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Old 05-02-2007, 09:02 PM   #1
AlanMcSwain
 
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Default Open Letter to Thunder Tiger, Align, Hirobo and others...

Subject: Large Electric Helicopter Safety Equipment Needed... Before Someone Gets Hurt.

I have been concerned lately by what I consider to be a potential safety hazard with the new generation of large electric helis. My own purchase of a Raptor E-550 has helped focus my thinking on this issue as I approach the set up and initial flight of this new helicopter. The revolutionary A123-M1 cell technology is also going to make these larger electric helis more popular because of the removal of the LiPo fire hazard and cost.

With nitro helis, on engine start, you typically hold the head with one hand while applying the starter with the other. The hand on the head is a safety practice. Should you have bumped the throttle stick on the Tx or made a recent programming or servo reverse error, when the engine lights, it will start to apply power to the drive system. Fortunately, the clutches we use don't have enough friction to overpower a good grip on the head tree during a "Hot Start". Many, Many potential injuiries have been avoided because of the presence of the centrifugal clutch in the helis and our practice of gripping the head tree.

Unfortunately, in the modern high power electric helis becomming popular, there is no equivalent safety procedure for dealing with a hot start. Yes, I do know that all modern ESCs have very positive, power application inhibition during power-up, but sadly, that is not enough of a safety margin considering the tremendous torque available to these drive systems. Consider a scenario where, while you were adjusting a battery strap on your T-600, some tool falls out of your pocket and happens to strike the throttle stick on the Tx where you laid it on the ground because you needed two hands to adjust the strap. OUCH!

The invisible assurances of the software running in these ESCs is simply not good enough. What is needed is a mechanical interlock between the Motor Pinion and the Main Drive Gear on these helis.

What I propose is that the motor mount design for future large electric helis include a cam-lock lever that when pulled thru approx. 180 degrees, the motor is backed away from the main gear far enough to disengage the gear mesh fully. The lever should also feature a ring on the end of it to facilitate the use of a "Kill Stick" so a running, but stable heli can be stopped when needed.

If this feature is incorporated in future designs, you would be able to power up the heli with complete confidence that no power will be applied to the drive system during initialization. You would be able to give the throttle a quick blip to check that the motor and pitch systems are operating suitably. Once these checks are done, you would simply move the motor cam lever forward, moving the pinion in drive contact with the main gear and step away from the heli.

There may be other ways to accomplish the same safety goal in other ways. I encourage you all to give this issue some thought and to contact your manufacturer reps and let them know that you expect this kind of a safety feature in thier future product offerings.

Alan
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Old 05-02-2007, 09:41 PM   #2
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Unfortunately Alan I don't see any more risk than if the same thing happened to a nitro, gasser or turbine...there is always the "what if" situations...throttle hold works the same in an electric as it does in a nitro...start up in throttle hold and you have one more safety precaution from something falling on the transmitter...

Sorry, I don't really see the need for the additional safety devices installed on the helicopter...a little bit of precaution and safety practices will go a long way in keeping accidents to a minimum...

Not bashing your idea...it is good to keep people thinking about safety...
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Old 05-02-2007, 10:51 PM   #3
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Lets toss these questions out to a wider audience...

How many of you feel completely confortable and safe when you plug in your battery to your esc on any size electric heli? I don't. And I'm an electronics and a software engineer. I know how this stuff works and I know it can't be 100% trusted.

The Deans connector we use takes two hands to connect. This means you can't hold the head, "just in case" while powering up the heli. Even if we could connect the battery with one hand and hold the head with the other, I'm not sure that would be enough on the larger heli's, especially the high voltage ones. Those outrunners produce alot of torque.

How many of you put the heli up on a car roof or hood while making that battery connection so you **can't** get wacked by the blades if something goes wrong?

Are you trying to anchor at least one side of the skids to the car roof while shoving those Deans together?

If you guys are using some procedure that I don't know about to make sure you don't get hit by an accidental blade spinup, I'd really like to know about it.

I have a healthy respect for the power of my nitro helis but I am not afraid of them because the head grip procedure works well and I've experienced a few hot starts and they are now fond memories that I am happy to say that I can count on **all** of my fingers.

Mistakes happen, equipment fails no matter how many precautions we take. That is the beauty of the nitro head grip precaution. No matter what happens, you have positive control of the heli.

You can't say the same thing with an electric heli. And I know that I really don't want to be in close proximity to a hot start electric heli possesing deadly force torque.
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Old 05-02-2007, 11:46 PM   #4
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I didn't with my little walkera dragonfly #4 even! I got hit once and from then on i bent my arm in a very uncomfortable way to plug in the bat without getting in the way of that blades.
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Old 05-03-2007, 02:58 AM   #5
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AlanMcSwain,

Take a look at what I setup for safety. True it doesn't disengage the pinion but I feel it's very safe. The good thing about this setup is you can adjust your radio and servos through your BEC without turning on the ESC!

Heli is in position
Turn on my radio
Plug in my Lipo pack
check throttle hold is on
Make sure gyro is set
Throttle stick is all the way down
Slide in the Allen key rod and turn it counter clockwise
Quickly get away while your ESC is turning on
Turn off throttle hold

READY TO FLY!!!!

It's as safe as anything I could think of. Works great!!!! Peace of mind. :glasses2:

The pics pretty much shows how easy and safe this setup is. The switch weighs about 1oz. http://www.teamwhyachi.com/

*EDIT Going from the MS-05 Switch to the MS-1 Switch. Keep in mind the MS-05 switch is rated way below what it can handle. It may not even be necessary to go to the MS-1 switch.... but better safe than sorry right. :wink:
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Old 05-03-2007, 03:33 AM   #6
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Lith...

Thanks for taking the time to post these pics. In my original post I said there were likely other ways to engineer this kind of interlock and your's is a prime example.

What Lith here has done is to create at least some safety distance between himself and the heli during ESC powerup and init. Lith's electrical interlock could also be improved upon by making the switch a slide interrupter that could be actuated by a clip release pull cord or finger stick of even greater length. A finger stick could also be used to pull the interrupter back into position to enable a safe approach in a stable runaway situation.

Way to go Lith!


Does anyone else have some kind of safety interlock setup on their e-helis?
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Old 05-03-2007, 03:57 AM   #7
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kevinator9...

I've been wacked by one of my mini-helis too and that's what really got me thinking about this.

And even if you put the heli up where you can get "under" it, you still need both hands to plug in the pack. I was even using the side of one of my hands to try to clamp a skid to the roof of my car, but I also realised at the time that this practice was not safe because if the heli started up, it would likely just pivot over at me because I could not clamp down both skids at once.
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Old 05-03-2007, 03:58 AM   #8
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Quote:
Originally Posted by AlanMcSwain
Lith...

Thanks for taking the time to post these pics. In my original post I said there were likely other ways to engineer this kind of interlock and your's is a prime example.

What Lith here has done is to create at least some safety distance between himself and the heli during ESC powerup and init. Lith's electrical interlock could also be improved upon by making the switch a slide interrupter that could be actuated by a clip release pull cord or finger stick of even greater length. A finger stick could also be used to pull the interrupter back into position to enable a safe approach in a stable runaway situation.

Way to go Lith!


Does anyone else have some kind of safety interlock setup on their e-helis?
Thanks man! I feel very comfortable using it.
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Old 05-03-2007, 05:28 AM   #9
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I have hot started a few nitros and my gasser. When I hot started my gasser luckily I had a death grip on it. I still wrapped the flybar around my arm

Conversely I have never had an issue with my Trex 450, 600, or my Ion-X. The Ion actually starts so slow (using a HV110 ESC) I have about 5 seconds where I would feel comfortable grabbing the blades and yanking the connection.

The other safety the ESC has over the nitro is they will not initialize if the throttle is not at 0%. Not to mention I do not have to start it get it warmed up, F with the throttle trim, then back it down. So my hands are not on the radio and the helicopter.

Now my e-startup procedure is:
- Radio on
- Check model
- Turn on BEC
- Check movements
- Throttle hold
- Plug-in battery(s)
- Step away
- Idle Up 1 or 2
- Turn off throttle hold
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Old 05-03-2007, 05:44 AM   #10
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Every thing needs a safety feature I suppose.... back up sensors on cars, bells at cross walks and early warning systems on cars to avoid accidents.... I think the best way to avoid an accident is to put down the cell phone, place both your hands on the wheel and actually drive your car.

On my e-flite Blade CP, the 4-1 wont go green if there is any throttle or trim at all. If you are really concerned you could go to your local auto parts store and buy a bit of thick vacume hose and wedge it against the stick to hold it in place.

Personally.... Before I plug in my heli I MAKE SURE the stick and trim are down.... Kinda like checking the water before you step into the tub.

Just my 2 cents.....
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Old 05-03-2007, 02:35 PM   #11
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Quote:
Originally Posted by AlanMcSwain
kevinator9...

I've been wacked by one of my mini-helis too and that's what really got me thinking about this.

And even if you put the heli up where you can get "under" it, you still need both hands to plug in the pack. I was even using the side of one of my hands to try to clamp a skid to the roof of my car, but I also realised at the time that this practice was not safe because if the heli started up, it would likely just pivot over at me because I could not clamp down both skids at once.
I did that also (but it was on the floor) and when I was going for the battery my face was quite near the blades! I got wolloped by them on the side of my head once (this was before I knew what they could do...)
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Old 05-03-2007, 04:21 PM   #12
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Quote:
Now my e-startup procedure is:
- Radio on
- Check model
- Turn on BEC
- Check movements
- Throttle hold
- Plug-in battery(s)
- Step away
- Idle Up 1 or 2
- Turn off throttle hold
DDog...

Powering up the radio rx first sure helps eliminate a confused ESC hot start. But when you plug in the drive battery, if the ESC did get confused on init and did apply power to the motor, even briefly, you would get whacked, right?

See, what I'm trying to establish here is that we should be able to be confident that ALL of the heli's electronics (microcontrollers, really) have powered up cleanly and safely and are operating as expected. Once that state of stability is established, the last step before stepping away would be to swing the motor pinion into contact with the main gear.

Alan
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Old 05-03-2007, 04:43 PM   #13
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Quote:
See, what I'm trying to establish here is that we should be able to be confident that ALL of the heli's electronics (microcontrollers, really) have powered up cleanly and safely and are operating as expected. Once that state of stability is established, the last step before stepping away would be to swing the motor pinion into contact with the main gear.

Why not put a simple on off switch in the positive lead going to the main motor instead of a complex swing away pinion? You could mount it any where you would like and after every thing is good to go, you flip it on and fly away... Simple and effective

but one more thing to remember when shutting down.... gotta turn it off or it will be on next time you start up... but then again you would have to disengage the pinion too... so either way...

I still say just be careful and use your brain and you should be ok.
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Old 05-03-2007, 04:53 PM   #14
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Quote:
See, what I'm trying to establish here is that we should be able to be confident that ALL of the heli's electronics (microcontrollers, really) have powered up cleanly and safely and are operating as expected. Once that state of stability is established, the last step before stepping away would be to swing the motor pinion into contact with the main gear.
The way I test this is quite simple, I slowly plug the battery pack in - this way if I hear the motor arm up - I can just release the plug and it will die before ramping up. What I am saying is that when I plug the flight pack in I just get the connectors touching first, listen for a half second for the conf beeps or for the motor and then press the plugs together. That way if something sounds wrong the plugs will disconnect as quickly as you can let them go.

The idea of a moveable pinion base is very complicated and will add a bunch of weight and mechanical issues to the helicopters. You would be hard pressed to find such a moving unit that locked in the EXACT location each time - causing mesh issues. It would also be difficult for this mechanism to be solid enough to stay engaged in the same exxact spot through all the loads of flight. I could honestly see such a mechanism that worked properly costing over $100 by itself. Maybe I am thinking too much on it, nerds tend to do that But I think it would be a very hard task to make something reliable and EXACT in that function without it costing a fortune.

I can say that all my setup is done with the pinion pulled away, I also emply the throttle hold switch on startup like mentioned before. The method of soft plugging I mentioned above has saved me on one occasion from my own stupidity- blades didnt even get a chance to move - so I know it works. Just another idea.
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Old 05-03-2007, 05:18 PM   #15
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I think that the easiest most fail safe way would be to have a lock pin so nothing can turn. Put a ring on the end with a long piece of string then pull it out from a safe distance just before you spool up.
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Old 05-03-2007, 05:36 PM   #16
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Quote:
Originally Posted by AlanMcSwain
DDog...

Powering up the radio rx first sure helps eliminate a confused ESC hot start. But when you plug in the drive battery, if the ESC did get confused on init and did apply power to the motor, even briefly, you would get whacked, right?
Not any more than I would get whacked with a nitro... It is not like there is a delay if you have a good hot start.

With an electric theoretically with a bad ESC (which I have never heard of) unless it started AND gained enough speed during a 1/4 rotation of the blades (and the blades did not fold) AND it was not enough to knock me down... I would still have the connection wires in my hand.

The Trex 450 starts REAL fast. A 90 sized swinging 710 blades just can't... Due to Inertia and Mass.

I think you are giving these things more credit than they deserve quite honestly. Kind of like the Lipoly "fire hazard". Yes, it is "true" but if you follow the rules the "reality" of it actually happening is... small to none.

My $0.02
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Old 05-03-2007, 06:35 PM   #17
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Found this over on the Mikado site. These folks have the most experience with this subject.

http://www.logoheli.com/tips.htm#Safety
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Old 05-03-2007, 07:13 PM   #18
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That site is kind of funny... look at the other side of the page

Asking your wife or other inexperienced person to take care of your Lipolys is just plain stupid. I would no sooner ask my girlfriend to take care of my charging batteries anymore than I would ask her to take care of my Nitrous Oxide system on my car. And she has a doctorate (she is a Dr.) Educated does not = Experience

Like I have said earlier on the "Lipolys are Dangerous" thread. I know of, and hear news from, ALL of team Flightpower... and I have NEVER have I heard of and ESC going bad and hot starting. We are taking thousands, if not tens of thousands, of flights. And even if it did... I am not exactly sure how it is any different from a glow or gas hot starting as it would be a lot of "no fun"
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Old 05-03-2007, 08:16 PM   #19
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Quote:
Originally Posted by DebianDog
The Trex 450 starts REAL fast. A 90 sized swinging 710 blades just can't... Due to Inertia and Mass.
I know I'm more scared of a small heli freaking out on me than my E-620!!! One day my Blade CP freaked out after plugging it in. The ESC had a fit and went full throttle when the throttle stick was all the way down. I was inside my hobby room and had to make a run for it. I looked around the door and it was bouncing off the ceiling! It hit my plank hanging up then hit the ground flopping around like a chicken.
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Old 05-03-2007, 09:03 PM   #20
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Quote:
I am not exactly sure how it is any different from a glow or gas hot starting as it would be a lot of "no fun"
I've had glow hot starts and they are startling, but that friction clutch just can't win over my instant death grip on the head. Why? Because my hand was already there, holding it.

There is no equivalent "when all else fails" safety procedure with electrics. You double check all your switches and sticks, you step up to the heli like a man, and you use BOTH hands to plug in the ESC to the battery while you and your arms and head are in close proximity to the unfurled blades. From that point forward **YOU ARE GAMBLING**.

You are trusting that code within the ESC that you did not write and have not, nor can not examine is going to execute flawlessly.

You are investing belief in the infallability of the engineers and programmers who designed that ESC, people whom you do not know, have never met and likely could never identify.

You are hugging a high tech teddy bear named Silicon Oxide, hoping that it's couple of micron thick insulating layer dividing the forces of positive and negative within the array of HexFets will continue, please continue, to hold.

Deny it if you like, but you have just joined the church of "But It Worked Just Fine Last Time".

Lith is the smart one here. He understands the potential danger and has taken steps to mitigate it. OK, it took one pissed off Blade CP to show him the light, but he still gets applause from me!!
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