Alternator Alignment

[britinusa]

I have spent hours reading/watching anything I can about the alignment on our M25-XP engine.

Copying images from Mainesail's site http://www.pbase.com/mainecruising/universal_alternator_bracket&page=1

The engine does have the critical alternator upgrade.

The manifold bolts are longer as on Mainsail's site.

The Alternator Bracket is positioned fully aft (at least I think it's fully aft, as no slot is visible in front of the mounting bolts but the slot is visible aft of the bolts)

There are no shims

When viewed from above with the lower steps in place as a reference beam, the belt appears to be at an angle to the beam.

Mainesail's image looks like this:

My situation is the opposite! The belt is angle aft from the alternator to the coolant pump. ie. Looking down at the belt, more of the belt is visible astern of the lower steps near the coolant pump pulley compared to the visible belt at the alternator pulle.

All three of the pulleys (main shaft, coolant pump and alternator) are of the billet machined type, not pressed steel.

Any ideas on how I can move the Alternator Aft in order to improve the alignment (and thus reduce the belt dust)

Thanks.

Paul

[mainesail]

What model alternator is it?

[Noah]

What makes you think your stairs are a square/straight edge?

[KWKloeber]

Paul I think you need to ck with a straight edge against the pulley faces and go from there. If you had to, you could take some off the back of the shoe and shim the front.

kk

[britinusa]

So, basically, suggesting that I use a straight edge on the face of two pulleys to see if they are aligned?

Paul

[KWKloeber]

 Paul,

Correct. Spanning across the face of the fixed pulley, extended over to the alternator pulley. First it will tell you if they are in line, And then additionally whether the alt pulley is cocked.

[britinusa]

Ok, Sunday we'll do that with a Straight Edge.

Paul

[Ron Hill]

Paul : You need to take your straight edge and seat it on the lower drive pulley with touching both sides of the pulley.  Then adjust the alternator so the straight edge touches both sides of the alternator pulley while staying seated on the drive pulley.

From your picture it looks to me (eyeball wise), like the alternator needs to be moved fwd.  Eyes can lie, but a straight edge doesn't!!

My thought

[Stu Jackson]

Paul,

I'm sure you've seen this, but just in case...

Universal M-25 & M25XP Alternator Bracket Upgrade & Alignment 101 IMPORTANT

http://c34.org/bbs/index.php/topic,7917.0.html

My picture of the "after" shows that lining up with the stairs is NOT what you are looking for.

[britinusa]

From your picture it looks to me (eyeball wise), like the alternator needs to be moved fwd.  Eyes can lie, but a straight edge doesn't!!

My thought

Ron, that pic is from Mainesail's site.

My situation is the opposite, the belt is angled the other way.

I'll be at the boat Sunday and will straight edge it as Ken suggested.

Also, I dug through my photos and found this one, taken before I did the engine harness replacement and major engine clean up.

It shows how the alternator is mounted using a large spacer between the ears of the mounting bracket.

I could get that spacer machined down (or replaced) and add a skinny one in front of the alt mounting ear.
That way it would move the alt aft and I could then use the slots on the mounting bracket to align the alternator.

I think it's an 85amp alternator. Can't find the pic that shows the label.

Paul

[britinusa]

Paul,

I'm sure you've seen this, but just in case...

Universal M-25 & M25XP Alternator Bracket Upgrade & Alignment 101 IMPORTANT

http://c34.org/bbs/index.php/topic,7917.0.html

My picture of the "after" shows that lining up with the stairs is NOT what you are looking for.

Absolutely! Ron's(Mainesail's?) site is a huge help.

[mainesail]

Paul : You need to take your straight edge and seat it on the lower drive pulley with touching both sides of the pulley.  Then adjust the alternator so the straight edge touches both sides of the alternator pulley while staying seated on the drive pulley.

From your picture it looks to me (eyeball wise), like the alternator needs to be moved fwd.  Eyes can lie, but a straight edge doesn't!!

My thought

Not all crank and alt pulleys have the same material thickness on the front side of the pulley. As such the optimal way of doing this is to clamp a known straight edge to the crank pulley and extend it slightly beyond the alt pulley. I use a piece of aluminum L channel or aluminum square tube. If the front side of the alt pulley is thicker than the crank pulley, as in the double belt pulley pic above, a square shim exceeding this offset, can be placed under the straight edge before clamping it to the crank pulley. The measurement will be the same, straight edge at crank to fore edge of belt. Repeat at alt end. The two measurements should match. Because pulley dimensions, ahead of the belt vary, you want to measure from straight edge to edge of belt not align the pulley faces fore / aft..

Once clamped in place you are first measuring the distance from the straight edge to the edge of the belt at the crank. You then measure this distance at the alt pulley end. If the fore edge of the alt pulley is thinner than the crank there will be a gap between the fore face of alt pulley and the straight edge, which is fine. The measurement that matters is straight edge to fore edge of belt. Once you know the alt fore/aft alignment is good you can then measure for squareness by measuring straight edge to pulley on both sides, eg: closest to crank side and opposite crank side.

[britinusa]

Thanks Maine Sail.

I'm heading down to the boat this morning armed with clamps and straight edge and digital calipers.

Will take pics.

FYI, all of the pulleys are double similar to the one shown, but I totally understand your point and should focus on the alignment of the belt, not the pulley although the pulley alignment (twist) is also something to be reviewed.

Really appreciate your input.

Paul

[Ron Hill]

Paul : Sorry, the instructions that I gave were for a single pulley, as I didn't realize that you had a double pulley!! 
You should follow Mainsails instructions or
you could go to Balmar (Looks like you have a Balmar alternator?) and purchase a single pulley.  Then with a single pulley you can play around with spacers/washers to gain the correct alignment. 
I say go to a single pulley also because you might be running into problems if that double pulley on the alternator moved FWD starts to touch the steps?!?

A few thoughts

[mainesail]

Paul : Sorry, the instructions that I gave were for a single pulley, as I didn't realize that you had a double pulley!! 
You should follow Mainsails instructions or
you could go to Balmar (Looks like you have a Balmar alternator?) and purchase a single pulley.  Then with a single pulley you can play around with spacers/washers to gain the correct alignment. 
I say go to a single pulley also because you might be running into problems if that double pulley on the alternator moved FWD starts to touch the steps?!?

A few thoughts

Again crank pulleys are very often different from alternator pulleys in the distance from the edge of the pulley to the center-line.

Straight Edge Clamped to Crank Pulley Extending to Alternator Pulley:


Measurement from Straight Edge to Edge of Belt at Crank Pulley:


Measurement from Straight Edge to Edge of Belt at Alternator Pulley:


Gap Between Straight Edge & Alt Pulley:


This gap is because alt pulley face is not the same thickness as the crank face.. If we lined this alt pulley up with the crank, using a straight edge against both faces, the alignment would be off.

The straight edge just needs to be square with the crank pulley. Once it is, the measurement is from the straight edge to edge of the belt at both ends. Lining up pulley faces can often lead to problems because the pulley center-lines are not always the same from the fore edge of the pulley.