Q. Have you ever compared an XXX100HV servo to ProModeler servo?
A. What's an XXX100HV servo? Honestly, there are so many Oriental manufacturers private labeling their servos for 'anybody' willing to buy 100 of 'em, it's hard (impossible?) for us to keep up. These days it seems everybody and their brother sees servos as a way to make a buck, to include hobby shop owners, folks selling Chinese ARFs, etc. But while they're busy chasing another buck, are they watching out for your interests?
Please allow me to share a thought. If you only look at price, torque, and speed then honestly, you're playing checkers. It's only when you begin to delve deeper that you begin to play chess. And by deeper I mean examining how the servo is actually constructed because this determines how well it will hold up. This becomes especially important when you're shopping against low bidder. Put another way, are you getting your money's worth, or are they trying to bamboozle you with a label? Since nobody likes getting ripped off, let me show you what to look out for when shopping servos.
In this brief read I'll try and help guide you about what's important, and what's not. Honestly, there's a lot to take in but after slogging through it, you'll be independent of the opinion of others - including mine - and most especially that of the so called forum experts. Moreover, few folks will bother learning all of this, so in doing so you'll immediately become the go-to guy in your club regarding servos! E.g. the one they can rely on for helping making sense of the smoke screens being blown left, right, and center in the servo business. Let's jump in!
1. Does this XXX100V have o-rings? Yes or no.
2. If it does, then how many? Ours have 13 o-rings in the assembly.
3. Are the o-rings fully captured like ours? Exposed o-rings are vulnerable. For an example of this, look closely at the photo below and take note of the tiny pocket into which the o-ring fits so when the bolt head bottoms, with the end result being it's totally encased (hidden).
4. Does it meet any MIL-STDS? Ours meet three, MIL-STD-810G-Part 16
- Shock - Test Method 516.6
- Vibration - Test Method 514.6
- Rain - Test Method 514.5
5, Is the center case aluminum? Yes or no.
6. If it's aluminum, is it finned? Cheapo servos may come with an aluminum center, but they're rarely finned and instead, what they do is play up on the fact aluminum dissipates heat without ever getting into the details about what cooling fins bring to the game (if they even know). So absent the cooling fins, you're only getting half the benefit of aluminum, maybe less. Here's the rub, if less than caring designer, or a private label servo guy buying someone else's work product only goes half way on this critical component, then what other short cuts are they taking to save a buck?
I wonder because money is the root of all evil, and cooling fins are a big deal for electronic component longevity. Think of other heat producing devices, like lawnmower engines, computer CPU and GPU cooling systems, etc. See any of them touting aluminum sans the fins? Didn't think so!
7. What about fasteners? Are they Allen-head, or Phillips-head? Teeny-tiny Stainless and/or Grade 12.9 Allen head bolts are pricey, much more so than Phillips head fasteners - but straight up - nothing is better.
8. This brings up an important point, do they use bolts or screws? Remember the difference; machined-thread bolts (like we use) are better than coarse screws, which may thread into either plastic (or soft aluminum in some cases).
9. But there's more. Like how many bolts are used to secure the gear assemblies together? For example, we use 6-bolts on the transmission segment plus 4-bolts for the electrical cover - 10 total - and not because they look snazzy but because the assembly (in effect a gear box, like a transmission in a car) becomes stiffer with six bolts versus four - even with some of our smallest servos! And stiffer is better because it means the opportunity for excess play and backlash to ever develop is greatly reduced. But it costs more money to develop for stiffness and spending more money in anathema to a private label guy, because that's not why he's in the game!
10. This brings up gears; 100% metal, or does it include a plastic 1st
gear? Believe it or not, my gear costs go down by half if just that one
little gear is made of plastic! I don't bite on the cost savings . . . but
11. This brings to yet another point regarding gears; some of our servos feature steel gears! Flat out, steel gears are the best. Nothing wrong with conventional metal gears (bronze/steel/aluminum gears) but steel is strongest - by far! Cost a lot more, too.
12. What's more, good gears are worthless if they'll go out of alignment over time, so this brings up an important feature; does the cheapo servo have bronze inserts? Honestly, without these hard points you end up with a significant weakness in the product design. Reduced durability, or more specifically, the lack of inherent toughness which is important because in the hands of hard flying pilot, the steel-gear-shaft-to-plastic-interface of an el cheapo servo simply experience accelerated development of excessive play (so that by around 50 flights, in the opinion of top pilots, they're effectively so worn you need to replace them).
13. What about the PCB? Is it protected for shock and vibration with potting compound? This is what's used for aviation components, for stuff going into out space, and in our servos. Pain in the ass to apply, expensive and takes more time - and time is always money? Yes, but totally worth it.
14. What about a conformal coating for moisture protection?
15. Next there's the question of the potentiometer. Is it a genuine 1,000,000 cycle unit Nobel (Japanese), or a clone? Or worse, is it a no-name oriental unit? Honestly, this little bit of mechano-electrical wizardry by my Japanese supplier costs 4X what an identical looking bit but from a Chinese supplier goes for (also with a claim of 1M cycles but which turns out to be bullshit).
Speaking of potentiometers, if one goes south will they sell it to you? Or will you get a song and dance? More importantly, do you trust some private label guy trying to make a quick buck to even know the difference between the potentiometers? Bottom line? Can he even answer the question regarding the supplier of the actual part? And do you trust him to pony up for the good one, or might he be opting for the cheapo?
16. Does the private label servo guy offer spare parts? Do they offer a repair service. And isn't this important as Hell to know before you buy?
Anyway, I pay the price of the superior Japanese pots for a reason. And frankly, you wouldn't know the difference for a year, or maybe longer (by which time your private label servo vendor is either shielded by the servo being out of warranty, or has changed his mind about the servo business altogether thus leaving you high and dry. Better to know this in advance! So one of the reasons I'm paid the big bucks is making decisions like whether to use the best pot, or the fly by night potentiometer to save a little dough because pennies add up to dollars.
17. And don't forget the motor, Japanese or Chinese? Ours are Japanese. Simply put, the precision and quality are unmatched by anybody else on the planet (and I have no domestic source at all). Anyway, I'm paying about 2.5X more for Japanese motors - this just to keep our standards at the very top. Does the guy slapping a label on a servo have a clue about this? Sometimes you have to follow the Benjamins to determine where your interests lay. The clues are out there and often you don't even have to disassemble the product to figure it out!
18. No disassembly required? It's true because sometimes it's the obvious stuff. For example, we have micro size servos offering 100 and 150 oz-in and guess what? We mount them securely by using 4-screws instead of two. Why? Simple, it's because we know you have to stop it from rocking on its mounts to preclude lost motion, or why bother getting precision servos in the first place?
But what about the guy selling private label servos? Does he even test for something as elementary as this before buying setting out to make money whilst being clueless regarding high performance servo design? Remember, top brands became so for working hard. It's been our route and you can tell just by the sheer variety of servos we offer (over 20) whilst the private label guys may offer a few. Thing is, many of these private label guys have outsourced their design to someone else. Usually someone more concerned about the almighty buck (and the easy making thereof). This, versus offering a product to be proud of.
We believe it's an open and shut case when outfitting your model, but this is a decision you get to make, and unless your money grows on trees, it's one that's important to get right! If you've read this far and grokked what you read, then congratulations for sloggin' through it all.
Details, or who who woulda' thunk a small touch like how many screws are used to mount a servo could be a tell regarding the product quality . . . one ultimately as important as the tell a poker player would play off of when betting big (if I may mix my metaphors).
Buying servos is like playing a game. The question is, are you one of those who plays checkers - or - are you at a higher level because you're playing chess? I've shared with you how to become a master at this game, e.g. how to judge if your money is being well spent. And all this, without my even needing to see the competing product!
And thus, now you can ably decide for yourself what's best for you. And you can do it without asking anybody's opinion. And the best part? You don't even need to be an engineer because anyone with eyes can look and check off these details for themselves. Remember, they say the Devil is in the details . . . it's true.
Anyway, to make it even easier for you, I've linked to a handy checklist, which is in the popular .pdf format. Print one page (you get four charts) and then go shopping. Compare our servos to theirs - and do it to your heart's content because you'll be secure in the knowledge you're now forevermore free of relying on the advice and opinions of others to spot when someone is trying to blow smoke up your skirt!
Last thing, I urge you to visit our website and poke around within the askJOHN section for more useful information about servos in general.