Motor/3s Battery Question(s)

[KanchiX]

I almost posted this in the Axial Wraith specific section, but realized it belongs here...

I purchased a Speed Gems motor tonight and I noticed on their site that it's meant for 3.7-7.4v, I wanted to know if I could use a 11.1v battery provided I'd be running it through an external BEC. Would I just blow up my new motor? I do have another I could use instead, that the guys at my lhs said would work fine.

Here's the setup
Axial Wraith
-Holmes Hobbies Torquemaster XL, BR, WP (2s-6s)
-Castle Creations 10amp BEC
-SpeedGems 2 Trinity Diamond 15t Double Modified (or if I have to, a Tekin 35t)
-Savox High Voltage SG Servo

I'm still super n00b at electronics... just afraid of frying expensive parts.
If you have any questions for me, fire away. I should be nearby for the next few hours.

 

[Trubble]

IMO:

15 turns is a bit light, in a truck that's relatively large/heavy.

Hope you intend to gear fairly low.

 

[KanchiX]

IMO:

15 turns is a bit light, in a truck that's relatively large/heavy.

Hope you intend to gear fairly low.

I had a Timbuk2 Wraith system in there w/ a 13.5t brushless, it ran great. I'm still using the stock gearing (20 pinion, 80 spur 48dp) but I did have to metal gear the transmission after it stripped out, plastic gears, meh.

 

[KanchiX]

Wow, after over 6 hours of work, it's done.
Installed the BEC and the Holmes Hobbies ESC, cut away a plastic support that sat above the 2 cell battery to make room for the bigger 3 cell battery, modified some EXO servo brackets to make an overhead style brace to replace removed piece. And lastly fixed an MIP drive shaft I broke yesterday.

It doesn't seem like much but it was a hassle w/ a lot of soldering.

I figured I'd better play it safe than sorry and I used the motor that the guys at my lhs said would work fine. (***Still wondering if the speed gems can be powered and survive under that much voltage though!***)

I'll run it later today and tell ya how it does. I'm wiped and it's nearly 4am. (Initial programing and motor/servo tests went perfect so I know it's just rarin' to go and I can't wait!! 2 bad need sleep....)

 

[Johnnysplits]

You really didn't need the BEC with that particular esc. I say give it the 3s and keep an eye on the temp.

 

[Charlie-III]

Re: Motor/3S Battery Question(s)

An external BEC is NOT to power the motor, it's to power the RX and/or steering servo to take the load off the ESC's internal BEC.

Using 15T doubles in ANY crawler type vehicle sounds WAAAYYYYYY too hot a motor without some serious gearing changes.
Keep an eye out on motor temps if you use them.

For most of us, a 35T Brushed motor (or equivalent) works well for speed & torque.

 

[Johnnysplits]

Re: Motor/3S Battery Question(s)

An external BEC is NOT to power the motor, it's to power the RX and/or steering servo to take the load off the ESC's internal BEC

Was this directed at me?

 

[Charlie-III]

Re: Motor/3S Battery Question(s)

I purchased a Speed Gems motor tonight and I noticed on their site that it's meant for 3.7-7.4v, I wanted to know if I could use a 11.1v battery provided I'd be running it through an external BEC.

Was this directed at me?

Nope.....at the quoted post if I understood his comment.

Yes, I should have done this in my original post.8)

 

[Johnnysplits]

Ahh ok

 

[Johnnysplits]

Yeah you can't run the motor off of a bec.

 

[KanchiX]

Re: Motor/3S Battery Question(s)

Nope.....at the quoted post if I understood his comment.

Yes, I should have done this in my original post.8)

Lmao, Yea I guess I wasn't very clear, I know the hh torquemaster has a built in BEC but when I told the guys at my lhs what servo I was running they recommended putting in the castle BEC regardless.

When it was the Timbuk2 system it glitched all the time because of the servo, but I never had a BEC installed on it. (that time will come)

For now I just wanted to try out larger cell sizes for the perfect balance of weight/power/speed.

TBH, I think I've got it all I need in this 35T Tekin... Maybe I'd go to 27T but not for awhile.

This baby leaps over my little rock wall in my front yard from a dead stop w/ the fronts touching the wall. The wall is 2ft wide and a foot and a half tall made up of various sizes not set in any particular pattern (rough going when you ride the spine)

I am 1000% pleased with this new ESC and the 35T motor I got.

So much fun, I'll post a link when I have a video.

 

[Johnnysplits]

What's the torque output of your servo?

 

[KanchiX]

What's the torque output of your servo?

277.7 oz.-inch

It's a Savox Super Speed Digital Metal Geared Servo pt.# SC-1267MG


AND... The car is glitching again.... With a Castle BEC. Guys at my lhs say my hh speed controller could be the problem but I wired everything perfectly. The guy at the shop inspected and agreed it's done correctly. I haven't checked HH's site yet for an FAQ, but that's my next stop. I love this little baby, I just want her to love me back! :mrgreen:

 

[KanchiX]

Guy at my lhs also said it could be related to my transmitter or receiver. Both are stock to the Wraith. (AX3 transmitter (or remote, what have you.) AR3 Receiver)

Could these parts already be worn or burnt out after 2 months of use? I had lots of glitching start as soon as I opened that receiver box to replace my first servo. (but that servo hasn't burned out yet. I swear I'm starting to think it's the servo doing this and the only way I can fix it is to buy the castle link or replace the servo for something more efficient.)

Any suggestions will be tested... as long as they're logical. Hahahahah, The last thing I need is someone telling me to throw it at a wall.

 

[KanchiX]

More info:
Servo specs-

• Torque: @7.4v - 277.7 oz-in / 21 kg-cm
• Speed: @7.4v - 0.09 sec/60°
• Voltage Range: 4.5v-7.4v
• Weight: 62g
• Motor: Coreless
• Gear: Steel
• Case: Aluminum Heatsink
• Output Shaft: 25T Spline (Futaba)
• Case Size (LxWxH): 40.3x20.2x37.2mm

And I just read this....
*NOTE: Certain combinations of receiver and ESC have been found to cause "Brown Out" issues when combined with Savox servos. An external BEC, or BEC stabilizing receiver capacitor may be needed for efficient, glitch free operation in low voltage electric applications.

GAAAAHH!!!!! :evil:

 

[Charlie-III]

Is the BEC direct to the servo or through the RX?
If direct, do you have the RX, servo & BEC grounds tied together? If not, do so. Some radios need all the grounds together.
If through the RX, what voltage is the BEC set for? STock is ~5 volts, sorta low for a Savox servo.

I would NOT recommend a "glitch buster" which is just a cap, BEC is a better route.8)

 

[GRIMGREG]

It could be a RX/TX issue, the Axial units have been known to have some glitches even brand new out of the box.

 

[KanchiX]

Is the BEC direct to the servo or through the RX?
If direct, do you have the RX, servo & BEC grounds tied together? If not, do so. Some radios need all the grounds together.
If through the RX, what voltage is the BEC set for? STock is ~5 volts, sorta low for a Savox servo.

I would NOT recommend a "glitch buster" which is just a cap, BEC is a better route.8)

I was wondering when you might chime in. I've found your answers helpful in other's posts. Gotta love that search feature.


It's indirect through the rx and the voltage is set to stock (must be the problem.) I guess it's time to crack it open again and install the castle link to set that amperage higher.

I knew this day would come, dangit. It was curious that one shop guy said he needed his friend (the other shop guy) to tune it. Especially when guy B said it didn't need it, then when I brought it in and told him it was browning out still he couldn't say why. Money making ploy? Bah, most likely assumed it came set to 10, I hope.:roll:

I turned down the strength (endpoint?) of my servo and it doesn't brown out but maybe twice per full battery... Is it safe to keep running it while I wait for the castle link to come in if its not in stock at my lhs?

 

[KanchiX]

It could be a RX/TX issue, the Axial units have been known to have some glitches even brand new out of the box.

I'm going to try upping the amperage on the BEC before I run out and buy a new RX/TX combo.... BUT, do you or anyone else have any recommendations??

A friend of mine got one that came with two RX's but I think that may have been a promo deal. I'd prefer something like that for a future winch project, but all will be considered!;-)

 

[Charlie-III]

I was wondering when you might chime in. I've found your answers helpful in other's posts. Gotta love that search feature.


It's indirect through the rx and the voltage is set to stock (must be the problem.) I guess it's time to crack it open again and install the castle link to set that amperage higher.

I knew this day would come, dangit. It was curious that one shop guy said he needed his friend (the other shop guy) to tune it. Especially when guy B said it didn't need it, then when I brought it in and told him it was browning out still he couldn't say why. Money making ploy? Bah, most likely assumed it came set to 10, I hope.:roll:

I turned down the strength (endpoint?) of my servo and it doesn't brown out but maybe twice per full battery... Is it safe to keep running it while I wait for the castle link to come in if its not in stock at my lhs?

You set the desired output voltage, not the amps (directly). I would set the BEC to 7VDC, maybe a little higher.
As to endpoints. you want the radio to stop driving the servo before mechanical things bind. When you bind up the servo, amp draw skyrockets.

I'm going to try upping the amperage on the BEC before I run out and buy a new RX/TX combo.... BUT, do you or anyone else have any recommendations??

A friend of mine got one that came with two RX's but I think that may have been a promo deal. I'd prefer something like that for a future winch project, but all will be considered!;-)

I would look for a 4 channel radio that has adjustable EPA's & trims for all channels.
If you ever want to run a MOA, then ESC mixing is really needed.

I recommend either a Futaba 4PL (does well for crawlers) or a hacked GT3B/GT3C (8 channels, lots of options, inexpensive with $8 RX's.)