Glow plug tests on Wen Mac/Testors-McCoy engines

[fred krueger]

Last Summer, Bill Smith and I started working with Wen Mac engines (probably as a flashback to our youth!).  Bill is using a Mk II to power a Firebaby replica.
I started working with the later 'Hot Shot' versions and have a selection of Mk XII through Testors-McCoy.  The glow heads are not easy to find, and I use Merlin drop-in plugs almost exclusively in my Cox and Norvel engines, so I thought I would make a head clamp for the Wen Mac and compare the Merlin plug against the 2 generations of Wen Mac glow heads in my stock.
The tests were conducted with a Cox 6x3 prop and Sig 15% Champion fuel.  Other folks have done similar tests with smaller props, so they recorded higher rpm.  I recorded a max of 14,700 rpm using a Merlin plug.  That's not bad swinging a 6x3 prop
Fred


  

[Andrew Tinsley]

Fascinating Fred!
A very nice bit of work if I may say so. You can do a lot of good work with a lathe, I think everyone should have one. Even the cheap little Emcos can cope with this type of work and I am sure there are some even cheaper Chinese clones around!
I always thought that the little Testor McCoys and Wen Macs were a heap of rubbish until I accidently acquired one in a group of engines I purchased as a job lot. I was very pleasantly surprised how good it was. I now have several and I intended to do either a turbo plug conversion or a Merlin adapter. Seeing your very neat workmanship and the excellent results I think I will steal your idea!

Andrew.

[fred krueger]

Andrew,

Go for it!  Nothing more fun than playing with engines.  I also made a couple of conversion heads for standard glow plugs.  The old style makes a low compression head and the newer style makes a high compression head.  I need to document a test on those also (someday).

BTW, be careful when boring out the hole for the Merlin plug.  There is not a lot of material left underneath the top fin of the glow head.  Mine have a little slop and there is enough material so that you can tighten the finished clamp with no problems.

Fred

[YakNine]

I have been playing with a few Wen Mac's lately. I am making a coroplast beginners ringmaster for the flyathon and am going to use a glow head engine , I am putting together a Pee Wee Pup with my daughter and plan on using an older short glow plug engine on that one not as powerful but I like how they run better. T.J.

[GGeezer]

Hi Fred,
Which Merlin drop in plugs do you use? The company's website lists the following:
    GloBee™ Drop-In: HOT
    GoBee™ Drop-In: MED
        GloBee™ 10

Orv.

[YakNine]

Hi Fred I noticed the prop drivers on your engines aren't stock , are these cox units and did you have to modify them ? Thanks T.J.

[fred krueger]

GGeezer,

The plug is a Merlin 2019.  It is specifically designed for 1/2A.  Merlin sells them individually or as a set of 3 with clamp ring for $15.  Unfortunately, the clamp ring fits Cox and Norvel cylinders.  My video shows the machining of a Wen Mac glow head into a clamp ring to use with the Wen Macs.

YakNine,
The drive plates are made from Cox units.  I removed the spring starters to save weight and the Wen Macs start pretty easily by hand.  If you want to use an electric starter (I do sometimes), buy the brass drive plates (Cox International in Canada) and you won't do heavy wear on the front end when using an electric starter.  The drive plates must be drilled out slightly for the Wen Mac crankshaft.  I don't remember the drill size off the top of my head.  Drill them slightly undersize and the spines cut into the drive plate when they are assembled.

Fred

[Andrew Tinsley]

Hello Fred,
At the risk of sounding very stupid, how did you get the starter spring unit off? It looked as though it might be a press fit, but I wasn't too sure, so I didn't use a puller for risk of breaking it! I must admit that I looked at the set up for a long time and just didn't have the nerve to try getting it off. For some stupid reason, I hate the thought of damaging something unnecessarily. Must be something to do with post war austerity upbringing ......... never waste anything (even though it may be redundant!)

Andrew.

[fred krueger]

Andrew,
The steel drive plate is splined, just like a Cox, except Cox uses aluminum or brass.
Remove the backplate and the head.  Unhook the con rod from the crankpin and push the piston out the top.  You should not have to unscrew the cylinder.  Screw a prop nut partially on to the crankshaft.  Place the rear of the crankcase  on a flat piece of hardwood.  Make sure only the crankcase back is touching the wood surface or you'll break the crankcase.  Hold the crankcase firmly against the wood surface and tap the end of the crankshaft until the drive plate separates.  Remove the drive plate and starter spring.  Use a Dremel to grind off the rivets, then pry off the spring housing.  Purchase a Cox drive plate and open it up slightly (I don't remember how much...measure it and drill slightly under size to allow for spline cutting).
Good luck.

[GGeezer]

Thanks for the plug info Fred.

Orv.

[Andrew Tinsley]

Hello Fred,
Thanks for the info on the Wen Macs. I shall attack the starter spring and housing with confidence. The Brass 0.049 reedy drive plates are on order"

Thanks,

Again,

Andrew.