Fan belt

jpowell13 · #1 10-19-2016, 09:54 AM

I was making an IFR departure out of Gatlinburg-Pidgeon Forge last month, ran into a little rain and noticed my battery was discharging at about -10 amps. I was able to cancel IFR and make it to Jackson TN on the big 35amp-hour battery in my 6A.

I pulled the cowl and got an A&P to look at it. Of course, it charged fine on the ground. The A&P thought it must have been the connector at the back of the Plane Power alternator and that we fixed it when checking for a loose connection.

I pulled the battery, charged it fully and headed back to Baton Rouge. Once again, the battery started discharging in the air. I turned off all the non-essential stuff and was able to make it home with enough juice in the battery to power the transponder and radio for my arrival into Class C BTR.

The problem seems to be that my 2 and a half year old fanbelt is worn and bottoming out on the flywheel pully. I've never heard any squealing and tightening the belt only works until shortly after takeoff.

I'm sure the "old hands" would have known what to do right away, but I was fooled briefly. Looks like 2 years is about all you get on those belts.

John

BobTurner · #2 10-19-2016, 10:04 AM

Quote:

Originally Posted by jpowell13

but I was fooled briefly. Looks like 2 years is about all you get on those belts.

John

They should last a lot longer than that. Perhaps you have an alignment issue?

gasman · #3 10-19-2016, 10:36 AM

Rain on a under sized (too narrow) belt can slip. Did the belt come from PP?

jpowell13 · #4 10-19-2016, 10:43 AM

I'll take a look at that Bob. I would have thought they should last longer. My engine is an old narrow deck that was designed to use one of those monstrous generators on it back in the day. Would that make any difference? John

jpowell13 · #5 10-19-2016, 10:52 AM

The belt is a Gates 7300 XL (11A0760). It stands proud on the PP alternator pully but the PP tech said that's OK. I'll check with PP to make sure the belt is correct.

skylor · #6 10-19-2016, 11:20 AM

Quote:

Originally Posted by jpowell13

I was making an IFR departure out of Gatlinburg-Pidgeon Forge last month, ran into a little rain and noticed my battery was discharging at about -10 amps. I was able to cancel IFR and make it to Jackson TN on the big 35amp-hour battery in my 6A.

I pulled the cowl and got an A&P to look at it. Of course, it charged fine on the ground. The A&P thought it must have been the connector at the back of the Plane Power alternator and that we fixed it when checking for a loose connection.

I pulled the battery, charged it fully and headed back to Baton Rouge. Once again, the battery started discharging in the air. I turned off all the non-essential stuff and was able to make it home with enough juice in the battery to power the transponder and radio for my arrival into Class C BTR.

The problem seems to be that my 2 and a half year old fanbelt is worn and bottoming out on the flywheel pully. I've never heard any squealing and tightening the belt only works until shortly after takeoff.

I'm sure the "old hands" would have known what to do right away, but I was fooled briefly. Looks like 2 years is about all you get on those belts.

John

I had a plane power failure where the alternator dropped off-line and stopped charging during takeoff. Resetting it (pulling and resetting the field breaker) in the air didn't help, but on the ground it reset. I tried a second takeoff and and quit charging again on the takeoff roll (as soon as the engine reached full RPM).

It turned out that the rear bearing in the alternator had spun within the housing and the housing bore wore to the point where the slop was allowing the armature to rub against the stator. I think at full RPM the situation was bad enough to trip the alternator off-line (bouncing the brushes, perhaps).

You may want to loosen your belt and carefully check the alternator pulley for slop and play. Your failure sounds similar to mine.

Skylor

9GT · #7 10-19-2016, 11:54 AM

From my experience: Pull $PP alternator, throw in garbage can. Replace with $$$ B&C alternator with external regulator. You will never question that decision. Having been stranded away from home with a bad cheap alternator with only 70 hours on it, I never wanted to go through that again.

jpowell13 · #8 10-19-2016, 11:56 AM

Thanks Skylor. I'll check the bearings when I change the belt and let you know what I find. I think the Gates belt is right after talking with PP. I think I'll go with a gear driven unit when this one wears out. (Or may go ahead and change over now David.)

I may be drifting here, but the best answer may be to add one of those B&C sd8 backup alternators on the vacuum pump pad and change my heavy battery for an Earth X. Then, I would never get stranded by a bad fan belt or alternator and would loose 15lbs to boot. This would lighten the wallet somewhat also.

jpowell13 · #9 10-31-2016, 06:52 PM

So, I pulled the prop and removed the alternator belt. It looked almost pristine. The alternator spun smoothly with no play in the shaft. Turns out the crimp in the ring terminal on the battery lead was loose at the alternator. I failed to notice the loose terminal until I got the alternator fully exposed. The loose crimp explains everything. Now I have a new belt and a working alternator. Thanks to all for your help. John