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Confused!

Old 06-23-2003, 09:52 AM
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Guys....please help.

I'm new to the world of sparks, and have a problem that I'm not sure how to solve.

I have a 3D OD plane fitted with a 3 cell Lith-Ion pack, Hacker 08 BEC controller, a Torcman 350/10 motor and a APC 10x4.7 prop.

The problem is the motor is drawing too much current and shuts down after a 3 second full throttle burst.

Will upgrading to a 18 BEC controller increase this before the cells need a rest, or is this motor just inefficient for Lith-ION.?

I've tried emulating a friends set up, but with the Torcman instead of a Hacker B20L 4:1.
Old 06-23-2003, 11:49 AM
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Need more accurate information. What Li-ion cells are they ? What wind is the Torcman ? Are you sure it's a 350/10 (I didn't know you could get 10mm stator 350) ? What wind of Hacker B20L was your friend using and is he using exactly the same prop, cells etc. ?

My guess would be that the battery is too feeble for the motor/prop combination but there's no way to tell with the information given.

Steve
BTW please don't post the same message in several forums, one is enough.
Old 06-23-2003, 03:39 PM
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Your question can still be answered with the information given:

No, upgrading the controller will most likely not help. Amp draw is determined by the voltage of the battery, along with the motor and propeller.

Do you have any idea how many Amps your setup is drawing?

The only way to emulate a friend's setup is to copy it EXACTLY. By switching the motor without regard to how many Amps it would draw with your friend's prop
Old 06-24-2003, 06:42 AM
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Guys, sorry I'm so vague with this, as i said electrics is new and a foreign langauage to me.

Heres my spec (I dont know what the motors drawing as its all in German)

Cells: 3 cell Lith-IOn 10.8v 1.4A

Motor: Torcman 280/10, Prop: apc 10x4.7 (I've slightly cut it down)

Controller: Hacker 08 -3P (I'm changing to an 18)

My friends motor is the Hacker B20 18L 4:1 on the same prop and cells.
He gets about 10 seconds prop hang before the cells require a break.

I take it the Torcman is just not as efficent on these cells?
Old 06-24-2003, 03:45 PM
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No, it has nothing to do with being efficient on anything.

To accurately emulate your friend's setup, your motor needs to spin that 10x4.7 prop at the same RPMs, using the same Amps, as your friend's does.

I am sure that the Torcman is drawing signifigantly more Amps to turn that prop than your friend's Hacker. Your Torcman is probably putting out more power than your friend's Hacker, but the battery simply can't keep up what the motor's demanding from it.

When you draw too many Amps from a battery, the battery's voltage drops. The more Amps you draw, the more the voltage drops, until you reach the low-voltage cutoff (LVC), where the speed control either cuts the motor off entirely, or slows it down until the voltage comes back up. Since these are LiPoly cells, you are DAMAGING them by drawing them down to LVC. Most speed controls have a fixed LVC of about 5 Volts. You should not, under any circumstances, draw the voltage of a LiPoly cell below 2.7V, or you risk severely damaging the cell. In your case, that's 8.1 Volts. 5 Volts is less than 8.1 Volts, and that means you're drawing the voltage of your LiPolys down too far!

Using a heavier-duty speed control will actually make things slightly worse, due to the lower resistance it will have in the circuit. It will allow MORE current to flow.

The quick-n-dirty solution to this is to try smaller and smaller propellers until you get the Amps down to where the battery can handle it.
Old 06-25-2003, 06:39 AM
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Thanks for such a detailed reply....makes total sense - i now see a little more of the light!

My fear is that i'll end up with a prop too small to give me the performance I want (its an E3D model) So, I've ordered the obviously more efficient Hacker B20 15L 4:1.

For sale in the UK Torcman 280/5 and a Torcman 280/10 both used once!!
Old 06-25-2003, 07:59 AM
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I give up, you're just messing about with names and numbers. Now the model is an E3D not an own design as you first said. The motor is a 280/10 not a 350 as you first said.

Anyway a Hacker B20 is a very small motor for an E3D. It's more common to use a C40 geared 4:1 or even higher.

Good luck, it sounds like you'll need it

Steve
Old 06-25-2003, 08:14 AM
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Hey....check out the attitude on Steve.

Sure your second names not Meldrew?

Yes, Steve I made a mistake with the motor name, yes Steve its an own design E3D....that is possible isn't it? Surely motor size is relevant to the size and weight of the model, the whole thing ready to fly weighs less that 1lb.

I'll post a video of the one with the Hacker B20 torque rolling.

Your attitude is not welcome, and even with my limited electric knowledge, your wrong.
Old 06-25-2003, 01:27 PM
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The E3D is a very well-known design of a specific type and size kitted and sold in the hundreds (at least) by a modeller who often posts here. You claiming to have designed the same model except yours is not the same size is rather confusing.

Steve
Old 06-25-2003, 01:34 PM
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I didn't design it, its a friends OD....and I see E3D being used as a "buzz" word for Electric 3D in the UK - I was not reffering to the Gary Wright model.

I'll try to make my posts clearer as you seem to get easily confused.
Old 06-25-2003, 01:40 PM
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mkirsch, cheers for your help.

You know maybe it is the controller, as the throttle stick seems to act like a switch and instantly cuts the motor, its not a gentle drop off in power and the controller is getting quiet hot.

I already have a Hacker 18 controller so I'll fix it up tonight and see what happens.

I'll post a pic of the plane to save anymore confusion.
Old 06-26-2003, 06:48 AM
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Tried the 18 controller....seems to be a lot better and no throttle on/off switch effect. Hopefully I'll get a test flight tonight.

Not sure if I'm going to get the same duration with the Lith-IONs that my friend gets with his Hacker B20 version (35mins)

Heres a pic
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Old 06-26-2003, 03:30 PM
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Hmm, maybe you were just overloading the controller, then. That means you're definitely drawing more than 8 Amps, probably close to 10, maybe more. That's going to be pushing that 3S1P LiPoly pack quite hard...
Old 06-27-2003, 06:53 AM
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I'm aware that its a very borderline set up that has to be flown with care to give the cells a chance of reasonable longevity.

I got a quick flight in last night, superb! it just floats. Great 3D - you only need to push the cells a little hard in prop hang, so I think the idea is to keep that to the odd 8/10 second burst. But, the Lith-IONs give you such a light set up.

Is Li-poly and Lith-ION the same?
Old 07-03-2003, 12:11 AM
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Go to the LRK site
http://groups.yahoo.com/group/lrk-torquemax/
Old 07-19-2003, 03:42 PM
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Cool site. I followed the links. Not bad, just wish I had a lathe.

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