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Alternator belt measurement advise

J

jeff beckley

Well Known Member
I need to move my generator back away from the cowling. Also modify the adjustment arm.
That means a different belt is needed.
How do I calculate the size?
 
Old school here....after you have the alternator repositioned, grab your wife's cloth tape measure from her sewing kit. Wrap it around the pulleys, pull tight and read the length (use a metal tape if you don't have the other). Google alternator belt with the width and length you need. If you have a number on the old belt just use that number and find one the next size shorter. I just changed the belt on my IO360 with the large pulley from a 15365 (36.5"long) to a 15360 (36" long) to give me some cowl clearance.
 
RV7 To Go said:
Old school here....after you have the alternator repositioned, grab your wife's cloth tape measure from her sewing kit. Wrap it around the pulleys, pull tight and read the length (use a metal tape if you don't have the other). Google alternator belt with the width and length you need. If you have a number on the old belt just use that number and find one the next size shorter. I just changed the belt on my IO360 with the large pulley from a 15365 (36.5"long) to a 15360 (36" long) to give me some cowl clearance.
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I git the jist. But to be sure, when wrapping the cloth tape , do I do it around the top flang or try to get it nested deep in the valley?
I have never known where the measure belts.
Top wide side or around the inner short groves
 
Around the outside, with a cloth tape, as others have said. I then took the cloth tape to the store and measured the belts to find one with a matching circumference. And also bought the next size up, to be returned later.
 
Or, take your old belt - which you don’t need anymore - and cut it and use to measure the gap between pulleys. Take that belt and info to Napa and they should be able to give you the right length belt. They used to have a tool to measure belts and may still.
 
I got the old belt out. I really need the next size smaller. I tried to look it up. Couldn't find a chart.
 

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jeff beckley said:
I got the old belt out. I really need the next size smaller. I tried to look it up. Couldn't find a chart.
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If it's two sizes smaller based on what was said here they go by 1/2 inch I won't be able to get the belt around the ring gear and generator.
I half to drill a new hole in the arm to move it back. It rubs a hoke in my lower cowle. The Phillips screw on the generator also hits.
To shorten I have to drill a hole on the end and cut off the old one.
 

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PaulvS said:
The belt in the photo is 11A0925 i.e. 11mm wide and 925mm long. The next size down is 11A0915.
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I recently went through trying to find a shorter belt. Never found one that was not a LOT shorter, which would not have worked. Stayed with my original replacement belt of the same size as the one I took off and it seems to be working. Wondering what I will do when the belt starts to loosen up..... Good luck!!
 
In my somewhat odd installation (o-320-h2ad) I found there is exactly ONE belt size that can be gotten onto the pulleys and can be tightened.
I originally thought I could use a stock Cessna alternator but found it doesn't clear the cowling.
Good luck!
 
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