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Old Jun 05, 2012, 05:53 AM
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One more thought on a high kV motor conversion...maybe crazy or stupid but her goes.

What if a 16 p rotor was converted to 8 p. Two N followed by two S magnets?
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Old Jun 05, 2012, 06:14 AM
Jack
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The comment on the table "nur fur speed" means "best for speed" so I assume that it means that it is the potentially fastest wind (highest RPM). You want to keep the magnet coverage below 100%, I think 80% or so has been mentioned as good so each magnet pair should only have a width of about 10% or so of the I.D. of the housing.

Jack
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Old Jun 05, 2012, 07:00 AM
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Originally Posted by jackerbes View Post
The comment on the table "nur fur speed" means "best for speed" so I assume that it means that it is the potentially fastest wind (highest RPM). You want to keep the magnet coverage below 100%, I think 80% or so has been mentioned as good so each magnet pair should only have a width of about 10% or so of the I.D. of the housing.

Jack
So the 12 tooth 8p with an ABC wind might be a good option base on the page you posted.

Here is the translated page from Google translator
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Old Jun 05, 2012, 10:31 AM
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Quote:
Originally Posted by leadfeather View Post
One more thought on a high kV motor conversion...maybe crazy or stupid but her goes.

What if a 16 p rotor was converted to 8 p. Two N followed by two S magnets?
When I did that.. I asked, and the Good Doctor suggested a multiplication factor of 1.73 (?) on the kv would result.. Seemed plausible as I'm inumerate..
Certainly the re magged Motor did go 'much' faster .
Do be careful in setting up those few mags re balance and position... and that the bearings are healthy.
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Old Jun 05, 2012, 11:40 AM
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Even 120-125mph is pushing it on 14p even with a slippery airframe and a castle esc. There isn't a whole lot of info on making a 10p rotor. I sorta wing it using printouts of pie charts to line up the magnets; works surprisingly well actually. The old magnets usually pop right out with a knife... same with all the glue residue left in the rotor after removing them. It's very important to get every last bit of glue out of the way so you don't end up with a proud magnet that hits the stator later on. I use rubberized CA to glue the mags back in (IC2000). The wind options will be dLRK. The Kv's are like 14P scaled by a factor of around 1.23 (YMMV, but should be in that range). So say you have a 12T-14p motor that tests out to 2800Kv... if you were to just modify the rotor for 10p without rewinding, you'd end up with 1.23 * 2800Kv = 3530Kv.

With a 10p red'n'black in my Eclipse I was able to achieve nonstop 135mph throughout a 2-3min flight. My Phx35 esc still had LVC cutoffs at least 3-5 times per flight, but that is to be expected when you're piping 300W and 30kRPM through a 25gm motor. Sometimes when I ramped up the throttle the LVC would kick in (never run in soft cutoff). The cutoffs happen more when you ramp throttle up slowly, or spend lots of time cruising at 1/2 throttle. The LVC's aren't a safety issue, since a short blip of power is enough to send most speedsters around the field twice, LOL! So it's a hardcore on/off speed only deal... not good for aerobatics or general goofing around... speed hats only. Once you see your micro racer zipping by with a good 10P at full song the first time, any esc cutoffs you deal will be well worth it.

FYI, my Eclipse was randomly taken out by a ~200mph head on midair collision with a funfighter... on the day of the lunar eclipse last month. Talk about fate! The debris from the freak accident scattered across 100yds of tall grass. I lost my motor, nanotech pack, and castle 25; only found the Rx and servos. I have to get back in the saddle soon and do a few more 10P motors... still haven't finished my PBR motor.

Kev
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Old Jun 05, 2012, 11:47 AM
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Originally Posted by leadfeather View Post
So the 12 tooth 8p with an ABC wind might be a good option base on the page you posted.

Here is the translated page from Google translator
I've thought of trying 8p as a natural progression from 10p.

Quote:
Originally Posted by Bare View Post
When I did that.. I asked, and the Good Doctor suggested a multiplication factor of 1.73 (?) on the kv would result.. Seemed plausible as I'm inumerate..
Certainly the re magged Motor did go 'much' faster .
Do be careful in setting up those few mags re balance and position... and that the bearings are healthy.
1.73 sounds about right, but the actual number won't be the same for all motors. Theoretically it should be 2.0, but at higher RPM you get more 'no-load losses' that bring it down a tad. I noticed the same thing going from 14p to 10p; should be a factor of 1.4, but actually tested out around 1.23. I'm curious, at the kinds of RPM's we're talking about here (30k+), if NSN... or NNSSNN... would work better? I'll guess that eddy currents win, and the NSN makes a more efficient 8p wonder, but that's just guessing.

Kev
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Old Jun 05, 2012, 01:40 PM
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Kev,

The results you obtained with your Eclipse is one of the best examples I've seen of very good RC power train and airframe engineering...in the sense of accomplishing a lot (of speed) with so little (motor/weight).

I think I've convinced myself to try the 8p with the same wind (8t 23g) hooked up as Y instead of delta. I'm going to try the NN SS magnet arrangement. This is just based on my gut feeling that there will be more magnetic strength (less saturation or whatever) than with half the magnets.

Sorry to here about the midair...but it would have made spectacular video!
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Last edited by leadfeather; Jun 05, 2012 at 03:16 PM. Reason: typo
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Old Jun 05, 2012, 02:56 PM
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Sweet LF, I look forward to hearing about your results with 8p! It's a battle between saturation, eddy currents, and any effects that doubled mags may have on the esc's ability to keep timing... only testing will tell.

I do wish I still had the Eclipse around to fly last weekend, but at the same time I couldn't have asked for a better ending... other than not having it on video. I learned a lot from that project, and plan to use that knowledge to make an improved Eclipse v2, which I won't fly during an eclipse of any sort.

Kev
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Old Jun 06, 2012, 08:51 PM
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Originally Posted by Truglodite View Post
Sweet LF, I look forward to hearing about your results with 8p! It's a battle between saturation, eddy currents, and any effects that doubled mags may have on the esc's ability to keep timing... only testing will tell.

I do wish I still had the Eclipse around to fly last weekend, but at the same time I couldn't have asked for a better ending... other than not having it on video. I learned a lot from that project, and plan to use that knowledge to make an improved Eclipse v2, which I won't fly during an eclipse of any sort.

Kev
What is that green mangled looking thing?

I'm having a hard time getting the magnets loose from the rotor to do the 8p conversion; can't get any to pop free. Any tips?
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Old Jun 07, 2012, 02:52 AM
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Yes

Soak the bell in Acetone for a few hours

I had a NN, SS NN ,SS setup done but the wind did not work , so I changed to stock magnet configuration ,

The magnets are very wide doing it NN,SS, NN,,,,,,,, will it really run like that ,

of course the Kv would be real high
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Old Jun 07, 2012, 06:32 AM
Jack
USA, ME, Ellsworth
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Originally Posted by leadfeather View Post
What is that green mangled looking thing?

I'm having a hard time getting the magnets loose from the rotor to do the 8p conversion; can't get any to pop free. Any tips?
The acetone soak will help, on two pieces that are (probably) CA glued together like that you can take a thin exacto blade like a #15 and work it in between the magnet and the housing and sometimes it will pop the joint. Of course the "pop free" thing does not account for the annoying things that magnets will want to do.

And don't stab yourself with the eXacto knife! There are no bonus points for that!

Jack
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Old Jun 07, 2012, 07:44 AM
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Lead feather

That green mangled thing is Trugs plane,,,,,, see it below his name

Amazing minimum plane , low drag very light and oh so fast , there is a downside , these type are hard to see in the air and you can get disorientated very fast
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Old Jun 07, 2012, 10:40 AM
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Originally Posted by Bare View Post
... and the Good Doctor suggested a multiplication factor of 1.73 (?) on the kv would result. ...
= sqrt(3) = Kv multiplicationfactor when going from star to delta.

Going from 16 to 8 magnetpoles will roughly double Kv and reverse motor rotation. Ditto LRK and it's variants, going from 14 to 10 magnetpoles will reverse rotation, and give a 40% Kv increase.

Vriendelijke groeten Ron
diy motor tips • Get a life ... get a 3$ Wattmeter
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Old Jun 07, 2012, 10:41 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
The Netherlands, GE, Nijmegen
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Quote:
Originally Posted by Bare View Post
... and the Good Doctor suggested a multiplication factor of 1.73 (?) on the kv would result. ...
= sqrt(3) = Kv multiplicationfactor when going from delta to star.

Going from 16 to 8 magnetpoles will roughly double Kv and reverse motor rotation.


Vriendelijke groeten Ron
diy motor tips Get a life ... get a 3$ Wattmeter
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Old Jun 07, 2012, 11:55 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Boy, you can say that again!

Jack
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