Some things about Electrics Update
|I am not an authority by any stretch. There are people out there that "really" know electrics. Chris Stephenson, Will James, Clint Akins, Eric Larson and Finless Bob to name a few. Seek these guys out at funflys and watch what they do. Ask them questions.|
The T-rex 450 is so fast and so small that it can really fool you.
If you're use to bigger machines, be careful. This is especially true
when flying against a bright sky without a lot of light. In the evening
or on really cloudy days, make a real effort to keep the model within a
range that you can see exactly what it is doing. The wind will carry
these little models away very quickly.
When you mount your components, always keep the ESC and Motor wires as far from the antenna, receiver and servo wires as possible. On the T-rex 450 I mount my receiver up on the battery tray, the gyro between the frames at the rear, the battery on the lower tray up front and the ESC on the side. All of my servo wires are at least an inch from any of the motor/ESC wires and the antenna isn't near anything. Since I've been using a PCM receiver, I have had zero reception problems. I know the battery can be mounted higher to "improve the CG" but honestly, this thing rolls like a bullet anyway so I just can't see the difference. I've crashed quite a few times and I've never had any damage to any of the major components other than one battery (ouch). That was the worst crash I've ever had. Straight in nose down at terminal velocity. I don't really think it mattered where the battery was mounted in that one. It was going to be ruined anyway. The gyro is tucked away safely between the frames instead of up on top where the blades could beat on it in a bad crash. The ESC is out in the open where air can get at it and keep it cool. I like this setup.
Good solder joints ensure all the power gets through the connection. I've seen some really bad connections, including a guy that twisted the wires and put some duct tape on them. No solder at all!! Then he wondered why his motor wouldn't work. Learn to solder and solder well. If you're going to stay with electrics, invest in a good soldering iron or better yet, a good soldering station. Use heat shrink, not tape. Make it look good.
The tiny servos we use on the smaller models don't have the power to muscle past a sticky spot. Make sure your links are silky smooth. If you have a sticky link, you can try squeezing the link while it's on the ball. Use pliers without serrated jaws and be careful. If you have an appropriate sizing tool, that's even better. But go slow. The last thing you want is for the links to be too loose.
All Lithium based batteries such as LiPo or Lithium Ion are designed
to be charged at 1/C. That means that if the capacity of the battery is
1500 mah, 1C is 1.5 amps. You would set your charger to charge at 1.5A.
Normally, depending on the state of charge, it will take about an hour.
Use a charger that is specifically for Lithium batteries.
As a pack is charged and discharged the individual cells can become out of balance. In other words, each cell that makes up the pack is an individual. One might be full at 4.18 volts while another one isn't full until 4.22 volts. When you charge the pack, the charger is looking for 4.2 volts per cell to tell it the pack is full. If the pack above was a 2S1P pack, neither cell would be happy. Cell #1 would be overcharged and cell #2 would be under charged. A balancer's job is to make sure the cells end up with the same voltage. They will be very busy during a charge. They discharge the cell that's higher and send a little more juice to the one that's lowest until both are full and neither is overcharged. Sometimes you might end up with a little less than 4.2 volts per cell, but at least they are the same. The V Balancer takes control of the current coming from the charger and will terminate the charge when it should. That's one thing I really like about the V-Balancer. It can also balance the cells with no charger at all.
When we decided to start carrying electric helicopters, one thing that really bothered me was the cost of batteries. I heard that all the batteries are the same, so why would I want to buy a high priced battery? The fact of the matter is...you get what you pay for. If you want high performance and long life, buy a Flight Power or Thunder Power battery and treat it well. The worst thing you can do to your battery is over discharge it. No Lithium battery will forgive you for that. I said that is the worst thing but I'm assuming you know how to operate your charger. Charge a 3S pack on a 6S setting and you've ruined the battery. Always double check your settings! Most speed controllers have a battery protection setting. For the longest battery life, choose the high protection setting. Your flight times will be a little shorter, but your battery will love you. With cheap batteries, it seems like it doesn't matter what you do. They just don't last long. I have a pile of batteries to prove it.
ARF helicopters might be okay, but then again, they might not. It's always best to check for proper assembly. Okay, I know you aren't going to do that, but at least check the bolts that go in the end of the blade axle and make sure they have Loctite on them. Do that even if you don't do anything else! Keep a close eye on all of the bolts in the head. Among the things that I've seen come loose are: Blade axle bolts (goodbye blades), the bolts that hold the balls on the swashplate, washout bolts and main shaft collar bolts. I'm sure I'll see more as time goes on. I know you are really anxious to fly, but please take the time to do this.
I'm certainly not an authority on electrics, but I do know that the battery, motor and ESC should all do their job. When they do their jobs, they get warm. If one of these components isn't working as hard as it should, more than likely, you aren't running the right gear ratio and the other two components have to work harder and get hot. Assuming you are using a proven power package, consider another gear ratio.
Imagine waking up to find your hobby room on fire, or looking over and seeing your car on fire. Not a very pleasant thought, eh. Lipo fires happen every day. Some are because of bonehead mistakes like charging a 3S pack on a 6S setting. Some are unexplained. Do a google search for "Lipo fires" and see. My advice is to charge your packs outside on a fireproof surface far from anything you don't want burned up. If you can't do that, at least use a portable fireproof safe or Liposack. Right here in Corpus Christi we had a guy burn his whole house down charging a little park flyer battery. His whole house!! All of his stuff...gone! Don't let that happen to you. If you see white smoke coming out of your battery, it's about to catch on fire. Water only makes these fires mad. The only way to put it out is to smother it with sand or a fireproof blanket. A fire extinguisher will be handy to put out the fire as it spreads, but it won't make that battery quit burning. Right about now, you'll be wishing the battery was in a Liposack! If you're unfortunate enough to have a fire in your model, the best thing to do after you dial 911 is to watch it burn and protect the area around it the best you can without endangering yourself or others. I wish I owned all the property that had been burned up because of Lipo fires!
Electric models need to be oiled once in a while. I normally use Tri-Flow. Be sure to shake it up first. A drop between the blade grips and the head block will help keep the dampers lubed and the bearings in the grips operating smoothly. Just a touch on the washout bearings and any other bearings you can see is a good idea. Be sure to put a drop on the top of the swashplate and washout hub right where the mainshaft goes through them. A drop on the tail rotor shaft will keep the pitch slider working smoothly and a drop on each tail rotor blade grip between the grip and hub will help too. Some of this oil might sling off so get out your rag and be ready to clean things up a little. On my T-rex 450, I give the belt a good shot as well. Every once in a while, pop the main gear out and remove the sleeve that goes through the auto bearing. For this one I like to use a little automatic transmission fluid (the red kind). I flush it really good and assemble it wet. Wipe off any excess after assembly and put it all back together. After you get done oiling it, spin the main blades and notice how much better they spin. It's worth the time.
Sometimes we get a little cocky with the smaller machines. We might fly them a little closer to ourselves or others than we would a big machine. I'm just as guilty as anyone else. The thing to remember is that even a T-rex 450 can do serious damage if it hits you. If it were to hit you in the right place, it could kill you just like a big machine. BE CAREFUL. The only helicopter I know of that can't really do any serious damage is the Hirobo XRB. The Blade CX and CP, though not terribly dangerous, can cut you pretty deep. I know. Don't ask.
Shooting autos with a T-rex 450 is actually fun but I don't recommend it for learning autos, that's for sure. You get one shot at a good landing and that's all. There's no stopping and hovering involved. The collective move from negative to positive must be quick and low. If you are landing on soft grass, even a really botched auto probably won't hurt the machine much, if at all. Give it a whirl on a day when the wind is blowing steady at about 7-10mph. Get mentally prepared to go for it...lower the collective and hit the switch. Don't try to bail out or you'll strip your main gear. Keep it pretty close and have plenty negative available. I would recommend a minimum of 8 degrees. You'll probably use it all. Keep the model level and the collective low until the last minute. It's a challenge, but it's worth it. Most guys haven't ever tried one and never will. They just don't know what they're missing!
The guy that burned his house down bought a new house and proceeded to burn that one down too! He's still flying electrics. Another customer burned his Idaho mountain home to the ground. Please be careful. Neither one of these guys are dumb or careless. They just weren't paying attention and both broke rule number one... always be nearby when you're charging a lipo.
The guy in Idaho had his battery in a Liposack. It burned right through it. It took a while and if he had been close by, it would have helped, but the end result was a pile of charred remains where a beautiful mountain home used to be.
I have changed all of my models to 2.4 Ghz and I can only say...why didn't I do that sooner! I still mount my receivers in the same place and I have had ZERO problems with reception.
I've watched quite a few guys doing autos with the T-rex and other 450 size machines. Most of them use too much negative in the descent. You need a decent amount, but there's no need to slam it all the way to the bottom. Come down at a reasonable speed with a good flare at the bottom and you'll see just how well a 450 can auto.