RE: Ask your electric FAQs HERE!  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       


Hangar 9 46% TOC Ultimate 10-300
Seller:  wardie
Details:   $8,000.00   |  10/1/2008   |  Classified Ad
We will rotate YOUR AD in this spot if you select "Forum Featured" when placing or editing your ad!

All Forums >> Electric Aircraft Universe >> Electric General Discussion >> RE: Ask your electric FAQs HERE!
Page: <<   < prev  1 [2] 3 4   next >   >>  

Login
Message << Older Topic   Newer Topic >>
RE: Ask your electric FAQs HERE! - 6/1/2004 5:22:36 AM   
ZimboRaider



Posts: 430
Joined: 8/28/2003
From: AshburtonCantebury, NEW ZEALAND
Status: offline 		Matt-

Are you going to publish this on a seperate page with illustrations(such as in the RCU University) or are you going to leave it as it is?

Some more:

-What is 3D?

-What are the pros and cons of Lithium Polymers?

-How do I know if I need a gearbox?

Zimbo

_____________________________

Be worried when the object you are assembling looks normal but there are a few screws and/or devices left in the box:)

(in reply to Matt Kirsch)
       Post #: 26

RE: Ask your electric FAQs HERE! - 6/1/2004 1:19:52 PM   
Matt Kirsch



Posts: 7037
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline 		Eventually, I plan on compiling this into a "real" FAQ, and sticking it somewhere. I have a few places in mind, and all involve unmentionable places on people I don't like, but I digress Yes, if RCUU will have it, I'd like to post it there.

Guys, I don't have to answer all the questions. There are several unanswered ones in this thread already. Just be sure to quote the question to make it easier on me when I go to compile it

For example:

quote:

What is the difference between brushless and brushed motors?


Motors operate on the principle of using electromagnetism to push and pull against permanent magnets. To do this, they need a way to switch the direction of current flow, or "commutate," to reverse the polarity of the electromagnets as they approach the permanent magnets.

On a brushed motor, the permanent magnets are fixed, and the electromagnets rotate. Current is transmitted to the electromagnets through a pair of metal contacts that brush against a commutator. The commutator is a sectioned band that's wrapped around the motor's shaft (properly insulated of course), with each section connected to one end of an electromagnet. As the motor rotates, the brushes move from section to section on the commutator, switching the polarity of the electricity so as to push and pull against the fixed permanent magnets.

On a brushLESS motor, the permanent magnets rotate, and the electromagnets are fixed. Instead of brushes, brushless motors have a computerized controller that handles the commutation. The controller knows when and how to energize each electromagnet so as to push and pull on the permanent magnets at the appropriate times.

(in reply to ZimboRaider)
       Post #: 27

RE: Ask your electric FAQs HERE! - 6/1/2004 1:50:25 PM   
Matt Kirsch



Posts: 7037
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline
quote:

How do I know if I need a gearbox?


The need for a gearbox, and the ratio of said gearbox, depends on the motor, how many cells you're using to power it, and the propeller you're trying to turn. Generally speaking, "outrunner" style motors do not need gearboxes, while most conventional motors do. This is due to the large diameter of the external rotor on outrunner motors, and the tremendous amounts of torque they produce because of that large diameter rotor. Conventional motors often need to use gearboxes to multiply torque to spin larger propellers.

What really tells the tale is "Kv," the RPM per Volt rating of the motor. Motors with low Kv ratings, regardless of design, are generally used as direct drive while motors with high Kv ratings are generally used with gearboxes.

In most cases, performance and efficiency benefit from using the largest diameter propeller that will fit on the airplane. The task is to find the correct motor/gearbox combination that spins that prop given the Volts and Amps you determined would power the plane earlier (see previous questions from Bobsean). To that end, *Calc programs like Electricalc, Motocalc, and P-Calc, along with information from manufacturers' websites is a tremendous help. Some manufacturers are thorough enough to provide example applications for their motors; you can often find a setup that's pretty close to what you want and tune it by using a slightly larger/higher-pitched prop or by changing the cell count in the battery.

(in reply to ZimboRaider)
       Post #: 28

RE: Ask your electric FAQs HERE! - 6/1/2004 7:17:34 PM   
Wayne Miller


 

Posts: 977
Joined: 9/10/2003
From: DrumboOntario, CANADA
Status: online 		Hi,

Matt: I tried to send you an email to OK this post, but it was returned saying to try later - you may want to check your email address.

I've been following your new thread on electrics and thought my RCU acronym list may be a good reference for the new people. I built it to clarify some of the terms used here at RCU, I found some terms confusing when I first joined and thought this list may help someone else. The latest list is always at the end of the post.

The address is as follows:
http://www.rcuniverse.com/forum/m_1527996/mpage_3/key_wayne%2Cmiller/tm.htm

Best regards,

Wayne Miller

(in reply to Matt Kirsch)
       Post #: 29

RE: Ask your electric FAQs HERE! - 6/3/2004 1:12:10 AM   
ConfessChrist


 

Posts: 1
Joined: 5/21/2004
From: Westminster, CA, USA
Status: offline 		Hey!

Let me start of by saying I'm brand new! Never flown, not once. This community has already been a great place for researching this interesting hobby!

Anyways, here's my question (I don't believe it has been mentioned yet). I notice that all the electric RTF (remember, i've never flown) kits online have specification for flight duration times. The gas(glow? what's the diff?) kits do not have this detail on the pages I've seen. So, how does the flight duration of an electric plane compare to that of a gas plane? Is it shorter? This is basically my only concern with an electric plane.

Thanks in advance!
[Chris]

(in reply to Wayne Miller)
       Post #: 30

RE: Ask your electric FAQs HERE! - 6/3/2004 12:47:51 PM   
Matt Kirsch



Posts: 7037
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline
quote:

ORIGINAL: ConfessChrist
So, how does the flight duration of an electric plane compare to that of a gas plane? Is it shorter?


Flight times can be shorter, the same, or longer, depending on how much effort (and sometimes money) you put into the power system. Many park flyers will fly for over 10 minutes on inexpensive brushed motors and NiMH batteries. The same size plane with a badly-designed system might fly for 3-4 minutes on the same battery.

Duration has always been a concern with electric airplanes, because there has traditionally been no way to increase the flight duration without incurring a severe weight penalty. The only answer was bigger and heavier batteries, while a glow-powered plane's duration could easily be extended by installing a slightly larger tank. Pounds vs. ounces.

Along came NiMH batteries. These offer signifigantly higher capacities for the same size and weight as NiCd. Double the capacity in some cases, but more typical is 50% to 66% more. With a well-engineered power system, 10+ minute flights are obtainable.

Within the last two years or so, Lithium-based battery technology has come on the scene. The popular Lithium-Polymer, or LiPoly, or LiPo :P cell offers five times the capacity of a NiCd in the same physical space so ungodly long flight times are possible without the weight penalty.

(in reply to ConfessChrist)
       Post #: 31

RE: Ask your electric FAQs HERE! - 6/4/2004 5:08:39 AM   
adhsooner


 

Posts: 26
Joined: 3/4/2004
From: coweta, OK,
Status: offline 		What is the best glue to use on foam?

(in reply to Matt Kirsch)
       Post #: 32

RE: Ask your electric FAQs HERE! - 6/10/2004 7:00:13 PM   
predator500


 

Posts: 84
Joined: 3/9/2003
From: sarasota, FL, USA
Status: offline 		does anybody have a list of the equivelent electric motors to 2 stroke nitro engines? It would come in handy for me.

Colin C

(in reply to ConfessChrist)
       Post #: 33

RE: Ask your electric FAQs HERE! - 6/10/2004 7:45:11 PM   
Matt Kirsch



Posts: 7037
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline
quote:

ORIGINAL: predator500
does anybody have a list of the equivelent electric motors to 2 stroke nitro engines?


Unfortunately, there is no such list. There are so many motor on the market right now, and more coming out all the time, that such a list would be impossible to maintain, even if such a list were useful.

The real issue is that every motor is capable of flying a wide range of airplanes, producing a wide range of power. Through the use of different cell counts, gear ratios, and propellers, you can get wildly different amounts of power, thrust and speed out of a single motor. As an example, a certain motor direct drive on 6 cells might be barely adequate for flying a 2lb, .15-sized combat plane. Up the cell count to 10, throw a gearbox and huge prop on it, and it will easily handle a 5lb .40-size trainer.

Because the battery is where the power comes from, it's quite easy to draw up some rough equivalencies based on cell count (Volts) and Amps. The cell count is based on 1.2V/cell NiCd and NiMH technology:

.15 ~ 8 cells @ 30 Amps
.25 ~ 10 cells @ 40 Amps
.45 ~ 16 cells @ 40 Amps
.61 ~ 20 cells @ 45 Amps

Motors are rated by their maximum capacity in cell count and current, so choosing a motor and ESC once you've figured out the size of the battery is just a matter of shopping.

(in reply to predator500)
       Post #: 34

RE: Ask your electric FAQs HERE! - 6/10/2004 7:51:45 PM   
Matt Kirsch



Posts: 7037
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline
quote:

ORIGINAL: adhsooner
What is the best glue to use on foam?


What's best is a matter of personal preference. Many adhesives will work on foam, including white glue, yellow carpenter's glue, epoxy, foam safe CA, and polyurethane glue. Epoxy is one of the more popular choices as it is relatively inexpensive, and cures in a reasonable amount of time. Foam safe CA, though it cures quickly, is fairly expensive and does not have much of a shelf life. Yellow, white, and polyurethane glues require the parts to be clamped overnight.

Adhesives like regular CA (cyanoacrylate), and contact adhesives like 3M77 and contact cement contain solvents that will melt foam. Watch out for products that contain acetone, toulene, MEK, and other industrial solvents. Gasoline also does a number on most foams.

(in reply to adhsooner)
       Post #: 35

RE: Ask your electric FAQs HERE! - 6/11/2004 2:09:08 AM   
skater_719


 

Posts: 380
Joined: 10/22/2003
From: lAkE gEnEVA, WI, USA
Status: offline 		what motor could replace the stock motor in an wattage extra 300, its just a 180 motor and is too small, any suggestion, answers would be greatly apriciated

(in reply to Matt Kirsch)
       Post #: 36

RE: Ask your electric FAQs HERE! - 6/18/2004 1:24:56 PM   
Matt Kirsch



Posts: 7037
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline
quote:

ORIGINAL: skater_719
what motor could replace the stock motor in an XXXX XXXXX, its just a XXX motor and is too small, any suggestion, answers would be greatly apriciated


I'm going to answer this as if it were a more generic question.

When an airplane is underpowered, the first thing many people do is assume it's because, "the motor is too small." The physical size of the motor has little to do with power, if anything.

A neat aspect of electric flight is that the motor is merely a conduit through which the power flows. Motors can handle wide ranges of power, and you can increase or decrease power at will. Increasing the amount of power available to the plane is as simple as changing the stock propeller for a larger one. Your next simplest option is to add a cell to the battery. Either of these will make a dramatic difference in available power, without a "bigger" motor.

You can also go the "bigger motor" route if you like, but it's not as simple. What you need is a motor with a slightly higher Kv rating than the existing motor, that can handle the Volts and Amps being applied to it. This motor will not necessarily be physically larger than the existing motor, and may in fact look identical, or may be physically SMALLER!

The Kv rating is RPMs per Volt, how fast the motor turns when one volt is applied across the terminals. If you don't know the Kv rating of your motor, there isn't an easy way to find out, so you'll need to explore other options.

The motor is only too small if it cannot handle the power being pushed through it, and burns up. You need to have a rough idea of the motor's limits, and where you are in relation to those limits, before increasing propeller size or adding cells. A motor change usually requires a complete re-evaluation of the power system, the possible use of a different propeller, different ESC and/or a different battery due to the different characteristics of the new motor.

(in reply to skater_719)
       Post #: 37

RE: Ask your electric FAQs HERE! - 6/19/2004 6:13:12 AM   
jackplanet514


 

Posts: 5
Joined: 4/28/2004
From: Salt Lake City, UT, USA
Status: offline 		I think I am having chatter?

So my generic question is what is chatter and what causes it?

I have a HiTec rec. with HiTec servos and an E-flight 10-amp ESC.
When I plug in my GWS 9.6v/730mAh Ni-Mh battery the servos chatter (vibrate). However when I plug in 7.2v/600mAh Ni-Mh battery everything seems to work fine.

Thanks in advance.
JackPlanet

(in reply to Matt Kirsch)
       Post #: 38

RE: Ask your electric FAQs HERE! - 6/21/2004 1:53:25 AM   
onecb


 

Posts: 27
Joined: 3/2/2003
From: Kearns, UT,
Status: offline 		I am considering getting into electric flight. I used to race electric cars and I have several 2000 mil amp nicad sub C cells. and several ESCs left. I was wondering if it is possible to use these for electric flight? If so what kind or size motor and what size plane would these power respectively? Thanks in advance.
Alvin

(in reply to jackplanet514)
       Post #: 39

RE: Ask your electric FAQs HERE! - 6/22/2004 1:33:01 PM   
Matt Kirsch



Posts: 7037
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline
quote:

ORIGINAL: onecb
I am considering getting into electric flight. I used to race electric cars and I have several 2000 mil amp nicad sub C cells. and several ESCs left. I was wondering if it is possible to use these for electric flight? If so what kind or size motor and what size plane would these power respectively?


Several years ago, the only electric planes on the market were powered by car motors, car speed controls, and car battery packs. They flew like cars. If you could get them in the air, they were overweight and underpowered. Flights only lasted a couple of minutes because of the tremendous amount of current the motors were pulling just to get enough power to fly the plane. Everything came back HOT.

Car packs and car ESCs have traditionally not worked very well, mostly because the airframe has to be incredibly light to make up for the power system's unfavorable power-to-weight ratio. It's just very heavy for the power it puts out.

With cells the size of the ones in your car packs, it's very rare to see planes with fewer than 8 cells. Most have at least 10 cells. Even though the power systems are even heavier than the 6/7 cell packs (i.e. a 12 cell pack weighs twice as much as a 6 cell pack), the planes scale in a square and cubic fashion (i.e. double the dimensions of an airplane, you get 4 times as much wing area and 8 times the volume). The airplane's weight-carrying capability goes up as the size goes up.

On smaller aircraft, we use smaller cells, but a higher cell count like 8, and get our power from Volts instead of Amps. Running at a lower current (Amps) means we can use physically smaller and lighter cells, keeping the airplane's weight down. This makes for a better-flying plane and longer flights.

(in reply to onecb)
       Post #: 40

RE: Ask your electric FAQs HERE! - 6/22/2004 1:52:49 PM