HMB Endeavour tiller and steering question

[dashi]

Thanks Jud I think we have a working theory.

Druxey these variations became apparent in my calculations as shown which I was expecting to see. As we know Pollard solved this in 1771 so until then each helm would have had more 'character'.

These variations can be smoothed by varying the diameter of the drum in different places to take more or less rope per turn which we have evidence of. From my understanding Pollards invention keeps the helm tension linear throughout the entire sweep of the tiller therefore eliminating all this jiggery pokery of the drum and tackle for larger ships where the tiller and it's support sweep could be fitted beneath the quarterdeck.

 

As for the helm of vessels slightly smaller but requiring a wheel where a long heavy tiller was on the quarterdeck then this is the problem we are attempting to workout.

Edited April 3, 2016 by dashicat

[dashi]

Jud and Druxey here is my calculation for 1/4 which I hadn't bothered with in my previous post. It shows this variation a bit clearer.

 

32.5+51.5=83mm

 

I'll edit my previous post to include this calculation. Can you please confirm this Jud?

[jud]

 Went back into cad and copied the hard Left Rudder drawing, put in a Tiller at half Left Rudder, adjusted the blocks so they were as they would be under strain and snapped the distance. See the results in my post above. As I believed, looks linear to me.

[dashi]

Thanks Jud I'm happy to go with your cad calculations as my eyes aren't too good and play optic tricks on me from nurve damage that glasses can't compensate very well.

[druxey]

If your calculations are correct, build a working model to prove things out!

[jud]

Don't need to druxey, I don't have a problem with what I have said, might be wrong about what I think was done, but the math and physics I have been working with is correct. If you have a problem, why don't you build a model based on my drawings and prove me wrong?

jud

[druxey]

I wasn't challenging you or your calculations, Jud, just suggesting an empirical experiment! Sorry if what I wrote sounded more aggressive than I meant it to.

[JerseyCity Frankie]

I am puzzled by the destination marked "To Tension Adjusting Blocks" in the notation on this drawing. Is it being suggested that even more tackle is needed for these lines? I think this rig is already too complex. Not shown in the drawing are the forward lead blocks to guide the line back to the drum on the wheel, six blocks on the bulwarks and two on the tiller in total, plus "tension adjusting blocks" somewhere aft?  There is not-in my opinion- a need for all the blocks indicated and hinted at in the drawing to do the job of transferring forces from the wheel to the tiller. Here is how I would rig it: The line end of the line is fixed to the aftermost leadblock on the bullwarks and is rove through the block on the extreme end of the tiller then rove through the aftermost lead block it originated from. It then is lead forward to another bulwark mounted leadblock located exactly abreast the drum on the wheel. It takes the prescribed number of turns around the wheel then repeats the lead on the opposite bulwark. There are six blocks in total.

Without building a working model its unlikely you are going to see how much actual slack is introduced into the line by the arc the head of the tiller passes through. But lets examine this arc. Lets assume for the sake of argument that when the rudder is amidships the head of the tiller is two feet above an imaginary port and starboard line drawn on a flat deck with no curve built into it ( I know our deck has a curve but lets keep it simple). Now lets assume that when the tiller is hard over the height above the imaginary athwartship line has been reduced by a foot (and this is being generous). All one need do is mount the lead block on the bulwark at a point equidistant between these two heights at the 1.5' level and half the slack is eliminated. With three or more turns on the drum at the wheel this amount of slack can be easily dealt with if there is ever a point where the tension falls below the level of keeping the turns tight. Simply "tailing" the slack on the opposite side of the drum would keep all tension required to ensure the turns were holding. Also selecting a line with a lot of elasticity will go a long way to keep the slack manageable.

Edited April 4, 2016 by JerseyCity Frankie

[jud]

Good questions Franke. Keep in mind my first sentence in my post, #54, and the word perhaps. This was kind of an interesting exercise for me because of my experience with the effects of slack allowing movement that is then violently stopped, IE, the end of the rope, a proper hanging or a mechanical joint destroyed. Slack is something mankind has learned to avoid in the things he makes and slack in a steering system can be bad if it allows movement to happen that is then stopped suddenly. A man on the end of a tiller is a buffer absorbing the different forces acting on the rudder caused by wave action and the vessels reaction to it, 'constantly changing of the direction of forces'. Now if that man got tired of being beaten around and tied off the tiller, that would be fine as long as the lashing did not allow movement, allowing any slack would soon destroy the steering system because movement brought up suddenly, loosens, first connections then more.

That is why I adding Tension adjustment to my sketch, I do know that later steering systems using steering quadrants as rope guides placed adjusters on the tiller arms themselves.

Did not show any of the steering gear forward of the forward blocks that I did show, because that part of the system is rope running through stationary blocks to a stationary steering drum, none of which takes up or allows any more or less slack than already exists. Unless the drum is in a cone configuration, what goes on the drum, an equal amount comes off, so I didn't consider that part of the system a variable which I could reasonably manipulate.

The arc that the Tiller gear travels is another constant that we can only change by changing the length of the tiller itself, that arc is curricular, not a straight line, that creates a swing for any rope pulling on it from the side, can't change that. Then by mounting the blocks to the bulwarks at a height that keeps the vertical changes at a minimum that leaves us with only controlling the effects of the swing on the length of the lines on each side of the tiller to play with. We can keep that effect minimal by using the direction of the pull as the controlling factor. I chose two blocks to do that, why did I place them where I did? I drew a line from the end of the tiller through the end of the ark at the maximum swing of the tiller extended to the bulwark, I drew another line beginning where the first one began on the tiller through the maximum swing of the ark and extended to the bulwark. At the bulwark I now had two points related to maximum tiller swing, found the mid point between them for a third point. That third point represented the center of the change in movement of the tiller perpendicular to the arc, half of that movement being on each side of a line from the tiller to number 3. I placed two blocks at equal distanced from #3, that gave me a minimum perpendicular movement to the arc as the tiller was moved from C/L to its maximum outboard position. Doing it that way did keep the slack at a minimum that could be obtained without using a quadrant guide for the tiller ropes.

Is this the best way to do it, probably not? Do I think this is how it was done at the time, doubt it? This only represents an idea of how I might begin the layout if the rigging choices been mine to make, at that place and time.

Please keep in mind that I have not attempted to convince anyone or believe myself that my sketches represent how the Endeavour's steering gear was rigged, they only represent how I might do it. Others are welcome to add to or find errors with how my thinking might keep the slack at a minimum. I will especially encourage any documented enlightenment on this subject that might be offered or newly discovered.

I will defend the fact that movement allowed by slack, suddenly brought up will destroy anything over time.

I also must apologize that my communication skills prevented a much better explanation about my intent when posting those sketches. That shortcoming has lead me to be so wordy in attempting to clarify my intent and what I was saying, have been expect a chewing out for posting so much of what some must consider as drivel.

jud

Edited April 4, 2016 by jud

[dashi]

Frankie thanks for your input but if you look back over previous posts you will find that we have already tried that as part of 'working the problem' and it didn't work because of the chimney cowl. The working configeration now I believe is a lashing at the tiller head to tension the helm rope which leads to blocks positioned on the bulwarks to reduce slack and aviod the chimeney cowl, which then lead back through blocks to the wheel like on the replica. We have been using a tried and true formula for working out the slack in any given configeration and thanks to Jud's efforts on the cad I think we have don't that. Also your idea of more turns on the drum to take up slack won't work because the rope is nailed on the drum fixing a centre point for the closed loop formed by the helm rope, so the only way that I know they used to take up slack at the drum caused by the tiller arc, was to increase the diameter of the drum relative to where in the tiller arc the slack is produced. As I indicated earlier this was done by making the drum concave but I understand we don't need to do that in this situation. The year is 1768 and chances are the rope is rough hemp although I think they also experiemented with raw hide but I can't remember when.

 

According Jud (please correct me if I've got this wrong) the physics of a 21 foot 280 pound plus solid oak and iron headed tiller projecting 19 feet from the rudder head, unsupported would break the rudder head. History tells us that it was common practice to use an arced tiller support (sweep) 2/3rds of the tiller wood length from the rudder head as indicated on the 1771 drawing in my first post, to support heavy tillers on vessels that required a wheeled helm configuration. We don't know what the replica tiller is made from so until we do we can't use that as a working example for 1768 which I've indicated in previous posts.

Edited April 4, 2016 by dashicat

[jud]

 dasacat; Been close to 50 years since I studied force vectors and bending moments, there are probably others much more qualified to do the math than me but I will do a very rough go at it, it should show the types of forces acting on the top of the rudder post created by using an unsupported cantilevered steering tiller. The easy bending moment would be the iron fixture at the end, going to use a weight of 150 pounds and consider the force as acting on the end of the 16 foot section of the wood tiller. 16' X 150# = a 2400 ft lb bending moment at the rudder head.

 To make it easy will consider the force acting on the cantilevered tiller from it's weight acting at the mid point of 8'. So the weight of the oak tiller being 280 pounds concentrated at the unsupported midpoint the moments would be, 8' X 280# = a 2240 ft lb bending moment at the rudder head. Add those forces up, 2400 ft lbs + 2240 ft lbs = 4640 ft lbs of bending moment acting on the rudder post head, that way for the same reason we put long handles on wrenches.

  What I did here is only a limited and rough calculation of the forces involved, it includes assumptions about where and what forces are involved but it should indicate the value of having support for the tiller. The modern replica may be using lighter and stronger materials, what is under the rudder post cover is unknown. Materials may change and lightening the load but the directions of the force vectors involved have not.

  Keep in mind that my statics and strength of materials is very rusty and I'm not an Engineer.

jud 

Edited April 5, 2016 by jud

[dashi]

Jud I'm really appreciating your technical input into helping answer these questions and as far as I'm concerned your engineering expertise is way above my pay grade so I'm learning a lot from this discussion. As far as your education is concerned I think that puts you in good company as I believe Einstein was also a High School drop out, plus I have difficulty with communication too which has gotten me in a lot of strife over the years so I think I know where you are coming from in this regard.

 

Regarding the replica I have sent them an email with several technical questions concerning the helm and tiller that we would like to know the answers too. I don't know when or if I might get a reply.

 

In the meantime I'm searching methods of holding the tiller in the rudder head. If we use a tiller sweep then this would affect the design purpose of what appears to be a bracket going from the tiller up to the rudder head as shown in the proposed plans of 1768 but which I'm not seeing in the 'as refitted' plan of 1768 which might be due to only having access to a low resolution copy. 

 

Also if the tiller sweep were used on the quarterdeck then I'd imagine it would be the reverse design for under the deck where the tiller hangs by a 'gooseneck' from the sweep. So on the underside of the tiller I'd imagine there would be a projection with a curved steel plate that rode along the top of the sweep with possibly a lip on it's aft section to help brace the tiller. The sweep could possibly be made of oak 1' high with a greased steel runner on the top like Jud has suggested. The quarterdeck beams appear to have been placed in the correct position to support all this. This of course is just speculation based on my current novice understanding of the physics at hand.

[dashi]

While waiting for a reply to the email I have been wondering how to proceed with my build. I've decided that on my build log (not here in this discussion) I will attempt to build both helm rigs in a way that I can perform a simple refit should new information necessitate it.

 

I've also been looking at the tiller brace that runs from the tiller to the rudder head and need to ask this question if anyone can please help. From this research I'm noticing that in all the old tiller plans I've seen, all the heavy tillers can be readily removed by means of a pin through the end of the tiller or tackle from the tiller to hooks through 0 rings in the head. So if it is a solid metal bracket on the Endeavour then, would I be correct in speculating that it could only be bolted to either the tiller or head but not both. Meaning would one end need to be pinned or lashed some how to enable the ready removal of the tiller in an emergency?

[dashi]

dasacat; Been close to 50 years since I studied force vectors and bending moments, there are probably others much more qualified to do the math than me but I will do a very rough go at it, it should show the types of forces acting on the top of the rudder post created by using an unsupported cantilevered steering tiller. The easy bending moment would be the iron fixture at the end, going to use a weight of 150 pounds and consider the force as acting on the end of the 16 foot section of the wood tiller. 16' X 150# = a 2400 ft lb bending moment at the rudder head.

To make it easy will consider the force acting on the cantilevered tiller from it's weight acting at the mid point of 8'. So the weight of the oak tiller being 280 pounds concentrated at the unsupported midpoint the moments would be, 8' X 280# = a 2240 ft lb bending moment at the rudder head. Add those forces up, 2400 ft lbs + 2240 ft lbs = 4640 ft lbs of bending moment acting on the rudder post head, that way for the same reason we put long handles on wrenches.

What I did here is only a limited and rough calculation of the forces involved, it includes assumptions about where and what forces are involved but it should indicate the value of having support for the tiller. The modern replica may be using lighter and stronger materials, what is under the rudder post cover is unknown. Materials may change and lightening the load but the directions of the force vectors involved have not.

Keep in mind that my statics and strength of materials is very rusty and I'm not an Engineer.

jud

Jud is this correct: If I take an 18 foot beam and support it at a fulcrum point 'c' of 1 foot from end 'a' and apply 250 pounds at the other end 'b' then would it produce 1.9 tons of force at end 'a'?

 

Assuming I've understood the physics, then the 8" square oak tiller would need to be able to withstand a load of 1.9 tons at the fulcrum where it enters the rudderhead. Whilst the rudder head would need to be able to withstand an upward load of 1.9 tons @ 1 foot past the tiller fulcrum while at rest. If this is correct then we need to know two things. What is the breaking point of an 8x8" oak beam and the steel strapping required to lift 1.9 tons. If the breaking point of the oak tiller is less than 1.9 tons then it needs to be braced with a support along it's length. If it can withstand a breaking point of 1.9 tons plus extra for tolerences then the rudderhead needs to be strong enough to hold past an upward load of more than 1.9 tons.

 

Of course please correct me if I've got the physics wrong.

 

Bottom line is regardless of the conventional interpretation of history and what we might choose to believe, as Jud has rightly stated, "everything still needs to obey the laws of physics", which is what we are trying to research and answer here with out bias.

Edited April 8, 2016 by dashicat

[jud]

dashicat; Go to web.mit.edu/4.../1_lecture5.html and then click on, 'what is a moment', some good information there that should be of benefit to you and others wondering about forces and what it requires to keep things Static. An imbalance of force and resistance will result in movement unless restrained. 250# at the end of a cantilevered beam can create more force than many realize.

jud

[dashi]

Jud, could you repost that MIT link please, as it's coming up page not found? 

[jud]

"web.mit.edu/4.../1_lecture5.html" When you get there clik on "What is a Moment". I copied and pasted that link into my browser, it seemed to work for me.

I found the site by searching for "Moment Arm", a lot popped up.

good luck

jud

[dashi]

Another point to consider:

 

Cooks HM Bark Endeavour crew list http://www2.sl.nsw.gov.au/banks/series_03/crew_01.cfm there is no mention of a black smith that I can find. Now if the tiller brace which broke twice in the rough seas off the coast of New Zealand that Cook refers to in his log were made of steel then they would have needed a black smith to repair it. This would have entailed building a make shift smelting fire on shore to weld the broken metal brace back together which I think would have been doable but not likely with out a smithy.

 

Further having a past life as a industrial maintenance technician I can tell you that you don't use a nail to replace a blown fuse wire because that weakness is a safety feature built into the circuit so it breaks at that controled point protecting the rest of the wiring and building from serious damage. This same principle is true for any mechanical system, so it dosn't make any practical or logical sense to attach the tiller arm to the rudderhead using a thick chunk of steel right at the point where there is almost 2 tons of canterleaver preassure inside the rudderhead caused by the weight of an unsupported heavy oak tiller.

 

The most practical solution I think would be to follow accepted practice proven and used at that time for over 100 or so years. That is to support a heavy tiller along it's length using a 'tiller sweep' or quadrant thereby instantly reducing the canterleaver stress in the tiller head from 2 tons to 0 leaving only the sheer stresses from steering for the rudder head to take. As for the tiller brace I think it would also have followed tried and true practice and as such more likely would have been block and tackle to hold the tiller in it's seat in the rudder head. Then if there was a sudden loading at this point the tackle would break like a fuse in an electrical circuit thereby protecting the tiller and rudderhead from catastrophic damage and requiring only a short stay in a harbour for repair as indicated in Cooks log. Also this method of tackle to brace tillers needed tensioning from time to time to maintain a good fit of the tiller to rudderhead which couldn't be done with a solid steel brace.

 

So until more evidence to the contrary comes to light I think the the red line drawn in one of the 1768 draughts indicating what could be thought of as a tiller brace going from the rudderhead down to the tiller would more likely be indicating the tiller brace tackle. But this is just my speculation based on historical research and technical experience. I am not an engineer so any figures technical figures given regarding canterleaver pressures need to be confirmed.

[shipaholic]

Hi Dashicat

They did indeed do repairs to ironwork. They were not called blacksmiths but armourers. Here is a passage from Cook's Journal at Tahiti:

 

"Tuesday, 18th. Cloudy weather with some showers of rain. This morning took as many people out of the Ship as could possibly be spared, and set about Erecting a Fort. Some were employ’d in throughing up intrenchment, while others was cutting facines, Picquets, etc. The Natives were so far from hindering us that several of them assisted in bringing the Picquets and facines out of the woods, and seemed quite unconcern’d at what we was about. The wood we made use of for this occasion we purchased of them, and we cut no Tree down before we had first obtained their Consent. By this time all the Ship’s sails were unbent and the Armourer’s Forge set up to repair the Ironwork, etc. Served fresh Pork to the Ship’s Company to-day for the first time."

[JerseyCity Frankie]

Found some tiller images on the web. I find it helpful to look at actual examples of gear in cases like this. Even though these are modern replicas, you can see these are wooden rudder heads and tillers, and the forces involved are the same as would be found at any time in history. Clear in these examples are iron reinforcings and they come as no surprise.

Edited April 10, 2016 by JerseyCity Frankie

[dashi]

Steve: Thanks for this information and I stand corrected regarding the Armourer’s Forge and the Naval title for Blacksmith which I didn't know and hadn't come across this version of Cook's log. I see that Robert Taylor is listed as the Armourer on board the Bark Endeavour. Looking ahead in Cook's log from the link you provided I found this:

 

Wednesday, 25th. Winds and weather as Yesterday. P.M. set up the Armourer’s Forge to repair the Tiller braces, they being broke. By night we had got on board 12 Tons of Water and two or 3 Boats’ loads of Wood, and this I looked upon to be a good day’s work. The Natives gave us not the least disturbance, but brought us now and then different sorts of Fish out to the Ship and Watering place, which we purchased of them with Cloth, beads, etc.

 

So Cook here clearly mentions "Tiller braces" which indicates at least two. So he is not referring to tackles like I thought, but neither is he referring to the single brace depicted on the replica because there is only one of these. So could he be referring to the steel strapping on the rudder head of which there are several and which are depicted in the photo's provided by Frankie?

 

 

Thanks Frankie for providing these photo's of rudder heads. I've already looked at these and they do not have the metal tiller brace that I'm referring to which is in photo's of the replica, however yes they are reinforced with steel strapping as tiller heads of this era were and which in light of my recent discovery in Cook's log could have been the braces Cook needed to repair as I've indicated above. Unfortunately the tillers do not appear to be 8" square by 18 feet long from the head, but instead appear considerably shorter and smaller, looking to be only 4" square judging by the people's hands holding on to them so the vessels are probably also relatively smaller than the Bark Endeavour. In this case the forces involved would have been far less, about 1/4 less by my reckoning when compared to the forces in the rudder head from Endeavours tiller arm if it was unsupported. 

 

Cheers guys, this information is helpful.

[druxey]

I believe that 'braces' here refer to the gudgeon straps.

 

Steel, Naval Architecture,  page 11:

 

BRACES. Straps of iron, copper, or mixt metal, secured with bolts and screws to the stern post and bottom planks. In their after ends are holes to receive the pintles by which the rudder is hung.

[dashi]

Thanks Druxey. We might have made some progress today as it looks like we can rule out Cook's log as referring to that piece of steel on the replica which is bolted to the top of the tiller and passes up at an angle to under the rudder head housing. Still like to know what is hidden under that housing?

 

So the probability of using tackle to hold the tiller into the rudder head and an arced tiller support under the tiller as was done for tillers of this size still stands and is reinforced by the clarification of what those "Tiller braces" likely were that Cook repaired, unless evidence to the contrary comes to light.

[jud]

Turn the wheel righty and the stern goes lefty, turn the wheel lefty and the stern goes righty, rudders on the wrong end of the boat! 

jud

[dashi]

For clarification of what we are reffering to, then please read posts 14, 90, 91, 98, 99 and 100 while referring to the following link to a photo of HMB Endeavour replica's tiller housing showing the metal work I am refering to that is attached to the top of the tiller and which runs up into the housing which we have just established are not the iron tiller braces that needed repair in Cooks log. http://www.modelships.de/Museums_and_replicas/Endeavour/gIMGP3613.jpg

Edited June 11, 2016 by Dashi

[dashi]

I was qwereing steel being used .was steel used may be I am wrong robin

I think it might depend on where the metal is used as to what alloy was used, whether iron or brass or copper if you read through this museum documentation of the 1791 wreck of HMS Pandora.

 

https://www.google.co.nz/url?sa=t&source=web&rct=j&url=http://www.qm.qld.gov.au/~/media/Documents/QM/About%2520Us/Publications/Memoirs%2520-%2520Culture/C2-1/c2-1-campbell-gesner-part-a.pdf&ved=0ahUKEwif5tGi-4TMAhWh2qYKHWFGCC4QFggxMAk&usg=AFQjCNFcjgzdnR6RjmYtxhpj8p1wciIKEA&sig2=olbhWw9jo5gSo7WglJSSeQ

 

And in conjunction with the above artical the following artical gives the history of iron and it's uses on ships from the 1600's. It appears from this artical that iron smelting wasn't refined until the 1800's and up until that time it could be quite brittle.

 

http://www.maritime.org/conf/conf-goodwin.htm

Edited April 10, 2016 by dashicat

[jbshan]

In a couple of those pictures you can see what amounts to a fid through the tiller abaft the rudder head.  This holds the tiller in place, and being tapered as shown in the pics, you hammer it in farther if it works loose.

Note the tackle shown in some of the pics.  This is relieving tackle, the tiller was mostly moved by pushing on the tiller.  No wheel involved.

Port tiller (or helm) means starboard rudder.  This caused some confusion and now rudder orders coincide with the movement of the ship's head.

[jud]

 Ships pivot around the head from rudder movement, it is the stern that swings, that trait saved my ship 'the Ammen' from being cut in two during a collision, just enough time to start the swing, so the other ship slid down our Port side.  19 July 1960, USS Ammen DD 527, killed 11 injured 25.

jud

Edited April 11, 2016 by jud

[dashi]

Seems to be problems with posting links Robin as I can open these but some others from other peoples posts I can't. Not sure what the answer is?

 

So here is a technical drawing of a rudder from Greenwich Museum I was going to post a link to but will upload instead. It's dated 1830 and looks like it's indicating the different types of metal, but that could just be my interpretation. Also of particular interest is the ring on top of the head, could this have been to attach tensioning tackle to the tiller arm?

[mtaylor]

Dashicat,

 

I suspect that ring was use in shipping and un-shipping the rudder.