Posted by: kit« on: 16 January 2015, 16:51:33 »Thanks Colin, very clear - I will have a think. I never go flat out astern except to take way off in case I swamp it but you can never foresee what you will may have to do to avoid a collision....
Cheers Kit Posted by: colin« on: 16 January 2015, 05:42:21 »Hi Kit
No Need to be Sorry, that's why the Topics stay here, so they can be reopened if needed..   I say that its not a good idea..! does not mean that you can not do it that way, it means that there might be some fall backs.. depending on the throw of the Servo and the positions of the linkages between Servo and Rudder. what can happen: when driving astern, and a full (hard left or right) rudder command is given one or both of the rudders can go past the Servos throw point, which means that the rudders would turn round and face the wrong way... thus giving you no control over the ship any more... I hope I have written this so it is understandable... this happened to me once in my boating career, since then I connect my Servos to rudder with double linkage.. see my builds http://www.deansmarine.co.uk/index.php?topic=144.msg771#msg771 Posted by: kit« on: 15 January 2015, 19:39:21 »Sorry to maybe reopen an ancient topic but only just found the 'top tips' section.
Colin Quote 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 Posted by: Jeremy« on: 28 April 2012, 13:22:28 »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 Posted by: Jeremy« on: 27 April 2012, 10:25:31 »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 Posted by: colin« on: 24 April 2012, 18:27:40 »another way... to solve the problem would be to move the servo...
Posted by: colin« on: 24 April 2012, 18:11:01 »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... Posted by: paul swainson« on: 24 April 2012, 17:47:37 »@ 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. Posted by: colin« on: 24 April 2012, 06:20:39 »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.. Posted by: mikearace« on: 23 April 2012, 19:51:55 »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.
Posted by: paul swainson« on: 23 April 2012, 15:58:20 »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.
Posted by: colin« on: 23 April 2012, 12:51:47 »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... Posted by: paul swainson« on: 23 April 2012, 12:16:08 »second photos better size to view i hope
Paul Posted by: paul swainson« on: 23 April 2012, 12:11:13 »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 Posted by: colin« on: 23 April 2012, 10:18:13 »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 |