Steering pulleys (sheaves)

coopec

coopec

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I've been working on the design of the yacht steering for some time now.

Originally I planned to use 8mm SS 7/19 cable but the experts said I should use 10 mm and pointed out the quadrant could take 10mm. The minimum diameter sheave for 10 mm cable is 7 inch (to avoid fraying) so I priced them and the Harken 178mm is $197 (plus freight). Since I needed about 10 of them that was out of the question.

I have now looked at using V belt pulleys and find I can convert the V of a A-Section pulley with minimal machining to take 10 mm cable. I will then use Bronze self lubricating bearing sleeves. (Having a Son with a lathe helps).

Can anyone see a fault with my plan?

Temp V belt.JPG

Temp Bearig sleeves.JPG

s-l640.jpg
 
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Hi, need to get an understanding of your boat?

WLL, displacement, underwater profile, rudder profile (skeg/balanced etc) to get a better understanding.

10mm wire for a steering system sounds, well, huge , unless you've got a very large, or very heavy boat.

6mm wire, with a 12" quadrant would suit up to 13500in.lb (1500Nm) of torque, with a safety factor of 4x and is used on medium displacement boats in mid-40 foot range with a balanced rudder, as a reference point.

Fundamentally, if you're sure there's enough "meat" in the V-pulley castings to allow you to machine in a smooth radius for the wire, then don't see any reason why it shouldn't work.

But have you tried the likes of Edson, Jefa and/or Lewmar for the price of their spare sheaves intended for steering systems?
 
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I have an album on Flickr
https://www.flickr.com/photos/44071060@N06/albums/72157631756633356

The yacht is 43ft and weighs 26880 lbs
https://www.finelineboatplans.com/bruce-roberts-mauritius-norfolk-43-boat-plan

The yacht is center cockpit and therefore there is a fair distance between the pedestal and the quadrant (unlike an aft cockpit yacht)

Taskers (who are professional sailmakers and yacht riggers) said 6 mm cable is too light. Then they said I could use 8mm but I'd be better using 10 mm as there would be less stretch and I'd get a more positive feel.

Looking at Edson and Ronstan equipment advertised they don't really cater for larger yachts.
https://edsonmarine.com/sailboat-data-sheets/
 
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OK, still 10mm sounds really overkill to me. Whilst I'm sure Taskers are familiar with wire breaking loads etc, there is a certain speciality on steering systems that you should tap into.

I'd personally reach out to Lewmar or Jefa....they're the 2 biggest players in sailboat steering systems right now and both cater all the way up the yacht size scale.

They also have steering sheave pulleys off the shelf, from 4" up to 10" or so, from memory, and shouldn't be too (?!) expensive...though may still of course be more than v-pulleys simply due to the volumes produced.
 
I'm sure they weren't suggesting 8mm SS would break but they said it would stretch over a distance.

I just priced an 80mm Lewmar sheave (I need 178 mm diameter) and they want $USD255. (Out of the question!)

As far as "meat" on the pulley is concerned surprisingly I would only need to take about one mm out of the groove each side and bottom. I'm wondering if I should get a 10 mm rod/tube, wrap some emery paper around the tube, spin the pulley in the lathe and sand the pulley into shape. ( I reckon I could do each pulley in a few minutes.)
 
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coopec said:
I'm sure they weren't suggesting 8mm SS would break but they said it would stretch over a distance.

I just priced an 80mm Lewmar sheave (I need 178 mm diameter) and they want $USD255. (Out of the question!)

As far as "meat" on the pulley is concerned surprisingly I would only need to take about one mm out of the groove each side and bottom. I'm wondering if I should get a 10 mm rod/tube, wrap some emery paper around the tube, spin the pulley in the lathe and sand the pulley into shape. ( I reckon I could do each pulley in a few minutes.)
Click to expand...

Which sheave are you looking at from Lewmar?
 
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cobolt said:
Yeh you're looking at their high end racing kit, this is designed for running rigging, not steering systems, so it has needle bearings, side-thrust ball bearings, machined from solid aluminium block, the full works...you can't really compare to a cast steering sheave!
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Ok, can you point me to one of their (Lewmar/Ronstan/Edson/Harken) "el cheapo" 7 (or 8) inch ones please!
(It would be great if you could prove me wrong but I'm not holding my breath)

Temp Sheaves.JPG

As I said I find any Ronstan, Lewmar or Harken product comes at gold plated prices and none of them appear suited to a largish cruising yacht.

Here are Edson prices
https://edsonmarine.com/products/sa.../wire-rope-sheaves-assemblies/single-sheaves/
 
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What kind of preload tension do you expect to run the wire with?
I suspect fat wire with low preload will give more slack as it mves around the sheaves.

We had an Edson system on a 42ft boat. I think the wire was 5mm.
5mm s/s 7x7 has a breaking load of about 1.5 tonnes? Might have been galv wire?
Our wheel was about 4ft, the sprocket in the middle about 2 inches?
Say max 300kg on the wire would be 12.5kg at the rim of the wheel? That would be pretty physical to steer?
Work out the stretch for sensible steering forces?

I think machined ali sheaves will corrode and wear if not anodised, but you could get that done, or even DIY.
 
Just a couple pf points.

In my long, long experience of cable systems for motorcycles it is clear to me-and the manufacturers-that twisted wire cable of the Bowden type has no, or only infinitesimal, stretch.

What happens with motorcycle cable systems is that the outers compress.

This gives effectivly the same effect.

I see no reason for a boat system with an outer to act any differently.

Our American boat uses an Edson cable steering system, with both inner and outer cables. It is a 12 metre heavy Motorsailer and uses 10mm-or perhaps 3/8th inch-cables. It has screw in lubricators in the outers.

The boat is 12 years old, has 1,000 hours on the engine and has no appreciable play in the steering-perhaps an inch of backlash.

It has never been adjusted-its got sealer on the threads of the adjusters-and I dont intend to adjust it untill the backlash more than doubles. It has remained the same in four seasons and 5,000 plus NM. It is lubed by turning the greasers down regularly-every time the oil and belts are checked.
 
rotrax said:
Our American boat uses an Edson cable steering system, with both inner and outer cables. It is a 12 metre heavy Motorsailer and uses 10mm-or perhaps 3/8th inch-cables. It has screw in lubricators in the outers.

The boat is 12 years old, has 1,000 hours on the engine and has no appreciable play in the steering-perhaps an inch of backlash. .[/QUOTE

I wouldn't compare motor-cycle bowden cables with yacht steering cables. (I reckon they are like chalk and cheese)

You say your boat is "12 metre heavy Motorsailer". Is that a center cockpit? How long are the cables from helm to quadrant?
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coopec said:
rotrax said:
Our American boat uses an Edson cable steering system, with both inner and outer cables. It is a 12 metre heavy Motorsailer and uses 10mm-or perhaps 3/8th inch-cables. It has screw in lubricators in the outers.

The boat is 12 years old, has 1,000 hours on the engine and has no appreciable play in the steering-perhaps an inch of backlash. .[/QUOTE

I wouldn't compare motor-cycle bowden cables with yacht steering cables. (I reckon they are like chalk and cheese)

You say your boat is "12 metre heavy Motorsailer". Is that a center cockpit? How long are the cables from helm to quadrant?
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It is an Island Packet SP Cruiser, a modern motorsailer with a huge pilothouse and only an internal steering position. The cables must be over 6 metres long. They are vertical from a sprocket behind the 30 inch wheel. They are attatched to a piece of motorcycle chain which goes around the sprocket. They then turn through a gentle right angle and go either side of the engine bay, into the lazarette area and then onto a large split plastic wheel clamped direct to the rudder stock.

Why would marine cable be any different to smaller bowden cable? It is made in EXACTLY the same way.

I made a test length of motorcycle inner cable years ago, before deciding to make cables for customers-I had trusted my life, and First Mates life-to cables I had made for our race bikes.

The test length was exactly 412 mm long, with 3/8 inch barrel nipples each end, dip soldered using a solder pot with an aggresive flux and a hard solder-not electrical solder.

One nipple was fixed into a 3/4 inch steel bar across the top of my Churchill 100 Ton 2 speed hydraulic press, the other end to the same sized piece of bar screwed into the piston end.

When the press was operated it tightened the cable, dead straight downward push. IIRC it exceeded 3 tons on the gauge before I stopped. No human hand working a motorcycle control lever could apply such pressure. When measured, the cable was still 412 mm long-measured top of barrel nipple to top of barrel nipple.

That was good enough for me. My hand made bespoke motorcycle control cables have been sent all over the world, perhaps thousands of them, never had a failure.

Had customer failure when they sent the wrong dimensions though!
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I am progressing with the chain and cable steering for the yacht.

The "V" belt pulleys cost $50 and the roller races $3 but then there is the machining. Fortunately my Son has just bought a lathe and while he is inexperienced he is doing a great job. (I can't guess what a Fitter and Turner would charge per pulley)

I've shown the pulleys to the professional yacht rigger who examined them carefully and he can see nothing wrong with them.

The cost of an Edson 8 inch pulley (with needle roller bearing) is $285

IMG_1681.jpg

IMG_1682.jpg
 
My yacht when acquired had a tiller. I replaced it with pull, pull cables which was good until the mild steel sheaths rusted. I now have sheaves and use dyneema instead of ss cable. Smooth, easy to maintain and check at any time.
 
LadyInBed said:
Maybe a silly question, but have you googled Pully Wheels?
A large selection comes up at sensible prices.
Click to expand...

Thanks for the suggestion but 99.9% would not be appropriate. For example:

  • Anything less than 7 in, (180mm) diameter is no good.
  • "V" belt pulleys -no
  • less than 10mm cable groove is not acceptable.
  • Pressed metal - not appropriate.
  • capable of handling large forces 500kg+?
  • many are not affordable ($285 ea. is out of the question as I need X10 of them)
For Stainless Steel cable the diameter of the pulley must be a minimum of 7 in. otherwise the strands start to fray.
 
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