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spare alternator belt

prkaye

Well Known Member
A local builder put a spare alternator belt roughly in-place so that if his alternator belt fails while away, he can put the spare on without having to take the prop off.
I'm looking at my setup, and having trouble visualizing where I could place a spare alternator belt and not have it be in the way, and how I could secure it. Does anybody who has done this have a photo they could share?
 
Phil,
This is an old trick that some started many years ago. Generally it doesn't work very well.
One problem is that you now have an item that can cause trouble if it comes loose and becomes entangled in the prop hub.
The other problem is that deterioration of the belt is caused by heat and age as much as wear. Therefore, when the original belt fails, the "back-up" belt is not much better than the original.
These belts don't fail that often anyway. I've been flying my -6 for 16 years and have changed the belt once. Come to think, It's probably time to change it again.
Thanks for the reminder.
 
Phil,
I've been flying my -6 for 16 years and have changed the belt once. Come to think, It's probably time to change it again.
Thanks for the reminder.

I never thought I'd live to see the day that Mel needed reminding of anything. ;)
 
There's 2 way to tell when you're getting older...

I never thought I'd live to see the day that Mel needed reminding of anything. ;)
One is a loss of memory...
And I forget what the other one is.
 
OK thanks for that tip. That's what I was concerned about - the spare belt getting in the way, or getting tangled. I think I'll leave it out.
 
Carry a spare on trips and change it out on some regular schedule during your condition(al) inspection. :)
 
Phil,

These belts don't fail that often anyway. I've been flying my -6 for 16 years and have changed the belt once. Come to think, It's probably time to change it again.
Thanks for the reminder.

It's now been 17 years................. You need to think 17 years.........:D
 
...and yet another data point...

...on my -6A, using Van's 60A internally regulated alternator, and the recommended belt, I found that I could only install the belt if...I removed the ring gear, slipped on the belt, strrrrrrrtched the belt over the alternator pulley, and then reassembled. So, even if a spare belt was somehow placed behind the prop out of the way...I still would have to remove the prop and ring gear to get the new belt installed.

If I had used the next size longer belt, then the alternator pulley would have hit the lower fiberglass cowling, so that was not an option.

In the old days of typewriter repair (IBM Selectric), it was common for the field guys to install a second, spare motor-drive tooth belt inside the typewriter, loosely around the drive shaft clutch. This labor saving procedure was beneficial when the first belt wore out, and the spare belt could be slipped in place in just a few moments (the replacement of the first belt...the first time...was on the order of 30min). About halfway through the life production run of these typewriters, the belt material chemistry was changed and it was found that the life of these drive belts had lengthened to the point that if a spare belt was provided, it did not get used because service life environment made it no better that the belt that had worn out.

For me, it looks like installing a new, fresh belt is the way to go.
 
Carry a spare on trips and change it out on some regular schedule during your condition(al) inspection. :)

This made me laugh. To change the alternator belt, you have to pull the prop - not something that would normally be done on a condition inspection, and not something that one would typically undertake 'on the road' unless you really had to. Depending on where I am, I might be more likely to fly home without an alternator.
 
This made me laugh. To change the alternator belt, you have to pull the prop - not something that would normally be done on a condition inspection, and not something that one would typically undertake 'on the road' unless you really had to. Depending on where I am, I might be more likely to fly home without an alternator.

Or just use the backup alternator!:D
 
What about segmented belt

What about these? I carry one but have not had to use it.
 

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Yep, belt-driven alternators will most likely eventually have the same status as vacuum pumps......

Maybe. Many of us that fly a lot of IFR like having the redundancy of 2 alternators.

Or maybe having more lithium (or whatever battery tech is current at the time) battery capacity than fuel to complete a flight.

Just the natural progression of mechanical being replaced by non-mechanical. :)
 
Or maybe having more lithium (or whatever battery tech is current at the time) battery capacity than fuel to complete a flight.

Just the natural progression of mechanical being replaced by non-mechanical. :)

That’s a good option. Better, IMO, is having options to eliminate single points of failure. Maybe not much of a concern for VFR pilots but when I’m flying IFR in IMC I’ll take as many as I can get. And yes I understand the the biggest single point of failure is the engine, so I recognize there are limits as to risk mitigation and you have to be comfortable with the level of risk you are willing to assume. YMMV…..
 
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I need more amps than most - with both a full glass panel and electron-dependent engine. I have a larger than average battery on board (ETX 900) but I also have dual alternators. I need a lot of electrons, and I fly a lot of long cross-country in all kinds of weather, so I tend to pay close attention to that sort of thing.
 
Just get a section of link belt and make your own, when and if, you need it. And yes they do actually work. Quite well I might say.
I got stuck with a broken alt/water pump belt 30 years ago 23 miles from nearest town in the heat of summer. I walked the road till I found a chunk of rope that I finger spliced to make a belt and that got me to the nearest town.
YES I know it was a car. But, in 55 years of driving that is the only belt I believe I have had break.
Yes, I have two batteries and two alternators on my RV-6A, So, I don't have to worry about broken belts. I don't carry extra tires or tubes either.
My three cents worth Art
 
I’ve not tried a link belt on an aircraft. But it’s considered a great upgrade for a table saw. Smoother & less vibration. My saw’s had the same link belt since 2003 and shows no signs of wear. Runs at 3500rpm and much smoother than the traditional belt. Might be worth experimenting on an aircraft…
 
Belts and hoses should be replaced every 8 years, and you will never have a failure. I would much rather do that than have a spare belt that could come loose and get wrapped around something.
 
Installing a spare belt will guarantee it will never be needed.
If not, it will beak for sure.

That's the way things work. ;)
 
The alternator belt on my Mooney failed last fall on takeoff. Unfortunately, the reason it failed was that the drive pulley bearing in my alternator failed. I had plenty of time to get to my destination on battery (it was only a 20 minute flight). Would I have taken off with a known failed alternator? Probably not, but once in flight, I did some troubleshooting and deemed the risk was low for continuing the flight.

I asked my A&P about spare belts--he said, like Mel above, that spare belts mounted in place aren't a great idea because

1) It's generally not allowed in certified designs (pertinent in my case)
2) They spend a ton of time being exposed to heat, water, etc., that cause them to degrade in place
3) Alternator belts almost never fail on their own--in his experience, mine was the first he recalls failing in his 25-year career, and the root cause was the alternator failure anyway.
 
I am sure a link belt will work fine. Problem is that most 4 cyl installs only have about 1/4-1/2" of belt length range from hitting either the cowl or the block. Can't remember off hand, but thought that each link changed the belt length 5/8-3/4". Might need some luck to make it fit.

Larry
 
Those Link Belts

I’ve seen just a couple of belt failures in my 40-odd year career of fooling with little airplanes. I’ve seen a few spare belts wired and zip tied into place and I might have tied a couple in place myself. I think I remember one person actually using it. While it’s true that the spare gets thermal cycled the same as the active belt, it’s also true that it doesn’t get stretched during that time. If it gets you home then I figure it’s done it’s job. I hate the thought of changing a belt on an airplane when I’m out in the sticks, especially one with a constant speed airscrew. Especially if it’s a three blade prop because it’s so hard stretching the belt over that third blade. But. All that said, the McMaster-Carr link belts seem to work amazingly well. We have two RVs on the home drome with them and they’ve done fine. Admittedly, one failed (during a formation practice flight!) but an alternator failure came first. And of course, ya can’t use one on a type certified airplane. On the other hand, if a belt failed on my gummint approved spam can when out in the weeds, I would not hesitate to install one to get me home.
 
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