Topic: Set up for Rudder servo/linkage.

[paul swainson]

Most servos have a movement of 180 degrees, so when setting up the position of the servo what rules should be used.   I have a problem with very poor movement of the rudder in my Perkasa.   Both rudders are drilled into the hull about 20mm from the stern.  This leaves very little room for movement between the rudder spindle and the stern of the boat.   I have linked the two arms with a connection rod with both rudders central to the hull.   One arm on the rudders is longer then the other. I have positioned the servo the the far left of the hull (as you look to the stern) with a short link to the furthest away rudder tillarm.   So when the rudder is moved the arm on the servo moves through a 90 degree's swing pushing the rudder tiller only about 10-15 degrees.   I do not seam to be able to push the arm to get at lest a 30-40 degree angle from the center line.  Can any one help with an a layout plan or rule to follow?

Paul.

[mikearace]

You can adjust the swing more by varying the hole that the connecting rod goes into.  The servo arm travels more, and less, when it is in either the outer hole or the inner hole.  This applies to both the servo arm and the tiller arm. Before you do anything I suggest you try moving the linkage rod to the outermost servo hole and the innermost tiller arm hole.   If you have tried this already and I'm stating the bleeding obvious then apologies.

[colin]

Mike is correct.... as far as more movement of the rudder by changing the the position of the linkage (inner hole on servo less movement of rudder)

but if i have understood you correctly Paul....

your talking about a different problem...!!

you have two rudders ? and there both connected to the Servo ??  if yes, that is not a good idea..!!

the two rudders should be linked to gether, then from one of the Rudders the linkage should then go to the servo
hope the attached picture helps

[paul swainson]

I have attached a photo of the set up just now and have moved the tiller arm to the other rudder with no effect.
Paul

[paul swainson]

second photos better size to view i hope

Paul

[colin]

Hi Paul,

the set up is nearly correct...
servo at the furthest point, now you will have to move the connection on the rudder closer to the rudder post..
you might have to move the servo further to the rear transform, so the linkage remains reasonably straight...

[paul swainson]

Thanks for the information, will try moving the rudder connect closer to the rudder.   I was wondering if there is a longer servo arm to which I could use or a 90 degree angle rudder arm.   This may help with pushing the rudder arms futher over to increase the angle on the rudder.  I have used the standard 4 arm control cutting off one arm.  If there was an arm which is longer by 10mm this may help.

[mikearace]

Colin is right from the pic in that you have the linkage to the servo arm on the furthermost point of the servo arm but there is no room to manouvere it so as to result in more circumference travel than where it is now.  To do this you would need to maybe move the servo.  Or,  I suggest you maybe want to try and discard that linkage to the servo arm and between the tillers, leave the servo where it is and use piano wire to link the servo to the tiller and then to each tiller in the closer holes to the rudder shaft.  Not sure if that makes sense but I think I understand what I am saying.  That will allow you to experiment with each hole to see how much extra throw you can get.

[colin]

I was wondering if there is a longer servo arm to which I could use or a 90 degree angle rudder arm.

Yes Paul, would be the answer.

there are lots of ways to lengthen the Servo arms or use a 90 degree tiller...

Tiller Arm not to sure of the size of your rudder post, from the photo it looks as if its 4mm..

for your set up... i would first try and get some different tiller arms... make the linkage between the rudders on the stern side of the rudder post, and then the servo to rudders on the front side of the rudder post, as in the drawing..

[paul swainson]

@ Mike, Will remove the arm from the servo, and the connecting rod to the rudder arm.   Then connect the servo using wire to each each rudder arm starting from the closes and work my way to the furthest and measure the throw.   Got that, so what do I attach to the servo to hold the wire, a four arm or 6 arm servo control arm?

@Colin,  When I look on the internet there does not appear to be any measurements given for servo or rudder arms.   Do you know of a site that may make them to suit?   Your diagram is great but I do not have the space at the back of the rudders to link them as per your diagram.   I might look at making a smaller connection to the rudder which may leave enough space to fit a connection, but I feel there is not enough room for this., the connection has to be in the front.

Thanks guys for the help in this matter.

Paul.

[colin]

Robbe do some thing that would sort the problem out... it fits on a 3 and 4 mm rudder post

http://www.robbe.de/anlenkhebel.html

sorry the website is in German, but i am sure that a model shop in the UK has them or something similar...

[colin]

another way... to solve the problem would be to move the servo...

[Jeremy]

Don't know if this helps but attached are a couple of photos of my Dark Biter rudder set up. I imagine its fairly similar in space to the Perkasa. Seems to work ok but not tried out on water yet. You can alter the amount of travel by moving the pushrod in/out from the pivot point on the servo  and the rudder linkage. If I remember correctly if the pushrod is fitted to the farthest point on the servo arm and the nearest point on the rudder are you get the most movement (bit like the gears on a pushbike) however it can over turn and jam so I'm afraid trial and error

ps sorry picture of showgirl added by mistake though similar set up

[Jeremy]

Also forgot to add that these tiller arms are from Cornwall model boats not the ones supplied by nautical marine models.

They are longer so give more room for manoeuvre (sorry for the pun)

http://www.cornwallmodelboats.co.uk/acatalog/tiller-arms.html

and suit 3mm or 4mm shafts. The connectors are from SLEC and are standard aircraft aileron/rudder ball joints

[kit]

Sorry to maybe reopen an ancient topic but only just found the 'top tips' section.

Colin

you have two rudders ? and there both connected to the Servo ??  if yes, that is not a good idea..!!

Can you explain why not?  I did on a Rothesay a few years back and it works fine - servo about six inches in front of the rudders, one arm pushing, the other pulling.  The reason I ask is that I'm just putting another twin screw twin rudder arrangement together and don't want to repeat a mistake!  The linkage goes under the mortar well but the attached should give a general idea of the layout

Thanks

Kit