Bill, I mis-spoke....the rates given were way too slow. Where I said 12 it is actually 0.12 seconds. And that number is time to move 60° (typically). And typical excusions (end to end travel) are more typically 90°, and often go as high as 180°. 320°excursion is quite rare and expensive.
I also hope you will look around at optional vendor resources, as there are many, many places to buy servos. I'd also urge you to follow Don's advice about types conpatible with his little controllers, as it would apply to almost any other microcontroller-based servo control you find or design/build. I apologize for offering incorrect and potentially misleading data...it wasn't intentional, but was hastily done and careless of me. Cheers, Chuck --- In [email protected], "chuckcluff48" <chuckcluff48@...> wrote: > > > It seems everyone hovers around the brand that matches their radio or > their favorite customize your R/C for HOT action article. > > Futaba seems to be one of the most popular, but frankly, I haven't been > able to tell much difference. They come classified by traditional or > digital (I still use traditional, but may move over to digital when I > get time to better understand how to interface them.), they are > classified by holding torque, best end to end transit time and weight > (or size). They are often called, micro, mini, standard, large and very > large. > > A lot of the micro units go into HO layouts (as in the previously > referenced article). For larger loads and applications where more > holding torque is required (that also translates into power for > movement), you go up to larger, more powerful servos from there. > > As to quality, the cheapest ones, which are generally fine for most > railroad applications, you'll find the gears are all nylon or acetal > plastic and they use bushings (usually also plastic) to manage the > torque moment. For a somewhat higher price, you can get metal gears and > bearings, though for these applicatons there isn't enough movement over > the track lifetime to justify the extra expense for most applications > (IMHO). > > To see it in perspective, I have a set of old standard size servos in a > large R/C plane I built 23 years ago. They still work fine, even after > the plane got turfed (hard crash) several times, requiring a complete > main wing rebuilt each time. On one occaision a friend was flying it and > got confused about the attitude of the craft and plowed it in so hard > the only part that was intact was the instrument box in the main > fuselage. Because of the kind of construction I used, I was able to > completely rebuild the plane from the instrument box out. I never had to > replace any of the servos and to this day, they work fine. These are > the less expensive plastic gear servos that today run about $12 > (although I paid quite a bit more for them at the time). > > The message here is that servos are actually quite robust and somewhat > forgiving.....if you correctly size them to the application. To do that, > you must determine the amount of force required to move the object of > interest (large ailerons in the realm of 50" require considerable > torque, track switches require quite a bit less). That is why Don calls > out micro servos for his HO examples i his article. For S, I might > suggest a moderate mini servo. > > For the last three years, for non-R/C applications (I've hung up my R/C > gear for awhile), I've been buying most of my servos from HobbyKing > (link: http://www.hobbyking.com/hobbycity/store/uh_index.asp > <http://www.hobbyking.com/hobbycity/store/uh_index.asp> ). Now I'm not > promoting that business, but I am explaining what I've done and am doing > in the spirit of sharing information. You may prefer to buy local, or > have a favorite vendor you use....and that's just great. I buy most > stuff online, since I'm way out here at the end of the pole line in a > rural community and they just don't offer much in the local > establishments that I need for my various interests. > > HobbyKing carry a pretty good variety in almost all the available sizes. > Their EM 9g offers a 1.5Kg (about 53 oz-in or casually 3lb-in) holding > torque and a 12 second end to end transit time. Very adequate for most > small motion activities in a layout (and easily used for some lighter > switching in HO applications). > > For switches in S-Scale, I imagine something more like the Corona 939MG > for $4.30 offers nearly 5lbs holding torque, metal gears, ball bearings > and a 14 second end to end transit. I haven't tested that yet. If you > get a switch built up and can tell me the moving force, I can suggest > any number of servo options....and I'll bet they'll all be under $10. > > If you want to see someting really beefy, look into their BMS620-MG..... > metal gears and bearings, weighs less than 2oz (for you weight > watchers), 15 second end to end transit and 9.1Kg (that's 126 oz-inches > or, as I've casually been calling it, over 20lbs) holding torque. Um, > that's lb-in for any technical sticklers. The rating is always in Kg-cm > or oz-in at this scale. This one could easily turn an S-Scale swing > bridge of 120 scale feet. > > In the really big, as in "we need to build it, 'cause they don't make > them", you have to get into a little machining and find a good gear > supplier, use moderate, but larger motors, etc.. That's much more > involved and costly...but some folks like that "make it from scratch" > kind of thing. > > I confess to a certain amount of that....that's one reason I'm here. > Anybody can go to yon HO store, buy a bunch of ready-built stuff off > the shelf and assemble a very nice track and control system. I had a > friend that built a beautiful store window display in HO and N scales > completely from off the shelf purchases. The store was delighted and he > was well paid for a fun shopping trip and four days of painting, gluing > and wiring (with a little help on the electronics from yours truly). I > was not paid, since I owed him a favor. But it was fun anyway....and he > got well paid. > > These are great for scale action elements, because they can be > controlled at a scale rate (much slower than these transit times, > especially nice, since one usually only needs a portion of their total > "throw". Most will rotate at least 180 degrees, many as far as 300 > degrees. And, of course, if you take out some of the encased elements, > they just rotate (not really servos any more, but controlled with the > same electronics)..... > > Ad of course, they carry Futaba, if you want to have shiny buttons and > less cash in your pocket.... ;-] > > > > Now I've been a wee bit flip here (and gone on too long again), but I > hope this will provide a reasonable starting point for you and anyone > else that is interested in useing servos, but uncertain how to proceed. > > Best Wishes to you and all the group, > > Chuck > > > --- In [email protected], "Michael" <meldridge@> wrote: > > > > Any thoughts on durability of various brands? Is there a brand you > prefer? > > > > -Michael Eldridge > > > > --- In [email protected], "chuckcluff48" chuckcluff48@ wrote: > > > > > I can't actually make any claims to originality for the use of > servos > > > for active but non-rolling elements of a layout. I have considerable > > > other experience with them, but that is irrelevant here. > > > > > > > [Non-text portions of this message have been removed] > ------------------------------------ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/S-Scale/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/S-Scale/join (Yahoo! ID required) <*> To change settings via email: [email protected] [email protected] <*> To unsubscribe from this group, send an email to: [email protected] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
