Arcing/Glitching Problem
 

Hey Guys,

I finally got my TXT-1 back together and it's playing up on me!

I have installed a Super Rooster and 2x 17T Venom Fireball motors in parrallel, I use Venom 3300mah packs and everything is wired up using Deans plugs. The problem is when I use reverse the Motors jerk and change direction, or it has a spastic, the steering sometimes glitches when i put it in reverse also! When this happens you can see a spark coming from where the brushes contact the comm. So I went through and re-wired the motors, installed capacitors and checked everything, everything seems fine, but it still does it, sometime's worse than others! This is really annoying me because I feel I've done all I can do, I've called a hobbyshop and they said it might have something to do with the aluminium ladder frame causing interference, but it can't be because It still happens when i run it out of the truck? Dunno, I hope some of you might be able to help me with this problem? I can't take it to a hobbyshop because the closest one is 2 days drive away.

Cheers

Dave

Sounds like unwanted Rf interference. Try changing the position and orientation of your Receiver.

Are you using a schottky diode? If so, get it off there. I assume you don't have a schottky on there, but I had to mention it.

Next, check the timing on your motors. If I were you, I would keep them at a maximum of 10 degrees. You have to consider that in reverse, your timing is reversed, and that 20 degrees of timing then becomes 20 degrees of retarded timing, and will make wierd crap happen.

You are patially right, the RF interference is likely coming from the arcing, which produces stray waves, that then find their way into the antenna. :)

If he's used Schottky Diodes, they'll have blown once he put it in reverse.

True, but that could still be a source of glitches, but not the whole problem.

Thanks for the replies guys.

I'm not using Schottky Diodes, I was informed that that was a BIG NO NO with Reversible ESC's. I have three capacitors installed as per the Novak instructions.

I tried moving the ESC and Reciever as far away from each other as possible to no avail.

The timing of the motors is set to 0 degrees, should that be alright?

On another forum a guy said it could be something as simple as replacing my transmitter batteries, so I'll try that tonight.

Thanks again

Dave

Keep the reciever away from the servo as well. Servo, especially metal geared ones, cause intereference when they operate. Seeing as how this issue only occurs in reverse, I am not sure if it is entirely the fault of inteference. I would run anywhere from 4 to 7 degrees of timing on a mod like that. The Venom Firebal modifieds are budget modifieds. They are a litle cheaper than a good Speed Gems or Reedy, but they'll get the job done quick enough. As for 20 degrees of timing, that is insane for a 17 turn wind! You can try 20 degrees of timing if you want your motors to draw more amperage than the starter in your full size car! :lol:

Also, do you have 3 diodes on just one motor or on both motors?

Arcing will occur in most every motor when it is forced to run reversed timing. It is unavoidable, because every component on the motor is designed to operate it's best in one direction. The springs may be different from positive to negative (not sure on the Fireball. I have a 15 turn Fireball downstairs but it's buried under about 30 or 40 other modified motors :D ), the brushes may have a softer edge on one side, and other factors affect the severity of arcing. They will also arc when braking. It's not something to be dreadfully scared of, just something to be aware of.

I have 3 capacitors/diodes on both the motors.

Here's what you need to do:

Disassemble both motors, cut both commutators, clean everything, reassemble them, and quite possibly the problem will be gone. From what you have said, the only logical cause now is out-of-round comms.

If that doesn't work, try a stiffer brush spring.

:)

What radio gear are you using? Is it old? Have you ever dropped the crystals? Or used the receiver where it has been subjected to vibrations without adequate insulation? What about the aerial wire? Sometimes, these type of problems can occur from dirty pots inside your transmitter. Similar glitch problems can occur when the capacitors in your receiver start to break away from the PCB, or if moisture has entered the receiver (or condensation if you have the receiver wrapped up in a balloon or other waterproof material).

Electric motors can sometimes cause interference, and a dodgey comm will cause excessive arching - Phatkat has detailed getting the comm cut. But I think at this stage, some more information is needed regarding the actual radio.

I agree. There is a definite problem with the comms, but likely something else is going on too.

Everything is brand new, surely I shouldn't have to cut the comms in brand new motors? I don't really have access to a comm lathe anyway.

I'll see what I can do over the next couple of days.

Thanks heaps for the info guys, it's greatly appreciated.

Dave

What radio?

Sorry, this is the Transmitter and Reciever I have...

Sanwa Radio

The radio you described has 'dry cells' in the Tx. These metal tabs are notorious for corroding and/or not fitting up tight enough against the cells causing poor connections. It's not normally a problem when they're new though. :confused:

As for Xtals, if they've been dropped, it doesn't matter how new they are. ;)

Certain bands are more prone to interference, 27Mhz AM is particularly iffy. I can't comment on 75Mhz, but FM radios generally give a much more reliable signal.

What you might want to do is a try range check and get a friend to help you. Disconnect the motors and try the radio for range and see if any glitching occurs. If glitching does occur, you can rule out any car related causes. Then you can concentrate on the radio - Tx, Rx, Xtals, Aerials, etc.

Thanks Horatio,

I changed the TX Batteries last night, just incase it was something as simple as that, but, that did nothing :(

When I get some more time I'll go through some of your suggestions and see if I can knock this problem on the head.

Thanks again

What do you mean by this, how could they be different from positive to negative?

Because when I pulled the brushes out to check them, I heaped all the springs together, not taking notice of which one came from where!!!

When motors are manufactured, the comms are just kinda "shoved" into place, and are not completely round. That makes the brushes bounce, and the hotter the motor, the more they bounce. I think you really need to have the comms cut, at least to just know that they are not the problem. I know you don't have convenient access to a lathe or shop, but I will offer you this: If you want, you can ship me your armatures, and I will cut them for you, no charge. I have 14 years' experience in this hobby, and know very well what I am doing, so I can promise you that I will care for your parts very well. Let me know, you can PM or email me.


Matt

The comms are never perfectly round, even from the factory.

Arcing will always occur to a certain extent, it's damn near impossible to get a motor to operate without a little bit of arcing. The brushes will always bounce a little bit. The Fireball's are a bit on the "inexpensive" side, and they may be a little tweaked from the factory. Just get the arcing down to a reasonable amount and see if your glitching goes away. Phatkat has given you just about all the info you need to get rid of your arcing problem.

I just realized something!!

The suspension is specifically designed to operate in one direction. My Juggernaut hates reverse! What if when you drive in reverse your front wheels just jiggle because they aren't designed to operate as efficiently in reverse?

As for the arcing, re-program your Super Rooster. If when you let off the gas or hit reverse the brakes enable to fast or not enough, your motor's may act erratictly. Arcing happens a lot of times in reverse and under hard braking. Program the ESC and adjust your trim.

Hey Guys,

Sorry it took so long to get back to ya's.
I went through and tried everything you have suggested but the glitching problem remained. Thanks for your offer Phatkat but it would cost me more to send you the motors to have the comms machined than it would be to buy new motors, cheers anyway.
So, I don't know why I did it, but I plugged the Reciever pack back into the reciever (with an ESC you don't have to have a reciever pack) and more than 3/4 of the glitching and spastics went away!!! :confused: I have accepted it the way it is now, although it still glitches, it's better than it was!
Why should hooking up the reciever pack remove most of the glitching, I don't understand???

Sounds like a dodgey Rx to me. Or some sort of lead problem from the Speedo. That's the thing with these kind of problems - without actually having the gear in front of you, it's difficult to help.

Post some pictures if you can, that should save a 1000 or so words.