What NOT to do with your throttle

[KevinPJF]

Hi all,

I was having issues with my 450X (long story, but I think detail is important). I crashed it, ordered parts, reassembled it, and took it out for a test. Turned out the pitch was inverted (up, negative pitch, down, positive pitch). I had just completed a lot of work, to include going back through the BX, so I started reading about what it could be.

I found a point where it said something about, if your pitch is reversed, then reverse the channel. In my naivete, I reversed the throttle. With the helicopter powered up on my kitchen bar. As SOON as I confirmed in the Tx I wanted to reverse it, I heard it start spooling up. I grabbed the skids to keep it somewhat under control, but I couldn't disconnect the battery one-handed, so I hit TH. It didn't respond. So I dropped the throttle. Now the bird is pushing down toward me. I'm wondering what the heck I'm going to do. If the gear were to have given way, I would have been injured.

Well, the tail slid off the bar, it turned sideways, and the main hit the bar, which reduced the main gear's gearing to confetti. Now the motor is spinning furiously, but the rotor isn't, so I unplugged the battery. I was lucky to get out of it without at least stitches.

Please learn from my mistake. TAKE YOUR BLADES OFF before working on it, at least. ALWAYS ask yourself are you sure before making major changes like reversing the throttle.

Thanks for reading!

[leadmonster]

Wow. Glad you didn't get hurt .

[trex-]

This makes me to think about the protective clothing like motor cyclist wear. At least a shield ready beside you for prop attacks when heli goes out of control.

[acrow]

Thanks for the warning.

Most likely issue was that both blade grips were spun 180 degrees before you mounted the blades but good warning.

Another thing worth thinking about is the fail safe settings you have for your throttle. It is best checked by connecting a servo to your throttle channel so there is no danger of motor spinning. Then check that it goes to fully off when you turn off your transmitter.

One of the local clubs makes you demonstrate that your fail safes work. You would be surprised the number of people who thought their fail safes were safe but discover they're not.

Regards

Acrow

[KevinPJF]

That's exactly what the problem was.

[trel]

I learned early on ( the hard way) to remove the main blades AND disconnect 1 or 2 of the motor leads before working on your heli. The servos still work but no spool up of the motor. A small cut on the arm from the tail blades convinced me of that.

[atkin]

If I remember correctly, the motor can fire up (in a strange way) with just one of the 3 wires removed. I think it spins slowly though.

Blades off = Goood!

Originally Posted by trel

I learned early on ( the hard way) to remove the main blades AND disconnect 1 or 2 of the motor leads before working on your heli. The servos still work but no spool up of the motor. A small cut on the arm from the tail blades convinced me of that.

[Kap'n Krunch]

[QUOTE=KevinPJF;6440356]Hi all,

I was having issues with my 450X (long story, but I think detail is important). I crashed it, ordered parts, reassembled it, and took it out for a test. Turned out the pitch was inverted (up, negative pitch, down, positive pitch). I had just completed a lot of work, to include going back through the BX, so I started reading about what it could be.

I found a point where it said something about, if your pitch is reversed, then reverse the channel. In my naivete, I reversed the throttle. With the helicopter powered up on my kitchen bar. As SOON as I confirmed in the Tx I wanted to reverse it, I heard it start spooling up. I grabbed the skids to keep it somewhat under control, but I couldn't disconnect the battery one-handed, so I hit TH. It didn't respond. So I dropped the throttle. Now the bird is pushing down toward me. I'm wondering what the heck I'm going to do. If the gear were to have given way, I would have been injured.

Well, the tail slid off the bar, it turned sideways, and the main hit the bar, which reduced the main gear's gearing to confetti. Now the motor is spinning furiously, but the rotor isn't, so I unplugged the battery. I was lucky to get out of it without at least stitches.

Please learn from my mistake. TAKE YOUR BLADES OFF before working on it, at least. ALWAYS ask yourself are you sure before making major changes like reversing the throttle.

Thanks for reading![/QUOTE

when you hear that infamous sound grab the head and hold on to it for dear life. don't let it go let the motor smoke esc smoke or rip the wires out what ever you can do your
lucky it wasn't a 700

[KevinPJF]

Originally Posted by Kap'n Krunch

when you hear that infamous sound grab the head and hold on to it for dear life. don't let it go let the motor smoke esc smoke or rip the wires out what ever you can do your lucky it wasn't a 700

I was telling the story at the LHS and mentioned I was glad it wasn't a 700. But luck has nothing to do with that aspect. A li'l girl I've been married to for almost 30 years, who's named after a spice, has WAY more to do with it not being a 700 than luck.

Seriously though, it makes me glad I am taking it slow in the hobby (nano to a FP 200, to a CP 100, then 450, etc). While there is nothing inherently wrong with starting with a big bird, experiences like this can end much differently, as you pointed out.

[Skidpad]

Yes, glad you aren't seriously hurt. This thread is also an example of testing your failsafe early on in the setup process; correctly set, one could turn the radio off and have failsafe take over, thus avoiding trying to wrestle a spooling heli.

Yes, failsafe typically does take about two or three seconds to kick in, but at least it's safe from at least one standpoint.

[flyingquisinart]

My guess is this is probably the most common injury or near injury accident with helis. I've done it, setting up an ESC on a 550. It was only a spin up to maybe 20% but tore the skin off my knuckle and scared the hell out of me. Lesson learned on that one.

[Crowbar]

I heard that same story from a couple people at the field. They always point out how the transmitter asked them whether they really wanna invert the throttle channel.

Maybe Tx suppliers may wanna implement a safety timeout. You know when you change display resolution or orientation on your computer and it reverts back to the previous setting if you don't confirm?
For the heli (or a plank for that matter), that would just move the motor for a second if you mess up, usually not enough to get airborne.

Also: always take main and tail blades off when messing with that stuff.

[19trax95]

this is why i hold the head on my 700 nitro machine with a firm grip every time i start it. I only had to witness one hot start on a 90 size machine (that's something youll never forget, a 90 size motor doing its hardest to rip out of your hands until the clutch fries or the main gear strips out) to hold on until im sure its not going to start to spool up. This has transferred down to my little 180 cfx even. I put my hand across the had and then connect the battery with throttle hold on. Just force of habit now.

[Mattinfla]

Originally Posted by 19trax95

this is why i hold the head on my 700 nitro machine with a firm grip every time i start it. I only had to witness one hot start on a 90 size machine (that's something youll never forget, a 90 size motor doing its hardest to rip out of your hands until the clutch fries or the main gear strips out) to hold on until im sure its not going to start to spool up. This has transferred down to my little 180 cfx even. I put my hand across the had and then connect the battery with throttle hold on. Just force of habit now.

That works for a nitro or gas with a clutch. But a big electric would be a different story. Unlike internal combustion engines, electric motors have full torque at 0 rpm, and will increase torque until it either burns up something in the power train, or breaks loose....

[blade450]

Originally Posted by Mattinfla

That works for a nitro or gas with a clutch. But a big electric would be a different story. Unlike internal combustion engines, electric motors have full torque at 0 rpm, and will increase torque until it either burns up something in the power train, or breaks loose....

Some ESC's detect that they are being stopped. YGE will give a startup failure. My Kosmik has stopped because it was blocked once too.

Not every ESC does this of course, but some are actually able to detect something is going wrong and will stop if stopped long enough.

[distructor]

Glad there was no damage to you
I did something similar. After setting up a new heli, just before I went flying, I figured I needed to check the failsafe by turning off the TX. As the rotor started up. I had to pin it against the wall in our entryway. No damage, but sure taught me a lesson as well.

[mmickels]

Originally Posted by acrow

Thanks for the warning.

Most likely issue was that both blade grips were spun 180 degrees before you mounted the blades but good warning.

Another thing worth thinking about is the fail safe settings you have for your throttle. It is best checked by connecting a servo to your throttle channel so there is no danger of motor spinning. Then check that it goes to fully off when you turn off your transmitter.

One of the local clubs makes you demonstrate that your fail safes work. You would be surprised the number of people who thought their fail safes were safe but discover they're not.

Regards

Acrow

I test the fail safes on all my birds. Also, unplug the motor wires when you are working on the model. It only takes a second and can save you from an injury.

[jbrandt]

Something else that's important, that I'm sure you know now, but is important to point out:

All things equal, your transmitter settings should NOT change after replacing parts!

This isn't necessarily true if you are upgrading parts, but if you're just replacing broken stuff after a crash, you should have to mess with your TX settings.

So if you have to reverse something to get it working "right" after a rebuild, STOP and double check the mechanical setup.

And of course, always unplug one of the motor wires before your first bench test.

[AntDX316]

There should never be an option to reverse the throttle switch w/o going through at least 1 layer of confirmation. Like are you sure? are you sure again? then OK.