Kraton Kraton 4S servo recommendation?

[Linchpind]

I'd like to upgrade the servo on my Kraton 4S. The servo is fine, but I want some thing much faster and more torque.
I think the stock one is rated at 15KG and .14 on speed. Is there anything that is faster? I seem to see a lot of servos with torque, but not a lot of speed.
I already have a new radio that I want to install and thought I would change the servo out while I got it apart.

 

[WoodiE]

@Linchpind take a look at the thread, Recommended Arrma 4x4 Mega Upgrades

 

[Linchpind]

Thank you for the link, but I'm a bit confused. I'm still trying to wrap my head around how servos are rated and what would be an actual upgrade...
The stock servo is a ADS-15M. 15KG (is this the weight??) 208oz(torque/strength??) and .14 on speed.

Forgive me, but I don't know what all this is and to add to more confusion, some servos that I have looked at, they list the specs of the servos at 4.7v and different specs for the servo at 6v. Is the Kraton 4S a 4.7volt or 6volt vehicle? I'm using a 4S battery.

I'm assuming the higher the oz number, the stronger the servo is and the lower the speed, the faster it turns?

I looked at all three servos listed on the top post of the message thread you listed. The first servo linked is the Savox SW-0230MG with the specs listed as .13/111.1 I would assume that this is faster than the stock ADS-15KM but weaker in strength?? So it looks like it turns faster but is weaker and this would not be an upgrade for me?

The second servo listed is the Savox SW1211SG .10/208.3. Am I correct in thinking that this is turning faster than my stock servo and about the same strength.

My head is spinning....all I want to do is to turn faster and have a little more strength to turn the wheels. Metal gears would be nice. I just cant figure this out and I appreciate any help you could give me.

The last servo they reccomend BEC?? it looks like a servo lead with capacitors in it??

 

[Pat_ranch]

These work just fine, and they're cheap.

https://www.ebay.com/p/10034936054

 

[Arrmature]

All servos come with two properties specified; torque and speed. Some manufacturers also specify stall current which I personally think is very important to know, but most won't tell you.

Torque is measured in either kg-cm or oz-in and is a measure of how hard the servo can push before it stalls. 15 km-cm is the same as 208 oz-in. The higher the number the stronger the servo can push. Torque also increases with voltage - your ESC supplies 6V so focus on 6V specs.

Speed is measured as the time to sweep through 60 degrees of rotation with no load. It's almost meaningless. As soon as you load a servo, it will sweep more slowly. Generally servos with more torque won't be slowed down as much under a given load.

There is a tradeoff between torque and speed. The torque/speed relationship is determined by the strength of the servo motor and the gear train in the servo. For a given servo motor, more torque results in a slower servo and vice versa.

Then there is the difference between analog servos (which Arrma uses) and digital servos. Digital servos respond to small inputs much better and will change directions much more quickly than analog servos. If you have an analog and a digital servo with the same speed rating (say .15s per 60 degrees), most will find the digital servo more responsive or "faster". The only downside to digital servos is that they are noisy - even when sitting still they are constantly chattering. They also draw a bit more power, but that's a moot point when you look at what the ESC and motor are consuming.

Your last question was about the BEC. A BEC is essentially a voltage regulator that takes power from the battery and outputs a nice clean stable voltage - typically 6V. Your ESC has a built in BEC that outputs 6V at 3A continuous and 6A peak. This where the stall current comes into play. If you look at the last two Savox servos in the recommended replacements thread, you'll find that the stall currents are 6A for the 1211 and 5A for the 1256. If either of these servos were to stall due to the steering getting jammed, the servos will draw 5 or 6 amps until you shut it off. You run the risk of burning out the BEC built in to the ESC, so an external BEC is sometimes used. Hobbywing makes external BECs capable of delivering 8A continuous or even 10 A, but they tend to interfere with the radio if you're not careful with placement.

I just replaced my servos and went with 20 km-cm Power HD servos. At 6V they produce 18 kg-cm of torque and they are fast enough for my needs despite the speed rating being a bit slow. What I really like about them is that the stall current is around 5 amps, but after a couple of seconds, the servo gives up and stops pushing so hard, dropping the current to about 2.5 amps so I can skip an external BEC.

The Annimos servos sold on Amazon are a popular choice here. They are cheap and so low risk. There are some videos on Youtube where these servos have been tested for torque and stall current. Stall current won't be an issue as they don't draw more than 3 A when stalled.

 

[Linchpind]

Thank you very much for taking the time to explain this to me. I really appreciate it! Now I can make sense of what Im looking at!

 

[Knxwledge]

How much are you willing to spend? I think that’ll help a lot with suggestions. They range from $20 to $150+

 

[Arrmature]

Another thing you should be aware of is that the stock servo is rated at 15 km-cm and .14 s/60 degrees at 7.2 V. At 6.0 V, the ratings drop to 14 km-cm and .16 s/60 degrees.

 

[Linchpind]

Id be willing to spend around 35-60ish for something digital. Looking for speed, but it sounds like anything digital with a lot of torque will be better than the stock servo. I just bought some dBoots Backflips that seem to be slightly larger than the stock wheels and tires. The track that I ran the car at has a lot of sharp turns. I find myself slowing down a bit more than I should to make the turns. I sldo have a new flysky radio that I want to swap in as I don't care for the stock one.

 

[Knxwledge]

Im using this one and I love the torque and speed it offers. Way faster than the stock servo.


JX BLS-HV7132MG 32KG

https://m.aliexpress.com/item/40009...er_id=8604c00586754b6da73a719bb2080a6e&is_c=Y