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Discussion Starter · #1 ·
When some ask you what the disc on the front of the alternator is for, most of us say to keep the water out it. It is designed to keep the belts from bouncing around and hitting the fins plus help the fins from bending out catching the belt. I had hurt 2 belts because the fins were bending but after the disc, that problem was over. I'm not sure if it helps us in the rain but at least we feel better.

Adrian
 

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I don't know Adrian, you never see a disk on a stock alternator on anything other than a Boss Hoss, it's got to be for the rain.
 

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Discussion Starter · #3 ·
Rain sounds good to me however you won't see any pulley's that are as small as the Boss Hoss's due to the needed RPM's at idle with all the stuff that is running with electricity. Most folks believe that and works for me but the reason the factory put them on was to stop the belts from being tore up. My friend talked to Monty long time ago about his over heating with his clutch bike. He told Monty that he had done nothing at all but change the pulley to a billet one. He was told to change it back to the small one and use the disc.
I was talking to Marv yesterday about this and he also said "The reason was to save the belt."

Adrian
 

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Must be because GM uses a disc on all of the later model alternators that use a serpintine drive belt. Ford uses no disc or fins.
 
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Alternator Disk

The disk between the alternator fan and belt pully is to augment the air flow through the alternator, the air flows aft forward to cool the rectifier bridge heat sink, then over the armature, and out the front through the fan blades. If you use a small pully it lets the air from the front of the fan come in from the center and out the blades reducing the air volume through the alternator case. Add to this a 70 m.p.h. breeze going the opposite direction working aginst this flow, and the alternator over heats and burns out the diodes in the rectifier. The disk blocks the air from the front, and forces the fan to pull a high speed column of cool air through the alternator case. It also works as a slinger for water that is coming fronmthe front of the bike. This is a very important item to have on a Boss Hoss. Bill Alexander
 

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Re: Alternator Disk

Sounds like you might know what your talking about. ;) Welcome to the site Bill.

Bill ALEXANDER said:
The disk between the alternator fan and belt pully is to augment the air flow through the alternator, the air flows aft forward to cool the rectifier bridge heat sink, then over the armature, and out the front through the fan blades. If you use a small pully it lets the air from the front of the fan come in from the center and out the blades reducing the air volume through the alternator case. Add to this a 70 m.p.h. breeze going the opposite direction working aginst this flow, and the alternator over heats and burns out the diodes in the rectifier. The disk blocks the air from the front, and forces the fan to pull a high speed column of cool air through the alternator case. It also works as a slinger for water that is coming fronmthe front of the bike. This is a very important item to have on a Boss Hoss. Bill Alexander
 

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I have run a full custom made alternator and pulley cover for 28,000 miles and have never had an alternator problem or even seen the alternator wet despite many, many rain miles. The alternator is completely shieded from dirt, rain and wind for that matter. I never realized that shielding it from the wind could be actually helping the fan blades by not fighting their function.

Adrian..you stated that the Boss needs a smaller diameter alternator pulley because of all the electrical stuff (fuel pump, water pump) but what about the power needed to run a car with four xenon headlights, fog lights, interior lights, 330 watt stereos, navigation systems, power seats and windows, heaters and air conditioners. My current car which is loaded with every imaginable electrical device should need an alternator the size of Montana or a pulley 1/4" in diameter.
I really don't understand. It would seem that the electrical demands of the Boss pale by comparison.......Joe
 

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Discussion Starter · #9 ·
Bill
No doubt they are a good idea but I'm sure that Marv at Chopper City is all wet, but I place my money on his knowledge about the disc anyway.

Joe has the right idea and you are correct about the air flow.
 

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What about putting the disc directly in front of the pulley right after the nut? Wouldn't it help keep debris from hitting the pulley/belt along with creating a "wider" wind block?
 

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Discussion Starter · #14 ·
hozztil said:
What about putting the disc directly in front of the pulley right after the nut? Wouldn't it help keep debris from hitting the pulley/belt along with creating a "wider" wind block?
Marv says that the blades straighten and will tear off the belt. It did it to mine but I didn't realize that was the problem.

Adrian
 

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They all come stock with the double pulley setup. Don't tell me you don't have that on your bike. :shock:

zenbiker said:
Lamont....What's that double pulley setup you posted? Never seen that before...Joe
 

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I was out playing in the rain and after riding for about 4 1/2 to 5 hours in the rain I started getting a squeal from the Alternator Belt when starting out from a complete stop. Now that it is all dry it only squeals every 3rd or 4th time i start out.

I checked the belt and it seems to be just as tight as it ever was. The Trike is an '05 and has less than 4000 miles on it.

Should I replace the belt or just get used to the the squeal ??

Mark
 

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Adrian,

I may not be talking about the same disc you're referring to. If so I apologize. I bought this as an add on from one of the BH dealers through the internet. It is a flat disc with the hole in the middle machined to allow the pulley nut to be countersunk. It it about the same diameter as the entire alternator. I put it on in front of the pulley. Are we talking about the same disc?
 
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