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Old Dec 28, 2011, 10:15 PM
2.3 D Hack Bradenton FL
frankjp's Avatar
Joined Dec 2010
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Some thoughts here.
Originally the the 88% restriction was to stop the timing squeal with the 16x8 xoar.
I haven't heard that until the 16x7 Aero naut and then only once. The 16x8 aero naut does it a lot. these are heavy props. Can these ESCs sample what it is trying to spin and adjust its timing or some other parameter as needed? Anybody real familiar with this Hobby Wing 100 amp ESC?
Also when these 3300 Sky's were new they had around 30m ohms internal resistance,,,today they are around 46-55m ohms. This is after after about 12-18 flts./bat. We may be right on the edge of not being able to use the 16x8 when the Bats are new. We have been all over the ESC timing range during static testing ,without any real definitive or consistent results. Seemed to just squeal less and less.
Frankjp
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Old Dec 28, 2011, 10:45 PM
2.3 D Hack Bradenton FL
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Joined Dec 2010
177 Posts
I just did a quick static run up of the 16x7 Aero-Naut
start v. 25.18 min V. 21.59 Thrust 5.85kg 83.85 amps 1852 watts Didn't get RPM
I expected it to squeal but it did not even when jamming full throttle.
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Last edited by frankjp; Dec 28, 2011 at 10:54 PM. Reason: Left out watts
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Old Dec 28, 2011, 10:49 PM
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Are you using the same ESC as Tom?
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Old Dec 28, 2011, 11:04 PM
2.3 D Hack Bradenton FL
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Quote:
Originally Posted by dead View Post
Are you using the same ESC as Tom?
Yes, this is the plane we did all the recent testing with.
Motrolfly with The K-Force 100 amp. ESC
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Old Dec 28, 2011, 11:07 PM
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How many amps did Ken say the Motrofly was good to? Seems to me likt he told me 80 amps but I could be wrong...
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Old Dec 28, 2011, 11:08 PM
2.3 D Hack Bradenton FL
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Quote:
Originally Posted by dead View Post
Are you using the same ESC as Tom?
No ,,not the same as what Tom is using in his plane. We both had timing issues though.
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Old Dec 28, 2011, 11:10 PM
Not as Good as The Kid
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Joined Sep 2009
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Dead.... It was Frank's plane and 100A K-Force ESC that was used for the flight test. We didn't use Tom's plane because of the 12% restriction, so his static test is on the same power setup.

This makes sense, Frank, because we know some people are having timing issues with higher C batteries, even with smaller props.

I'm just not sure it's a good idea to select a prop that requires we use older batteries, or batteries with low C ratings, or drain off some voltage from a fully charged battery before flying in order to make it work. But what you are saying makes sense.... and maybe Tom's ESC won't having timing issues anymore because his batteries now have about 20 flights on them and the slightly higher internal resistance is keeping current at a lower level than when everything was new.

21.56v is lower than anything we saw in the flight tests and is probably the reason for no squeal this time. 83A, even at static, is still higher than I think is acceptable, though.
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Old Dec 29, 2011, 09:56 AM
Not as Good as The Kid
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South Pasadena, FL
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Here is something else to think about. I listed to Tom’s comments, and transcribed the comments about the propeller’s ability to deliver sufficient airflow over the control surfaces during low speed harriers, the propeller’s raw WOT speed, and the propeller’s pull-out power, all from the pilot’s perspective. You can review the video to confirm this:

1 - Pull-out okay but not great, not a whole lot of vectored thrust and required a lot of throttle pulsing, but a decent speed prop.
2- A lot better than first, mid-range and low throttle had a lot better authority, airflow over the plane was a lot smoother, pull-out was a lot better.
3 - Airflow felt a lot smoother than one and two, low and mid-range was very good, pull-out was awesome, flew really nice.
5 - Not all that great in harriers, not much vectored thrust, had a lot of power at the top end, and a lot of pull-out power.
6 - Really fast speed prop, didn't have a whole lot of vectored thrust, pull-out wasn't the best I've seen, but actually kind of good in the middle.
7 - Pretty nice prop, really fast high speed, had a really good pull-out, didn't feel like it had a lot of vectored thrust, but plenty of thrust on the low end.
8 - Insane pull-out, had a lot of vectored thrust in harriers, very nice all around and one of the top three props so far.
9 - Really fast prop, didn't have a whole lot of pull-out or vectored thrust.
10 - Insane pull-out, really fast, not really sure about the vectored thrust because of changing wind conditions but okay.

With this in mind, I used a minus sign for comments that were not that good, plus signs for moderate comments like ‘good’, and decent’, and double-pluses for ‘really good’, ‘great’, ‘awesome’ and ‘insane’. I used these to create a points system and I was then able to divide his comments into three tiers.

The top tier contains the:
3 - 16x7 Aeronaut (6 points, 2.15G and 1654W)
8 – 16x7 Vox (6 points, 2.08G and 1421W)
10 – 16x8 Xoar (5 points, 2.17G and 1536W)

The second tier contains the:
2 – 16x7 Xoar (3 points, 2.08G and 1414W)
7 – 16x8 APC (3 points, 2.05G ND 1448W)

The bottom tier contains the:
5 - 15x8 Aeronaut (2 points and no data)
1 – 15x8 Xoar (1 points, 1.90G and 1242W)
9 – 15x8 Vox (0 points, 1.90G and 1393W)
6 – 15x8 APC (-1 points, 1.91G and 1338W)
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Old Dec 29, 2011, 10:30 AM
They Call him Dead!
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AP...One thing confuses me. The only thing I see that puts the Xoar 16 x 7 below the others is that he said the pull out was "good" instead of "Insane". But if you look at your time for pull out calculations the Xoar is #1. Also, if you watch the video, the Xoar seems to have extremely good pull out. Any thoughts?
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Old Dec 29, 2011, 11:02 AM
Not as Good as The Kid
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Quote:
Originally Posted by dead View Post
AP...One thing confuses me. The only thing I see that puts the Xoar 16 x 7 below the others is that he said the pull out was "good" instead of "Insane". But if you look at your time for pull out calculations the Xoar is #1. Also, if you watch the video, the Xoar seems to have extremely good pull out. Any thoughts?
Well, to keep from subjectively interpreting the data, I will say the data and Tom's comments speak for themselves, but I will also say the way I timed the pull-out is subjective in itself and I have an idea for redoing this. I'll post my findings when I'm done, but also consider this....

The 16x8 Xoar had the second best time, the best G-rating, the second best Watts reading with less Amps than the next closest competitor, and Tom has no plan to change from the 16x8 Xoar as far as I know, even after the testing and seeing the data. If the wind had not died and confused the harrier test, I think it may have ranked better in his review. From the data, and from his review, I would suggest trying several 16x7 props to see if he can now remove the restrictions from the ESC, getting a bit more power, less Amps, and eliminate the timing issue altogether.

It seems that this is the direction Frank is going in with his further static tests, and confirming this probability. The 83 Amps in his recent static test concern me, but this may extrapolate to about 70 Amps in the air, which means further in-flight tests are needed to confirm this.

Ken told me to keep it under 80 Amps and under 130 degrees F.

My holy grail is to find a prop that produces under 70A, heats up to under 110 degrees F, provides no timing squeal on a fully charged, 30C, new battery, and produces over 1500 Watts in the air and 2.10G's in a pull-out. I think this is all obtainable from what we have now seen.
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Old Dec 29, 2011, 03:31 PM
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USA, WA, Redmond
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Originally Posted by Aeroplayin View Post
Well, you did say about the 16x8 Xoar, "Insane pull-out, really fast..." and the wind dying changed the conditions making the harrier control test inconclusive, but yeah, you picked all the big wood electric props. From my data analysis of the vertical pull-out....

2 16x7 Xoar = 1.29 Seconds and 2.08 G
10 16x8 Xoar = 1.44 Seconds and 2.17 G
3 16x7 Aeronaut = 1.49 Seconds and 2.15 G
8 16x7 Vox = 1.57 Seconds and 2.08 G
7 16x8 APC = 1.60 Seconds and 2.05 G
6 15x8 APC = 1.62 Seconds and 1.91 G
1 15x8 Xoar = 1.64 Seconds and 1.90 G
9 15x8 Vox = 1.91 Seconds and 1.90 G

Hey, Lee... Check out the G values for the 15x8 Xoar, and Vox (the same). Then check out the G values on the 16x7 Xoar and Vox (the same). Hmmmmmm......

Hey Frank... I think we should have included the 16x8 Vox too. How's your back.... LOL!!
Simply stunning efforts and results Tom, Frank and Jim. This is the way props should be tested and eval'd. bench testing, flight testing is where it is at. You could clearly see the flight differences and performance results in the videos.

I knew the flight testing would bring some surprises. It appears Vox and Xoar are very similar if not the same, which contradicts my initial findings. This is why a second and sometimes a third independent test is an absolute must before reaching a solid finding.

It was my experience when testing the carbon Mejzlik 16X8 prop which weighed a whopping 81 grams that the squealing / timing issue could be somewhat mitigated by cross hatch sanding the back of the prop hub with 320 grit sandpaper. The smoother harder surface of the composite props don't seem to take as positive a bite into the prop adapter. In some cases this can cause a slippage between a heavy prop and the prop adapter when rapidly increasing the throttle to 100%.

I found that using a drill press to vertical cross drill the Aeronaut prop yielded some mass reduction and improved the on bench and in flight spool up. Insuring the right size diameter cross drilling, hole spacing, slow drill press plunge speed and careful prop rebalancing is paramount to insure prop integrity. Otherwise you could easily end up with a catastrophic mid flight fragmentation prop failure.

Again superb work. This is the way prop testing should be done!
If I lived closer I would take you guys to dinner on my dime.

Kindest Regards,
Speed
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Old Dec 29, 2011, 06:03 PM
They Call him Dead!
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Hey Lee,

Could you post a pic of that drilled out prop hub?
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Old Dec 29, 2011, 08:58 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 leespaddock View Post
If I lived closer I would take you guys to dinner on my dime.

Kindest Regards,
Speed
Thanks, Lee. Happy New Year, and maybe we'll all be able to get together someday. Frank, Tom, and I have spent several evenings at the local rib joint (the area's best ribs, IMO) rehashing test flights and data.

As for everyone else within striking distance of MCRC, it looks like we're going to have the 3D throwdown on January 28th, which is a Saturday. 3D pilots will have the flight line all day. This will be the second one we've had and we're expecting guys from around the state to make the annual 3D pilgrimage. I know for a fact that every EXP offered by EF will be in attendance and I will bring the entire selection of props for anyone to try on there plane.
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Old Dec 30, 2011, 02:23 PM
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USA, WA, Redmond
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Quote:
Originally Posted by dead View Post
Hey Lee,

Could you post a pic of that drilled out prop hub?
Here are a couple of pics of the vertical cross drilling and tip clipping I experimented with on the Mejzek 16x8 Carbon fiber Prop at 81grams. It yielded a 15x8 prop at 74 grams. The mass reduction and improved spool up on the bench. I only cross drilled the Aernaut 15x8 with no tip clipping and shed 5grams.

Again insuring the right size diameter cross drilling, hole spacing, slow drill press plunge speed and careful prop rebalancing is paramount to insure prop integrity. I am still nervous about the acuracy of my balancing because my prop balancer is static (in one plane with the prop stationary) verses a true dynamic balance (in three planes with the prop rotating).

Use caution if you employe this backyard method. Without careful attention to balancing detail you could easily end up with a catastrophic mid flight fragmentation prop failure.
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Old Dec 30, 2011, 11:36 PM
They Call him Dead!
YellowJacketsRC's Avatar
United States, SC, Pawleys Island
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Thanks For the Pics and Instructions!
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