Drum steerer

Dear all
I hope you don't get bored from a novice
I'm interseted in the old Drum steerer !!! with ropes
I didn't find enough info about this subject in my web search.

Which diameter the Drum should be?

Usually it relys on friction between the drum and the rope,would it be better to fix the rope to the drum before winding it around the drum!!
In one article they said that the drum was spinning and the rope was not winding and they had to wet the rope so it swells to be more firm around the drum

I have seen some photos of a system with tackle added to the system to gain more power

A digram would be great

Any info would be apreciated

Ahmed

 

What are you going to use it on? Sail? Powerboat? How big?

 

Good day
Great diagrams
It's for a a futre wooden fixed keel 2 chines motor cruiser
LOA 10.5
WL 9.45 M
Beam 3.0
desplacement 11.5 TON
Balast 6000.KG (internal only)
draft 1.1 m
schooner 66.0 m
Thanks
Ahmed

 

This has more to do with small boats but it will give you an idea of what's needed. There is something at thetop of the page and more about half way down.
http://www.glen-l.com/weblettr/webletters-3/webletter26.html
The main problem with it is if any one thing breaks while underway it may pull the steering violently one way or the other. But, then again, it works and has been used for a long time.

 

There are many ways to build this kind of steering system because the dimsnsions of the drum determine the number of elements in the tackle and hence the size of the rope.
Determine first the torque (in ft fbs, or metric equiv.) required to secure the helm of your boat. Depending on several factors this would vary a lot from boat to boat.
However, let's say your tiller would have 300 ft lb of maximum input as a requirement. Now you can figure out how to size your system.
The steering wheel would probably need to be easily managed with less than 20 ft lbs maximum leverage, meaning a 24" radius wheel would require that much pressure on the hand to turn when there was 300 lbs of torque acting on the tiller.
Therefore, you need a 15:1 system if the system efficiency is 100%, and more likely a 20:1 system guessing a 25% loss to friction in blocks and the drum.
To achieve one part of the mechanical advantage, the drum diameter in ratio to the steering wheel diameter might be 6:1. A 48" diameter wheel would then turn an 8" drum.
This leaves a tackle of 3:1 as the best choice. Actually, I wanted 3.33:1, and I can fiddle with the tiller attachment point to get my exact desired ratio.
All this also tells you the maximum normal tension on the drum, which would be120 lbs. Give this a good 3:1 safety margin (360 lbs). You can mock this up by setting up the 8" drum near the ceiling so it can't turn, hanging a 360 lb weight from one rope and a very light weight (maybe 10 lbs) from the other rope, and seeing if any slippage occurs. The 10 lb weight simulates a spring-tensioned idler block that would provide tension to the low tension side of the steering system (this spring tension can be changed any time to adjust the grip on the drum, along with the number of drum turns).
The drum surface could be made in many ways. A spiralling groove might be good in terms of rope wear. The rope might be the double braided type. To make a spiralling groove you could use a wooden drum (hardwood). The spiral would have to be turned on a machine lathe.
Hope this helps.

Alan

 

It's much clearer now !!!!
Thank you SamSam
Than you Alan,that helped a lot !!!
another point
Is there problems with riding turn on the drum from the rope !!
Because I think the rope lead will change with more turn on the drum.
Would be also exces loosening and tention on the rope when you turn from had to hard

Thank you
Ahmed

 

The origional drum steering was far simpler .

The wheel and drum were built on the end if the tiller and lines attached to the rail, as required.

As the wheel was turned it simply gave mechanical advantage to moving the tiller.It went back and forth ON the tiller.

In light weather the boat could be steered simply with the tiller, when it became heavy going the lines would be strung and the added leverage used to control the triller.

Interestingly since this is before the auto , the wheel went in the same direction as the tiller. Backwards from todays wheel steering.

FF

 

In small systems the cable is small enough and the lead of the rope changes enough to allow it to ride up on itself, which tangles itself and also changes the diameter and so the mechanical advantage. The grooves on drums stop that from happening in small systems. With larger rope and a smaller change in the lead, the rope might self wind without riding on itself. In the small systems there is usually a spring on each end of the final attachment to take up any slack and keep the system from tangling. That is one of the problems if any part of the system breaks, the tension on the other spring pulls the steering that way very suddenly.