Generator belt deflection

[sentra]

I am replacing the drive belts on my 1994 Nissan Quest. Although i seem to have gotten the correct tension on the belt by experimentation, i am having some difficulty understanding how it all happened. Can someone please provide some explanation? There must be other vehicles with a similar setup.

 

[Colt45ws]

What are you missing?

 

[sentra]

The longer, horizontal jack screw, also known as the adjusting screw, was more than half way screwed in, as you can see by the clear marks on the threads. Now, it's not, and that makes me think something might not be right. I realize that the new belt doesn't stretch as much, but there is still quite a bit of difference.

Also, when i was taking off the belt, i took out the long jack screw, but there was still tension on the belt. I had to remove the inner and outer generator to bracket bolt, which allowed the generator to swivel, and removed the belt.

When installing, just tightening the longer jack screw applied tension onto the belt and the generator won't swivel, even though inner and outer generator to bracket bolts were not screwed it.

I would like to know the purposes being served by the screws and bolts.

Old belt:

 

[Colt45ws]

Manufacturing differences and yes the belts do stretch a lot. Ive seen pictures of belts stretched about 2-3 inches.
As far as having to remove the alternator, they might not have left enough room for it to swivel to release the belt all the way. It may have been intentional so the belt will stay where it is supposed to be while you setup the adjustment.
The bolts are there to hold the alternator to the engine. Yes, the tension may hold it to the engine, but what if the belt breaks?

 

[The_Jeff]

Just FYI it's a good plan to loosen all the swivel bolts a little before going at the jack screw. Your tension was being held by the friction of those swivel bolts.

Also you want to check the tension in about a week as the belt beds in. Gatorback= good choice.

 

[mechtech2]

Stretched timing belts or serpentine belts? If they are puked internally, maybe.
Mostly I have seen wear that makes them loose - wear of the outside rubber.

 

[sentra]

Thank you for the responses, guys. I spent more time on it today, and i now know what's going on.

 

[mechanicx]

I see you say you figured it out. If I'm looking at this set up right, instead of just using a through bolt, they used an inner and outer bolt that are inline. So it does swivel on those two bolts if the bottom bolt in the adjuster is also loosened. Then the adjusting screw can move the alternator. The difference in the adjuster screw now being threaded out more (alternator inward) only looks like maybe 1/2 inch and about what you expect to see with a new and different belt vs the old.