Need some elcectric advice

[schmleff]

I used to fly nitro heli's a few years back but am now looking at getting a trex to replace the blade cp I currently have.

I am a total electric aircraft noob. I don't know a 420 motor from a 430 motor. I don't have a clue about almost all of this stuff. If the battery is 11 some odd volts, how does the reciever get 4.8?

So, can someone point me in the right direction to learn this stuff? Im getting advice in other forums but I am too noob to even know what I am being told.

Thanks!

[Bryan]

Unlike your Blade that has the receiver, electronic speed controller (esc) and battery eliminator circuit (bec) all in one box, the t-rex uses (or can use) separate components.

The bec is what breaks down the voltage to run the servos, gyro and receiver. Typically, the bec is built into the esc.

As the name infers, the bec reduces the weight and complexity of the machine by eliminating the separate battery pack that would be used to run the lower voltage components.

I think that you are already pointed in the right direction, just keep reading and asking questions. That’s how I’m learning :wink:

[schmleff]

I was recommended to buy a 450L motor for my trex. I go to pick one out and they list different kw ratings. What is that about? I am sure its power but how do I know which one to get?

[Bryan]

Short answer because I'm at work. The Align 450L will work great in a trex.

If you are seeing different specs for the 450L, post the links that you are looking at and we'll sort it out for ya.

[schmleff]

Here is the Align site I was looking at. http://www.align.com.tw/shop/index.php?cPath=22_67

Three different 450L motors listed.

[spork]

Jeff,

Our resident expert "Finless Bob" is a big fan of the 430L motor. It's a VERY common motor for the T-Rex. If you go with an Align motor I think this is definitely the one you want. It's the 430L with silver end-caps (not gold), and 3550 kV (the very first one on the link you posted)

Incidentally, you're going to want to make sure and get the right Lipos and such. Most of us use a 3-cell LiPo pack with 2100mah or more. You'll also want it to have 15C discharge rate or more. The Thunder Power Pro Lites are probably the most common. Apex makes one that's a tad heavier, but about half price. Incidentally, the area you really need to get right is care of LiPo's. There's plenty to read on these forums, but the high points are:

- DON'T over-discharge (try not to take out more than 80% capacity)
- Charge them with a LiPo charger (not NiCad, not NIMH), and use a balancer
- Don't charge them in anything you're not happy to see burned to the ground.
- Don't wander very far while they're charging.


...they list different kw ratings. What is that about? I am sure its power but how do I know which one to get?

Actually the kV gives you the no-load RPM of the motor. It's expressed in RPM per volt. So a 3550 kV motor would spin at 35,500 RPM on 10 volts with no load. It's not really more or less power, it's more like electronic "gearing" and has to do with the number of winds of wire on the armature. More winds gives more torque and less speed. Fewer winds gives more speed and less torque.

[Bryan]

Ditto what Rick said.

[schmleff]

Jeff,

Our resident expert "Finless Bob" is a big fan of the 430L motor. It's a VERY common motor for the T-Rex. If you go with an Align motor I think this is definitely the one you want. It's the 430L with silver end-caps (not gold), and 3550 kV (the very first one on the link you posted)

Incidentally, you're going to want to make sure and get the right Lipos and such. Most of us use a 3-cell LiPo pack with 2100mah or more. You'll also want it to have 15C discharge rate or more. The Thunder Power Pro Lites are probably the most common. Apex makes one that's a tad heavier, but about half price. Incidentally, the area you really need to get right is care of LiPo's. There's plenty to read on these forums, but the high points are:

- DON'T over-discharge (try not to take out more than 80% capacity)
- Charge them with a LiPo charger (not NiCad, not NIMH), and use a balancer
- Don't charge them in anything you're not happy to see burned to the ground.
- Don't wander very far while they're charging.


...they list different kw ratings. What is that about? I am sure its power but how do I know which one to get?

Actually the kV gives you the no-load RPM of the motor. It's expressed in RPM per volt. So a 3550 kV motor would spin at 35,500 RPM on 10 volts with no load. It's not really more or less power, it's more like electronic "gearing" and has to do with the number of winds of wire on the armature. More winds gives more torque and less speed. Fewer winds gives more speed and less torque.

Cool, I had my Blade charging in the minivan, which I would be more than happy to see burned to the ground.

Someone in another forum said that I should go with the 450L. What kv should I use for that motor?

BTW, my blade cp sucks in the wind. The tail is way to slow. It just wags back and forth. I have been practicing nose in and doing well but its hard to hover normal with the tail swinging all over at every little breeze. Makes me want to get my nitro going again till I can get a Trex.

[spork]

Someone in another forum said that I should go with the 450L. What kv should I use for that motor?


Sorry, I'm completely unfamiliar with the 450L. I'd personally be more inclined to go with the 430 if only because our resident expert knows everything there is to know about it, and seems to really like it. Perhaps the guy on the other forum could tell you what kV and what pinion works well on the 450L. You'll have to let us know how it works out.

[WayneBrown]

My typo, I meant 430L, it came out 450.. go figure. :?

[Bryan]

Yeah, me too :lolol

Sorry Jeff, that was my bad. :oops:

I think we all agree that you won't go wrong with the first 430L that is on your link.

Next question...if you dare :cool:

[Bryan]

PS. You do know to shop around for your best price, right?
Getting the best price is the 'sport' part of this hobby.

[schmleff]

PS. You do know to shop around for your best price, right?
Getting the best price is the 'sport' part of this hobby.

Very interesting you bring that up. I can buy the 450xl online for about 165 shipped. I can buy it at the local hobby shop for 189. $24 bucks is a good bit of money. However, I buy CA, airplane kits, heli parts, and all kinds of stuff. The local shop supports the community buy hosting events and hosting winter fly ins. They also have a couple of slot car tracks, indoor rc tracks and an outdoor dirt track.

I stopped to see if they had parts for the T-rex and they stock tons of it. The owner of the store has one.

Call me dumb, but if the local store supports what I am doing, I tend to support them. After all, $24 bucks is not much to pay to keep a store in town.

[spork]

Call me dumb, but if the local store supports what I am doing, I tend to support them. After all, $24 bucks is not much to pay to keep a store in town.


I think that's a good attitude. But personally, I'd make sure the owner knew you were buying locally to support the shop. The fact that he owns a Rex is pretty key. Hopefully, you two will fly together. He might give you lots of good info.

RC