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Old 07-12-2021, 08:37   #1
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A learning opportunity

I recently tore off the alternator ground post of my new balmar alternator at 13ft/lbs of force (see attached). Initially I thought what the hell, but I think there is a lesson to be had here for future boat work

First off I am not a fan of mechanical stuff, I’d be much more comfortable diagnosing issues from a computer.
But I am hardly a rookie in this area. I’ve all but rebuilt an e46 S54 motor, doing everything from the timing chain tensioner guide to the rod bearings and quite a few things in between. If anyone is familiar with the car, you know how mechanically complex the motor is.
However, with that car everything is spelled out for you; tightening torque, tightening angle, everything. Having taught myself how to work on cars from this motor, I expected everything to be the same.

It has pretty quickly become apparent to me that there is quite a bit more “grey” area when working on the boat. There seems to be quite a bit more leeway on the installs; a lot more “make sure it’s tight” rather than “tighten to 30ft/lbs and then 90 degrees”. If that’s more a result of working on German cars than cars in general I don’t know.

So my question is, how do people approach working on their boats? Is “snug it down” the rule of thumb? I am fine with 99% of the improvisation work, but that last 1% left unspecified has consistently made me uncomfortable.

To drive home how neurotic I am here, I had purchased a laser alignment tool to make sure the belt was inch perfect and had disconnected the alternator to move it. My belt is now perfectly aligned but now the alternator needs some work 🙃
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Old 08-12-2021, 06:45   #2
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Re: A learning opportunity

Hmmmm. Really good question, Notyetsinking. I'm your opposite, much more at home with steel than with computers. First note: Don't count on the manufacturers of electrical equipment to use high quality bolts. That $200 Balmar alternator uses bolts you could find in little packets in a grocery store.

My practice is to pay careful attention to my torque wrench when doing engine repairs that are dependent on proper torque, such as the head gasket. Beyond that, I think that I have developed a feel for bolts, and pay attention to whether this is an ordinary common steel cut-thread hold-it-together bolt or a hardened rolled Grade 8. They feel different, for starters. Soft bolts stretch, and you can feel that in torquing them. I also pay attention to diameter, and avoid using a wrench that might twist off a small bolt - little bolts need little wrenches. Really little bolts need nut drivers.

I suspect that as you keep doing boat repairs you will develop this feel for hardware. Right now, the penalty for not having that feel is figuring out how to drill out and rethread the bolt in the Balmar.

A fun extercise might be to take a handful of various bolts, clamp them very tightly in your vise, and twist them off using various wrenches.
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Old 08-12-2021, 12:10   #3
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Re: A learning opportunity

I really like tkeithlu's answer.

One time, from not knowing what he has written, I broke off two small studs, on the rails the car seat was bolted to. You are not alone. With familiarity, and small wrenches for small nuts and bolts, and attentiveness, you're brain WILL just "get it." Trying the exercise he suggests may accelerate the process for you.

Sorry about your alternator bolt.

Ann
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Old 08-12-2021, 19:56   #4
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Re: A learning opportunity

An old timer taught me to "feel out" a proper torque for bolts, using two, three or four fingers to turn your wrench, instead of purely arm strength. had good luck with that philosophy for thousands of questionable nuts & bolts
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Old 08-12-2021, 23:27   #5
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Re: A learning opportunity

Quote:
Originally Posted by tkeithlu View Post
Hmmmm. Really good question, Notyetsinking. I'm your opposite, much more at home with steel than with computers. First note: Don't count on the manufacturers of electrical equipment to use high quality bolts. That $200 Balmar alternator uses bolts you could find in little packets in a grocery store.

My practice is to pay careful attention to my torque wrench when doing engine repairs that are dependent on proper torque, such as the head gasket. Beyond that, I think that I have developed a feel for bolts, and pay attention to whether this is an ordinary common steel cut-thread hold-it-together bolt or a hardened rolled Grade 8. They feel different, for starters. Soft bolts stretch, and you can feel that in torquing them. I also pay attention to diameter, and avoid using a wrench that might twist off a small bolt - little bolts need little wrenches. Really little bolts need nut drivers.

I suspect that as you keep doing boat repairs you will develop this feel for hardware. Right now, the penalty for not having that feel is figuring out how to drill out and rethread the bolt in the Balmar.

A fun extercise might be to take a handful of various bolts, clamp them very tightly in your vise, and twist them off using various wrenches.
Well, I certainly do not have that feel yet but this was not an issue with the bolt. The part that tore off is the metal extension/lip of the rectifier where the thru-bolt was housed. There was no issue with the bolt. So I will likely have to buy another rectifier from balmar and rebuild the alt

I am really hoping I do not need to develop the feel for the hardware; from digital switches, electric motors and a couple personal design projects, I hope to have nearly all the mechanical hardware gone in 5 years. Usually I like breaking things, it is the only way I really learn. I just hope I figure out how to break things on my schedule (lol).
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Old 09-12-2021, 00:00   #6
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Re: A learning opportunity

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Originally Posted by JPA Cate View Post
I really like tkeithlu's answer.

One time, from not knowing what he has written, I broke off two small studs, on the rails the car seat was bolted to. You are not alone. With familiarity, and small wrenches for small nuts and bolts, and attentiveness, you're brain WILL just "get it." Trying the exercise he suggests may accelerate the process for you.

Sorry about your alternator bolt.

Ann
I really appreciate the advice and I understand the value in what he is saying, but that sort of 'feel' has never been a strength of mine. Maybe giving an exercise as suggested will help, it is certainly the type of training I have never really done in this application. However, to this point I have done a bit of work with stretch bolts, and maybe that has really thrown that 'feel' out of whack. Thanks BMW

Slightly different tangent but I know the marine industry is given a lot of leeway for hardware failures resultant of the marine environment. I used to think that was understandable. But as I've been doing quite a bit of my own work lately, I have noticed quite a difference in the way manuals are written; much less specific from general installation to the details of bolt torques. It seems like a small thing but given what appears to be a much higher failure rate, may speak to a lower engineering standard in design and testing. If I were doing this on any car, I would get a torque spec. That torque spec is not a random number. Pretty frustrating given the marine markup.
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Old 09-12-2021, 00:45   #7
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Re: A learning opportunity

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Originally Posted by Notyetsinking View Post
I recently tore off the alternator ground post of my new balmar alternator at 13ft/lbs of force (see attached).
never again use bolt to connection terminal like you here use
bolt-grounding post,terminal,nut,terminal nut
you have electrical reading but SS is not good for connection


you must use bolt grounding post. terminal 1 and on this terminal 2 washer nut 1 with Loctite or 2 nut
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