Nitro failsafe

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mzanzirc

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Apologies is this was already covered. I did a search, but my ninja skills probably failed me.

So as I have my nitro running, the TX and RX has it's own built in failsafe.
Nice, but it's only there when you lose comms when your TX loses power or the car is driven out of range.

If your receiver battery should die, the failsafe between the TX and RX will do diddly squat if the receiver does not have power to close the throttle servo.

So I'm guessing you have to have a two stage failsafe for nitro. But what?

Throttle return spring?

Something like this:

https://www.ebay.com/itm/3336517761...sag6kAYLz+ideMFj1XHHImSUnxkI|tkp:BFBMppOI_ZZg

But how does it work? I can see it plugs in between the servo and the receiver, but does it have it's own battery in to be powered independently from the onboard car battery?

I'm intrigued.
 

WoodiE

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@mzanzirc the failsafe built into your radio would cover you on the electronics side. For complete battery failure or otherwise, I would use either some rubber bands or a return spring on your carburetor.
 

mzanzirc

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Throttle return spring, that's all you ever need, and that's all that's reliable.
I have seen those. Thanks.

BUT....will a TRS not cause the servo to die prematurely?

I mean, the spring needs to be stronger than the servo to pull the carb closed in the event of a hump pack failure or battery ejection, so would that not add additional stress on the servo and make it die sooner? I read on some forums people don't like the TRS as it's ineffective if its not strong enough.

@mzanzirc the failsafe built into your radio would cover you on the electronics side. For complete battery failure or otherwise, I would use either some rubber bands or a return spring on your carburetor.
Yeah thanks. Hence my 2 stage comment. :)

Failsafe for the TX and RX, then a secondary failsafe for getting the carb closed if the on board battery is kaput. :p
 

johnnydmd

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BUT....will a TRS not cause the servo to die prematurely?

I mean, the spring needs to be stronger than the servo to pull the carb closed in the event of a hump pack failure or battery ejection, so would that not add additional stress on the servo and make it die sooner? I read on some forums people don't like the TRS as it's ineffective if its not strong enough.

It doesn't need to be stronger than the servo. When the servo loses power, it offers little resistance. Same when it loses radio connection. Actual springs made for this aren't that strong actually. It shouldn't affect the life of a servo.
 

mzanzirc

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It doesn't need to be stronger than the servo. When the servo loses power, it offers little resistance. Same when it loses radio connection. Actual springs made for this aren't that strong actually. It shouldn't affect the life of a servo.
Interesting thx.

I will see if I can find some springs and play around with them.

Would really like to get a failsafe in place. Even though I've velcro strapped my battery in the car, one never knows. :D
 

cbaker65

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Interesting thx.

I will see if I can find some springs and play around with them.

Would really like to get a failsafe in place. Even though I've velcro strapped my battery in the car, one never knows. :D

Also ,not having any type of spring on the carb causes engines to idle high when off the throttle!
Most Track racers use rubber bands ,an dont run a switch ,they plug their receiver battery direct
into the receiver!..:thumbs-up::cool:
 

mzanzirc

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Right.

So what is the accepted method for the TX/RX failsafe on a nitro?

Full brakes or neutral?

Neutral

I'm leaning towards neutral. Purely because the car will just coast to a stop. BUT, I guess if I'm WOT and 10m from a obstacle, it might still coast into the wall at a decent pace. Probably highly unlikely, but who knows.

Full brakes

I also like full brakes as the car will stop immediately and not coast and still be able to hit something. Only con I can think of, if I turn off my transmitter and it goes to full brakes (failsafes) and forget to turn the car off, the servo might get damaged trying to keep the full brake on.


What do you guys have yours set at?
 

gandalfnz

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Check out how I did mine...
 

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Hojaz

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It doesn't need to be stronger than the servo. When the servo loses power, it offers little resistance. Same when it loses radio connection. Actual springs made for this aren't that strong actually. It shouldn't affect the life of a servo.
This is interesting.
My servo is really hard to move by hand when reciever is turned off.
I have to put ALLOT of rubberbands on just to make it move a little towards closed pos, and if i do, the carb wont open fully without maxing out the throttle Epa.
I'm guessing some servos are easier to move than others??
 

olds97_lss

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TRS covers you for battery falling out or going dead.
FS in the receiver covers you for loss of signal.

I set my FS to go wheels straight and throttle at idle. Then if it cuts out when in flight or something, it doesn't lock the brakes and endo like an idiot.

Some old fail safes would sense the voltage of the battery and kick in when it got below 4.2V or something like that as well as loss of signal. But that won't help you if your switch dies or battery comes unplugged.

Traxxas uses a stupidly stout TRS on the revo with the stock setup. It puts load on the carb/linkage and servo all the time. I never cared for it and would make my own wire, use collars/springs on the wire so there would be a little tension on the servo when at idle pressing the carb closed, but the only "spring" it was fighting was a more normal TRS spring I'd use by someone else that was connected to the throttle pivot.

My small block revo with the motor down low in the stock mount:
2019-0815-Revo21TM-Top.jpg


My big block revo has the motor up high, so I have the TRS connected to a roll bar:
2019-0120-RevoBB-ThrottleLinkage.jpg


On my old savage X, it was more normal, one end of a spring connected to the HSN housing, the spring went around the front of the carb neck and connected to the throttle ball end thing, you can kind of see it here:
2019-0614-SavageX-Linkage.jpg
 
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