Merlin inserts?

944_Jim wrote:Bernie,
Ouch! I hate when a deal goes bad too. I didn't mean to peel a scab there. I understand not wanting to deal with particular vendors. There is a Porsche parts vendor outside of Atlanta I will never deal with ever since 1995...expensive part not as described despite phone calls to that vendor for his word that the part was, well, as described. I actually drove to the vendor for the return of the mail order part, yet he held the $$ for a month before issuing the refund.

Just out of curiosity, what size is the plug hole in the clamp? I didn't think to bring my son's Merlin-equipped Scientific FW-190 home from work today (wall art at work for now). Tomorrow I will, so I can make a quick spreadsheet between Merlin, Norvel and AP clamps/inserts...including the Norvel .049 and .061 clamps.

I'm thinking out loud here without having my Merlin clamp handy...but I wonder what it would take to make a plug adapter that your clamp would secure in a Cox engine.
I know "the other guy" (not EXEngines to avoid ambiguity) sells a plug adapter for the Norvel .074 that is held onto the block with the oem clamp. But this means a clamp, adapter and plug...three parts instead of only two.

The hole is 8.61mm (0.339")

I didn't think I would stir up a big conversation. Loads of good information.
I need to go through all my small glow gear and do an inventory of sorts.
I will be ordering some parts!

944_Jim wrote: Nothing on the .074, except concept, fits any of the .061-.049 engines.

I get your point, but that isn't exactly true...

If I remember correctly the head clamp from the Norvel .074 actually fits the VA .049 mkII engine.

Well, just a slight deviation from the Merlin conversation, does anyone know what options I might have for a replacement insert to suit a K&B Torp Jr .035?  Same concept as the Merlin/Norvel design only smaller.  While I don't plan on flying it, my Torp Jr will only run with the battery connected.  It would be nice to have it right.  Not sure if there's enough "meat" on the Norvel type plugs to turn one down to fit.

Ok...Busy slide, but it has all the numbers.
Key notes:
Mix and match whatever you want between the Cox, Merlin and Norvels. Whatch for the "unique".combinations; the Norvel .061 clamp on the lowly Cox reedies, and the Cox glowhead on the Norvel .061. The Cox head doesn't look too far out of place on the AP .061 because the AP is a thinner profile engine than the Norvel .061.
The AP clamp fits only the AP. Oddly, all other heads/clamps will screw into the AP engine without force.
The Norvel engines appear to use the same glowplug. That same glowplug is an extremely close match with the Merlin.
The AP glowplug will fit the other engines. The flange is thicker, so the "other" clamp will ride higher in the cylinder threads.

At one of our combat contests, I had the pleasure of flying Henry Nelson. Afterwards, I initiated a conversation with him as I was interested in a specific head he was making for a particular engine. Unfortunately, he did this as a experiment and had no plans on producing more. He did offer me some unfinished blanks if I was interested. He mentioned that no one in particular could offer a plug like his for the price and quality he offers and he intentionally did that. It was all in the machining of the plug. That was over 6 years ago and that statement is still holding true.

I've never had a AP plug insert last, I liked them but they have a very short lifespan. I only know of one source for the AP inserts now and one plug is the cost of 2 Nelson plugs. As for Merlin, I found the red Merlin inserts to be too hot causing pre ignition on start up. I spoke to Al Kelly in regards to this. While I used his advice to sort out issues, they just didn't work for me. Higher nitro made problems worse and it becomes very expensive.When your engine is taking out plugs to the point where that cost outweighs the engine, it's time to shelf it. When flying combat, time is important and if the plane goes down, airtime is lost so getting up and running is the key, Merlin plugs didn't work for me in that environment. Nelson plugs outlast all of them not too mention can be purchased for $5.

Thanks to all for the replies.

I am trying to simplify the information, so….
This is what I have been able to glean from the thread….

Cox heads on work on Cox .049 & .051, Norvel .061, AP .061 with head gasket adjustments.

Merlin Clamps and inserts work on Cox .049 & .051, Norvel .061, AP .061 with head gasket adjustments under the clamp.

AP clamps and inserts work on Cox .049 & .051CORRECTED, Norvel .061, AP .061 with head gasket adjustments under the clamp.

Kamtechnik adapters work with all COX .049/.051 and Norvel .051/.061 using the tapered bottom TURBO style plugs with head gasket adjustments under the adapter.

Nelson heads and glow plugs work for Cox .049-.051 and Norvel .049-.061.


Cox heads are available from Cox International and some other hobby shop websites.
Kamtechnik adapters are available from Kamtechnik website.
Nelson head and glow plugs available from Galbreath website. CORRECTED
AP clamps and glow plugs available from Hobby Club website.


It appears that Cox, Norvel, and AP parts are all within a few hundredths of a millimeter of each other! Thank you Jim for the visual aid!

Cox heads for .020, .09, and .15, and also for Norvel .074, will be in production soon from Greg.
Some Merlin clamps are still available from Bernie at Cox.

I apologize for not being in the loop, but most of you seem to be on a first name basis, so I need to ask, who are the makers/sellers of the parts?  The only one I recognize is Bernie from Cox Int.

Please feel free to correct anything I got wrong.

Norvel .061 with Merlin head.
Cox reedie with Norvel .061 head.

Aero wrote:Thanks to all for the replies.

I am trying to simplify the information, so….
AP clamps and inserts work on Cox .049 & .051, Norvel...

Please feel free to correct anything I got wrong.

Nope...only the glowplug.
I thought it was odd that all clamps/heads screwed into the AP, but not the other way around. The AP gets about two turns in the others before binding. I wasn't going to waste a part to see just how much force/deformation it would take to seat the glowplug in another manufacturer's engine..
Not only that, but the other guys' plugs wouldn't fit the hole in the AP clamp.

Duplicate...Mods, feel free to delete. Thx.

I did all this documenting to see if a glowplug can be machined to accept a plain-jane or Turbo plug.
Or, is there enough meat left to re-machine the Cox International clamp to take a generic plug/turbo plug?

Hopefully, I will have time to look closer at the Merlin/Norvel clamp and a spare glowplug tonight. I expect the Cox clamp to be very similar with the same re-work.

Nelson style large base and 3/8 "hex are not going anywhere for a long time...many Europe, and eastern Europe speed, racing, boat, Free flight, and combat engines have designed the head for the Nelson plug
Many DubbJett engines used that plug and for a while Dubb got Merlin to make plugs with the Nelson Seat on standard thread diameter, 1/4" hex....sadly they are all sold

Also sadly Doug Galbreath no longer sells anything

And for what it is worth...many pilots that use Nelson plugs by them in quantity. On race day use a new plug every-race/or heat, many combat pilots have from 1 to 30 planes and engines with them for a long weekend contest with a bunch of new plugs on a speed caddy

not unusual to see a pit box with many new plugs and a bag or jar of used but good plugs..popped plugs are left in the pit grass as a joke for the metal detecting guys who zoom around after a contest....grin

Here is my understanding of the Norvel and AP development (for what it's worth).

The AP engines are clones of the very early Norvel engines, right down to the smaller and colder original Norvel type plugs.

Norvel realized their early small plugs were too cold and released the newer larger dia plugs and clamps that are a little too hot and caused some overheating when run at max rpms. Their solution was the Rev-lite cylinders and heads for better cooling.

The Nelson heads and clamps were designed for Free Flight and Speed contestants prior to the Norvel engine release and were just about spot on for that and all Norvel engines as well.

The very early Norvel plugs and engines have just about been forgotten, but are still around.

Norvel engines with the early adhesive mounted venturi are likely to have the small plugs, but there is only one way to be sure, check-it!

Bill

944_Jim wrote:I did all this documenting to see if a glowplug can be machined to accept a plain-jane or Turbo plug.
Or, is there enough meat left to re-machine the Cox International clamp to take a generic plug/turbo plug?

You can easily machine the stock Cox glow heads to take Turbo plugs. Works all the way from .15 down to the .020 engines. On the .020 it looks kind of strange, in terms of size, but it does work:

Surfer_kris wrote:

944_Jim wrote:I did all this documenting to see if a glowplug can be machined to accept a plain-jane or Turbo plug.
Or, is there enough meat left to re-machine the Cox International clamp to take a generic plug/turbo plug?

You can easily machine the stock Cox glow heads to take Turbo plugs. Works all the way from .15 down to the .020 engines. On the .020 it looks kind of strange, in terms of size, but it does work:

Can you show a bit of the process? Measurements? I have access to CNC lathe and mill.

Ok. So it looks like the Cox clamp and replacement plugs can be modified to use Turbo plugs. I know...just pony up and buy a Turbo head for the engines. But this gives my Norvel .061 clamp (big) something to do. For the little ones, I'll have to reconsider.
https://www.rcuniverse.com/forum/1-2-1-8-airplanes-70/4533758-turbo-plugs-how.html#post4533758