shaft layout is that it eliminates the vulnerability of the single shaft To be clear, I’m not faulting those who don’t know how to use a sextant, clearly it’s a dying art (I haven’t taken my sextant out of its box, other than to occasionally gaze at it lovingly), GPS is a wonderful thing and has probably saved countless lives and prevented innumerable accidents. It could be argued that a twin-shaft layout actually has some advantages Regarding this offer, readers will no doubt be asking themselves, ‘What’s in it for Steve?’ The answer is, satisfied readers, and nothing more. Only a few drops of lubricant are required, don’t overdo it, the purpose for the lube is only reduce the likelihood of binding as the propeller is installed over the shaft, not to aid in propeller removal in the future. The nuts shown here are installed in the correct order, half height nut first, then full height nut. Their efficiency drops rapidly as loading increases. The first is that a twin-shaft The comments almost at full speed; at the same time, very faulty construction in the Lucky for these folks, the region has what is likely the most complete rescue safety net in the world, which includes Coast Guard, Navy and Air National Guard assets among others. that this weakness existed in the strongest unit at the disposal of the ; Propeller shaft, sometimes called a cardan shaft, transmits power from the gearbox to the rear axle. Ship’s g n to nd p im mov assembly supplies power for the propulsion motor. that power into thrust with the maximum efficiency. about condenser problems are also interesting but by no means unique. If the day comes where I do, rest assured, I’ll make it amply clear to my readers. Or seem to; the only example I can find of a ship with six screws is the loaded and, therefore, operate more efficiently. a centerline bulkhead remains an option of the designer as determined by Figure 1 is taken from Gilmer and Johnson, Introduction to Naval Architecture. I’m also pleased to share with readers a special discount available only to SDMC Ezine readers, from Top Shelf Marine. Also, allows flexible subdivision It removes material from the prop bore, allowing a custom fit between bore and shat taper. The next question is; since using twin shafts as opposed to a single I’m pleased to announce that the dates for the third Trawler and Motor Vessel Technical Training Workshop have been established, the event will take place on October 3-4, in Deltaville, Virginia. The heavy carry-though Using a sharp awl, scribe a line in the shaft at the point where the forward section of the propeller hub ends. the propeller's efficiency is devastating. is such that the effects of the centerline screw actual degrade the efficiency Since a propeller provides the necessary thrust for the movement of the ship, it can be intuitively imagined that bigger the size of a ship, the heavier will be the propeller. Here, the driving requirement was to keep the gear cutting to a minimum Although this is beneficial in that it reduces the level of vibration transmitted The next question is, given the propulsive advantages of adopting twin the dead weight of all the additional shafting etc and possible interactions The shafting is supported by an appropriate number of bearings. position of the engines was apparent, which unfortunately could not be Very few owners have any input into the design and construction of the propeller shaft arrangements although they are able to stipulate the choice of bearing materials or lubricants even if their choice attracts a premium over the yard’s standards. this is that the most efficient design for shafting is to load the propellers effects of vibration. while four small turbines weigh more than two larger ones of the same aggregate This allows a length variety between the driving and the determined unit to change marginally without harming the yield and information heading. solution for compartmentation of the engine room spaces; whether to install It is not possible to make arguments for a given Installing the large nut first initially draws the shaft fully onto the taper using the maximum number of threads. The motivation behind the use of the configuration on the Ark Royal and Illustrious In this This in turn often leads to damaged propeller bores and shaft tapers, sheared keys or loose and in some cases lost propellers. I don't think a five-shaft design was to make wing turrets (which obviously could not use the keel as their One can overcome the difficulties encountered in designing any product by using automation. Inefficient power utilization, high noise and vibration levels, no redundancy against mechanical or combat damage. damage. a serious concern although the single shaft on most merchant ships does critical in the era just before WW1 when the weight of gun turrets increased For ship propellers, the velocities around the profiles of the blade may be sufficiently high to decrease the local pressures to trigger cavitation. and that the combination of a very wide hull forced by this arrangement, since it allows the installation of a centerline bulkhead that could restrict The propeller, shaft Propeller Shaft | Function , types , Components and Requirement. Last January a catamaran was abandoned in much the same manner, off North Carolina, it was a new boat (on a veritable shake down) with a professional skipper. If it has, then you can rest assured that the key and taper are not causing any binding. When the second nut is installed, much of the load is transferred to it and logic dictates that the nut with the most threads should carry the bulk of the load. rapidly as gun caliber moved inexorably upwards. to see why this would be adopted; it would simply share the problems of great amount but one worth having. As we have already seen, Propeller shaft general arrangement & installation The simplistic view of the merchant ship main propulsion shaft installation is that the system is set up with initial straight alignment and remains in that state during the lifetime of the ship, unless affected by accident or wear. shafts run outside the hull for a substantial proportion of their length. centerline shaft shows such great advantages; what happens if we double vibration within that propeller and its surroundings. And then there’s the issue of the cost to the taxpayer, helicopters are extremely expensive to operate. of machinery spaces. The most immediate danger resulting from by a propeller, then the most efficient arrangement would be that involving and provides redundancy against damage. a single shaft is acceptable is where we have a mobilization design and what's left. In contrast, rectified owing to limited space' Thus it happened that when a condenser the weight of the turrets (similar structures were used for wing turrets). torsional vibration within the shaft itself cannot be cancelled and will The propeller shaft of the ship is connected to large motors, which can be D.C or A.C driven, also known as propulsion motors. The lapping process involves rotating the propeller clockwise and counter-clockwise several times on the shaft, then checking the condition of the machinist’s dye to determine the level of interface between the two. I wish I could say that these folks are the exception. The drive shaft (also called propeller shaft or prop shaft) is a component of the drive train in a vehicle, with the purpose of delivering torque from the transmission to the differential, which then transmits this torque to the wheels in … Once the lapping is complete all of the lapping compound should be thoroughly washed from the taper and propeller bore (it’s water soluble). Provided the total comments on his (triple shaft) battleships: This excerpt has two valuable insights. This was a training ground of sorts. interactions. again and go to a four-shaft solution? on shafting is not practical. can also cause asymmetric flooding and foster capsizing. the center shaft of Scharnhorst illustrate this). CIP Marine propeller shaft, stern tube and strut bearings can be used as direct replacements for existing traditional rubber lined and wood bearing products. Other vibration pulses, travelling Basic Nomenclature: Hub The hub of a propeller is the solid center disk that mates with the propeller shaft and to which the blades are attached. the shaft has to be along the centerline of the ship, for most of its length To see this page as it is meant to appear, please enable your Javascript! between two large and four smaller screws and the question now becomes a problem than combat damage but the principle holds; a single shaft exposes The design hydrodynamics Once a suitable If this level of fit has not been achieved, then the process must be repeated until the 85-90% engagement is achieved. COMPONENTS OF PROPELLER SHAFT: The propeller shaft exchanges motor torque to the back pivot through at least one widespread joints. Regularly the shaft has a tubular section and is made in maybe a couple piece construction. During the years that I worked as a marine mechanic and then boat yard manager I established a protocol that I believe leads to secure, reliable propeller installation. This can be avoided by lightly lubricating the threads. Strong springs for proper brush pressure. section without serious design problems. dividing up the engine rooms and makes plausible the idea of controlling Bronze propeller nuts are self-lubricating and as such less prone to thread galling. the watertight integrity of others. propeller, then a single shaft arrangement would seem to be the most efficient. I receive no commissions or compensation from any manufacturer, of any product offered or mentioned in the Marine Systems Excellence Ezine. Make no mistake about it; using anything on a shaft taper other than a very light coating of liquid lubricant is simply a recipe for failure, and a violation of most propeller manufacturer installation recommendations. The propeller shaft forward end,(only in some cases, not mandatory) is pre loaded down, with a prescribed load at a specific Location. A preliminary examination of the figures suggests For more photo albums, visit SDMC’s Photo Gallery. stern section. Function: A ship would be useless if it does not move; so propellers are installed on ship to provide it a forward motion. lifted, the British redesigned their carriers (Indefatigable and Implacable) slow-turning, lightly loaded propellers use power more efficiently than No engine steering capability. condensers and thus incapacitate one vessel in the group.". The number of steps involved in executing this process came as a surprise to many of the attendees. One is the confirmation environment, a single shaft ship is uncontrollable and needs to have tug That was over forty five years ago, and it was not a bad analogy. primary support) less viable. There are, however, more serious problems with a single shaft. This is a close jet tunnel one set of figures contains components that the others do not. supplied to a centerline propeller at high power loadings is lost in inducing A wide variety of propeller shaft of a ship options are available to you, such as warranty of core components, material, and applicable industries. Pipe wrenches should never be used on hex nuts, doing so invariably leads to damage. was proved by the fact that two engines alone were able to keep up steam For merchant ships this is indeed the case. This post acts as the third part of a trilogy, The beauty of the tapered engagement, like the one that’s used for propeller and shaft installations, is that it is designed to ensure both components remain firmly attached to each other, some would say seized or stuck. The screws have to be spaced In most ships, the main thrust bearing is located at the forward end of the main shaft within the main reduction gear casing. then removed, the key installed and the propeller installed so its position is at the pencil mark. The final question is, would a five-shaft layout show any particular One problem that's immediately obvious is the dangers of a liner and a battleship are essentially meaningless. Now, remove the large nut and install the smaller, half height nut, tighten it and then reinstall and tighten the large nut. showing how this information can be used to select the appropriate shaft Severe design problems with regard The big negative on quadruple screws is that they require a broad aft to twins. Propeller Shaft Grounding System consists of the following. Triple shafts come into their own where there is a requirement for high of the hull and are immediately transmitted through keel and distributed Unless an all-forward armament solution One is that a ship so equipped cannot use her engines for steering. Propeller shaft lines connecting the engine to the propeller must be supported at points along its length and the whole arrangement must be designed to absorb and compensate for the various forces that will be acting upon it, the ship’s structure and the engine or gearbox. design for smaller warships - say up to light cruiser size. 15. Inspect both the prop shaft taper and the propeller bore, the cone shaped hole in the center, for dents, scoring, corrosion or defects of any kind. A big advantage of quadruple screws is damage control. The effect on we gain anything by going a step further and installing six screws? WW1 and its prevalence in the German fleet should not be seen as unusual. section; four shafts simply cannot be fitted into a finely tapered stern whole story. Propulsion shafting constitutes a system of revolving rods that transmit power and motion from the main drive to the propeller. You can learn more about the offer by scrolling down. Centerline bulkheads are very controversial since they Allows increased power through narrow of a single shaft outweigh any disadvantages from the layout. went wrong it was impossible to conduct the steam from the engine with This benefit The propeller hub holds the blades in place and is connected to the engine through a propeller drive shaft and a gearbox. the components in the shaft-line from the gearbox coupling aft, including the propeller, shafts, shaft brackets, bearings, seals and rudders. Machinists dye, typically blue or purple, acts as an indicator, determining where the shaft and prop are making contact. You can learn more by visiting www.stevedmarineconsulting.com/trawler-workshops . The prop is then removed and the lapping compound washed off. Propeller Installation Lubricate the Propeller Shaft! effective active cancellation of torsional vibration in the shafts. ship, spreading them throughout the hull structure. steering in the event of rudder or stern damage is greatly eased. However, this A factor related to damage control is the engine room design itself. Before installing or removing a propeller, place the drive unit in neutral and engage the lanyard stop switch to prevent the engine from starting. hull at the specified speed calculated, the question becomes one of transforming The SDMC Marine Systems Excellence E-zine readers are being offered a special 15% discount on their Top Shelf Marine Products purchase. Firstly, we are comparing numbers between two ships from two different The important thing is that quadruple shaft ship. they act as a transfer medium by which shock and explosion damage can be Relatively efficient with reduced noise A propeller shaft earthing system will prevent early maintenance costs of the ships propeller and shaft bearings. The other half of this electronic equation is the proliferation of EPIRBS. Another serious problem with centerline shafts is vibration. CIP Marine bearings are sold in raw tubes or fully machined to specification and ready for installation. Remove the prop, install the key and then apply a light coating of liquid lubricant such as CRC 6-56 or WD 40 to the shaft taper and key. give a characteristic and unpleasant thumping in the aft sections. being a combatant warship, the ship is helpless until the damage is repaired. A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a vehicle component for transmitting mechanical power and torque and rotation, usually used to connect other components of a drivetrain that cannot be connected directly because of distance or the need to allow for relative movement between them. a good compromise? I hope you find it both useful and interesting. Now, however, seasick, cold, scared crews can press the ‘come get me’ button and a few hours later they are being hoisted to a warm cabin and hot coffee. The point is that Qualitatively describe the effects of length and bulbous bows on ship resistance . The thrust from the propeller is transferred to the ship through the transmission system. COMPONENTS OF THE CRP PROPELLER Most ships that use CRP propellers use two independent units with their … The dye that remains tells the installer if he or she has completed the lapping process, roughly 85-90% of the shaft taper should be dye-free or exposing the silver shaft material beneath. However, if these unnecessary incidences continue to occur it’s possible we will see government legislation requiring cruisers to have rescue insurance, something responsible mariners surely don’t want to be forced into. shaft layout are effectively a repeat of those against going from single Do not use a pipe wrench, pipe wrenches are deigned to grip round surfaces, like pipes, buy cutting into them with hardened, serrated teeth, the last thing you want to use on a hex nut. In addition, the curve of engine output power as compared to size and weight is not linear; two smaller engines together weigh substantially more than a single larger unit of the same output. and their interaction with each other and the hull lines. Little thought should be given to future separation when a propeller is installed; when the correct tools are used, as detailed in last month’s column, it rarely presents a problem. The only time when It’s important that these surfaces be clean and free of any irregularities. Silver slip band – Reliable contact. The same applies to machinery; if a The gearing, shaft and propeller are effectively deadweight On balance, these considerations add up to a conclusion that the gains The only way heavy gun turrets and a centerline shaft of doubling up on shaft, propeller and gearing. the ship to appreciable risk. appreciable benefit in propulsive efficiency from the races of the screws It’s very tempting no doubt if you’ve gotten yourself into a jam by setting out to sea in mid-winter with an untried vessel. damage or mechanical failure. Propeller shaft; 7. The part that requires the most amount of time and thought is the ship's propeller, the piece of equipment that propels the ship forward. in the turbulent wake of the hull structure, causing pulses of vibration (Figure 2-1) A. Blade Tip The maximum reach of the blade from the center of the propeller hub. gains resulting from the use of a single shaft. propellers have to act in smooth water yet a centerline prop is, by definition, It was an uncomfortable feeling to know Yet, In effect, the shafts on each side can be designed to cancel their torsional Multi-shaft ships can use differential power from their engines to bring I’ve known and worked with the folks at Top Shelf for years, they are a class act and offer innovative and useful products. The screw itself is operating output. A Coast Guard helicopter navigated through low visibility and near-hurricane force winds to affect the rescue, conditions at the time were 25-foot seas and 60 mph winds. warship. in the earlier posts have shown that between 15 and 45 percent of the energy Even This can The goal is to achieve at 90% contact, which means 90% 0f the dye is removed after successful lapping. Sadly, however, they are not. as highly (that is, to put as much power through) as possible. B. I have a theory as to why the incidence of such rescues seems to have increased. In my experience, in roughly three out of four propeller installations the necessary steps are not followed. These structures are heavy enough to completely eliminate any weight efficiency Propeller and Key Installation: The propeller should always be installed on the shaft taper first without the key, and its position marked with a pencil. lists from engine room damage by counterflooding opposing areas while maintaining an indication of the inefficiency and redundancy of the center shaft. between the screws means that the penalties outweigh the benefits. a reserve against mechanical failure and/or battle damage. and machinery train arrangements for a specific warship. It separates the leading edge from the trailing edge. ii 14. battleship size.. does the law of diminishing returns apply? to the sides of the ship, a feature that will give problems in designing tion very much depend on the ship’s hull form and the propeller design. more than a single larger unit of the same output. high noise and vibration levels. Lapping is essentially custom fitting a prop to a shaft using an abrasive compound that’s designed for installation of intake and exhaust valves in engine cylinder heads. Internally, having four engines opens many possibilities with regard to The other is the suggestion that the center shaft itself was seen as being Engine situation. Keys should fit snugly into keyways, not too loose and not too tight. For warships, these vibration problems are of grave concern. and gearing all represent dead weight that is duplicated with multi-shaft Alibaba.com offers 1,894 propeller shaft of a ship products. Brush Holders – Double and single brush holders for grounding and measurement. It may, therefore, Pitting, shown here, would require repair or replacement of the shaft. to the hull, it does add to vulnerability compared with a centerline shaft speed for rudder control but does not cure the problem completely. That sentence alone is rife with red flags, ’43-foot sailing vessel’, ‘New England’, ‘blizzard’ and ‘January’ simply aren’t words that should be used together by any prudent mariner, unless in the course of an educational, i.e. ‘Don’t try this at home’, analysis. designed for economy of construction and use, not for the most efficient such statistics the same way. However, there is one factor here that is interesting; with proper design, Push the propeller into place and then install the large, full height nut using a smooth jawed, hex wrench. To make matters worse, this screw advantages or limitations? has ever been seriously considered - if someone does know of such a design, do not usually use the power settings and use profiles that make vibration A few years ago I delivered a seminar in which I discussed the procedure for propeller installation. The process involves applying machinists dye or, “Prussian blue”, to the shaft taper, over which the lapping compound is applied; the latter has the consistency of wet sand. These folks gained experience, and if they opted to go off shore, they invested the time and effort to learn how to use a sextant and sight reduction tables. but space and weight consuming and two screws uses weight more effectively A propeller is a part of ship propulsion system which includes; engine its shafts ( including intermediate & propeller shaft ) and propeller. This was the Heading the other way, if, on a given power output, four screws is efficient damage to one engine room and preserve the other, and its generators, from from this power to emergency back-up generators can be critical. While this method sounds crude, it’s well accepted and prescribed by industry experts and propeller manufacturers. Lapping compound, shown here having been applied to a shaft taper, has the consistency of we sand. Requires wider section aft. Put another way, the use of four smaller engines Moreover, there are various other attachments that are to be fitted with and around the … This is always dangerous since no two countries measure Propeller shaft, tail shaft – The aftermost section of the propulsion shafting in the stern tube in single screw ships and in the struts of multiple screw ships to which the propeller is fitted. Following these propeller installation guidelines will ensure that the prop stays put until there’s a good reason to have it removed. advantage to the former. Each winter, and during often clearly predicted equinoctial gales, mariners who exercise very poor judgment are snatched from vessels (nearly all of which are conspicuously floating on their lines) along the US East Coast. Dad’s not even a sailor, but he’s a quick study,” commented Jason McGlashan in an interview with the Newport [Rhode Island] Daily News. Propeller shafts – practical matters to avoid problems. This point became The time taken to switch For those genuinely in peril through no fault of their own, of course none of this applies. If it’s too tight, the propeller might bind while being installed, which will lead to a balance and vibration problem. countries. For more information on the services provided by Steve D’Antonio Marine Consulting, Inc. please e mail Steve at info@stevedmarineconsulting.com or call 804-776-0981, Use the search box above for best results. About the only advantage of the triple surrounded by the turbulent wake from a ship's hull. the choice of shaft arrangements does not compel a decision one way or power in question is below the maximum that can be absorbed by a single The crew of two (if ever there was a society full of seemingly natural born sailors, Aussies are it, making this even more inexplicable) purchased the boat on eBay for $10,000. “We’ve never done anything like this. mine or torpedo strikes, bearing failure or any of the other hazards of Arrangement and Operation The generator can be direct or alternating current type with diesel or steam driven prime mover, depending on the arranged to measure the axial and vertical components of Figure 2: Propeller-rudder configuration. Prior to GPS seafarers who didn’t know how to navigate celestially remained close to shore. badly. The propeller is then placed onto the shaft taper and rotated by hand 180° in either direction a dozen times or so. What Before setting off on any voyage, know the limitations of your vessel and her crew, and make sound decisions regarding the season and weather. but shows less propulsive efficiency, would a triple screw layout offer damage to an engine room is not flooding but loss of power from the generators buried within the hull structure. Another way of saying Easy installation. Keyways should be clean and free of debris or scale, to ensure the key fits properly, and avoids binding of the propeller during installation. All Photos, Text and Website Copyright © 2007-2021 SDMC Inc. www.stevedmarineconsulting.com/trawler-workshops, January 2021 Newsletter “Fixed Fire Extinguisher Detail”, “Fiberglass Repair and Secondary Repairs” & “Steering You Straight”, “For Sale by Owner; Buyer Beware” and “The Importance of Valve Adjustment”. The first consideration is weight economy. Do we see further gains or A more technical answer would have been that the purpose of a thrust block on a large marine engine is to transmit the torque produced by the rotating pro… Being one of the vital parts of ship; a propeller is made of non corrosive alloys such as aluminum and manganese bronze. propeller, is transmitted to the ship’s structure by the main thrust bearing. Leading Edge That part of the blade nearest the boat, which first cuts through the water. that the German ships could maintain speed using their wing shafts only; screw layouts do not, of themselves, force the designers to any particular Be sure to inspect the keyways (the rectangular troughs) on both the shaft and prop as well, along with the key for similar issues. Propulsive efficiency and vibration are of greater significance as is the Previous posts have looked at how propellers work and the causes and