AD 12 drive shaft wear

[neps989]

Working on a AD 12 7.5 hp. I noticed wear on the lower part of the drive shaft. I checked other drive shafts that I have and they have similar wear. What is the cause of this? I have a driveshaft with very little wear but don’t want to use it until I figure out what is causing the wear.
Thank you,
Rob
Sorry picture isn’t showing up. Wear is on lower end of drive shaft.

• This topic was modified 4 years, 3 months ago by neps989.

[frankr]

Are talking about toward the top of the flats area? Where it drives the double-D top end of the shock absorber? Well let’s not call it “normal”, let’s just say nearly all of them will show wear there. Maybe that makes it “normal”? Heck just use it unless it is really terrible.

[neps989]

Thank you.
That is the wear that I was concerned with. I had a nice picture attached showing the wear. The picture didn’t post for some reason. I didn’t get the error message saying it was too big.
I guess I will take your advice and use it.
Thanks again,
Rob

• This reply was modified 4 years, 3 months ago by Mumbles.

[frankr]

It’ll run till the wear extends all the way around, then it’ll be dead in the water I don’t think I’ve ever seen one completely fail for that reason, though I’m sure it is possible.

[fleetwin]

I’m trying to understand just what caused that wear pattern…Will have to look at a lower driveshaft sometime to understand….I’m guessing there is similar wear on the other side of the driveshaft as well….

[neps989]

You are correct, there is the same wear pattern on the other side of the driveshaft. I have other drive shafts and they all show the same wear pattern. I have one that has very little wear that I plan to use. I was hoping that someone could tell me what causes the wear. I did not remove the lower driveshaft to inspect it.

[frankr]

I thought I did explain it. The drive shaft goes into the double-D hole in the upper cap on the shock absorber. The upper cap is fairly thin at the top end–in fact as thin as the wear notches on the drive shaft. The drive shaft is fairly soft in comparison to the shock absorber, which is very hard. So, the shaft is exerting a rotating force in the shock absorber’s double-D hole and the softer shaft just gets beaten away, for lack of a better word. It would take a motor with very few hours on it to show no wear. The more hours, the more wear. I suppose a low oil level might contribute to it a bit, also.

[garry-in-michigan]

That is why Carl Keykaufer refused to use stainless steel drive shafts his Mercurys. We all know how well that worked.

[fleetwin]

Thanks Frank, makes sense now

[neps989]

I finally made it back to the shop armed with the information provided by frankr. I now understand what caused the wear pattern.
Thank you frankr for the explanation.
Rob

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