mikemcE
I wanna be Dave
I believe the potentiometer shaft, all others use plastic pins. Also updated the bearings and gears.
John is the real deal, great guy, fantastic vendor, great service.
I would buy more if I needed another servo hands down
http://www.audacitymodels.com/Products/PDRS420v4/Default.aspx
Revision History
S420 - we released the S420 (420oz-in) in November 2013. This digital HV-servo offers dual ball bearings, an all-aluminum case, titanium 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 - a 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 - the decision to not use steel comes back to bite us on the ass because by late 2014, pilots flying IMAC maneuvers report the conventional 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 giant scale competitors are 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). Moreover, first tier pilots (sponsored) replace gear sets yearly. For them, it's routine maintenance (especially because new gears are free to them). However, our customers are sponsored by MasterCard, instead and thus, we saw no choice but to opt for steel gears (putting paid to our hubris in thinking we were smarter than JR or Futaba). However, along the way we had also discovered titanium gears doesn't mean the gears are made of titanium. Silly us, what were we thinking in believing the supplier? The story is, however more a failure to communicate rather then an attempt to deceive because to the supplier, titanium is their way of saying 'gray' . . . e.g. gray color anodizing (versus red or blue anodizing). Turns out titanium is a poor choice of material for gears (may as well use blocks of cheese for all the good it would do to use actual titanium) so we switch to steel, change the file to laser etched Steel Gears on the sides instead of Titanium (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. Another rub had raised its head, literally. The downside of using stock gears instead of custom gears is we use an o-ring to seal the case where the splined shaft exits and the thickness of the rubber o-ring subtracts a tiny bit from how much splined shaft sticks out. What we learned is some servo arms rub the case, which naturally enough affects centering. We let our customers know and recommend either owners of the v1 and v2 servo remove a bit of material form the undersides of the servo arms, or insert a tiny washer as a spacer between the top of the splined shaft and the servo arm before installing the bolt to create a little bit of clearance. Anyway, our v3 with custom gears resolve this altogether because we designed the entire gear and thus, we made the spline long enough to preclude this ever being an issue again. 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 . . . and aren't compressible). 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 pressure exerted by the steel gear-shafts (just like hammering a nail through a beer can). 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, we 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.
Super duty reinforcement - brass inserts in aluminum where steel shafts fit
Hang up and Drive
John is the real deal, great guy, fantastic vendor, great service.
I would buy more if I needed another servo hands down
http://www.audacitymodels.com/Products/PDRS420v4/Default.aspx
Revision History
S420 - we released the S420 (420oz-in) in November 2013. This digital HV-servo offers dual ball bearings, an all-aluminum case, titanium 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 - a 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 - the decision to not use steel comes back to bite us on the ass because by late 2014, pilots flying IMAC maneuvers report the conventional 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 giant scale competitors are 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). Moreover, first tier pilots (sponsored) replace gear sets yearly. For them, it's routine maintenance (especially because new gears are free to them). However, our customers are sponsored by MasterCard, instead and thus, we saw no choice but to opt for steel gears (putting paid to our hubris in thinking we were smarter than JR or Futaba). However, along the way we had also discovered titanium gears doesn't mean the gears are made of titanium. Silly us, what were we thinking in believing the supplier? The story is, however more a failure to communicate rather then an attempt to deceive because to the supplier, titanium is their way of saying 'gray' . . . e.g. gray color anodizing (versus red or blue anodizing). Turns out titanium is a poor choice of material for gears (may as well use blocks of cheese for all the good it would do to use actual titanium) so we switch to steel, change the file to laser etched Steel Gears on the sides instead of Titanium (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. Another rub had raised its head, literally. The downside of using stock gears instead of custom gears is we use an o-ring to seal the case where the splined shaft exits and the thickness of the rubber o-ring subtracts a tiny bit from how much splined shaft sticks out. What we learned is some servo arms rub the case, which naturally enough affects centering. We let our customers know and recommend either owners of the v1 and v2 servo remove a bit of material form the undersides of the servo arms, or insert a tiny washer as a spacer between the top of the splined shaft and the servo arm before installing the bolt to create a little bit of clearance. Anyway, our v3 with custom gears resolve this altogether because we designed the entire gear and thus, we made the spline long enough to preclude this ever being an issue again. 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 . . . and aren't compressible). 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 pressure exerted by the steel gear-shafts (just like hammering a nail through a beer can). 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, we 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.
Super duty reinforcement - brass inserts in aluminum where steel shafts fit
Hang up and Drive
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