Jaw Jaw toggle assembly

[coopec]

I am trying to complete my steering and need to join the cable to the chain. I'm considering using a Jaw jaw toggle and a wire rope swaged (or DIY swageless) fitting. The cost is the problem. Before I fabricate a a couple "Jaw Jaw toggles" is there a cheaper/better way?

No point going to Edson et al because the maximum they go to is 6 mm wire rope and my wire rope is 10 mm. The riggers say I won't find a solution "off the shelf"

 

[knuterikt]

On my Goiot steering there is a chain split link between the eye terminals and chain.
Would think the chain split link to be as strong as the chain.

 

[coopec]

On my Goiot steering there is a chain split link between the eye terminals and chain.
Would think the chain split link to be as strong as the chain.

Thanks for that

I could just put the Jaw Jaw assembly between two outer links of the chain and use a M5 clevis pin. That is probably what I would do as I can't see any need for a split link.

NOTE
I am trying to find the parts you mentioned in the Goiot Catalog but so far no luck

 

[knuterikt]

Thanks for that

I could just put the Jaw Jaw assembly between two outer links of the chain and use a M5 clevis pin. That is probably what I would do as I can't see any need for a split link.

NOTE
I am trying to find the parts you mentioned in the Goiot Catalog but so far no luck

boat is 35 years old..

 

[coopec]

boat is 35 years old..

Noted, but I'd still be interested to know how they handled it.

But thanks for your help. Just now I went through my scrap ss bin and found a length of rudder stock so I can make up two "Jaw Jaw Assemblies" out of that.:encouragement:

 

[Yngmar]

Chain + tensioner: https://www.svb24.com/en/bavaria-chain-sets.html

Only the tensioner: https://www.svb24.com/en/bavaria-chain-tensioner-for-control-chain.html

You'll note the tensioner has two threads to which you can fit whatever you like (one thread will be left-handed though). You can probably do something with that

 

[coopec]

Chain + tensioner: https://www.svb24.com/en/bavaria-chain-sets.html

Only the tensioner: https://www.svb24.com/en/bavaria-chain-tensioner-for-control-chain.html

You'll note the tensioner has two threads to which you can fit whatever you like (one thread will be left-handed though). You can probably do something with that

Yngmar

Thank you for those links.

I have yet to work out what diameter wire rope they would be for but that doesn't matter as the photos indicate I'm on the right track with what I am doing. (For once a bit of yacht gear seems reasonably priced)

My rigger says I should tension the wire ropes up at the quadrant but I'd like to be able to do it at the pedestal as well.

 

[Yngmar]

Better yet, it looks like Jefa has all the parts at okay looking prices: https://www.jefa.com/steering/products/cable/chain/chain.htm

Ours is tensioned at the quadrant like your rigger suggests. I've found this completely sufficient, but access to the quadrant is very good on our boat.

 

[coopec]

Better yet, it looks like Jefa has all the parts at okay looking prices: https://www.jefa.com/steering/products/cable/chain/chain.htm

Ours is tensioned at the quadrant like your rigger suggests. I've found this completely sufficient, but access to the quadrant is very good on our boat.

Thanks again Yngmar.

The photos are excellent but their gear is for max 6 mm wire rope (mine is 10 mm)



That gives me a lot of confidence to go ahead with what I am doing.:encouragement:

(I wonder how many cutting discs I'll wear out getting them into shape?)

 

[Norman_E]

What I am struggling to understand here is why the steering cable is 10mm wire, unless the boat is huge. My 45 footer uses 6mm 7x19 stainless wire which has a safe working load of about 320KG and a breaking load of close to two tons. 6mm is far more flexible around the pulley wheels in the two wheel setup than 10mm would be. I note that the Jefa parts only go up to 6mm wire size.

 

[coopec]

What I am struggling to understand here is why the steering cable is 10mm wire, unless the boat is huge. My 45 footer uses 6mm 7x19 stainless wire which has a safe working load of about 320KG and a breaking load of close to two tons. 6mm is far more flexible around the pulley wheels in the two wheel setup than 10mm would be. I note that the Jefa parts only go up to 6mm wire size.

Everyone asks the same question (and so did I)

Correct me if I am wrong but your yacht is a Sun Odyssey 45.2 which is aft cockpit.

The wire rope from the pedestal on your yacht to the quadrant is probably 1M (?) so it is not going to stretch in that distance. With a center cockpit the wire ropes are much longer maybe 5-6M (?) so there will be significant stretch over that distance. If it stretched (say) 1 1/2 inches that would translate to about 4+ inches at the wheel. By going to M10 you don't get any stretch and therefore the steering feels a lot more precise. That's how it was explained to me by the experts. (Incidentally my boat is 43ft)

 

[Norman_E]

It sounds a reasonable explanation, but I doubt that the wire actually stretches very much and I think 10mm wire is overkill. On my boat the wires travel round two pulleys on each side. I have not measured them, but they are probably 4 or 5 metres each. You are however stuck with the size you have. Without a diagram of your boat's setup its hard to see where your chain to wire joins are. Is it a system where the wheel has a chainwheel on it and both ends of the chain are attached to wires which end by pulling opposite sides of the quadrant?

 

[coopec]

It sounds a reasonable explanation, but I doubt that the wire actually stretches very much and I think 10mm wire is overkill. On my boat the wires travel round two pulleys on each side. I have not measured them, but they are probably 4 or 5 metres each. You are however stuck with the size you have. Without a diagram of your boat's setup its hard to see where your chain to wire joins are. Is it a system where the wheel has a chainwheel on it and both ends of the chain are attached to wires which end by pulling opposite sides of the quadrant?

"Is it a system where the wheel has a chainwheel on it and both ends of the chain are attached to wires which end by pulling opposite sides of the quadrant?

You got it in one:encouragement:.

I got my figures a bit wrong. The yacht has a 32 inch wheel and the chain sprocket it about 4 inches so the ratio is 8/1. Therefore if the wire rope stretched just 1/4 in. there would be 2 inch play at the fingertips. (1/2 inch = 4 inch at fingertips)

Logic would tell us that the type of rudder (balanced/unbalanced) would have a big factor on the loads of a steering cable. (If you have two rudders(?) that would halve the loads). Lewmar says we should only load up to 25% of breaking strain load. My rudder is unbalanced but hopefully I'd be nowhere near 25% of breaking strain.

For those interested in all types of Lewmar steering systems this brochure give quite a good coverage
http://moreman.ru/eshop/tovar/catalogs/lewmar/steering.pdf

 

[Norman_E]

I think that 10mm wire is excessive.

I pinched the following from the website of a wire rope supplier: https://www.s3i.co.uk/wire-rope-technical.php

Elastic stretch can be calculated by the following formula:

Elastic Stretch = (W x L) / (E x A)

W = Applied Load ( kN )
L = Cable length ( mm )
E = Strand Modulus ( kN/mm²)
A = Area of Cable = (D2 x pi) / 4 (where D= Dia of cable mm)

Typical values for E are:

1x19 = 107.5 kN/mm²
7x7 = 57.3 kN/mm²
7x19 = 47.5 kN/mm²
Dyform = 133.7 kN/mm²

One kN or kilonewton is the measure of force equivalent to about 102 kilgrams mass.
So lets apply a load of one kN to your steering wheel. That is the equivalent of a heavy man hanging his entire weight on the rim of your wheel at the 3 O'clock position. That equates to 8KN at the chain.

Applying the formula, Elastic Stretch = (W x L) / (E x A) we get (8 x 6000) / (47.5 x 15.7) or 48000/745.75 = 64.36mm That is for 10mm wire with a cross sectional area of 15.7 sq mm For 6mm wire substitute 9.4 and the elastic stretch works out at 107.5mm

Both the above figures are however quite ridiculous because firstly you could never apply such force at the wheel rim, but more importantly it does not need more than a tiny fraction of that to move the rudder, which is solely determined by the force of water against it and the bearing friction. Even a completely unbalanced rudder in a sailing yacht will not need much unless the quadrant is a tiny one. Mine is about 12 inch radius and my wheels are 36 inches with a sprocket less than 3 inches diameter so in theory I could exert more force on my steering wires. In practice I doubt that I apply a force of 50kg to the wires in any conditions. Don't forget that the above example is putting 8kN on the wire, that is over 1600kg, so if the actual maximum force applied is equivalent to 100KG, which I doubt very much, the stretch of a 6mm wire would be less than 7mm. 3mm more than 10mm wire. Would that matter in practice? I doubt it.

 

[Norman_E]

I am trying to complete my steering and need to join the cable to the chain. I'm considering using a Jaw jaw toggle and a wire rope swaged (or DIY swageless) fitting. The cost is the problem. Before I fabricate a a couple "Jaw Jaw toggles" is there a cheaper/better way?

No point going to Edson et al because the maximum they go to is 6 mm wire rope and my wire rope is 10 mm. The riggers say I won't find a solution "off the shelf"

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There is a far cheaper method of attaching the wire to the chain, if you have the space for the parts. Look at this page for wire rope grips. https://www.s3i.co.uk/stainless-steel-rope-grip.php
You need to bend back the wire ropes round a thimble and secure with three grips per rope. Join the thimble to the chain with two strips of stainless steel long enough to span the length lost by doubling the wire back on itself, with a high tensile bolt through the last link of the chain at one end and a bolt through the thimble at the other. 3mm x 20mm steel is about right. A slice of steel or even plastic bar like a thick washer to fill the inner diameter of the thimble is a nice extra, but not really necessary. See this video: https://www.youtube.com/watch?v=HKt6kswEAXo

 

[pvb]

The wire rope from the pedestal on your yacht to the quadrant is probably 1M (?) so it is not going to stretch in that distance. With a center cockpit the wire ropes are much longer maybe 5-6M (?) so there will be significant stretch over that distance. If it stretched (say) 1 1/2 inches that would translate to about 4+ inches at the wheel. By going to M10 you don't get any stretch and therefore the steering feels a lot more precise. That's how it was explained to me by the experts. (Incidentally my boat is 43ft)

10mm wire rope is complete overkill. There's no way that 6mm wire rope would stretch 1.5" under the very low tension involved in a steering system. You need to find new "experts".

 

[coopec]

Norman

I do appreciate you going to the effort you have. I've gone through this exercise before but a long time ago.

Just now I have been doing some calculations of elastic stretch of 7 X 19 cable and also forces on a rudder. the forces on the rudder can be found here:

https://www.phoenixmarinesolutions.co.uk/themes/phoenixmarine/calc.html

My rudder is 1.4M height
Average width .4M
Speed 8 (max)
My rudder post is not vertical (let's ignore that)

As far as elasticity of wire rope is concerned I've used the formula here



I'll go over my figure again but working on 8 ft (6mm wire rope) I found the stretch was .21384 of an inch. As there are two cables there would be .42748 inch at the sprocket and therefore with a 32 in wheel and 4 inch sprocket 3.42 inches slack at the fingertips.

Now where have I gone wrong?

(I'll go over your calculations too to see if they give similar results)

I better do some work but I'll be back.:encouragement:

 

[coopec]

There is a far cheaper method of attaching the wire to the chain, if you have the space for the parts. Look at this page for wire rope grips. https://www.s3i.co.uk/stainless-steel-rope-grip.php
You need to bend back the wire ropes round a thimble and secure with three grips per rope. Join the thimble to the chain with two strips of stainless steel long enough to span the length lost by doubling the wire back on itself, with a high tensile bolt through the last link of the chain at one end and a bolt through the thimble at the other. 3mm x 20mm steel is about right. A slice of steel or even plastic bar like a thick washer to fill the inner diameter of the thimble is a nice extra, but not really necessary. See this video: https://www.youtube.com/watch?v=HKt6kswEAXo

I must be missing something here. How can I put a 10mm wire rope and thimble through a motor-cycle chain link? I'm utterly confused!

Maybe the answer lies in your statement "if you have the space for the parts." If I understand you correctly then I don't have the space.

]

 

[coopec]

Norman

Apparently the formulas we are using are similar but I will have to sit down and go over your calculations when I'm less rushed.

One thing we seem to disagree on is the load on a rudder and I've given a link to a calculator in another post. Here it is again

https://www.phoenixmarinesolutions.co.uk/themes/phoenixmarine/calc.html

My rudder is 1.4M height
Average width .4M
Speed 12 (surfing down a wave)
My rudder post is not vertical (let's ignore that)

Suppose I'm in a gale and start surfing at 12 knots the load on the rudder would be 650kg. The mechanical advantage of the quadrant would be about 8:1 and the mechanical advantage of the pedestal gear/wheel would be about 10 so total 18 Therefore load on the wheel would 650/18 = 36kg

That sounds about right to me but I'm rushing (Gotta do some work on the yacht)

Cheers
Clive

 

[coopec]

10mm wire rope is complete overkill. There's no way that 6mm wire rope would stretch 1.5" under the very low tension involved in a steering system. You need to find new "experts".

Very low tension? Really!! (You can't be serious?)

Why don't you google something like rudder torque calculation