sweli

My Feedback: (7)

Have a large scale 1:8 or 1:6 project truck that I am having trouble getting the ESC and BEC to work well on.

Heavy chassis - 20lbs
Hacker Brushless A30-8XL (1100kv)
Quark 33 Universal ESC
Tamiya High Lift 3spd
Tower Hobby MG995 steering servos (1fr, 1Rr)
Cheap servo doing the trans shifting.
Cheap X'tal FT06-B Tx/Rx

Finally got the ESC to do forward and reverse.
With only BEC (5v3amp) from Quark ESC, the steering is sluggish, weak, sometimes not responsive.

I soldered up my own heavy gauge servo harness/pigtail.
As it stands right now, Quark ESC BEC is plugged straight into ch3. This provide power to the Rx and transmission servo.
Then I have a second, stand alone BEC, plugged into my pigtail harness. This harness has the red and black wire from the BEC going to the red and black wires of the front and rear MG995 servos. The black neutral also goes to the Rx, as well as the orange signal to the Rx.

This setup works well, ie. steering has a lot of power. Except, when you get above 1/4 throttle, you loose 100% of the steering control? In fact, if you are turning the wheels while you accelerate, the wheels stay locked in the turned position, until you take the throttle back to neutral, then the steering servos return to their neutral position.

I doubled checked my BEC pigtail, and it is not returning power to the Rx.

Help?
Cross talk?



Second test:
When I plug the ESC through a different pigtail, removing the red wire, and plug the stand alone BEC into the Batt on the Rx, steering works fine, but I get no ESC control at all. In fact the ESC gives a funny single beep and no lights upon power up.

Hmmmmmmm?
Is it the funny cheap radio (made for Euro) that I am using?

Other ways to get steering servos the power they need?

Any help appreciated.

t9dragon

My Feedback: (11)

What battery are you using?

sweli

My Feedback: (7)

3800mah Nimh, 6 cell, TEnergy generic brand (all over Ebay).
Dean ultra connector into a "Y" harness I made that splits between a female Dean Ultra and Dean Micro.
Dean Micro goes to stand alone BEC.
Wires out of battery are 'OK'.
My Y-harness uses high quality silicone cased wires.

Do you think I am pulling more then it can give?

sweli

My Feedback: (7)

Hey T9dragon,

You might be onto something.
I have two of those 3800 packs. Charged both on my Integy charger about 4-5 days ago. One not used, one used to get the ESC programmed.

Test 1: used both battery packs to power it. One into ESC, one into separate BEC. Works great.

Test 2: Gave each a full charge. Now one works fine on the bench.

I won't be able to give it a run around the basement until I finish some driveshaft and steering linkage adjustments. Guess we'll see how long a 3800mah cheap stick lasts moving 20lbs around with 4ws.


Any other chime in is appreciated.
Should I stick with a 6v receiver pack running the steering servo's?

I see Novak makes a nice 6v, 5a BEC.
Castle makes one also, but makes you buy their USB castle link to adjust it from the 'out of the box' 5v.

thx
sweli

sweli

My Feedback: (7)

So I found the stand alone BEC was either overloading or maybe starving when the truck was in motion past half throttle.

The cheap Towerpro MG995's are rated up to 7.2v, so through the pigtail for the front rear steering, I am running straight 7.2v(dirty, no filters) to the front and rear steering. Still have 6v BEC to the trans servoa and Rx, through the ESC.
A little more noise at neutral, but wow the torque! They'll turn 40series Moabs at a standstill, on carpet and cement with no problem. My suspension gives before the the servo does.

I'll see how long they last.

cflight

Unitedhobbies has a 5/6v bec for reasonable money, with a swap pins set up...?

You are definatly straining the bat. , figure moving 20lb.s with a big motor and only 7.2ish V....Amp draw is probably higher than you'ld think. If you wire yourself up the way you started and run two bat.s in parrellel, positives together and negatives together, you'll keep your Voltage and double the available current, Amps. Not to mention longer run times and use of a regulated bec for the servos.
Of course the bat.s are probably dropping from full charge to below 7.2 at the first juice of the throttle, as long as your playing the voltage out of a full charged pack, your not really going to damage your servos.

How can you beat these MGs ? I can't stop picking them up 2 at a time! I don't even know why! But hey there's a little esc in each one!

sweli

My Feedback: (7)

Thanks Cflight.
I thought about parallel batts, but then thought about the pig sized weight I was already hauling around and didn't want to add to it.

It runs well now and its not overheating anywhere. Batt, connections, ESC, motor feel warm but never hot.
[ul][*] I removed the 6v3a BEC I was running. [*] The Towerpro MG995 servos are supposedly rated 4.8-7.2v.[*] ESC BEC provide Rx and transmission servo 6v3a.[*] Pigtail harness from batt dean connector provides straight 7.2v to the front and rear steering servo
[/ul]

I have run two batteries in this configuration and it seems to work well. I get about 20min runtime on my cheap 3800 pack. My guess is I was drawing more then the BEC could handle and it was browning-out.

Whole truck was an experiment. Articulates well. Way to high of COG. Crawls and can do 8-9mph. Huge ABS jeep body has leds mounted everywhere and my nieces want one of their old barbies driving.
thx

cflight

Hey Man that sound like a cool project to say the least.

20 min. on 3800mah, your amp draws fine, I assume the bec isn't a switching buck regulator and was burning off the voltage with resistor restriction and heating up??? Got me? Maybe turning 20 lbs does draw more than 3A in 2 steering servos...?
By running 7.2 to them you've dropped the amps on the boards and increased voltage, allowable on those servos, so your probably better off!

1:6 Jeep huh...have you seen the 1:6 WWII Willys or is that what Barbies driving this summer?
http://www.customrcmodels.com/index.htm