Alternator Belt Dust & Overheating
For as long as I can remember, the main belt has been spewing black dust all over the engine room. Along with the dust came an odor of burning rubber. Unpleasant. Annoying. Instead of really solving the problem, I masked it by installing a heavy duty belt from NAPA. This solved the burning rubber smell, but the dust continued to settle – all over everything – especially the alternator.
The other morning leaving Deltaville under power, I heard a loud “schnapp”, and wondered what I had just hit! I throttled back and looked over the side, but no floating log appeared. I smelled rubber, and saw smoke below. Immediately, I shut down the engine, and dropped the hook.
Upon opening the engine compartment, I saw the problem – the old broken belt trick. Pretty sneaky sis. No big deal, I have 2 or 3 spares. But I wondered why-oh-why that heavy duty belt broke.
I began monitoring the belt temperature with my infrared thermometer. To my surprise the belt temperature reached 350º quite quickly, and when I throttled up to 2400 rpm, the belt temperature rose above 450º. Concurrently, I noticed the alternator output had dropped to nearly nill… 5 amps plus or minus 2. Bad regulator? Too much belt dust build up on the windings? Overheating caused a short circuit? Oh bother.
Upon removal of the alternator, I saw, by spinning the pulley, that the shaft wasn’t straight, such that the pulley wobbled. So much so, that on one side, the fan blades nearly scraped the front body of the alternator. Clearly this was the cause of my overheating, dust-producing belt issues.
Fortunately, in Hampton VA, there was, close by, an alternator/starter repair shop by the name of Dixie. I hopped on my Dahon, and peddled my poor alternator over for a rebuild to the tune of $140, with the promise of it being returned to me in 23.5 hours. Not bad.
The following day – installation success. No more dust, plenty of power (amps), and normal belt temperatures. Cleanliness is next to Godliness when it comes to alternators. Keep ‘em clean, keep ‘em straight. For the record, this alternator is a Max Amp 137/116 amp alternator made by Ample Power on a Yanmar 3GM30 with a single V-belt.
Considering the initial cost of a K-rated 135 amp alternator, the cost to rebuild the unit was a bargain. L and I enjoy reading about your adventures. You are “out there living the dream” and we are sitting in front of computer “machines” wonder if the “machine” controls us or do we the “machine”. You are doing great. Keep on going. Fair Winds Rod
Ben,
Hey I was looking at the Dahon bikes. What model do you have? Still like it?
Cole
My Dahon MuXl is great. Been very reliable for almost 3 years now. I highly recommend them if you get an upper level model. You have to pay attention to what components they put on the bikes. Their cheaper models, are just that – cheaply built. Keep them greased and like all bikes – maintain them, an they will last a long time.
What do you suppose bent the alternator shaft? Are you running Gates Green Stripe belts? They are indestructable (but not immune to wobbly pulleys of course
Fair winds,
David
Hey Ben,
You were probably about 20 yards away from my boat when you went through Deltaville. Godspeed is at the Chesapeake Marine Railway.
By the way, I had massive amounts of black dust also. It turned out that I had just a little rust on the inside of the pulley. Amazing how much dust a spot of rust can produce.
If you are heading down the intracoastal, the anchorage at Portsmouth (just in front of the Portsmouth Naval Hospital) is a good spot to start the trip. If the Dismal Swamp Canal is open, make sure you leave the anchorage no later than 7am so you can get to the lock by 9am, then they open.
Mark Gearhart
Hi Ben , I was wondering what bent the armature shaft , too ?
Was the repair,,, to straighten out the shaft or replace the shaft ?
Do you carry a spare alternator ?
Did you have an alternator belt guard made to install over the alternator pulley fan blades, so that you could enter the engine room underway and under power without worry about bumping that pulley fan ?
Do you have a high amperage circuit breaker in the output cable-line from the alternator ?
Douglas
I think Ben was dealing with shot bearings on the alternator’s shaft, not a bent shaft. When the bearings go, the shaft can wobble and the pulley doesn’t stay properly aligned.
The question is what caused the bearings to go on a fairly new alternator?? There are lots of possibilities. The alternator’s pulley and the crankshaft pulley need to be aligned by shimming the alternator. If the belt tension is not enough, the belt slips, especially if the alternator is working hard. A slipping belt generates lots of heat that is transmitted through the pulley to the shaft and its bearings. Too much belt tension is hard on bearings on both ends. Ample Power, the supplier of Ben’s alternator, strongly recommend using Gates Green Stripe belts. They are much more flexible that the solid Yanmar belts, and so grip the pulleys better.
High output alternators like Ben’s sometimes use double, matched belts. If Ben’s smart regulator is the Ample Power SAR, he has the ability to set the alternator’s maximum output (and toggle it back to full output). With the Yanmar 3GM30′s modest HP, and his single pulley alternator, it might be a good idea to reduce the alternator’s maximum output to maybe 60A, especially if the batteries are fairly discharged. If the batteries’ resting voltage is low, say below 12V, the smart regulator will allow the alternator to go to maximum output, assuming the engine rpm’s are high enough.
I think this discussion belongs on the BCC forum, so I’m going to copy and paste it there, and Ben and others can choose where to comment.
Dan
Hey Ben,
Good to meet you the other night. Look forward to next time!
We’ll put links to you and Teresa’s sites on ours.
Ya’ll are the first sailors we’ve met who are documenting your travels so well.
Garth and Sarah
I have a Yanmar 3GM30F and run a Powerline 150 amp alternator on a single pulley with no problems at all. I use a Gates Green Stripe belt for it and have never had a problem. I think dual belts are very difficult to adjust equally since the are not on separate pulleys, one is susceptible to doing more work than the other.