vanman

My Feedback: (2)

OK, I am a newbie to the RC Car and Truck Scene but have been flying planes for several years so I do have a clue about radio gear....

I finally got my new truck yesterday.....

I stopped out and picked up some fuel, new batteries for the transmitter and receiver and came home prepared to start breaking the motor in......and all started going just fine.

1st tank of gas fine, 2nd fine, 3rd fine, 4th fine during the 5th tank the fail safe came on and no response from the transmitter.....Of course before beginning I verified that when the failsafe is activated the throttle is cut and the brakes are applied....everything checked out fine.

As I was walking up to the truck it went full throttle and took off!!!! Wham, lodged itself under the neighbors trailer and was still running wide open.....I got under the trailer and got the truck shut down, got it out from under the trailer and a casual inspection only showed a couple of things bent but nothing broken..... The failsafe was on red.

I shut off the truck and the radio, and then turned everything back on, the failsafe reset and everything appeared ok.....so I started the truck.....give it gas the engine runs up but does not move.....

I found that I had destroyed the gears in the differentials and had to rebuild them.......

Got that all done this morning took the truck outside again....replaced all of the batteries just to make sure.....1st tank of gas fine, 2nd fine during the 3rd I noticed no response from the radio again..

Luckily I was standing in front of it and so when it hit me I caught it and got it shut down....I noticed this time though that the failsafe was on green......

What the heck is going on????? Why is this thing going wide open and why is the failsafe not shutting it down?????

HELP ME PLEASE!!!! Im not having much fun yet since I have spent more time disassembling and rebuilding than I have driving.......[]

Thanks for your help and ideas!!

Bill

Dr.ArmoMaxx

what truck is it? what failsafe? it seems like there is problem with your radio otherways with new batteries why should it fail on you?

vanman

My Feedback: (2)

The CEN Genesis with the radio and failsafe that comes with it

RC Collector

Failsafes usually kick in under two conditions - channel interference or low receiver battery voltage. I don't know the Gensis, but if the installed unit does not sense low battery voltage, and your truck does not have a throttle return spring, it's running away because the receiver battery is dead. In this case, replace the failsafe with a name-brand one and get a return spring.

Failsafes that are set electronically (by pushing a button) can lose their settings. Check this by turning off the transmitter (with the receiver on) before each run. Don't just look for the red light - check which way the throttle/brake linkage is moving. I've had a failsafe apply full brakes when checked on the first tank, and full throttle at the start of the second tank.

IMO, the Genesis looks like it has some power-hungry servos, and those four AA's can't last very long - a 5 cell 6V 1000+ Mah receiver pack would appear to be a critical upgrade.

Gulliver Foyle

The CEN failsafe does detect low voltage, beleive me. Mine has shut down a couple of times. The failsafe is not set from the factory though, so you have to set it before you run. Power hungry servo's? I am using a 4.8 volt, 2250mah NiMH pack and it (Genesis) sucks it down in like 2 tanks.

RC Collector

Gulliver, try adding another cell to your pack to boost the voltage to 6V. I think you'll see a big improvement in run time.

Vanman, it sounds like your failsafe is not set correctly (or is losing it's setting between tanks) AND your receiver battery is going flat after two tanks. Reset the failsafe and check it before every run, and invest in a 6V, 5 cell Nimh pack with the highest capacity you can get. It might be worth having your LHS build one for you using high-capacity cells.

COPO

You should really install a throttle return spring.. These work no matter what, unless a gear in the servo breaks and jams it. very unlikley though. I have not used a failsafe for a while now as the spring does it all.. Very easy to set up and cheap..

Gulliver Foyle

I build my own packs, thanks though. 2250 NiMH are the highest cap I can find right now, and they are AA size. 2/3 A sized cells I have seen are only 1100mah, and you can't fit 5 AA cells in the Genny battery box box. I am going to try a 6 volt hump at some point in the Gen.

RC Collector

Gulliver, where did you find the 2250 AA cells? I'd be interested to put some in my TX. Judging by the power-consumption of the Gensis, I would look into installing even a subC 5 cell pack somehow on the chassis. I run a 2100 NiCad in my 1/5 scale, and get about 50 minutes of runtime with two quarter scale servos.

Hooch, the throttle return spring is important, and the Gensis should be fitted with one, but it does not protect against frequency conflicts. As long as there is power to the servo, the servo will easly override the spring.

Gulliver Foyle

http://www.batteryspace.com In addition to highest cap NiMH cells I have seen, their prices are great. I have yet to get a bad cell through them. Some of their chargers have problems if you read their tech support, so I would steer clear of those. I like the idea of the sub-c RX pack, I might try that. I use the AA 2250 NiMH in all my transmitters, and especially appreciate them in my M-8 where power consumption is an issue. I assemble the AA's into receiver packs and on 1/8 buggys I have run 4 tanks in a row with no appreciable loss of power. I really don't know how long they (RX pack) will last as I never ran one vehicle long enough to kill one. Once after peaking one of my receiver packs in the morning before our Sunday run, I accidently left the power on my buggy on, did'nt notice, and by the time I got to our parking lot an hour and a half later, it still had enough power left to run through 2 tanks.

RC Collector

Thanks for getting back, appreciate the info. Will get met a set and try it.

Vanman, hope you found the info here of value towards preventing another run-away ... hate to have 18 pounds of Genesis coming at me out of control ...

vanman

My Feedback: (2)

Guys,

Thanks so much for all of the input! I apologize for not saying anything earlier, but left for 10 days on vacation and couldn't check my email.....! DOH!!! I felt like a junky that couldn't get a fix!!!

I am going to upgrade my battery for sure!!! AND add a return spring.

Has anyone tried putting the Li-Poly packs with a 6 volt regulator in theirs? I actually have been using them on my planes and they really last and CAN take the power requirements...I am pulling over 10amps continuous in one application and have over 200 charges on a couple of my packs......keep expecting one to die but they haven't yet.

Li-Poly was the direction I was thinking anyhow..... CEN wants my truck back so they can check it all over.......which sucks since I will now lose it for a couple of weeks....unfortunatley they sent UPS to pick it up AFTER I had left for vacation or it would be back waiting for me now....[>:]

They are standing behind it pretty well so far though...

Again thanks for the input!

Bill

vanman

My Feedback: (2)

Some more information to assist in troubleshooting after reading some of the suggestions above.....

The failsafe was indeed set up and working correctly...I checked and verified the operation several times..... including after each of the runaways!

On both occasions the truck was sitting still and idling, then full throttle run away....so the servo had to have been driven forward.....(which I can see if it is in a loss of signal state with no failsafe) If the receiver pack was dead or REALLY low, do you believe it would have had the umph to drive the servo and maintain it at that point????

Would the return spring have helped me in this situation? On both occasions it was in the constant full throttle position until I could get the engine shut down...... That's how it blew the gears in the differentials...... I suppose if it glitched with enough power to go full throttle and did not have enough power to return the servo it would stay at the driven position and the return spring would have pulled it back.....?????

What type of spring should I put on it????

Thanks again guys!

Bill

RC Collector

The failsafe detects low battery voltage and will engage at that point, if set correctly.
As long as there is power going to the servo, the throttle return spring will not be able to return the servo arm to the idle position. The spring's sole purpose is to close the throttle if there is a complete loss of power on the truck.

You should use the mildest spring you can to do the job. If the spring is too strong, there will be an excessive power drain on your battery. To find the right spring, you must experiment a little. Hook the spring up and, with the truck receiver off, open the throttle manually by turning the servo horm. Then let go. The spring should be strong enough to just overcome the servo to close the throttle.

In your case, it could be a defective failsafe, whereby the low-voltage sensor is not working.

Having said that, here's a failsafe "not-safe" story of my own ...

At the start of the third 15 minute tank, I checked the operation of the failsafe on my 1/5 scale. It was night, the body was on and the engine off. I always perform this check at the start of every tank. On the previous run, I did this check with the body off, looking at the linkage moving to full brake. This time, I heard the servo whirr, saw the red light go on and concluded that all was OK and started my run.

Ten minutes later my car took off on a 40 mph full throttle run-away, which luckily ended with a swipe off the curb, a flip, and no breakage. Reason: my failsafe lost it's setting when I re-connected the battery for the third tank, meaning that it moved the throttle to wide-open when the battery ran down. I didn't check the movement of the linkage on that run, otherwise would have seen the problem. First thing I did after that was to replace the electronic push-button unit with one with which is set by turning a potentiometer (from Venom).

geofferama

Give them 2 more years or a hundred or so more cycles, they might not fail, but you'll notice significant degredation. Here's a quick way to figure how much longer they have: All lithium batteries have an aging problem. They'll lose around 20% capacity per year @ room temp. Deep discharges will kill them faster and heat will kill them fastest of all. (toss 'em in the fridge with a 40% charge & the loss is minimal)


Li-Poly's may have the lowest weight of any battery
but please don't use them for R/C cars:

1. You must use a li-on/li-poly charger. absolutely must. From Dansdata.com:
"if the charger delivers more current than they expect, or charges them too long, they can and will die spectacularly, possibly destroying your laptop, luggage, desk or lap in the process." Or in this case your (real) car or house.

2. Li-Poly's are fragile. "High case temperature resulting from abuse of the cell could cause physical injury. Rupture may cause venting with flame." Vanman might have heard about li-poly's bursting into flames after a plane crash. I've heard about garage/house fires.

They have their place, but nitro trucks ain't where its at. They're unforgiving and as described [link=http://www.rcuniverse.com/forum/Using_LI_Po_Batteries_Safely/m_1238924/tm.htm]in this thread[/link] "the [battery] fails instantly and catastrophically." Safety comes first, that's one of the reasons y'all use failsafe's and a return spring.

Thos

This has happened to me on 3 occasions, twice while in idle and once while driving. On the third occasion I had installed an airtronics FM receiver thinking interference was the cause but was proven wrong. I tested the servo on the Genny throttle and found it twitching an awful lot so I changed it for the airtronics servo I got with the radio kit and this seems to work. I'm bringing my truck back to the shop anyway as the engine wont draw fuel any more and even pumps it back into the tank when you throttle it. I reckon the excessive throttle on runaway may hav done some damage.

tizdaz

hmm

I know when failsafes are setup correct they are meant to be great, but imo too much can go wrong with them, not by fault of its own, but by the user! ...A simple lack in memory may end up with a runaway! ...Ive read so many posts about people who had runaways due to using failsafes than i care to remember! ...i know most of the time its the users fault, but failsafes (imo) can do just as much (or more!) damage than you would get if not using one, providing you have good radio gear & fully charged batteries + battery checker i dont see much use for a failsafe, a simple thing like discon the battery & forgetting to reset failsafe can cause a runaway & 9/10 instead of failsafe going full brake it goes WOT!