VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.


Go Back   VAF Forums > Model Specific > RV-14
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #11  
Old 03-04-2016, 04:37 PM
vic syracuse vic syracuse is offline
Super Moderator
 
Join Date: May 2005
Location: Locust Grove, GA
Posts: 2,678
Default Yes.

Yes, seen it both ways actually. Glad it will get installed.

Vic
__________________
Vic Syracuse

Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES
Kitplanes "Unairworthy" monthly feature
EAA Sport Aviation "Checkpoints" column
EAA Homebuilt Council Chair/member EAA BOD
Author "Pre-Buy Guide for Amateur-Built Aircraft"
www.Baselegaviation.com
Reply With Quote
  #12  
Old 03-04-2016, 05:34 PM
mburch's Avatar
mburch mburch is offline
 
Join Date: Feb 2005
Location: Northwestern USA
Posts: 1,232
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.
Yes Vic, these photos were just part of the fit-up stage from years back.

mcb
__________________
Matt Burch
RV-7 (last 90%)
http://www.rv7blog.com
VAF #836
Any opinions expressed in this message are my own and not those of my employer.
Reply With Quote
  #13  
Old 03-04-2016, 07:30 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,841
Default

Quote:
Originally Posted by rvbuilder2002 View Post
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 Reverse 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).
I guess I need some more educatin then.... I'm familiar with PFM (I gotta feeling that's what this must be) or this is just over my head

The original purpose of the 'I' terminal was a convenient place to pick off 12v during starter operation to bypass the coil resistor for better spark back in the day when cars had real distributors and one big coil.

You can see from the diagram below that the 'I' terminal is connected to the starter terminal inside the solenoid, this is just a bit "upstream" of the starter itself so unless there is some PFM happening somewhere in the wiring I'm not sure I understand what difference it would make connecting the solenoid using the 'I' terminal rather than the connecting it to the starter terminal.

Maybe that's why Skytec, who have some pretty smart folks working for them, can't seem to figure out why Van's does it this way.

__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 03-04-2016 at 07:47 PM.
Reply With Quote
  #14  
Old 03-04-2016, 08:10 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,203
Default

Ok Walt. I concede.

You have proven that you are way smarter than me (I already new that) and everyone else at Vans.



For everyone else.....
The only down side to wiring it this way is one extra wire that maybe weighs 10 grams with connector. Other than that it hurts nothing (except that it is wrong )

I have explained why Van's recommends doing it this way.... because of prior experience with start motor performance. With Van's business history, does anyone think anything would be added to the design if there wasn't some reason discovered at some point?
Regardless, it is a very simple thing to just delete the extra wire if you choose.

BTW Walt, The electrical lesson comment wasn't for you.... (I knew you would probably come back with an explanation of why it wasn't needed, regardless what I said)
It was for anyone (such as the OP) that was interested in hearing what the reasoning was (whether you agree with it or not).
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #15  
Old 03-04-2016, 08:44 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,841
Default

Scott,
I agree with you 99.99% of the time and always appreciate your posts, so please don't take my questioning the theory on this one personally. Maybe it works, I don't know, if it does my simple brain just fails to understand why it would. That's why electronics is so much fun, sometimes it just doesn't make sense. Then again perhaps its time to re-evaluate, just "because we've always done it that way" doesn't necessarily make it right.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 03-04-2016 at 08:55 PM.
Reply With Quote
  #16  
Old 03-04-2016, 10:33 PM
GeraldC GeraldC is offline
 
Join Date: Sep 2013
Location: Buda, TX
Posts: 56
Default

Walt, I think your schematic symbol for the contactor is making it more confusing than it is. Bob Nuckolls posted a better schematic symbol a while back that makes it more obvious what's going on.



The "I" terminal isn't connected to the exact same node as the output of the solenoid. It's a third connection, independent of the input and the output.
When the contactor opens, the "I" terminal disconnects from the output of the solenoid, which is not obvious from your diagram given the schematic symbol used in it.

Does that make sense?
Reply With Quote
  #17  
Old 03-04-2016, 11:22 PM
Isaac's Avatar
Isaac Isaac is offline
 
Join Date: Nov 2009
Location: Peoria, Az
Posts: 157
Default RE: Starter Disengage Wire

If you dig further into the SkytecAir.com website, and read the "Jumper Wire 101" discussion, Skytec recommends that when using the "Experimental Aircraft" wiring diagram, the starter push button switch should be sized to carry at or above 30 amps for the Lycoming PM/LS starters and at or above 20 amps for the Lycoming HT starters.

Reference Note 2 in the Experimental Aircraft Wiring diagrams.
http://www.skytecair.com/Jumper101.htm

Bob Nuckolls wrote an article detailing why when not using an external starter solenoid the starter switch needs to be able to handle large currents and why it is also hard on the starter push button switch.
http://www.aeroelectric.com/articles/strtctr.pdf

If you use the Vans Aircraft wiring implementation and as Skytec points out the wiring implementation used by almost all certified aircraft, the starter push button switch only needs to be rated to carry 3-4 amps. The upside of using the Vans recommended wiring for the starter is that a lower DC current rated switch can be used and the switch will see less wear and tear and should last longer. So in a round about way, I think SkyTec actually answers the question on why Vans does it they way they do.
__________________
___________
James
RV6 N947J
Reply With Quote
  #18  
Old 03-05-2016, 12:00 AM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,203
Default

Quote:
Originally Posted by GeraldC View Post
Walt, I think your schematic symbol for the contactor is making it more confusing than it is. Bob Nuckolls posted a better schematic symbol a while back that makes it more obvious what's going on.



The "I" terminal isn't connected to the exact same node as the output of the solenoid. It's a third connection, independent of the input and the output.
When the contactor opens, the "I" terminal disconnects from the output of the solenoid, which is not obvious from your diagram given the schematic symbol used in it.

Does that make sense?
Thanks Gerald.
Your diagram shows the mode of operation that I understood occurred, but at this point I will take nothing for granted.
As soon as I get a chance I will be taking a close look at how the start solenoid operates.
I will report here what I find.

Edit: After doing a quick search I found this text written by Bob Nuckolls in the discussion thread where the above diag was originally posted...

"At some later time, there was a rise in popularity
of PM motors on light weight starters. If wired
per the B&C philosophy, counter emf voltages
generated in the starter motor during spin-down
would keep the jumpered, built-in contactor
energize for seconds after the starter button
was released."


And....

"There is another option for adding the external
contactor on a PM starter and dealing with the
run-on problem.

You can use the contactor's "I" terminal
to energize the solenoid-contactor yet
release it the same time that the starter
switch opens. "


PM starter means Permanent Magnet starter..... one that will turn into a generator while being driven by the engine.
I will do some testing to confirm that the start solenoid currently sold by Van's actually functions as detailed in the diagram.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")

Last edited by rvbuilder2002 : 03-05-2016 at 01:02 AM.
Reply With Quote
  #19  
Old 03-05-2016, 12:02 AM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,203
Default

Quote:
Originally Posted by airguy View Post
It's fiberglass - it'll fit - sometimes before, sometimes after we work on it. Some field adaptations require more effort than others, that doesn't make them wrong.

As for the rest - Scott, we appreciate that you know a bunch of stuff, and that you are trying to "educate the masses", but there are occasionally folks out here that know stuff too. It would be nice if you quit trying to be the smartest guy in the room.

Just my 2 cents, but I've only got 3 degrees, what do I know?
And this brings what valuable input to the discussion?
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #20  
Old 03-05-2016, 06:04 AM
Ron B. Ron B. is offline
 
Join Date: Nov 2007
Location: Yarmouth, Nova Scotia
Posts: 2,490
Default

Thanks Scott
If the contactor was designed as in Walt's diagram I see no advantage to making a change from Skytec's method, but as shown in Gerald's diagram I see the difference.
I will wire mine as per Van's instructions.
__________________
Thanks Ron
RV-10 SOLD
RV-14 Flying
AirCam flying
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 11:15 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.