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  #1  
Old 03-03-2016, 07:44 PM
Ron B. Ron B. is offline
 
Join Date: Nov 2007
Location: Yarmouth, Nova Scotia
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Default Starter disengage wire

Van's has us remove a jumper wire on the starter and install a wire from the starter relay (on the "I" terminal) and run it to on the small terminal on the starter where you removed the jumper from.
Can someone explain the reasoning to me, enquiring mines need to know? They call this wire a disengage wire rather than an engaging wire.
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  #2  
Old 03-03-2016, 08:17 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by Ron B. View Post
Van's has us remove a jumper wire on the starter and install a wire from the starter relay (on the "I" terminal) and run it to on the small terminal on the starter where you removed the jumper from.
Can someone explain the reasoning to me, enquiring mines need to know? They call this wire a disengage wire rather than an engaging wire.
Since I don't want enquiring mines to possibly explode while thinking hard ....

It is an optional method of controlling the starter activation.

If the jumper is left in and used to activate the solenoid, the starter functions fine, but is slower to disengage when the key is released. In some instances there is a noise that is unsettling to some passengers (but Skytech says it is not detrimental to the starter).
If the I terminal is used to control the solenoid, the starter drive disengages more cleanly.
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  #3  
Old 03-04-2016, 05:43 AM
Ron B. Ron B. is offline
 
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Thanks Scott, I would have sleep better had I known this last evening.
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  #4  
Old 03-04-2016, 07:33 AM
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Walt Walt is offline
 
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Default

With all due respect to Van's you may want to review the following advice/diagrams from Skytec prior to wiring the starter.
I'm not a big fan of the LS starter for multiple reasons, do yourself a favor and upgrade to an NL or the B&C.

http://www.skytecair.com/Wiring_diag.htm
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Last edited by Walt : 03-04-2016 at 07:38 AM.
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  #5  
Old 03-04-2016, 09:47 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Ok, it looks like a little DC electrical lesson is in order.....

I only have a basic 2 year electronics degree (from many many many years ago so I have forgotten the majority of it) so I don't claim to be anywhere near someone that can speak with any authority on the subject, so I fully expect others to chime in and correct me where needed.

When the jumper is left in place on a Skytech starter to avoid using a second activation wire routed to the solenoid, the power input side of the solenoid is connected directly to the power input of the starter motor.

When the start circuit is activated, the starter motor and the solenoid are both fed power via that one wire, the motor turns and the solenoid pushes the drive gear fwd to engage the ring gear of the engine making the engine turn.

When the start circuit is deactivated, power is removed from the starter motor and the solenoid, but the solenoid is still electrically connected to the +V input side of the motor.

Why does this matter? Because at this point the starter motor has now converted to being a DC generator. It is still spinning (driven by the now started engine) and with its power input connected to the solenoid, the Counter EMF produced by the spinning motor works against the collapsing field of the solenoid coil. This keeps the solenoid/starter drive engaged for longer than it would be if the power was interrupted instantly as happens when a separate activation wire is used.

This delay can be quite noticeable in some instances, and as I mentioned previously can cause an annoying noise that has the sound of an unhappy mechanical device. Particularly in instances where the engine goes to a rather high RPM immediately after starting (higher the RPM, the stronger the EMF that is produced).

As I said in my first post, Skytech has always said this was not detrimental to the life of the starter (do we know that for sure?), and that doing it the Van's way was optional.

I find it interesting that they now have this diagram on their web site and they say they don't know why Van's does it this way.... Well as far as I am aware, no one at Skytech has ever called to ask!

BTW, this wiring scheme was not my idea. It was conceived by the late Bill Bennedict... former general manager of Van's Aircraft (and Electrical Engineer)

BTW X2, I recommend caution in arbitrarily changing to the NL starter. If you are using the Van's supplied fwd facing induction system (affectionately referred to as the snorkel), an NL starter motor wont fit.

Bottom line? It is experimental... you can do what you want. We have been doing it this way for 18+ years and we get very good life out of our starter motors (and our normal mode of operation results in probably way more engine starts per hour than the average user).
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

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Last edited by rvbuilder2002 : 03-05-2016 at 01:06 AM. Reason: Corrected erroneously written Reverse EMF to Counter EMF
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  #6  
Old 03-04-2016, 10:07 AM
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mburch mburch is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
BTW X2, I recommend caution in arbitrarily changing to the NL starter. If you are using the Van's supplied fwd facing induction system (affectionately referred to as the snorkel), an NL starter motor wont fit.
It fit okay in my airplane, Scott, once I ground off the superfluous mounting lugs in accordance with Skytec's installation instructions. I had to do a bunch of fiberglass work to get the snorkel to fit around the alternator, but the starter required no fiberglass modifications.



(note: the above photos were taken during the fit-up process, all fasteners are temporary)

mcb
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Last edited by mburch : 03-04-2016 at 05:43 PM.
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  #7  
Old 03-04-2016, 10:12 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by mburch View Post
It fit okay in my airplane, Scott, once I ground off the superfluous mounting lugs in accordance with Skytec's installation instructions. I had to do a bunch of fiberglass work to get the snorkel to fit around the alternator, but the starter required no fiberglass modifications.



mcb
Good to know.
I am still not sure it would work for all installations.
For example, the RV-14 comes with a molded fiberglass filter frame frame for the top. This limits the amount of positioning latitude available while doing the installation.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

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  #8  
Old 03-04-2016, 11:47 AM
BillL BillL is offline
 
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Default Thanks for th explanation

Quote:
Originally Posted by rvbuilder2002 View Post
Ok, it looks like a little DC electrical lesson is in order.....
Thanks Scott, I was thinking back EMF was the issue, but probably combined with the fact that experimental uses some lightweight props with lower inertia and the engine winds up pretty fast on the first firings.

This is my reasoning why a certificated application may not need or use this wiring method.
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  #9  
Old 03-04-2016, 12:33 PM
vic syracuse vic syracuse is offline
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Default Temporary?

Is it just temporarily fitted? There is a missing stud/nut on the forward left mounting hole of the starter to the engine.

Vic
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  #10  
Old 03-04-2016, 12:42 PM
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az_gila az_gila is offline
 
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Default

Quote:
Originally Posted by vic syracuse View Post
Is it just temporarily fitted? There is a missing stud/nut on the forward left mounting hole of the starter to the engine.

Vic
It is missing, but on my O-360 that is listed as a bolt, not a stud/nut.... much easier to add later...
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Last edited by az_gila : 03-04-2016 at 12:48 PM.
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