Cox Glow Comparison
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- Опубліковано 31 січ 2018
- I compare the standard Cox glow head to the Merlin 2019 1/2A, and glow adapter with an OS #8 plug. Omega 25% nitro fuel with added castor was used along with an APC 5x3 prop.
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My theory on why the glow plug adapter doesn't work very well is chamber volume. The internal volume of the OS 8 glow plug is so high that it poses a SIGNIFICANT reduction in compression, which in turn murders top end. I'd almost bet that if you machined the adapter to be much flatter and ran the thinnest head shims you could you might be able to get hte adapter and OS 8 to run half decent.
One thing I did notice, though, is that the OS 8 was the most *stable* plug on test. Just goes to prove my theory on those things, which is basically 'Any glow engine will run on an OS 8 no matter how big or how small*.
Once again a good case for an analogue tachometer.
Very good stuff Dave. I bet two or three of them running simultaneously on your 2x4 would sound really neat!
I actually considered doing that. Perhaps some day.
You need to try that by adding head shims. that merlin might be over compressed and not at peak rpm . dont know. I would try head shims to get teh most rpm out of each
I am not familiar with Merlin either. Just doing a google search on them and they seem similar in design to the plugs I use.
coxengines.ca/cox-.049-glow-plug-adapter-insert-style.html
From the experience with the above plug, the compression question is a valid one. How many head shims did you run with on that test? I use two shims with 10%. It would not surprise me if it needs a lot of shims for high nitro. At my nitro levels, the above plug does out perform the standard glow head by a few hundred rpm on reed valve motors. I have seen over 1000 rpm on my Tee Dees from this plug. Maybe we have different heat ranges.
I agree that adapter for the OS 8 sux. If you put that motor on a 2 meter motor glider, you should have a problem on your hands. The stock BW is adequate to pull an old school 2m sail plane to thermal altitude. Losing 2000 rpm is a real deal killer. You would be lucky to sustain altitude out of a hand launch.
Merlin Plugs are made in Chicago by my friend Aldon Kelly , one at a time by hand. If you ever want instructions on glow plug operations give him a call.
@@jeffie8696 I understand that this is a 6 year old thread but today got a merlin plug and test it already on a single port engine and I was amazed. Do you know if those are still available since the maker is a friend of yours?
1300 rpm is about the norm for a golden bee. Someone correct me if I’m wrong. I don’t have a tach, just from videos I’ve seen
i was wondering why the dragonfly didnt have a muffler when i noticed the old style thin wall cylinder. was that cylinder on the dragonfly put on by you or did you get it like that because i have only seen those types of cylinders on older babe bee and teedee engines (50s to 60s).
forgot to say good video btw
What about same test with bigger props ? Like 7x4 ?
Those engines are long gone. That is a six year old video for crying out loud.
Merlin makes good plugs.
Where do the Merlin plugs come from? I've never heard of them.
I bought mine from eBay, but here is the website. www.merlinglowplugs.biz/main_page.html
That's good to know.
@@dmrcflyr2 Not anymore!