Pull Pull geometry

[namba969]

Hey Guys,

Im setting up my first pull pull steering setup in my new tunnel and im having a few issues. I originally picked up a hanger 9 aluminum wheel but it is too large for the radio box, as is every other pull pull wheel I could find. So now I'm forced with using a straight doubled sided servo horn. The problem I'm having is the servo horn leverage is shorter than the leverage on the engine, causing the cables to be tight when engine is straight, but once you turn the engine, the cables are loose and the lower and engine can now flop left or right. I have seen pictures of people using pull pull cables with straight servo horns, just not sure how you keep the cable tension the same throughout the throw of the servo. Does this make sense? Any help or advise would be appreciated!!

Thanks,

Andrew

 

[Jerry Dunlap]

Hi Andrew,

I use pull/pull cable steering on my 20 Kneeler. The cables are connected to Robart radio box seals. When both cables are tightened equally, I've not experienced an issue with one cable becoming slack when turning the engine.

I'm attaching a photo of my cable steering system. As you can see, the cables run along the fuel tank sides.

JD

 

[Bill Britton]

I think you will find that the distance between cables at the servo is smaller than the distance between them at the arm on the foot. If you are getting slop in the cables when the servo turns, the cables are further apart at the foot. I they get tighter when the servo turns the distance is smaller. They must the the same.

Or do I have that backwards... :blink:

 

[RodneyPierce]

I should have some small and medium hangar 9 wheels here by the end of next week, if those would work for you. Get me the width in your radio box, and I can measure them for you.

 

[HOTWATER]

I have never had a problem with cables being tight and them becoming slack when the servo goes left to right....are you setup like Jerry Dunlap's picture with two seperate cables with clevises on all ends? Can you take a pic of your setup? Would be very hellful to us.....

 

[Bill Britton]

Sorry for the bad quality but i did it quick. Look at the image I attached. The top one is correct, the lower two will cause problems.

 

[moparbarn]

the width of your pull pull wheel & the steering arm need to be as close to the same width as possible. like bill described, a difference will cause what you're having happen. on boats with a narrow radio box, i have redrilled the steering arm to come closer to matching the wheel. can't go too far in though, you lose leverage & will need a stronger servo. also, closer on the engine end means quicker steering, & a potentially "twitchy" boat......i have changed out radio boxes that have a lip around the outside for straight sided ones, to gain the extra width . the advantage of the wheel over an arm is the pull in relation to the radio box seal is linear, no sideways movement. an arm swings an arc, causing sideways movement, requiring a boot type seal. with a wheel, you can just run a small nylon tube for the cable, with a simple heat shrink "wiper/seal" on the outer end.

 

[Grimracer]

Yes.. A pull pull.. IF' the servo output and the tiller mounts are not the same width WILL cause this. IF' they are the same they will not..

BUT.. truth is you are likey expecting the engine to turn to far. It really only needs to pitch about 1" (prop nut) in eather direction. You will never notice it has a tick of slack in it, when you turn, on the pond.

Grim

 

[Ray Sametz]

Question, why not use two 4-40 rods like I did back in the day????...==={}

 

[Jerry Dunlap]

Question, why not use two 4-40 rods like I did back in the day????...==={}

I just thought the cables looked cool on the Kneeler. I use solid rods on my tunnel boats.

JD

 

[Kevin Krogness]

Jerry I tried looking up those Seals you used. Are they no longer made? I typed them in google and this was all that came up.

http://www.pacinfo.com/~yayoe/Review/LEECRAFT%20XT.pdf

 

[HOTWATER]

Those are Robart seals....not sure if you can still buy them...

I agree with using the 4-40 rods...that's what I use now...0 problems....

 

[namba969]

Sorry for the bad quality but i did it quick. Look at the image I attached. The top one is correct, the lower two will cause problems.

View attachment 44797

Originally I had a distance of 1.25" between the clevis' on the servo horn and 1.75" on the engine steering arm. So I redrilled the engine steering arm to make it 1.25" to match the servo horn distance, same issue, just not as bad. The radio box I'm working with is VERY narrow, like 1.5" wide where the servo sits. One thing I did notice was that the eninge/lower pivot point is not on the same plane at the steering arm on the engine. (using a hijack mount, cmb redhed, and lawless lower with a 707 steering arm on the engine) Robin, would you have a wheel that is less than 1.5" in diameter?

Thanks again

Andrew

 

[Kevin Krogness]

I have a little slop in mine but like Grim said it is only when alot of steering input is used or more then needed I should say. I have not noticed a problem when running.

 

[namba969]

How much is a little slop? And how far off center was the prop before the slop started? This is actually my first tunnel so this is new to me.

Andrew

 

[Bill Britton]

I would use 4-40 rod if i were you.

 

[Jerry Dunlap]

Jerry I tried looking up those Seals you used. Are they no longer made? I typed them in google and this was all that came up.

http://www.pacinfo.c...LEECRAFT XT.pdf

I purchased the Robart seals at my LHS. I bought a couple of packages a month or so ago.

JD

 

[Kevin Krogness]

Jerry are they available any place else? Do you have a close up picture of the whole works? I like the looks of them! Thank you..

 

[Jerry Dunlap]

Jerry are they available any place else? Do you have a close up picture of the whole works? I like the looks of them! Thank you..

I used the Robart seals in the radio box for my JD Sport 20 Hydro. I'm not sure if Tower carries them.

JD

 

[RonShaw]

Hi Andrew,

I use pull/pull cable steering on my 20 Kneeler. The cables are connected to Robart radio box seals. When both cables are tightened equally, I've not experienced an issue with one cable becoming slack when turning the engine.

I'm attaching a photo of my cable steering system. As you can see, the cables run along the fuel tank sides.

JD

Jerry,

You care to share more on your turn fin placement for that Kneeler??? Looks like it is attached the side of the center section instead of the sponson, the way Tommy Lee used a turn fin on his oval record tunnel. Caught my eye right away.....