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External Fail Safes vs Electronic on/off switch?

External Fail Safes vs Electronic on/off switch?

Old 05-20-2013, 11:13 AM
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Default External Fail Safes vs Electronic on/off switch?

This is a re-post from a post I put on the Radio & Electronics forums. I was getting no luv there so I figured I'd come to my fellow Nitro heads. If this is wrong my apologies, I'm just really looking for some clarity on this topic.
So....
Saturday I had the unfortunate experience of watching a runaway. My buddy was out behind his house tuning his motor before we were heading out to the track, when bam.. there goes his buggy. Went at least a quarter mile straight down the street before hitting a square concrete curb. The RC8 took it pretty well considering. Now I, and him for that matter, run Throttle return springs. So now Im on the quest to find more security. I have read about the Robitronics in-line fail safes, and read some on the KO and Robitronocs electric on/off switches. I run LiFe receiver batts, so from what I've read the Robotronics is the way to go. My question is does the on/off switches offer the same, apply brakes, features of the fail safe? I run Nitro almost exclusively, so which is the better option, the On/off switches or just in-line fail safes. All help and info appreciated.
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Old 05-20-2013, 12:06 PM
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Nope. Just another part and another connector ready to fail and cause a runaway.

Most reliable setup I've seen yet:
-two rubber hair bands for carb return springs
-7955 servos
-Airtronics M11x
- Protek Lipo. (get rid of that darn LiFe pack)
-Deans plug for a switch, or battery bars for a switch.
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Old 05-20-2013, 01:31 PM
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Just to be clear, I personally have never had a runaway... knock on wood.. My buddy was running a proper TH return spring. This had to be a hit on the radio. It was about 30-40 ft away, he went to bring it back around and thats when he realized it was on its own. Now i will say that he WAS running on 75hz, but still there are no hair ties, rubber bands, or THR springs that are going to anything to help in the loss of radio signal. After seeing that happen, really was sad to watch, it made me reflect. I sure don't want to see my $$$$ buggy do that, hell not even the XXL for that matter. So I pose the question. Are these devices really that worthless, that i should get rid of my dx3r and LiFe packs and buy a new $300+ radio and new LiPo's? Seems logical to me they would have their place, but then again thats why I'm asking the question here.
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Old 05-20-2013, 01:44 PM
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Default Spektrum

The spektrum receivers have a built in failsafe. You have to bind them with the position you want on the radio. So hold the brakes while binding. When your all set up turn your car on without it running and turn the radio off to see if it puts on the brakes. You should also run a coreless servo on your throttle that will be easily pulled shut when you unplug the battery to test.I have just had a few runaways because I didn't set the failsafe on my spektrum receivers. But I have them fixed now. If your friend is running 75 mhz stuff you do need a seperate failsafe.
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Old 05-20-2013, 01:55 PM
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Yea i have the built in TX/RX fail safe set. All my gear is sorted, as far as radio, servos, batts, and what-knots. I'm here looking for that little extra insurance. If it just not needed, what I've always thought and the reason I know so little about the devices, then its really not a pill i have to swallow. However, if it is good cheap added insurance then i would surly get one.
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Old 05-20-2013, 07:33 PM
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Originally Posted by Starksky View Post
Just to be clear, I personally have never had a runaway... knock on wood.. My buddy was running a proper TH return spring. This had to be a hit on the radio. It was about 30-40 ft away, he went to bring it back around and thats when he realized it was on its own. Now i will say that he WAS running on 75hz, but still there are no hair ties, rubber bands, or THR springs that are going to anything to help in the loss of radio signal. After seeing that happen, really was sad to watch, it made me reflect. I sure don't want to see my $$$$ buggy do that, hell not even the XXL for that matter. So I pose the question. Are these devices really that worthless, that i should get rid of my dx3r and LiFe packs and buy a new $300+ radio and new LiPo's? Seems logical to me they would have their place, but then again thats why I'm asking the question here.
Get some decent HV servos and you're all set. Hitec 7955's are obviously my choice.

LiFe packs are way more fragile than Lipos, that's your current weak link. Then you have your switch. Get rid of that and you're golden. 99% of running away poroblems are fixed at that point.
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Old 05-21-2013, 01:04 AM
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Good quality servos that have low friction when they lose power( so return spring
Or hair band will work) NiMh or LiPo pack and get rid of that switch, use a mini
Deans plug. 95% of your problems solved. Very rare for a good quality servo to
stick in a full lock position unless you power down the radio and the fail safe pulls
it to one sidr and cooks the motor, but thats another subject.
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Old 05-21-2013, 01:48 AM
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Originally Posted by Zerodefect View Post
LiFe packs are way more fragile than Lipos, that's your current weak link.


What makes you say they are fragile? Moreso to the point why running a LiFE pack would be a cause of a runaway?
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Old 05-21-2013, 02:47 AM
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Any electronic safety will be nothing when the power suddenly cuts off so a kind of a return spring is extra needed to make it complete.

Forget on/off switches but not the electronic ones (KO has one), If you still want to use a switch then use a dustcover which are available.

When using LiPo batteries be sure the servo's are rated for the use of LiPo voltages. If not it will work but for how long....

When using switching voltage regulators be sure they are rated enough (3A can be to low) and be sure their switching frequency does not interfear with the receiver. For sure it is not wise to mount it near the receiver.

When using LiPo or LiFe be sure it has a balancer cable. Balanced charging does give a better charging and with that a longer life to the battery. When charging just use 1 or 1.5C max charging current.

Also Lithium based batteries like to be storaged with a half charge. When raced the battery will be half charged so do not charge it until the next time of driving.

In case of a transponder, do not mount it near the receiver or on a servo. A transponder is also a transmitter and its signal can interfear the electronics nearby.
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Old 05-21-2013, 06:01 AM
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Originally Posted by wombat View Post


What makes you say they are fragile? Moreso to the point why running a LiFE pack would be a cause of a runaway?
Experience. They can fail so bad that your Rx voltage can brown out low enough to lose control of the throttle servo. Lipo's have been far more durable for us up here.

I've also considered direct powering my servos because a Hitec servo also has a failsafe built into the servo that you can program. Thus if the Rx fails completely, the throttle servo can throttle back all by itself when it senses no signal.

But, I haven't trid that in my "little cars" yet. Just my 5ive.
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Old 05-21-2013, 09:22 PM
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will carb return spring reduce the life of the servo?
it is after all "pulling" the servo at whichever position the throttle servo is in?
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Old 05-21-2013, 11:04 PM
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Originally Posted by wyl03 View Post
will carb return spring reduce the life of the servo?
it is after all "pulling" the servo at whichever position the throttle servo is in?
Higher quality servos require much less spring tension to return them to netural.
I have seen cheap servos that require so much spring tension to
return them to netural that the spring overwhelmed the servo. Generally
speaking the higher quality the servo the less of a problem this would be.
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Old 05-21-2013, 11:38 PM
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Throttle return springs of any kind will do nothing to help you in the event of a radio or other electronic failure. The servo is obviously strong enough to overcome the spring each time you pull the throttle. What they will do is return the carb to idle in the event your throttle linkage fails or comes apart.
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Old 05-22-2013, 02:08 AM
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I run an M11X with the built in failsafe and I run a throttle return spring. Some people here in Italy laughed at me for the spring. I was at the track yesterday and my linkage screw stripped out. The car just stopped and idled because of the spring. I would have lost a brand new NovaRossi BTTS without it.

I have never once had the electronic failsafe trigger. The signal quality on the M11X is second to none, but it can't make up for mechanical failure which is much more likely to happen.
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Old 05-22-2013, 02:39 AM
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Originally Posted by mkorn View Post
Throttle return springs of any kind will do nothing to help you in the event of a radio or other electronic failure. The servo is obviously strong enough to overcome the spring each time you pull the throttle. What they will do is return the carb to idle in the event your throttle linkage fails or comes apart.
Really... so when you lose power because of a bad battery, switch or connector
problem(90%of all radio problems) a throttle band or return spring that will return
the servo to center will do nothing um yeah ok
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