AJ Models 62in Acuity servos

by | |
Selecting the best mini servos for the AJ Models 62 inch Acuity

As usual, one of these articles begins with a customer but this time, I initiated the conversation when I noticed a fellow bought a set of DS160CLHV servos and, realizing he was a new customer, out of curiosity reached out regarding for which model they were intended. He responded he was building an AJ Models Acutity (the 62” version).

For those in the know, this is a smaller version of the airplane with which Andrew Jesky won the Nats in 2016, the Element. And these days, his company, AJ Models, offers both this 62” version, and a full on 2m bird suitable for pattern and IMAC competition, also.

Anyway, reason I know all this is because of a couple of customers, Nick and Jeff Ziegler, and a story I told a few years back titled, Brotherly Love - clicking this link takes you to a nice story of an Acuity and these two brothers from Moline, IL.

That, and I own a Jesky-designed model, a 126” Slick. This, a 3D Hobby Shop product as campaigned for years by SupaTim (once of Northwest RC, but these days better know as the GM of Extreme Flight and Skyline Models).

And allowing me a brief birdwalk, this YouTube video (1-minute only) is of SupaTim having a blast with his 126" Slick model at an event (one like mine but flown like I can't).

It is from many years ago, but even then, Tim showed himself to be a very talented pilot. As for me? I count myself fortunate for owning an example of this fine Jesky-designed aircraft.

And of course, that Andrew is a talented designer goes without saying . . . but there, I just said it, anyway! Point being, the guy’s seriously good! And not born that way, but instead the direct results of loads of hard work and effort.

So his stock in trade these days is an enormous range of self-designed model aircraft. And he offers them to the market (that would be you, and me) at very affordable prices - each a delight to fly.

And note; there's absolutely nothing in it for me to say this because I only know the man through his work product. Meaning, I've never so much met him and thus, my recommending him and his company doesn't buy me a cup of coffee in terms of any conceivable benefit.

So I'm telling you out of honest admiration for what results when you work hard and play hard in America. The greatest country under God's grace!

Anyway, click this link to AJ models (his website). I share it because I feel it's worth a visit for if you've maybe fallen in a rut and didn't realize the wealth of designs he offers modelers like us. His slogan of . . .

Up your game. Fly AJ Aircraft.

. . . really resonates. And note, as usual, clicking a link doesn't mean losing your place here because it opens within a new browser tab.

Anyway, back when Nick equipped his model, he used our DS160CLHV - the same servos my new customer ordered for his. And back then, the DS160 was one of three minis in our lineup, and our most powerful CL mini-class offering.

These days we're up to seven minis, and the DS160 is just middle of the range torque-wise. So it occurs to me, a few photos regarding an Acuity-build might be in order. Especially if accompanied by a few thoughts regarding what other ProModeler servos from our expanded lineup you might select, instead.

Basically, I am going to present a few different thoughts for your consideration because these days, we offer five suitable minis for the Acuity.

Note; I'm leaving out the DS110CLHV and DS335CLHV - we'll touch on them lightly but principally I'm yak about these five in no particular order.

  • DS210CLHV
  • DS160CLHV
  • DS205BLHV
  • DS355CLHV (low profile)
  • DS405BLHV


While the DS160CLHV remains in the lineup (as well as the DS110CLHV), these servos have been joined by 3rd servo in the CL-series, the DS210CLHV.

Beyond a different motor allowing us to offer significantly more torque (whilst maintaining these servos signature superior speed), we did a few things in bringing the DS210 to market.

One is we totally redesigned the upper polymer case. This let us add a tiny bit more glass-filled Nylon material. Why? The extra material is around the output shaft bearing expressly helping it better withstand the added torque the DS210 brings to the game.

That, and we switched from all-metal gears to all-steel gears - and this is a really big deal.

- Before and after switch; from all-metal to all-steel gears

Previously, our CL-series minis used gear materials including steel pinions, brass bulls, and the final output gear made of 7075-T6 aircraft aluminum to which a wear coating (hard anodizing) was applied. While a very good set of materials, loaded above a certain point they wouldn’t hold up as well as we’d like.

What point? Some really aggressive XA-types could actually break them in the air! Especially aileron servos whilst performing rifle rolls at top speed (basically sticking a huge honking control surface out in the breeze) and brrrrp, they'd strip.

In my defense, I never saw maneuvers like the rifle rolls and walls coming down the pike back when I first designed this servo (so it's woulda, coulda, shoulda only if I could have foreseen the future).

Anyway, the all-steel gear train brings to an end the possibility of stripping gears in flight because these things are strong! And note, this never manifested with the DS110 because it didn't have the torque of the DS160. Point being, things would have been *worse* with the DS210, hence the updated design!

Recapping; along with the new motor for adding the DS210 to the lineup, and beefing up the case, we switched gear materials to all-steel. While all-steel is technically all-metal, the facts are steel is a much stronger metal than the others (witness Ferrari and NASCAR whose transmissions use all-steel gears).

End result, these new gears hold up to anything you can throw at them (in the air, ground encounters don’t count). And the best part? Well, because we’ve grown our share of the market, then our buying power has increased, also. How much? To the point we can now, perhaps not dictate terms to suppliers, but at least meet them on a more level playing field. This means, we upgraded the DS110 and DS160 servos, *and* were able to hold the line on the price. So win-win!

Anyway, it's my opinion the DS110CLHV is a bit light for an Acuity unless you are completely into 'smooth'. Or if you're using a gyro where the incredible speed is a marked advantage. But gyros are disallowed in competition, thus making the DS160CLHV the better choice.

But the DS210CLHV is clearly a better servo for an Acuity *if* you tend to horse around with it, e.g. fly it HARD. That said, if smooth is your forte, instead, then the 30% extra torque is something you'd only feel in your wallet.

Remember, the answer to which is the best servo is . . . it depends!

Of course, the real reason for doing the all-steel gear train for the DS210 was we either used stronger gears else it wouldn’t live. Hobson's choice! And we knew this because we have long been using all-steel gears with our more costly DS205BLHV where the gears have lived fine with *any* 60-class model no matter what maneuvers were thrown at them.

And this brings up the question, why a 210oz-in *and* a 205oz-in mini-class servo? We’re glad you asked!


It’s down to motors. And for this we need to take a quick detour into what our model numbers mean because you don’t need a decoder ring to break the code. It’s actually simple and straightforward and means something in plain English, because . . .

  • DS = Digital Servo
  • xxxx = rated torque in oz-in
  • CL = Coreless motor (BL = brushless)
  • HV = High Voltage (to 8.4V)

So the DS210CLHV and the DS205BLHV are making similar torque and speed (or so nearly the same you couldn’t tell when mounted within model if your very soul depended on it).

Note; speaking about motors, if you don’t know diddly about servo-motors, then we can help you learn more. Review this . . .

. . . and after you truly grok the contents, you’ll be your club’s expert whenever someone wonders about the difference in servos. trust me, few modelers understand this stuff and you will.

This, because we take the various types of servo motors, which all servo manufacturers use (iron core, coreless, and brushless) and using the lathe, slice them open and photograph the guts. Then we explain - with detailed CU photos - what’s what, and why. Here's an example;

So could the DS205BLHV be a better servo for you versus the DS210CLHV even if speed and torque are virtually indiscernibly the same? Yes, *if* you practice a lot. No question.

Let me explain, I was tucked under wing and taught to fly by Bill Norman who ran Homewood Toy & Hobby on the south side of Birmingham and Bill was a pattern maven. So beginning in 1972, after work we'd leave for the field at Grayson Valley arriving just in time to get in three flights (sometimes four), then clean up, pack up, and head for home (always arriving after dark).

We did this three days a week plus Saturday and Sunday for years. Point being, if you fly a LOT then the brushless motor servos really pay off because they last 5X longer and with no brush dust to accumulate inside the motor, results in less heat buildup and a near indefinite service life.

There's a reason top modelers say brushless servos are worth a few extra bucks, trust me.


This mini may well be our very best offering for this class of model for all but the dedicated competition level pilots who fly a lot (hundreds of flights a year of practice plus 12-20 weekend events on the circuit, plus the Nats). To thine own self be true said the bard (Shakespeare) and this means, don't pony up for pricey brushless servos unless you need to depend on the servos for years and year of hard use. Otherwise, save money and use coreless servos, instead. Straight up!

And note; the DS160 isn't our most expensive mini-class servo - middle of the road price-wise. Comes with a CNC-machined alloy center case (begins as a solid billet of 6061-T6). And you get cooling fins to help when it's working hard by shedding heat better than smooth side alloy servos, do.

- Hogged from a solid billet of 6061-T6 aircraft aluminum, note the cooling fins!

You also get reinforcements within the polymer with Swiss turned bronze which are insert molded expressly to better anchor the steel gear shafts of the transmission section. These are the kind of details that deliver solid value. And especially important when you don't want to torch your wallet.

Think of the DS160CLHV as our best all-arounder

- Bronze hardpoints mean more precision because the bores don't wear like plastic ones


The DS205BLHV exists because it’s a more durable product. This once also meant the gears were more robust because they are all-steel, but now that the CL-series have all-steel gears, too, there still remain two principal advantages, which you many pilots feel make them worth the extra dough.

One of the tremendous advantages lays in the alloy case. This, we hog from a solid billet of 6061-T6 aircraft aluminum. It, quite simply, is a much stronger case than polymer. You won't notice for years (maybe never), but the greater rigidity helps. Basically means it delivers a longer service life. Especially under stressful conditions like XA-maneuvers.

That, and the second advantage the BL have versus the CL-series is as we've discussed, the brushless motor. As you know, runs cooler and lasts 5X longer. Or put another way, you get more bang for your buck!

Strange as it seems to say about a more costly product, this are important considerations even if your money doesn't grow on trees, agreed?

- DS160CLHV set up for pull rudder


Next up we offer the DS355CLHV, another super mini built within an alloy case. But unlike the others, this one is low-profile, and one which is astonishing for offering a stupefying 355oz-in of torque.

Look, unless you’re new to the sport, then you surely realize just a few years back, 350oz-in was the domain of standard class servos (like the Hitec HS-7955TH). To obtain that from a mini is nearly inconceivable! Yet deliver it does and if you fly stupid hard (and if weight is important) or if you need the low-profile (the Acuity doesn't), then consider this DS355CLHV servos as the best ones for you.

- Under stab mounted elevator servos provide you a short and direct linkage

ProTip: Of course, there’s no substitute for the sheer size of the gear face when it comes to withstanding vibration (so if you’re looking for servos powered by high vibration engine, say a single-cylinder gasser engine) then a standard size servo cannot really be substituted for by a mini. This is a case where bigger (gears) is better. So don’t be dumb, capisci? We offer the the DS415BLHV in the alternative where standard class servos work for you model.

Examples of users specifying this DS355CLHV low-profile super-mini include Bret Becker. If you're unaware, he quite notably used ProModeler servos throughout his model. Specifically, a set of DS355CLHV to drive the flaps of his self-designed molded carbon fiber (and Top Gun event overall wining) reproduction of the Lockheed U-2.

- Tucked away, discretely hidden the DS355CLHV in  Dr. Bbecker's U-2 model

And as an aside, because there were a few scale modelers who espoused sour grapes at his using an EDF powered model instead of a turbine, he made monkeys of them by winning the title of Mr. Top Gun with his U-2 . . . two years running!

Major point being, Dr. Becker very intelligently used what we offered in a low-profile super mini to build a championship caliber model. We're honored to have played a small role.

- Just look at the hardware accorded the man who wins all the marbles!


Bottom line? If you pick your battles, then you can definitely use a super mini in models, which might surprise you. An example it this highly experienced fellow out in California. Look what he did with an 85” Extreme Flight Extra.

Would you ordinarily believe this would be a candidate for mini-class servos?

Yet he built an ultralight-weight weapon with which to campaign by thoughtfully equipping it with our super-minis. How? Simple, by being smart like instead of a 50cc single cylinder gasser like many would spec (basically, a paint shaker), he opted for a 12S electric setup, a really smooth and near vibration free motive source.

Next, figuring he could shave quite a few grams by substituting our low profile DS355 super mini for standard-class 350oz-in servos (pros know grams add up to ounces), he exhibited the kind of subtle genius you see in pilots with many years under their belt (recall the joke about old-bull and young-bull on a hilltop surveying the field with many heifers to grok what I mean about gray beards like Baker).

So just as long as you’re not stupid, this kind of thing (substituting a mini for a standard) can be made to work to great advantage. But use your head, eh? Remember the point about paint shakers inducing greater gear wear based on the smaller size of the mini-class gear face.

Anyway, added to which, even if you don't have a specific use for a +350oz-in mini with an Acuity, some guys buy their servos with other models in the back of their mind. Basically, ponying up for the DS355CLHV super mini might make perfect sense in an Acuity today, and something else tomorrow. This fact alone may make them the best mini-class servo for you! As usual, it depends.

ProTip: What made using minis in Baker's model easy is a little mount adapter we make called an M2S (mini-2-standard). Weighing but a few grams each, you merely install the 6061-T6 alloy mounting plates into your model (wherever a standard size servo is fitted). Next, you install our mini-class super servos in place of standard class servos. And just like that, Bob’s your uncle!

Put another way, if you’re the type who can think outside the box, then maybe we can help you advance into areas of modeling you may have never considered before while using the same set of servos - like maybe after a moment of brain fade resulting in a crash makes your servos available for something new!


But we don’t stop at 355oz-in. This, because of the wonders of the ever more powerful magnets afford us by developers of rare earth minerals like neodymium. So we also offer you a DS405BLHV. Once again a brushless motor, and this one is a skosh more than 400oz, and packed within a mini-class case . . . yee-haw!

Smooth, fast, powerful, and weighing significantly less than standard class servos in this torque range, the DS405 is something of a first. Will others catch up, especially outfits in Asia with government money backing them? Yes, as surely as God made little green apples they will. But what I predict they won’t do as well is build them to our standards of quality.

Part of what makes your ProModeler servos better than competitors is that unlike hobby-grade servos, they're built to meet military standards (and subjected to these tests).

MIL-STD-810G-Part 16

  • Shock - Test Method 516.6
  • Vibration - Test Method 514.6
  • Rain - Test Method 514.5

In part, this is due to the requirements of our primary customer. However, because we're modelers and have knocked a servo off a workbench, experienced crashes, and know a thing or two about engine vibration (plus how a summer afternoon pop-up rain shower may drench a model before landing), it means these tests are important for civilian users as well. So if you're looking at another servo, one which offers similar performance and pricing, but hasn't been tested to military standards, which would you rather have?

Added to which, I suspect competitors who are guided by accountants and businessmen instead of engineers, will cheap out. Like instead of the world’s best potentiometer, the Japanese Nobel 1mc, maybe they’ll resort to a clone because it’ll be cheaper.

Facts are the clones look the same, and even perform the same (but only for a little while). We know because we've tested to failure under harsh conditions of shock and vibration. We don't use the 1mc just to spend more money, it's better!

So because the clones only cost about 25% of much as the genuine item, I suspect plenty who claim 1M cycles are lying. Us? While we resist the siren's song of lower cost by using the real thing, when it comes to vendors specializing in badge-engineering (like their engineering input amounts to sending an art file to be placed on someone else's servo), do you really wanna bet they'll use the good stuff like we do? Just an observation, OK?

For example, maybe they’ll turn to using el cheapo Hall Effect sensors, instead to save money. They'll try to fool you with how they're better by preaching technical gobblygook. And it’s true, they are very good sensors, every bit as good as the 1mc . . . until they’re not. But what they're really better at is saving money because they're dirt cheap. I mean at most costing just 10% of what the 1mc goes for.

But here's the rub (and the part they don't speak out loud). Part of why you pay us the big bucks is for doing something for you you may not even realize is a big deal. Making a better engineering decision involves factors like how something fails, which is actually more important than when it takes a crap.

This matters. Learn more about pots if you’re curious by reviewing this;


ProModeler offer you several mini-class servos. What’s in it for you? Getting the exact same product our G&I customers buy, and at a price vs. performance point well suited for your needs (and without torching your wallet).

Potential ProModeler minis you may choose include these arranged in order of increasing price;

  • DS110CLHV
  • DS160CLHV
  • DS210CLHV
  • DS205BLHV
  • DS355CLHV (low profile)
  • DS405BLHV

. . . and there’s one missing, the DS335CLHV-180° - yes, a 7th super mini exists! But this one is quite special in a way that rules its use out for the Acuity build because it transits 180° instead of 90°. Thus, this low profile 180° super mini exists to solve mechanical problems like sliding a canopy, or compact servo-operated miniature retractable landing gears, plus a host of specialized robotics applications not applicable to the Acuity.

In short (pun intended) this low-profile puppy is perfect for those of you who need a mini with an expanded range of travel. We mention it just to plant a seed in the back of your brain, not because you'll need it for your Acuity.

- A low profile super mini, the DS335CLHV transits 180° instead of 90°

What else? Well, if your experience with mini class servos include alternative products like the generally well regarded and popular Hitec HS-7245MH, which on their website they describe in part as . . .


  • Our Best High Speed Mini Servo
  • Efficient Coreless Motor
  • Heavy Duty Metal Gear Train
  • Dual Ball Bearing

. . . then you’re in for a revelation with ProModeler mini class servos. Why?

For starters our lightest duty mini, the DS110CLHV spanks theirs in terms of performance by giving you 110oz-in vs. 89oz-in (or 20% more torque) and in terms of speed, 0.035sec/60° vs. 0.11 sec/60°, meaning ours trounces their in terms of transit speed, also. You get a mini servo that’s more than 300% faster, too.

But there’s more because at the time of this writing, on Amazon theirs goes for $76.99 so we spank them on price also! You're just getting more servo for your money with ProModeler.

Of course, this is partly because of our efficient customer direct business model, but also because we’re willing to settle for less money-wise in order to gain market share. This was once known as an old fashioned price war! And you win because of it. We do too, so once again win-win!

What else? When it comes to powering your servos, an old school battery pack or an ESC might be risky. You need to bring your thinking into the present and begin to think beyond voltage and think in terms of current flow. What do we mean? Simple . . . read the specs and use your brain. This means assess what the specs are *really* saying and what it means to you and your model.

Power to the people

For example, every single ProModeler servo gives detailed specification. And not just child’s level torque and speed, but by delving deep and presenting really detailed specifications. Ones broken down into five voltage ranges.

So if you look, you’ll see the performance of our servos is detailed at 5V, 6V, 6.6V, 7.4V, and 8.4V. These correspond to a 4-cell NiCd/NiMH and 5-cell NiCds/NiMH). Yes, old school chemistry but still favored by some.

The 6.6V is for the users who favor easy to live with A123 type battery packs (LFP, LiFePO4, or Lithium-Iron-Phosphate).

Meanwhile 7.4V is the domain of LiIon packs while 8.4V is for fresh off charge LiPo or synthetic derived sources like BEC (Battery Eliminator Circuits). What’s the IMPORTANT number?

Current, denoted in Amperage, or abbreviated A.

And take note, performance varies based on voltage. This is not a brand thing, it's down to physics. Maybe you like 6.6V of the A123 packs because they're easier to live with (I do, I prefer flat out them). Thing is, at 6.6V the DS205 is delivering about 173oz-in instead of 205oz-in. So you need to *think* about these things, also, when selecting the best servo for you and your model. You can't play checkers, you need to think around corners and play chess. Don't be like rookies who focus on just torque at max voltage without consideration for which chemistry they prefer using!

Major point being, if you eyeball the current draw when stalled (meaning the exact point when the servo is delivering rated power), for the DS205 it’s nearly 3.5A at 8.4V. Multiply that times how many servos in the model, and bearing in mind what engineers think of most (the worst case scenario), then it becomes bloody obvious a battery pack with a single 3.5A power lead won’t cut it. In truth, the freebie BEC built into most 6S ESC probably won't either. Just saying, OK?

Look, it's a hobby, not your job. You can take the time before deciding to learn more by reviewing these brief articles.

Is this a lot to read? Yes, but what's your alternative? A forum where you may actually be interacting with some 12 y/o, or maybe a keyboard warrior with thousands of posts in his history but who is merely rehashing old wives tales?

Anyway, and succinctly, each power lead (DuPont connector whether branded JR, Futaba, Spektrum, or the Universal we use) is rated at 3.5A continuous. As it happens, deciding to use a battery pack with a single lead is a questionable decision regardless of what you’ve always heard or done.

Not trying to scare you, just want you to ponder long and hard what the risks are of doing things the way it's always been done. We're in a new world when minis make well north of 200oz-in, and even more so with +400oz-in.

Remember, torque and speed doesn't materialize out of thin air. It takes current to make things move. The days of servos that consumed a few hundred milliamps are history! Word to the wise.

Also, please remember, we live in a litigious society and despite AMA insurance of $250,000, you’re going to be on the hook financially for far more than you can imagine if you ever find yourself in a courtroom nervously sipping from a glass of lukewarm water whilst swallowing hard and sitting in the witness box while serious questions are barked at you by a lawyer. Like, 'Sir, what were you 'thinking' when you supplied insufficient current for your model’s avionics?'

This, because despite your best efforts, you miscalculated a maneuver and stuffed your model through someone’s windshield thereby killing their wife - added to which, you're also going to be personally devastated because said woman, minding her own business crocheting a baby blanket for her granddaughter, a) didn't deserve it, and b) you didn't mean to do it, either, and c) she was your best friend's wife! Could be a seriously heavy emotional load - take my meaning?

After all, we’re flying models, and while some may view them as just toys for big boys, any in no way are they less lethal at 6lbs @ 88fps (60mph) when possessed of far *more* kinetic energy than a .45 caliber bullet (115 grains, or 0.26 oz) traveling at 800fps . . . understand?

Current consumption (amp draw) is serious stuff so use your head because we’re not kids playing with toys regardless of how some may look at it.

Major point being, these super mini servos may be small size-wise, but their current demands aren’t any less than a similar performing standard class servo. And this is 100% true as well for our better quality competitor's, like the very nice MKS HV747 (208oz-in) . . . so high current demand is not just an issue with ProModeler, but with all high performance minis - it's physics, not opinion!

So measures like using built-in BECs, which work fine for toy-like foamy ARFs equipped with cheapo servos won't necessarily be best practice when dealing with high performance models of the caliber of these by AJ, Extreme Flight, and OMP - not when equipped with high performance servos, understand? You must have your head fully engaged!

Anyway, we offer a standalone BEC by Castle that has two power leads instead of one. It’ll do the job (delivering more than the 3.5A a single lead is rated for) if you have a phobia against maintaining a dedicated battery pack for your model. And remember, it doesn't matter if the BEC is rated for 8A if the connection for delivering that current only flows through a 3.5A connector! You must have two of these to get enough current for this type of model equipped with high performance servos.

Note; if you’re fine with a dedicated avionics battery, we offer them ranging from 650-6000mAh, each with four leads. Four?

Yes, four leads because these packs have a pair of DuPont connectors, each capable of delivering 3.5A to your receiver simultaneously, so 7A without heat build up (continuously, and in our opinion, this is enough).

There’s also a balance connector (for the charger to monitor the state of charge of each cell as it does it’s thing). Plus an XT30 (rated at 30A) via a 16AWG lead, which is actually what we use for charge/discharge purposes to minimize wear and tear on the DuPont connectors.

These all share silicone jacketing material, the soft supple stuff that is so flexible and resists abrasion. Basically, the best packs money can buy.

Anyway, when it comes to powering your control subsystem, it would sure be a shame to pony up for the best of the best model airplane-wise, ditto motor, ESC, servos, etc. and then take a shortcut in the power department because nobody told you about modern day servo current requirements. Consider yourself informed. Heads up, eh?

Any further questions, suggestion for this article, etc. then just reach out to me at 407-302-3361, or via email: info@promodeler.com

This entry was posted in .