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When to replace alternator belt

crabandy

Well Known Member
What's the average lifespan of the alternator belt on a Lycoming?

I'm doing my condition inspection and initially the belt looks good, but as I turn the prop and watch the belt stretch over the smaller alt pulley small cracks become visible.

9 years flying and 600 hours on the stock belt.
 
How painful will it be if the belt breaks away from home? I have one of those link belts in my travel bag just in case. I'd probably only change the belt when you pull the prop for maintenance, but I'm day VFR. Guys with much more experience will hopefully chime in and give you better advice.
 
Definitely time to change it, I think 4-5 yrs is the recommended time change or if it shows distress like cracks.
 
Definitely time to change it, I think 4-5 yrs is the recommended time change or if it shows distress like cracks.

Thanks Walt, did not realise it was such a short cycle as mine is 13 years old and still looks OK. How easy is it to change, do you have to remove the flywheel/ring gear? also what part/brand would you recommend for the replacement?
Thanks
Figs
 
Link Belt

Hey Mickey, Never heard of a link belt. Great Idea to get you home vfr. Which one did you get? Anybody else carry one of these for an emergency?
 
Thanks Walt, did not realise it was such a short cycle as mine is 13 years old and still looks OK. How easy is it to change, do you have to remove the flywheel/ring gear? also what part/brand would you recommend for the replacement?
Thanks
Figs

Anytime I pull the prop I replace the belt. My prop has a recommended 5 year overhaul so at the very minimum, I replace the belt every 5 years. If I pull the prop for some reason before the 5-year period I replace the belt. I have 2 extra belts that look just fine but belts are cheap compared to a break-down away from home.

-Marc
 
I'm not advocating anything, just providing a datapoint. The belt on my RV-6 is 23 years old and still looks fine. It is a drive belt used on commercial lawn equipment purchased from a local dealer. The fixed-pitch prop hasn't been off the engine in 22 years so there hasn't been a convenient time to replace the belt. I only fly day VFR so am not as electrically dependent as some pilots.
 
Is the belt aviation specific or is it just a part number that can be sourced from NAPA ?

Belts are easily sourced from NAPA. They need to be the proper length for your particular installation, best to take the old belt in the first time to get a proper match. Note how much range of adjustment you have in the alternator position before removing the belt. For instance, if you see that the current belt puts you towards the end of the adjustment range to tighten the belt, consider downsizing the length just slightly.
 
Most folks use the Gates 7355/7360 belts.
One reason I will no longer do RV6 condition inspections is their general lack of good maintenance practices/programs.
 
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It's the belt, not the delivery path.

Belts are easily sourced from NAPA. They need to be the proper length for your particular installation, best to take the old belt in the first time to get a proper match. Note how much range of adjustment you have in the alternator position before removing the belt. For instance, if you see that the current belt puts you towards the end of the adjustment range to tighten the belt, consider downsizing the length just slightly.

It is more brand and specific model of the belt, not delivery path.

I ran the gates alternator belt on my Volvo for 160,000 miles. Many examples like this and never failed a raw edge Gates belt.

If however, if one can bend the belt backwards (arc like the small pulley) and see cracks go (or close) to the reinforcement, then it is wise to replace.
 
FWIW, tribal knowledge has long held Gates as the best quality, readily available belts. Would like to know if most still feel that way. I do know that a lot of aircraft OEMs were using them and relabeling them. Then you had to buy a > $120 belt from them because that PN was the only thing approved under the TC. Probably a few hundred $for one today. Makes you miss certified world don't it! Another FWIW data point, B&C utilize Gates in their kits. Knowing B&Cs rep for quality says a lot, to me at least.

Rockauto sells to individuals the same prices as resellers. They have a pretty huge selection of most anything including drive belts.

Constructive thread. It didn't veer off by someone stating their selection was best by getting a back-up gen thus not having a SPF in an alt belt, etc. That said, if you don't have a back-up source for wattage, a link belt will pay for itself a hundred times over if it's ever needed.
 
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Walt, please elaborate on what sets the -6 owners and maintainers apart from those of other other RV’s that would make you avoid them? Not questioning your decision; I’m genuinely curious as most of the roughest RV’s I’ve seen have been 6’s.
Edit: Apologies the OP, I hope this doesn’t cause a big thread drift.

Back to the discussion: I’ve heard of people securing a spare belt behind the big pulley.
-experiences with that? Pix?
 
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Back to the discussion: I’ve heard of people securing a spare belt behind the big pulley.
-experiences with that? Pix?

That has been discussed here many times. Two problems with it on RV’s:
1) The design of RV forward baffles make it almost impossible to do.
2) The spare belt sees as much heat as the primary one over its lifetime, and is generally pretty badly degraded by the time you might need it….

In terms of belt life, I replace them “on condition”, since I have never seen anywhere that documents a life limit - I’d be curious if Walt has a reference to one that I have missed. To me, “On condition” means if I see cracking, its time for a new belt. I have always gone a good ten years or so - but this will vary on the type of environment in which you live and operate, and the brand belt that you use. I always try and get Gates because I know the name.

Paul
 
I have an SD8 for backup, but I’ll also have dual crank sensors for EI and the thought of a half broke belt flailing around is a little spooky.

It struck me that the RV isn’t new anymore…………9 years and 600+ hours have been good to me. So far anything I’ve replaced has failed Prematurely, time to start inspecting wear items a little better.
 
Careful!!!

Anecdotal report from local DPE had local student report this answer during Q&A session of a check ride:

DPE: "What would happen if your alternator belt broke?"

Student: "The propeller would stop"
 
In terms of belt life, I replace them “on condition”, since I have never seen anywhere that documents a life limit - I’d be curious if Walt has a reference to one that I have missed. To me, “On condition” means if I see cracking, its time for a new belt. I have always gone a good ten years or so - but this will vary on the type of environment in which you live and operate, and the brand belt that you use. I always try and get Gates because I know the name.

Paul
No hard fast rules, some folks recommend 36,000 miles while other say 60,000 miles for automotive V belts. In years that probably equates to 5-6 years. Belts also wear out so checking wear compared to a new one is also something to consider but not easily accomplished. So even if the belt is not showing outward signs of cracking, they are still considered wear items and should be replaced on a regular basis, just like you would on your car.

The Car Care Council says chances of a V-belt failure rise dramatically after four years or 36,000 miles, while the critical point for a serpentine belt is 50,000 miles. Any belt should be changed when it shows signs of excessive wear. But many new composite belts don’t show signs of wear until the failure occurs.

More info from Gates (even though the ref is for serpintine belts the same guidelines are applicable:

https://www.gates.com/content/dam/gates/home/knowledge-center/resource-library/tech-tips-bulletins/tt002-15.pdf
 
Walt, please elaborate on what sets the -6 owners and maintainers apart from those of other other RV’s that would make you avoid them? Not questioning your decision; I’m genuinely curious as most of the roughest RV’s I’ve seen have been 6’s.

Maybe it has something to do with the age of the 6 fleet, but many are purchased because they are available for a lower price point and owners tend to treat them like a 172. Owners aren’t really interested in fixing them up or taking good care of them it seems. And most mechanics don’t really want to mess with them either so they get neglected there as well. I don’t work on certified aircraft anymore do to the same mentality.

That’s not to say there aren’t some outstanding examples of the 6’s out there, those owners that love their machines and take excellent care of them, but they aren’t the ones that show up at my shop for work.

My goal is to help make nice RV’s better, for owners that understand that mechanical things require lots of TLC and have souls, and it pays to respect that bond :D
 
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Ignoring maintenance because it’s to much work? not a great plan in my book

I am not suggesting to ignore maintenance, just pointed out that it is not just the cost.
Also, I am of a belief that a bit of common sense goes a long way. An aircraft that flies 50 hours a year and to change the belt every 5 years (250 hours of life) without inspecting it to check its condition would be the same as throwing away vinegar just because of it reached the expiration date.
 
I am not suggesting to ignore maintenance, just pointed out that it is not just the cost.
Also, I am of a belief that a bit of common sense goes a long way. An aircraft that flies 50 hours a year and to change the belt every 5 years (250 hours of life) without inspecting it to check its condition would be the same as throwing away vinegar just because of it reached the expiration date.

Wow that's a giant leap! Guess you shouldn't change the oil if it still looks good even though it's been a year since the last change.....

-Marc
 
Wow that's a giant leap! Guess you shouldn't change the oil if it still looks good even though it's been a year since the last change.....

-Marc

If it test good, yes I would not change it. However, engine oil has a calendar year interval which is based on test result and gases that gets injected to it. But if I change the oil and don't run the engine in one year, I probably wouldn't change it.
Another scenario would be if I ran the engine enough hours in 4 months but not enough that oil needs changing, lets say 25 hours, I may extend that 4 month calendar a bit longer. For me, it is all common sense driven and based on test results, much like the vinegar example.
 
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No hard fast rules, some folks recommend 36,000 miles while other say 60,000 miles for automotive V belts. In years that probably equates to 5-6 years. Belts also wear out so checking wear compared to a new one is also something to consider but not easily accomplished. So even if the belt is not showing outward signs of cracking, they are still considered wear items and should be replaced on a regular basis, just like you would on your car.

The Car Care Council says chances of a V-belt failure rise dramatically after four years or 36,000 miles, while the critical point for a serpentine belt is 50,000 miles. Any belt should be changed when it shows signs of excessive wear. But many new composite belts don’t show signs of wear until the failure occurs.

I am guessing belt life is a function of heat (including heat cycles), belt tension, belt quality (brand, material, manufactured on Friday or Monday), belt load, belt cycles of changing RPM, plus several others. I don’t have any data on how a Lycoming in an RV relates to auto in any of these variables. Just doing simple math shows that in a car at average speed of 60 mph means 36,000 to 60,000 miles is 600 to 1000 hours of use. Auto has lots of RPM changes that causes stress and slippages that airplanes don’t experience to any where the same degree. All said my conclusion is airplanes maybe “easier” on belts than autos but I could easily change my mind with further data. (See my Mark Twain quote below)

I base my belt replacement on condition and every time I have the prop off, which is not too often since I have a fixed pitch metal prop. I just put on my third belt in my 1000 hours of flying so averaging about 400-500 hours.
 
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And Besides

I’m just glad our RV-6 has a two blade propeller. Stretching the belt over that third blade on some airplanes is a real bear. Seriously, during 100 hour, periodic condition inspections, or whenever else the cowl is off, I take a good look at the belt for delams, cracking and tension. I don’t recall ever changing one because it looked bad. But yeah, me too on changing whenever the prop is off. I’ve seen very, very few failures in my many years fooling with little airplanes. One of my formation buddies just had a failure of a linked belt after very few hours, so there’s that. I’ve wired a few to the engine as spares and yes of course it gets thermal cycled, but not stretched and bent while the working belt is place. The backup just has the get the airplane home or at least to where a new belt can be installed. That said, I don’t recall hearing of a time when that spare was actually used to bail someone out of a sticky situation. I considered adding one to our airplane, but as previously reported, the baffling pretty much ruled that out.
 
The Car Care Council says chances of a V-belt failure rise dramatically after four years or 36,000 miles, while the critical point for a serpentine belt is 50,000 miles.

2014 vehicle, 187,000 miles and the serpentine belt was just ok'd by the technician.

Funny thing about those recommendations from those organizations...they seem designed to generate more income for their real clients, don't they?

E.g., car uses 0W20 fully synthetic oil. Recommendation is change every 7500 miles (or half as often as they used to with non-synth oil, but it costs twice as much). Thanks to sending samples to Blackstone and slowly extending the intervals, we're now at changing every 20,000 miles or so *with no change whatsoever in the oil analysis results*.

What's the worst thing that could happen if your belt broke in flight? You *do* have backup batteries (or alternator) for flight-critical items, right?

And putting on a linked belt once on the ground, even if just to get home, seems like a decent option vs. pulling the prop when it's not necessary.
 
Alternator belt change times.....

In terms of belt life, I replace them “on condition”, since I have never seen anywhere that documents a life limit - I’d be curious if Walt has a reference to one that I have missed. To me, “On condition” means if I see cracking, its time for a new belt. I have always gone a good ten years or so - but this will vary on the type of environment in which you live and operate, and the brand belt that you use. I always try and get Gates because I know the name.
Paul

I recently was doing some major work FWF including replacing all timed-out hoses and a reconditioned harmonic balancer. I thought since I had the prop off and balancer off, I'd replace the belt. Why not? Less than $10, as I remember. After 1012 hours and 25 years, I figured it was about time. It is a little bit of a PITA but I now have a new belt to go with other new things!

The old belt looked BRAND NEW!! There is NO evidence of wear, cracking, abrasion......nothing. I'll probably carry it as a spare.

Belt: Gates 7370 XL from National Aviation Parts Association (NAPA).
 
I recently was doing some major work FWF including replacing all timed-out hoses and a reconditioned harmonic balancer. I thought since I had the prop off and balancer off, I'd replace the belt. Why not? Less than $10, as I remember. After 1012 hours and 25 years, I figured it was about time. It is a little bit of a PITA but I now have a new belt to go with other new things!

The old belt looked BRAND NEW!! There is NO evidence of wear, cracking, abrasion......nothing. I'll probably carry it as a spare.

This has been my experience as well (23 years on a Gates industrial belt). The belt is checked every time the cowl is off but never seen any evidence of deterioration. If/when the FP prop is removed the belt will be replaced but the prop isn't coming off just to replace a belt that appears to be in excellent condition.
 
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I’m just glad our RV-6 has a two blade propeller. Stretching the belt over that third blade on some airplanes is a real bear.
It should be easier, as a 3-bladed prop will usually be a smaller diameter than an "equivalent" 2-bladed prop.
 
Bough the Gates 7355 XL belt and installed it, it was slightly big and used almost all of the adjustment for the alternator belt tension.
I removed everything a second time and installed a Gates 7350 XL that was the perfect size.
 

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To Walt's point, the 6 is the oldest and least expensive of the side-by-side models. In general, those that buy a 6 these days are looking for a deal and then often skip a proper pre-buy and try to spend the bare minimum on maintenance. I have walked away from a few RVs, either they were so bad I didn't want to be associated with them or they needed a lot of TLC and the owner did not want to spend the $ to address those items. I have also seen some 7/9s I wouldn't touch as well, but since they generally cost more to purchase, the owners are better funded.

I am a 6 builder/owner myself, so don't think I have a bias against the older models. Just the reality of an aging fleet. I have seen worse in the even less costly world of Sonex and similar, so it is not Vans-specific issue.

Maybe it has something to do with the age of the 6 fleet, but many are purchased because they are available for a lower price point and owners tend to treat them like a 172. Owners aren’t really interested in fixing them up or taking good care of them it seems. And most mechanics don’t really want to mess with them either so they get neglected there as well. I don’t work on certified aircraft anymore do to the same mentality.

That’s not to say there aren’t some outstanding examples of the 6’s out there, those owners that love their machines and take excellent care of them, but they aren’t the ones that show up at my shop for work.

My goal is to help make nice RV’s better, for owners that understand that mechanical things require lots of TLC and have souls, and it pays to respect that bond :D
 
Just the reality of an aging fleet

And, lest we forget, the most numerous by far :)

As far as mine is concerned, the belt is 17 years / 1'400hrs old, and will be replaced, a major PIA with a 3 bladed CSP, upon taking the prop off either this Winter or the next...
 
I get the feeling from this thread that some folks take better care of their cars than they do their aircraft.
Maybe we could reduce the mechanical accident rate if we took maintenance a little more seriously?
I find it distressing that this attitude is so prevalent (it’s a PIA so I just won’t do it).
(We spent thousands of man hours taking care of aircraft that weren’t broke in the airlines, and their safety record is proof of the concept of “preventive” maintenance).
Maybe a “refresher” from the chart below on accident rate from mechanical problems will get your attention?
Notice how EAB is worse than the control group in all of the mechanical categories.

accidents_03-1.jpg

Chart courtesy of KitPlanes.
 
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Walt, your opinion has been stated. If I was doing work on airplanes for pay I might also be more vocal about "neglected" maintenance.

But my RV-6 isn't going to fall out of the sky if the alternator belt fails. However, there are flight critical aspects of maintenance and I give those areas fanatical attention. I feel my RV-6 is very well maintained in spite of the broad brush with which you seem determined to paint.

Not everyone shares my opinion and I'm fine with that. No need for you to feel offended if not everyone shares your opinion. We all want safe aircraft. :)
 
+1 on your post Sam!

my RV-6 isn't going to fall out of the sky if the alternator belt fails. However, there are flight critical aspects of maintenance and I give those areas fanatical attention

... and my very thoughts as well :)
 
Can you tell which one is new?
Just removed belt for replacement which was new in 2013, less than 500hrs. RV7
Also showed signs of distress on the sides and significant wear to cogs (?).
New one is quite stiff, old one feels more like a noodle.
Both are Gates 73xx

i-LW72T53-X2.jpg
 
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Just curious. How many have had a properly aligned and tensioned belt, that’s only pulling an alternator, and not oil soaked, actually break?
 
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