Extreme Flight 69in Turbo Raven servos

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So yesterday, as I am wrapping up my day, a long-time customer emails about experiencing gear failure of a DS160CLHV on the rudder of a model. Fortunately, being a good stick, he'd managed to bring the plane in to a safe landing. Anyway, he put some good questions to me, for which I suspect others would like the answers, also . . . and just like that, we find ourselves with another caseSTUDY. This time regarding the Extreme Flight's 69" wingspan Turbo Raven (a model so nice, I own one myself). So here's what he wrote . . .

I have a DS160CLHV servo with maybe 80 minutes of airtime. It was used on an EF Turbo
Raven for pull-pull rudder. The smallest pitch gears, perhaps #3 and #4 in the chain from
the pinion, stripped completely. No crashes, no hard landings. I am at a loss for the
reason. Luckily, I saved the airframe. The rudder was nearly at neutral.

Anyway, I know you were going to replace the gears in these servos with steel. Have you
done so and are they a direct replacement for the old gears? I am also wondering if these
are not enough servo for the Raven. I have 4 sets in 60” aircraft and so far no issues but
the Turbo Raven is a bigger aircraft.


So my response forms the basis of the caseSTUDY, and while this TL:DR cuts to the chase, it does so without nuance. First my brief response . . .

  • Yes, we've upgraded the DS160CLHV to steel gears.
  • And no, we cannot retrofit existing CL-series mini-class servos.
  • And yes, it's our opinion the original all-metal gear DS160 is enough for a 69" TR, but
  • Aggressive pilots shouldn't use that servo within such a large model

With the last two answers you can see I'm trying to have it both ways. In truth, this is what's meant by nuance because as always, the real answer for whether the DS160CLHV should be used in the Turbo Raven is . . . it depends.

So I'll begin by noting he's been happy flying the same DS160 servos in several 60" airframes (he said as much). And so have a lot of folks. In fact, and quite frankly, almost nobody complains about the DS160 within that class of airframe (60"), and some are flown quite hard, and for many, many flights (to include the 69" TR).

Thus, the DS160 has become a favorite of many pilots for very good reasons including, it's;

  • strong
  • fast
  • centers well
  • cheap

. . . and these are pretty much the four best servo-qualities in the world for a pilot, agreed?

And to be blunt, if this were false, the forums would be lit up with complaints. They're not, ergo what I'm saying is true. And as further proof, I share what customers tell us . . .

So the DS160 works very well in 60" class 3D models to include the larger 69" Turbo Raven. But if there's been a knock against the DS160, it's that within the same basic size air frame (60"-class), Extreme Flight also offer the 69" wingspan Turbo Raven and 84" Turbo Bushmaster, and these might be a bit much for the DS110 and DS160 servos.

Note; both use the same power sub-systems (6S3300-4000, spinning a 16x8 prop, and <100A ESC), and are cut (the servo mounts) for the same size servos (16x36mm footprint), e.g. mini-class. But these two aircraft have a *substantially* greater wingspan.

And that last (more wingspan) meant trouble for some modelers (but not all) because it also means more leverage acting on the servo due to the force of the airflow. And while leverage is important, we'll have to come back to this. Please, first allow me a brief birdwalk regarding gear size because it's fundamental to this story of leverage, or why the servo broke in the air *but* at the same time, this doesn't mean they're defective.

We'll use four different servos to illustrate - they're the ProModeler Century-class servos.

Century-class servos

We offer to the market 4 servos outputting ~100oz-in. From smallest to largest, they're our;

  • DS105CLHV submicro
  • DS100DLHV micro
  • DS110CLHV mini
  • DS90DLHV standard

We call these our Century-class because they're all basically outputting about 100oz-in and there are 100-years in a century (nothing tricky about our thinking). Thing is, while they output about the same torque, they couldn't possibly be more different - as this photo demonstrates.

- The ProModeler Century-class of servos . . . the DS105, DS100, DS110, and DS90

What's important about the Century-class isn't that they all output about 100oz-in *but* that the servos are different physical sizes. And an obvious corollary is while their gears are sized to handle the output (transmitting 100oz-in of force, plus a minimum of a 50% safety factor), then the servos with physically larger gears will also handle significantly more input torque (force feeding back into them). Yes, feeding back into them . . . and this is important as it relates to leverage. And there's that word, leverage, again. So, yes, we're going around the world but we're coming to the crux of the matter, leverage.

Anyway, and put another way, when speaking about gears, and with all things being equal, bigger means stronger (well, duh!). However, there's another way to get there, material, which I'll address in a moment. So regarding the Century-class servos, let's work through some examples, beginning with the smallest Century-class, the DS105 submicro's gearset.

Gear size as it relates to strength

The DS105 gearset is rated to handle 150oz-in (50% more than rated torque). 50% greater is the design standard for that servo (and the minimum of all ProModeler servos). It means the servo has to withstand 50% more than rated output (at a minimum) being fed back into it. And to be honest, for a 9-gram class servo, that's little short of astonishing since competing servos are outputting ~30oz-in. So the DS105 truly is the mouse that roars!

Meanwhile, the gearset for the next size up, the DS100, are actually rated to 225oz-in. This is more than 50% because the DS100 is a derivative of its sister servo, the DS150CLHV and both use the same gear set. Thus, 50% more than 150oz-in is 225oz-in (150 x 1.5 = 225). Remember, 50% is our design spec safety factor for a gearset *but* it can actually end up being greater (the perfect example being the DS100). Bottom line, the DS100 can withstand substantially more input torque than the similarly rated DS105. Why? Simple, it's because the gears are physically larger!

So next up is the DS110 where the gears, once again being physically larger than those of the similar torque DS100, are rated to 240oz-in instead of 225oz-in because the DS160 uses the same gears (160 x 1.5 = 240). And we're going somewhere with this, because taking advantage of the fact the DS90 is derived from the DS360, its gearset is actually rated to 540oz-in (360 x 1.5 = 540) which is substantially more than the 135oz-in, which a 50% safety factor gearset would normally dictate for our 90oz-in servo! So instead of 50%, the safety factor is 300%, or far more than the 135oz-in required by our 50% stronger design standards. So DS90 owners get a gear set that's stronger than needed by a country mile - yee-haw!

And none of it is a miracle. It's 100% down to the larger physical size of the gears making them more rugged - not magic. So when it comes to gears, bigger is better in terms of strength - duh!

As for why this is, we need to briefly discuss gear ratios and tooth profile.

Gear ratios and tooth profile

Did you know gears work by sliding? Fact! The involute surfaces slide against each other. And the gear tooth is the end of a lever with the fulcrum placed at the center of the gear!

- The gear tooth is the end of a lever with the fulcrum placed at the center of the gear

So another little know fact is the gears are basically just an endless set of levers! Remember Archimedes, and what he said? Give me a firm place to stand and a long enough lever and I can move the world!

So the way it works is the longer the lever, the more force you can exert and with gears, the higher the ratio, the longer the effective lever. So with our DS160CLHV servos, you're seeing gear ratios of 290:1 . . . and that's one Hell of a long lever!

But turn it around 1:290 and when you try to shove 1 against 290, it becomes easy to exceed the strength of the involute gear's tooth profile and the material fails . . . the gear breaks. This is part of where I've been going with the concept of leverage. And explicitly why I advise against putting an arm on a servo and zinging it back and forth b hand.

Anyway, we also have leverage in terms of wingspan. Basically, where the longer the span, the longer the lever - we'll touch on this later. Moving on, let's delve into the actual gear construction.

On bulls and pinions

Another gear fact . . . pinions gears (the smaller gear) efficiently work against bulls gears (the larger ones) at a ratio of about 1:4 (and a reasonable max of 1:6). Note, another common bit of terminology for the bull-gear is spur-gear, ring-gear, or if you grew up on a farm around tractors, the master-gear - all mean the same thing.

Note; if you want to learn more about gears, and because we don't shy away from when things go wrong, you may enjoy reading this brief article on when gears need repairing. While it specifically features the DS505BLHV it's a superb primer on gear construction within our servos (and pretty much all servos on Earth).

Anyway, ratio just means how many revolutions of a pinion rotating/operating against the bull before it completes a revolution, and since the bull has between 3-6X more teeth than the pinion, the math is easy.

We just use number of teeth in the bull gear divided by the number of teeth in the pinion gear to get the ratio. For example, since the pinion gear attached to the motor of a DS160 servo has 10-teeth and it drives a bull gear of 32 teeth, then the ratio is 3.2:1 (32/10=5.2).

  • Put another way, to get 1 turn of the bull, the pinion must make 3.2 revolutions.

- Note; motor for the DS 110/160/210 series have the motor pressed into the case

So that bull, in turn, has a pinion pressed into it (thus creating a combination gear). Learn more by following this link, which as usual, opens a new browser tab so you don't lose your place here:

Recapping; so the bull has a pinion pressed into it, and that pinion drives another bull, which also has a pinion pressed into it, which drives yet another bull gear, and so on. And when all is said and done, the DS160 servo has a gear ratio (for the whole gear stack within the transmission) of 290:1.

But remember, the very purpose of the transmission is to multiply torque. It's how we get from a tiny and very high speed (but incredibly weak) electric motor to a servo generating ten pounds of force on a 1" lever (160oz-in is 10lbs because 160oz/16oz/lb=10lbs and by definition, this is on a 1" lever).

And in keeping with ProModeler's reputation for engineering prowess, we reveal technical details our competitors keep secret. Why? Simple, it's our belief an informed consumer is a better consumer. Put another way, knowledge really *is* power!

So in this instance, the DS160 gear ratio (290:1 for this particular servo) is disclosed within the specs. And we do so for each and every servo!

Leverage, or why the fact you can break servo gears in the air isn't a defect

So the way it works, the individual gear-teeth have to be small to fit inside the case. That, and we make them no bigger than they absolutely must be to save weight (weight's important, right?). That, and the size of the gear tooth (as we already know) determines their strength, or the force at which it fails. And as is the most fundamental case, the smaller the teeth, the easier it is to break them, and the larger the teeth, the more rugged they are - makes sense, right?

So the motor (rated in nano-Newtons) operates through a gearbox stuffed full of tiny gears with tiny teeth, e.g. the transmission section of the servo (just like the transmission for a car). Multiply the torque of the motor by 290:1 and the servo motor ends up producing quite a healthy amount of torque - all because of leverage. But while the output is healthy, the reverse, the amount of force you can input isn't so healthy. It's remarkably easy to break the gears by inputting too much force.

Against ratio

You see, the amount of force you can input into a gear by back feeding it (e.g. you into a servo via an attached servo arm, or the force of a breeze as the control surface sticks out at 80mph) can readily break the teeth. This, by the way is why we expressly warn against rotating servos with the servo arm manually - meaning you zinging the servo back and forth to feel the compression (just kidding). Anyway, this is why we expressly tell you not to do this and it's because the gear teeth are remarkably easy to break when operated against ratio.

Against ratio means gears are designed to multiply torque upward, meaning small gears driving bigger gears to increase torque. And they're physically sized to not break when operate at ratios of about 1:4 instead of when operated against torque, e.g. backwards at 290:1, capisci?

And thus, the leverage of the airflow against a ginormous control surface is enough to break the gears in flight. So is a foot bumping against the rudder of a model sitting in the pits, or bumping the rudder against the door frame of your car or house - all are enough to break the gears by exceeding the ultimate strength of the involute profile. And none of these are examples of a defect in the design but merely of encountering the mechanical limit of the servo!

- Turbo Raven's sweet direct elevator linkage gives you tight control

So basically, *you* or the breeze against the control surface, or the wheel of a model car, may offer up *far* more force than the gears can withstand. Your lever (so to speak) is too long for the profile and the gears will just break. Happens in a crash, too.

And like we noted, 290:1 is one really loooong lever and thus (and finally, closing this circle), here's where leverage becomes important. When you try to go backwards against the gear ratio and force 290 against 1, thing may break! What beaks? The gears.

So remember, the exertion of force by means of a lever is the definition of leverage and you, or the forces of a crash, or the forces of the breeze via the control surface, may be *much* stronger than gears are able to withstand. And when this happens, they break. And it's not because of defect but because the ultimate strength of the involute profile has been exceeded.

The evolution of the CL-series to encompass a stronger servo, the DS210CLHV.

So here's the thing, my customer wasn't the first to break DS160 gears in the air. Does this make them defective? Well as we now know, no, it doesn't. What's more, I never viewed this as a problem in the design . . . more like we've merely found the limits of the mechanism. Basically, there's a difference between a defect and a limit, do you grok? Point being, a stronger servo has always been something on my mind as regards the Turbo Raven.

Thus, when a customer calls to speak with me about a Turbo Raven servo recommendation, I try and put them on the DS205BLHV, instead. This is a brushless 205oz-in mini servo that transits in a lighting fast 0.052sec/60°. But customers resist this suggestion for two reasons. 1st, because it costs more, and 2nd, because EF actually recommend a sub-100oz-in servo (or did).

So they ask about using our DS110CLHV, instead of the DS160. Why? In my opinion it's mainly because it costs less than the DS160CLHV. The other rationale (and a very strong one at that), is they observe EF themselves are were selling the Hitec HS-7245MH, an 89oz-in at 0.11sec/60° servo for the model.

Note; they no longer offer the Hitec 7245MH and instead, the least expensive offering on their site (at the time of this writing) is the nice Savox SV1261MG plus the very nice but even more expensive (and very nicely made), MKS 9767 . . . both of whom - straight up - offer us solid competition.

Servo recommendations, specs and pricing

So let's look at EF's respective specs and street pricing to see what we can learn;

  • Hitec 7245MH - 89oz-in @ 0.11sec/60° - Amazon street price $77 each
  • Savox SV1261MG - 277oz-in @ 0.09sec/60° - Amazon street price $93 each
  • MKS HV9767 - 131oz-in @ 0.074sec/60° - Amazon street price $98 each

To reiterate, I try to guide folks off the DS110CLHV because I don't feel a Century-class servo is enough (although we *do* have some pilots flying the TR with our DS110CLHV and they're happy). What's more, the DS110CLHV gears don't generally break in the air (probably for the same reason the gears in the Hitec don't break). It's because nether of these servos are strong enough to force the surface out into the breeze in the first place (so called blowback).

So the above two servos (until EF augment their product lineup with something more cheaply made out of Asia, and perhaps privately labeled) are Extreme Flight's official recommendations. Moreover, it makes perfect sense if you think about it, for Extreme Flight to have quit selling the HS-7245MH for this model (and it's probably for the same reason I guide folks toward a stronger servo than our DS110CLHV). It just ain't enough!

However, unlike EF can (and do - by force majeure, e.g. simply by removing the HS-7245MH servo from that product's listing), I can only guide you toward a more powerful servo than the DS110 because the decision of what to buy is yours, not mine. That, and I'm not going to stop offering it.

- Over 700 flights of 4:30 duration, rudder servo remains tight, Mark Dobson, Merrimac, MA

So cutting to the chase, let me tell you who killed Cock Robin. ProModeler offer six servos that will fit the Extreme Flight Turbo Raven air frame;

  • DS110CLHV - 110oz-in @ 0.035sec/60° - $49.00 each
  • DS160CLHV - 160oz-in @ 0.064sec/60° - $59.99 each
  • DS210CLHV - 210oz-in @ 0.061sec/60° - $69.99 each
  • DS205BLHV - 205oz-in @ 0.052sec/60° - $79.99 each
  • DS355CLHV - 355oz-in @ 0.077sec/60° - $89.99 each
  • DS405BLHV - 405oz-in @ 0.050sec/60° - $99.99 each

Anyway, knowing some folks can break the DS160 in the model, I made it a practice to guide customers toward our lovely steel-gear equipped DS205BLHV, instead of the DS160CLHV. Thing is, this has been when costs becomes a factor. Cost? Yup, basically, guys don't want to pay $90-100 for a servo for a 60"-class air frame. It's just a fact.

So the basic issue is because our 205oz-in brushless mini costs a lot more than a DS160 and since most modelers are cheap bastards price sensitive with regard to the price of servos, the DS160CLHV became the choice de jure if not defacto

Is what it is but as a friend once pithily observed, 'Spending nearly as much for servos as for the airframe is stupid until you consider it won't fly worth a shit if you don't!' and he makes a valid point, but I digress.

So next, let's look at our 205oz-in brushless servo, the one costing 90 bucks.

- The alloy-case DS205BLHV has brushless motor, all-steel gears, and transits in 0.052sec/60°

To be honest, the DS160 is enough servo for all but the most brutal of pilots. In fact, for a lot of pilots, the DS110 is perfectly OK also because, and this is important, a lot of folks love how the Turbo Raven model looks and flies *but* aren't really into hard core 3D.

Added to which, if you like using gyros like the Aura8, then the stupidly fast DS110 works great with those (FYI, the DS110 was developed with model helicopters in mind and those all fly gyros and those pilots absolutely LOVE fast servos on cyclic).

But while it's our opinion, the DS160 is GREAT for a 60" airframe, and leaves a bit to be desired with a 69" wingspan model like the Turbo Raven (ditto the 84" span Turbo Bushmaster), everybody doesn't agree. Simply put, while the accomplished pilot performing XA maneuvers is better off with a +200oz-in servo, the DS160CLHV threads a needle of price performance that leaves it the perfect servo for probably 90% of pilots.

Anyway, while we try hard to guide folks to that DS205 servo, and many agreed with us and did just that, like this fellow, it doesn't make it the best servo for you.

So how do we define hard 3D, or XA?

It's like this; if you are performing Rifle Rolls (wide open throttle and full aileron deflection), a maneuver which is *really* hard on aileron servos and which not all 3D pilots can pull off, then you need more than the DS160 offers. Ditto if your repertoire include the violent Crankshaft (rough on everything), and Wall maneuvers (especially hard on elevator servos because it presents the entire bottom of the airplane to the forces of the wind). Similarly, if you fly the Parachutes, another maneuver tough on elevator servos, then you stand apart from most 3D pilots and are in a select group of what I call XA-pilots (Extreme Aerobatics).

Look, I don't know you, and have never seen you fly so I can't judge based on what you say on the phone - only you can make this decision. But trust me, if you perform the above maneuvers, then you really, really want more than 160oz-in. And our brushless all-alloy DS205BLHV is a superb choice.

But now let me throw you a lifeline if money is tight because we've upgraded the DS110 and DS160 to all-steel gears at the same time as we rounded out the lineup of CL-series mini servos with the introduction of the DS210CLHV. It was this, our introduction of the DS210CLHV, which puts into your hands a durable and popularly priced servo the will give you 200oz-in without breaking the bank

Best part is, we held the line on DS110 and DS160 pricing compared to the previous all-metal gear iteration. And we were able to do this because we've grown to the point where maybe we can't dictate to suppliers like the big guys can, but we're big enough we're no longer on the back foot when negotiating.

So if you're a sport pilot, the DS110 is a great alternative, and the DS160 is enough for how many of you fly so with these you get fast, powerful, great centering at a superb price. And if you feel you need 200oz-in, then the DS210CLHV is priced right in there with the long established and well made 89oz-in mini from Hitec (as well as the el cheapo made-in-Asia label-engineered alternatives.

Label engineered? Yeah, you know, where some hobby dealer decides to get into the servo game and their entire engineering contribution amounts to the art-work for the label. That, along with their brand they perceived as easy money collected from amongst the unknowing. These are servos someone in the far East is actually cheaply making for them because they can sell them under their label/brand and score easy cash. Whatever, just remember, caveat emptor.

So what's next? Well, since Extreme flight deem it worthy of offering the 277oz-in @ 0.09sec/60° SV1261MG, then it's worth noting for similar money you can buy the DS355CLHV, instead. Ours at 355oz-in is 28% more powerful whilst at the same time, @ 0.077sec/60° it is almost 20% quicker. Quicker is important for 3D. That, and it's built significantly better, too.

And by built better, I speak of things like bronze hardpoints within the case (at the gear shaft mounts). These are there expressly to ensure the servo will actually *live* when making that kind of torque. After all, once you get to nearly a 300oz-in mini servo and then pound the steel gear shafts against aluminum of the case, then let me tell you, the bores don't stay round for long unless they're reinforced. Thing is, once they go egg shaped, then the tolerance of the gear mesh goes to Hell and they begin to wear like crazy. Fact!

But beyond that, theirs lack cooling fins and if you think you can run a few amps through that servo and not shed heat efficiently you're in for a surprise. We mill cooling fins into our servos for the purpose of effectively shedding heat, not for decoration! Heads up.

Plus with ours, you get all-steel gears, which are way the hell stronger than whatever they're using. Then there's the MKS HV9767, again, no cooling fins, and they use titanium gears. Thing is, Ti is actually pretty soft and while it was great for the wing skins of the SR-71 Blackbird, the material actually kind of sucks for gears. And you don't need to be an engineer to realize this, you just need a pair of eyeballs Mk II and a brain. How? Simple, the proof is the money-is-no-object teams racing in F1 and NASCAR use transmissions with steel gears instead of titanium.

So why are some using Ti for gears? Simple, it's because the marketing types know that titanium (along with carbon fiber) are words that kick mental masturbation into high gear. Some will nearly salivate and these word definitely gets the rubes reflexively reaching for their wallets because they don't know any better. Truth is, titanium isn't good for gears because it's brittle, soft, and prone to fracture. Fact.

And note; the +350oz-in output by our DS355CLHV is enough to fly some significantly larger models, too. For example, this thoughtful fellow who uses them in his Extreme Flight 85" Extra.

So who should pony up for our DS405BLHV servos? Maybe nobody. Or maybe those who are out there actually inventing new maneuvers. Why? Well, if you fly really hard, then the +400oz-in being output by the DS405BLHV absolutely WILL shove that aileron out into the breeze with the authority a 160oz or 210oz-in servo simply can't. Is this reason enough? Dunno, your call but it's not very much more than what's being asked for some distinctly inferior Asian servos.

That, and when the DS405BLHV is working, because it's so very, very powerful, it'll be loafing compared to more heavily stressed servos. There's a school of thought that values overkill and the DS405BLHV is the very *definition* of overkill.

A few last thoughts before wrapping this up . . . what 'really' differentiates a ProModeler servo from the competitors? Meaning, what makes the CL-series better is 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 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 (modelers).

Point being, if you're looking at another servo, one which offers similar performance and pricing - but - hasn't been tested to military standards, then servos meeting MIL-STDS are always better (even if you don't need the benefit their enhanced durability delivers right now).

However, beyond making servos expressly designed to survive the abuse encountered in the real world, there are important ownership considerations worth mentioning with a ProModeler CL-series servo. For example, many are surprised to learn there are bronze inserts within the polymer case. These, for reinforcing where the steel gear shaft fit - hard points in essence. Makes for a twofer, e.g. the benefit of lighter weight with the durability of an alloy case!

Do you consider your servos to represent an investment? If so, then ProModeler servos are worth your consideration not just because they outperform the others, but because they're built to last longer. And the thrifty amongst us will especially recognize what receiving good value means in addition to receiving top level performance. Honestly, in this regard, it's well recognized your ProModeler servos really deliver, and here's why.

First, many modelers immediately notice the cooling fins machined into the case. All else being equal, cooler components last longer, right? But beyond this, even if you're not an electrical engineer, you'll appreciate other small touches - ones which are otherwise invisible.

Second, there's the matter of the 13 o-rings which seal the case. They're between individual case components, and at the output spline shaft, and beneath the heads of the ten grade 12.9 Allen head screws (used to secure the three servos in the CL-series together). And these thread into aluminum instead of plastic!

Third, there's how we protect the PCB from vibration with a conformal coating (instead of a cheapo square of foam rubber). Also referred to as potting compound in the civilian world, we just call it monkey-snot. Why? It's because it's such a sticky smelly mess to apply. But totally worth it!

So why do we bother applying monkey snot? Simple, it's because once applied to the PCB, it oozes between components and sets. This is the secret sauce behind our servos thriving in harsh high-vibration environments. Bottom line? This is an aerospace-grade technique, and one which also help makes ProModeler servos more valuable to you by prolonging service life.

After all, while they're destined for an electric model right now, who is to say - perhaps a few years from now - you don't choose to race high vibration Formula 1 models, or perhaps are attracted to helicopters? Thus, instead of focusing on just one thing, your ProModeler servos are versatile enough for wherever your heart may some day lead you.

So beyond performance, ProModeler is really about delivering good value!


When building a world class 3D model aircraft from the likes of Extreme Flight, then ProModeler offer you six really solid servo alternatives for customizing your experience. Fast for gyros, powerful for the aggression, and both!

These range from the stupid fast DS110CLHV, which is optimized for gyros and is outstanding at slow 3D maneuvers like Rolling Harriers and Torque Rolls, to the stout DS160CLHV, which has the muscle to power your aircraft through most aggressive 3D maneuvers like Blenders, and Waterfalls. And then there's the DS210CLHV, which will be your first choice when your skill set includes maneuvers like a Wall, Parachute, and Rifle Roll.

Plus our money-is-no-object alloy-case series like the DS205BLHV, the pricey alternative to our DS205CLHV which is pretty much the best +200oz-in class servo we know how to make. What makes it worth the extra dough? An all-alloy case, for starters. Then there's the brushless motor, which if you fly a lot makes the 5X longer lifespan a no brainer. Is it worth the extra 10 bucks a pop over the DS210CLHV? It would be to me, but it's not my decision.

Note; in the interest of full disclosure, there are two other mini-class servos, which are both considered overkill - but - that some amongst you may wish to investigate. These being the DS355CLHV (yes, 355oz-in of torque from a mini makes it a real monster) and the DS405BLHV. Both are considered complete and total overkill, but they exists for a reason, capice?

What's the best ProModeler servo for the Extreme Flight 69in wingspan Turbo Raven? As usual, and no surprise to the pros amongst you, the answer is . . . it depends!

Servo arms

Last thing; you're going to need servo arms and compared to chinesium alternatives, let me mention the PDRS32-25T, a beauty with an H-beam profile for stiffness, and made of 7075-T6 aluminum for strength.

Especially nice about the PDRS32-25T (a 1-1/4" arm) is you also get a clamp mechanism. So the conventional M3 bolt is for fixing it axially to the output shaft, plus the M2.5 machine thread bolt that clamps it radially to the spline shaft.

These two actions totally preclude the arm from working its way loose *and* also prevents any possibility of play between how well the servo arm is broached and how well the splines were cut by the gear hobbers. Think of this as a twofer, or as belt and suspenders for the control system.

And if you favor pull-pull action for the rudder, then we'll guide you to the PDRS34PP-25T instead of a tiller-type arm (opposed dual horns) . . .

So why a pulley? Simple, it's because pull-pull cables won't go slack transiting from one extreme to the other as much as when using a tiller arm! Only thing to watch out for is a) make sure the control horns align with the hinges, b) that you've snugged the figure of 8, and c) that it's a straight shot from the pick up points on the control horns to the plane of rotation of the pulley (meaning aligned with the groove of the pulley else the cable will slip out of the groove - duh).

Last thing, a) take a gander at this article about tips for improving your ARF because a) there's some more information about using a pulley, and b) with respect to leader cable, the really, really good stuff cable-wise is this 7x7 stainless leader (available on Amazon, and no, we don't do affiliate links with them).

Closing thoughts

In the end, with ProModeler servos you get better parts - from the individual components that make up the servo, like the alloy finned center case for better cooling, better gears, better potentiometer, o-rings, bronze hardpoints, potting compound, cap screws instead of el cheapo Phillips heads - everything about them is top notch. Plus you can get better servo arms, too! 

Still have questions? Call us at 407-302-3361 and we'll try to help you!

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