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ragbag
07-19-2005, 10:31 PM
I picked up a Sis Kadet EP 42. Did the water break in as I always do with brush motors. The first motor was very noisy and had very dirty water after each run.

3

The motor continued to give me problems, Sig replaced it with no problems.

Did the water breakin on the second motor and here is the results of the new one.

4

As you can see it was a great improvement.
George
Gainesville Fl

Reformed Nitroaddict
07-19-2005, 11:24 PM
Wow - what a difference! Do you know what contributed to the water getting so dirty on the first motor?

Mike Parsons
07-20-2005, 12:29 AM
Wow that was a huge improvment! That is strange that the brushes would have had generated that much residue. I wonder if they were a bad batch. Good to see that they replaced it....good on SIG.

-Mike

ragbag
07-20-2005, 12:33 AM
Possibly a soft brush or a soft spring. The motor had a lot of arcing at the brush's and ended up with an open winding. Didn't go into it as it was under warranty and didn't want to give that up.

Everything else that was with the kit was quality, guess one out of a bunch isn't bad, just happened to be mine.
I just count it as a learning experience, that's how we impprove the product.


George
Gainesville fl

Joe Ortiz
08-01-2005, 08:00 PM
How do you do a water break-in:confused:

Joe

Matt Kirsch
08-01-2005, 09:34 PM
You break the motor in, in water.

Yes, water. More specifically, you place the motor in a container of water, and run it. The water carries the brush dust away, and you end up with a much better breakin.

Doesn't it short out? Well, no. Water is a very poor conductor of electricity, and electricity will always prefer the path of least resistance. In this case, the brushes and copper windings of the motor are the path of least resistance. Nearly all of the electrical current will follow that path.

What you have is a parallel circuit, with one leg going through the water, and the other through the motor. Electricity will flow in proportion to the resistance of each leg of the circuit. Lots of juice will flow through the low-resistance motor, and very little will flow through the high-resistance water.

An interesting factoid is that pure water is completely non-conductive. It's the impurities in the water that cause it to conduct electricity.

ragbag
08-01-2005, 11:34 PM
You only do this to brush motors.

As Matt said, distilled water is an insulator.

I never run the motor before break in, if you do then the brushs are score before you start.

I place the motor in a container of water and run it at low voltage. I have a power supply that puts out 5 volts and that is what I use. I run the motor for a few minutes, watch the color of the water, as it turns grey replace it with clean water. when the motor runs nearly clear water you are done.

That is how I knew I had something going with the Kadet motor, 3 five minute runs and the color never changed.

After the run, drop the motor in alchol and let soak for a couple of minutes. The alcohol absorbs the water, blow out with compressor or some sort of low pressure air. Re-oil and set aside to finish drying. If I don't want to wait I put a heat gun to it and warm it a little.

Run it and you will see very little if any arcing on the brushs.

George
Gainesville FL

Joe Ortiz
08-02-2005, 12:00 AM
Wow, great information, thanks.

Joe

Geoff_Gino
08-02-2005, 01:58 PM
Hi Guys

I am slowly getting to grips with the LiPo packs and wold like to clear a few things up so that I don't end up with a ball of smoke.

When describing a LiPo pack I understand that 6s3p actually means 6 individual cells in series and 3 individual cells in parallel, which means there are a total of 9 indivudual cells.
If this is true - what would be the total voltage of the pack and how do you determine the current rating. I believe KOKAM have a 3,2A/H cell on the market, now my problem is that these are not available in South Africa and I will have to make up what I need from our local hobby shop.
The power pack is intended for a Hanger9 F4U 60 size Corsair which will probably be in the region of 10 Lbs when finished.

If I "had" 2 of the Kokam packs in the plane would they have to be charged individually at the field or would I be able to charge them together (series or parallel).

I have contacted a local distributor who does NiCad and NiMh for our instruments and they won't deal with LiPo's so I'll be stuck with my local hobby shop and their normal quote is "can be done - take 6 to 8 weeks though"

Any and all help is welcome and a cct diagram or 2 would help.

Thanks
Geoff :confused:

Reformed Nitroaddict
08-02-2005, 02:43 PM
Cannot answer all of your question, but can on some of it.

You are correct in your comments about parallel and series. When wiring packs in parallel the amps available and mah increase, but voltage stays the same.

For example:

a 3S1P 10C 1300mah pack is 11.1V, 3cells, and 1300mah. It has a 10C discharge capacity meaning it can be safely discharged up to 13amps.

A 3S2P 10C 1300mah pack, would be 11.1V as well, since it is two 3cell packs wired in parallel. Voltage stays the same. But now, the total mah rating is 2600mah. Now, because it is two 10C packs wired in parallel, it is essentually a 20C pack. So this pack can be discharged safely at 26amps. Or at some less amerage but a much longer runtime.

Make sense? The primary reason for wiring cells in parallel is to increase the max amps the pack can produce. So if you follow the general rule of 100watts per pound, you would want to prop and gear the motor to allow for 900-1000watts being that your plane is 10lbs. Since volts x amps = watts, the packs would need to produce about 90amps at 11.1V. This is rather high, so it might be better to increase the series of cells to four instead, 14.8V. Now, you only need to produce 60amps to get to 900watts. So, if you had four cells of say 2000mah each, then a 4S3P 2000mah pack would allow 14.8V and 80amps max power. This pack would easily be able to produce 900-1100 watts of power if properly proped and geared. Of course, you need to make sure that the motor and ESC can handle it too.

Did this all help?

Geoff_Gino
08-02-2005, 03:13 PM
Nitro

Thanks for the quick response. It does all make sense but my main worry is charging the packs at the field and is the 14.8 volt not to high for a field battery. (Must be as the field battery only gives 12 volt) so what's wrong with two field batteries in series for 24 Volt to run a field charger.

Geoff

Reformed Nitroaddict
08-02-2005, 03:47 PM
Geoff - I don't see any reason why you couldn't do that with the field batts. Their may be another way that I'm not aware of though - as I usually fly park flyers, so this isn't an issue. I know there is a thread in the giant scale forum about someone building and flying a large scale electric, maybe ask him how he is doing it?

Matt Kirsch
08-02-2005, 09:39 PM
Follow the charger's recommendation for input power. Chargers capable of charging high-voltage packs have a voltage booster circuit that allow them to charge the packs from a 12V power source.

Use this phrase to remember the "3S2P" notation: Sells(cells) in Series, Packs in Parallel. When you see 3S2P, for example, that means "three cells in series per pack, two packs in parallel." You MULTIPLY the numbers together to get the total number of cells. A 3S2P pack would have SIX cells in it, not five.

Geoff_Gino
08-03-2005, 07:07 AM
Hi Matt and Nitro

Thanks guys - I am getting the hang of it now. 2 field batteries in series will not be a problem as long as the field charger can handle the 24 volt input and with modern electronics most if not all should be able to handle the input. My aim is to be able to charge all of the packs at once but having seen the EAM 17 bomber this has become my goal and even if I need 4 field batteries and 4 field chargers BOY DO I WANT THAT!!!!

Geoff

Warren T
03-06-2008, 02:35 AM
The cobalt motor in that plane was so weak I gave it away. If you want to fly it use a brushless 400 outrunner and a 3 cell lipo battery and it will go just fine. Check out Hobby City or BP products so you can get a system with out a co-signer.


warrenI picked up a Sis Kadet EP 42. Did the water break in as I always do with brush motors. The first motor was very noisy and had very dirty water after each run.

3

The motor continued to give me problems, Sig replaced it with no problems.

Did the water breakin on the second motor and here is the results of the new one.

4

As you can see it was a great improvement.
George
Gainesville Fl

Slowdoc
05-21-2008, 11:15 PM
The cobalt motor in that plane was so weak I gave it away. If you want to fly it use a brushless 400 outrunner and a 3 cell lipo battery and it will go just fine. Check out Hobby City or BP products so you can get a system with out a co-signer.


warren
=============================================
Check out the new Brushless deal for $10 more than Brushed.
I'ts designed for Outrunner looks like BP hobbies 2410-9Y. But I had to upgrade that from 8a- 83Watt to RCHot Deals 2408-18T for 11.6 a at 125Watt using 9 x47 APC SF.
Ernie

Dr Kiwi
05-22-2008, 04:28 PM
Wow, great information, thanks.

Joe

Just use a D-cell or two for the under-water break-in. On small motors I've used an AA.