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bert269
03-24-2006, 05:08 PM
Hi
I'm converting a brand new 60 Trainer from gas to electric. The gas engine req. was specified as .40-60(2c). WHat I have in the plane now is a Phoenix-45 ESC, AXI2820/10 brushless and a wooden TopFlight 11x8 prop. The battery pack is Lipo 14.4V 2300maH (discarge rate = unknown)...

Ok, this is my results from the Hyperion E-meter:
Volts: 12.18
Amps: 7.5
Watts: 91
RPM: 5295

I must add that I did NOT made any setting changes to the e-Meter. Are these reading correct? How can I ensure that they are correct - what do I need to set the e-meter too?

Please advise.

Thanks
Bert

slipstick
03-24-2006, 08:26 PM
I know nothing about the "e-meter" but those readings are wrong. The current should be more like 40A and the power around 500W.

Did you connect the meter to the battery first and give it a few seconds to stabilise before you connected the ESC ? Not doing that is one reason why some wattmeters give odd readings.

Steve

jonnyjetprop
03-25-2006, 09:57 PM
Let me pop in with a couple of things. Here is the manufactors web site for the motor:

http://www.modelmotors.cz/index.php?id=en&nc=produkty_vypis&kategorie=m_neodym_ac&id_rady=axi_28&id_produktu=axi_2820_10&nazev_rady=Series%20AXI%2028%20GOLD%20LINE&hmotnost_rady=(78%20-%20161%20g)

The max amps are 42 for 60 secs. The max eff is 30 amps. This makes the motor a 300 watt motor. This is just too small of a motor for the plane.

Here's the way I see it. Your plane will weigh about 6 lbs. ready to go. I would recommend a system that can provide 100watts/lbs. or in you case a 600 watt system. Figure an curent draw of 40 amps.

600 watts divided by 40 amps means that you need a 15 volt battery that can provide a 40 amp current.

For lipos, this means a 4s or 5s battery.

If your current battery can't deliver 40 amps, you need a bigger battery.

Let me recommend Espirt Models website:

http://www.espritmodel.com/

Look under the motor section. There are many different brands of motors listed. More importantly, they list the watt output along with the battery and propeller. For this model, find a system that can put out 600 watts and you'll enjoy the model.

Hope this helps.

John

bert269
04-10-2006, 06:57 PM
Hi John

Thank you for the info - yet it helped me a lot and got me started (good I think).....

I am finally at the stage where I received the motor and put it in the plane. I ordered the AXI 4130/20 - Yes I know it may be a very big motor, but I figured that since it will gave me the power I can put it just as well and later use it in another plane if I thru with my taining on the trainer.

In the mean time I have also ordered some LIPO's (and are awaiting the second batch). I have ordered 2 X 14.4V @ 4000mah. I could not get the same LIPO's the second time I ordered and could only get the 18.5V's @ 4000mah.

I currently have a 45Amp ESC installed with the two 14.4V @ 8000mah (Parallel). But the motor almost had no power, when I tried it out over the weekend???. I guess according to the website you send me:
Aerobatic/3D GP U-Can-Do 3D 4130/20 Jeti 77-O TP6000 7S3P Li-poly 19x8 APC-E Scale GP Ryan STA-M 4130/20 Jeti 77-O TP8000 8S4P Li-poly 16x10 APC-E Scale Racer GP Shoestring Racer 4130/20 Jeti 77-O TP6000 10S3P Li-poly 15x8 APC-E
that I certainly need more LIPO's (4S +), right?

I am waiting for a bigger ESC, so that I can put the two LIPO's in serie to get 33.3V. I would have liked to get it at 8000mah (two serie, two parallel) - but I will not have enought space in my fuselage for all that lipos'....So I will have to stick to the 4000mah.

The prop I currently have installed is a 13X11. Now I have not tested the RPM's and WATTs with my e-meter yet, I'm waiting for the ESC, which should be here in the next couple of days.

How does this setup sounds to you. Will I be able to get it in the air?
Let me know what you think, please?

Take care
Bert

Matt Kirsch
04-10-2006, 09:24 PM
Volts are where your power comes from. The more Volts you have (i.e. cells connected in SERIES, not parallel), the more power you have.

The 4130/20 is a very "cool" or low-Kv motor, meaning it requires a high voltage to get it into its operating range. ModelMotors.cz rates the motor for 16-24 (NiCd) cells, which is equivalent to 5S to 7S in LiPoly. On a 4S pack, the motor won't produce any usable power. Connecting more 4S packs in parallel won't help, because all that does is increase duration.

Frankly, the 4130/20 isn't the ideal motor for this setup, either. A more appropriate motor would be the relatively hotter 4130/16. Coupled to a 6S LiPoly and a 15x10 prop, this makes a great conversion for most .60-size sport, aerobatic, and warbird models.

If you can't return the 4130/20, we can work with it.

I'm not sure who's been feeding you information, or if you've been playing the, "buy first and ask questions later," game, but you'll be much better off asking here first, then making one trip to the hobby shop.

bert269
05-01-2006, 04:49 PM
Ok, I have ordered and installed my 4130/16 and I must say it really does make a difference - powerwise.

I have two lipos in the system both 4000mah. The one is 18.5V and the other is 14.8V (5S, 4S). I have them in serie connected, so about 33.3V !

No, I did not have the change to get the plane in the air yet. I only set it up finally over the weekend and connected the E-Meter to it.
Just to add. Accoring to the specs of the 4120/16 for a plane of around 160oz, I used a 13x8 prop.

At full throttle (on the ground) the emeter only reports about 35% effeciency. Does this mean anything? The max RPM it measured was about 9000.

I really must say - there is a lot of power(toque). I really had to hold onto the plane to keep it still, even just at 1/2 throttle.

I will report back on the weight, etc later today.

I was wondering (besides the effeciency thing), is the RPM's good enough for the plane to get it in the ait (and keep it there for a while)?

Thanks
Bert

philmaur
05-03-2006, 10:22 AM
Ok, I have ordered and installed my 4130/16 and I must say it really does make a difference - powerwise.

I have two lipos in the system both 4000mah. The one is 18.5V and the other is 14.8V (5S, 4S). I have them in serie connected, so about 33.3V !

No, I did not have the change to get the plane in the air yet. I only set it up finally over the weekend and connected the E-Meter to it.
Just to add. Accoring to the specs of the 4120/16 for a plane of around 160oz, I used a 13x8 prop.

At full throttle (on the ground) the emeter only reports about 35% effeciency. Does this mean anything? The max RPM it measured was about 9000.

I really must say - there is a lot of power(toque). I really had to hold onto the plane to keep it still, even just at 1/2 throttle.

I will report back on the weight, etc later today.

I was wondering (besides the effeciency thing), is the RPM's good enough for the plane to get it in the ait (and keep it there for a while)?

Thanks
Bert

Bert, can you get a full set of readings with the Emeter - volts, amps and rpm and the exact make and size of the prop? Then it would be possible to answer your question on efficiency.

Phil

bert269
05-14-2006, 07:07 PM
Philmaur,

Hey - no I did not forget about this tread - just too much going on and I could not get to it (for weeks!!!!)...LO
Sorry about that.
Anyway - I charged the LIPO's full and here is what I have:
Batteries: 33.3v 4000mah.
Motor : Axi 4120/16
Prop: TopFlight 14 X 8 (powerpoint) wood
Emeter Readings(with 100AMP Shunt):
28.87V
33.5 Amps
0969 Watts
5370 RPM
20% Effic

Please let me know what you make out of this....

Thanks
Bert

philmaur
05-18-2006, 11:01 AM
Philmaur,

. . . .
Motor : Axi 4120/16
Prop: TopFlight 14 X 8 (powerpoint) wood
Emeter Readings(with 100AMP Shunt):
28.87V
33.5 Amps
0969 Watts
5370 RPM
20% Effic

Please let me know what you make out of this....

Thanks
Bert

Bert, unfortunately, I haven't tested the TopFlight wood series of props, but let's make a few assumptions. I am guessing that you have taken the figures for the Aeronaut 14 * 8 folder ie pf = 3.08 and pc = 1.249 so that the efficiency from your figures would be

(5.370^3.08) * 1.249 / 969 = 19.9 %.

The problem is your rpm reading. Is there any chance you had the Emeter set to a 3 bladed prop? (A single push of button C on the tacho screen would set the blade count to 3). If this is the cause, the motor rpm would have been 5370 * 3 / 2, ie 8055 rpm. Now if you plug that back into the equation, out pops an efficiency of 80 %, which looks much more likely.

Certainly, there is no way that 969 watts in would only give 5370 rpm on a 14*8 prop. (We have recorded 1500 rpm more than this from a Z3025/6 with under 600 watts in).

The prop constants for your wooden prop., would not be exactly the same as the Aeronaut 14 * 8, but we are at least in the right ball park. Any chance of repeating the test - check the blade count, put the constants in as 3.08 and 1.249 and try a few runs to waiting for the steady rpm Hold and save the readings and get back to us with the results.

Have fun,

Phil

Matt Kirsch
05-18-2006, 01:32 PM
Something is definitely wrong here. :confused:

You should be seeing Amps in the 100+ range, for about 3 seconds, before the whole system goes up in smoke!!! :eek:

The 4130/16 is only rated for 12-20 NiCd cells, which is 4S to 6S LiPoly. From what you've described, you're running 9S!!! :eek: That's way way way too much! :eek:

Of the two packs you have, the 5S, all by itself, would be best when coupled with a 16x10 prop. The readings on your E-meter should then be in the 35A range, with voltage around 16V. RPMs should be around 6000.

As I said earlier in your thread, Volts are what determine how much power you have. But, like any other application involving power, you can easily have too much. What happens when you run 900HP through a crankshaft designed for 300HP? It breaks. Put too many Volts into a motor, it breaks too. That's why you MUST pay attention to the manufacturers' specifications.

I think you're getting away with it now because the cells can't take the high Amps, and you're keeping the runs short. If you tried to fly the plane this way... smoke 'em if you got 'em... :(

philmaur
05-18-2006, 03:33 PM
Something is definitely wrong here. :confused:

You should be seeing Amps in the 100+ range, for about 3 seconds, before the whole system goes up in smoke!!! :eek:

The 4130/16 is only rated for 12-20 NiCd cells, which is 4S to 6S LiPoly. From what you've described, you're running 9S!!! :eek: That's way way way too much! :eek:

. . . That's why you MUST pay attention to the manufacturers' specifications.

I think you're getting away with it now because the cells can't take the high Amps, and you're keeping the runs short. If you tried to fly the plane this way... smoke 'em if you got 'em... :(

Bert, I agree with Matt's comment about your cells not taking the high current, but I'm not so sure about the 100+ amps. Christian Perssons calculator for the 4130/16 gives 28.87v, 47.5A, 9058 rpm at 80.8% for an Aeronaut 14*8, whilst Motocalc seems to give 28.8 v, 44.9A, 8648 rpm and 73.9% for a 14 * 8 prop. Of course, not all 14 * 8 props are the same - yours might be less of a load than other makes.

To re-quote Matt "you MUST pay attention to the manufacturers' specifications." and I suggest you build up to the limit step by step, measuring all the way.

Phil

bert269
05-18-2006, 03:53 PM
Thanks guys, both of you - I do appreciate the effort you are putting into this, really. I understand and see what changes I can make to the config, but I will probably do some testing first again with those new parms to see if the efficiency picks up...

I really heard what you say about the voltage. And yes, I can see that I'm way too high on that, but according to the manufacturer's specs:
Voltage range 16-24 cells RPM per Volt 390 RPM/V Max. Efficiency 88% Max. Eff. Current 18-40 A (>84%) Max. loading 60 A / 30 s No load Current/10V 1,8 A Internal resistance 63 mohm Dimensions 49,6x65,5 mm Shaft Diameter 6 mm Weight 409 g Recommended model weight 3000 - 6000 g Propeller range 16 cells 16"x10"
20 cells 14"x10"
24 cells 14"x8"
Taking 3 cells = 1 Lipo (3.6-3.7 v) so that 24cells = 8lipos. My setup have one lipo more than the max, correct? I totally hear what you are saying and appreciate your help....and will see how I can change it (the problem is I'm sitting with two lipo packs...one of 5 cells and one of 4 cells.....HOW the hell do I get 6-8lipos out of that???lol

Thanks guys, I'll come back with the results as soon as I have time to do them, hopefully later today.

Take care
Bert

bert269
05-18-2006, 05:18 PM
Oh sorry I forget to add this to my previous message. 14" is about the max I can go with a prop length. Else my plane will looks like it's running on 'scaffulding'. My wheels only allow for a prop of 15" max (given no hard landings to use shock absorbing in the wheels and no long grass either!)

sigh!
Thanks guys, i'll follow with the results later as soon as I have them.

bert269
07-10-2006, 05:42 PM
Ok,

I must just give some feedback. I used 8 lipos (5s, 3s in series), each 4000mah on the 4130/16 setup and it flies like a dream. I get about 13-14mins flying time out of the packs and after I cooled them down, and recharge them, both still had about 25% charge left. About four times now the amount of current that was put back by the charger was below 3000ma to each pack.

The power is defenitly there when I needed it. The four times I have flown the plane now, the wind was quite gusty and it was good flights.

It just seems to me that I have a bit of a problem with the landing gear. (ok remember this is a trainer and I'm still the trainee!)...It seems to me that the front wheel strut is a bit inadequate. After each "reasonable hard landing", the front wheel strut is bent and I have to straighten it out. I think I need a thicker(or stiffer) wire for this strut, due to the weight of the lipo's and the motor....

I'm happy with the conversion. I don't know how this plane would have flown with the nitro motor, but I'm happy with what I have going.

Thanks everyone....

(PS. I'm already working on my next project, the Giles G202. Going to use the same setup for that plane when it's ready)