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Nov 30, 2005, 09:25 PM
Motors beat engines!
Thread OP

gws's new brushless, too good to be true?


In my new Feb 2006 fly rc mag, page 18, they do a brief preview of the upcoming gws 400 bl. From the text:

28 mm diam
produces 56 oz thrust with 12x8 prop
price- $30

I the pic, it appears to be about 40mm long so its weight is likely about like the mega 16-15-xx series, so around 2.7 oz.

Heres the dilema. Per motocalc, to get 56 oz thrust from a 12x8 needs about 7400 rpm and 280 watts output .

Now, for $30, I can't imagine its got the best efficiency, but perhaps its in the mid 70's. So figuring 75% eff., you'de need about 370 watts input to get that 280 watt output, meaning the motors absorbing 90 watts.

This seems a whole lot for a sub 3 oz piece of metal to absorb without going into meltdown.

Thoughts here folks?

BTW, in the same blurb, they also mention a upcoming gws 480 bl thats supposed to do 70 oz thrust. $35!


Dean in Milwaukee
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Nov 30, 2005, 09:43 PM
phillyphly
e-guru's Avatar
I doubt the veracity of the original numbers at any price - no way for 30 bucks. But then again, nobody thought GWS could really change the face of parkflying either!

Here's to hoping...
Dec 01, 2005, 01:11 AM
Registered User
galloping gimp's Avatar
GWS Brushless Motors...testing begins.

In the above thread, GWS' Mr. Lin says:

The GWS BL motor price in USA market:

2015 ( short 200 ): $20
2028 ( long 250 ): $25

2815 ( short 400 )$30
2825 ( long 480 ) $35


So it looks like there will be at least four GWS brushless motors.

- Jeff
Last edited by galloping gimp; Dec 01, 2005 at 01:20 AM.
Dec 01, 2005, 04:16 AM
Ay up it's warped
mtbrider's Avatar
It would be nice if we can get them at a similar price over here, the thread GG possted is going wild on the GWS site
Dec 01, 2005, 06:19 AM
Registered User
vintage1's Avatar
Ability to handle power depends on efficiency.

A 90% efficient motor will handle three times the power of a 70% one of the same size.

I would say the figures are probably about right...but tests and use will establish it.

There is no reapon why outrunner type motors (are these outrunners) should not be, in volume, cheaper than can motors of similar materials (no ball races, cheap ferrite magnets)

Whether the similar poor efficiencies and the extra cost of a brushless ESC is worth it is a moot point.
Dec 01, 2005, 06:48 AM
Registered User
yeah i'm holding my breath.... an outrunner is just some decent magnets, a couple of ball races, a squirrel cage or "flux ring", stator and some copper wire and a few other sundry bits and bobs...

add to that a clever design which is a once off expence and away you go ... it really shouldn't have to cost the earth ... especially when you are producing in Asia

look at the price kit motors go for... and they are a very small market.

my guess is they'll get over 80% effeciency ...how much over is the burning question

this could be good

big bird
Dec 01, 2005, 09:07 AM
Closed Account
I'll believe the motor numbers when Dr. Kiwi gets his hands on them.

Until then.......
Dec 01, 2005, 09:08 AM
Motors beat engines!
Thread OP
Quote:
Originally Posted by vintage1
Ability to handle power depends on efficiency.

A 90% efficient motor will handle three times the power of a 70% one of the same size.

I would say the figures are probably about right...but tests and use will establish it.

There is no reapon why outrunner type motors (are these outrunners) should not be, in volume, cheaper than can motors of similar materials (no ball races, cheap ferrite magnets)

.

They are inrunners, although a small outrunner is planned too.

From the thread referenced above here:

Data for 2028-4
KV rating 3900
Ratio 6.6:1
Prop amps Thrust in g (oz.)
1147 7.4 573 (20.21)
1180 10.6 666 (23.49)
1260 11.1 834 (29.41)

I ran motocalc on the 12x6, looks like it would take roughly 93 watts out and 5600 rpm to achieve, so based on a nominal 3.7v/cell under load, 11.1x11.1 = 123 watts in on that test for about a 76% eff.

It sure would be nice if they would post rpms and watts.

Also, from elsewhere in that thread, an actual weight :

"Here's some pics of the 4600KV motor. I should have some gearbox and EDF data soon. Weight is 1.76oz compared to the Himax 2025 2.26oz"



Dean in Milwaukee
Dec 01, 2005, 12:16 PM
Scratch builder
Has Mr. Lin been spot on in the past?
Dec 01, 2005, 12:21 PM
My Bulldog is my copilot ..
TheLost's Avatar


(picture taken from GWS's website).
Dec 01, 2005, 12:38 PM
Balsa just crashes better
Cub Fan's Avatar

Test versions


One of my friends got four to test ( he is a GWS Dealer)
They are 1014 pt numbers- 20 MM dia in-runners but also show BR-2028 part numbers
PKMOT-1014 shows KV-4600 BR-2028-3
PKMOT-1014-A KV-3900 BR-2028-4
PKMOT-1014-B KV-3000 BR-2028-5
PKMOT-1014-C KV-2300 BR-2028-6
Thats the only info/specs I have so far - all these appear to fit in the GWS gear box
We are going to try the KV-3900 in a Formosa in the next few days- replacing a 350 BB brushed motor. I will let you know how that works out
Dec 01, 2005, 12:46 PM
Registered User
galloping gimp's Avatar
Quote:
Originally Posted by KenSt
Has Mr. Lin been spot on in the past?
Mr. Lin is the president of GWS, so he's in a position to know! I think he sometimes exaggerates a bit (also known as "marketing"), but overall he seems like a good guy.

One thing for sure, the experts on this forum will ruthlessly test every claim GWS makes. We're very fortunate in that respect.

- Jeff
Dec 01, 2005, 01:44 PM
Master of 1 point landing
Quote:
Originally Posted by DeaninMilwaukee
In my new Feb 2006 fly rc mag, page 18, they do a brief preview of the upcoming gws 400 bl. From the text:

28 mm diam
produces 56 oz thrust with 12x8 prop
price- $30

I the pic, it appears to be about 40mm long so its weight is likely about like the mega 16-15-xx series, so around 2.7 oz.

Heres the dilema. Per motocalc, to get 56 oz thrust from a 12x8 needs about 7400 rpm and 280 watts output .

Now, for $30, I can't imagine its got the best efficiency, but perhaps its in the mid 70's. So figuring 75% eff., you'de need about 370 watts input to get that 280 watt output, meaning the motors absorbing 90 watts.

This seems a whole lot for a sub 3 oz piece of metal to absorb without going into meltdown.

Thoughts here folks?

BTW, in the same blurb, they also mention a upcoming gws 480 bl thats supposed to do 70 oz thrust. $35!


Dean in Milwaukee
You considered that those guesstimates are in a gearbox right?
Dec 01, 2005, 01:57 PM
Motors beat engines!
Thread OP
Quote:
Originally Posted by ImaBiggles
You considered that those guesstimates are in a gearbox right?

Yes, but for the math, it does'nt matter. I put int a 12x8 apc prop, and inputted a large motor that could turn it far faster, and throttled back till I got the correct thrust, then took rpms and watts out. That gave me the amount of output watts any motor/gearbox combo would need to produce to turn that prop that rpm.

Then it was just a matter of working backwards with eff. estimates to get approx. watts in.


Dean
Dec 01, 2005, 02:32 PM
Lori, hey, you're home early
CarreraGTSCS's Avatar
When are these supposed to be available?
Mike


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