Strange loss of control issues, root cause?

[flipwils11]

Just finished this gold pan runner I built for my son and it's exhibiting some very strange behavior, which my gold pan runner only does when the batteries are nearly exhausted. The symptom is full throttle seems to "steal" the voltage (my guess) from the receiver and hence the steering and throttle resulting in loss of control. At best if you happen to be turning, it will start doing circles until you run and pick it up. At worst it goes full speed into a curb or other obstacle.

Mine only does it when the battery is on the way to dying so I just use half throttle to finish running it out. Now on his new runner, it's doing it every time I do full or even 3/4 throttle. What's worse is the battery is fully charged so it does (and has) gone straight into curbs because you can't steer or get it to respond. Really pisses me off!

I'm running an old pistol grip Futaba Magnum 1024 pcm radio and receiver, Novak XRS esc, futaba older steering servo, and nicd batteries. The same thing happens with a 4500 nicd or the 1800 pack.

[mikedealer]

could be bad crystals? could be a servo issue (is the servo vintage or modern)? or you may need one of these
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXNRE0&P=ML

[flipwils11]

could be bad crystals? could be a servo issue (is the servo vintage or modern)? or you may need one of these
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXNRE0&P=ML

Perfect! Seems like a good idea to me.

The crystals are brand new from Tower because the radio didn't come with any. Hopefully over its life, the receiver's antenna wire was never cut because I remember that was a no-no. The behavior seems associated more with not enough power resources for the motor and receiver though. That capacitor seems like a great idea.

Is this behavior more prevalent in any battery type due to the demand for voltage?

[jwscab]

yeah, with a hot motor, and especially a weak battery, you can get voltage dips that can cause stuttering or glitching.

as a quick test to figure out if it is for sure a voltage sag, if you still have a cell pack from the radio, you can put 4 cells it in, plug it into the battery slot in the receiver, and pull the red wire out of the speed controller plug, so that it doesn't backfeed into the receiver. you will have to switch on the receiver switch first, then the esc switch, and run it around.

under heavy full throttle high load you will see the issue, so if you see the symptoms disappear, then you know for sure it's in the power system, and can either gear it slightly differently, run a stutter stopper/glitch buster type cap, or even improve the battery esc connector; voltage drop from high current can be pretty significant with tamiya and other cheaper type connectors.

[flipwils11]

Alright, I guess I need to try some of the other suggestions in this thread because I got the little Novak capacitor and it still does it. The 4500 mah pack is horrible and it goes out of control, but the 1800 mah nicd packs are just fine.

[mikedealer]

try some of this
http://www.teamnovak.com/tech_info/ts/ts_potAdj.htm#tsg_ADJ_2

got me otherwise

[shane]

Sir, if I can be of some help.
I had a few beers and thought about it, and had more beer and thought about it some more.
Sounds like you may have to "old school" process of elimination ( or at least narrow it down for ya ) You have enough electronics that you know DO work, so start with good batteries for your transmitre and receiver, that you know are good. Next step: Diconnect your esc from your receiver ( this is where you use a receiver pack) and steering servo. Power up. From here we just have to think it through, now test a servo (any servo, maybe the one you just unplugged, but only one, for now, and best if you know it works perfect) in each port on your receiver (kinda basic nitro style). See if the servo acts up in each port. If the servo works perfect in each port, we know the problem has a strong chance of being in the esc, motor, or battery and we go from there. If the servo glitches or has problems in any port, we backtrack through the system from there ( this is where I swap out crystals and test ).
You might already see where I'm going with this.
I hope I didn't leave anything out and I hope this is of some help. If you need more help from this point, let me know.
Please let us know how you make out.
At this point, I will have a beer and think

[flipwils11]

I'll go back and reprogram the Novak ESC and revisit all the settings on the radio. If that doesn't work then I think I'll try using my radio and receiver and see what happens. I also have a few spare receivers and even a spare radio (thanks civilguy). I hate troubleshooting, I'd rather be driving!