Hello listers. Try http://www.servocity.com/ServoCity/Products/Sprockets__Gears__Chain/sprockets__gears__chain.html for ideas on gearing up servos to get greater throw.
Remember of course that as you increase the throw you also decrease the thrust of the servo. Best wishes, Tony Walsham. Remote Control Systems. P.O. Box 1118 Bayswater, Vic 3153 Australia. www.rcs-rc.com Tel - North America: 1 800 490 6945 Tel - Elsewhere: ++ 613 9762 7785 On Wed, 04 Dec 2002 16:07:02 -0800, you wrote: >Hi Mike, > Sounds as if you are looking to increase effective control from the >limited servo movement?. > I have an assortment of various servo,s, and have used both the >following servo,s for steam engine R/C. For direct or indirect push pull, >or rotary controls. > Futaba S3102 Metal Geared @ 51 in oz 1.1"HT x 1.17 L. x .51" W. with >190degr movement. > Hitec FMS S90 Nylon Geared @ 30? in oz. 1" H X 1.17 L x .8" W. with >180degr. movement. > I also have a Roundhouse Elsa (Similar to Katie), which was supplied >with R/C controls. > This uses Hitec HS 81 Servo,s for throttle and Johnson bar. These also >have 180degr. movement. Servo uses a .5" long arm = 1" total stop to stop >travel driving to a .9" long arm at the throttle. The linkage arm is >positioned in the outermost hole of both crank arms. > Typically I run the Elsa at approx 30% open throttle, or 30% of full >movement available. Which is more than sufficient for "scale speed". > > I am not very familiar with the Frank S controls and cab space. >(It has been several "months" since our web mom visited one of my steamups >with his Frank?- Oops!). But also know he was busy building his own track!. > > However if you are looking for even more movement at the throttle, >etc., there are several methods you can use, as follows:- > e.g. For direct drive- Extend the "generic" .5" long servo arm to .75", >(or more), which would increase direct drive throttle movement from 1" >total swing to 1.5". This is probably the simplest method > Alternatively, for indirect drive add an intermediate pivot bellcrank >with a 1''? (or more) long arm, between the servo and the throttle, if you >have room for a stable pivot platform. Then drive from outer hole on the >servo arm to inner hole of bellcrank arm. Add a second link arm from outer >hole of bellcrank to throttle. The increase in total arm movement would be >the original servo arm length max-min swing plus the distance (total swing) >between the inner and outer holes of the bellcrank. > Third option would be quadrant gear and pinion rotary drive. But I >think this route may not be needed for the Frank. > > Effective Throttle Required:- Personnal Thoughts. > I suggest that most engines drivers think they must have the absolute >"maximum" amount of R/C throttle range as possible, at all times for >running, especially starting from cold, or with a heavy load. When in fact >a wide open throttle and max startup steam pressure, results in drastic >wheel spin, and is bad driving!. > Factualy, when engines are warmed up and with constant steam pressure. >They will re-start, run easily and fast even at a 20-40%? throttle opening. >So the initial 1"+ cold start servo throttle movements, have to be severely >cut back to approx. 25% for constant controllable running. In conjunction >with setting the Johnson bar % cut-off, if fitted. > Therefore designing a "manual" overide, which initially allows large >"hand" throttle movements at startup, but allows lower "running >throttle" R/C control is a better option, than trying to increase servo >movement for "excessive full range" controls, which may only be needed for >5-10% of the running time?. > This "manual servo overide" can be achieved using the same simple >spring loaded push-pull rod mechanism as used for R/C cars. i.e. for hand >"blipping" the throttle of high reving engines, prior to race starts. Or >adjusting clutch/brake mechanisms. > Using a custom tweeked spring loaded overide to give full cold start >throttle assistance has the advantage of also being a safety mechanism in >case of loss of R/C signal during running. i.e. in preventing the engine >running at over 40%? throttle in case of a signal loss. > > 2nd Thought- Running Light with R/C:- > How many steamups have you attended where the majority of steamers, >are content to run their engines 'light" with absolutely no load at all, on >10lbs pressure, 1/4 throttle for "hours". Typically some are free running, >but many still use R/C under these conditions also. Probably running down >the batteries faster than the water. Why?. > Could it be some designs cannot pull the skin of a rice pudding, even >with full throttle R/C?. > > 3rd Thought:- > Running a Big Boy "light" with a single load car representing "100 >actual" cars is even worse!. > Still having Fun, > Best Regards, > Tony D. >4/02 -0800, M Paterson wrote: >>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 >
