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Big Torque Servos - ProModeler PDRS420BLHV 420oz Brushless servo!


Hey guys, one of the things we like to do here on GSN is find new products and let you guys know about them! I found this website and started reading and I have to admit, I like the owners no-nonsense straight forward approach to selling his product.

So after giving the website an eyeball these servos may just be the real deal and for just $79. As always we are just sharing the info, you guys make your own decisions have opinions! Besides, more options is never a bad thing!

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Nominal Voltage*: 6.0 - 7.4VDC
Operating Voltage: 5.5 - 8.4VDC
Torque: 380 - 420 oz-in
Speed: 0.14 - 0.12 sec/60°
Frequency: 1520µs/330Hz
Dead band: 2µs
Weight: 73.5g
Wire: JR/265mm

NOTE: deciphering the parts code - PDRS420BLHV means:
  • PDR = ProModeler
  • S =Servo
  • 420 = oz-in - torque
  • BL = brushless motor
  • HV = high voltage
*Nominal voltage - for a LiPo cell, it's 3.7V/cell (or 7.4V for a 2S pack). Yes, a 2S pack fresh off charge reaches 8.4V - but the voltage depresses nearly as soon as you load it. This is why we offer specs at nominal voltage. What this means in a practical sense are specs generated at real world voltages because inflating specs is a fool's game (and a matter of questionable ethics). Remember, the figures don't lie . . . but the liars figure!

NOTE: an o-ring seals between the splined output shaft bearing and the case, so the shaft protrudes a little bit less (by the thickness of the o-ring). To compensate, e.g. ensure there's adequate clearance between the bottom of the arm and servo case, when using metal servo arms, just sandwich the included lock washer between the arm and the top of the output shaft - then snug the bolt as usual.

The S420BLHV has been created expressly for competition pilots flying thousands of flights/year. Ideally suited to aileron, elevator, and rudder of giant scale models, e.g. 42% IMAC models. This servo centers beautifully, offers superb performance, and is the best we know how to make. In short, this is the top of the line ProModeler servo - no excuses.

Billet aluminum case - the entire case is CNC-machined from a solid billet of 6061-T6 aircraft-aluminum. End of story.

Heavy duty dual ball bearing supported output gear with CNC-machined case sections.

Gear train- all metal gears makes this servo strong. Material selection makes it tough. For an 800% increase in wearing surface hardness, we use exotic titanium-ceramic (TiCN) armoring for the 7075-T6 output gear (this is the exact same aluminum-alloy used in components of the upper receiver of an M-16 rifle). Intermediate gears are made of 4140 chrome-moly steel. The result is optimum strength and wear characteristics for high precision and long life.


- TiCN/7075-T6 output, 4140 chrome-moly steel intermediate, plus 7075-aluminum/4140-steel input-gear

O-rings - have you noticed how some really expensive servos don't have o-rings? The claim is electric models make them superfluous. Since getting caught in a pop-up rain shower isn't unheard of, and re-purposing servos into a nitro-powered model a year later happens all the time . . . do you buy that line of reasoning? We figure it's because the manufacturer pockets a few extra bucks - but leaving o-rings out comes at your expense because keeping water, fuel, and exhaust residue out of your servo is important. Wanna know why the S420BLHV is fully o-ringed? Simply because our engineers make these decisions instead of our accountant.


- Water resistant case features o-rings beneath the bearing, screw heads, and between case sections.

Nitty gritty - it's said the measure of a man is what he does when nobody is looking - take our servo's measure the same way. Ever disassemble a servo? They typically use four long-ass Phillips head screws, which come up from the bottom, sandwich the center section, and actually thread into the plastic top-case, right? However, an S420BLHV is built better. How? To begin, we use grade 12.9 Allen-head machine-thread bolts instead of el cheapo screws. Six come in from the top plus four more from the bottom, and instead of sandwiching the center case, the ten bolts actually thread into the aluminum. The result is a far more rigid assembly that's so much better . . . it's not even fair to compare!


Packaging - nestled within a high density foam insert for protection, each S420BLHV servo arrives packed in a jewel case. Since good looks never hurt, we laser-etch our logo into the polished aluminum case. These servo look great - think in terms of the fit and finish equal to, or better than, servos selling for more than $200. Bottom line? For the craftsmen who appreciates our high standards because we pay attention to the smallest detail, we hope you'll be as proud to install them in your model as we are to make them.

For more information: PROMODELER


I'd like to see a torque test.
Not sure if it's a true torque test but they out perform an 8711HV all across the board and are super quiet. Only down side for me is they have a Futaba spline. They are worth every penny and will be my go to from now on.
@SleepyC it's worth a note that the customer service rivals DA service!! They have been great servos and John beech has been great to deal with


Not sure if it's a true torque test but they out perform an 8711HV all across the board and are super quiet. Only down side for me is they have a Futaba spline. They are worth every penny and will be my go to from now on.
@SleepyC it's worth a note that the customer service rivals DA service!! They have been great servos and John beech has been great to deal with
Good to hear. Like I said, everyone has "their" brands, but it's good to see more enter the race, especially if people are saying they are a quality make!


Another guy posted something about these in the Radio forum, now those that know me know I'm a die hard ATX guy but after reading through numerous comment from guys praising these servos, my next bird is going to get a set.

The value, and the all aluminum case along with the amount of guys raving about the customer service sold me. :)
Yeah, these aren't a bad servo. Dad actually thought he had a bad servo for his tail rotor. I said he needs to have it hooked up to the gyro. He said that he didn't. So, I took my heli down there, unplugged my servo and plugged his in, and guess what............ It worked! So, I told him that and he said no way. Yeah way!

These servos have been out for a couple years now. They really seem like a good choice for a economical budget!


Just Do It
I would like to see and hear more positive reviews before I will switch from my Savox 1270's. I like the case construction but a lot more to a servo than it's cover.