Futaba HPS-A703 versus ProModeler DS930BLHV

A servo matchUP (comparison article) comes about from time to time and nearly always in response to a question regarding a specific servo like; I’ve been using Hitec D645MW servos for years but a buddy said I should look at ProModeler, so what have you got to compare, and what recommends them?, or words to that effect.

The answer to the above is a ProModeler DS180DLHV and because we don’t hide from these questions, we buy a competing servo, take it apart and show what’s what using side-by-side photos. This, so you can suss out which side of the bread is buttered for yourself, because nobody likes being told what to do. Note this example.

This brings us to this matchUP, which comes about in a unique fashion because a potential customer isn’t just inquiring about a Futaba HPS-A703 but is also describing a problem when using them with a Jeti Central Box 310, all whilst asking not only what we’ve got to compare, ‘but’ if he can expect the same issue with ours.

Thing is, the answer involves a 3rd party’s product, and sensing a cow patty in which I don’t want to step, strange doesn’t begin to describe a feeling akin to being asked if I’m still beating my wife!

Unfortunately, an honest response is unlikely to win friends and influence people (e.g. persuade him to buy our servos). More likely, my response alienates him (and in making him unhappy, it means he won’t buy our servos). I really hate can’t win situations – sigh.

Unfortunately, I’m not wired to shy away from controversy, so because he asked, he’s going to learn what I think. You will, too.

Note; this article runs a bit longer than usual because an investment in such expensive servos deserves our best effort at guiding you. If you’d rather not clutter your brain, the Page Down key is your friend.

Futaba A703 vs ProModeler DS930BLHV

Q1. I was hoping you may be able to help. A friend of mine (Steve Astlund) recommended your servos since he has had good luck with them in his IMAC planes. I am putting together a 40% Edge 116” and just purchased (8) Futaba A703’s. I am also switching over from Futaba to Jeti and trying to use their Central Box 310. I have been having an issue of the servos locking up after I put them through some motions. I think it has to do with the servos not liking the BEC within the Central Box. 

I may end up changing out all the servos with something that has no compatibility issues with the Jeti Central Box. What servos within your lineup would you recommend, or would yours potentially have the same issue?

A1. We’re looking at two distinct questions, but first, we’re gratified whenever word of mouth sees someone wash up our shore, please extend our thanks to your friend, Steve.

In reverse order, there have been no reported problems with ProModeler servos and Jeti Control Box 310, so let’s get that out of the way from the get go. Nor have there been reported issues with PowerBox, AR, or any alternative power distribution systems.

So I suspect Futaba HPS-A703 specs (below) warning against BEC-use is why you bring up BECs when asking if you’ll experience the same issue with ours (graphic from Futaba’s website shared as fair use).

So here’s the thing, like Futaba, we also advise against BECs but from our perspective, it’s because of model truck customers. Talking about guys with toy-grade ESC/BEC combos (note their mention of dry cells, also leading me to suspect this is true for Futaba, also).

Really saying (and talking myself out of a potential sale), I don’t think Futaba are to blame for what you’re experiencing. Speaking of which, what did Futaba say when you asked them? And what do the folks at Jeti have to say? Like could your Central Box 310 be defective?

Wondering because we have tons of folks using Jeti power distribution systems with our servos (and likely, so do Futaba). But back to your Central Box 310 issue, if I had it on the workbench connected to an oscilloscope, maybe I could offer more insight.

Meanwhile, and in defense of my competitor, consider this; the HPS-A703 is Futaba’s top of the range standard class servo (and it’s not in me to toss my competitor under the bus to try and gain advantage because we can beat them fair and square). Point being, I don’t think there’s any issue with your HPS-A703 servos and instead, if I were you, I’d seek elsewhere for the root of the problem.

Also, don’t forget this while you’re troubleshooting; your receiver(s) are also drawing power off the BEC circuit. Point being, if all the servos lock up, then ‘maybe’ you’re unjustly blaming the servos (thus, putting a final nail in my hopes of making a sale).

Anyway, I think you’re lucky your $5000 model was on the workbench when you discovered the issue because the condom of consequences isn’t usually lubed, but I digress.

Next, to the part of your question important to me, what have we got to compare to Futaba’s A703 servos? Well, as it happens, we have more than one for your consideration, we have four! So that’s next.

Disclosure

If anyone suspects we’re going to say an HPS-A703 is junk, they’ll be sadly mistaken – nothing could be further from the truth. It’s quite a finely made product. Do I think ProModeler is better? Well, yes as it happens, I do (as I should), and I also believe I can prove it to you.

So in what follows, please do not interpret anything said as derogatory of Futaba, or the company’s products. Instead, it’s my sincere belief they offer one of, if not the highest grade, RF-system available to the consumer market, and excellent servos to boot!

Moreover, in the interests of full disclosure, know this about your author (that would be me); following a few years with Orbit, and a 15 year stint with Kraft equipment, I’ve flown Futaba radio systems since 1989 (and continue to this day with an 18MZ). Saying, there’s a soft spot in my heart for Futaba, which colors my thinking.

However, this last doesn’t actually matter because it’s on you to suss out which servos best serve your interests. That, and my job right now isn’t to love on Futaba, but to show why your money is better spent with a servo-specialist versus those from an RF-specialist. Particularly when you’re equipping a seriously expensive RC model.

Introduction

Is anyone surprised at learning we’re been asked more than once what we have servo-wise to compete with Futaba’s finest servos? At the time of this writing, it’s their HPS-A703, but we’ve previously been asked about their HPS-A700 (then it was in regard to use in a XA-model, or extreme aerobatics aircraft). This means compared to this question – oriented toward an IMAC model – that guy got a different answer about which of our servos to use.

Facts are, we’re reasonably familiar with their line of wares so let me share this; we actually have four alternatives to an HPS-A703 for your consideration. Two BLS1 series, and two more within our BLS2 series.

What’s the difference? Torque, speed, and price . . . like, duh, what did you expect me to respond?

Lineup

The two on the far left are DS630 and DS930, an HPS-A703 in the middle, and DS845 and DS1155 arrayed to its right (note; the latter sport a huge 8mm spline shaft – there’s a reason). And with regard to all four of our servos? Their full part numbers end with BLHV.

This brings up the question; what do these various letter/number designations actually mean. Well, you don’t need Cliff Notes because it’s actually easy to suss out the ProModeler parts-code;

• DS = Digital Servo
• xxxx = torque rating in oz-in
• BL = Brushless motor (CL = Coreless and DL = 3-pole iron)
• HV = voltage range, where 8.4V is considered high voltage

So all the servos in the above photo are equipped with brushless motors. And you know this because of the BL within Futaba’s model description of HPBLS.

Heck, even if you don’t know jack about the motors inside your servos, just the fact their best (and ours) use brushless motors is a clue these are the best motors money can buy. Meanwhile, operating on the assumption you’re not a subject matter expert, then review this material because you may find it of use even if you end up buying someone else’s servos;

• About RC servo motors

Note; we put this article together to help modelers learn about the differences between the 3 basic types of motors offered in the industry. These being iron-core, coreless, and brushless. This, in part, because nobody else does.

Since everybody offering RC servos use these three types of motors it means whether you favor Futaba, Hitec, Spektrum, or ProModeler servos, in making it our business to cut motors open using a lathe to show you what’s what inside, you benefit.

But besides educating, we’re also hoping to score brownie points!

Anyway, along with close up photography, reading the article means also learning several reasons brushless motors are best. This, to include their place within the hierarchy of cost structures, which is reflected within this little graphic . . .

. . . which shows price plays a role in sussing out best. And as a general rule, the more things cost, the better. Surprised?

Cutting to the chase; we have had many ask about servos in comparison to the HPS-A703. Enough so we bought examples expressly for the purpose of disassembling and photographing their guts to help put together this brief guide showcasing how they match up.

As for why use photos? In part it’s because they’re worth a 1000 words (and I’m wordy enough). But using photos means you don’t need to be an engineer to figure out what’s better for you as long as you have a pair of Eyeballs, Mark II (plus a few spare gray cells).

Against which servo?

As usual, it depends. On what? On how you’re going to use your servos. This fellow’s query is specific to an IMAC-oriented model airplane versus XA-oriented, a scale model, an RC truck, or boat.

DS1155BLHV

Since Futaba’s best is listed for $280 it would be easy to assume we’d put up our most expensive standard class example; the DS1155BLHV. But we didn’t because it blows the HPS-A703 out of the water with 1155oz-in vs 916oz-in, or about 20% more torque. The DS1155BLHV matches up better against the HPS-A700, instead.

Added to which, at 0.10sec/60° vs. 0.12sec/60° the DS1155 is also about 20% quicker transit time-wise than the HPS-A703. And it’s expensive! Basically, it’s really more servo than you need to throw at the IMAC problem, in our opinion.

Where we feel the DS1155BLHV is actually better suited is for a 33% and 40% aircraft that are XA-oriented because of their need for speedy servos (as well as rugged duty in RC trucks). More so than IMAC.

However, this is just my opinion, which is like a belly button because we all have one. Also means this is my best opinion right now, but of course, it’s subject to change as I gather more information.

DS845BLHV

Moving on, we could also have reasonably put our 2nd most costly standard class into the fray. Putting the DS845BLHV against the HPS-A703 is not crazy if you’re into XA but once again, overkill for IMAC.

This, because they compare fairly closely torque-wise (theirs actually makes 9% more torque). But at 0.06sec/60° vs. 0.12sec/60° ours is CONSIDERABLY quicker (on the order of 200%). Honestly? The DS845 is in a whole other league speed-wise (think Usain Bolt vs high school sprinter).

This once again makes the DS845BLHV servo fantastic for XA but because speed is a lesser consideration for IMAC use, there’s no real need to spend so much. So, once again, we felt this wouldn’t be fair to put up against the Futaba HPS-A703.

DS630BLHV

Note; we could also pitch our DS630BLHV hat into the ring for your consideration. This, because it’s a solid contender for plenty of guys using them in both 33% and 40% models.

Proof? Witness this experienced IMAC-pilot’s thoughts regarding the DS630 installed in his Dalton 330SP.

. . . but at 630oz-in vs. 916oz-in, a DS630 is down 31% torque-wise to the Futaba HPS-A703. And whilst 20% quicker than theirs at 0.10sec/60° vs 0.12sec/60°, the torque disadvantage is significant.

This means many/most modelers (with a marked general tendency to focus on torque instead of a speed advantage) would dismiss the DS630 out of hand. Thus, we don’t believe it’s a reasonable comparison to the Futaba, either.

DS930BLHV

Ultimately, we selected our 3rd most expensive servo as our best to put up against Futaba’s HPS-A703 for an IMAC application within a 40% model. It’s the ProModeler DS930BLHV.

And no, servos don’t know in what they’re installed. And yes, this is a judgement call based on how IMAC-maneuvers are flown versus XA-maneuvers.

Why the DS930? It’s because torque-wise 930oz-in vs 916oz-in is a wash (a mere 1.5% difference). And speed-wise? Both are rated at the same 0.12sec/60°, so the speed-specs are a wash, also. So like the little girl in the 3 bears story, a DS930 is just right for IMAC duty!

This next fellow (photo below) is coincidentally also flying a Dalton (like the previous photo), but this time an Extra 260 version. He has this to say about a set of DS930BLHV within his 40% class competition aircraft . . .

Disclaimer

So why this interest in pitting the servos spec-to-spec as closely as possible? For the same reason heavyweights aren’t put in the ring with welterweights. So while the title of this entry is matchUP, I’m no fool, either (meaning I know money plays a role in everything).

So even if you’ve got more money than God himself, despite our feeling we beat the HPS-A703 in many important categories, adding a price advantage is just smart business! Basically you can buy two DS930BLHV servos for the price of one Futaba HPS-A703.

But let’s dive deeper because most modelers participating in the sport with 40% aircraft (and large turbine jets) are, and I mean no offense, in a whole other league compared to the average club pilots. Saying guys who can afford $280 servos tend to also look beyond the price simply because they can afford to. Club pilots, on the other hand focus solely on price (hence the rise of off brand east Asian imports).

And competition IMAC pilots are a whole different breed altogether! They don’t give two flips about cheaper, they’re 100% about better. Better what? Better anything! Basically, they’ll kill for a 1% improvement.

Saying what floats a competitor’s boat is better performance, better durability, better quality, better cooling, and pretty much better anything! In a word, competitors are seeking more than just value. But it’s within that word – value – where ProModeler really tells its story.

We’re saying the Futaba HPS-A703 is a very fine servo but the ProModeler DS930BLHV is better – and – we believe we can prove it.

Big words? Yes, definitely so we’re going to resort to photos. And if you’re short of time, then just scanning the photos (and the captions) is enough to get the gist.

HPS-A703 vs DS930

First up, the servos placed in close proximity. In boxing it’s called the tale of the tape, but here it’s the side-by-side photo. The idea is to give a sense of scale – basically they’re same size.

We’re speaking of a pair of standard-class servos (possessed of a 40x20mm footprint). There’s also 10mm between the mounting screws on each beam. They’re basically drop ins for each other.

This means swapping in one for the other leads to no mechanical compatibility drama. This is a good thing since we hope folks will be ditching their HPS-A703 in favor of a set of ProModeler DS930BLHV.

Appearance

Looks-wise they’re both handsome in their own way. The ProModeler in a simple and understated sort of way, the Futaba being dressy. Like in a stylish black tie and tails sense!

Black finished off with striking bits of red and blue, along with 13 tick marks around the around the output shaft, make for a very sharp looking package. Can’t deny it!

That, plus laser etching and silk screening on the sides boldly proclaiming the Futaba brand identity. Plus more laser and screen work on the bottom. Hate to give it up, but score a point for the Futaba’s better looks because we’ll admit, that’s one handsome rascal. This makes the score is 0-1 in their favor right out of the gate!

And we get why, too. After all, appearance is everything to a certain crowd. They like their models to look sharp and for the gear inside to look sharp, also. Facts are a lot of servos sell based on being pretty, else marketing companies wouldn’t waste time and money dressing them up, right?

Thing is, we’re an altogether different breed. Instead of a marketing focus, ours sees an emphasis on engineering, instead. Means we’re more into form follows function. But all that matters is your opinion.

Center case – cooling fins

Next, while we willingly sacrifice appearance (the immensely valuable promotion value of the laser-etched logos on the case sides), we do it in favor of hogging from the solid billet of 6061-T6 alloy center.

What for? To create cooling fins! Saying cooling is more important than looks – at least in our book. This next photo is a porcupine center. We call it a porcupine because of ten bolts (with tiny o-rings) sticking out like quills.

Why cooling fins? Well, if you study specifications (all ProModeler servos have a spec sheet like this one below) and if you eyeball the 4th and 5th voltage columns . . .

. . . and specifically for the purpose of eyeballing current draw at stall (when servos make their rated torque), you’ll note how it’s drawing 6-7A at full song (output depends on input voltage).

While we don’t have the full specs for the Futaba HPS-A703, just using grade school math and Ohm’s Law for power, P=V*I (or W=V*A).

• P = Power (watts)
• V = Voltage
• I = Current (or amps)

And plugging in some numbers gives us 8.4*6.7=56.28 so we’re dealing with 50W devices. That’s a lot of heat, believe me!

Like have you ever tried changing a hot light bulb instead of waiting to let it cool? Burned the crap out of you, right? Major point being, the cooling fins on ProModeler servos are not decorative. 

When you’re working your servos really hard, there’s a butt load of heat to dissipate. Yes, smooth aluminum alloy will do the job, but more slowly than a case section equipped with cooling fins. Reason fins work better has to do with the advantage of more surface area from which heat can radiate! Simple physics!

Why doesn’t the HPS-A703 have cooling fins? Well, Futaba doesn’t tell us but as an educated guess, the amount of time a case is being machined is a critical factor toward cost. Since time within the machine cell is about doubled due to fins (and man-time doubles also since the man tending the machine has to wait twice as long), fins costs more. So our theory has to do with reducing product cost.

Meanwhile, circling back around to the Futaba HPS-A703 and our not finding current draw information, if anybody finds this information, kindly share that we may update the article. Minor point being, since both output in the +900oz-in range, then you can reasonably expect both to consume similar amounts of current (because you can’t produce power out of thin air). Saying no matter which servo you select, both make a fair bit of heat that needs dissipating.

Bottom line? Cooling fins are functional. So ask yourself this; when you’re ponying up for your servos, knowing how you fly and how long you expect such an expensive purchase to last, would you rather your servos had smooth sides with logos, or cooling fins? After all, heat is the enemy of electronics, right?

Anyway, if you’re keeping score, we believe a reasonable man will score a point to the ProModeler side of the ledger for the cooling fins. Means the score is now tied 1-1.

The next photos are their respective bottom covers, the part that conceals and protects the printed circuit board (the electronics section).

Electronics section

Let’s see what we’ll learn. One thing that’s striking is we’re finding more and more servo brands decorating with laser etched propaganda, or silk screen printing. Sending these out to be decorated (or doing it in house) constitutes another operation, and it is isn’t cheap so we don’t do much of it.

Reason we send them out instead of doing them ourselves is because it’s hard to beat a man at his own craft – but – that said, we also keep laser etching to a minimum because of cost. After all, especially on the bottom electronics cover, what’s the purpose? Like once it’s installed, who is going to see it?

But while we’re looking, look close because there’s an important detail to take note of. Don’t scroll for the answer, observe!

The eagle eyed amongst noticed ProModeler relies on an assembly held together with Allen head, or socket cap screws. These are the good ones, too, grade 12.9 versus we don’t know what Futaba uses for their Phillips head screws.

While fasteners aren’t a huge deal, as engineers we prefer the non-slip nature of the Allen drivers . . . what about you? Is it reasonable to assign ProModeler another point, now 2-1 simply due to our using better fasteners – is this fair?

Anyway, next, let’s open them up.

So let’s skip past the covers themselves, both are alloy. Theirs is anodized black in keeping with the corporate identity. We don’t spend extra money on color anodizing. But eyeball the o-ring in the ProModeler cover.

See how it’s sitting within it’s own ridge or groove? This turns out to be important. For now we’re going to take a point for this little feature (and prove it’s better than how they do it, later), please trust us.

Score’s 3-1. Next up, the guts . . . the PCBs (printed circuit boards).

Potting compound

Before moving on, take note of what is really quite important in the above PCB-photo – it’s the copious amounts of potting compound we slather on. That’s the white stuff that almost looks like icing on a cupcake!

This stuff (depending on vendor) can be white, black, or translucent. The color doesn’t matter, and we use all three interchangeably depending on supplier.

Thing is, once applied to the PCB it flows – oozes – in between all the components (especially the thin solder joints for the legs of microcontroller and FETs. Then it sets up (hard, rubber-like). You can actually dig into it with a thumb nail, and leave a temporary mark, but it soon disappears. It’s tough stuff.

Its purpose? This stuff is what helps supports the components and protects them against shock and vibration.

And it’s not even overly expensive, and certainly not difficult to apply, but it does stink, and application is tedious to apply neatly. Not only is it time consuming (and this really just speaks to the technician’s time, or what labor costs), you also don’t want it on your hands (so the work is done with gloves). It’s sticky, stinky, and we refer to it as monkey snot!

Anyway, I suspect the reason others don’t use it (or as much) is they don’t fret about government business. Not the way we do. That, and time is money so applying monkey snot means higher labor costs. But believe me, potting compound is a big deal if you have any hopes of meeting MIL-STDS.

More regarding this, a little bit later, but next, let me show you how boards are made. This, in hopes you’ll grok why all this matters.

PCB – Printed Circuit Board

So the way a modern day servo works isn’t some big state secret. They feature a classical set up little changed from the 1970s which comprises a motor, pot, transformers and an H-bridge. This last varying voltage (± and 0) to start and stop the motor based on potentiometer position.

It’s absolutely not rocket science.

So the individual PCB are actually done as part of what’s called a card. Tiny creases, much like stamps have perforations within a sheet at the post office, delineate the actual boards.

We fold and crack them off into individual PCBs. It’s almost like tearing a stamp off a sheet, to get 20 individual pieces from a card.

This photo is shared to give a sense of scale since the servo is familiar. Note the brushless motor with 5-pin connector. And while it’s hard to see, the motor has 3-pins for soldering to the board.

Shanging subjects, folks always want to know why ProModeler are so quiet. Basically, our servos don’t squeal and whine like competing digital servo designs. This is a big deal. We’re not going to tell you.

Why not? Honestly? We play this kind of information close to the vest because we’re talking about the crown jewels. But it’s no surprise we (as does Futaba, and everybody else) rely on a design comprising micro controller and 3 FETs plus bits and bobs like tantalum capacitor, resistors and diodes.

The real issue of concern is how very fragile and susceptible to damage due to vibration the attachment of these components are to the board. Reason is, solder cracks easily. This is why connectors are more reliable when crimped versus soldered. There’s a solution, which we’ll come to in a bit.

So the microcontroller controls everything via a PID algorithm (almost like using a pair of SPDT relays to reverse the motor). The algorithm runs curves optimized through software controlled tuning based on the mass of the rotor. We’re only talking a few hundred lines of code. And we avoid using an external crystal for the purpose of making the servo more resistant to shock and vibration (both of which play Hell on components so the fewer, the better).

So people often ask about the process of making the circuit boards. We don’t do the production quantities, just the prototypes. This, because production quantities requires a huge facility with a butt load of pick and place machines like this one.

Part of how you get a better price out to customer like you isn’t just from using suppliers of the lowest possible cost, but in being smart and using people who are genuine experts in their field. But you have to know what you’re doing so in-house prototyping let’s you figure it out.

Later, when it comes to production at scale, then there’s no sense in us replicating a huge building full of pick and place machines we can’t possibly keep busy when we can have them made by specialists. But only after we prove the board design! So one’s enough for our purposes.

Components

Next, those reels you saw in the above photo? Each is loaded with individual components on a tape. There are hundreds if not thousands on a reel, and each reel is loaded a different component.

What component? Whatever is required for the particular board being made – like duh! So these components can be FETs, resistors, microcontrollers, diodes . . . whatever!

And here’s the thing, if you’re willing to pay about 15% more, these component parts can be bought in MIL-SPEC (military specification), and we do. In fact, anything and everything that can be bought for a ProModeler servo is MIL-SPEC.

The other guys? More often than not, we see decisions made – in our opinion – by the marketing team instead of the engineering team. So this informs our opinion about their product line and who runs the place, but we won’t speculate in specifics since we don’t want to get sued. For now, let’s back to individual electronic components.

Once placed on the board, the next step in the process is the reflow oven. These can have temperature zones so that components on one side aren’t melted off when the board goes back through to solder the components on the flip side.

That’s right, we use PCB with components on both sides to save space. Doesn’t make us geniuses, everybody does this because the inside of a servo – the space within – is precious because other stuff has to live there, too. Not just the PCB, but the pot, motor, we must even allow enough room for the wiring!

Inside your servo

So if you feel like it, removing the four screws securing the bottom cover expose the electronics side. All you need is a 1.5mm Allen and you’re in business. Void the warranty? Nope! Taking a peek won’t hurt anything!

Yet if you look at the PCB of your servo, you’ll see very little. Why? It’s because of something you get with a ProModeler servo that you don’t get with hobby grade servos like you are typically offered by the marketplace. All meet a minimum of three MIL-STDS and these meet eight.

Do these matter to do? Dunno, they should because it’s your money. We’re just informing you what’s what because you decide what matters. So the reason you don’t see much is the PCB gets coated in potting compound.

Failures

This next photos shows why we apply potting compound and the consequences of an inadequate application . . . component failure! The thing about failure is what do you do about it?

Our view is failures are nothing to be ashamed of as long as they become an opportunity to learn with the purpose of overcoming. After all, it’s not like we had success from the very first beginning.

Fundamentally, failure offers us knowledge of what to expect if nothing changes. So it’s an opportunity to make changes, e.g. incorporate what we’ve learned because like everything else, trial and error is involved in iterating our designs.

So these things take time to sort out but we’ve never been afraid of failure, or of showing what’s happened . . . badge of honor in a way.

Purpose of this photo, however is to help convey why the application of potting compound is important for peace of mind. For example, instead of thinking like a modeler, put yourself in the shoes of a project engineer speccing servos for a military contracted UAS.

Ask yourself this, what’s more important, the value of the aircraft (perhaps more that $85,000), or the mission delivering ammo to soldiers under fire? Like I sometimes wonder how these guys sleep bearing such huge responsibilities. What don’t I ponder? Why they make a big deal of MIL-STDS.

So for your $5000 model, granted lives aren’t on the line, but would you rather PCB components of your servos be exposed to damaging shock and vibration just because someone chose to save a few bucks? Or would you rather one slathered in protective potting compound?

Anyway, I hate to belabor the point, but I have a theory for why competing brands don’t show the inside of their product. It’s to do with the ‘good enough’ theory. Since professional product photos plus specs have always been good enough for consumers to fork over the dough, then don’t rock the boat, or change.

Anyway, we show you the guts of our servos out of respect. Or put another way, we trust you to suss out what’s best for you.

A brief birdwalk; in 1972 when I was getting into the sport, Bill Norman of Homewood Toy & Hobby opened a servo up on the counter and showed me how it was made. These days that doesn’t happen. Of course, we’re also hoping to push your hot button because everybody loves quality.

So by showing you these things in intimate details, things like potting compound, we’re hoping to positively influence you because unlike the contracting officers who writes MIL-STDS into the specs, modelers aren’t exposed to why this matters. That, and we figure the more you know, the better our chances of earning your business!

Recapping, the fundamental reason for the potting compound is it mechanically locks the bits and bobs in place on the printed circuit board. Otherwise, the only thing that secures the individual surface mount component to the PCB are teeny-tiny spider-leg like solder joints. And when solder is all that’s holding things in place, vibration can play Hell with your servos. And this is a detail regarding just two of eight MIL-STDS for this servo.

Anyway, and while we can’t speak for hobby grade servos, with the DS930BLHV you get a servo meeting these eight MIL-STDS.

MIL-STD-810H

• Shock – Test Method 516.6
• Humidity -Test Method 507.5
• Vibration – Test Method 514.6
• Acceleration – Test Method 513.6
• Sand and Dust – Test Method 510.7
• Water Intrusion – Test Method 514.5
• Altitude <70,000’ – Test Method 500.6
• High Temperature – Test Method 501.5

Since MIL-STDS matter to the government . . . are they a reasonable proxy for you – meaning do you get better servos? We suspect the answer is yes.

Means it would also be reasonable to allocate another point to ProModeler about now, eh? This makes the score 4-1.

Transmission section

So let’s flip the servos over and look at the topside – at the transmission section. Honestly, both gear trains look pretty good.

Futaba mentions using stainless steel for the output gear, but not what grade and they remain schtum about the other gears. We think the others are a good grade of high carbon steel (but this is just an educated guess based on experience, nobody from Futaba has told us).

However, with ProModeler, the rest of the gears in your servo are also stainless. Stainless makes a big difference in the rest of the gear train. We feel it’s better because stainless is a more rugged steel than high carbon. Tougher.

So in the same way the old Timex commercials proclaimed, takes a lickin’ and keeps on tickin’, so do stainless gear trains – else Futaba wouldn’t take pride in mentioning they’re using a stainless output gear . . . make sense?

Anyway, and FYI, where other materials like high carbon steel or titanium will fracture, stainless steel being more rugged absorbs the blow and keeps on going. Moreover, that it’s more expensive is just part of the deal (but we save on cosmetics like color anodizing and laser etching to help make up for it). Saying we use stainless for a reason.

And since details count, take note; we use 303 stainless for the bull gears (the larger diameter gears), and 420 stainless (which can be hardened) for the smaller pinion gears. Note; the pinion gears are the ones which drive bull gears. Always, never the other way around.

And if you know what to look for, you can see the subtle sheen that indicates stainless gears. And I’m absolutely NOT saying Futaba gears are bad, I’m saying we believe an all-stainless steel gear train is better.

Is this another place to give another point to ProModeler? Looks like we’re starting to run up the score . . . 5-1 in favor of ProModeler.

Center case – intermediate

So now let’s look under the hood (so to speak). Let’s field strip the gear trains and eyeball the case components themselves. After all, the case is the foundation element that holds the gears in alignment. What I found was something of a surprise. And we’re about to really run up the score.

The Futaba uses a polymer intermediate case center fitted to the alloy main center. Ours is 100% alloy. Moreover, we only use poly intermediates with servos outputting below 400oz-in.

But even more importantly, they’re not doing anything to reinforce at the gear shaft, the bore is molded . . . straight plastic! Not kidding.

Now this is something of a red flag in our opinion. Reason for adopting plastic is because it’s lighter and cheaper than alloy. But make no mistake, it’s also weaker. Means a crash that maybe doesn’t take out gears almost to a certainty damages this plastic piece. Means it begins to wear.

For us, the fundamental reason for a plastic intermediate case section is lowering cost (and to some extent, weight, but mostly cost). We know this because we do it for some of our servos (before switching to alloy when we go north of 400oz-in).

But there’s a major difference because when we opt to use a plastic intermediate section, we press in a bronze bushing. Its purpose it to reinforce the plastic where the steel gear shaft is fitted to support the transmission gears.

Note; we do this for all ProModeler servos. Even ones costing a mere $30 like the ProModeler DS90DLHV depicted, below.

Look closely at the above photo, do you see the small bronze bushing? Now look back at the Futaba HPS-A703 intermediate. Do you see the difference? Honestly? This is a big deal in my opinion (and it should be in yours, also).

That shiny bit of bronze in the center of the red plastic (where the intermediate gear-shaft is fitted) anchors the center gear shaft. It’s present in every ProModeler beginning from our least expensive 90-oz-in servo because we don’t take shortcuts. Yet Futaba’s top-of-the-range HPS-A703 outputting north of 900oz-in has bupkis and relies on relatively soft plastic?

Problem with this are the internal loads (as the servo operates normally) will, over time, force the shafts to walk. By this meaning the bore will stretch out of shape (elongate). Then these normally perfectly round bores become egg-shape. Remember, plastic comes from the Greek platikos which means flow.

So this plastic *will* deform under load, it’s just a matter of time. Especially with a servo outputting 900oz-in. Like we’re talking about a butt load of force being developed, take my meaning? And on impact? Then all bets are off because shit happens.

And when the round bore become egg-shaped (and it will), then guess what happens to gear mesh? Yup, goes to Hell. This then accelerates gear wear because gear mesh becomes shit (profane engineering term for no longer within precise alignment).

When they’re working against each other, the involute (a special curve that describes the gear surfaces) slide smoothly one face against the other. Perfect alignment is critical. Shaft position is what determines this! It’s our view the hardpoints (bushings) are critical.

Upper gear case

What’s next? Let’s look at how the gears are anchored topside. Obviously, the shafts upon which the gears rotate have to be anchored at both ends, right? We looked at the bottom, so now let’s look at the top.

Note; we refer to this section as the top-side. Here’s what we found top-side, the upper case (whose job it is is to anchor the steel gear shafts upon which gears spin) shows another lack of bore reinforcements in the Futaba HPS-A703 example in our possession.

In common with ours, their upper case is also an aluminum alloy and in keeping with their style manual, it’s anodized black. But as you can readily see when you look into the depth of the bores where the shafts are fitted, the soft gleam of the raw aluminum means no bushings here, either. The raw aluminum readily contrasts with the black anodizing so it’s obvious.

Meanwhile, the ProModeler upper is reinforced with steel bushings. We refer to these as hardpoints.

And FWIW, these bits (hardpoints) are turned on what’s called a Swiss lathe and knurled. The purpose of which is to help anchor them, like teeth biting a steak, when pressed into the alloy of the case section.

OK, now we’re scoring at will, call it 6-1 because of the unreinforced case. We kind of feel like we’re beginning to kill them, and because we’ve made our point regarding the differences in the two products, let’s wrap this up.

Bottom line? It’s our opinion, for virtually any IMAC competitor, the DS930 is a great offering. Guys flying hard XA-maneuvers will want something faster so if that’s you, consider harder hitting servos, instead.

When it comes to faster servos, we have two on offer, the DS845BLHV and DS1155BLHV. Being a BLS2 design they’re built a bit different in that instead of being in-line 3-shaft design like BLS1 servos (and the Futaba HPS-A703), they’re a S-curve, 5-shaft design.

Regardless of which servo you select, we feel we give you a lot of bang for the buck. Especially with the DS930BLHV if you’ve been budgeting for the Futaba HPS-A703 because they’re like two-for-one.

Finally, remember that point I took for the o-ring at the beginning of the electronics cover section? That wasn’t us just stealing an unearned point. We took that point because when you eyeball the servo cases closely – observe – don’t look, you’ll see hidden seals.

Their o-rings are visible, exposed to damage. Unlikely? Nope, not when you go for a MIL-STD involving dust intrusion because sand and dust are abrasive. Over time (24-hr test cycle), blowing sand will readily wear the tiny diameter of the rubber down and gain entry.

The o-rings of a ProModeler servo are invisible to the eye after assembly by design. They are fully encased expressly to protect them from sharp object damage. These things are very, very thin!

Protecting the delicate case-section o-rings is a really is a big deal because unless fully armored (meaning encased by metal), then the delicate rubber o-ring becomes vulnerable to external damage.

This is how we earn;

• Sand and Dust – Test Method 510.7

. . . because that stuff is pernicious and will wear down the rubber and allow ingress of contaminants. What’s more, we don’t go the extra mile for the sheer joy of it (actually, we do), but because these are requirements of our prime customer.

And it’s you who also benefits from all this attention to detail. Think I’m kidding? Not if you fly in the desert southwest of the United States, we’re not because dust’s part and parcel with the experience!

Added to which, servos mounted eternally beneath the tend to get a bit of exhaust or smoke oil, right? Combine dust and oil and over time, it’s bad juju.

So if you’re thinking our using so many o-rings plus an enclosed design is unimportant, maybe you haven’t been thinking it through. now that you have more information, is sealing it up tight a bad thing? Or have we just run up the score, further?

Wrapping things up

Bottom line, some folks will buy the Futaba HPS-A703 because it’s always worked for them. We get it, and respect it because we have long respected Futaba as the very best from the days of servos like the venerable S148, S9102, and more!

But if you’re going to be the king, you have to kill the king. And thus, we can’t hide from their best, we have to take them on and lock horns. This, despite the high esteem in which we hold them, and their products. With the DS930BHV we’ve given it our best shot.

We feel we’ve shown you a servo with similar performance to the HPS-A703, which offers you MIL-STDS for shock, vibration, water and dust intrusion, and more.

A servo that also operates cooler because of fins CNC-machined into the center case. Fins, which increase surface area to better radiate heat away.

Ultimately, we believe your investment will also last longer because we fitted it with an all-stainless gear train. And because we took the trouble to reinforcing shaft bores for the gear shafts upon which gears rotate using steel bushings. Speaking of more durable hardpoints.

Then there are details regarding the use of a polymer intermediate section – sans bushings – which leads to questions about the long term durability of our competitor’s wares versus the immensely stronger DS903 with an all-alloy case. This can’t be glossed over. It’s important when you’re dealing with ~900oz-in of torque.

Added to which, there are little touches like using Allen head socket cap screws instead of Phillips. And don’t forget how instead of three o-rings the DS930 uses 13 seals to protect your investment. And, how instead of some being exposed to external damage, they are 100% fully captured (hidden), thus protecting them against external damage.

Honestly? If the DS930BHV were merely as good as the Futaba HPS-A703, then we’d have wasted your time. But we think it’s better, and believe we’ve proved it.

But, of course, the only thing that counts is your opinion. So what do you think? Is it time to add a set to your cart? If so, then also consider our servo arms.

Servo arms

These range in length from 15-60mm. We CNC machine them from a solid billet of 7075-T6 alloy and they include a backlash compensating, clamp design. This means in addition to an axial screw securing them to the output spline shaft, you can also snug them up radially against any possible lash between the parts.

We mill and broach these, then drill and tap for M3 mounting hardware (on 5mm centers). They’re a really nice bit of kit and add that finishing touch to a special aircraft – yours.

And note; these servos aren’t just for IMAC use. Scale and sport modelers value them also. This, because power and great centering never goes out of style.

Further study

You may find it a profitable use of your time to review this material;

• BEC or dedicated pack?
• Will ProModeler servos work with NiCds?
• On the batteries John prefers using
• Why’s my pack got two JR-connectors?
• Will a Hobbywing Max6 run my servo?
• How to determine flight time for a 2S850 LiIon
• How many Amps can the servo connector handle?

Q2. Am I better off with DS1155 or DS930 for my 40% IMAC model?

A2. Remember what it says in the Bible (Matthew 6:24) . . .

‘no one can serve two masters.’

Put into modern day parlance, either you set up like a 3D-god (think Jason Dusia), or for smooth IMAC performance. One – or – the other, but not both.

This, because the setups are polar opposites. One is lightning quick with enormous control throws to enable post stall maneuvering. The other is all about precision, meaning juuuust enough throw for the maneuver, and not one iota more!

The idea of the latter is to retain 100% of the resolution, which the RF-system offers. But an XA, or 3D setup, tosses resolution out the window. These models use the longest possible arms. The downside is this shows up as huge amounts of free play at the trailing edge of the control surface.

Meanwhile, an IMAC model is set up with the shortest possible link position and grabbing the end of a surface shows a lot less free throw . . . even though the servos are identical. So leverage for huge throw (long arms) magnifies the inherent backlash between the gears. It can’t be helped because zero backlash doesn’t exist.

So fundamentally, a model set up for XA stuff loses all semblance of precision. I’m sorry, but you have to choose, which is what we learned as kids at Bible study! Bottom line? If you’re the 2nd coming of a Dusia, then you must equip your model for that. And from ProModeler, this means DS1155 with 55mm arms.

Conversely, if you’re a smooth IMAC-type pilot, then spending your money for such fast and powerful servos as the DS1155 just helps you, a) mentally masturbate, and b) eat a hole in your wallet, but you’re actually better off with the DS930BLHV, instead. Or maybe our DS630BLHV. Depends.

And opt for PDRS35-25T or maybe PDRS40-25T servo arms.

So turning now to quote from the bard, when Polonius said to his son Laertes in Hamlet, ‘to thine own self be true‘, this is what he meant, and for you, it means pick either an XA-setup or an IMAC-setup!

Now, switching gears, if you’re a fan of pull-pull rudder controls, let me show you one last thing, a pulley for the job instead of a tiller arm. This, because sailors harnessed ropes and cable hundreds of years before pilots and a pulley is the right tool for the job.

These pulleys are available in three sizes, 34mm, 50mm, and 100mm and above is a PDRS100PP-25T (100mm diameter) fitted to a DS930.

Note; while the cables usually criss-cross, this doesn’t matter in the slightest. Anyway, your benefit of using a pulley versus a tiller is the non-pulling side cable doesn’t go as slack because excess is taken up as it’s wound around the perimeter resulting in more precise control in turbulent air – and is there any other kind during a contest?

Here’s a PDRS50PP-25T (50mm diameter) within a 30% IMAC model.

Finally if money is important and you’re a shrewd judge of your needs, the facts are we offer servos costing just $100 that may satisfy you perfectly in both 33% and 40% models. This, because the answer to which are the best servos? As usual, it depends!

Final thoughts

In closing, let me offer a few final thoughts. Begin with perhaps reviewing this article because it may further influence your thinking when it comes to spending big money on servos:

• On rebuilding damaged DS505s

Bottom line? The right servo for you is a reflection of your innate talent, your goals, your willingness to practice, and your budget. Feel free to reach out and speak with me, I’m try to be readily available;

• Telephone: 407-302-3361
• Email: info@promodeler.com

. . . and let’s see what we can suss out if we put our heads together!