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Ok to bend uninsulated ring terminals?

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plevyakh

Joined: 10 Jan 2011
Posts: 39

Posted: Sat May 14, 2011 8:20 am Post subject: Ok to bend uninsulated ring terminals?

Bob,

I'm installing my L-60 alternator and have an issue with clearance of the B-lead nut and trying to install an uninsulated Ring Terminal (4AWG, .25" Stud).   The standard flat terminal directs the wire 90 degrees from the B-lead nut.



I need the wire to run AFT or parallel to the B-Lead post to be able to feed it through my front right engine baffle and then towards the starter contactor sitting on the firewall.



Is it acceptable to bend the uninsulated ring terminal 75 to 90 degrees?   Or is there a different #4AWG terminal I could use that would allow the wire to come off the B-Lead post pointing AFT instead of perpendicular to the post?



Thanks,

Howard

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_________________
Howard Plevyak
GlaStar / Cincinnati, Ohio

nuckolls.bob(at)aeroelect
Guest

Posted: Sat May 14, 2011 10:41 am Post subject: Ok to bend uninsulated ring terminals?

At 12:20 PM 5/14/2011, you wrote:

 	  Quote: 	
		  



Bob,

I'm installing my L-60 alternator and have an issue with clearance 

of the B-lead nut and trying to install an uninsulated Ring Terminal 

(4AWG, .25" Stud).   The standard flat terminal directs the wire 90 

degrees from the B-lead nut.



I need the wire to run AFT or parallel to the B-Lead post to be able 

to feed it through my front right engine baffle and then towards the 

starter contactor sitting on the firewall.



Is it acceptable to bend the uninsulated ring terminal 75 to 90 

degrees?   Or is there a different #4AWG terminal I could use that 

would allow the wire to come off the B-Lead post pointing AFT 

instead of perpendicular to the post?


	


   Sure. But one bend only. After all, the barrel

   of a ring terminal is "bent" to form the barrel.

   There are terminals with factory-bent flags that

   accommodate the functionality you're needing. Those

   products might be heat-treated after the bending

   operation for stress relief . . . but not necessarily

   so.



   All metals have a relatively predictable behavior

   with respect to stresses in the material and the

   number of times that stress can be applied before

   failure occurs.



   I'm told that this characteristic gave rise to

   an early-on requirement for running an engine

   for 75 hours on a test stand as part of the

   certification process. Not that 75 hours of 'service

   life' was good enough.  It was based on the premise

   that if a ferrous (iron based) parts did not fail

   in 10 million cycles at rated stresses, it wasn't

   going to fail during service life due to overstress.



   That didn't mean the engine wouldn't wear out in

   200 hours . . . it just meant that it wasn't going

   suffer breakage at those stress levels.



   Non-ferrous parts (copper, alum, etc) behave a bit

   differently. They DO have a stress-to-cycles service

   life. Furthermore, it's a non-linear curve. For example:

   You might bend your copper terminal over a 90 degree

   flex say 10 times before it cracks. Change that

   to 45 degrees and the number goes up markedly . . .

   say 50 times. Change that to a vibratory oscillation

   that deflects it just a fraction of a degree, and the

   number might be in the millions of cycles . . . BUT IT

   WILL break eventually, even at that small level of

   deflection.



   This is why wings have been known to fall off and cabin

   tops have blown out of venerable airplanes. The

   phenomenon can usually be traced to an error of analysis

   for the stress-to-events ratio of the part that failed.



   So you're safe in forming the flag on your terminals

   as needed to accommodate the installation but strive

   minimize the number of events for this very severe

   stress on the material. Know that by doing this one

   bend, you have reduced the service life by some

   large but probably insignificant number (1 billion

   down to 800 million????) for the as-installed

   condition.



   This is why it's a good idea to limit the stress

   applied to such terminals by supporting the wire

   as close as practical to the terminal or perhaps

   fabricating the wire from some very flexible material

   (like welding cable) to minimize that wire's ability

   to apply a lever-moment (length x mass) to the

   terminal.



   Taking the b-lead wire immediately away from the

   alternator to attach at some point on the airframe

   does not offer much means for near-terminal support

   of that wire. In fact, the terminal end will be

   shaking with the amplitude of engine vibration

   while the airframe end is much more stationary.



   Can you leave the terminal flat, support the wire

   close to the terminal and then route off to the

   airframe?



   The same admonition applies to bolting fat-wires to

   the lead posts on many of the RG batteries we're

   so fond of. Lead posts have a similarly non-linear

   s/n to failure curve. In years past, we've heard

   from builders who suffered a battery post failure

   due to vibrations stresses of a 2AWG jumper wire

   bolted to the battery.



   This is why we've recommended 4AWG welding cable

   jumpers from the (+) post to contactor and (-) post

   to ground for such batteries . . . irrespective

   of the size of fat wires elsewhere in the system.

   You might want to consider a welding cable jumper

   from your alternator's b-lead to where ever that

   segment ties off to the rest of the system.



   These are gross examples of what that copper sleeve

   inside the insulator of a PIDG terminal is all about.

   When you mashed the terminal on the wire, you placed

   the wire under severe stress to achieve the gas-tight

   connection. Support immediately adjacent to that

   stress riser is key to long service life.



   The terminal itself benefits from the same consideration

   for reducing cyclic stresses to the material.



   Bob . . .

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rjquillin(at)cox.net
Guest

Posted: Sat May 14, 2011 11:28 am Post subject: Ok to bend uninsulated ring terminals?

On 5/14/2011 11:36, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 At 12:20 PM 5/14/2011, you wrote:

> 

>

> Bob,

> I'm installing my L-60 alternator and have an issue with clearance of 

> the B-lead nut and trying to install an uninsulated Ring Terminal 

> (4AWG, .25" Stud).   The standard flat terminal directs the wire 90 

> degrees from the B-lead nut.

>

> I need the wire to run AFT or parallel to the B-Lead post to be able 

> to feed it through my front right engine baffle and then towards the 

> starter contactor sitting on the firewall.

>

> Is it acceptable to bend the uninsulated ring terminal 75 to 90 

> degrees?   Or is there a different #4AWG terminal I could use that 

> would allow the wire to come off the B-Lead post pointing AFT instead 

> of perpendicular to the post?



   Sure. But one bend only. After all, the barrel of a ring terminal is 

 "bent" to form the barrel.

   There are terminals with factory-bent flags that  ccommodate the 

 functionality you're needing. Those

   products might be heat-treated after the bending  operation for 

 stress relief . . . but not necessarily so.


	


I would suggest an effort to maximize the bend radius would also prove 

wise to distribute stress, as opposed to a minimal radius 'sharp' 90 

degree bend that would concentrate it; as one might obtain by clamping 

the ring in a vise and whacking the crimp barrel over with a hammer 

would likely produce.

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat May 14, 2011 1:08 pm Post subject: Ok to bend uninsulated ring terminals?

 	  Quote: 	
		  I would suggest an effort to maximize the bend radius would also prove wise to distribute stress, as opposed to a minimal radius 'sharp' 90 degree bend that would concentrate it; as one might obtain by clamping the ring in a vise and whacking the crimp barrel over with a hammer would likely produce. 	


    Excellent point.  If one has an 1/8" piece

    of aluminum or mild steel from which to fabricate

    a bend radius tool . . .

 [img]cid:7.1.0.9.0.20110514165610.01db16f8(at)aeroelectric.com.0[/img] 



    Bob. . .



 



 

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   Bob . . .

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plevyakh

Joined: 10 Jan 2011
Posts: 39

Posted: Sat May 14, 2011 2:03 pm Post subject: Re: Ok to bend uninsulated ring terminals?

I'll try to maximize the bend radius and support the wire as well.   



Thank-you both for the replies.   Just what I needed to keep making progress.



Howard

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_________________
Howard Plevyak
GlaStar / Cincinnati, Ohio

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