|May 24, 2012, 04:50 PM|
I've broken a 7x10 on every landing so far with my Ninja. I have a stash!!
Still, a folder is starting to look attractive, if nothing else but for the convenience of not having to drill out a new prop and fit after each flight....
If only 7x10 folders were easy to get hold of....
|May 24, 2012, 06:22 PM|
That IS our problem Bro....PROPS...or should I say lack of them.
The 7x13's I have from Marcus are GREAT blades...however when you put them on a 45mm spinner they magically become 8x13's. The Monster 1.1 that is coming takes a 60mm spinner so add at least a half an inch.
My dream is a set of high pitched 6's or 6.5's...which puts us in the 7 to 7.5 inch territory with the spinner.
Sooner or later (after this next build) am going to shift attention to making molds and props. Will start by re-pitching APC's and making molds from them...long slow learning process (already started some reading) with lots of frustrations...but it might be worth it in the long run.
QUESTION for ya DownUnder - Do you have the "hard brake" set on the ESC or no brake. I was told awhile back that if you set the brake on the ESC it will be less likely to break the prop on landing. Haven't tried it yet.
|May 24, 2012, 06:28 PM|
Arctic the brake is set to soft - and the prop does actually windmill. My experience is that if the prop is freely spinning (or thereabouts) then it's less likely to break.
I might try turning the brake totally off and see what happens.
Funny, I'm thinking of trying to make my own props as well. Same size as you. Sooooo much to learn....
|May 24, 2012, 11:53 PM|
With my plans to run a 22/50ish motor on the front of the Ninja's firewall, it's going to put the prop even farther ahead of the firewall. The impact forces that are breaking your props, DUP, are going to be transferred along a longer lever, and transmit more force, to the plane's firewall and the backplate of the custom Mega.
Both these parts are going to have to be bulletproof to hold up.
Or if I'm too scared of busting up a firewall or motor backplate, I'll have to go with the traditional mounting route of putting the inrunner behind the firewall.
LOTS of this decision making is going to be affected by the experience Arcticflyer has with running his big inrunners at high power.
I don't know the power levels they can take in these applications. If the motor's power has to be choked down from 4000W to 3500W, that's not so bad. But if it has to run at half of "Stryker power" then I'll be more determined to mount the motor in front for extreme cooling.
This is groundbreaking!
|May 25, 2012, 12:07 AM|
I would think the force to break off an APC 7x10 (approx 1" off the tip) is never going to break your planned motor or firewall Murdo. They're quite thin at the tips. I bet I could break one mounted to a motor statically by just hitting it with a large screw driver!
|May 25, 2012, 12:29 AM|
Murdo - I am hoping to get the first flight in tomorrow with the NEU at 4S I opened up my cooling holes in the nose a bit more today and made some improvements to the vents. I realize now (hindsight 20/20) that getting heat out of the motor and plane is parmount for these larger planes and motors.
When the new Monster comes, that will be my first consideration of the build...where to put the scoops and where to put the vents. The goal for that plane is 250 (doesn't hurt to try) and it won't get there unless it can get rid of the HEAT. Should know tomorrow if I can go to 5S with this motor. It will all depend on the temp of the case when I land
Well I'll probably start breaking props tomorrow...should start buying some shares in APC. I don't think snapping props will hurt your motor...if you can get that thing on the outside in the air by all means do it!
|May 25, 2012, 08:52 AM|
That makes me feel a good deal better, DUP and Arctic.
I'll press on with the "outboard" install!
I can always get the large Megas in 8mm shaft, so the shaft is guaranteed to hold up to whatever potholes I can find in the field.
Are you guys keeping a close eye on the prop's position during the final landing glide? This is where having a strong brake comes in, as the position can be observed and the throttle blipped until the prop is close to horizontal.
A windmilling prop guarantees that at some point the prop will touch the ground, even if it's only to bump it out of the way, which may be causing the frequent tip breaks.
'Course, watching the prop only works if you can land close enough to SEE the prop!
|May 25, 2012, 11:20 AM|
I agree with this technique. On my pylon models with 5" props this is the method used and I rarely, if ever, break a prop. I would think it would be even more difficult to break a 7x10 because they are extra robust. I also used that method with a 6.5x10 (cut down APC) on a MEGA 16/40/2. This worked well except that the braking stuggled to stop the prop under initial deceleration (180+ mph). Once it slowed down to ~100 mph the prop would lock in place and you could do Murdo's method.
Murdo, I can't wait to see your Ninja. 8mm motor shaft? Is the whole motor a shaft!?! I think they call those outrunners (tongue in cheek, if the emoticon isn't obvious enough!)
|May 25, 2012, 02:15 PM|
Perfect Day...except for the Badger!
The only challenge at the field today as the weather was perfect was staying out of the Badger's way He kept a good eye on me and I kept a good eye on him
Beautiful day about 50F with very light variable winds. First flight with the NEU 1515/1Y. Decided on 4S with an APC 7X9. The launch was uneventful except without the strong winds of earlier in the week it took the wing a few more feet to really grab air...always a little scarybut it pulled away nicely. Noticable difference between the APC 7x9 and the 7x13 folders in the torque.
Here are the inflight numbers with (7) WOT passes over the camera (will get the speed later in the day when I get all the file conversions done and Waveoscoped).
Static at launch: 214Amps
In Flight passes at WOT: Amps 196.4 Max
Amps 183.6 Avg
Watts 2663 Max
Watts 2424 Avg
Volts 15 Max
Volts 14.3 Avg
RPM's 25,779 Max
RPM's 21,376 Avg
Good News: 124F motor case temp on landing! The cooling efforts are
working That means I believe this motor can go to 5S with
a 7x10 APC and not cook WE SHALL SEE!
Bad News: The ESC temps got higher than I wanted to see and as the ESC
is under the wing and behind the battery it is not getting the air
that it should
Bad News: First landing BROKE the PROP...I knew it
Good News: The Plane was SCREAMING
Did the Waveoscope and one of the passes was 180...slowly getting there
|May 25, 2012, 04:00 PM|
Be aware that the current draw of 7x10 is minimum 15% higher than a 7x9( which in my experience is much less effective).
At 5 S i would expect 300Amps+!
I have no experience with inrunners in this size so please try it and post results... but be carefull
Again good luck
I think i have to hurry up with my promised projekt!
|May 25, 2012, 04:28 PM|
Did you have another flight with the same battery and prop on the Neu where temps were higher than before the cooling mods?
Your greatly lower temperature may be due to not only the better cooling, but the increased efficiency of the Neu motor over the HET that got to 285F on less power.
|May 25, 2012, 05:28 PM|
I've got an experimental (no kidding) setup I'm planning to put in my X or similar airframe. My plan is to run "speedcup" style runs and maximise output in 6-8 second runs.
From static testing I got these data from the CC ICE log with the M. Koch 7x13 on a 38mm spinner and 5S:
This equals for a pitch speed (give and take a few) of:
What ammount of unloading can I expect from in-flite data vs. static and what will the real speed/pitch speed factor be?
OK I know it is hard to estimate, but any input is very much appreciated
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