VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics

  #1  
Old 12-28-2019, 05:19 AM
74-07 74-07 is offline
 
Join Date: Dec 2016
Location: Greenville, SC
Posts: 478
Default Slow cranking results found

Read up on all of the other threads. RV-8, 320 hours, IO360 200 hp., one blade and stop then, next try would crank. Used all the info here and once again, like many others, found starter contactor burned and pitted. Replacing both contactors. I do have one question. The airplane has EXP2 Bus system. Starter contactor has diode but master does not. Any reason they both shouldn't have a diode?
Reply With Quote
  #2  
Old 12-28-2019, 06:03 AM
vic syracuse vic syracuse is offline
Super Moderator
 
Join Date: May 2005
Location: Locust Grove, GA
Posts: 2,631
Default

Put a diode on both solenoids.
__________________
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
  #3  
Old 12-28-2019, 06:20 AM
74-07 74-07 is offline
 
Join Date: Dec 2016
Location: Greenville, SC
Posts: 478
Default

Thanks Vic. Got them ordered.
Reply With Quote
  #4  
Old 12-28-2019, 07:46 AM
JonJay's Avatar
JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
Default

How many hours?
Where was it pitted and burned?
The “contact” is a disk that should rotate freely. Near as I can tell, the intent is for vibration to allow that disk to randomly move allowing a “fresh” surface to contact the terminals.
I inspected mine at about 500 hours and the disk was fine. A few small arc traces and very minor discoloration in a couple spots but not even close to failure. No pitting.

The original Vans electrical diagrams do not call out a diode on the Master Contactor but I agree with Vic. So does Aeroelectric.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.

RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
Reply With Quote
  #5  
Old 12-28-2019, 08:08 AM
snopercod's Avatar
snopercod snopercod is offline
 
Join Date: Aug 2016
Location: Asheville, NC
Posts: 2,112
Default

Diodes across the coils are necessary, but you have to realize that they only protect the switches activating the solenoids. I installed the diodes to protect the starter switch and master switch, but I really wanted to protect the starter contacts. So I installed two large 18V DC MOVs across the starter solenoid contacts, from one contact to the center plunger, and from there to the other contact.
__________________
(2020 dues paid)
Reply With Quote
  #6  
Old 12-28-2019, 08:22 AM
74-07 74-07 is offline
 
Join Date: Dec 2016
Location: Greenville, SC
Posts: 478
Default

Jonjay,

The disc was pretty severly burned/pitted. I would post photos but I'm just photo challenged on this site. Also, interestingly, the disc apeared to have been moving but not 360 degrees as the pits were each in about a 100 degree arc. One contact was burned/pitted on one corner. I suspect the contact was rotated during aircraft assembly and was only touching the disc on that corner. 320 hours

Last edited by 74-07 : 12-28-2019 at 08:26 AM.
Reply With Quote
  #7  
Old 12-28-2019, 09:29 AM
Ironflight's Avatar
Ironflight Ironflight is offline
VAF Moderator / Line Boy
 
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,268
Default

Since the topic hasn’t been discussed here for several years, I’ll bring it up again. It is important that when you tighten the nuts to attach wires to the big studs on a contractor, you back up (hold) the inner nut while tightening the outer one. If you don’t you end up rotating the stud slightly in the case. The stud is just a square headed bolt and the bolt head is what the contact disk touches to complete the circuit. If this twists even slightly, the disk will only make contact on the corner - a much smaller area - and this will cause pitting, scorching, and decreased conductivity. If you keep the bolt/stud in the correct position, you will have much longer life, and better performance.

Paul
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
Reply With Quote
  #8  
Old 12-28-2019, 09:32 AM
JonJay's Avatar
JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
Default

Quote:
Originally Posted by 74-07 View Post
Jonjay,

The disc was pretty severly burned/pitted. I would post photos but I'm just photo challenged on this site. Also, interestingly, the disc apeared to have been moving but not 360 degrees as the pits were each in about a 100 degree arc. One contact was burned/pitted on one corner. I suspect the contact was rotated during aircraft assembly and was only touching the disc on that corner. 320 hours
I bet you’re right about the contact rotating. That is all too common as you can’t get a normal wrench on the post to hold it while you torque down the nut. Many just crank it down without realizing the post turned, which rotates the internal contact. Then you have a sharp edge with little surface area making contact with the disk. Just a matter of time to failure.

(Paul was typing while I was!)
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.

RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
Reply With Quote
  #9  
Old 12-28-2019, 10:13 AM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,229
Default

Quote:
Originally Posted by Ironflight View Post
Since the topic hasn?t been discussed here for several years, I?ll bring it up again. It is important that when you tighten the nuts to attach wires to the big studs on a contractor, you back up (hold) the inner nut while tightening the outer one. If you don?t you end up rotating the stud slightly in the case. The stud is just a square headed bolt and the bolt head is what the contact disk touches to complete the circuit. If this twists even slightly, the disk will only make contact on the corner - a much smaller area - and this will cause pitting, scorching, and decreased conductivity. If you keep the bolt/stud in the correct position, you will have much longer life, and better performance.

Paul
One of the challenges I've found is that the inner nut is really hard to hold with conventional tools. The nut thickness is less than a typical nut and my wrenches are too fat to fit.

I'm sure I've solved this problem before, but don't remember what I did... (Maybe ignition wrenches??)
__________________
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
Reply With Quote
  #10  
Old 12-28-2019, 10:35 AM
JonJay's Avatar
JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
Default

Quote:
Originally Posted by Kyle Boatright View Post
One of the challenges I've found is that the inner nut is really hard to hold with conventional tools. The nut thickness is less than a typical nut and my wrenches are too fat to fit.

I'm sure I've solved this problem before, but don't remember what I did... (Maybe ignition wrenches??)
I ground down a few wrenches. 10mm for the control terminals and 14mm for the high amp. I think, Don?t hold me to that!
I keep all the cheap old wrenches I finding so if I need to weld, grind, bend, or whatever to make a special tool, I have the stock.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.

RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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 04:16 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.