't. Decided to put her right back in the air of which she took off good for about 75 feet and then just lost ALL power. She nose dived from about 75 feet and sat on mother earth fluttering like a beached whale (no offense to animal lovers). I unplugged the bat and replugged her in after a few minutes of which everything was working perfect. My guess is that the Eflite 40amp ESC overheated and momentarily shutdown (hence causing a loss of all power and not just motor) or the AR6000 rec overheated. Got home to bench test using the same electronics (with a charged TP2070E) and again power readings were 40/405 @ 9.73V. Decided to re-test using a spare Electrify 35amp ESC (with the same bat/prop ect.) of which the readings were 52/483 @ 9.08V.
So, long story short, my initial readings using the 6x4 and larger props were eronously low due to a defective Eflite ESC. As a side bar for you Eflite fans, I am a die-hard Eflite person as I've probably got over $1k in Eflite electronics to include motor, esc's, ect...I personally like it because the name says it all and the quality (electronics) is usually really good.
Back to my lesson(s) from rcnewb et al, I understand what your're saying about using a smaller prop due to the higher kv, but I thought that was the point of them making the 6 pole series with a max amp rating as high as 40? I will go and purchase another 40amp esc tonight and remeasure numbers using the smaller props as you've suggested.
Motocalc comes up with:
prop-5x4.75 = 33amp, 9.4V, 307watts, 84%effic, 27oz thrust, 104mph prop speed
prop-4.75x5.25 = 31amp, 9.5v, 297watts, 84%effic, 24oz thrust, 116mph prop speed
prop-6x4= 44amp, 8.9v, 389watts, 81%effic, 40oz thrust, 77mph prop speed

The weight is 24.8oz with everything in it (0.5oz glass, bat, motor, ect..). Does this mean I have to use at least a 5" diameter to be able to have high speed as well as good verticle (thrust vs weight)?
Sorry for the long story, but wanted to include as much for those that may follow with the same type of question. Eric
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