After just installing B&C BC460-H alternators, I ran into a consistent problem in mounting on the RV-14's IO-390 and I thought I'd mention it here in case any of you used that alternator on your install.
The issue is this: When you order the alternator for Boss mount, you choose if you have a dual groove or single groove pulley, and that determines which U-shaped boss mount bracket you get. The 2 brackets they have, have slightly different fore-aft hole alignments that determine how well the V-Belt centers in the grooves of both pulleys. If you are not in alignment you will for sure wear the belt worse, but also have a much higher chance of belt breakage.
When I ordered my alternators, I ordered the standard Single groove bracket because that's what I have on both my IO-390 and IO-540. My IO-540 is a narrow deck older engine, but my IO-390 is new from Lycoming in 2015.
In fitting the alternator to the engine, the only way you will get a good accurate look at the alignment is if you use some sort of alignment tool. Eye-balling won't get it, because you can move your head around an convince yourself that you're off to the forward side, dead on, or off to the aft side, all by just moving your head a little or switching eyes. Fortunately the alternators ship with a flat but dog-leg bent adjuster arm that makes a decent tool to verify the alignment. You can lift the alternator to its highest position, and run that tool around the large pulley and see where it hits in the alternator pulley.
On my IO-390, it hit about 1/3 of the way up the aft side of the v-groove slope. I tried multiple brackets to verify that they were drilled accurately and it was the same story. B&C gave me the hole measurements for their 2 brackets and based on the measurements I was skeptical that the dual-groove pulley would work also. It moved it twice as far as was needed to make it proper. I then went to do the install on my IO-540 and had the same issue but it was more severe. (which was good, actually)
So I had them send me 2 of the dual-groove pulley brackets. The dual groove bracket moved the hole exactly the right amount for my IO-540, which made that perfect. But, the dual groove bracket indeed moved the alignment too far on the IO-390. So, I was left with the only real solution(s) to be either:
1) Grind the alternator mounting hole on the alternator case and shim the alternator to align. (This would mean I permanently changed my alternators dimensions)
2) Elongate the holes in the Boss mount bracket to allow proper alignment.
I opted for #2 for now, but, it's an imperfect fix because now you have to worry about the bracket sliding forward if something shifts, so you would want to find a way to prevent that movement.
There is an option #3 that I'm going to explore and that's to see if I can get them to produce a 3rd bracket that has intermediate hole spacings, or, if I can have a bracket sourced that has no holes drilled. The down side to this is, if you drill them yourself you'll want them to be perfectly accurate because any mis-drilling will result in a potentially twisted alternator alignment that would also not be good. Also, one of the 2 holes is elongated by default so you'd have to drill and elongate that hole if you wanted it done as all other brackets are made.
I just wanted to mention it here, because I can't be the only one that this will affect, and if you just blindly installed your alternator without verifying the alignment, there's a high likelihood that yours is off too. My original Plane Power 60A alternator was perfectly aligned using the default bracket so the engine itself must be fairly standard, but I'm really not sure if B&C is perhaps fully aware of the various hole spacings that may be found in the field.
I will be doing a full write-up on the project when I get time and there will be pictures at that time.
The issue is this: When you order the alternator for Boss mount, you choose if you have a dual groove or single groove pulley, and that determines which U-shaped boss mount bracket you get. The 2 brackets they have, have slightly different fore-aft hole alignments that determine how well the V-Belt centers in the grooves of both pulleys. If you are not in alignment you will for sure wear the belt worse, but also have a much higher chance of belt breakage.
When I ordered my alternators, I ordered the standard Single groove bracket because that's what I have on both my IO-390 and IO-540. My IO-540 is a narrow deck older engine, but my IO-390 is new from Lycoming in 2015.
In fitting the alternator to the engine, the only way you will get a good accurate look at the alignment is if you use some sort of alignment tool. Eye-balling won't get it, because you can move your head around an convince yourself that you're off to the forward side, dead on, or off to the aft side, all by just moving your head a little or switching eyes. Fortunately the alternators ship with a flat but dog-leg bent adjuster arm that makes a decent tool to verify the alignment. You can lift the alternator to its highest position, and run that tool around the large pulley and see where it hits in the alternator pulley.
On my IO-390, it hit about 1/3 of the way up the aft side of the v-groove slope. I tried multiple brackets to verify that they were drilled accurately and it was the same story. B&C gave me the hole measurements for their 2 brackets and based on the measurements I was skeptical that the dual-groove pulley would work also. It moved it twice as far as was needed to make it proper. I then went to do the install on my IO-540 and had the same issue but it was more severe. (which was good, actually)
So I had them send me 2 of the dual-groove pulley brackets. The dual groove bracket moved the hole exactly the right amount for my IO-540, which made that perfect. But, the dual groove bracket indeed moved the alignment too far on the IO-390. So, I was left with the only real solution(s) to be either:
1) Grind the alternator mounting hole on the alternator case and shim the alternator to align. (This would mean I permanently changed my alternators dimensions)
2) Elongate the holes in the Boss mount bracket to allow proper alignment.
I opted for #2 for now, but, it's an imperfect fix because now you have to worry about the bracket sliding forward if something shifts, so you would want to find a way to prevent that movement.
There is an option #3 that I'm going to explore and that's to see if I can get them to produce a 3rd bracket that has intermediate hole spacings, or, if I can have a bracket sourced that has no holes drilled. The down side to this is, if you drill them yourself you'll want them to be perfectly accurate because any mis-drilling will result in a potentially twisted alternator alignment that would also not be good. Also, one of the 2 holes is elongated by default so you'd have to drill and elongate that hole if you wanted it done as all other brackets are made.
I just wanted to mention it here, because I can't be the only one that this will affect, and if you just blindly installed your alternator without verifying the alignment, there's a high likelihood that yours is off too. My original Plane Power 60A alternator was perfectly aligned using the default bracket so the engine itself must be fairly standard, but I'm really not sure if B&C is perhaps fully aware of the various hole spacings that may be found in the field.
I will be doing a full write-up on the project when I get time and there will be pictures at that time.