Had a receiver blackout due to my receiver battery. Oops. Full throttle upside down for nearly 30 seconds. Still has great compression, cylinder wall looks fine, piston looks fine. Can't start because the one way for the pull start didn't enjoy the heat. Got to 350 degrees right as I shut it down. What am I looking for in a failed motor due to a runaway? It's an rtr motor that can be replaced for 60 bucks but runs consistent and I modified the sleeve, so she screamed. Would like to avoid a new motor right now.
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Runaway RC
- Thread starter aMawds
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smittyzz
RCTalk Talkaholic
Return spring helps a lot
Sixtysixdeuce
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Why did it take so long to get to it?
Well, catastrophic failures are obvious. Otherwise, the same signs you get when they're worn out; Hard starting, won't idle, won't hold a tune, flaming out.
- Thread starter
- #5
Opposite side of the track and I was in the driver stand. I then tried to kill it by plugging the exhaust with my shoe but at full bore it wasn't going to happen. Basically I was afraid to flip it on it's wheels for fear that it would fire off into the bushes. Ended up flipping it on it's wheels anyway and that let me kill it.
Good to hear that failure is fairly obvious. With good compression and no obvious signs of damage to the liner I hope I'm alright. I'll pull the pull start off and fix the non retracting problem then go from there.
I have a rubber band on the throttle but that isn't strong enough to pull the dead servo. Only to close the throttle if the linkage popped off. I'll order 3 more receiver batteries of the LIFe chemistry and keep an eye on voltages for now on. This is the second time this has happened, and the first time it almost ended catastrophically. First time it happened the throttle was hardly open past idle. The NIMH battery will only be a backup or test battery at this point. Very small traxxas hump pack and I don't trust it.
- Thread starter
- #6
Bullet dodged. Not only does she run, but she runs completely fine. Didn't get to drive it but started it up. Glow plug was fried. One way bearing was a lost cause as well, but I was able to drive the old one out of the metal housing and a one way from an electric 450 size heli is an exact fit. Go figure. With the JP-2 pipe just running on a test stand the motor revved much much better than with the junk stocker, sounded a bit healthier, and on the ground tried to pull from my hands harder. I'll run a tank through it tomorrow to give it a real test but I think I'm good. An order goes out for more RX batteries though. Not going through this again. I learned my lesson. Plus a runaway nitro is simply dangerous and reckless.
- Thread starter
- #7
An update, engine seems untunable. Just pulled the head button and bits of metal were fused to it and the piston top, and a tiny chunk taken out of the crown of the piston as well. Spending 30 bucks on a piston and cylinder for a 60 dollar rtr engine seems silly so the buggy is likely dead until I can afford a replacement. Oddly it still has compression, but I'm assuming the leak past that missing chunk isn't exactly a calibrated leak and is the reason why it only seems to run well on the low end, or full throttle, but never both at the same time. Either it doesn't idle and sputters on take off, or idles fine but doesn't run well full throttle. Luckily I have a truggy with an OS motor coming to keep my mind off the loss. Coming with a starter box too, so when I replace the buggy motor I won't be getting one with a pull start. That'll drop the price 10 bucks or so... Lol. A lesson learned. Another receiver battery is cheaper than even the cheapest motors, and easily pays for itself in the headaches alone. Again, glad I learned these lessons on cheap equipment so I don't toast a 200 dollar motor. The old motor will sit on my desk as a reminder.
hulkmaxx
Wanna know my secrect. I'm always ANGRY!
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At the least I would install a fail sake return spring. I have been luck only have had one runaway and it suck I ended up popping a brand new engine on a new rig! Lesson learned.
Snook Man
Hardcore RCTalk User
It’s never a good thing when "Full throttle upside down for nearly 30 seconds"
Regardless of engine manufacturer, there will always be some damage that occurred to a glow engine in that instance.
- Thread starter
- #11
Can someone give me some info on the return spring and failsafe? I have a small rubber band on the throttle so if the linkage pops off, it will close. I'm assuming what you guys are referring to is able to close against the depowered servo in the situation I was in, complete loss of electrical power on the vehicle. As for a failsafe, the transmitter I use has a built in failsafe and I have it set to jam the brakes on, however that only covers the transmitter shutting off or losing signal.
I definitely agree. This track is next to a road and if aimed just right a runaway buggy could possibly jump into traffic and cause some issues must bigger than a fried motor. I'm covering the battery side of things but I obviously have no solution for a servo letting out the smoke or the receiver simply quitting.
I definitely agree. This track is next to a road and if aimed just right a runaway buggy could possibly jump into traffic and cause some issues must bigger than a fried motor. I'm covering the battery side of things but I obviously have no solution for a servo letting out the smoke or the receiver simply quitting.
Snook Man
Hardcore RCTalk User
A throttle return spring is usually attached to the throttle arm so that in the event the (battery power fails/disconnects or receiver dies) fail safe can not do its job the spring can over power the servo and return the throttle valve to the idle gap.
It’s a little tricky to get the proper spring rate so as to not be working the servo too hard but still be strong enough to pull it when needed. A little tinkering with attachment points and different springs is all it takes to get it to work properly. A rubber band works for when the linkage ball end pops off the throttle arm but they are not usually strong enough to move a dead servo
It’s a little tricky to get the proper spring rate so as to not be working the servo too hard but still be strong enough to pull it when needed. A little tinkering with attachment points and different springs is all it takes to get it to work properly. A rubber band works for when the linkage ball end pops off the throttle arm but they are not usually strong enough to move a dead servo
- Thread starter
- #13
After posting that I did a bit of research and saw people were doing it with more than one hair band and doubling them up to get the right tension. I immediately went downstairs and got it just right with two bands, both doubled up. On both, I have one half of the double up looped around the mouth of the carb, the other half over the high speed adjustment. Adjusted my end point and the servo doesn't seem to care the bands are there, but if at full throttle I shut the receiver off, it closes right back up in under a second. I feel better now. I'm going to go buy more of those hair bands. They're black silicone. I'm sure I'll get looks at the store though x) My throttle servo is rated at 148oz so it seems to have plenty of pull. I'll set this up with the truggy as well when it comes, BEFORE I run it for the first time, and I'll be checking my dead receiver return before every run for now on. No more runaways, ever. Unless something ridiculous happens like a rock getting under the body and jamming the linkage up or something. Anything else I might be missing?
- Thread starter
- #15
How does a second fail safe solve a power outage due to a battery disconnecting or dying? I have the failsafe for the transmitter cutting out, and the rubber bands for the servo failing, linkage popping off, or power failure.
That only works is you have power available. If you completely lose power its useless. And he already has a low power/signal loss failsafe built into his radio like most newer radios do nowadays so that end of the problem is covered. Without a mechanical failsafe to return the throttle to a closed position you will have a runaway in the event of total power loss. Turn your receiver power off then fire up your engine and see what happens.
hotrodrob
not hotdogbob
Lost track of the thread, thought he had tx batterie issues and not a rx batterie issue, no one said to not use a spring return/mechanical failsafe, and we all know what can happen if one forgets to turn on the powersuply to the rx but thanx for the reminder bud
Nitro Nerd
Gone - bye bye.
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Throttle return springs have never worked on the run-aways I've had - to the point I don't use them anymore. RocketRdr...I got your back. ;-) I know what you are saying. Not everyone does so kudos for posting that detail.
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- Thread starter
- #20
Hotrod no problem. Hard to keep track of every thread if you're following a bunch of them. Nerd, hopefully I have better luck than you x) I've had three partial runaways where the servo stops responding for under a second, and two total runaways. First time around the throttle was just open past idle and I easily caught up to it and stopped it. Second time was what this post was about, full bore over a jump, flipped over, other side of the track literally screaming. Toast. I vow to never let it happen again. I don't know what I'd do if my hobby ended up ruining an innocent persons day, let alone month from taking out a knee cap or something. These are heavy and not toys.
