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Old 08-24-2016, 09:54 AM   #1 (permalink)
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Default S420

Not really a heli servo but i noticed the S420 servo is gone from audacitys website, been discontinued or being replaced????
Say "Ya" to da U.P eh!?!
I drive WAY too fast to worry about cholesterol................
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Old 08-24-2016, 10:00 AM   #2 (permalink)
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Location: Upper Peninsula, MI

I see its back up as version 4....wonder if the backlash in the gears thats was noticably present in the v3 has been fixed?
Say "Ya" to da U.P eh!?!
I drive WAY too fast to worry about cholesterol................
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Old 08-25-2016, 12:07 PM   #3 (permalink)
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Oops, human error (mine) led me to forget to switch on the S420v4 when switching off the S420v3. Thanks to your eagle-eyes and heads up we've corrected the problem Thank you, Will, I appreciate it. Meanwhile, this S420 revision history may offer insight into it's development.

Revision History

S420 - we released the S420 (420oz-in) in November 2013. This digital HV-servo offers dual ball bearings, an all-aluminum case, metal gears, and importantly, a brushless motor. It's a re-geared version of our S245 helicopter servo and we price it aggressively at $79.99 against competing servos like the JR 8711HV costing $199.99. We can do this principally because of fewer middlemen (versus it costing any less to make). Feature-wise, the JR 8711HV has a coreless motor (cheaper) but more expensive gears (steel). We figured this was a wash and opt for the better brushless motor because of 5X longer life and lower power consumption - no brainer. Immediate success followed and our only problem was making them fast enough because modelers aren't stupid (2-1/2 servos vs. 1 servo represents a great value).

S420v2 - this decision comes back to bite us on the ass because by late 2014, pilots flying IMAC maneuvers report the metal gears aren't making it through a full season. They'd adopted the servo because of a great reputation for centering (and because fully equipping their plane with 7 servos cost them less than buying 3 of the JR 8711HV servos). But in not opting for steel gears we'd made a mistake. While we're rather proud they're using them in the first place because it means our design and price strategy are working, we have to scramble to address the wear concern (remember, our experience is with helicopters where the loads are greatly reduced in comparison). Also, first tier pilots (sponsored) replace gear sets yearly (routine maintenance, especially because they're free to them). However, our customers are sponsored by MasterCard so when worn gears samples elicited a supplier-response basically saying, 'this is why we sell steel gear sets', we saw no choice but to opt for steel gears (putting paid to our hubris in thinking we were smarter than JR or Futaba). Next, we laser etched Steel Gears on the sides (so folks could tell them apart), and set forth to do battle again - this in early 2015.

S420v3 - along the way we'd gained another type of customer - crawler drivers. Unlike pilots flying 40 lb models with 150cc-engines, these guys hammer 15lb rigs against immovable objects. And not content to merely abuse the gears . . . some actually break them! The fix was larger gears, which benefits IMAC competitors, too. The rub was we wanted 'really' larger gears and this meant our supplier didn't have an off-the-shelf offering. In turn this led to our first foray into custom steel gears! However, taller gears also meant the original case wouldn't work so this present the opportunity to revise it. This is when we incorporated fully captured o-rings and finned the sides. And with gears made to our specs, we redesigned the potentiometer drive by using steel pins instead of plastic pins and extended the splined shaft portion to increase case clearance with the servo arm. We released our new S420v3 flagship in late 2015.

S420v4 - by mid-2015 pilot reports of excessive backlash resurfaced. However, this time the hobber reported gear-wear well within spec. Hmmm, we're baffled because the bore centers are correct and if the gear wear is within spec, why are we getting excess backlash? The critical clue came when a crawler owner returned his S420v3 for potentiometer repair due to water intrusion. This presented an opportunity to disassemble and measure a servo we knew had suffered accelerated wear (rocks are harder than air). We're shocked to realize the bores (where the steel gear shafts fit in the aluminum top case) are loose, and not because of manufacturing-error but because under extreme stress, the aluminum itself deforms. It basically becomes pear shaped under the extreme pressure exerted by the steel gear-shafts! In turn, this allows the gear shafts to wobble - end result is excess backlash - who'd a thunk? Especially because the other guys choose instead to fit their gears really tightly (and simply offer replacement gears for sale when they wear in too much). Fortunately, we had an easy fix; this one merely involving a brass insert thus creating a hard point for reinforcement (just like we do for our plastic servo cases). Nobody else in the world does this - who wants the over on how long it takes Oriental manufacturers to copy us? Anyway, after a minor case redesign (for the larger boss to accept the hard points) plus slight reprogramming of the CNC mill, we began making our now super duty case and re-released our flagship - this time as the S420v4. That was early June 2016 . . . and so far, so good - yipee!

To be honest, I hope like Hell this version proves good enough because every time we have to make a change to the design it costs us money to recoup it. Are we done? Dunno but we really cannot think of what else will improve this servo - but know this - if someone experiences failure, we're not too bullheaded or proud to learn the lesson and apply it with alacrity. It's called progress and we've come to understand why each Porsche 911 looks so much like the previous year's model yet their engineers constantly find little ways to improve it - same for us. And not that we're in their league but we'd like to think we're not letting the grass grow under our feet, either.
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Old 08-26-2016, 08:37 AM   #4 (permalink)
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^^ You need not look further for the reason why I will always be an Audacity customer!
"I don't care that they stole my idea, I care that they don't have any of their own" - Nikola Tesla
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