Starting Out with a T-Rex 450
This guide is intended to provide a complete list of the things you'll need to start out on the right foot with your T-Rex 450. Obviously, there are MANY choices for most of these items. This cannot be the final word, but it is guaranteed to put you on solid ground so you don't find you've either bought the wrong stuff or find yourself having to upgrade in just a few months. By following these recommendations you should end up in fine shape. No matter what gear you buy, you should study the Finless build videos available for free on HeliFreak.com. These are extremely useful. You'll learn a lot, and quite likely save yourself untold heartache. Plus Finless is available on HeliFreak to answer all our T-Rex questions - which he does - everyday. For a basic overview of wiring skip to the bottom of this page.
First a few acronyms
TX = transmitter
RX = receiver
ESC = electronic speed control
3S = a battery pack with 3 cells in series
LiPo = Lithium-Polymer battery pack.
eCCPM = electronic cyclic-collective pitch mixing (3 servos typically will attach directly to swashplate)
I'll keep this simple. You'll need three servos for your swashplate (cyclic and collective). Use the Hitec HS-56 or HS-65's. I prefer the HS-65's. If your heli uses eCCPM you may want to opt for the MG (metal gear) version of the HS-65. This will save you from stripping servo gears more often than not on a crash (you WILL crash). Stripped servo gears are less common on the HDE version of the heli. On the tail you should consider the Futaba 9650. This is an excellent digital servo. You won't need to upgrade. But it's not inexpensive. I have the Hitec HS-50 on my tail. It works fine for me, but it's no match for the 9650 once you get into big-time 3D flying. The tail servo is not a good place to experiment. I can recommend the HS-50 for starting out, or the Futaba 9650 for anything at all. If you choose something else, you're on your own.
Mount the tail servo on the left side of the tail boom. This will protect it from a blade strike in a crash.
Don't skimp on the TX. You can go higher-end than my recommendations. But if you go lower, you'll upgrade sooner than you want.
Futaba 7CHP: This is an FM/PCM transmitter. It has excellent features at an excellent price. If not for the new Spektrum radios this is the only one I'd mention. I think it's more full-featured than the Spektrum DX6, but doesn't boast some of the spectacular features of the spread-spectrum technology. The Spektrum DX7 has all the features you need, the spread-spectrum technology, and a price to match. Using the Futaba 7CHP transmitter with a Futaba PCM receiver will give you a great glitch-proof setup. But you still need to coordinate frequency channels with the other pilots. If you won't be flying in a crowded club environment, this radio would be tough to beat for the price. It will serve you on the T-Rex and bigger helis for a long time to come.
Spektrum technology advantages:
· No shootdowns
· No RF glitches
· High performance/low latency
· No waiting for your channel to come free
Spektrum DX6 (DSM) - ParkFlyer
The DX6 is an entry level 6-channel computer radio (Plane+Heli) suitable for ParkFlyers and small electric helicopters. It is compatible ONLY with the AR6000 Rx. While there is no issue about range (tested to thousands of feet), for various reasons the manufacturers recommend it's use be limited to park-flyer type helis and planes. Some feel the features of this radio are just a bit limited, particularly if you intend to go to bigger/nitro helis later.
Spektrum DX7 (DSM2) - Unlimited
The DX7 is a mid-range 7-channel computer radio (Plane+Heli) with the second generation spread spectrum technology (DSM2) which gives full range capability and can be used in any kind of model aircraft at all when combined with the AR7000 Rx. The DX7 can also be used with the AR6000 (DSM) or AR6100 (DSM2) ParkFlyer receivers but application is then restricted to those kinds of models. This is an excellent full-featured radio, that will serve you for a long time to come.
R146ip: If you go with the Futaba transmitter, I recommend the Futaba R146ip receiver. This is a single-conversion PCM receiver. Because it is single conversion many people don't feel it belongs on the big nitro helis (because of potentially limited range), but on the T-Rex it's bulletproof. It's small, light, and impervious to those ubiquitous glitches that you could spend your life hunting and fixing. There are those that feel that using a PCM receiver "masks" an underlying problem, and therefore you shouldn't use one until you've nearly perfected your wiring and layout while using an FM receiver. Many (including myself) believe there's no reason to start out with an inferior technology (FM/PPM) before going to PCM. For my money the ticket is to take care in placement of your components and wires, use a ferrite ring, and a PCM (or Spektrum) receiver, and call it a day.
(DSM): 6-channel ParkFlyer Rx compatible
with both the Spektrum DX6 and DX7. Very compact and only 7g.
AR6100 (DSM2): Diminutive 6-channel ParkFlyer Rx compatible only with the Spektrum DX7. Even tinier than the AR6000 and only 3.5g.
AR7000 (DSM2): Full range 7-channel Rx compatible only with the Spektrum DX7. A compact but novel two-part design with a main Rx connected to a tiny satellite Rx by a 15cm cable. It is the use of these two Rx mounted at least 5cm apart that gives the "full range" capability. Still smaller than most PCM Rx and only 14g.
Futaba GY401: This is it. Probably the most common gyro in use on the T-Rex. It is an excellent gyro with an excellent feature set. It can be used in proportional or heading hold mode (and switched from the transmitter). You can also control the gain from the transmitter. It is designed to take advantage of the performance of digital servos, but can be used with analog servos as well (just flip the switch). There are more expensive gyros, but until you're winning the nationals on a regular basis you won't need more than this on your T-Rex. This is the one to go with.
Futaba GY240: The 240 is the little brother of the 401. It can also be used in proportional or heading-hold mode. It is a solid performer, but lacks some of the excellent features of the 401. It does not have any specific support for digital servos, but can still be used with them (without taking full advantage of their potential). If you bought a T-Rex with this gyro, or if your budget is very tight, you will do just fine with this unit. However, if you have the choice, spend the few extra dollars for the 401.
Whichever way you go, you’ll want to protect your investment by mounting it inverted on the bottom of the tail-boom. This will protect it from a blade strike in a crash. Rdlohr on HeliFreak sells a nice mount for this purpose. Many like to use a Velcro strap for safety when mounting inverted. I don’t.
Battery technology is changing rapidly. This is a good thing. For now a few things are no brainers... You'll want Lithium-Polymer (LiPo) batteries. These batteries pack a LOT of power into a small, lightweight, package. NiCads, NiMHs, etc. are not going to cut it on your T-Rex. So here are the specs you'll want for starting out:
· Configuration: 3S-1P (sometimes refered to simply as "3S"). This refers to 3 cells in series, and just 1 string of them. 4S-1P (or 4S) would be 4 cells in series. Some folks run 4S on the T-Rex, but you don't need to get into that to start out. Most of us never do. Just by way of explanation... 3S-2P would be 2 parallel strings of 3 cells in series (not that you'd ever do this on a T-Rex). Make sure your batteries have a balance tap (more on that below). Most people use the Dean's Ultra connectors for the primary pack output. Some packs don't come with connectors - so check, and get them if you need to.
· Capacity: somewhere in the neighborhood of 2000 mah (milliamp-hours). Most suitable batteries will fall between 1800 and 2200 mah.
· Current capability: You'll want a pack with at least 15C continous and 20C burst capability. That should be plenty good for starting out. Some packs now are coming out with 25C continuous or higher. You don't need this, but it won't hurt either. This refers to the rate at which they can deliver current. Basically 1C means they can run themselves dry in 1 hour. 2C is twice as much current (2xcapacity/hour), so they could run themselves dry in 30 minutes. A 15C battery could run itself down in 4 minutes. Of course we don't use the battery at its maximum capacity for the entire flight, so we typically get anywhere from 6 to 10 minutes of solid flying on a pack. DO NOT DISCHARGE A LIPO TO LESS THAN 20% OF IT'S RATED CAPACITY (more on LiPo alarms and timers later).
· What to get: There are now any number of packs that at least seem to have excellent specs and excellent prices. I think the jury is out on whether the budget packs are as robust as the big name packs. If you don’t want to experiment in this area you should consider Flight Power and/or Thunder Power packs. A search on HeliFreak will turn up a ton of info on LiPo options. But if you follow these specs you should be on solid ground.
Whatever you settle on, get at least 2 packs.
One could write an entire book on the pros and cons of the various chargers, power supplies, balancers, and such for LiPo's. I'm not going to do that. For now I'm going to tell you what I use. It's a solid setup, but I don't claim it's the best or the only good one.
Triton Charger: This will charge and discharge LiPo's, Lead-Acid, NiCad, and NiMH's. It has an optional thermal probe (which you should get and use). It's easy to use, and provides a wealth of info on battery health and condition. It takes 12 volts as input (as many do these days), so a separate A/C power supply or battery is required. I don't care what LiPo charger you use, but under NO circumstances should you charge LiPo's with a non-LiPo charger.
Balancer: I use the Thunder Power 205. This plugs into the balance tap of your LiPo pack. You can balance while charging or standalone.
Power Supply: I use a power supply out of a PC. This is a common enough approach, but there are also plenty of 12 volt supplies available for this purpose.
Container: LiPo's can ignite or explode. NEVER leave a LiPo unattended while charging. Houses and cars burn down. Try explaining that to the wife. Always charge your LiPo's in a fireproof container (like a steel ammo box or ceramic LiPo charging container). I'm not kidding.
For starting out you'll want to use the Align 325 Pro Wood blades. They are an excellent blade at an excellent price. You may later decide to try carbon blades, but not before you've gone through at least 10 sets of these woodies at $12 a set. Whatever you do, don't use the Align fiberglass blades. You could use them for stirring paint in a pinch, but don't expect a great paint job if you do.
Again, there are a million choices. You won't go wrong with the Align 430L. For many experienced pilots this is the motor of choice. It's inexpensive and powerful. There are plenty of other good motors as well.
Lots of choices here too. Many like the Align 35 amp ESC (electronic speed controller). Do the "Finless Heat Sink Mod" if you go with this unit. It's a solid, simple unit that will serve you well.
· Pitch guage
· Blade balancer
· Ball-link pliers
· Ball-link resizer
· Allen wrenches
· Long nose pliers
· Jeweler's screwdriver set
· Hobby knife and a packet of blades
· Align one-way bearing removal tool
· Double-sided foam tape, self-adhesive velcro, blue loctite, cable ties, CA (cyano-acrylate or super-glue), velcro straps
LiPo Alarm: I like to use a LiPo low-voltage alarm to let me know when I'm done flying before destroying a LiPo pack. Some folks prefer to time their flights. I try to remember to time, but my alarm lets me know when my packs are getting dangerously low regardless of initial charge state, if I forget to start the timer,... You can make a LiPo alarm from simple plans and Radio Shack parts for about $10. Or you can buy one for $20-$30. Efliernz sells a simple unit on HeliFreak.com.
Simulators: Several flight simulators are available for your PC. There is a very significant range in price, and a somewhat less (but significant) range in quality (in my opinion).
The biggies are RealFlight/G3.5, Reflex/XTR and Phoenix. G3 is the most expensive and needs a really beefy PC and graphics card. Phoenix is the cheapest and newest and is the flavor of the month. All three are very good but only incrementally better than the much less expensive ClearView. All of these need a decent 128MB 3D graphics card. Finally, there is FMS (Flight Model Simulator). FMS is a free download. Plenty of people feel it is a big step below the others. I personally find it to be a very impressive simulator for the price (far better than a $200 simulator I purchased a few years ago). If you download FMS, you’ll want to purchase a USB cable to connect your TX to your PC. You can get this cable from www.milehighwings.com
Ferrite ring: The ferrite
ring is basically a noise filter. They're small, cheap, and a necessity. Put
one on the wire between your ESC and RX. Take as many wraps through the ring
as possible (5?). This will reduce/eliminate the single biggest noise source
into your RX. Even then, you'll want to take care to keep your RX as far as
possible from the motor, ESC, and gyro.
Note: I’m told a ferrite ring is neither needed nor recommended for a Spektrum Rx. It shouldn't do any harm, but it won't do any good, adds weight and is something else to find a spot to mount on a crowded airframe.
So, what belongs in your crash kit? Obviously your crash may be more creative than my imagination, but I’ll try and hit the high points.
You'll have a 3S LiPo battery. That battery will plug
directly into the ESC through the 2 fat wires coming out of the ESC (usually a
black and a red). The ESC will also have a three-lead "servo wire"
coming out of it. That wire plugs into the throttle channel of your receiver
(but should first be wound several times through a ferrite ring). On a Futaba
RX that would be channel 3. This serves two purposes... it powers the receiver
and servos with 4.8 volts (regulated down from the 11.1 volt LiPo pack), and it
communicates the throttle command from the RX to the ESC. You'll have 3 fat
wires coming out of the ESC. They go to your brushless motor. These leads can
go to the motor in any order. If the motor spins the wrong direction, swap any
two of those three leads and you'll be good to go.
Your gyro will have two "servo wires" coming out of it. One with a connector that will plug into your RX "rudder" channel (channel 4 on a Futaba RX). The other 3-wire lead plugs into your rudder servo (which will be mounted on your tail-boom). On some gyros there will be a third lead (frequently with only a single wire). That will plug into an aux channel of your RX for controlling the gain and mode of your gyro.
We're almost there now.
You'll have three more servos. Each will have a 3-lead "servo wire". these will plug into your RX Aileron, Elevator, and Collective Pitch channels respectively. On a Futaba these will be channels 1, 2, and 5 or 6 (can't remember which right now). If your bird uses eCCPM they will have to be mixed in your TX to perform the cyclic roll, cyclic pitch, and collective pitch functions. On the non-eCCPM birds each one does the job related to the channel it's plugged into.
Finally, your battery will have two fat wires coming out of it (usually red and black). Batteries frequently come with no connector on these leads. You’ll have to add your own connectors to these leads and to the two corresponding leads on the ESC. Most people use the Dean’s Ultra connectors. Your battery should also have a short lead coming out of it with 4 leads going into a small connector. This is a balance tap. It’s not used during flight. Instead it is used to balance the battery (before, during, or after charging – this is a big topic by itself). Some systems charge the pack through this “tap”.