Ronaldcorb

My son has an RC10GT RTR that has developed a strange problem. After running for about 3/4 of a tank the truck will sudenly go to full throtle and he is not able to activate the brake. This has so far resulted in 2 crashes, one of which gave us a leson in how to change a rear shock strut.

I checked the car before we ran it yesterday and had full brake action when we started. The only things I noticed were that the idle is set a little high(we have to hold brake on to stop the car at ide) and the engine is still set a little rich (I think).

We are still running the car without the body to provide max cooling to the engine while it is still new. The truck has had a little less than 1/2 gallon of fuel run through it. (Trinity Power Blend 20% Nitro)

As the tank ran dry yesterday it went into speed-up mode and crashed (was a cool flip though) into the yard next door. We had only run about 3/4 of a tank through it on a quick test after repairing the shock strut.

When I picked up the truck the metal chassis was to hot to hold in my hand. Not just the side by the exaust but the whole thing. I work with my hands and can hold things when thay are pritty warm but this was downright HOT.

What I think is happening is that the receiver is overheating and malfuncining causeing the "run-away condition

Now to the questin: Is it suposed to be that hot and if not why would it be?

Other things that may be impotant: The Air temp at the time was about 103 (we do live in Vegas) and we were running it on the paved street. (yeah it is hard on the tires, but don't have track near here yet and don't know what tires to use for street.) Also this truck is just how it came out of the box. No upgrades ot changes (except fot the new shock strut )

Thanks for putting up with such a long post

Ronaldcorb

FlyinRazorback

My Feedback: (8)

I'm not an engine guru by amy means but it sounds like you are running too lean. As the engine heats up during a run, it leans itself out. A good indicator that it is running to lean is by not being able to touch the engine after running it for some time.

vegas mossie

does the truck have a kill switch? ( to prevent run aways) also, it is not uncommon for a engine that is running rich to speed up as it runs out of fuel. check the tank to make sure the lines are free and not hung up. as for the heat, you might try less nitro in your fuel during the summer. ( i do this with my planes) where do you live at? i'm up by sunrise mt. my sons and i run our stadium truck behind sunrise in the desert . lots of room to let the trucks fly!!! plus there is a LHS close to pick up the parts we need! good luck loren

Ronaldcorb

I am not sure that you understand what I am saying. I am talking about the CHASSIS being to hot to handle. I expect the engine to be hot but this is the area under the fuel tank and receiver.

I will re-check the mixture and try richening it a little.


How does the kill switch operate? Any info on how to do this will help.

I expect the engine to speed up as it runs out of fuel BUT should't we still have throtle /brake control?

The fuel is what was recomended by the LHS on Boulder Hwy. We are near the 215 and Eastern.

Thanks for the help

Ronaldcorb

FlyinRazorback

My Feedback: (8)

Is the engine not to hot to touch also. Heat is dissapted through the engine mounts and to the chassis.

Elwood

My Feedback: (2)

I would get a throttle return spring. Losi sells a kit that should work out great. $3.00. Run it on my GT after a runaway...

I would do the spit test. Gross, but it works. Dab a little on the head. If it just sits there- too cool. If it cooks off, should be OK. If it sizzles like bacon on a hot pan, then it is too hot.

Also, you might try a lower nitro fuel due to the heat.

vegas mossie

with our temp. extremes, i would try less nitro first. if your esc is over heating, it could cause all sorts of problems. the engine is cabable of heating up the chassis and our heat just magnifies the problem. have you run it at night? maybe try a tank full at night, then the lower nitro. also check the batteries for the esc and radio. keep us posted how it goes Loren

FlyinRazorback

My Feedback: (8)

ESC with nitro?

vegas mossie

esc, reciever what the he** do i know??? i need to have my head reattached...

Ronaldcorb

ESC= Extra Special Contraption Also called a Receiver and/or Servo

Last time we did the "Spit" test on the engine it was OK. I guess that the thing that concerns me most is that when the truck speed up, we had NO brakeing action even though full brake was applied. Being in electronics this indicates a thermal runaway condition in the receiver. What tempature should the receiver be able to handle? Maybe we need to check the receiver internaly for bad conections etc.

Has anyone had this problem before? Is this a common problem?

As for lower Nitro, what % would you recomend?

Ronaldcorb

While discussing this thread with my son I had a sudden revilation.

His radio system is AM. We also discovered that he is missing a few screws from his truck. What may be happening is that something is loose and the metal to metal contact that occers as the engine/truck heats up will generate interferance. This could be causeing him to "shoot down " himself (as the saying goes in airplanes. Don't know the RC car term).

I think that the plan of attack will be to re-check all screws and replace as needed. Then we will try to find a tempature gun to double check the engine temp. Then we will adjust the Nitro content if required.


Comments?

Ronaldcorb

FlyinRazorback

My Feedback: (8)

After each day of running and bashing it is good practice to clean the truck off good and check for and tighten loose screws. It also doesn't hurt to check periodically throughout the day.

"when the truck speed up, we had NO brakeing action even though full brake was applied."

Does it idle real high? If so, try turning down the throttle / idle knob a bit. Also, the brake wears out fairly quickly under heavy use and may need to be replaced. As for heat interference with Rx, I guess it's possible but I don't know.

"ESC= Extra Special Contraption Also called a Receiver and/or Servo"
Is this a western thing? As far as I know, esc's, receivers, and servos all perform a different function. Are there any servos or ESC's I don't know about that are capable of receiving radio transmissions?

vegas mossie

No it is not a western thing, it was just me getting the esc and reciever mixed up (electric and gas) I believe I am begining to suffer from rc overload. ( fly two paper airplanes and call the dr. in the morning) LOL Loren

po'boy

im new to rc cars but have flown rc planes 24 years now and the first thing i would check is with the fuel tank . if it runs fine for 1/2 to 3/4 of a tank then speeds up what i think is happening is it will start sucking up air with the fuel causing the engine to turn lean and also get hot

Ronaldcorb

Thank-you
That is one point that we had not considered.

One more thing to look at. With all these ideas I am sure that we will get this thing licked soon.

Ronaldcorb

dbow

My Feedback: (1)

In my opinion this is not a fuel or carb problem or even a heat problem. If the engine runs off like that its of course going to be hot and transfer heat to the chassis.


I think Ronaldcorb hit it right on the nose about something being loose on the truck. I think that it could be a glitching problem and the 3/4 tank is just a coincidence. If it were something other than the radio then the operator would still have control and braking.

I would take a gander at the exhaust pipe and check all the metal to metal parts.
I have had this problem on my RC10GT, whenever I came off a jump it would take off full blast and not stop till it flipped over.

Come to find out that the pipe support was sliding up and down on the pipe whenever I landed from a jump causing the radio to glitch.
I reproduced the sliding action and watched it glitch the radio.

The pipe May or may not be the case on your truck but certainly worth checking out.

You could also do what was suggested earlier and put a spring on the throttle. any spring will do really, just make sure it has enough recoil to pull the servo arm back when no power is going to it.

One last thought... I know you probabaly already did this, but check your batteries. If you run nicads they could be dumping 3/4 tank into a run. They may have developed some memory and need to be cycled.

If your running alkalines, get rid of them and get a charger and some Nihms or nicads, will save you tons of money.