Tony I hope that this is not a repeat as my first message "dropped" before completed. Can you provide the make and model of the servo that provides 180 degree rotation? Every servo I have seen has a much smaller throw and I need the extra movement to operate the throttle on both my O'Connor modified FrankS and the Ruby.
Regards Mike Paterson --- Anthony Dixon <[EMAIL PROTECTED]> wrote: > Hi Walt, > Agree R/Cing engines needs "customized" design > detailing, per engine > type. Some easy, some a challenge. Especially the > larger but smaller scale > engines (1/32) with little excess cab room. > I was originally replying in broad terms back > to Geoff regarding > R/Controlling the throttle and blower on my U1, with > servos, etc in the > tender. > But to clarify a little, the hook up methods I > originally tried were as > follows:- > Flexible bowden cable- 1st Choice;- > Was ok for taking up the variances between a > full right and full left > curves on the track. But the cable "wound up" to the > extent all the servo > torque movement was absorbed in the flex, before the > throttle even turned > at all. Also could not fully close the throttle, or > open a closed throttle, > as the servo torque was absorbed in the cable. > (I did try several sizes). The stiffer cables, > also stiffened the > movement between engine and tender, causing > derailing. The lighter cables > "wound up". > > Rigid wire with female universal joint at one > end:- > Needed a slot > 5/8" along c/line to ensure > total swing movement, and > servo at 40 in oz did not have enough torque to > fully close throttle. (I > was twisting along the center line of the servo > shaft and throttle and with > only 1/4" max leverage. Not with additional lever > action). > > Also tried the sliding tube method, to account > for swing movement, in > conjunction with a 1" long "L" shaped lever into > servo arm to increase torque. > > Thought I may need full rotation, so I Increased > effective rotation and > torque by fastening a 60 tooth x 1" dia gear wheel > quadrant (cut in half), > to the servo, and drove a smaller 20 tooth gear on > the end of an R/C > wheels universal coupling drive rod. Plus a modified > universal female > socket at the throttle. i.e. 1: 3 ratio. > As the servo only rotated 180 degr, this still > gave 1 1/2 turns on the > throttle shaft, with enough torque to open a closed > throttle, and vice > versa. But still needed a separate drive for the > blower. > Incidentally, later tests showed that when > running under hand control > and warmed up, the engine needs less than 1/2 turn > between stop and very > fast. And is typically run at less than 1/8 turn on > the throttle. So any > slop in the linkage controls, quickly defeats the > purpose of R/C. Which is > why I went the gear drive route. > > Johnson Bar- Controlling this from the tender > was also going to be > another sliding rods problem. > > Finally decided I did not want three + servos, > and numerous linkages > between tender and engine. So found the smallest > physical servos which > would fit in the cab. Increased effective leverage > with longer moment arms, > and finished up with one servo pushing and pulling > the throttle and blower > in unison. I like to keep a little blower 1/32 turn > on when running, or for > unscheduled stops, as this minimizes any chance of > the flames blowing back > from under the firebox. This is adjustable by fine > tuning the control > clevis on threaded push rods > I plan on removing the rotating screw rod system > for the Johnson bar, > and fit a push/pull > quadrant. Again with one servo in the cab. > Regards, > Tony D. > The > >Some thoughts and observations on R/C for > alcoholics....er alky fired loco's! > >The Aster Mikado is easy to R/C. I made a little > fitting to go over the > >existing handle > >and connected via turnbuckle to the servo mounted > with a strip of blackened > >copper to the cab floor > >I have found I rarely need to adjust the blower and > have not put a servo on > >it yet. From an operational standpoint, Mr. > Lunkenheimer has decreed that > >road engines, i.e., K-4, Hudson, Mikado, etc. DO > NOT GO IN REVERSE! A yard > >switcher brings their consist to them and they > main line it from there. > >Geoff's observation about the degree of bending for > tender mounted controls > >can be overcome with a flexible piece such as piano > wire or the spring core > >material from old speedometer or choke cables (if > you are so inclined, you > >can buy a new replacement cable at K-mart, etc.), > etc. This works especially > >well if you are controlling the round "handle" on > many aster throttles. A > >fork at the end of the wire or spring goes through > the holes in the round > >handle, and a similar "fork" fits into a round > servo plate or the holes in > >opposing arms on the 2 or 4 armed attachments. > >Another approach is to use square tubes that > telescope with ball fittings on > >the ends since there is usually a straight line > path from servo to control > >even with the engine going around a curve provided > the extension can > >telescope. > >Really, it's a "piece of cake' -- dang, this diet > is killing me......... > >Keep your steam up! > >Walt & Lunk > __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com
