parabellum

I'm thinking of converting my tf mustang into electric.
and now have 4stroke 90 on it.

I'm new to electric, so don't know much.

I guess I need a motor, esc, and batteries.

any recommandations?

is li-poly better than nimh?

parabellum

I was going through the posts and it seems the following will be good choices for electric conversion

motor = AXI 4130/20

esc = Jeti Advance 77 Controller

batteries = kokam 2000mAh 3 pack


question is, how many kokam 2000mah 3 pack do I need?

what is the voltage that axi motor can handle?

since kokam 3 pack is 11.1v, do I only need to connect them in
parallel to increase ampereage therefore the running time?

or do I have to increase the voltage?

Matt Kirsch

My Feedback: (21)

You're on the right track, but at the wrong station

Voltage is kind of equivalent to cubic inches in an engine. More Volts, more power.

With that Top Flite warbird, you'll need at least 1000 Watts of power to fly it at 10lb. The AXi 4130 series is easily capable of that, but not on 11.1V. The motors will only handle 40 Amps continuous, and 40 Amps at 11.1 Volts is only 444 Watts. A little less than half of what you need. Since you've already hit the maximum current rating of the motor, your only option is to increase the Volts.

To get 1000 Watts at 40 Amps, you need about 25 Volts. On a LiPoly, you probably want 7 cells in series to get an average of 25 Volts throughout the flight. It'll start off at 29.4 Volts and end at 21 Volts.

As you point out, you will need to put multiple packs in parallel to get the Amperage capacity. Instead of Kokam 2000 cells, I'd use 1500s. The 1500s are more popular and less expensive. Each 1500 pack is capable of sustaining 12 Amps, so you need four 7-cell packs in parallel to power the plane.

These packs, I'd make them by building them up from two and three-cell packs, using Kokam series and parallel connectors.

I'd also think about using the 4130/16 motor instead of the 4130/20. You may not have enough ground clearance for the prop that the 4130/20 will turn at this power level. Either motor will work, with the right prop.

parabellum

thank you for the information.

I'm thinking of using 15inch varioprop with 4 blade.

what is the maximum voltage that these motors can handle?

Matt Kirsch

My Feedback: (21)

All the data on these motors can be found at http://www.modelmotors.cz.

You'll see them rated in terms of cell count. The 4130/16 is rated for 16-24 cells. The 4130/20 is rated for 20-30 cells. These are NiCd cells, rated at 1.2 Volts each, and are 1.4 Volts each fully charged. You do the math

parabellum

If I want to swing scale size 4 blade prop on 60 size warbird, would that be possible?

let's say I want to use 15in 4 blade prop. model weights 10-12 lbs.

is there some combination of motor/reduction gear/esc/batteries that
will allow reasonable performance? and if so make and model of each component.

Matt Kirsch

My Feedback: (21)

There are literally hundreds of different combinations that'll do that, but you could be a little nicer in your request... "if so, make and model of each component" You could've at least phrased it as a question instead of a command

Since we're talking warbirds, 100 Watts per pound is a good power loading to shoot for. You're looking for 1000 to 1200 Watts. 30 cells at 40 Amps. So that's either 30 NiCd/NiMH cells or 9 LiPoly cells.

I have the perfect motor for you. AXI 4130/20. The specs at http://www.modelmotors.cz say it can turn a 14x10 2-blade prop at the power level you'll need. For each blade, drop an inch in pitch or diameter, so it should be okay on a 14x8 4-blade prop, or perhaps even a 15x6. Finding either of those props might be tough, though, as 4-blade prop selection is quite limited.

parabellum

thank you for the information.


I would like to use 15inch 4blade, if I could I would like to swing even bigger prop, like 18inch 4blade.

would that be possible? I know I can use smaller prop, but I don't want to.

main reason for moving to electric is because there is no reduction gear
available for glow engines (there were some couple decades ago, and rcv)
and without reduction gear, it is not possible to swing scale size 3 or 4 blade prop with glow engines.

redxfred

My Feedback: (3)

Matt,
Thanks for taking the time to reply to all this. I'm sure it's frustrating, but I got a lot of "Basic Good" out of your advice here too. Incidentally, the dates on the posts are coming up as 4 days in the future... perhaps the calendar function needs a reset.

ray foley

reality versus desires, sometimes problematical. Since you will be doing some fiddling with props, batteries, and a specific motor, a wattmeter will be essential to the process. That is if you don't want the magic smoke to get loose from you motor. Electricalc or motorcalc will also help a lot.

We often have to adjust to reality, it sucks but so it goes.

good luck -rjf