Alt arm turnbuckle hack PROBLEM

[Marco Flamingo]

In 2021, I posted about replacing my alternator adjustment arm with a stainless turnbuckle. Yesterday, while doing my morning ER check, I wiggled the V belt to check tension. The alternator wiggled. Looking closer, I saw that the turnbuckle shaft had "fractured" and separated. This is actually the second time I have had a stainless bolt used on the alternator shatter like that. The first time, the pivot bolt around which the alternator tension is set shattered. That caused the alternator needle to bounce around. While I was rumminating about that, I failed to notice the temp gauge (the warning buzzer didn't work). The resulting loose V belt meant the water pump wasn't working, which meant overheat, which meant engine failure, which meant pulling the engine out, which meant pulling my wallet out.

After getting back in the water, I replaced the SS pivot bolt with steel. It might corrode more over time, but I figured it was less likely to shatter. Now, the same thing has happened with my SS adjustment turnbuckle. In this case, the alternator was no longer tensioned properly, but was apparently still generating a tach signal and providing enough raw water. Kind of a fluke that I saw it. Just thought I'd post because others have done this hack. Worked great until it didn't. Fortunately, I had the original arm in my spares box, as we are in the boonies (anchored in Cameron Cove on Princess Royal Island).

 

[luna]

There is a reason that most bolts that attach the cling ons to a diesel's engine block are Grade 8 steel.
They rattle.

Leave the stainless off of the engine. Use paint and a dry E.R. to control corrosion.

Good catch, that apparently prevented an overheat.

 

[Mac2]

Have you located grade 8 eye bolts or turnbuckle? I like that hack for tensioning.

 

[Marco Flamingo]

Looks like Home Depot. Might have to buy 2 if you want eye-and-eye. Should get a couple of nuts to lock it. Not sure I'll go that way. The arm worked for 10,000 hours and isn't that inconvenient to set tension.

Everbilt 5/16 in. x 9-3/8 in. Zinc-Plated Turnbuckle Hook/Eye 807096 - The Home Depot

Crown Bolt - Zinc Plated 5/16 in. x 9-3/8 in. Turnbuckle Hook/Eye - 5/16 in. thread Diameter. 9-3/8 in. open measurement. 6-1/2 in. closed measurement. Hook and eye turnbuckle. 2-7/8 in. take up measurement.

www.homedepot.com

 

[Diep]

That zinc plated turnbuckle is probably cast.

It will run you closer to $30 but you can get forged or forged and galvanized from an industrial supply-type place.

 

[O C Diver]

I'm curious what size the bolt was?

When adding the second alternator to the John Deere, all hardware was stainless steel including the brackets. The all-thread in the below picture is 1/2".

I did learn maybe 25 years ago, that welding SS all-thread changed something in the structure of the metal, causing it to break. Hence the small piece of SS angle for the bracket.

Ted

 

[luna]

Have you located grade 8 eye bolts or turnbuckle? I like that hack for tensioning.

Nope, although I never looked.

Looks like Home Depot. Might have to buy 2 if you want eye-and-eye. Should get a couple of nuts to lock it. Not sure I'll go that way. The arm worked for 10,000 hours and isn't that inconvenient to set tension.

Everbilt 5/16 in. x 9-3/8 in. Zinc-Plated Turnbuckle Hook/Eye 807096 - The Home Depot

Crown Bolt - Zinc Plated 5/16 in. x 9-3/8 in. Turnbuckle Hook/Eye - 5/16 in. thread Diameter. 9-3/8 in. open measurement. 6-1/2 in. closed measurement. Hook and eye turnbuckle. 2-7/8 in. take up measurement.

www.homedepot.com

If you bought 2 with the intent on making an eye bolt at each end wouldn't the end that had the hook in it originally have the opposite hand thread?

Good choice in using the original arm. With 10,000 hours on it, it is likely just broken in.

 

[ABfish]

You're tensioning the alternator belt, but it appears you're loading the turnbuckle in compression. Turnbuckles are generally used in tension loading only.

Compression load rating would be a fraction of the tension rating. And as others have mentioned, stainless is not the best material for this use.

 

[Bmarler]

Agree with that, the turnbuckle wouldn’t be my first choice. I’d use something like this: https://www.summitracing.com/parts/...5b7oN4yHzvwTHWJ0mN9CvyaqBT3JZZyhoCSS8QAvD_BwE
Available in almost any material you want, as well as any size. That one is just an example so you can get the idea.

 

[Marco Flamingo]

I'm curious what size the bolt was?

The turnbuckle was an M8 because that's what fit. It had the right size eye for the block and alt bolts. The pivot bolt was M10 because that's what Balmar has on their "larger" pivot bolt for my alt (they have the same 100A alt available with an M8 pivot bolt. But I doubt that Balmar specs stainless. That was probably the PO.

There really isn't that much compression load on the turnbuckle. Only enough so that the belt doesn't slip. The issue seems to be stainless bolts handling vibration. They don't in my experience (0 for 2).