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#1
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engine alignment
I have an engine alignment problem in that when my engine was taken
out of the boat in Port Sudan in the Red Sea, the mechanics who were not marine engineers did not align it properly when they reinstalled it. At lower revs it vibrates somewhat. It has four flexi-mounts that are bolted to two longtitudinal engine bearers and each is connected to the engine by a vertical threaded bolt. I would be very grateful if someone in the group could advise me the sequence or process of aligning it again. The yacht is now out of the water. The engine is a 37HP Nanni diesel with a "V" drive with a plastic flexicoupling between the gearbox plate and the propellor shaft plate. Thanks Peter Hendra N.Z. yacht Herodotus |
#2
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In article ,
Peter Hendra wrote: I have an engine alignment problem in that when my engine was taken out of the boat in Port Sudan in the Red Sea, the mechanics who were not marine engineers did not align it properly when they reinstalled it. At lower revs it vibrates somewhat. It has four flexi-mounts that are bolted to two longtitudinal engine bearers and each is connected to the engine by a vertical threaded bolt. I would be very grateful if someone in the group could advise me the sequence or process of aligning it again. The yacht is now out of the water. The engine is a 37HP Nanni diesel with a "V" drive with a plastic flexicoupling between the gearbox plate and the propellor shaft plate. You'll have to wait until the boat's back in the water, the rig is properly tensioned and things have settled for awhile. Then it's an iterative process of getting the height and angle closer and closer, eventually winding up with the shaft in the center of the shaft log and the drive plate exactly parallel on each axis. Then lock the mounts down. recheck and bolt the shaft together. Take the plastic piece out as you measure of course. It'll smooth things if you're a bit off, but you don't want to have it always flexing. -- Jere Lull Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD) Xan's Pages: http://members.dca.net/jerelull/X-Main.html Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/ |
#3
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If you are going to tackle this job yourself, you should pick up a
dial indicator gauge and an articulated, adjustable post to use with it. A magnetic base is convenient for working around engines. Your engine coupling should have been machined true when the engine was put together but needs to be checked. 1) Clean up the edges and faces of both coupling halves. Remove all paint and rust, and get them as smooth as you can. 2) Set up the dial indicator on the edge of the coupling and rotate the output shaft. There should be only a few thousandths change in dial reading as the shaft is rotated. If the coupling has a pilot and you can get the dial indicator to read on the edge, check that as well. It will be a better reference than outside of the flange but is tricky to keep the dial indicator on. 3) Set up the indicator on the face of the coupling and rotate. There should only be a few thousandths change here. If anything is seriously out of whack here, you should send the engine and both coupling halves out to be reworked. 4) Calculate the weight of the shaft from the first bearing or support. Multiply cross sectional area x length x .284 pounds per cubic inch. Divide by 2. Calculate the weight of the coupling half the same way and add. 5) Put a wire sling around the shaft as close to the coupling as possible. Lift with a scale in the line until the reading is as found in 4). Tie off shaft so scale retains that reading. 6) Put the indicator on the coupling edge, pilot (if any), and face and check as you did with the engine half. If anything is out of whack here, you should send the coupling out to be reworked. 7) Be sure the shaft is in the proper fore and aft position. Shim and adjust the engine until a feeler gauge (spark plug gap gauge works well) reads the same distance between the coupling faces all the way around. 8) Put a straight edge across the coupling faces at the 12:00, 2:00, 4:00 etc. clock positions to be sure the centers of the two shafts are the same. If the edges of the shafts are different sizes, you may have to use a feeler gauge between a straight edge on the larger one and the smaller. 9) Bolt and secure the engine mounting bolts. 10) Break for the day. If it's early, take a hike or go swimming. 11) Next day. Recheck all measurements. 12) Bolt up coupling. This must all be done in the water. On a sailboat, the rig should be tensioned. If there is a long distance between the stuffing box and the first bearing. You should unpack the stuffing box on land, calculate the shaft weight ignoring the stuffing box as a support point, and hang the shaft as described in 4) and 5). Then repack the stuffing box. When the boat is in the water. Recalculate and hang using the stuffing box as the first support point for the calculation. Even if you have a flexible coupling, you should get the shaft aligned as closely as possible. The exception is CV joints which need to have an intentional angular offset of several degrees for best life. -- Roger Long "Peter Hendra" wrote in message ... I have an engine alignment problem in that when my engine was taken out of the boat in Port Sudan in the Red Sea, the mechanics who were not marine engineers did not align it properly when they reinstalled it. At lower revs it vibrates somewhat. It has four flexi-mounts that are bolted to two longtitudinal engine bearers and each is connected to the engine by a vertical threaded bolt. I would be very grateful if someone in the group could advise me the sequence or process of aligning it again. The yacht is now out of the water. The engine is a 37HP Nanni diesel with a "V" drive with a plastic flexicoupling between the gearbox plate and the propellor shaft plate. Thanks Peter Hendra N.Z. yacht Herodotus |
#4
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After reading this I'm glad I have saildrives!
Of course,when I snag a pot I wish I had outboards! Roger Long wrote: If you are going to tackle this job yourself, you should pick up a dial indicator gauge and an articulated, adjustable post to use with it. A magnetic base is convenient for working around engines. Your engine coupling should have been machined true when the engine was put together but needs to be checked. 1) Clean up the edges and faces of both coupling halves. Remove all paint and rust, and get them as smooth as you can. 2) Set up the dial indicator on the edge of the coupling and rotate the output shaft. There should be only a few thousandths change in dial reading as the shaft is rotated. If the coupling has a pilot and you can get the dial indicator to read on the edge, check that as well. It will be a better reference than outside of the flange but is tricky to keep the dial indicator on. 3) Set up the indicator on the face of the coupling and rotate. There should only be a few thousandths change here. If anything is seriously out of whack here, you should send the engine and both coupling halves out to be reworked. 4) Calculate the weight of the shaft from the first bearing or support. Multiply cross sectional area x length x .284 pounds per cubic inch. Divide by 2. Calculate the weight of the coupling half the same way and add. 5) Put a wire sling around the shaft as close to the coupling as possible. Lift with a scale in the line until the reading is as found in 4). Tie off shaft so scale retains that reading. 6) Put the indicator on the coupling edge, pilot (if any), and face and check as you did with the engine half. If anything is out of whack here, you should send the coupling out to be reworked. 7) Be sure the shaft is in the proper fore and aft position. Shim and adjust the engine until a feeler gauge (spark plug gap gauge works well) reads the same distance between the coupling faces all the way around. 8) Put a straight edge across the coupling faces at the 12:00, 2:00, 4:00 etc. clock positions to be sure the centers of the two shafts are the same. If the edges of the shafts are different sizes, you may have to use a feeler gauge between a straight edge on the larger one and the smaller. 9) Bolt and secure the engine mounting bolts. 10) Break for the day. If it's early, take a hike or go swimming. 11) Next day. Recheck all measurements. 12) Bolt up coupling. This must all be done in the water. On a sailboat, the rig should be tensioned. If there is a long distance between the stuffing box and the first bearing. You should unpack the stuffing box on land, calculate the shaft weight ignoring the stuffing box as a support point, and hang the shaft as described in 4) and 5). Then repack the stuffing box. When the boat is in the water. Recalculate and hang using the stuffing box as the first support point for the calculation. Even if you have a flexible coupling, you should get the shaft aligned as closely as possible. The exception is CV joints which need to have an intentional angular offset of several degrees for best life. |
#5
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Jere Lull wrote:
In article , Peter Hendra wrote: I have an engine alignment problem in that when my engine was taken out of the boat in Port Sudan in the Red Sea, the mechanics who were not marine engineers did not align it properly when they reinstalled it. At lower revs it vibrates somewhat. It has four flexi-mounts that are bolted to two longtitudinal engine bearers and each is connected to the engine by a vertical threaded bolt. I would be very grateful if someone in the group could advise me the sequence or process of aligning it again. The yacht is now out of the water. The engine is a 37HP Nanni diesel with a "V" drive with a plastic flexicoupling between the gearbox plate and the propellor shaft plate. You'll have to wait until the boat's back in the water, the rig is properly tensioned and things have settled for awhile. Then it's an iterative process of getting the height and angle closer and closer, eventually winding up with the shaft in the center of the shaft log and the drive plate exactly parallel on each axis. Then lock the mounts down. recheck and bolt the shaft together. Take the plastic piece out as you measure of course. It'll smooth things if you're a bit off, but you don't want to have it always flexing. You must align the engine and prop shaft by adjusting the mounts as above so that the engine and prop shaft are pointing in the same direction, at the same height and lateral alignment. Additionally, you need to ensure that the prop shaft is aligned before you align the engine to it. First, make certain you do not have a bent shaft or warped prop. Most prop shafts can be wiggled around somewhat and you need to ensure that it is true and centered first. Keep in mind that on many boats the prop shaft and engine is set off to one side by possibly 1/8 of an inch to compensate for prop walk while proceeding straight ahead. All inboard propellors will vibrate at some speed, because of interference between the hull, the flow of water and the prop. After it is all set up, next time you yank the engine, consider unbolting the engine mounts themselves from the engine bed and pulling the whole works without disturbing the adjustment of the mounts, still attached to the engine. Worked for me because the mounts come out and can then be detached from the engine and reattached with little or no movement using the original holes, etc. Loose mounting holes, worn from repeated re-installation, are caused by improperly re-inserting threaded fasteners into holes without regard for cross threading. A screw should be turned backwards until the threads are percieved to 'click' into the established threads. Few workmen bother with this, and holes become sloppy, requiring filling and re-tapping. Some loose holes may be snugged up with heli-coils, or by coating the screw with wax and then filling the hole somewhat with epoxy, and then re-inserting. Improperly done, this can be a disasater if they need removing in the future. To assist, you must find or make some reference marks on the boat and then align the prop shaft and engine to the same spatial relationship, using the reference marks on the boat and measurements of the prop shaft and of the transmission shaft, using feeler gauges between the drive flanges. These are precise measurements to be sure, and while non too easy, are certainly not impossible. The alternative is to make adjustments underway, "tuning" the alignment for minimum vibration. Working around rotating machinery is very hazardous. You would make the adjustments at the worst vibrating rpms, taking note of eccentricities, possibly using a strobe light keyed to the ignition or some mark on the flywheel, or using a runout gague. Do not do this! A friend of mine would use the approach of loosening all the setscrew and then running the ******* hard and fiddling with it until it settled in or broke, then resetting the screws. I do not reccommend this, as in about half of the cases it would promptly fly into pieces. In the other half , it would take longer to fall apart. Sooner or later, he will lose an arm. My father in law, God rest his soul, a Canadian veteran of Holland, an old time horseman, woodsman and a farmer, would buy a bushel of parts, bolt them together loosely with locking wire, let it shake, and replace pieces whenever they broke. Many of our farms are run this way and while farmers survive somehow, there are many casualties. He is also reputed to have welded a steering knuckle on his tractor, using the starting battery, a jumper cable and a coat hangar. It got him home. He was scary in other ways, too. Good luck. Terry K |
#6
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Hi Peter
We overhauled the gearbox and replaced the engine mounts on "Leonidas" last year. This included the realigning of the engine mounts. We found the process easier than suggested by Jere, Terry, Roger and Jeff. We have engine mounts that are screw adjustable, and the front mounts are at 45 degrees so that there is a small amount of latteral movement. All are screw type adjustable like you have, and we also have a flexible 'Vetus' coupling on the propellor shaft. Because the coupling pad is soft, you have to remove it while you do the alignment, and align the metal to metal coupling surfaces. We did the initial aligning on the hard, (we had to get the yacht back to the marina on relaunching) and then realigned it in the water two weeks later. The process is as follows : * remove flexible coupling pad and loosely screw metal coupling flanges together. Prop shaft will slide both ways so you can remove the pad and then couple the metal flanges together. * With texture color mark four equally spaced reference points on the flange. ie 90 degrees apart. * With feeler gauges measure gap at each reference point and write down the results. (This is important as you can see the results of each adjustant, and it greatly shortens the process.) * Think about ajjustment to be made and then turn one adjusting screw one half a turn. Measure with feeler gauges and write down results. * Continue untill you get same result on the feeler gauge at each measuring point. (or within 3 thousandths of an inch. * Tighten locking nuts on engine mounts, recheck with feeler gauges. (Repeat if necessary). If OK reinsert flexible pad. * After launching and vessel has settled down, then remove flexible pad and recheck alignment. Adjust if necessary, and refix pad. We got Leonidas within 2 thou' on the hard, but she was about 11 thou out when we rechecked her after she'd been in the water for two weeks. Realignment took about five minutes plus another fifteen minutes each to remove and reinsert the flexible coupling as the bolts were not easy to reach. Re- reading above, I think it was easier to do than explain. Its not a difficult job. The only tools you will need are spanners, feeler gauge set and a good light. Fair winds Graeme sv "Leonidas" |
#7
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One word about the plastic flexicoupling they are not designed to correct
alignment. All the powertrain has to be correctly aligned first. Before you do anything check the cutlass bearing and the strut. If the cutlass bearing is loose and the strut out of line, bent or not anchored properly these have to be fixed using the proper sequence. After years of misalignment on my boat and countless attempt to correct it we used the following method: With the boat out of the water the engine was taking out. The shaft was removed. It was inspected. The shaft was found to be gouged by the set screws inside the flange connecting it to the engine. This had for effect to make alignment near impossible. A new shaft was used. The connecting flange was properly mounted and secured with the set screws on the new shaft with the proper key stock. The shaft and the flange were set up on a lathe. Then the flange was machined perpendicular to the shaft. After that the shaft with the flange already mounted were pushed through the hull. Then the engine was installed in line with the flange and the mountings adjusted. After having the fiberglass boat in the water for about two weeks the alignment was checked and minimum correction done. In my opinion, it is best to have the shaft and flange machined together. While you are at it you be rewarded to check the cutlass bearing and strut. In extreme case you may have to replace the cutlass bearing and rectify and strengthen the base of the strut. If you detect an hairline crack in the strut welded repair is not recommended. Replacing with a new one is much better. "Graeme Cook" wrote in message ... Hi Peter We overhauled the gearbox and replaced the engine mounts on "Leonidas" last year. This included the realigning of the engine mounts. We found the process easier than suggested by Jere, Terry, Roger and Jeff. We have engine mounts that are screw adjustable, and the front mounts are at 45 degrees so that there is a small amount of latteral movement. All are screw type adjustable like you have, and we also have a flexible 'Vetus' coupling on the propellor shaft. Because the coupling pad is soft, you have to remove it while you do the alignment, and align the metal to metal coupling surfaces. We did the initial aligning on the hard, (we had to get the yacht back to the marina on relaunching) and then realigned it in the water two weeks later. The process is as follows : * remove flexible coupling pad and loosely screw metal coupling flanges together. Prop shaft will slide both ways so you can remove the pad and then couple the metal flanges together. * With texture color mark four equally spaced reference points on the flange. ie 90 degrees apart. * With feeler gauges measure gap at each reference point and write down the results. (This is important as you can see the results of each adjustant, and it greatly shortens the process.) * Think about ajjustment to be made and then turn one adjusting screw one half a turn. Measure with feeler gauges and write down results. * Continue untill you get same result on the feeler gauge at each measuring point. (or within 3 thousandths of an inch. * Tighten locking nuts on engine mounts, recheck with feeler gauges. (Repeat if necessary). If OK reinsert flexible pad. * After launching and vessel has settled down, then remove flexible pad and recheck alignment. Adjust if necessary, and refix pad. We got Leonidas within 2 thou' on the hard, but she was about 11 thou out when we rechecked her after she'd been in the water for two weeks. Realignment took about five minutes plus another fifteen minutes each to remove and reinsert the flexible coupling as the bolts were not easy to reach. Re- reading above, I think it was easier to do than explain. Its not a difficult job. The only tools you will need are spanners, feeler gauge set and a good light. Fair winds Graeme sv "Leonidas" |
#8
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Gentlemen,
Thank you very much for this. I built the boat from scratch and installed, as engine bearers, two parallel angle irons so that the engine and its mounts could be slid forward and lifted out. We had a new engine installed by a yard in Brisbane 5 years ago but in sailing up the Red Sea we were motor-sailing behind the reefs south of Suakin (south of Port Sudan) when the damned thing suddenly seized solid. I could not even turn it with a large wrench applied to the crankshaft pulley. With nothing locally or even nearby but desert we had no option but to sail 50 miles day and night to the open sea across an area marked "uncharted" on the charts with dotted lines showing the possible position of reefs. The mechanics at Port Sudan, who were only truck mechanics, had to have the engine in and out in the same day otherwise customs duty was payable. Unfortnately they undid the engine mounts before I thought about it. When they stripped it at their workshop they found that a nut from the crankshaft had come undone and had jammed in some gear teeth. This from a new 2 year old diesel. When they put it back in we tested it at revs and everything was great. It was only when we put it into gear to leave that we found it was massively unbalanced which I corrected as much as possible by adjusting the threaded mounts. At cruising revs of 1800 it is OK. It is only at lower engine speeds in gear that it vibrates. Port Sudan is not a place for yachts to go. As the wind was coming directly out of the narrow, reef lined harbour mouth, and there was nowhere we could anchor 90 metres deep) we had to call for a tow by ba pilot boat. This was to cost us, with harbour fees nearly US$2,000. There was no way to get this money as the banks have no connection to our banking system. My lawyer couldn't send money due to a US embargo on funds transfer. We were very fortunate that the Chief Pilot was a religious man (I had to wait in his office while he finished his daily reading of the Q'uran) who argued on my behalf with the Port Captain that they should not be charging me but extending hospitality. They waived all fees and we became their guests, being taken to their homes and to their beduine relations in the desert. So much for a country where you are warned by your government not to go as it is deemed unsafe. The boat is now on the hard in Spain and I intend returning to get it ready for crossing the Atlantic from the Canaries at the end of this year so I am very, very grateful for all of your help. My wife and son (and for the moment, I) are back in Sydney as he had to start High School. I shall be sailing by myself, not by choice but because we have no option. Thankyou once again. It is wonderful also to look up a newsgroup where the Russian porn masters have not yet posted. A few religious zealots I can handle though I am mindful of the definition of a Christian who is "someone who fervently believes that the New Testament is a divinely inspired book eminently suited to the needs of his neighbour" Peter Hendra New Zealand yacht Herodotus |
#9
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In article ,
Peter Hendra wrote: At cruising revs of 1800 it is OK. It is only at lower engine speeds in gear that it vibrates. I don't know why an alarm is going off here, but it seems sorta strange that the vibrations are only at lower power settings. It's as if I heard about that symptom as an unusual circumstance a bunch of decades ago. For some reason, I'm thinking about an inbalance between cylinders, perhaps a bad gasket or a timing problem -- as if the timing is slightly too advanced in gasoline engine. In other words, something else might be wrong, so I'd get a good mechanic to look at it when I could. -- Jere Lull Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD) Xan's Pages: http://members.dca.net/jerelull/X-Main.html Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/ |
#10
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There were two reasons for "doing the job twice" re engine alignment
1. We had to motor two miles to an anchorage immediately on re-launching and needed reasonable alignment to do so. 2. The engine mounts always settle down a little after they have been use for a while and re-alignment is then necessary. Graeme sv Leonidas |
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