Guest 000 Posted October 13, 2015 Share Posted October 13, 2015 I have a slight alternator mis alignment judging by the small amount of black powder adjacent to the alternator pulley. The problem is the crankshaft pulley is a conventional solid type pulley whereas the alternator pulley is one of those one-size-fits-all pressed steel jobs where the outside edges flare outwards. This makes using a straightedge across the pulleys impractical. Does anybody have a cunning trick for accurately aligning pulleys? Thasnks Quote Link to post Share on other sites
wheels 543 Posted October 13, 2015 Share Posted October 13, 2015 Could be misalignment. Could also be belt slipping due to too much load on the belt, wrong belt profile, or a cheap poor quality belt.The easiest way to check is look down along the belt. You should see the belt around the pulley and continuing on down in a straight line to the other pulley. Misalignment will cause a small kink in that line at where the belt leaves the pulley. You can also do the same with a length of string. Quote Link to post Share on other sites
Guest 000 Posted October 13, 2015 Share Posted October 13, 2015 It's an 11mm Gates belt driving a 56amp alternator, so I think belt quality is OK and not overloaded by the relatively small alternator. I am familiar with the string method but the problem is there is not really enough room between the top of the engine and the bottom of the cockpit floor for me to get my head in and eyeball it properly. Especially being long-sighted.. The only solution I can see is to replace the pressed metal alternator pulley with one which has the same profile/flange thickness as the crankshaft pulley and then use a straightedge across the pulley faces. I was hoping for an alternative fix to save me the expense. Quote Link to post Share on other sites
John B 106 Posted October 13, 2015 Share Posted October 13, 2015 Notch or pack a batten of something straight and of the length outside to outside, and eyechrometer or measure from that whether the pulleys are out of alignement . If the mount looks good you could start by assuming that its square to the drive, so it might just be a matter of a washer or three to bring the centres into line. I used to find excessive wear on my alternator belt when the battery was old . It always needed great lumps of juice into it so wore out the belt. New battery , problem went away. Quote Link to post Share on other sites
wheels 543 Posted October 14, 2015 Share Posted October 14, 2015 Don't you just love it when you can't get at all the important regular maintenance items. I reckon a special kind of hell awaits designers that such things. They will be given a limited time(always just a few seconds short of the actual repair time) to fix one of the things they designed and when they fail, they get a good jab with a red hot pitch fork. Yeah a 55A alt will be fine on a single pulley. Sorry I don't know what measurements relate to belt width and belt ID. I use the letter, A B, M etc.. When pulleys are under 40mm in diameter, I use a notched belt to ensure the belt fits well around the small pulley. Remember that a correctly fitting belt is driven and drives pulleys by its sides, NOT by the inside flat of the belt.I Quote Link to post Share on other sites
John B 106 Posted October 14, 2015 Share Posted October 14, 2015 "Remember that a correctly fitting belt is driven and drives pulleys by its sides, NOT by the inside flat of the belt." sounds like the fit of my jeans. Quote Link to post Share on other sites
Guest 000 Posted October 15, 2015 Share Posted October 15, 2015 Well, I'm going to put myself to huge expense and change the alternator pressed steel pulley to a proper machined job that will enable me to use a straightedge across the flanges. I don't think these pressed steel flanges with a couple or three washers in between depending on belt size are much good. Although the bearing surfaces of the flanges appear true, the outside rolled edge lip is not meaning straightedge alignment is impossible. Since this would appear the only way to line everything up, I don't see any alternative. Oh, bother! Quote Link to post Share on other sites
wheels 543 Posted October 15, 2015 Share Posted October 15, 2015 Chris, before you go to that trouble.The little bit of rubber maybe normal wear. Even correctly aligned Belts wear. It is normal to see belt rubber settle on anything under the belt.Is the ALT not the original?How many hrs has it done on this engine? Quote Link to post Share on other sites
Guest 000 Posted October 15, 2015 Share Posted October 15, 2015 Wheels, I'm pretty sure that the engine (Perkins Parama) would have originally come with a 15-20 amp alternator, probably painted blue like the rest of the engine, so I conclude that the present 56 amp Bosch alternator is an upgrade. I don't know how many hours are on it, but when I bought the boat 4 years ago the front bearings in the alternator promptly collapsed, requiring a rebuild. This together with the belt dust leads me to suspect an alignment problem. The main thing that really niggles me is that the present setup, space, pulley type etc, prevents me from accurately determining alignment. Part of being an eccentric. Quote Link to post Share on other sites
erice 732 Posted October 15, 2015 Share Posted October 15, 2015 after fitting a brand new engine a year ago the only signs of wear are black alternator belt dust and flaked paint on the crankcase nut esp. new soft belts, seem to shed a bit of dust until they "custom fit themselves to their space" + harden up to check alignment could you drop a steel straight edge into the pulley grooves and then measure across to the front of the engine face or even easier, slip some rectangular wood? blocks between the straight edge and the engine? got to be lots of ways to do it clamp a bit of wooden dowel, alloy tube, steel rebar into the pulley grooves and put a set square against them to sight against another tube set against the rocker cover? , Quote Link to post Share on other sites
Guest 000 Posted October 15, 2015 Share Posted October 15, 2015 Got to love this forum for it inexhaustible wealth of ideas. I found that dowel thin enough to lay in the pulley grooves was a bit too bendy, but some alloy 9mm tent poles were ideal. They fitted into the crankshaft pulley groove nice and firmly and it was a simple matter to rotate the pulley slightly until the tent pole contacted the alternator pulley. This showed the alternator to be in line fore and aft and athwartships. Next step was to put another tent pole across the bottom of the pulleys and hold the two poles (top and bottom) in place with a couple of rubber bands. I couldn't fit my head between the top of the engine and the cockpit floor to sight down on the poles so used a small spirit level with an adjustable bubble. This showed the alternator to be a bit nose down, caused so I discovered by the front mounting bolt being a bit sloppy. Probably a metric bolt in an imperial hole, but easily fixable. Problem solved. Thank you all. Quote Link to post Share on other sites
wheels 543 Posted October 16, 2015 Share Posted October 16, 2015 Good to hear you have it sorted.By the way, 55A is the normal size ALT on these things, so could have been original. ALT's have a standard of design. I don't know of any that are just close to one another. Any differences would be quite dramatic. You can get a 55. 60, 80 all in the same body type and fixing points for instance. Quote Link to post Share on other sites
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