Servo or ESC

[Jadd]

All the electronics on my SCX-10 are stock and only a few months old. I have taken it out for a few hours every weekend and a little during the week, so it has been used but I wouldnt say bashed. It's all been plastidipped, and was fine until last weekend. It got submerged a few times, now when I fire it up, the motor works just fine, but the steering servo wont make a sound at first, sometimes at all... I took the servo apart and put it all together, and it worked again. Not at first though, when it was all apart I tried working it and the gears would just spin...eventually it work normal and put it back together and ran it. Last night it wouldnt make a sound at all, I forced the wheels a little and it started working. This morning, I got nothing at all, there was a slight hum, and went dead... Should be the servo right? not the ESC correct?

 

[k7zpj]

You need to get a new servo and a BEC to power it. The stock servo isn't very strong and wouldn't be uncommon to have it fail after a bit of use.

I would recommend a Hitec HS7954SH. It is has plenty of torque for the SCX10 and is one of the somewhat lower cost options for a servo over 300oz of torque.

With any high torque servo you do need to have an external BEC.

 

[Jadd]

You need to get a new servo and a BEC to power it. The stock servo isn't very strong and wouldn't be uncommon to have it fail after a bit of use.

I would recommend a Hitec HS7954SH. It is has plenty of torque for the SCX10 and is one of the somewhat lower cost options for a servo over 300oz of torque.

With any high torque servo you do need to have an external BEC.

I have been looking into servos anyway, so buying a new one is fine, I kinda understand a BEC, but do I need one if my stock esc has one? I only run the stick batteries no lipo. But if I still need one any suggestions? Thanks!!

 

[Hardline]

The stock esc-bec has to power both the RX and servo. If the servo gets a little power greedy...say a steering stall...more is demanded from the bec than it can deliver and it underpowers the RX and you lose control. It's an intermittent thing, sometimes it never even happens to some people. So it may or may not be a must-have. But definitely a good idea to help keep the rig troublefree.

 

[k7zpj]

I have been looking into servos anyway, so buying a new one is fine, I kinda understand a BEC, but do I need one if my stock esc has one? I only run the stick batteries no lipo. But if I still need one any suggestions? Thanks!!

The BEC in the stock ESC only provides 1 amp of current. High torque servo need more than that. This post explains it.

http://www.rccrawler.com/forum/electronics/411201-yes-you-need-external-bec.html

 

[Epcampau]

Yes just allow you esc to run the rx and have a bec to run just your steering servo

 

[Jadd]

The stock esc-bec has to power both the RX and servo. If the servo gets a little power greedy...say a steering stall...more is demanded from the bec than it can deliver and it underpowers the RX and you lose control. It's an intermittent thing, sometimes it never even happens to some people. So it may or may not be a must-have. But definitely a good idea to help keep the rig troublefree.

I tried reading that thread about YES YOU NEED A BEC before, and tried reading it again tonight, there is so much b!tching back and forth I still cant get anything clear so I said screw it and just buy it. also in my shopping cart is the Hitec HS7954SH servo... I am wondering though, should I get/do I need the USB programming cable also? I've found all 3 of these things for $123 "out the door."
So cable or no? Ya know what though, I probably will... I have had this truck for a few months and maybe the first 2 weeks I had it, I didnt change something on it, or fiddle with it some how. Thanks guys!

 

[k7zpj]

I tried reading that thread about YES YOU NEED A BEC before, and tried reading it again tonight, there is so much b!tching back and forth I still cant get anything clear so I said screw it and just buy it. also in my shopping cart is the Hitec HS7954SH servo... I am wondering though, should I get/do I need the USB programming cable also? I've found all 3 of these things for $123 "out the door."
So cable or no? Ya know what though, I probably will... I have had this truck for a few months and maybe the first 2 weeks I had it, I didnt change something on it, or fiddle with it some how. Thanks guys!

The Castle Link is a good investment. It allows you to set the voltage on the BEC and it can be used to change settings on the stock Axial ESC.

 

[treys1]

Just to throw something out there. Should you have a little extra to put in, a Holmes Hobbies BRXL Has a BEC strong enough for 200-300oz servos.

I have run them in many scalers with ~200oz servos + winch + lights with no problems. I like it this way as the BRXL is an awesome ESC & it simplifies wiring.

 

[Hardline]

Holmes himself recommends an external bec with his BRXL on larger than stock servos. The CastleLink will not only program the bec, and obviously all the Castle esc's but also the Holmes BRXL and Axial AE series escs because Castle builds them for those guys.

 

[treys1]

Holmes himself recommends an external bec with his BRXL on larger than stock servos. The CastleLink will not only program the bec, and obviously all the Castle esc's but also the Holmes BRXL and Axial AE series escs because Castle builds them for those guys.

There are several posts on this forum where Holmes has stated his internal is good for 200-300oz servos.

I have run a BLS452 with a winch and lights with no problem in sever different scalers. Just saying it is possible.

Here's the most recent where he says 300+ its a good idea.

http://www.rccrawler.com/forum/holm...r-br-xl-big-brushed-power-63.html#post4445064

 

[Calderwood]

I tried reading that thread about YES YOU NEED A BEC before, and tried reading it again tonight, there is so much b!tching back and forth I still cant get anything clear so I said screw it and just buy it. also in my shopping cart is the Hitec HS7954SH servo... I am wondering though, should I get/do I need the USB programming cable also? I've found all 3 of these things for $123 "out the door."
So cable or no? Ya know what though, I probably will... I have had this truck for a few months and maybe the first 2 weeks I had it, I didnt change something on it, or fiddle with it some how. Thanks guys!

You don't mention which programmer you are looking at. You need the castle link since the bec comes preset to only 5.1v volts. You don't need the hitec programmer since it won't benefit your situation.

 

[Jadd]

The cable I was referring to was the Castle Link, but that leads to my next question, what should it be programmed to if I am running 7.2v 3000Mah NiMH batteries? 7.2? I dont get that part.

 

[mjc597]

The cable I was referring to was the Castle Link, but that leads to my next question, what should it be programmed to if I am running 7.2v 3000Mah NiMH batteries? 7.2? I dont get that part.

Look at the specifications oon the servo you bought..they should be posted on the website where you got It...there should be a spot telling you the torque specs and speed specs at specific voltages...usually has specs for 4.8v , 6.0v , and 7.4v , most of the high end hitec servos are rated for up to 7.4v so usually people will set the bec to 7.4v to get the most out of the servo...

 

[Jadd]

Look at the specifications oon the servo you bought..they should be posted on the website where you got It...there should be a spot telling you the torque specs and speed specs at specific voltages...usually has specs for 4.8v , 6.0v , and 7.4v , most of the high end hitec servos are rated for up to 7.4v so usually people will set the bec to 7.4v to get the most out of the servo...

Oh, it really is that simple. I tend to over think things I guess. You can lower the volts to save battery life at cost of torque then.

 

[Charlie-III]

The cable I was referring to was the Castle Link, but that leads to my next question, what should it be programmed to if I am running 7.2v 3000Mah NiMH batteries? 7.2? I don't get that part.

Look at the specifications on the servo you bought..they should be posted on the website where you got It...there should be a spot telling you the torque specs and speed specs at specific voltages...usually has specs for 4.8v , 6.0v , and 7.4v , most of the high end HiTec servos are rated for up to 7.4v so usually people will set the BEC to 7.4v to get the most out of the servo...

+1.

If you're running a NiMH pack (6 cell) or 2S LiPO, most HV (high voltage) servos can be powered direct off the battery, no need for a BEC although it's still nice.8)

 

[Hardline]

+1.

If you're running a NiMH pack (6 cell) or 2S LiPO, most HV (high voltage) servos can be powered direct off the battery, no need for a BEC although it's still nice.8)

Actually, I don't see much of an advantage. The bec can't add voltage. If your battery is at 7.2 and your bec is set to 7.4, the servo will only get the 7.2. As the battery drains, the servo voltage will follow it down, regardless of bec setting.

The bec will protect the servo from overvoltage (fully charged battery is higher than nominal), but the current HV Hitec line is "2S-rated" which means they're good to at least 8.4V. The 7954 is one of those.

So advantages of battery direct? One less electronix pkg to fail, to buy, less wiring, less packaging on rig, etc.

I think the advantages of an external bec vs battery-direct don't hit until you up the battery to 3S.