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Old Aug 14, 2011, 11:40 AM
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Oh agreed! As motor and battery tech improves, higher rpms are achievable and with the given materials used for motor shafts, reduces the potential for deformation and failure because it is supported on both ends.

This even dampens vibration. And if they balance these at the factory motor to fan, it just that much easie to the end user.
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Old Aug 16, 2011, 07:46 AM
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Oh agreed! As motor and battery tech improves, higher rpms are achievable and with the given materials used for motor shafts, reduces the potential for deformation and failure because it is supported on both ends.

This even dampens vibration. And if they balance these at the factory motor to fan, it just that much easie to the end user.
Even Mercury 64 EDF's motor shaft is supported on both ends.
To get more smooth rotation.
Motor shaft was made by hardening process to get high rigidity to prevent deformation.
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Old Aug 16, 2011, 12:45 PM
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I agree with you but are you going 5mm ... 8mm shafts.
Its not just the initial balancing I'm concerned with. Its the heavy landings that can easily bend even the 5mm shaft (now carrying a heavier fan at much closer tolerances) if you spool up as you touch down.
The same concern was posed with Machs 90 since they have the forward guard why not place a thrust bearing to safe guard this. However, it changes the price and weight to an already heavy and expensive assembly.

So the motors shaft size may become a future focus.
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Old Aug 16, 2011, 12:58 PM
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The fact its supported at both ends, with the supports only a very small distance apart, means flex is almost zero. Certainly far less than a conventional layout where, even if perfectly balanced, gyroscopic forces cause vibration / flex.
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Old Aug 16, 2011, 01:22 PM
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We are in agreement; but they went smaller on the 64 so I'm curious if they did the same for the 70 and 90 and are depending on the extra bearing or if they also beefed up the shaft as well.
I'm not even certain which is the better of the two but curious as to what they decided. Both I guess may be best.
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Old Aug 16, 2011, 02:24 PM
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Guess well find out soon.
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Old Aug 17, 2011, 06:51 PM
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I agree with you but are you going 5mm ... 8mm shafts.
Its not just the initial balancing I'm concerned with. Its the heavy landings that can easily bend even the 5mm shaft (now carrying a heavier fan at much closer tolerances) if you spool up as you touch down.
The same concern was posed with Machs 90 since they have the forward guard why not place a thrust bearing to safe guard this. However, it changes the price and weight to an already heavy and expensive assembly.

So the motors shaft size may become a future focus.
Most of user just know the unbalance will bend the shaft.
Forget another force is Gyro effect.
(You are a master)
As we knew, EDF will like a mechanical Gyro while high speed rotation.
Let's think.
What is happen while heavy landing.
Both fan and motor will give a shaft a same direction impact force to bend the saft on front / rear of fulcrum.
Then, they will keep this status rotation for a while.
Gyro effect makes unbalance wrose.
(You will know what I say if you had experience to hold a gyro toy on your hand before)
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Old Aug 18, 2011, 11:01 AM
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Well Devon partly yes. The forces do exist as you show but they translate to the weakest point. Its like make a car chassis rigid and all the many forces gets translated to your body in the event of an impact.

Because there are two bearing in a motor, the shaft within the motor is usually intact though it carries the heavy magnets. Shock is absorbed by the bearings and the motor housing and mount.

On the fan side of the fulcrum or beyond where the motor mounts, there is no support other than the shaft itself. Thus impact forces are not dampened and are supported only by the integrity of the shaft. Because the shock on the motor side is taken by the entire motor, much of its energy ripples out back to the EDF housing amplifying the shock to beyond the fulcrum or mount. So much of the force gets focused at the fan and at high rpm with enough slight flex to out of balance the shaft, this can induce the shaft to fail.
Previously not a big deal with the much lighter fans of CF or Composite. But now the fans are becoming much heavier made of alloy and are thus more susceptible if the previous specs remain.

If a bearing is forward of the fan supported by a stators or a straight vain like on the 90 mach, then the impact force gets more evenly distributed to the entire assembly.
I think that was the advantage of your design that you were trying to describe. The other avenue is just mak the shaft thicker, which also can make it the heavier option than just the bearing.

To me though, of great concern is by making higher powered and heavier fans, if the energy needed to drive them and the weight to drive it increases significantly, you basically are making a 70mm perform like a 90 or 100 but it still has the weight of a 90 or 100 making that very powerful 70 no longer useful to its class because the size model that you would put it in may no longer be able to fly it as well or for even shorter flights.

Big challenge because if the weight can't be kept down, in a system that needs more weight to reinforce its higher power level or more expensive and exotic materials to support such; it will be interesting to see if it actually is a good trade off.

Like SMorrisRC said.... will just have to wait and see.
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Old Aug 18, 2011, 12:33 PM
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Mine are here!!!!
Wow, I want to put them on display.......
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Old Aug 18, 2011, 12:35 PM
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Old Aug 18, 2011, 01:20 PM
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What are you waiting for.... fire em up and post the real world figures

MERCURY 64A 3700KV (2~5S LiPo) actual weight.
Result:
@Voltage, Amps = Watts, Thrust


I've been told I've been bumped to the end of Aug. And the order number mismatch hasn't been corrected on the account either.
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Old Aug 18, 2011, 02:12 PM
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Their actual weight is correct. About 160g.
I put two in my pak to test, but I don't have a suitable battery as I'm waiting on XPS to replace a 65c that puffed instantly. I've run them up on a wholly unsuitable 4s 4000mah 25c, thrust (for two, installed) about 2.1kg. Also ran on a 5s, 3000mah, 30c (again, not up to the job). The 2kg pak hovered at 60% throttle. I got scared after that.
Haven't played with timing either yet, but my word do they sound great!
Will get them on the wattmeter when I've soldered up a suitable battery adapter.
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Old Aug 18, 2011, 05:24 PM
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To me though, of great concern is by making higher powered and heavier fans, if the energy needed to drive them and the weight to drive it increases significantly, you basically are making a 70mm perform like a 90 or 100 but it still has the weight of a 90 or 100 making that very powerful 70 no longer useful to its class because the size model that you would put it in may no longer be able to fly it as well or for even shorter flights.
Big challenge because if the weight can't be kept down, in a system that needs more weight to reinforce its higher power level or more expensive and exotic materials to support such; it will be interesting to see if it actually is a good trade off.
Exactly what I have been conveying to people for years, whats the point of trying to get 3kg thrust from a 70mm fan if it takes crazy watts and huge batteries to do it? 2.5kg at 87A on 6s is right up there as it is for weight carried in a 70mm model, and its not strength thats the issue, its wing loading, having flown heavy and lighter versions of the same aircraft I can say categorically that the heavier higher loaded airframes are NOT enjoyable to fly period.
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Old Aug 18, 2011, 05:30 PM
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With regards to shaft failures, I have not personally bent a 5mm shaft, and never had a 90mm fan run badly enough to do so. Nor have I damaged a shaft from a hard landing, talking like this is only going to cause fear mongering through the thousands of unheard readers in here who often take what is written as gospel.

Supporting the shaft at the end does seem logical, but it would be prudent to have the numbers crunched first before we accept it as necessary.

The Wemotec rotors are light as are the HET, schubeler, Vasa, a fan running in perfect or near perfect balance should not cause failure of the shaft. Same thing with this "8mm shafts are better in 90mm fans" being pushed lately, maybe for fans with very heavy rotors, but if the shaft adapter fits tight and is extremely high quality like the wemotec are, I dont see the issue with 5mm shafts. I can fit a wemo adapter to any 5mm shaft and tighten hell outa the set screws, the adapter does not get kicked offline, its extremely rare to have one run out of true. Look at the wemo adapters, the quality of materials and machining is evident. They also use a hardened alloy nut and a shim washer that is paper thin and weighs nothing. Its attention to detail like this that separates a wemo from say a lander fan by a large margin.
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Old Aug 18, 2011, 05:44 PM
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Gorgeous
Just remind you do not forget to apply some threadlocker on 4pcs screw on nose cone and tail nozzle thread before setup into your plane.(they shown on the install manu).
Due to some users like to setup in hide wire mode( wires come out hub).
So we don't apply threadlocker on them before exist factory.
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