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E-flite . Futaba-RC . Next D

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e-Electric Conversions > Electric Conversion Options for PSU Test Stand
 
 
breedatrad
Senior Heliman
Location: NW PA

Hi All,

The Penn State University (PSU) has a Bergen Intrepid mounted in a test cell, powered by an old AstroFlite motor and speed controller. The motor's encased in a heat sink (custom built for them by Bergen, I think) but doesn't supply enough power to do realistic testing.
What suggestions can you full-size (.60 equiv) electric heli guys make for a better Motor/ESC combination. Basically; It's a Bergen Intrepid .60 frame (sans tail) mounted on a rigid test stand with strain gauges, RPM sensing, etc. attached to it for vibration/torque/thrust measurements. They're using an external power supply so volts/amps available shouldn't be a problem. It'd be nice if it could fit inside of the stock frames though so we don't have to re-engineer the whole set-up!

Thanks for any suggestions you guys come up with.

Brian Reed
breedatrad@csonline.net
10-13-2003 Over year old.
 
 
rscamp
Veteran
Location: Ontario, Canada

I'm not familiar with the heli so I can't help much there. What AstroFlight motor is in it? Is it an Astro 60? Which wind? What voltage is supplied to the motor? If you could answer these questions we could get an idea of the power you have now. How much power do you need? Is this a static test setup?

Without knowing gear ratios etc., it is hard to know what would be best. For a drop in replacement, I'm guessing you need something with a Kv of around 400-500 RPM/Volt for a 60 size heli running on 30 cells. A Kontronik Tango 45-04 might work, for example.

But again, a bit more information would go a long way, Brian!!!

Rob
10-13-2003 Over year old.
HOMEPAGE  
 
 
breedatrad
Senior Heliman
Location: NW PA

Sorry about the slim details Rob but I looked over a spare motor pretty good and don't remember any specific nomenclature. And, unfortunately, specific details of the original setup were probably lost as students graduated. I'm on board as an R/C Heli consultant and Project Pilot (A couple of Raptor .60's and a Bergen Observer for heli vibe experiments and aerial photography).
I'm guessing that the heli's got .60-kit stock gearing of around 9.3:1, and yes, it's for static testing. Think of it this way:
We want to convert a standard .60 heli to electric power, for indoor use. Size-wise, the motor should fit inside of the stock frames, but weight isn't an issue. We need power roughly equivalent to an OSWC or YS STII, or a little better. Changing the gear ratio isn't out of the question, if needed.
What motor and ESC combo would put out .60 power for extended, static testing?

Brian
breedatrad@csonline.net
10-14-2003 Over year old.
 
 
rscamp
Veteran
Location: Ontario, Canada

Haven't got a clue what power a "OSWC or YS STII" would produce at what RPM, but with a ratio of about 10:1 and 30 cells (30-35VDC) and doing the match you will want a motor with a Kv in the order of 500 or so to get a decent head speed if you do not change the drive ratio.

Will it be carrying the batteries or will it be on a tether? If it is on a tether a motor like the Tango would be more than adequate for spritely performance. I think the Tango could run continuously because it cools well. With the Tango, you would use a Kontronik Beat 50-8-30.

The Hacker C50-xxXL series is another option but you may have to increase the drive ratio.

There are outrunner motors (i.e. Actro 24-4 or 24-5) that would do well. I have no idea if they would fit your application though.

For mounting and outline dimensions, check out:

www.kontronik.com
www.hackerbrushless.com
www.actro.de

Rob
10-14-2003 Over year old.
HOMEPAGE  
 
 
breedatrad
Senior Heliman
Location: NW PA

OS and YS .61's make about 2.25 HP@ 17,000RPM. Most guys fly them in the 14-16,000RPM range so, they're probably making between 2.0 and 2.2 HP.
What RPM range do the larger electric motors run in? That'll determine the required gear ratio. Is there a "sweet spot" where they make the most power or is it strictly a function of Volts/Amps available? I'd like to be able to turn 680MM blades at approx 1500 RPM and am guessing that there's an RPM where the motor makes its best power without overheating the windings and/or ESC.
Quote 
Will it be carrying the batteries or will it be on a tether?

Read the previous posts. The heli is rigidly mounted to an indoor test stand. It uses an external power supply.
10-14-2003 Over year old.
 
 
rscamp
Veteran
Location: Ontario, Canada

Hmmm. I thought I already responded to your post days ago. Wonder where it went? Maybe I didn't hit the button.

1500W (2HP) power out is probably quite possible for brief periods. This equates to about 55A of current at 30V which is reasonable.

RPMs from the motor are pretty much whatever you want them to be. There is a lot of flexibility there because of the choices available. Motors fight to run at their specific speed so the shaft power (and current) increases with only a small RPM change and no change in throttle setting. This is quite different from IC engines.

Most controllers have governors so speed regulation is even less of a concern. You can obtain the motor constants and apply the motor equations and know very accurately where you are on the efficiency curve.

Rob
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10-17-2003 Over year old.
HOMEPAGE  
 
 
breedatrad
Senior Heliman
Location: NW PA

Cooling?

How about cooling... Especially on the external-rotor types? Do I need to use a cooling fan/heat sink arrangement to keep it from burning up under extended load?
What else do I need to know?

Brian
breedatrad@csonline.net
10-17-2003 Over year old.
 
 
rscamp
Veteran
Location: Ontario, Canada

We fly these things without extra cooling. Cooling varies by brand and motor design. The temperature rise will also depend on how hard you are on it. If your power/time profile is no more severe than that experienced in flight it should be fine.

I can tell you that the extra 10% or more efficiency improvement over the brushed motor will make a big difference in the amount of heat that is generated. It should reduce it by at least a third I would think. I have no experience myself with the outrunner motors and how well they cool, but they are used with good success in the Joker which is a very nice 60 size electric heli.
10-17-2003 Over year old.
HOMEPAGE  
 
 
cwd10
Veteran
Location: PA, - U.S.A.

Hey Brian. I work at PSU, and would be willing to help out with this project. Is it on main (University Park) campus?
01-30-2004 Over year old.
 
 
breedatrad
Senior Heliman
Location: NW PA

Yeah, it is. PM sent.
01-30-2004 Over year old.
 
 
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e-Electric Conversions > Electric Conversion Options for PSU Test Stand
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