GrahamC

Yes, the .045" was from the Mecoa head.

The use of the anti seize with the Nelson plugs is simply to ensure that the plug does not gall in the aluminum head and hopefully permits the plug to be removed when needed.

Yes, using multiple head gaskets with the Galbreath head does in fact reduce the compression ratio (among other things).

Anti-sieze on the head threads and on the gaskets. Intesting idea. It may have some benefit on the head to cylinder threads such that you don't the the head siezed in the cylinder but would have no benefit on the gaskets/shims themselves.

Every time you add another or take away a head gasket/shim you are not only adjusting compression ratio (as you and others have noted) you are also changing many other variables - squish band thickness and plug depth to name two. In our small engines and for our use of sport flying it is one of the simpler ways to make these engines a bit more useable. My goal when I started this testing wasn't to get the ultimate in performance but rather to learn and to dispell some of the old wives tales.

cheers,Graham

GrahamC

Yes, much like the "peep hole" style of plug and head. Irecall that Norvel made an adapter button for their engines like this - Ihad one in my hands for a while but never tried it, Itraded it with a bunch of other stuff some time ago. I may try and make one or somthing similar to try.

Thought of trying that too. It is always easy to try these sorts of things when you have the facilities to make the parts but for the average flyer it doesn't have much interest. Besides, after some thought Idecided it wasn' t worth the time and effort what with Turbo plugs being commonly available even if they were a bit more costly.

Yes indeed, simply swapping in or out head gaskets/shims not only changes the compression ratio but several other variables as well. This is a very complex subject and I am afraid that my grasp of the subject is rather small. We tend to greatly simplify - this is only hobby after all and all we generally want to do is go flying, no fuss, no muss, no bother. Off the self engines, plugs, props and fuel are the order of the day for most. If you want to get that last bit out of these engines you have need to do the testing and test some more. Which begs the question - what do yo consider performance? Turn a small diameter high pitch prop very fast? Turn a larger diameter prop not so fast? AndyW rates throttle response and idling above all else (almost) Combatpig and others want speed. They all impose different requirements on the engine - load (prop), fuel, density altitude, what power band do you want to run in low, mid, high? Compression ratio, plug depth, combustion chamber shape, squish band width, squish band thickness, all are variables and all have an impact. I am going to go back and do some sum's on my measuresment with regards to calculating compression ratios (and effective compression ratios) to see where some of these combinations of heads and shims fit into the accepted norms for fuels that we use.

An interesting subject to some and quite boring for others. To each his (or her) own. We need each to pick our spot (desired performance) and test fuel, props, plugs to get as close to that as we can.

Interesting idea. I am not sure it required however but something to keep in mind.

Iam familiar with the technique. In fact one of my first attempts was to try something similar. I wasn't able to keep a good seal between the plastic plate and the small heads, clamp slipped, leaked - made a mess more than once. While not perfect, I do it without and make an effort to be as consistent as possible between measurements, hence the measure seven times, throw away the high and low, then average and round the remaining five.

cheers, Graham

iskandar taib

My Feedback: (5)

I have a few pre-Norvel AMEs that have these heads.The main problem with them was that glow plug elements are welded to the bottom of the plug, and this means when you tighten the plug, the end of the element will gouge into the seat at the bottom. Ugh.

Iskandar

GrahamC

Yes indeed that is a problem and one I recognized early on. I think it was an early attempt to "optimize" head/combustion chamber/plug etc and quite likely the grandfather of the idea of the Nelson and Turbo plugs.

I have picked up three of the new Merlin Norvel type plugs put haven't had the time to test them. Some others have posted a few comments but as of yet Ihave not seen anything negative. My first impression is that they are well made and fit quite nicely.

The plugs have steel bodys rather than aluminum which is quite interesting. I read a comment someplace by someone with a lot of experience in such matters (Dale Kirn perhaps?) that platinum does not like or care for aluminum - reacts or somehow oxidizes (I can't remember the content of comment) which is why most manufacturers used steel bodies for their plugs - except Cox and Norvel. I have not be able to verify the comment but makes me wonder if the Merlin plugs are made of steel for that reason or for simplicity or ease of manufacture?

cheers, Graham in Ottawa Canada
\

iskandar taib

My Feedback: (5)

Actually, the Nelson plugs came first. Henry's been making these plugs for many, many years - they've been popular with the CL racing crowd, and Russian F2D engines have been using them since they first started appearing back in the late 80s.

Yeah, true. Because they were cylinder heads rather than plugs per se. There were others, though - Gilbert, Testors, etc.

Anyone have a look at Doug Galbreath's web site recently? He's making a .020 head (actually, he'll machine your burned out head) that takes the insert part of the Nelson "Glo-bee" plug.

http://www.the-printer.net/DookCat.html#coxconv

Also, Bernie from coxengines.ca has announced he'll be making .020 Cox heads.

Iskandar

Jaspur_x

My Feedback: (1)

I want to try the turbo flatcoils out on my black widow and teedee 049`s with the "new" teedee piston/cylinders,  has anyone else tried these configurations yet?
I`m going to place orders shortly, since the" new" piston/cylinders are available, its time to break out the carbed 049 and give it a revival run at the sky 

Mr Cox

I don't want to spoil your joy, but there are no new piston/cylinders.

There are only some modified surestart cylinders. The modification concistst of removing the slit and then trying to deburr the inside. Mine was so rough and sloppy in the lower part of the cylinder that I don't dare to run it.

There is more info [link=http://www.rcuniverse.com/forum/fb.asp?m=10492710]Here[/link]

Jim Thomerson

I have a TD 09 high compression head modified for Nelson plug by a friend of a friend. At peak, it is about 200 RPM better than the stock head and seems to be more consistent when flying maneuvers.

Mr Cox

What is a "turbo flatcoil" by the way, a turbo-plug, glowbee-plug or both?

SGC

Mr Cox, Merlin make flatcoil(glowbee style) in regular 1/4-32 #2016 #2016B, turbo #2017,#2017Band Nelson style #1125B,#1125C plugs, as well as the 1/2A insert with flat coil -#2019B,2019C
http://www.merlinglowplugs.com/Aircraft.html
Stewart

Andrew

Stewart

Do know if the Merlin NELSON style plug is a drop in replacement for the original NELSON plug (11/32 x 32)?

andrew

Mr Cox

Wow, I had completely missed flat coils in turbo plugs.
I didn't think there was any advantage to the flat coils anyway?

mylamo

My Feedback: (1)

My experience with Glow Bee pligs was not all
that good. Power seemed to be down on lower nitro ( less than 25% )
and not very consistent. With nitro content over 25% and two shims
they would do well and outlast the hi comp Cox heads. RPMs were
not as good as Cox heads.
Ralph

SGC

Andrew,
From my correspondence with Merlin, the Nelson style plugs are the same on the thread/taper as the original but has the same hex/top construction as a 1/4-32 plug so a regular glowdriver will fit them, I personally havent purchased there nelson plugs as of yet. Ive only got the 1 VA mk2 and still useing up the spare nelson plugs I bought from Larry.

iskandar taib

My Feedback: (5)

Yup, indeed it is. Nelson has retired, someone else is now making the engines. The flat-coil Nelson plug is no longer available, and at least some pylon racers have switched to the Merlin flat coil. Darrol Cady sells them on his web site, Dub Jett ships them with his engines.

I should get a few to try.

Incidentally, check this out:

http://www.freepatentsonline.com/7205506.pdf

Do you think it'd fly???

Iskandar

Rubbernecker

My Feedback: (22)

I know this thread is a little old, but if I use more than 2 gaskets on a cox .049 with the Galbreath head, I cannot keep it tight. After every run the head is loose. Not the plug but the insert. Any ideas on how to fix this.

John

Mr Cox

Try with tightening the head when the engine is hot.

iskandar taib

My Feedback: (5)

The pylon racing people used them by the thousands. I was told the flat coil Nelson plugs would give a few hundred RPM more than the HD (vertical coil) plug in a F3D engine.

For some reason, they never caught on with F2D fliers, though. I wanted to try some, but they're not made any more. I have some Merlins coming, though.

You can still get Nelson flat coil rewinds from Russia, though:

http://www.rusengines.ru/prc.php?lan...7.67&EUR=39.51

Not cheap. And they call them "suppositories".

Iskandar

Larry Driskill

Hello all. (When reading my posts please remember that I sell Nelson plugs, believe them to be a great value and pretty much the long time benchmark for durable, high performance glow plugs.)

That said . . . Iskandar, I had not heard the rumor that Nelson was not making flat coil plugs anymore. I have them in stock and was quickly supplied by Nelson the last time I ordered.

So I wrote Henry Nelson and inquired. He immediately wrote back saying, "Not true". And he has lots of the bodies needed to make the plugs.

Thus, while there are more choices in plugs than a few years ago, the Nelsons are still the first pick of both many competitors and value conscious sport pilots.

iskandar taib

My Feedback: (5)

Hi Larry

I should have checked with Henry, I suppose. I was going by Dave Shadel's web site:

http://www.pspec.com/details.asp?ProdID=37&category=

and what I could find on Darrol Cady's web site:

http://www.darrolcady.com/Accessorie...ght.htm#nelson

Glad to hear I can still get the Nelson Globee plugs. I'll go and order some.

Iskandar

P.S. For the rest of you guys.. Larry's website is here:

http://www.kittingittogether.com/