Help with Servo purchase please

[GodSpeed]

So if you've seen some of my posts you know that I know very little about this stuff. I'm rebuilding a Cadillac A-stamp I had as a kid which surely my dad built since I was about 6 years old.

All of your help so far has been fantastic and I really appreciate it. Choosing a servo, however, is proving to be quite frustrating and confusing. There's hundreds of them out there and I have yet to totally grasp the exact specifications I should be looking for. If you could help me with those, that would be great. Could you help me with the following?

The one parameter I'd like to keep within is not to spend more than $50. The reason I say that is I've sifted through dozens and dozens of pages of servos and it seems like really good specs can be had for less than that, even $25 range, or you can easily spend double or triple and I don't know why???

1. Brushed, brushless or coreless? What's the difference and what should I get?

2. Minimum torque spec to look for? (or a maximum as well?)

3. Minimum speed spec to look for? (again or a maximum...can it be too fast?)

4. Digital over analog seems to be logical

With those parameters, I should be able to sift through the choices much more quickly with greater focus. Are those the only parameters I really need to be concerned with? Right now my eyes glaze over because of all of the choices and I don't understand what to quickly eliminate.

THANKS!!!

[THEYTOOKMYTHUMB]

I've always found this one to be a great value, but Savox makes some good choices too. I've never used a Savox so I can't compare the 2. You should be able to get a more than suitable servo for under $30. 2wd 1/10 buggies don't really even need this much power, but it never hurts. I've never actually put this in a gold pan so I'd take a quick measurement to be sure. I can't imagine it not fitting though. Most servos are within mm of each other.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXUZ89&P=ML

[85Edinger]

I would go with a coreless servo. They're not that much more expensive than brushed but they're more reliable and perform better. Brushless servos IMO are too expensive. All my servos
are coreless, digital, and metal geared.

For an Rc10, anything with 100 oz in. or greater is more than adequate.

Speed really depends on your standards. If you're just bashing, it probably doesn't matter much. For me, it just needs to be under. 18 seconds or so, but I've been spoiled by my Hitec 7965mgwth .11 second transit time.

Most importantly, no matter what you choose, you must make sure that the.servo's.travel limit comes on or before the mechanical travel limit of the steering linkage. Otherwise the servo will try to turn farther than it physically can and burn out. This means that if your radio doesn't have end point adjust (or at least dual rate) you may need to physically limit your steering wheel's travel.

Edit: coreless beats brushed, but brushed should be fine for your needs.
I have two Solar D771's. They are superior to that Hitec 645 for less money. Unfortunately they are too big for an rc10.

[GodSpeed]

Thanks so far. More opinions and information always welcome.

THEYTOOKMYTHUMB, that servo seems pretty slow, doesn't it?

85Edinger, thanks for the torque spec. I often see it listed in kg/cm so that 100oz-in converts to 7.2kg-cm I believe. I'll look for that, thanks. That seems quite powerful in fact. I think I've been looking at (wasting my time looking at) much too small/weak servos.

So to summarize your advice so far, 100oz-in or 7.2kg-cm min torque, <0.18 speed @ 7.2v and coreless, digital. Gotcha.

I was wondering about travel limit in fact so I'm glad you mentioned it. That should be adjustable on my transmitter? I'm looking at ordering the FlySky GT3C.

[THEYTOOKMYTHUMB]

THEYTOOKMYTHUMB, that servo seems pretty slow, doesn't it?

Matches my reaction time...

I guess it depends on what you're doing with it. If you're just using it for general purpose I doubt you'll notice. If a servo is too fast you may find that it makes the buggy feel "twitchy". Then again, you know what they say about opinions...

[GodSpeed]

THEYTOOKMYTHUMB, that servo seems pretty slow, doesn't it?

I guess it depends on what you're doing with it. If you're just using it for general purpose I doubt you'll notice. If a servo is too fast you may find that it makes the buggy feel "twitchy".

Good point. Thanks.

[THEYTOOKMYTHUMB]

That radio can probably slow down a faster servo too though. I'm not familiar with all it's specs, but most radios with a few extra bells and whistles can, so a faster one may give you more adjustability.

[85Edinger]

For bashing around the 645 is plenty fast. I'm just a basher/ club racer who likes something a little faster. You'll probably like it.
And yes, that Flysky has EPA. Even dual rate would be adequate.
My GT-3b can't slow servos as far as I know and it's pretty much the same electronically as the 3c. However, fast servos can be slowed down by turning the wheel slower. For my Rc10 with the fast Hitec, I usually turn in and straighten gradually and save the servo's reserve speed for when I need it. It simply takes practice to not turn the wheel all the way immediately.

[bully]

I have several of these but the hobbico branded ones same servo though.. http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPHD3&P=7
I also have a bluebird 617DMG+HS which is cheap and available from hobbyking and seems fine for 1/10 truck or buggy,I have one in my racer oin and it has been very good for more than a year now.. Digital and metal gear is the only way to go now Imo,you have to watch some of the savox servo's they are very power hungry and require the use of a glitch buster..

[RC10th]

I would say anything metal gear around .10-.14 and 80oz+ is good, not too fast or slow and enough torque. I agree with coreless being the way to go without going crazy. Please stick to a name brand servo though as there is a difference in quality (smoothness, centering and holding power)

[GodSpeed]

Anyone try these Trackstar servos by Turnigy? http://hobbyking.com/hobbyking/store/__43052__TrackStar_TS_915_Digital_1_10_Touring_Car_Buggy_Steering_Servo_45g_10_1kg_0_08sec.html

The specs sound amazing and it's $36 bucks.

Digital, brushless, alloy case, titanium gear, N2 ball bearing, 10.1kg-cm and 0.08 speed @ 7.4V

[Sixtysixdeuce]

My $0.02........


I have played with A LOT of servos, all over the price spectrum, and ranging extremes in speed and power.

At this time, my preferences for 1/10 2WD steering servos are the Savox 1251 and the HD8305TG from Atomik. The Savox is smaller (short) and lighter, but also more expensive at ~$60. The Atomik is heavier and a little less powerful, but also faster and only $33 shipped.

Savox 1251MG:

Dimensions(mm): 40.8X20.2X25.4
Weight(g): 44.5
Speed(@4.8V sec/60): .10
Torque(@4.8V oz-in): 97.2
Speed(@6.0V sec/60): .09
Torque(@6.0V oz-in): 125.0
Gear: Metal
Bearing: 2BB
Case: Aluminum
25 Tooth Spline

Atomik HD8305TG:

Type: Standard
Operating Speed: 0.07 sec (4.8V) _ 0.06 sec (6.0V)
Stall Torque: (4.8V): 4.5 kg-cm (76.38 oz./in) | (6.0V): 5.5 kg-cm (62.49 oz./in)
Input: 4.8 - 6.0 volts
Length: 1.58 in (40.1mm)
Height: 1.42 in (36.1mm)
Width/Diameter: 0.79 in (20.1mm)
Weight: 57 g (2.01 oz.)

I really like that Atomik unit as a throttle/brake servo on my 1/8 scales, too. So quick, they respond like a brushless.

If you have exponential adjustment on your TX, you can always make a fast servo slower, but you can't make a slow servo faster.