VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #11  
Old 03-27-2017, 01:24 PM
smash smash is offline
 
Join Date: Apr 2013
Location: Fair Oaks,CA
Posts: 36
Default Starter Contacter orientation

I just attended the SportAir class on electrical systems and the instructor advised against orienting the starter motor contactor vertically (as shown in picture below). The g-forces of aerobatics can cause the contactor to close thus engaging the starter uncommanded. He advised to mount it 90 degrees to vertical. How are others mounting their starter contactors?
__________________
http://www.smashsrv-14build.com
Reply With Quote
  #12  
Old 03-27-2017, 01:44 PM
rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGG
Posts: 1,998
Default starter contactor orientation

This seems to be an "old wives tale" according to Bob:

http://forums.matronics.com/viewtopi...065c2bd53a61d6

Quote:
Originally Posted by bob nuckolls
I have yet to put my hands on any
failure of hardware that supports any notion of risk
due to airframe induced g-loads.
__________________
Mickey Coggins
http://rv8.ch
Reply With Quote
  #13  
Old 03-27-2017, 01:44 PM
n982sx n982sx is offline
 
Join Date: Apr 2010
Location: Chicago, IL
Posts: 163
Default

Quote:
Originally Posted by smash View Post
The g-forces of aerobatics can cause the contactor to close thus engaging the starter uncommanded. He advised to mount it 90 degrees to vertical. How are others mounting their starter contactors?
First, neither of those are starter contactors. They are both continuous duty contactors, in this case, for ground power and bus cross feed. They are not part of the kit and Van's has no responsibility for them.

Second, for what it's worth, the starter contactor supplied by Van's in the firewall forward kit mounts at about a 45 angle.

I have no knowledge about the efficacy of the SportAir workshop remark.
__________________
Bob Meyers

Built and Flying RV-14A N626KM SN 140093 http://n626km.com
Built and Flying Sonex N982SX http://n982sx.com
Reply With Quote
  #14  
Old 03-27-2017, 01:56 PM
Av8rRob's Avatar
Av8rRob Av8rRob is offline
 
Join Date: May 2005
Posts: 135
Default

I also took the sport air workshop with Smash and found it curious that the -14 has its start/master solenoids mounted at the 45 deg. I might have to call Vans to ask their thoughts on the subject.
__________________
Rob Lasater
Rv-14 Fuse
Paid nov 2016
Reply With Quote
  #15  
Old 06-20-2017, 11:58 AM
Erimo's Avatar
Erimo Erimo is offline
 
Join Date: Jul 2015
Location: Marcoussis, France
Posts: 13
Default Relays clocking

So, did you have Van's answer ?
Reply With Quote
  #16  
Old 06-20-2017, 12:47 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 6,586
Default

Quote:
Originally Posted by rv8ch View Post
This seems to be an "old wives tale" according to Bob:

http://forums.matronics.com/viewtopi...065c2bd53a61d6
I don't agree with Bob's analysis since it is clear that he doesn't know which way the plunger of the contactor is moving relative to the vertical axis of an airplane if the brackets are mounted flush to a firewall ( In this configuration, the plunger could never be aligned with the longitudinal axis).
He also mentions looking at hundreds of T.C. aircraft...... I wonder how many of them were approved to purposely be experiencing 6+ g's during flight on a regular basis.

The contactors are mounted at 45* on the RV-14 because it is convenient for structural reasons and that then largely takes care of any possible issue as a result of pos. or neg G's.

BTW, there is nothing wrong with mounting the start contactor with the plunger vertical as long as you know which way the plunger moves, you mount it so it can only be influenced by neg. G's, and then you avoid high neg G's (likely 99.9% of all RV owners do).
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #17  
Old 06-20-2017, 03:21 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 1,976
Default

Easy to prove or disprove. Weigh the plunger. Measure the force required to overcome spring force to close the contacts, if oriented that way. Compare.

If oriented the other way, measure the force required to open the contacts against force applied by the coil while it's active. Compare.

While I don't know this with certainty, I suspect that Bob's done that.

Charlie
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 04:36 AM.


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.