Fail safe carb spring

[corona007]

Recently I was reading some post on a fail safe spring and might have a solution, Since I'm in the beginning of my R90SE and would like to have this safety feature. I have access to a coiler (spring making machine) and going to go ahead and make up some prototypes for my oS91SZ-H. I'm going to start by making them by hand (with no power) heat treated and use appropriate non corrosive wire most likely a stainless steel wire. It will be a torsion spring utilizing the existing tooling hole that is present on the carb (rod) leaver and the other end will be a 90 degree bend fitting the carbs outside casting. In other word it will be wrapped around the carb rod. It will have just enough torsion to close the carb in case a crash and the servo link is detached and not enough to make a difference on the power source. It would be too much of a con if I make it strong enough to close with a servo and I can't imagine the extra drain it would put on a power source. Also I might be able to retro fit on a OS50-H, But I don't have one. The 2 motors look very similar but I would need some dimensions to confirm. If you think you might be interested in this project or have any suggestions, comments good or bad please post them. Hopefully I will be starting next week.

[TheBum]

I'd be interested except for the fact that your intent isn't the same as mine would be. My only encounter with losing throttle control was when electrical power went out. The tricky thing about a solution for that is it would have to provide enough pull to move the servo shaft but not so much that the servo would overheat in operation.

[forjer]

..My only encounter with losing throttle control was when electrical power went out...
Yup. Since there is virtually no load on the throttle servo, power loss to the servo or entire system failsafe would be the most beneficial. In fact a lot of us are using a push/pull throttle setup so if one link managed to fail, the other link would most likely not.

Setting up a spring with enough power to overdrive or backdrive the servo will require a stronger servo (as well as still being fast) as well as a battery system that can handle the extra load.

It's a good idea to tame a heli that's out of control, but I'm not sure that a light spring is the answer. If you still have control over the other servos you could just fly it till it runs out of gas, in most cases another 5 minutes.

PM the Chris guy from Bergen around here and ask him about the spring on their kits.

Maybe another route would be to set up another micro servo to its own miniature battery and have that circuit kick in when the Rx loses power commanding the servo to cutoff the engines fuel supply.

[piwko4]

How bout this...

http://www.hurricanemodels.co.uk/unitrader/shop/product/NITRO-FAILSAFE/170

[DavidH]

How bout this...

http://www.hurricanemodels.co.uk/unitrader/shop/product/NITRO-FAILSAFE/170

Most of the radios already have a fail safe feature like the one in the link.

David

[piwko4]

so y do i see so many nitros with the motor screaming when they crash...

[DavidH]

How bout this...

http://www.hurricanemodels.co.uk/unitrader/shop/product/NITRO-FAILSAFE/170

so y do i see so many nitros with the motor screaming when they crash...

If the throttle linkage pops off the throttle arm. It is possible for the motor to go wide open in a crash. But it doesn't really happen very often.

David

[Pinecone]

so y do i see so many nitros with the motor screaming when they crash...

Probably because the pilot went max ptich (and therefore throttle) as a last resort save.

And then when the crash and the blades come off, there is no load, so they SCREAM.

[PurpleLuv]

I have a Traxxas Revo rc truck and it has a pretty strong return spring on the throttle. It is strong enough to pull the servo to idle if the receiver battery fails. I've had is happen once and it worked but I've also burned up a throttle servo too (about 50 bucks). If the protection was only for pulling the throttle closed due to a missing link a very light spring would do the job. I had a planker radio system fail and I had just went full throttle just before the failure. I didn't have a failsafe receiver (I do now). The plane flew into the ground at about 40 mph. This scared me and made me backup and rethink alot. My 33% Yak has a throttle cut and ignition cut. Just something to think about.

[corona007]

It's done...