cotton_eye_joe92

Hey everyone.

I've had two run-aways with my stock controller and stock servos in my Talon. The first one is the one that made it so dirty, just yesterday, I tested the servos before running it, and everything looked fine.

I took it on a highspeed run going full throttle, once again, it flew down through the ditch, over the icy water (thank god) and it ran away in the field. This time I chased it on foot for I'm guessing 5 minutes. I was out of breath when I got to ti. I picked it up (it was upside down) and turned it over. The engine was smoking, too.

Cursing, I took it back to the house. All the servos seemed to be working fine.

I'm thinking that my pullstart handle is getting in the way for the throttle servo.

Would it be a good idea to make my own mechanical 'failsafe' system with a spring through the throttle servo's horn leading to somewhere in front so that when I would let off the throttle, it'd go back to it's idle position?

Also, would it be worth buying a new radio and new servos?
I was going to get a failsafe at my hobby shop in Defiance, but they wanted like $30 for one, and I thought I was alright without one.

Thanks!
-Joe

SManMTB

Just use small rubberbands around the carb throat to the ball link and you're good to go.
Just like this:

[link=http://www.kyoshoamerica.com/techtips/throttle.asp]Click me![/link]

fugadude

Get rid of the pullstart and put in a rotostart? I hate pullstarts!

dustin7837

My Feedback: (1)

Get an electronic failsafe!!!!!
30$ is cheap insurance!
You should also add a throttle return spring or band like smanMTB says.
the talon has a rotary carb though, so setting it up will be different than the pictures in that link ^

cotton_eye_joe92

Yeah, but wouldn't a mechanical failsafe work and save the car no matter what? If the radio went bad, then the rubber band would move the servo back to the idle position no matter what, and if the pullstart handle got in the way, the rubber band would still move it back to the idle position, wouldn't it? No matter what went wrong, it'd still save it, right? Yeah, I probably will get a failsafe next time I go to Defiance.

By the way, this buggy is looking pretty tough. Two runaways in two days. The only thing I did was cracked a little bit of a rim for a tire, but I think I'll be ok for a while. The thing flew through a deep ditch catching air then cartwheeling a bunch and flipping, just wish the radio equipment was that good.

Anyone have tips on how I would mount the rubber band thing since this engine has a rotary carb?

Thanks!
-Joe

DaveG55

NO, a throttle return spring will NOT save you in any circumstance.
Actually a TRS will only help in a very limited set of circumstances. The only time a TRS will help is when you have a mechanical failure or a complete loss of power to the radio/servos, like if the batteries become disconnected. Otherwise the servos will have the power to overcome the TRS. If your loss of control comes from low batteries or signal interference a TRS is of no help at all because the radio is still giving a signal to the servos. Also, I don't think a TRS will help if the linkage/servo is catching on the PS handle. If the handle is in the way, a spring will not get it out of the way. Really it seems like it would just make it bind up harder.

On the spring itself, use a spring, not a rubber band. First because rubber will deteriorate when in contact with nitro fuel and second, because a spring will be easier to mount on a rotary carb. Mount it so that the spring pulls the throttle closed with the radio off but not too tight. Remembr,any extra pull the servo has to fight will decrease the servo response time and use battery power much faster.

Your best bet is to use both a TRS and a failsafe. Fails safes by Duratrax and OFNA usually run about $20, are easy to install and set up. They will also protect you fom low batteries and signal interference.

One last thing, If the PS handle is causing these problems you should probably address that too. Maybe by hooking it behind something out of the way or b y putting a bit of fuel line on the pull rope to get the handle out of the way.

cotton_eye_joe92

^Oh ok I get it now, sorry if I sounded dumb, I'm still kind of new with these things. Just got the buggy in late August.

I'm thinking of getting some metal wire or something to hold the handle up and away from the servos just a bit.

Thanks for helping me learn something new today

-Joe

silent_echo

Dave, you ahve a point iwth what you said about the mechanical failsafe. thats why for the most safety i recommend an electrical failsafe, AND a TRS this way if you go out of range or lose signal the failsafe kicks in, if your battery becomes disconnected somehow then the TRS puts the car at idle

SManMTB

I just want to comment on the text in green.
A TRS will save you in most cases actually. I've ran the rubberband solution for quite a while now and it works perfectly.

Low battery - with a low battery the servo doesn't have the power to move very fast (if at all) which means the throttle won't and can't stick at WOT. No risk of runways.

Loss of signal - If I turn off the transmitter the receiver is not getting a signal and will not send a position signal to the servos. Consequently the servos will not have a signal for position reference and therefore they have no torque. The throttle will be closed by the rubber band. Try it and you'll see.

Final comment. It's try that a rubber band made out of rubber will break and deteriorate like you wrote. The bands in the link (the same I'm using) are made from silicone and will not deteriorate.
With a rubberband you can also easily control the stiffness by adding or removing bands. I use 5 or 6 of them.
It is true that the servo uses more power with higher load but compared to what a steering servo uses this is a moot point really.

DaveG55

Well, I'm glad it's working for you.
Problem for me is when my batteries start to get low my radios and servos start getting a life of their own. Twitching, going wot, lots of odd behavior. A trs (or rubber bands) is no help at all for that. Neither are they any help for radio interference, which is what I should have said in place of loss of signal.
You can keep using just your rubber bands, and more power to you. Me, I'm going to keep running both on every nitro powered vehicle I own.

SAVAGEJIM

Dave has a point. Many of us upgrade our servos and these servos have, among other improvements, more torque. Some use throttle/steering servos that put out as much as 150oz-in (a little excessive in my opinion). When such a servo starts twitching and acting up when the recever batt is low or fails, the springs/rubberbands usually will not be strong enough to keep the servo from going W.O.T. or whatever.

Now, if the servo ceases simply to work when the recerver batt goes dead or fails, that would be ideal. Of course, the failsafe will also instantly go dead and will not do what it is programmed to do. The only way to prevent this is to make sure the receiver batt is never near dead and is in good working order. That way, the failsafe can do what it needs to do when something goes wrong.

SManMTB

Well, whatever floats your boat.
There's a reason sanctioned racing requires a TRS and not a EFS.

dustin7837

My Feedback: (1)

basically, the way I understand it, a properly setup TRS will save you from anything EXCEPT radio interference. At a race where channels are controled, not a problem. Local park where theres a chance of someone else having your channel, or even high voltage line... you may have an issue. Thats where the EFS comes in.

For less than 30$ and less than a half ounce. I think its worth having both. Then your always covered.