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Old Jun 14, 2003, 05:58 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,439 Posts
DC5-2.4 & AstroFirefly Motors

This thread is for small coreless motors, but not pager motors. Specifically it is for the DC5-2.4 from Westechnik and the Astro Firefly.

The DC5-2.4 is made CIK in Japan (edit, thanks to Matt Keennon for that bit of information) and the Firefly is made by Maxon. Here is a picture of a number of variations of the DC5, and one Firefly.

Top Row, left to right:
  • the DC5 9:1 (also available in 6.7:1) from Westechnik, 14g
  • the DC5 with open 5:1 gears from Westechnik, 7.9g
and bottom row, left to right:
  • Astro Firefly with old style 4:1 gearbox, 12.5g
  • DC5 with 11:1 gearbox from Westechnik, 14.5g
  • DC5 8:1 open gears from Westechnik, 13g
  • DC5 with VL products 5:1 planetary gearbox (Aeromicro), 14.4g
  • the DC5 Kolibri with Maxon 4:1 planetary gearbox from MTM in Germany, 13.2g

First, open gears are lighter than planetary gears (the Wes gearboxes are not true planetary gears). But, planetary gears are quieter.

My focus is mostly on semi scale planes for these motors like the Hobbico Staggerwing Beech ("classic bipe") foamie FF or the Estes RC version of the same plane. So, the higher gear ratios won't be appropriate as the prop would have to be too large.

A couple of more facts. The Maxon 4:1 planetary gearbox used on the MTM DC5 and the Firefly weighs 2.5g for the plastic gear version, and the metal gear version weighs 5.5g. Also, the DC5 is 12mm in diamter, which means it can use the GWS heat sink, which weighs 2.5g.
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Old Jun 14, 2003, 05:59 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,439 Posts
Here's the picture
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Old Jun 14, 2003, 06:06 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,439 Posts
And here are some static tests of the DC5 from MTM with the same 4:1 planetary gears and Gunther prop as the Firefly. The 7.4 volt tests are intended to estimate what the volts would be under load for a 2-cell LiPoly pack, while the 10 and 11 volt tests are meant to represent a 3-cell pack. I don't have any tests from packs yet, so I don't know exactly what they would be under load, and it depends on the capacity of the LiPoly cell anyway (e.g., volts under load for a Kokam 145x2 will be lower than for a E-Tec 250x2 if the load is high enough).
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Old Jun 14, 2003, 06:25 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,439 Posts
But, running either motor on three LiPoly cells is more than recommended by either Astro Flight or MTM. So, this graph shows thrust as a percentage of time zero thrust at 10 volts for both motors. Clearly there is some margin of error for any of these tests since the DC5 with a heat sink actually experiences a larger decline in thrust in the last minute of the motor run.

These are extreme tests as they are full throttle straight from my power supply at a perfect 10 volts. The prop is not unloaded, so the amp draw is higher than it would be in flight.

But, it looks like the smaller Firefly cannot stand up to the sustained high amp draw as well as the slightly larger DC5. But, if you don't abuse it, as Mike Taylor seems to have done, you can probably run this setup in your plane with occasional bursts of full throttle.

At the end of these tests both motors were slightly hot, but not so hot I couldn't put my finger on the motor and keep it there. I have a remote heat sensor on the way, but my finger is probably good enough. And, the Firefly was slightly hotter after this two-minute torture test.

I'll post more if I learn more. These tests give me most of the answers I need. I still haven't decided which motor to put in my Hobbico Staggerwing conversion.

Gordon
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Old Jun 14, 2003, 07:49 PM
Registered User
Hilo, Hawaii
Joined Jan 2003
111 Posts
Hi Gordon,

Have you considered the GWS LPS motors? I'm planning on testing one out on my Colibri next Friday night using a 2S1P Etec 250's.

GW/LPS-B2C-C
(M0.25) 62T / 10T = 6.2:1
Weight : 11.81 g (without propeller)

Prop EP7060
Volts 7.2
Amps 1.06
Thrust 58g/2.03oz
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Old Jun 14, 2003, 08:29 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,439 Posts
A seven inch prop would be sort of on the big side for what I'm looking for for the little staggerwing Beech. And, that motor/gearbox would have a very hard time fitting in the cowl. The advantage of the 4:1 planetary gear box is how compact it is, and quiet. These coreless motors are also more efficient. Mostly, I've had these motors since before GWS introduced their LPS system. At higher volts these still pull fewer amps and generate more thrust with a lower gear ratio and smaller more appropriate prop. And, when loafing around at 1/2 to 1/3 throttle, these corelss motors should be considerably more efficient than the LPS.

But, thanks for the suggestion. If I didn't have several of these coreless motors I might think about the LPS motor. In fact, I seem to recall one of the people who converted the Hobbico Bipe used the LPS system.

Gordon
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Last edited by Gordon Johnson; Jun 14, 2003 at 08:59 PM.
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Old Jun 14, 2003, 09:44 PM
Registered User
Hilo, Hawaii
Joined Jan 2003
111 Posts
Hi Gordon,

No probs, just a thought I'd bring up. I just fried two brush sets on my DC5-24 using the E-tecs probably because of the FMA mini 5 esc that I have on it. It was fine when I was just using 6 cell 120 mah nicads, but as soon as I switched to the E-tecs, there went my brushes! I just got a lead on where to buy a good ultra high freq. Schulze esc, but in the mean time, I'll be fooling around with the LPS systems. I also have a LPS RXC with a Westechnic CF prop on it now that will hover the Colibri but unless I reinforce the wings, I'll probably flutter it to death! My guess is that the LPS-B2C-C would be more suited for my Colibri so I will be trying that with either the 7060 or 6050 props.
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Old Jun 14, 2003, 11:59 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Bill,
Is the Shulze higher frequency than the JMP HF9, now called the HF10 since it can handle more amps and volts? Castle creations was going to release a high frequency ESC that was supposed to be considerably higher than the HF9, but never has. So, I'm curious if anyone has topped the HF9 yet.

Gordon
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Old Jun 15, 2003, 02:22 AM
Registered User
Pittsburgh, PA
Joined Jan 2002
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Re: your third post

Quote:
Originally posted by gordonjohnson
... The 7.4 volt tests are intended to estimate what the volts would be under load for a 2-cell LiPoly pack, while the 10 and 11 volt tests are meant to represent a 2-cell pack. ...
Gordon. I'm a little confused here. You said 7.4 for 2 cell Lipo and 10&11v .. a 2-cell pack. Did you mean the 10/11v are for a 3 cell Lipo ?
-Mike
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Old Jun 15, 2003, 02:28 AM
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Inari's Avatar
Las Vegas
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Gordon, if I read your graph correctly, the Firefly drops thrust faster than the DC5 but they both draw roughly the same Watts initially. Why do you think this is?

-John
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Old Jun 15, 2003, 05:14 AM
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jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
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Gordon,

thanks for your data. AFAIK nobody has ever measured the effect of the motor heating up. High currents are generally quite dangerous to the coreless motors because their rotor, having no iron core, has little capacity to take over heat energy and thus heats up quickly. besides that, without the core that could stabilize a heated rotor, the resin that holds the core in shape could melt and so destroy the rotor. Gordon, do you remember the fried DC1717 at the indoor event we both visited?

It has been common opinion that 8V and 1A is the practical limit for the DC5-2.4, and this only can be used with a high frequency ESC. This explains the experiences of ColdBlood.

Gordon,

the HF100 is not made by Jean-Marie Piednoir (JMP) but by Heino Jung (he lives near us and steps by every now and then at our indoor meetings).

John,

I think the rotor of the Firefly heats up more quickly than the one of the DC5-2.4, so the coil resistance raises more quickly, so the power goes down more quickly. It seems that the DC5-2.4 can get rid of the warmth easier. To confirm this Gordon could measure the static resistance directly before and after the test run. I would expect the resistance of the Firefly to go up more.

Regarding the IPS drives: I think this is a question like if you prefer a VW or a Mercedes-Benz. Both are fine cars, both will bring you to your aim, but sometimes you need the extra efficiency and lightness of the coreless motors, and sometimes you just want to allow yourself something!

Thanks again, Gordon, for showing us your interesting results.

Regards, Jochen
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Old Jun 15, 2003, 09:00 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,439 Posts
Jochen,
As usual, you know more about motors than I do. Thanks. Do you think the DC5 at 10 volts, but 1 amp will be ok? I think the key to all this is not to use it in a hovering type of plane. With the little staggerwing as I'll probably fly it it will get full throttle for the occasional steep climb or loop, with lower throttle settings in between. I'm also about to substitute a slightly smaller prop to see how much affect that has on amps. That might be another way to help preserve motor life a bit.

I think I may try measuring resistance as you suggest before and after a motor run. I did notice a very slight uptick in amps with the Firefly at the end of the two minute run. I interpreted this as related to windings getting hotter and having more resistance when hot.

I think you mentioned that Heino Jung makes the HF9, but I guess it must be marketed by JMP. Some time back I saw an article by someone who visited JMP in France and there were pictures of 50 HF9's being made by him in his apartment. Maybe he originally made them and now he subcontracts them to Heino. Regardless, I love those little ESC's.

Gordon
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Last edited by Gordon Johnson; Jun 16, 2003 at 10:10 AM.
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Old Jun 15, 2003, 03:15 PM
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California
Joined Oct 2002
410 Posts
Gordon- a couple comments. I think the DC5.24 motor is not made by Faulhaber but by CIK in Japan, note 'CIK' marked on the back of the motor. CIK was started by ex Namiki employees and the motor design is very similar to Japanese coreless Namiki motors (pagers). That motor is very good, and has high efficiency, 78%, as I dyno tested it at work. We ran it regularly at around 8V and 1A at around 25,000 RPM. -Matt
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Old Jun 15, 2003, 06:08 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Mike,
I corrected that post. Typo, yes it was supposed to be 3 cells for 10 and 11 volts.

Matt,
But what you you think about running the DC5 at 10 volts, but still a 1 amp draw? I stand corrected on the origin of the DC5-2.4. I have been previously told that that motor was also Falhauber, but now know otherwise. That explains why I could never find it on the Falhauber/Micromo site. Thanks. I'll correct the post above. You ran the motor on a dyno. In my static test above at 7.4 volts I got about 21,480 rpm at the motor. Since we probably can't get 8 volts for very long under a one amp load, we might be able to increase the prop pitch, or diameter and run on two cells. I might explore this.

When I started this thread I had two small boys in my home office with me so didn't have time to do much more than post some graphs. But, my reason for starting this thead is we were discussing these two motors in the Estes Bipe conversion thread and it seemed better to get that discussion in its own thread. In this thread Mike Taylor says he has had good success with the Firefly on three cells, which is what started me wondering about also using three cells with either of these motors in my conversion of the FF version of this plane. Also, at least one person converting the FF version of this plane in the Hobbico Classic Biplane thread used the DC5 motor, but on two cells. I believe he used the 5:1 VL gearbox.

So, finally, some background on why I started this thread.

Gordon
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Last edited by Gordon Johnson; Jun 16, 2003 at 10:12 AM.
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Old Jun 15, 2003, 07:26 PM
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MSC Rödinghausen, Germany
Joined Feb 2001
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Gordon,

kind regards to your two small boys! I had another small boy here who wanted to go to the Lego homepage, so I know what you mean! (And I like it, BTW).

Regards, Jochen
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