RCCrawler Forums

Jus · 07-21-2011, 03:48 PM

Just did some upgrades to my scx-10. Installed a Holmes BR-XL and a Savox 1256TG servo, 277oz @ 6v. Radio is same Spektrum DX3.0 and SR3000 rx that has been in the truck. Integy 35t lathe motor.

Running mostly Venom 3s 5400mah 20c lipo also a Thunder Power 3s 2250mah 45c. Oh and today I was running a like new Venom 2s 5000mah 20c lipo and when negotiating through rough rocky terrain it seemed to cutout more than it did with 3s.

I've been having a bit of an issue with power cutting out to both the servo and motor. Not a glitch but seems like the system overloads and after setting for 4-5 seconds it comes back to life and servo centers itself. Can't pinpoint whether the servo is always in a bind when this happens, don't think so though.. It's been most noticable when climbing and need more throttle. Is the servo sucking too much juice for the esc to handle? I was under the impression the internal BEC on this esc could handle most single servo setups. Considering how mild this servo is by comparison of some of the other servos out today I thought I'd be alright.

JonU · 07-21-2011, 04:33 PM

Sounds like the same problem I have in my xr10. I'm going to be installing my cc BEC and I would guess that you are drawing more power than the BEC can handle. But from what I've heard, the brxl should have no problems short of a competition setup.

outkast7222 · 07-21-2011, 06:03 PM

Sounds like the BEC to me too.

Charlie-III · 07-22-2011, 12:00 AM

I would start by checking your steering EPA's to make sure that is not the source of your overload (which is likely what is happening).
I would be surprised if the issue was the HH BEC that is built in, it should be fine.

The 20C rating is NOT helping you though. Did you try the 45C rating???

Jus · 07-22-2011, 06:37 AM

I'm very meticulous when it comes to my steering. I've spent hours tweaking the steering in this truck. Part of the most recent upgrades were aluminum C's and knuckles and CVD's. I can assure you it's not the EPA's causing interference.

I know the Lipo C rating is less than ideal but I've never had trouble with it before?? Never ran with a servo this powerful before though either.. Some time was spent with the Thunder Power 2250mah 45c unfortunately I can't remember if it never happened during that time. Next time out I will run one of these batts in the terrain it's acted up the most and see what happens.

JohnRobHolmes · 07-22-2011, 07:14 AM

I would say the BEC is the culprit of the shutdowns. The Savox servos are very inefficient for the power and so it will draw more amperage as compared to something like a Hitec of similar strength. Generally the BRXL can take a single servo setup with no sweat. Sometimes it just can't handle it for terrain, driver, vehicle, or servo reasons.

Jus · 07-22-2011, 08:03 AM

Thanks for the reply John. Interesting info on the Savox servo... I just thought it sounded good for the price and wanted to try one.

Would it be a worthwhile experiment to swap out the Savox servo for the Hitec 7955TG that's in my comp rig? The comp rig has a BEC so the Savox will be happy. And hopefully the BRXL and Hitec combo would get along a little better?

JohnRobHolmes · 07-22-2011, 09:03 AM

If you have the time it wouldn't hurt to try it out and see what happens.

Jus · 07-22-2011, 05:17 PM

I took the rig out this afternoon for probably an hour with the Thunder Power 3s 45c lipo. It died out a couple times and I really wasn't working the servo that hard.. One time the wheels were almost straight, but I was on and off the throttle.

Temps were a little high.. But then again it was one of the hottest days of the year, and unusually high for VT.. It was around 100*F. The servo was about 115*. The motor was 150* and the esc @ the heatsink was 150*.

Let everything cool down for a bit drove some more and hit cutoff and called it day.

I am considering doing the servo swap as frankly I can't afford to get a BEC @ this time.

JohnRobHolmes · 07-22-2011, 05:41 PM

I'm using a BLS352 on my shafty, and have never had a shutdown from the servo. I would be interested to know the amp draw of those Savox servos.

Jus · 07-22-2011, 10:29 PM

I swapped servos tonight. Put the Savox in my comp rig w/ BEC set at 6v. Servo seems to turn lock-to-lock faster and less twitchy now. One thing I forgot to mention earlier was that just sitting on the bench plugged in if I tried to turn the wheels back and forth quickly it'd cause a brownout for 2-3 seconds and didn't like to do that. Hooked up with the BEC the Savox turns back and forth effortlessly now. Good sign.

Put the Hitec 7955TG in my scx-10 with the brxl and tried the same lock-to-lock motion as fast as I could and it also is very quick and smooth. Even better sign.

Apparently Savox servos really are kinda funky.

Charlie-III · 07-23-2011, 06:01 AM

Sounds like you resolved your issue. What you were describing at the beginning sounded like a brownout due to load, but I keep reading that the BRXL has a good BEC unlike some ESC's, thus my concern.
It also sounds like the Savox is a power hog......

JohnRobHolmes · 07-23-2011, 07:20 AM

The BRXL has the strongest internal BEC on the market, but it still can't hang with some servos or situations.

Thanks for the feedback.

SuperRoo · 07-23-2011, 11:30 AM

Quote:

Originally Posted by JohnRobHolmes

I'm using a BLS352 on my shafty, and have never had a shutdown from the servo. I would be interested to know the amp draw of those Savox servos.

From the Savox website for the SC-1256TG:

Running current (at no load): 100 mA @ 4.8V
Running current (at no load): 120 mA @ 6.0V
Stall current (at locked): 4000 mA @ 4.8V
Stall current (at locked): 5000 mA @ 6.0V
Idle current (at stopped): 5 mA @ 4.8V
Idle current (at stopped): 5 mA @ 6.0V

The high resolution of the Savox servo could also be causing the trouble with the older Spektrum radio.

Combines leading edge technology with super high 12 bit (4096) resolution

Jus · 07-23-2011, 04:57 PM

Quote:

Originally Posted by SuperRoo

The high resolution of the Savox servo could also be causing the trouble with the older Spektrum radio.

Same tx and rx are being used in the comp rig, only difference now is the Savox servo is being fed by an external CC BEC and it works fine.

I took both rigs out today on the rocky slope where I spend a lot of time.. Had the brxl & Hitec 7955TG equipped rig binded up really bad on several occasions and both performed flawlessly(Running the Venom 2s lipo mentioned earlier in the thread). Same goes for the comp rig that now has the Savox servo. I should've stuck to Hitec that's treated me so well but for $20 less than the 7955TG I just had to try it.

Oh well, it works.. We'll see how it works out in the long term.

07-21-2011, 03:48 PM	#1
Jus I wanna be Dave Join Date: Jun 2008 Location: Vermont Posts: 2,016	Power cutting out to servo and motor Just did some upgrades to my scx-10. Installed a Holmes BR-XL and a Savox 1256TG servo, 277oz @ 6v. Radio is same Spektrum DX3.0 and SR3000 rx that has been in the truck. Integy 35t lathe motor. Running mostly Venom 3s 5400mah 20c lipo also a Thunder Power 3s 2250mah 45c. Oh and today I was running a like new Venom 2s 5000mah 20c lipo and when negotiating through rough rocky terrain it seemed to cutout more than it did with 3s. I've been having a bit of an issue with power cutting out to both the servo and motor. Not a glitch but seems like the system overloads and after setting for 4-5 seconds it comes back to life and servo centers itself. Can't pinpoint whether the servo is always in a bind when this happens, don't think so though.. It's been most noticable when climbing and need more throttle. Is the servo sucking too much juice for the esc to handle? I was under the impression the internal BEC on this esc could handle most single servo setups. Considering how mild this servo is by comparison of some of the other servos out today I thought I'd be alright.

07-21-2011, 04:33 PM	#2
JonU Pebble Pounder Join Date: May 2011 Location: Fort Bliss Posts: 177	Sounds like the same problem I have in my xr10. I'm going to be installing my cc BEC and I would guess that you are drawing more power than the BEC can handle. But from what I've heard, the brxl should have no problems short of a competition setup.

07-21-2011, 06:03 PM	#3
outkast7222 Rock Stacker Join Date: Jul 2011 Location: Elk River, MN Posts: 58	Sounds like the BEC to me too.

07-22-2011, 12:00 AM	#4
Charlie-III I wanna be Dave Join Date: Nov 2010 Location: 07456 N. NJ USofA Posts: 8,314	I would start by checking your steering EPA's to make sure that is not the source of your overload (which is likely what is happening). I would be surprised if the issue was the HH BEC that is built in, it should be fine. The 20C rating is NOT helping you though. Did you try the 45C rating???

07-22-2011, 06:37 AM	#5
Jus I wanna be Dave Join Date: Jun 2008 Location: Vermont Posts: 2,016	I'm very meticulous when it comes to my steering. I've spent hours tweaking the steering in this truck. Part of the most recent upgrades were aluminum C's and knuckles and CVD's. I can assure you it's not the EPA's causing interference. I know the Lipo C rating is less than ideal but I've never had trouble with it before?? Never ran with a servo this powerful before though either.. Some time was spent with the Thunder Power 2250mah 45c unfortunately I can't remember if it never happened during that time. Next time out I will run one of these batts in the terrain it's acted up the most and see what happens.

07-22-2011, 07:14 AM	#6
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	I would say the BEC is the culprit of the shutdowns. The Savox servos are very inefficient for the power and so it will draw more amperage as compared to something like a Hitec of similar strength. Generally the BRXL can take a single servo setup with no sweat. Sometimes it just can't handle it for terrain, driver, vehicle, or servo reasons.

07-22-2011, 08:03 AM	#7
Jus I wanna be Dave Join Date: Jun 2008 Location: Vermont Posts: 2,016	Thanks for the reply John. Interesting info on the Savox servo... I just thought it sounded good for the price and wanted to try one. Would it be a worthwhile experiment to swap out the Savox servo for the Hitec 7955TG that's in my comp rig? The comp rig has a BEC so the Savox will be happy. And hopefully the BRXL and Hitec combo would get along a little better?

07-22-2011, 09:03 AM	#8
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	If you have the time it wouldn't hurt to try it out and see what happens.

07-22-2011, 05:17 PM	#9
Jus I wanna be Dave Join Date: Jun 2008 Location: Vermont Posts: 2,016	I took the rig out this afternoon for probably an hour with the Thunder Power 3s 45c lipo. It died out a couple times and I really wasn't working the servo that hard.. One time the wheels were almost straight, but I was on and off the throttle. Temps were a little high.. But then again it was one of the hottest days of the year, and unusually high for VT.. It was around 100F. The servo was about 115. The motor was 150* and the esc @ the heatsink was 150*. Let everything cool down for a bit drove some more and hit cutoff and called it day. I am considering doing the servo swap as frankly I can't afford to get a BEC @ this time.

07-22-2011, 05:41 PM	#10
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	I'm using a BLS352 on my shafty, and have never had a shutdown from the servo. I would be interested to know the amp draw of those Savox servos.

07-22-2011, 10:29 PM	#11
Jus I wanna be Dave Join Date: Jun 2008 Location: Vermont Posts: 2,016	I swapped servos tonight. Put the Savox in my comp rig w/ BEC set at 6v. Servo seems to turn lock-to-lock faster and less twitchy now. One thing I forgot to mention earlier was that just sitting on the bench plugged in if I tried to turn the wheels back and forth quickly it'd cause a brownout for 2-3 seconds and didn't like to do that. Hooked up with the BEC the Savox turns back and forth effortlessly now. Good sign. Put the Hitec 7955TG in my scx-10 with the brxl and tried the same lock-to-lock motion as fast as I could and it also is very quick and smooth. Even better sign. Apparently Savox servos really are kinda funky.

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07-23-2011, 06:01 AM	#12
Charlie-III I wanna be Dave Join Date: Nov 2010 Location: 07456 N. NJ USofA Posts: 8,314	Sounds like you resolved your issue. What you were describing at the beginning sounded like a brownout due to load, but I keep reading that the BRXL has a good BEC unlike some ESC's, thus my concern. It also sounds like the Savox is a power hog......

07-23-2011, 07:20 AM	#13
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	The BRXL has the strongest internal BEC on the market, but it still can't hang with some servos or situations. Thanks for the feedback.

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