Linear Servos....

Nodrog1826

Nodrog1826

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Has anyone out there had any experience with linear servos?

Came across them whilst looking into ordinary servos, considering using one to operate a coach roof pantograph, in conjunction with a function chip.
 
No, but I'd like to see one. Hopefully someone here will be able to answer your inquiry.
 
I recall using linear servos many, many years ago (40+ years!) when i was into R/C model boats.... all they were was a standard servo with a different "top" to the casing, with two slots in it. The rotating servo shaft had a pinion gear on it, which engaged with two short rack gears running in the slots, each of which had a two-hole servo "arm" sticking up through the slot, so that as the servo turned one arm pushed as the other pulled - but in a linear fashion rather than a rotating motion.
Their only real advantage over a standard rotary output servo was that is was a straight-line push/pull motion so that the rod or whatever you had connected moved in a straight line rather than swinging to the side at all, which had some advantages in very cramped operating locations; it also might make it very slightly easier to mount a microswitch or similar to operate at the end of the arm travel.
I'm assuming that today's versions are on the same principle as the old ones I used?

Jon.
 
Sure it was on this site that they were used to open concertina doors???
I asked for more details, and a picture of a slim rectangular unit was posted. - Though nothing to give an idea of scale/size.
I was under the impression the unit shown had a micro-motor in it, so was smaller than a normal servo.
 
I purchased some linier servos a while back (several years) and never got around to using them. I did connect one to an eMotion 8FL though. I was playing with Pantographs around that time with my DB110. As you can see, the ones I purchased are not that big!

2015-12-29 15.20.50 (Small).jpg
 
Hmmm, a neat little thing, Mark - do you recall what make it is?
Very different from the clunking great 1970's ones that I described above - Ye Gods, what R/C modellers at that time would have given for servos the size and weight of today's.... ;)

Jon.
 
Mark..

I recall the video you posted on You Tube at the time.

All options are still open, micro, linear, normal servos, even fitting the missing LGB mechanics (Bit of an expensive option.) Still need to figure out how to allow for compression of the pantograph when raised.

One thing that is certain, will still need a function chip, may as well connect the various coach lights at the same time.
 
Have a look at these ones:

http://www.firgelli.com

They can plug right in like a regular servo.
You could use a Massoth 8FS, then use it to open and close the coach doors while you're at it! :-)

The r/c airplane shops will carry those really little ones like your picture-- I know the Parkzone or Eflite ultra-micro planes use them.

Keith
 
I wonder if anyone has tried these in Live Steam Locomotives. I would have thought that they might work well or even better then the normal type for Regulators and Revercers.

Am having a bit of problem with one of my Roundhouse Locomotives, so am going to try a Couple of these beasties in it to see if they work OK. Have ordered 2 from the UK Link.
JonD
 
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Just be aware of the 'weight of throw' for these.. - Not sure of the proper term??
They are 1.5g (which I assume means they would lift, and hold, a 1.5 gram load). - How 'stiff' are the regulator and reverser?

NOTE:
Comment for those in the first link. Not the Firgelli units.
 
1.5 g is the weight of the servo (1.8 g including the wire & plug). The servo ratings are as far as I know always specified as torque, in this case for the Goteck linear servo it is 0.2 kg/cm. This rating can then be compared to the torques of traditional servos, i.e. a Robbe 8g micro servo has a 0.8 kg/cm torque at 4.8V (1.3 kg/cm at 6V), so the Goteck linear servo is not very strong. There is also some backlash in the screw, and the throw is not very long.
 
Thanks for the clarification..

I also found an ?8 channel? DCC servo driver board ages ago.. I sort-of had it bookmarked in the old Forum, so have lost the link/reference..
It might well have been a MERG / DEMU / Sprogg related item??

I even 'borrowed' some servos from my neighbour (he into R/C planes), and started 'playing'.. I was then after a capstan servo, but their size (and cost) put me off..
 
Sort od bumping this topic....

Looks as if I am going with a rotary servo, have got a function chip on order, when it arrives, will be off to a model shop look at small servos, and pick their brains.

btw,

Does anyone have any idea where I can get some non electrical fine gauge wire, considering this as an alternative to an ohmega loop to allow for pantograph compression when raised.

Recall it been used on a Crok to raise/lower servo pantographs, there was an article on how to do this in German, but carn't find it now.
 
Nodrog1826 said:
Sort od bumping this topic....

Does anyone have any idea where I can get some non electrical fine gauge wire, considering this as an alternative to an ohmega loop to allow for pantograph compression when raised.
Click to expand...

A model shop dealing with model aircraft may be able to help. I guess some model aircraft may use it to control flaps and similar features.
 
Food for thought, thanks guys :wondering:

Had been considering fishing traces.
 
Now, do you mean 'piano wire'? - Which is stiff, and springy..
Or 'memory wire' which can be 'trained' to always go back to a certain shape?
 
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