Micro Linear Servo as Switch Machine?

[C855B]

A few weeks back I mentioned this linear R/C servo as an idea for a switch machine using the Tam Valley controller. Well, the order came in this morning's mail.

These things are tiny!!! It looks like these might just fit with my thoughts of hiding the machine in the roadbed, Peco style. If they work, they're going to be tough to beat at $4.29 each.

[DKS]

I've found them that are almost half that size. The only shortcoming with the ones I found is the need to add limit switches because they do not have servo circuits and they are not "stall" motors.

[C855B]

Open to different solutions, Dave, since this project is still an experiment. Do you have a source you can recall? Every ultra-micro servo I have found so far uses that board, 'cept a couple which put the electronics out on the wire.

[DKS]

Open to different solutions, Dave, since this project is still an experiment. Do you have a source you can recall? Every ultra-micro servo I have found so far uses that board, 'cept a couple which put the electronics out on the wire.

Got them off the 'Bay--I'll try to figure out who. Anyway, I just examined mine and it looks to be the same design as yours, just smaller--and with no PC board underneath. It has electrical wipers on the slider, so it may explain why I got them so cheap. To me it's OK that they're not servo-style, as I'm more comfortable using limit switches and such--more versatile, with fewer wires and less electronics overhead.

[DKS]

Here's the really small one I've got:



I got a bunch of them just to do animation, but a switch machine would be a great application as well.

[peteski]

While I have no experience with these servos, Looking at their construction, I'm worried about their longevity.  After all, most train layouts are usually built to last at least half a lifetime. 

Those motors are pager-type motors, IMO not designed for longevity (you normally replace your cell phones every couple of years).  I dissected few of such motors and they have very delicate paper-thin metal brushes.  Also, some of these motors I own had their magnets swell (oxidize) after just sitting for few years unused, due to the humidity in the air.  It seems that the rare-earth magnets were not coated tightly enough and moisture got inside them

I'm also worried about those tiny nylon gears splitting after few years but this might be just becasue the Bachmann splitting nylon gears scarred me for life!

I would just hate to see someone install couple of dozen of these on their layout and after few years start having all sorts of problems. Yeah I know. I'm probably just paranoid.    After all, this type of motors is also used in all those tiny RC helicopters where they are under large stress while flying and they seem to survive longer than the rest of the helicopter.

[LV LOU]

While I have no experience with these servos, Looking at their construction, I'm worried about their longevity.  After all, most train layouts are usually built to last at least half a lifetime. 

Those motors are pager-type motors, IMO not designed for longevity (you normally replace your cell phones every couple of years).  I dissected few of such motors and they have very delicate paper-thin metal brushes.  Also, some of these motors I own had their magnets swell (oxidize) after just sitting for few years unused, due to the humidity in the air.  It seems that the rare-earth magnets were not coated tightly enough and moisture got inside them

I'm also worried about those tiny nylon gears splitting after few years but this might be just becasue the Bachmann splitting nylon gears scarred me for life!

I would just hate to see someone install couple of dozen of these on their layout and after few years start having all sorts of problems. Yeah I know. I'm probably just paranoid.    After all, this type of motors is also used in all those tiny RC helicopters where they are under large stress while flying and they seem to survive longer than the rest of the helicopter.

Servos usually have very high quality motors.They take a terrible beating.Every time you reverse direction,literally,hundreds of times every time you fly/drive an R/C vehicle,the motor has to stop dead,and instantly reverse direction,they have to be built to take that abuse.I've been into R/C racing and flying since the late 70's,I really don't ever remember a motor on a servo burning up.In fact,I used to use the armatures from the few that the boards dioed in as upgrade replacements in HO slotcars for years..Being used as a switch machine would be like a vacation..

[DKS]

...(you normally replace your cell phones every couple of years)...

And not because the vibrator quit. You replace the phone to upgrade to the next version. I used to scavenge vibrator motors from old pagers and cell phones back before you could buy them new for less than a buck, the way you can now, and I've yet to have a pager motor die.

...Being used as a switch machine would be like a vacation.

Agreed.

[SkipGear]

Here's the really small one I've got:



I got a bunch of them just to do animation, but a switch machine would be a great application as well.

David,
 You have just the replacement mechanism for his servo above. There are a few different sizes of that style servo. long travel, high torque, high speed, etc. They are used in the better micro helis and planes. I fly a few planes that use them and the latest generation are amazingly fast for their size. It is rare that the motor dies but the mechanism do fail periodicly. The gears are very fine and easy to strip gears just by running them to the end points.

They would definitely have enough power to throw turnouts. You would probably want some sort of spring over ride on them though. The one thing nice about them is that they are worm drive so wherever it stops, the motor doesn't have to hold agains the resistive force so the motors last longer. In a normal servo, the gear train allows you to fight the motor with external force making the motor have to work all the time.

[C855B]

Yep - that motor/gear/worm thingy is exactly what's on some brands that use the servo board. The motor on the Hobby King servo is just a little longer.

I don't see any issues with longevity, or at least longevity from wear and tear. Duty cycle on a switch machine is like nothin', and Tony's observation that the worm drive trumps loopback position holding (provided the Tam Valley controller works that way!) is a big plus. I have an N-Trak module ready for track, so it's going to be my test rig.

[VonRyan]

  Don't get those too close or i might wants to buys me somes... Albeit those would be great for my Nn3 layout that I plan to be not only a stand-alone but an N-Trak attachment as well... those might be more gentile on Handlaid code 55 turnouts as opposed to one of my NJ International twin-coil "bang-bang" machines...

hmm...

-Cody F.

[DKS]

David,
 You have just the replacement mechanism for his servo above...

Ah, that explains things. Good that they sell just these parts, because for my applications the servo circuits are unnecessary.

... those might be more gentile on Handlaid code 55 turnouts as opposed to one of my NJ International twin-coil "bang-bang" machines...

After I stopped using commercial stuff like early Trix and Atlas Snap Track, I've never used twin-coil machines on any layout. I've either used a Tortoise, a DIY slo-mo, or a manual throw. I just think twin-coils are way too hard on N scale track, especially handlaid.

[TiVoPrince]

Wondering  
if a rather unbalanced length fulcrum is the answer.  Insert a lever similar to that on a Tortise machine yet much shorter overall.  Could still be embedded into roadbed or attached directly to turnouts in some sort of fairly stealthy way...


 \|/ 30% of fulcrum
  0  Pivot
 /|\ 70% of fulcrum to absorb addtional thow
[-S-] Servo

[alhoop]

I've found them that are almost half that size. The only shortcoming with the ones I found is the need to add limit switches because they do not have servo circuits and they are not "stall" motors.

David:
What size limit switch and where do you get them. Was it ever decided whether the motors on
the on  like you have would burn out if used like a stall motor?
Thanks
Al

[DKS]

If anyone is interested in just the mechanics, and not the whole servo, here they are: http://www.ebay.com/itm/E-Flite-EFLH1066-Replacement-Servo-Unit-Short-Throw-ParkZone-Ultra-Micro-J3-Cub-/390437132664?_trksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D27%26meid%3D445651085689721540%26pid%3D100033%26prg%3D1011%26rk%3D2%26#ht_2771wt_1163

Note that you will need to add limit switches or else they will tend to self-destruct.