Alternator shaft run out

[Rick]

G'day folks,

I just got a new Hella 100amp alternator for the TDI300 Defender. I spun the shaft and it looked a bit wobbly so I measured almost 10thou/inch run out on the outside of the pulley. Does that sound acceptable? The original is still in the truck and I'm not planning on swapping them until this weekend and I can't at the moment measure it.

Rick

[theelms66]

Mate. If you can see 10 thou runout your a better man than me.

[Blknight.aus]

that'll just be flange casting, check it on the rib faces and at the shaft.

if the shaft spins true, send it.

[Rick]

ttheelms, I reckon you could read a dial indicator, you're too hard on yourself [bigwhistle]


Thanks Dave,
I've measured in on the ribbed face with the wide foot on the indicator. I'm getting just over 8 thousandths with 2 different pulleys. It doesn't look good just spinning it slow but if it's of no consequence I'll put it in. I ran the indicator on the shaft where it smooth next to the frame and saw about 2 thou, out at the end of the shaft is just over 7 thou. So it seems the pulleys are pretty good but the shaft is wobbling a bit.

[Blknight.aus]

thats not too bad hows the deflection?

[Rick]

You got me there Dave, not sure what that is? Maybe the axial run out? That was just under the radial, maybe 6 or 7 thou on the edge of the pulley. It looks worse than it measures I guess.

[Blknight.aus]

deflection is how much you can move the shaft on the bearing.

[Old Farang]

What tempted you to check it in the first place? Not really telling you much with no load on the shaft from the belt. Mount it up with the belt on and then check it by turning the engine over slowly. Doubt very much if there is anything wrong with it.

[Rick]

Thanks Dave, I can't feel any deflection. Not really able to measure as the amount of thumb pressure I need to apply to the shaft starts moving my clamps holding the alternator to the bench. Doesn't seem to be an issue there.

Old Farang, I spun the pulley and I saw it wobble so I measured it. It's telling me the shaft is bent. I'm just asking if that much run out is problem or not. It doesn't look good and if it's an issue I'll have it replaced.

[POD]

I would not install it. It may be that the pulley bore is not concentric with the outer diameter, rather than the shaft bent. Either way I would send it back.

[Rick]

I put it in last weekend. Before I did I spun the old one after the belt was off. I couldn't see any wobble with it. I spoke with the supplier and they were happy to swap it out but I chose to put the new one in. Of course it wobbled a bit once installed but I've decided to go with it. I've got the old one to carry as a spare. I'll keep an eye on the newish belt to see if there is any obvious unusual wear.