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Post by Deleted on Sept 21, 2022 11:04:07 GMT
was an earth strap ever connected? I suppose there must be some connection to the starter motor for it to work, or was it an insulated alternator. Can't remember. If the alternator wasn’t grounded the bulb wouldn’t light up. Yes but the bulb only requires a tiny current. It could be earthed "enough" to light the lamp but not pass a high current from the alternator.
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Post by kris on Sept 21, 2022 11:18:35 GMT
If the alternator wasn’t grounded the bulb wouldn’t light up. Yes but the bulb only requires a tiny current. It could be earthed "enough" to light the lamp but not pass a high current from the alternator. There’s a seperate negative cable to the battery negative. ( thick cable. )
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Post by kris on Sept 21, 2022 11:19:48 GMT
Have you done the obligatory voltage tests to be certain about the connections? Seems odd if there is nothing unless the belt wrap is just not enough on the alternator pulley. That’s a good point about checking voltage on back of the alternator.
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Post by Telemachus on Sept 21, 2022 11:53:09 GMT
Have you done the obligatory voltage tests to be certain about the connections? Seems odd if there is nothing unless the belt wrap is just not enough on the alternator pulley. That’s a good point about checking voltage on back of the alternator. You would expect about 1 to 2 volts on the D+ terminal with the switch on but not rotating. Otherwise of course it is battery + and -. However checking voltages when no current is flowing can be deceptive.
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Post by Deleted on Sept 21, 2022 11:59:48 GMT
yars ago when I had a Russell Newbery DM2 the alternator had a habit of not extinguishing the indicator lamp / exciting the alternator until the engine was revved up. I got around this by replacing the lamp with a Lucas horn switch which when pressed excited the alternator regardless of the engine rpm. A momentary switch not an on-off toggle.
This was 25 or more yars ago and my memory is not what it was. I hesitate to suggest it (and if you die horribly don't come running to me to complain) but what happens if you momentarily join the wires to the indicator lamp when the alternator is spinning. Does anything happen?
Also do you have a proper DC clamp meter for the charging cables?
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Post by kris on Sept 26, 2022 13:53:20 GMT
Just a quick update to let anyone interested know where I’m at with it. The gentleman modifying the alternators for me hasn’t finished the second one yet, it should be weds. I talked to him about the belt situation and he’s going to sort out two different pulleys for the alternators. Slightly larger diameter and width. Hopefully this will sort out the situation. Another route is to try one of the newer Link belts because this brammer belt stretches like a very stretchy thing. Apparently some of the newer ones aren’t so bad. I’ve also thought about improving the tensioning on the alternators ( I’d appreciate it if Andrew could post a link or photo of the things he’s always going on about.)The final solution if these don’t work is to fit continuous v belts that are the correct length.but this entails unbolting the gearbox every time I need to change a belt, so I really hope I don’t have to resort to that.
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Post by Jim on Sept 26, 2022 14:38:51 GMT
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Post by kris on Sept 26, 2022 15:00:07 GMT
something like that for sure.
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Post by Telemachus on Sept 26, 2022 15:41:24 GMT
Just a quick update to let anyone interested know where I’m at with it. The gentleman modifying the alternators for me hasn’t finished the second one yet, it should be weds. I talked to him about the belt situation and he’s going to sort out two different pulleys for the alternators. Slightly larger diameter and width. Hopefully this will sort out the situation. Another route is to try one of the newer Link belts because this brammer belt stretches like a very stretchy thing. Apparently some of the newer ones aren’t so bad. I’ve also thought about improving the tensioning on the alternators ( I’d appreciate it if Andrew could post a link or photo of the things he’s always going on about.)The final solution if these don’t work is to fit continuous v belts that are the correct length.but this entails unbolting the gearbox every time I need to change a belt, so I really hope I don’t have to resort to that. Obviously having to unbolt the gearbox to change the belt isn't ideal, on the other hand we have done 4400 engine hours and only changed the belts once so it would not be something that you had to do often - presuming the alignment was good in the first place, and that the belt size matched pulleys etc.
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Post by Deleted on Sept 26, 2022 16:14:19 GMT
Yes I used a bottle screw for this job once. You do need a real one not mickey mouse.
Eta if you can change pulleys it might be worth putting on a polyvee type belt instead of a vee belt. I seem to recall that vee belt will go up to about 1.5kw so 100 amps at 15v whereas a polyvee will do double that happily and probably last a lot longer.
Beta marine for example use a single vee belt for the standard (70a?) Alt and a polyvee for the 175a optional extra alternator (12v). They also have a nice threaded rod based tensioner for the big alt.
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Post by kris on Sept 26, 2022 16:45:11 GMT
Just a quick update to let anyone interested know where I’m at with it. The gentleman modifying the alternators for me hasn’t finished the second one yet, it should be weds. I talked to him about the belt situation and he’s going to sort out two different pulleys for the alternators. Slightly larger diameter and width. Hopefully this will sort out the situation. Another route is to try one of the newer Link belts because this brammer belt stretches like a very stretchy thing. Apparently some of the newer ones aren’t so bad. I’ve also thought about improving the tensioning on the alternators ( I’d appreciate it if Andrew could post a link or photo of the things he’s always going on about.)The final solution if these don’t work is to fit continuous v belts that are the correct length.but this entails unbolting the gearbox every time I need to change a belt, so I really hope I don’t have to resort to that. Obviously having to unbolt the gearbox to change the belt isn't ideal, on the other hand we have done 4400 engine hours and only changed the belts once so it would not be something that you had to do often - presuming the alignment was good in the first place, and that the belt size matched pulleys etc. I’m hoping not to have to do this but it’s looking likely that I might have to.
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Post by kris on Sept 26, 2022 16:48:23 GMT
Yes I used a bottle screw for this job once. You do need a real one not mickey mouse. Eta if you can change pulleys it might be worth putting on a polyvee type belt instead of a vee belt. I seem to recall that vee belt will go up to about 1.5kw so 100 amps at 15v whereas a polyvee will do double that happily and probably last a lot longer. Beta marine for example use a single vee belt for the standard (70a?) Alt and a polyvee for the 175a optional extra alternator (12v). They also have a nice threaded rod based tensioner for the big alt. unfortunately I can’t change the flywheel attached to the engine. This has single v grooves in it. So a poly v or any other kind of belt is out of the question. It’s looking like at worse I will have to unbolt the gearbox. It’s only a matter of sliding it a little bit to let belt fit through then slide it back and bolt it up again. But I’ll try to avoid this if I can. If you can find a photo of the kind of tensioner your on about I’d appreciate it.
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Post by Deleted on Sept 26, 2022 16:57:52 GMT
It was similar to the one Jim linked to earlier. M10 or M12 with eyes at both ends.
I think a poly vee belt will run on the flat surface of the flywheel. With the ratio you mentioned previously it seems likely that the weakness will be the belt wrap on the alternator pulley.
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Post by Deleted on Sept 26, 2022 17:00:35 GMT
Bottle screw porn: www.ebay.co.uk/itm/1641047356441 metre long ex navy £25. Nice item! 6 tonne SWL probably a little over the top for an alternator but this is exactly the same pattern as the one I used.
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Post by kris on Sept 26, 2022 17:00:55 GMT
It was similar to the one Jim linked to earlier. M10 or M12 with eyes at both ends. I think a poly vee belt will run on the flat surface of the flywheel. With the ratio you mentioned previously it seems likely that the weakness will be the belt wrap on the alternator pulley. it’s not a flat surface it’s got v’s in it. Yes this is why I’m going to try slightly larger pulleys on the alternators. I could drop the ratio down to about 6-7 to 1.
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