Glow Plug choice for profile .28 engine

[Marty Hammersmith]

     I did search throughout the site before creating this thread. There doesn't seem to be any consensus on glow plug selection. I have a used Blue Bird .28 r/c engine someone has converted to control line on my Ringmaster S-1. I maidened today and the engine ran fine on an OS #8 but should I be considering other glow plugs? My standard control line fuel is about 8% nitro with 21% oil (this is a dual bearing engine). Oil is approximately 50/50 synthetic/castor.

[Dave_Trible]

Marty this may become the wrong question you will find.   This might end up being "where can I buy ANY glow plugs?"  They have gotten very scarce and expensive.  The insane price of materials to make them just about put every supplier out of business.  However if your #8 OS works good there seems to be plenty of those from oversees on Ebay.  Brodak may have a some Fireballs.  Last I looked Sonic Tronics has some non-idle bar longs on hand (these are pretty good).  I just received some great looking plugs from TCA Racing in Milano, Italy.  They are priced very reasonably- possibly due to the exchange rate.  Their service is good and fast!  I had my order from Italy in about five days.  I haven't had opportunity to try them yet but I'm betting on good quality.  They look quite like Glow Devils.  Other than that you may pay $18.00 to $20.00 bucks for plugs domestically. 
Your fuel sounds about right for your engine and as long as the plugs you have are keeping the fire lit then use what you have.

Dave

[Colin McRae]

     I did search throughout the site before creating this thread. There doesn't seem to be any consensus on glow plug selection. I have a used Blue Bird .28 r/c engine someone has converted to control line on my Ringmaster S-1. I maidened today and the engine ran fine on an OS #8 but should I be considering other glow plugs? My standard control line fuel is about 8% nitro with 21% oil (this is a dual bearing engine). Oil is approximately 50/50 synthetic/castor.

Marty, if your engine 'ran fine' on the OS #8 then just stay with it. The OS #8 is a med-hot temperature range plug.

The best way to see if your engine needs a different plug is to see what happens when you remove the power from the plug after the engine is started and running. If the engine is running OK with power supplied, but the rpm sags when power is removed, then the plug is not hot enough. As a rule of thumb, low nitro fuels (and I would consider 8% low nitro) need a hot plug. The OS A3 (A6) is a hot plug.

Due to cost, Brodak sells Fireball plugs for $5 and I have used them with no issues. Fireball makes a hot and medium-hot (what they call standard) plugs.

Also, for a CL engine application, I don't use a plug with an idle bar. Idle bar plugs are intended for RC engines with carburetors where the engine speed is varied. The 'idle' bar is just as stated. Helps keeps fuel off the plug element at idle conditions. Not needed for full speed CL application.

[Dan McEntee]

Marty, if your engine 'ran fine' on the OS #8 then just stay with it. The OS #8 is a med-hot temperature range plug.

The best way to see if your engine needs a different plug is to see what happens when you remove the power from the plug after the engine is started and running. If the engine is running OK with power supplied, but the rpm sags when power is removed, then the plus is not hot enough. As a rule of thumb, low nitro fuels (and I would consider 8% low nitro) need a hot plug. The OS A3 (A6) is a hot plug.

Due to cost, Brodak sells Fireball plugs for $5 and I have used them with no issues. Fireball makes a hot and medium-hot (what they call standard) plugs.

Also, for a CL engine application, I don't use a plug with an idle bar. Idle bar plugs are intended for RC engines with carburetors where the engine speed is varied. The 'idle' bar is just as stated. Helps keeps fuel off the plug element at idle conditions. Not needed for full speed CL application.

   I don't have any insight as to whether the situation with glow plugs will get any better or not. I have a pretty good supply and I'm always keeping my eyes peeled just in case I run across something.

  Colin McRae said;
   "Also, for a CL engine application, I don't use a plug with an idle bar. Idle bar plugs are intended for RC engines with carburetors where the engine speed is varied. The 'idle' bar is just as stated. Helps keeps fuel off the plug element at idle conditions. Not needed for full speed CL application. "

    Some of us use idle bar plugs for a reason. It acts as a barrier to protect the element against debris getting into that chamber and distorting, damaging or shorting the element. It also give carbon a place to form instead of inside the chamber or covering it up as it accumulated. If you fly ringed engines or have any appreciable amount of castor oil in your fuel, it will make carbon when it runs and it will build up where ever it can stick to. I have seen plugs that have been in an engine so long that the opening under the idle bar gets covered up and the engine starts running rough, but the engine would still run. This is usually a gradual process. If the idle bar wasn't there , it would accumulate right over the element in less time. It may chose to quit or really fall of at a bad time, like right before the model reaches the top of the wingover or just as you are finishing the clover!!
  In R/C, fuel still needs to reach the element at all times. That is how a glow engine works, a catalytic reaction between the methanol and the metal the coil is made from. Have you even had an engine start without warning before you attached the battery? Happens all the time if conditions are right.

  Type at you later,
   Dan McEntee

[bill bischoff]

O"Donnell has some glow plugs that work well for me. They have an 005 (med-hot) and an 008 (hot). According to their comparison chart, the 005 is similar to a McCoy MC59, and the 008 is similar to a McCoy MC55.
You can order them direct from O'Donnell for $8.00 and $9.50 each, which is reasonable these days. They sell them individually, so you don't have to buy a dozen just to try them. odonnellglowplugs.com

[Marty Hammersmith]

     Thanks for the Brodak mention for glow plugs. I'll add some to my next order!

[Lyle Spiegel]

Go to Mikegoesflying online store. I just bought a bunch of the #3 hot, w/o idle bar.   I Regret the idle bar GloDevils are no longer.

[Colin McRae]

   I don't have any insight as to whether the situation with glow plugs will get any better or not. I have a pretty good supply and I'm always keeping my eyes peeled just in case I run across something.

  Colin McRae said;
   "Also, for a CL engine application, I don't use a plug with an idle bar. Idle bar plugs are intended for RC engines with carburetors where the engine speed is varied. The 'idle' bar is just as stated. Helps keeps fuel off the plug element at idle conditions. Not needed for full speed CL application. "

    Some of us use idle bar plugs for a reason. It acts as a barrier to protect the element against debris getting into that chamber and distorting, damaging or shorting the element. It also give carbon a place to form instead of inside the chamber or covering it up as it accumulated. If you fly ringed engines or have any appreciable amount of castor oil in your fuel, it will make carbon when it runs and it will build up where ever it can stick to. I have seen plugs that have been in an engine so long that the opening under the idle bar gets covered up and the engine starts running rough, but the engine would still run. This is usually a gradual process. If the idle bar wasn't there , it would accumulate right over the element in less time. It may chose to quit or really fall of at a bad time, like right before the model reaches the top of the wingover or just as you are finishing the clover!!
  In R/C, fuel still needs to reach the element at all times. That is how a glow engine works, a catalytic reaction between the methanol and the metal the coil is made from. Have you even had an engine start without warning before you attached the battery? Happens all the time if conditions are right.

  Type at you later,
   Dan McEntee

Dan, I understand your comments concerning the potential additional benefits of idle bar plugs. I was only trying to say the idle bar design is not necessary for 'typical' CL flying. And I don't believe the lower cost Fireball plugs have an idle bar offering. If they do, I am unaware of it.

[Brian Hampton]

Bit of history first up. Bluebird was rebadged as Brat for the American market (no idea why). All Bluebirds 21, 25, 28 and 46 are AAC but for some reason the 51 is ABC. I have an unrun 28, not NIB because I stripped it down to have a look inside to take photos and to check things like port timings and compressions with both an OS plug and normal long reach.

The instruction manual recommends a fuel with 23% all castor but never less than 20% so your fuel should be fine. Ideally the plug length should be a long plug but if yours works fine with the OS plug then stay with it. Strangely the instructions mention using a cold plug but, once again, if you're happy with the OS then keep it.

[Marty Hammersmith]

Hi Brian. Thanks for the history but I am familiar with it. Indy R/C was just up the road and sold these engines as Blue Bird.  Dave Brown was a personal friend. He sold the Brats. He just passed away a few weeks ago. Time just marches on. Ugh. I own only the .25 and .28s in both brands.

Thanks to someone's input here, I switched over to the hotter A3/#6 OS glowplug based on my 8% nitro fuel. It didnt hurt. Just came in from a dozen flights. They're consistent from start to finish in 2 stroke. They're not timed for 4-2-4 break. Very happy with how its performing on a wide blade 10 x 4 prop.