Still a question on "watt per pound" rule of thumb

[Raven]

@trailblazer: Check out the below link on how to test. Post #10

http://www.daddyhobby.com/forum/showthread.php?t=52557

@Edmond: Ya man... bro remember wad we were joking abt in msn this afternoon. I got all the "test subject" prep and ready liao.


Rgds

[Babylon5]

B5,

If you check the Highendrc site http://www.highendrc.com/index_eprod...products_id=80

They listed it even higher rating of 65 amp vs 50 as shown on RC-warbirds. Since you have the motor, have a bit more faith in it and enjoy it.

Yes the rating is 1100watt. That is if the motor is in an ideal condition. The max rating of the motor is done in an ideal condition probably in a lab at 25 deg C. In reality the environment in which we usually operate the motors in the tropics are in an open field maybe in the hot sun where the ambient temperature over 25 degrees.
Moreover in a EDF or if the motors are covered by a cowling, the ventilation are definitely restricted. I always take the max rating of any motors with a "pinch of salt'. In such a harsher environment de-rating is applied.



Cheers

[edmond22]

Yes the rating is 1100watt. That is if the motor is in an ideal condition. The max rating of the motor is done in an ideal condition probably in a lab at 25 deg C. In reality the environment in which we usually operate the motors in the tropics are in an open field maybe in the hot sun where the ambient temperature over 25 degrees.
Moreover in a EDF or if the motors are covered by a cowling, the ventilation are definitely restricted. I always take the max rating of any motors with a "pinch of salt'. In such a harsher environment de-rating is applied.



Cheers

B5,

After your first sentence, the rest are all speculations. I am not interested to debate this with you further. You sounded like you are the developer of that motor when you are not!

Even when people design packaging, people do drop test. Lab with 25 deg? Stop misleading people please!

[RC-Warbirds]

Yes the rating is 1100watt. That is if the motor is in an ideal condition. The max rating of the motor is done in an ideal condition probably in a lab at 25 deg C. In reality the environment in which we usually operate the motors in the tropics are in an open field maybe in the hot sun where the ambient temperature over 25 degrees.
Moreover in a EDF or if the motors are covered by a cowling, the ventilation are definitely restricted. I always take the max rating of any motors with a "pinch of salt'. In such a harsher environment de-rating is applied.
Cheers

Hi Babylon,

the motor is tested and rated for 1.1kw by HET-RC.
HET Motors are tested by the factory and later again verified by HET dealers such as us (I don't have a lab.... )

I have plenty of customers pushing this limit without trouble.
Just make sure you install it correctly, use the heat sink ring and use a high quality fan for the correct size (70mm).

From experience I can tell you that most new HET motors when they first come out, are actually rated lower to keep a safety buffer. Over time, as dealer and customer feedback comes, in these values are then corrected upwards.


Regarding your setup:
I remember that you mentioned that you want to install the motor in a 90mm Fan. As I said in my email I would not recommend that as this motor is intended for 70mm fan units only. Larger motors with more mass are recommended for 90mm units as the torque requirements are much different to a 70mm fan unit.

Please do not hesitate to contact me via PM or email if you need more info.

cheers,
Eric

[Raven]

My guess I think he screw up the "pwee tub due amp" settings that's why he's screwing up all his readings and murdering the motors.

After reading the post, I had a dream last night. I dream of polar bears and penguins dress in lab coats doing bench test on HET motors in Antartica. gosh... i cant find a polar bear smiley icon.

@trail blazer: Go for 6s and tsunami 72amp esc for your 2w25

[trailblazer]

i still have quite some testing and assembling to do for my set-up

it'll definitely be awhile b4 it flyable. Anyways, the airframe is vibrating very heavily when on of the motor's running.

Will have to check it out again.

[edmond22]

i still have quite some testing and assembling to do for my set-up

it'll definitely be awhile b4 it flyable. Anyways, the airframe is vibrating very heavily when on of the motor's running.

Will have to check it out again.

What plane?

[trailblazer]

What plane?

HET F-15..

I'm gonna have to strip out the whole motor set-up... can't risk the vibrations. one of the fan unit is sounding very wrong also.

Maybe re-do everything again.. which is not a big problem

[Babylon5]

Hi Bro, I trust RC-Warbirds and Typhoon's claim of 1100 watt rating. See attachment. I have a 2w30, no heatsink (does have the ring though), using 6s and from experience can say the setup is pretty conservative, no where near pushing the Jeti Spin66 ESC or motor temp. I would think the 2w25's slightly hotter KV will be ok. I mean to each his own really, you dun think it can take more than 1kw of power while I have already zipped around above 100mph at 1kw for Typhoon motors for a long time already, zero incident.

I dun normally include efficiency calculations because IMO, they serve no real purpose other than confuse you further. Just take the max max power reachable and make sure you are within limits. So when I say 1100watt, in reality, it will be 1000++ or even lower.

Hi brother, the ring that comes with the motor is not a heat sink. Look at it carefully it is a kind of sleeving only as a fitting adapter. Putting the ring over the motor will make it run hotter in a tight space.

In my past I have design heat sink and I can tell you the ring is not a proper heat sink or even a heat sink at all.

The other point i want make is , if you run 1kW(which is below its max) of power on the HET motor, 13 % is converted to mostly heat and friction...that is translated over 100watts of heat.


If this motor is use in the EDF and depending on the EDF housing, only 50 to 60 percent surface body is expose to the air blast. The motor will run very hot and overtime will de-magnetise the magnet.
( Since it did not happen to your setup yet ,good for you but I am not taking chances). Moreover, each setup is different and I am more conservative.

My rule of the thumb regarding input power is to apply the de-rating power specification.
Operating 75% or lower of the max power is my starting point.
Just my friendly advise.


Cheers

[Babylon5]

Hi Babylon,

the motor is tested and rated for 1.1kw by HET-RC.
HET Motors are tested by the factory and later again verified by HET dealers such as us (I don't have a lab.... )

I have plenty of customers pushing this limit without trouble.
Just make sure you install it correctly, use the heat sink ring and use a high quality fan for the correct size (70mm).

From experience I can tell you that most new HET motors when they first come out, are actually rated lower to keep a safety buffer. Over time, as dealer and customer feedback comes, in these values are then corrected upwards.



Regarding your setup:
I remember that you mentioned that you want to install the motor in a 90mm Fan. As I said in my email I would not recommend that as this motor is intended for 70mm fan units only. Larger motors with more mass are recommended for 90mm units as the torque requirements are much different to a 70mm fan unit.

Please do not hesitate to contact me via PM or email if you need more info.

cheers,
Eric

Hi Eric , I fully understand the factory testing. I have talk to few vendor regarding max rating. my own company product also has max limit. Most of it is on ideal cases and very competative rated...if factory choose to spec too loosely the factory loses to competition product. ..too tight high failure rate , its a balance .

On the 90mm fan , I use 4cells and the max current will average around 58amps after about 20-30 seconds so it is below the max rating.
It does not matter if it is for 70 mm of 90mm, its the current loading that makes up most of the heat.
I will tried measured the case temperating under this condition.

For EDF application after you put the motor in the Housing , only 50 to 60 % of the motor is expose to the air flow. I have tested the motor on a 800 watts setup, it is running pretty hot and have not run it at full power but I like been conservative. I had some motor de-magnetise because of operating at or near its limit(not the HET motor). Some of this motor comes with impressive heat sink with fin but cannot make it.
I do not mean it will happen to HET motor but am just been conservative. In addition, I like the HET motor to have long service life.



By the way , regarding the HET motor would like to know the type of magnet use. eg samarium cobalt or neodynium pls PM me.


regards
Andrew

[edmond22]

Hi brother, the ring that comes with the motor is not a heat sink. Look at it carefully it is a kind of sleeving only as a fitting adapter. Putting the ring over the motor will make it run hotter in a tight space.

In my past I have design heat sink and I can tell you the ring is not a proper heat sink or even a heat sink at all.

The other point i want make is , if you run 1kW(which is below its max) of power on the HET motor, 13 % is converted to mostly heat and friction...that is translated over 100watts of heat.


If this motor is use in the EDF and depending on the EDF housing, only 50 to 60 percent surface body is expose to the air blast. The motor will run very hot and overtime will de-magnetise the magnet.
( Since it did not happen to your setup yet ,good for you but I am not taking chances). Moreover, each setup is different and I am more conservative.

My rule of the thumb regarding input power is to apply the de-rating power specification.
Operating 75% or lower of the max power is my starting point.
Just my friendly advise.


Cheers

Your first and second para is explaining to me that the ring is not a heatsink. Can you tell me why? I dun recall asking about heatsink or saying the ring is one.

The rest of your message is base on your opinion. While you are entitled to yours, try to remember HET probably sold more motors than you can type now and there are already countless applications out there with this motor. besides your own know how, you should at least google what the RC world have done with this motor. Since 2007, people are reporting 1185watts for 58 amps and settles held at 1160 for 55 amps on a cc80. That was 3 years ago, more than enough material are online for you to make an informed decision.

This means before you even considered buying this motor, people have already bought it, used it, flown it, owned it, sold it around the world. It is good you made it clear you did not mean the HET motor in your reply to Eric but remember you did make a statement about that particular motor not being able to take more than 800 watts. I feel that is an unfair statement made without basis. We were all addressing you on that statement, nothing more.

I appreciate your explanation on the housing, heat transfer and all etc etc. But I think you should take into account my background too, I am not exactly a beginner or intermediate for you to patronise. You try finding another fellow here that has dabbled in 12s 3.5kw heli 3D, 250amp draw on cc180 3.7kw F5B, 2.7kw 23% electric plane 3D, 1.3kw EDF all at the same time. I haven't even talk about flying style yet which I think you will find it challenging if I ask you follow my flying routine monkey see monkey do in each category, you will know then who is really pushing the limits of their systems. I am not saying you know less, but the quality of your debate is just not there for someone like me with that background.

I done them all and the trouble I had is mechanical/pilot issue rather than heat issues. I would appreciate a more reasonable debate coming from you when addressing me. I posted some links below, I trust videos, measured contributed data, reputable brands more than unfounded opinions.

In Wemotec's online shop, it is selling the 2w25 saying "Cheap but reliable motor for 6S Lipo in Mini Fan pro or HW 505
Consumes about 42 A in Mini Fan pro on 6S Lipo". Dun think Wemotec wants to risk selling something they do not think will work.



Search on RCgroups, 404 results since 2007, please find one that says cannot take more than 800 watts.

http://www.rcgroups.com/forums/search.php?searchid=23996075&query=2w25

I think we should get back on topic. If you want to talk about your testing and which motor can take what watts more, I suggest a new thread.

[edmond22]

HET F-15..

I'm gonna have to strip out the whole motor set-up... can't risk the vibrations. one of the fan unit is sounding very wrong also.

Maybe re-do everything again.. which is not a big problem

Glad you have that kit, very nice. The vibrations couldn;t be due to the airframe then. Is the Blade rubbing the shroud? Normally when you install the fan and test it, it will be fine but when you finally install them into the airframe, they might distort a bit and cause the blade to contact the shroud. Try taking out the offending unit and test spin on its own and see what happens. If it is the HET 6904 and 2w25 combo, should not need any balancing.

[trailblazer]

Glad you have that kit, very nice. The vibrations couldn;t be due to the airframe then. Is the Blade rubbing the shroud? Normally when you install the fan and test it, it will be fine but when you finally install them into the airframe, they might distort a bit and cause the blade to contact the shroud. Try taking out the offending unit and test spin on its own and see what happens. If it is the HET 6904 and 2w25 combo, should not need any balancing.

Thanks man.. i loved it the day I bought the kit

and yes... i definitely tested before fitting in everything also.. that has always been standard procedure even b4 i converted to electric..

(testbench the glow engine and breaking-in before fitting to plane)

Results from that:

the shroud got scratched and the fan got slightly fused to the motor housing due to the airflow pushing the fan towards the housing and causing friction.

Solved that by putting 1.5mm washer between the fan and the motor.

Can't solve the fan scratching the shroud.. did all i could... the motor jus sits too snugly in the motor housing.. worse case scenario is i buy 2x wemotec minifan...

(I already have one wemotec minifan powering an RAF Bae Hawk)

[edmond22]

Thanks man.. i loved it the day I bought the kit

and yes... i definitely tested before fitting in everything also.. that has always been standard procedure even b4 i converted to electric..

(testbench the glow engine and breaking-in before fitting to plane)

Results from that:

the shroud got scratched and the fan got slightly fused to the motor housing due to the airflow pushing the fan towards the housing and causing friction.

Solved that by putting 1.5mm washer between the fan and the motor.

Can't solve the fan scratching the shroud.. did all i could... the motor jus sits too snugly in the motor housing.. worse case scenario is i buy 2x wemotec minifan...

(I already have one wemotec minifan powering an RAF Bae Hawk)

Oh wait! If it is just rubbing slightly, I normally just muscle it a bit there and here to make it run as best as I could. I know what you mean on solving the slight rubbing problem. I would adjust it best as I could and make a waiver and let it rub (disclaimer, my approach only). I will let it rub and run till it clears keke. But watch that amp draw, anything stalling the fan is only going to bring the amp up. I do it at low throttle only. The HET is good, I like it better than the wemotec actually.

Are you intending on changing to 6s or another HET motor to run 4s?

[trailblazer]

Oh wait! If it is just rubbing slightly, I normally just muscle it a bit there and here to make it run as best as I could. I know what you mean on solving the slight rubbing problem. I would adjust it best as I could and make a waiver and let it rub (disclaimer, my approach only). I will let it rub and run till it clears keke. But watch that amp draw, anything stalling the fan is only going to bring the amp up. I do it at low throttle only. The HET is good, I like it better than the wemotec actually.

Are you intending on changing to 6s or another HET motor to run 4s?

no worries on everything battery wise.. i'm testing the whole set-up with the plane on the ground 1st..

like i'll still want to see how my batteries in parallel config. will hold up.. cos everything in the JAVA webpage is still calculation based on 1 single motor set-up.. i'll probably not be running at 1kw with the 4s but its a start..

i'll keep the 6s suggestion as one of the top of my list of changes.. and maybe use the 4s for an HET F-18... hehehehe