Upping the Volts

[Birdmanpete]

I have an unidentified Turborix motor which was supplied with a Turborix 60 A ESC, for "big" models. I tried it with a LiPo 3s 2200 battery in a Lanzo Bomber (2.2metre) and an 11x4 prop. It flew, in ground effect only.

I could easily fit two identical packs to give 24 volts. I wonder about the risks of cooking either the motor or the ESC. What precautions should I take?

Best wishes.

[hayofstacks]

What is your amp draw, and what does it pull your voltage down to? If you pull more amps then the battery can make, voltage suffers and amprage goes up.

[Birdmanpete]

I can only measure up to 10 amps. Will that test be adequate. And does the test have to be done at full throttle?

[hayofstacks]

Yes, it would be full throttle, and no 10 amps will not be adequate. 10 amps at 11.1v's is only 110 watts, which is roughly a .049 or smaller gas motor. I have a 240 watt motor on my 48" wingspan alpha 450 sport, running a 1800 mah battery.

Read some of the faq's and beginners guide to get an idea what all the numbers mean. Without knowing the specs of your motor it will be almost impossible to tell what type of setup you should run. You can generally guess at what an okay wattage level is by weighing the motor, and the kv rating will give you a good idea prop size and motor speed. It will not tell you much of anything about voltage requirements though.

[Birdmanpete]

I can weigh the motor but the kv rating is unknown. Is there a rough relationship between weight and Kv

[hayofstacks]

Do either of these look like the right motor?

http://www.airlandseahobbies.com/product/rcps81523
Or
http://www.airlandseahobbies.com/product/rcps81522

Can't really find much of anything under the turborix name other then cheapy speed controls. That site has the most complete list of motors I could find for them, and only those two sound like they even could be close. I'm leaning more to the smaller of the two, but I have no idea.

You really need to weigh the motor, or get ready to fry it with too much voltage. Especially if you have no volt meter.

[hayofstacks]

No real relation between weight and kv that I know of. A kv rating is how many rpm's the motor pulls a volt. This basically tells you about what range and size of props could work okay. A slower motor wants a larger prop, a faster motor wants a smaller one. This is also directly proportional to your cell count and voltage. Going from a 3 to a 4 cell could burn up a motor using the same prop if its close to maximum for a 3 cell. Pulling a 4 cell in should require a prop change to keep amperage in check.

Watts = volts X amps. So if you increase voltage, you need to go to a slightly smaller prop to keep amperage in check.

So let's say a 3 cell (11.1v's or so) pulls 30 amps, on a 6 cell (22.2v's) you would only want a maximum of 15 amps to keep the power (wattage) the same. So you would need to prop way down, and the motor should spin about twice as fast on a 6 cell as a 3 cell, based on the kv rating, while unloaded.

Basically without specs on the motor, try stepping up untill you have enough power to fly the plane, see if it blows it up, or replace the motor with one you know or can find the specs for. Think about this.

Your motor might be 800kv (around 8800rpm's on 11.1v's), or it could be a 2200kv motor (around 22000 on 3 cell). That is a huge differance that might take you anywhere from a 15 X 8 or so prop, down to a 5 X 5, all based on the kv rating with 3 cells.

If I we're. Me, i'd get a watt meter, mesure what your actually pulling. Then you can decide if its even near what you need to fly the plane, based on the weight and size of the model, should give you a good idea how many watts you need to fly the plane.

However, just because wattage goes up, doesn't mean speed or thrust will.

[Birdmanpete]

While the pictures are not super clear I think it is the second of those two. It seems like I will have to buy a watt(amps) meter and wonder whether the 100w model will be big enough

[Birdmanpete]

I have entered a photo of the motor in members gallery witht he title mystery motor etc.

[Nitro Blast]

Originally Posted by Birdmanpete

I have entered a photo of the motor in members gallery witht he title mystery motor etc.

Posting it here is immensely helpful.... help us help you.

[hayofstacks]

I give up trying to find you picture. I spent 10-15 minutes and couldn't find it. But even still, the picture won't tell me anything you don't know.

[CrimzonRider]

Birdman, I can not find the picture either....maybe its me....dunno.....

...might be easier whenever you hit the post reply button and the new dialouge box pops up, go down to "manage attachments" and just attach it to this thread.....

Like Nitro said....with no pictures or at least a link to something somewhat similiar, it just a shot in the dark for WF people to help you get your problem solved correctly. At the very least, give us very accurate dimensions of motor,....length and diameter...even then you will only get very generalistic answers.

IMO Post #7 has good advice for ya.....gotta have a wattmeter to be able to see what your voltage/amps are doing at different throttle positions.

http://www.wattflyer.com/forums/showthread.php?t=24238

Lots of good help around here almost 24/7!!

cr

[Birdmanpete]

My frustration with the picture is as great as yours. Sorry about that. In the upload file I find the message " In the queue 1". I feel sure that ther must be a delay between entering a picture and having it appear. Anyway, cut a long story short, I tested it in the garden and at 5300 revs (at less than full throttle) it was really pulling at the lead so I decided to fly it. As a precaution I limited the throttle throw to 60%. The challenge with this one on coarse grass has always been to get the wheels rolling but it easily achieved that without any pushing on the fin from me and lifted away with great style in less than thirty metres. The wind was a little gusty and the battery packs were fractionally too far aft but the elevator sorted that out and all went well. On landing there was no sign of distress at the ESC or the motor but one of the old puffy batteries was warmer than the other and the charger would not accept it for re-charge. I should explain that these batteries were giveaways from a competitive aerobatics pilot. I ordered new batteries a week ago. They will be here soon. The watt meter will be ordered as soon as I am clear on the required range.

[CrimzonRider]

Originally Posted by Birdmanpete

My frustration with the picture is as great as yours. Sorry about that. In the upload file I find the message " In the queue 1". I feel sure that ther must be a delay between entering a picture and having it appear. Anyway, cut a long story short, I tested it in the garden and at 5300 revs (at less than full throttle) it was really pulling at the lead so I decided to fly it. .......... I should explain that these batteries were giveaways from a competitive aerobatics pilot. I ordered new batteries a week ago. They will be here soon. The watt meter will be ordered as soon as I am clear on the required range.

No worries....happens to me all the time.(espically with computers )

Hope you found the problem, used old batteries are sometimes the first place to look....seems like you found that out. IMHO doubling your voltage with an unknown problem might just double your problems. If more problems arise, just ask away.

As far as wattmeters go, there are several good ones....I have this one....

http://graysonhobby.com/catalog/mpiwattmeter-p-244.html

as long as it can carry 100amps or more, you should be fine.

http://www.powerwerx.com/digital-met...dc-inline.html


heres a good thread......
http://www.wattflyer.com/forums/show...atts+wattmeter

Good luck
cr

[hayofstacks]

I just got a stupid idea...

You can put a tachometer onto your motor, and get a much better idea of kv rating. However, this will still not give you a perfect number for wattage or max amps. But weighing the motor should get you closer enough to get a good idea what to shoot for.

I think you now have everything you need, the rest is up to you.

[kyleservicetech]

Originally Posted by Birdmanpete

I have an unidentified Turborix motor which was supplied with a Turborix 60 A ESC, for "big" models. I tried it with a LiPo 3s 2200 battery in a Lanzo Bomber (2.2metre) and an 11x4 prop. It flew, in ground effect only.

I could easily fit two identical packs to give 24 volts. I wonder about the risks of cooking either the motor or the ESC. What precautions should I take?

Best wishes.

Just a precaution. Don't double the voltage on any electric model motor unless you've got accurate motor specifications for the motor.

Doubling the motor voltage does NOT double the amps and watts. Depending on the motor, doubling the voltage on the same motor/battery/prop will increase your current by about 3-4 times, and increase the watts by 6-8 times. Doubling the propeller RPM increases the power to turn the prop by 2^3 power, or eight times.

Unless you really had the motor underloaded, doubling the voltage could easily burn out the motor or esc.

[solentlife]

Turborix motors are actually quite good motors and all the ones I've used have performed well and nearly as per spec.

They are found on ebay mostly.

To OP ... doubling voltage as Kyle says is not a good idea ... generally Turborix motors are for 2s - 3S ... but some can be used on 4S ... giving a 33% increase in voltage applied ... (increase in actual output depends on prop etc.)

[mred]

Originally Posted by Birdmanpete

I have an unidentified Turborix motor which was supplied with a Turborix 60 A ESC, for "big" models. I tried it with a LiPo 3s 2200 battery in a Lanzo Bomber (2.2metre) and an 11x4 prop. It flew, in ground effect only.

I could easily fit two identical packs to give 24 volts. I wonder about the risks of cooking either the motor or the ESC. What precautions should I take?

Best wishes.

First off, you can look at your ESC and it will tell you how many volts you can use with it. It's almost a given that a 6S battery will fry your ESC, if not your motor too. Hobby King has some good prices on Watt meters and I would get one that goes to 100 amps at least. I have a Wattsup meter right now and am getting a bigger one just for that reason.

That Lanzo Bomber is a big draggy plane and will need a good size motor. Either your motor is to small, it is under proped badly, not enough volts from the battery, or all three. You really need to find out what motor you have and how to run it along with a good watt meter. Can't set up a motor properly unless you have that watt meter. Look on the motor and see if there are any numbers on it.

It sounds like you may be a little new to electrics so I would read this thread if I were you. It will answer a LOT of questions you may have.
http://www.wattflyer.com/forums/showthread.php?t=31368
This will cover most of the things you need to know when you are starting out and save you a lot of hair pulling along the way.

Ed

[ron_van_sommeren]

Originally Posted by Birdmanpete

... I could easily fit two identical packs to give 24 volts. ...

For a given system, motor current wants to go up squared with voltage, faster than one would expect (because a motor is not a simple resistor where I = U/R). So, doubling the number of cells would give an increase in current by a factor (2)² = 4! Worst case (no voltage sag, no resistance in system).

The table below lists the effect of one or two extra cells on current. Again, this is worst case.
Note that cell chemistry is not relevant (Pb, NiMH, LiPo, LiPoFe4)

One cell extra

1 ->  2 cells: 2   x 2   = 4   times higher, 300% more current
2 ->  3 cells: 3/2 x 3/2 = 2,3 times higher, 130% more
3 ->  4 cells: 4/3 x 4/3 = 1,8 times higher,  80% more
4 ->  5 cells: 5/4 x 5/4 = 1,6 times higher,  60% more

Two extra cells

2 ->  4 cells: same factor as 1 -> 2 cells
4 ->  6 cells: same factor as 2 -> 3 cells
6 ->  8 cells: same factor as 3 -> 4 cells
8 -> 10 cells: same factor as 4 -> 5 cells

Originally Posted by hayofstacks

What is your amp draw, and what does it pull your voltage down to? If you pull more amps then the battery can make, voltage suffers and amprage goes up.

You intended to write current goes down.

Originally Posted by Birdmanpete

I can weigh the motor but the kv rating is unknown. Is there a rough relationship between weight and Kv

Kv is not a rating. It's just a matter of more (lower Kv) or less (higher Kv) number of turns in the coils. No big deal there. More importantly though, it is not a unit of measurement, it is a physical property, the (inverse of the) motor's generator constant. Saying a motor has 200 Kv is not correct and leads to misunderstandings/smoke: Kv says nothing about power, torque, current, quality, efficiency, magnets, weight, size.
It's a bit like saying a car costs 25.000money, weighs 4000mass, can go from 0 to 50speed in 6time and has a battery of 250capacity. Correct: Kv = 200rpm/Volt. Unfortunaty almost all manufacturers and suppliers write it the wrong way. I got Cobra motors to change it and do correctly though

Also Kv = 1/Kt, where Kv torque for given current, in Nm/Ampère. All in units for grown-ups SI units, not the units used in Birma and one other country I dare not mention here



Vriendelijke groeten Ron
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