Perplexing Mystery...

[ExoSphere64]

Being new to the hobby I expected occasional issue to find me but this one really has me bewildered. I am sorry in advance as this is going to be a little long winded but I need to supply as much info as I can in hopes of finding an answer.

Let me start from the beginning. Early this summer I bought a TRX-4 Defender. It was very reliable and has brought be much joy. I have done extensive modifications but they all have been purely cosmetic.

Enter last month. Out on a demanding trail run and a couple of hours in I experience total steering failure. Based on everything I have read, the stock steering servo blows chunks. Easy fix. New, upgraded servo. (Side note: Only after ordering the new servo, I discovered that the stock servo was just fine, the brass drive gear just stripped out the plastic horn. ordered an aluminum horn)


I ordered the Traxxas 2255 high torque 400. Plug and play. All good for a couple of weeks. Then tragedy finds me once more. 15 minutes into a session, the ESC bakes off and ends my day. Visa card rescues me with a factory stock replacement. Everything back in working order. ( I also picked up a fancy BEC but did not install it)

Fast forward to a couple of weeks ago. Out on a great trail ride. Could not have been more perfect. About 3 hours in, I start having steering issues. Sluggish left and right, very slow and stuttering a lot. I was really bent thinking that my brand new steering servo was already failing. On further inspection, I noticed my transmission and diff lock servos were stuttering as well. (forward/brake/reverse inputs were working fine). I assumed it may be weak batteries in the transmitter so I swapped in a set of new ones. The transmitter never turned back on. It had completely failed. I swapped batteries several times and it was just dead. Visa carded a new one.

All was well in Defender land. I had a beer or 7 and decided to buzz the neighborhood tonight. 20 or so minutes were trouble free. Then all steering faded again. Because of the last experience, I checked the other servos and they were all doing the twitch dance as well. (Transmitter still communicating this time).

I shut everything down and started this post. The one thing that has been nagging me is maybe the steering servo is at the root of these issues. Also being so green I noticed (tonight) that the steering servo I installed was brushless (in a stock brushed) setting.

If anyone has actually read this far (miracle) does anyone have any advice?? Again, being so new, I miss some things. Tonight, while gathering information I noticed that the new steering servo was brushless. Could that be to smoking gun?

I am hoping one you you rock stars can help me figure this out!

 

[meatmonkey]

Firstly, when Traxxas electronics die, don't replace them with more failure prone Traxxas electronics. There are better performing, more reliable electronics available at similar costs.

Secondly, it sounds like your servos are all hitchy twitchy due to voltage variations because the stock ESC has a weak internal BEC that is mediocre at best powering 4 servos. You really want a seperate BEC, such as the Castle Creations BEC2.0 or similar. Even the external BEC Traxxas sells as an upgrade is not exactly sufficient depending on the amperage demands of most strong steering servos.

Running a brushless servo in a truck with a brushed primary drive motor won't cause issues. You just cant mix and match beushed/brushless drive motors and ESC's. However, some if the nicer ESC's, such as Castle creations Mamba x are capable of running both types of motors, but that type must be selected through a Castlelink before powering up the ESC.

 

[HDMM]

Meatmonkey pretty much summed it up......"thumbsup"

 

[OSRC]

Agreed 100% with meatmonkey, the upgraded steering servo is drawing more amps, and most likely is putting too much pressure on the ESC's internal BEC which can cause a cascade of issues.

Highly recommend at least a Hobbywing WP1080 ESC. Rock solid ESC, and a perfect replacement for the stock unit. Absolute steal at $40, and money well spent imo.

Traxxas stock electronics are hit or miss. Out of 5 trucks, I have 2 TRX's that are still running all stock with no issues (in fact, my x6 seems to have a ringer steering servo.) The other 3 I've already upgraded stuff and I've re-used their stock servo/ESC in some other rigs with no failures yet. But I've had 3 receiver failures so far, and one of the steering servos I swapped into another rig sounds like death. It's working, but probably not for long.

 

[ferp420]

Traxass electronics are the worst in my opinion atleast .

your new high powered servo most likely is browning out from not enuff power and most likely is toast and might have taken the other servos out too you need a bec for high powered servos

When a servo dosent have the amps to run it it works harder then gets hot if it gets too hot the motor will loose power till.the point it will bearly work or just stop working all together or let the magic smoke out remeber its realy hard to put the smoke back in and the servo wont work with out it

Other possibility is your end points arent set and its drawing to much power trying to push past the steering lock and browning out so check your steering setting's first seeing as how you changed radios and servos

theres also a cheap bandaid in the form of glitch busters basically a capacitor you plug in to the reciver to smooth out power spikes always good to have when powering the servos though your reciver

 

[durok]

Remember, the stock Traxxas shift and diff locker servos can take a MAXIMUM of 6.0volts - so you'll need to make sure your ESC or BEC is not delivering more than that.

This is a known issue...

 

[HumboldtEF]

Hey Robert I think meatmonkey nailed it with the amp draw and BEC issue.

One thing that would solve both weak points is a Mamba X ESC https://www.rpphobby.com/product_p/cse010-0155-00.htm

Its overkill for a brushed motor but its actually in stock and has a internal BEC thats good enough you wont need a separate external BEC.

The Torquemaster ESC from Holmes Hobbies is one of my favorites for Brushed motors though it will likely require a separate external BEC to power your amp hungry servos https://www.rpphobby.com/product_p/hh-210100002.htm

As noted make sure to keep the shift and diff servos at or under 6 volts. The way I like to accomplish this is with a bypass adapter https://holmeshobbies.com/electroni...ssories/holmes-hobbies-rx-bypass-adapter.html
These can be made if you have some servo ends and wire, just copy the wiring in the image. A BEC will plug into this and the other ends will plug into the servo and the receiver, the (steering) servo gets the full voltage from the BEC (whatever you set it to) and the receiver end just gets a signal with no added voltage.

EDIT: sorry I left off the easiest option, Just add an external BEC like this https://www.rpphobby.com/product_p/cse010-0004-00.htm

 

[ExoSphere64]

Thanks everyone. It makes sense now. "Brown out" really sums it up. I will go back and retrace my steps and see what else I can learn! You guys rock!

 

[mewalsh100]

You could also purchase a hi-torque, direct power servo. This would isolate your micro servos, keep them happy at their 6v, and eliminate the need for the BEC. It's been beaten to death, but absolutely agree on the Traxxas electronics. A much better, more cost effective solution for a brushed system would be the Hobbywing1080 esc and any of a variety of Holmes brushed motors.

 

[Inspector86]

I would recommend replacing the stock ESC with an HW1080 WP. This will power your up rated steering servo without the need for an external BEC for a LOT less money than the Mamba X. Don't get me wrong the Mamba X is a great ESC (I have a couple of them) it is just overkill for your application.

 

[mikemcE]

Meatmonkey pretty much summed it up......"thumbsup"

"thumbsup""thumbsup"

 

[ExoSphere64]

Very good info. It is running for now and am going to just let it be until after the holidays. I just acquired a second TRX4 and want to work on them together but want to wait until the shipping industry recovers from the holidays... Thank again all! "thumbsup"