How Loose is Your Alternator

[A64Pilot]

Noticed today doing the annual when I pushed on the Alt belt the Alt moved slightly, I thought this odd, Where it’s getting the movement is from the two pivot bolts being loose, now they are cotter pinned so obviously they were intentionally installed loose obviously to allow the alt to rotate freely for tightening the belt.

Is this normal for a Mooney? I don’t see it as a safety issue, just seems odd is all. 

[takair]

I don’t think this is normal.  It could lead to fretting and hole elongation and more looseness.  Alternator mounting is frustrating, the housings are rather inconsistent and they are different from manufacturer or manufacturer.  As you said, that is the pivot, so must be loose for adjustment, but from my experience must be tightened once set.  At a minimum, keep an aye on it to see if it’s “making metal”….  

[Hank]

 My alternator is tight. I check belt tension on preflight, the belt has some give, the alternator does not move.

[N201MKTurbo]

I usually install the pivot bolts loose, then tighten the belt, then tighten the pivot bolts. The alternator should be tight. If the pivot bolts are loose, it will wear the pivot bolts and bushings rapidly.

[A64Pilot]

We tightened it, that removed the looseness, that was there from wear from being loose, and that returned the belt to correct tension, so being loose obviously caused wear.

What had me confused was as there were cotter pins, it was intentionally installed loose, and as that ran against my experience I thought I’d ask.

Now onto the other thing that has been annoying me, that is the engine controls bottom out, there should be some “cushion” that is stops on the engine should hit leaving some travel on the cable.

Edited December 26, 2024 by A64Pilot

[N201MKTurbo]

It is a mixed bag. If you are the only one flying the plane and you know how the controls are rigged and feel, I agree a bit of cushion is the best way. That way you get the full throw out of device you are controlling.

On the flip side, I used to rig my prop control with some cushion. Every time my ex partner flew the plane, he would push the prop control all the way in. Once he actually told me how hard it was to get full RPM. He was pushing so hard that he was pushing the cable swivel at the end apart. I told him repeatedly to just gently push the control in till it stops. He never got it, he always pushed it to the stop. So I had to rig it with no cushion.

[takair]

4 hours ago, N201MKTurbo said:

It is a mixed bag. If you are the only one flying the plane and you know how the controls are rigged and feel, I agree a bit of cushion is the best way. That way you get the full throw out of device you are controlling.

On the flip side, I used to rig my prop control with some cushion. Every time my ex partner flew the plane, he would push the prop control all the way in. Once he actually told me how hard it was to get full RPM. He was pushing so hard that he was pushing the cable swivel at the end apart. I told him repeatedly to just gently push the control in till it stops. He never got it, he always pushed it to the stop. So I had to rig it with no cushion.

I see people go so far as to use the vernier to eliminate the gap on the prop….

[PT20J]

Some previous owner probably read on some internet forum that the alternator should be loose. 

[MB65E]

Check the alternator bracket/Arm. I’ve seen them paper thin due to ware. It’s behind the baffeling and untouched by many. 
-Matt

[A64Pilot]

On 12/26/2024 at 7:57 PM, PT20J said:

Some previous owner probably read on some internet forum that the alternator should be loose. 

No, I know the IA who cared for it, the owner never touched it, that’s what had me wondering if for some silly reason Mooney wrote it to be kept loose, just thought I’d ask before I tightened it.

[A64Pilot]

22 hours ago, MB65E said:

Check the alternator bracket/Arm. I’ve seen them paper thin due to ware. It’s behind the baffeling and untouched by many. 
-Matt

It appears to be fine, one end of it is held by one of the bolts that was loose though, but it didn’t seem bad. Engine has about 600 since overhaul and all accessories were replaced in overhaul.

[A64Pilot]

Ref no slop in controls, I’ve seen as the engine develops power the mounts being rubber allow a little movement, and that pulls the control slightly off of the stops

[PT20J]

1 hour ago, A64Pilot said:

On 12/26/2024 at 4:57 PM, PT20J said:

Some previous owner probably read on some internet forum that the alternator should be loose. 

No, I know the IA who cared for it, the owner never touched it, that’s what had me wondering if for some silly reason Mooney wrote it to be kept loose, just thought I’d ask before I tightened it.

It was a joke