lukesp

I have some after market heads to suit Cox 1/2A's floating around that I would like to ID. I'm sure I know what they are but can't for the life of me remember.
In the first pic the order is standard Cox, Hi comp Cox, Dynamic diecast, and the unknown plug.

The second pic shows the unknown plug with "W"shaped element beside the Dynamic plug, and the third pic's order is unknown, Dynamic, Hi comp and std Cox

Big Al-RCU

LUKESP,
The 'W' shaped element is an early Cox head. I just did a quick check on a couple of engines that both have that head. Both are 30+ years old. One was on a QZ that came originaly on one of the early PT-19's. (Before they started to use plastic backplate product engines on them.) The other was on a product engine that (I'm pretty sure) came on a later plastic plane called the 'Bushmaster'.
I'm not aware of any differences in performance between them and the current spiral coil heads. However, there probably was a reason for that configuration. Anyone know the background? They MUST have been robust, since these two are still good. Of course I don't know for certain that they are the original heads, but I think so, (I've had the engines since new).
Al Lenz

lukesp

Excellent Al, I took these heads ( four W elements) off some very old Babe Bees I had to do some rebuilding and I think you are right. I remember one I found some time ago (again on an old Thimble Drome babe Bee) and I threw it out because I thought the element had burned out. Rather stupid of me, but I was looking for the coil element at the time and saw this bent piece of wire instead. When I saw these four I realised my mistake.

That's what I love about RCU, always an answer. Thanks Al.

BTW, these W element heads are in fine working order too, I wonder (if they are indeed Cox heads) why they went away from them?

injunnut1

These are indeed Cox plugs ..... you will notice that Cox I.D.ed these glow plug heads with a machined 'ring' around the top fin. Dale Kirn once told me the story on these plugs, but I have forgotten it now. I believe at first Cox thought this plug was going to give an increase in performance, but when it proved out to be 'not the case' Cox went back to the coil element design exclusively ..... something like that as I recall? Back in the day a couple other manufacturers touted this 'W' element design in their engine ads, 'K&B Allen' Sky Fury plugs was one that comes to mind.

Donald Garry

Big Al-RCU

Thanks for the info Donald,
Yep mine all have the machined ring on the top which is clearly visible in LUKESP's first pic. If I had known that I wouldn't have had to undo the heads to check them!
Wonder if they were offered as replacements and if they had a unique part number?
Al

lukesp

Thanks Donald and Al for the info.

ffkiwi

Atwood also used the W-element form in some of their heads-I have a Shriek head with this form.