stunthanger.com

Engine basics => Engine set up tips => Topic started by: Peter in Fairfax, VA on September 16, 2023, 08:24:07 PM

Title: Glow Plug Experience
Post by: Peter in Fairfax, VA on September 16, 2023, 08:24:07 PM
Looking for comment on today's flying experience.

I run an O.S. SF 46 on 5% nitro, 20% oil.  The engine has been very reliable for multiple seasons.  However, it developed a problem where it would run poorly when I hit a hard outside as part of a lazy 8.  I tried needle settings and tank height.  It got progressively worse and finally cut out inverted halfway through a flight.  I was able to land safely and finally changed the plug.  Now it runs great and I'm back to working on my pattern for an upcoming contest (NVCL Stuntfest next Saturday.)

The old plug was a K&B 1L that had given long, excellent service.  The new plug is a Fox R/C Long.  My understanding is the K&B is cooler, and the Fox idle bar is both hotter and more tolerant of richness.

What is it about a plug that goes bad?  The bad plug looked just fine, visually.

Thoughts?

thanks,

Peter
Title: Re: Glow Plug Experience
Post by: Dave Hull on September 16, 2023, 08:53:10 PM
Probably eroded and oxidized the surface of the wire, meaning there was less and less clean surface to initiate a catalytic reaction. I'd assume it is pretty much the same mechanism that kills the cataclysmic reverter in your automobile.

If the wire is no longer shiny, but more "frosty" or whitish-looking, then that's what you've got.
Title: Re: Glow Plug Experience
Post by: Dan McEntee on September 16, 2023, 09:40:48 PM
  The problem could be the Fox plug also, depending on the vintage. I know that you have access to lots of new old stock, but try another known reliable good brand of plug before doing anything drastic.
  Type at you later,
  Dan McEntee
Title: Re: Glow Plug Experience
Post by: Peter in Fairfax, VA on September 17, 2023, 03:42:45 AM
The Fox plug worked great. One test flight to confirm the engine was adequate, then pattern after pattern.  I've had excellent luck with the Fox brand.  Most of my stock of those is old, as Dan notes.  I have some newer Fox plugs (orange package vs red/white/blue,) but the older ones are my go-to as known good.

The K&B looked fine; shiny wire.  Though it makes sense that it had some barrier.  If I was really well organized, I might look at it with a microscope.  I was even wondering if somehow the catalyst chemical, iridium in the platinum family, had somehow departed.

thanks for the discussion and information,

Peter
Title: Re: Glow Plug Experience
Post by: Motorman on September 17, 2023, 08:14:05 AM
Deleted
Title: Re: Glow Plug Experience
Post by: Istvan Travnik on September 17, 2023, 05:18:38 PM
Dear Friends,
once (or more) upon a time we discussed a lot about gloplug problems.
I digged out from the past my solutions and photos in this theme, see:
https://stunthanger.com/smf/open-forum/glow-plug-measurements/
 ( thread  #17 )
Istvan
Title: Re: Glow Plug Experience
Post by: Steve Helmick on September 25, 2023, 05:42:12 PM
I wouldn't walk across the street for a full card (dozen) of Fox glowplugs. The K&B was made by Ohlsson Corporation, and they make several brands...all good. Thunderbolts are made by Ohlsson Corporation. They are the remains of the O&R engine company. OS & Enya glowplugs are also very good, but cost even more.  y1 Steve