Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: How do I connect this to a servo?  (Read 3823 times)

barriew

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,012
  • Location: Thaxted, Essex
How do I connect this to a servo?
« on: December 23, 2008, 01:15:45 PM »

I have a length of flexible nylon 'rod' in a conduit that I would like to use in my current model to operate the rudder. I think this stuff is used by aeromodellers, but how do I connect it to the servo and rudder arms? Are there special connectors?

Thanks for any assistance.

Barrie
Logged

amdaylight

  • Guest
Re: How do I connect this to a servo?
« Reply #1 on: December 23, 2008, 01:31:03 PM »

I would go see your friendly RC Air Craft Hobby Shop, and look at either Dubro products ( http://www.dubro.com/hobby/ ) or Sullivan Products ( http://www.sullivanproducts.com/index.htm ), both manufactures a whole line of perfect little connectors for just this application. I would start with a 2/56 threaded rod and then screw a  2/56 clevis on it and then clip the clevis over the control arm, at the other end I would use a ball link to the servo arm. This is a fairly common way of hooking up control surfaces in RC aircraft.

I hope this helps, if not let me know

Andre :-)
over yonder in Portland Oregon
Logged

andyn

  • Guest
Re: How do I connect this to a servo?
« Reply #2 on: December 23, 2008, 01:41:01 PM »

You remove the inner, get a nylon or metal snaplink and epoxy the extender to the end of the inner tube, then cut the outer to the legnth you want, about 1/2 to 1 inch shorter than required, then cut the inner to the correct legnth, you then need another snaplink, put the inner back inside the outer, and epoxy the other extender to the other end of the inner.

The Snaplinks themselves screw on to the extenders once you are done.

The outer needs to be firmly expoxied onto whichever surfaces you can, otherwise they will just bend and induce a lot of slop into the linkage.

What you need:
http://www.ripmax.com/item.asp?itemid=F-RCA122&Category=010

What it will end up looking like, note this has two outers for extra stregnth due to it being the elevator control on a 110 inch wingspan glider. Sorry for blurryness
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,065
  • Location: Melbourne, Australia
Re: How do I connect this to a servo?
« Reply #3 on: December 23, 2008, 01:42:33 PM »

Barrie,

There are several possibilities.  
What the makers intend is that you use a short length of threaded rod (2mm or an american size)  You screw the rod into the inner snake and then screw a clevis (or ball connector) onto the exposed end of the rod - locking with a locknut if you feel like being very secure

Or you can use a pushrod connector - length of wire with a threaded end.  Thread the end into the inner snake and either bend a z-bend in the wire to fit through the rudder arm or whatever, or pass the wire thru a screw-clamp connector.

Or....  Sorry, I don't know how familiar you are with connection fittings - there are several other possible solutions but I wouldn't like to try and teach you to suck eggs.

How long is your route to the rudder?  These gadgets are famous for expanding and contracting more than the frame they are in.  This won't worry a boat driver much (but it sure makes model flyers sweat), but please remember to support the "outer" at (at least) both ends and have as little inner sticking out as possible  (to support the outer - glues don't like to stick to it - wrap with masking tape before gluing)

These are links to the sullivan site - the ones you have got are not Sullivan, but the instructions may help
http://www.sullivanproducts.com/S503Nyloncontrolset.pdf
http://www.sullivanproducts.com/GoldnRodContent.htm

Lubricate with water or silicone lube, or one of the oils for model racing cars made for plastics

Give it a whirl and keep asking!
andrew
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,065
  • Location: Melbourne, Australia
Re: How do I connect this to a servo?
« Reply #4 on: December 23, 2008, 01:44:06 PM »

GOOD GRIEF - The massed Bands of the Andrews have replied!

Lets have it as a harmony next time, bach
Logged

andyn

  • Guest
Re: How do I connect this to a servo?
« Reply #5 on: December 23, 2008, 01:48:19 PM »

im sure makes model flyers sweat

Funny you say that actually, one guy turned up to our flying club with some of these in an aerobatic Extra, the connections moved more than the control surfaces did....

GOOD GRIEF - The massed Bands of the Andrews have replied!

We have indeed, we're a mass model boat crimefighting team... We'll have the uniforms ready for llanberis next year :-))
Logged

barriew

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,012
  • Location: Thaxted, Essex
Re: How do I connect this to a servo?
« Reply #6 on: December 23, 2008, 03:29:49 PM »

Thanks the Andrews (and amdaylight) - I guess what I have is not what I thought it was as the inner is solid so no possibility of screwing anything into it :((

I'll have think about it and see if I can make use, otherwise its back to a solid link.

Barrie
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,065
  • Location: Melbourne, Australia
Re: How do I connect this to a servo?
« Reply #7 on: December 23, 2008, 04:11:54 PM »

Barrie

Two things:
1 - amdaylight is an Andre, so he is one of the massed band :}

2   didn't realise it's solid - the threaded links are also made with an internal threaded sleeve with a male thread at the end - thread it into the  female thread as far as possible.

alternative - find a tube that fits over the inner tightly.  Solder one of the threads (M2 or 2/56) into one end and fix the other over the solid inner.  Fix the adaptor by glueing, crimping or cross-drilling and putting pins through - or best of all - all of the above!

Do you need the length or flexibility?  You could easily run pull/pull cables made of dental floss through the outer tubes of this stuff and do a pull/pull rudder - this will circumnavigate all manner of obstacles and is pretty scale as well!  Only essential is that the rudder arms should be the same length as the servo arms.

Is there an excellent reason why you are not sticking the rudder servo right next to the tiller?  I do this and have never regretted it - you can generally poke a screwdriver in and remove the tiller bolt if necessary, and I attach the servo to the underside of the deck with double-sided tape - it can be peeled off if essential.  It has never been necessary to dive in and perform surgery - servos now are cotton-pickin' reliable

andrew
(percussion)
Logged

barriew

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,012
  • Location: Thaxted, Essex
Re: How do I connect this to a servo?
« Reply #8 on: December 23, 2008, 05:54:36 PM »

Thanks again Andrew. The reason for trying to use a flexible link is to avoid a solid link with 4 bends in it O0 The Servo needs to go forward of the aft well as there isn't room aft, and access would be difficult if I could squeeze it in. (See http://www.modelboatmayhem.co.uk/forum/index.php?topic=14422.0)

The length wont be more than about 15cms, and I can anchor the outer to the hull side for most of its length. I have some plastic connectors which I might be able to use, otherwise I'll get some of the metal extenders.

Barrie
Logged

pneumatician

  • Guest
Re: How do I connect this to a servo?
« Reply #9 on: December 23, 2008, 09:10:13 PM »

What you have there are what we Aeromodellers call "Snakess" for obvious reasons. 
A Nylon inner cable with a Nylon outer.  On good "Snakes the inner is ribbed to reduce friction.  The inner is also a tube and standard servo snap links and threaded rod is available from all good model shops or you could try www.sussex-model-centre.co.uk/shopdisplayproducts.asp?Search=Yes&sppp=12.

Anchorage can be quite critical to prevent movement loss.

Steve
Logged

amdaylight

  • Guest
Re: How do I connect this to a servo?
« Reply #10 on: December 24, 2008, 03:00:03 AM »

Barry,

I thought that the inner core was a tube like the Sullivan product, now for a couple of new thoughts (please treat them gently) First take a sample with you to the local hobby shop and find a clevis that will thread onto the inner core,  Now for a question, what is the diameter of the inner core?. Second you may be able to adhere (crimp plus glue) a small piece of brass tube to the inner core and then thread that to accept the clevises and ball links.

Let me know and I will keep beating the bush for new ideas.  <*<

Andre
over yonder in Portland Oregon

PS I should have read the other replies be fore writing this one as it basically says the same thing, sorry guys :embarrassed: {:-{
Logged

barriew

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,012
  • Location: Thaxted, Essex
Re: How do I connect this to a servo?
« Reply #11 on: December 24, 2008, 12:36:33 PM »

Thanks Andre - I think I have enough options to go on for now. I may indeed have another option which is to mount a miniature servo nearer the rudder and use a conventional link. Just need to see how much room and access I will have. I know these things are pretty reliable now, but I don't like putting things where I can't get at them :-))

Barrie
Logged

Seaspray

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,263
  • Model Boat Mayhem is the best model boat site
  • Location: East Ayrshire Scotland
Re: How do I connect this to a servo?
« Reply #12 on: December 24, 2008, 01:15:55 PM »

This is what I did as I had to have the servo a good bit away from the rudder post.

The wires are shaped past the motor each side to the rudder and all connected with plastic clips (4 off). These plastic clips have screws in their sides that tighten up on the wire which slips into them. I wasn't too keen to use snakes incase they jammed or interfered with the radio. I also used a servo extension wire. The servo is glued to a piece of ply on its end, it is just glued to a flat piece of ply to the hull bottom.

Seaspray
Logged

amdaylight

  • Guest
Re: How do I connect this to a servo?
« Reply #13 on: December 24, 2008, 10:09:50 PM »

Barrie,

What ever you do, don't bury that servo where you can't get to it because if you do Mr. Murphy and Company will surely get involved.

Now as to a question for the rest of the gang, why do you use two push rods to the rudder, I have built a lot of aircraft and have never needed two except on the real large aircraft.

Andre
Logged

Shipmate60

  • Global Moderator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 5,223
  • You bark - I will bite!!!
  • Location: Fareham
Re: How do I connect this to a servo?
« Reply #14 on: December 24, 2008, 11:08:00 PM »

There are 2 main reasons.
1/ going astern the rudder can travel "overcentre" and turn too far one way and jam.
Water is much denser than air so has a greater force on the rudder, plus the boat can hit something while going astern.
2/ Using 2 rods ensure that the main force is on the rod PULLING the rudder which is less stressful on the bends. It also balances the forces on the activating horn, therefore the servo. This usually leads to a more sensitive rudder.

Bob
Logged
Officially a GOG.

amdaylight

  • Guest
Re: How do I connect this to a servo?
« Reply #15 on: December 25, 2008, 12:34:38 AM »

There are 2 main reasons.
1/ going astern the rudder can travel "overcentre" and turn too far one way and jam.
Water is much denser than air so has a greater force on the rudder, plus the boat can hit something while going astern.
2/ Using 2 rods ensure that the main force is on the rod PULLING the rudder which is less stressful on the bends. It also balances the forces on the activating horn, therefore the servo. This usually leads to a more sensitive rudder.

Bob

Thanks Bob,

With aircraft going astern or backing into something is not something we have to worry about much and when it does happens over centering your rudder is usually the least of your problems something about re-kitting the airplane  {:-{. On my larger airplanes (Over 8' wingspan) I do use a pull-pull system but had never given much thought to the different viscosity of water and air and since my smaller airplanes are around 4 to 5 feet long which are about the same length as the boats I build I have always gone with the same set up. Not any more though< I will start using a pull-pull system in my boats where I can.

Learning something new everyday that I am in Mayhem  :-))

Andre :-)
over yonder in Portland Oregon
Logged

Seaspray

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,263
  • Model Boat Mayhem is the best model boat site
  • Location: East Ayrshire Scotland
Re: How do I connect this to a servo?
« Reply #16 on: December 27, 2008, 08:45:20 AM »

I use where poss as I like to think the servo is balanced when being used. I do have 2 other models on a single wire link. I feel I would like to change them to double wires   O0

When I did the flying it was always single link / rod / snake I always thought it was a weight issue.
Logged

BobF

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 498
  • Location: East Yorkshire
Re: How do I connect this to a servo?
« Reply #17 on: December 27, 2008, 12:22:58 PM »

Hi,
just had a quick read through the replies. I don't think any one has mentioned that some clevis's have a screw clamp fitting. A small screw that goes in from the side, and pinches against the inner cable.
Just a thought.
Logged

barriew

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,012
  • Location: Thaxted, Essex
Re: How do I connect this to a servo?
« Reply #18 on: December 27, 2008, 12:48:13 PM »

Bob,

Indeed I found one of those in my box of bits (minus the clamp screw , buts that easily sorted) and the other end will fit into a plastic 'ball and cup' type connector which I intend to drill and pin as I don't think you can glue the nylon rod. I was going to post a picture, but keep forgetting to take my camera to the shed :D

Barrie
Logged

andyn

  • Guest
Re: How do I connect this to a servo?
« Reply #19 on: December 27, 2008, 01:12:06 PM »

I don't think any one has mentioned that some clevis's have a screw clamp fitting.

Unfortunately these things when installed on snakes slip like a b****** and once nearly cost me a glider.

They wont slip down the tube, but do slip off.

Cyano will adhere to nylon, but it is probably a good idea to put a pin through too.
Logged

pneumatician

  • Guest
Re: How do I connect this to a servo?
« Reply #20 on: December 27, 2008, 02:23:23 PM »

On Aircraft I use Cables then of course they are always connected to both arms of the servo and control surface. This helps prevent blowback and flutter, flutter can cause complete surface failure in real Aircraft and more so in models.
One thing I have always thought a No No was right angle bends in push rods.  Also snap links that tighten to the control rod with small screws.
Again these things are not as critical in Boats as Aircraft but when a few hundred quid hits the ground because the linkage failed is very embarrassing. :((
Perhaps these considerations are more pertinent in  Submarines.

Back to me planking now.
                                  Steve
Logged

derekwarner

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,929
  • Location: Wollongong Australia
Re: How do I connect this to a servo?
« Reply #21 on: December 31, 2008, 11:26:32 PM »

Hi all.....I must agree with Steve here......proprietry manufacturers [Du Bro & the like] would purchase purpose composition high tenslie ductile steel wire [zinc plated] for their control rods, however these materials are not designed for short radius bends

You could search GOOGLE...find out the Grade of steel used...then search under the AS/ASTM/BS number & ask for the minimumm [cold] bend radius

My guess for this type of wire would be in the order of 10 x the wire diameter....so for 1/16"diameter wire would be 5/8"diameter or 5/16"radius

An alternative to bending could be very small brass blocks with two 90 degree opposed drilings for soft soldering...I have also seem these drilled & tapped for 2.56 UN threads then used also as adjustments with 2.56 locknuts

The range of product from the manufacturers [previously mentioned in this string] is extensive to say the least & good value :-)) .........Derek





Logged
Derek Warner

Honorary Secretary [Retired]
Illawarra Live Steamers Co-op
Australia
www.ils.org.au
Pages: [1]   Go Up