stunthanger.com
Building Tips and technical articles. => 1/2 A building. => Topic started by: Andrew Tinsley on June 16, 2015, 01:01:53 PM
-
Hello,
I have a Thermal Hopper and the head is stuck fast, before I give it the third degree, I believe that the glow heads used in the early Cox engines are different to the later heads. I would like to run this engine, so any tips of what can be converted? Does Doug Galbreath do a turbo conversion for this engine? Any help will be appreciated.
Andrew.
-
Soak it in fuel or alcohol overnight. After drying, heat it with a hair dryer or heat gun till the gunk starts bubbling out of the seam. The head should come right off at that point.
The HEAD to CYLINDER changed thread size at some point, but the CYLINDER to CASE did not. Swap cylinders to a modern set and realize more power from boost ports.
Phil
-
Hello Phil!
Now that is a smart piece of lateral thinking! A Bernie TD cylinder and a Galbreath head should see it turning over smartly!
Thanks,
Andrew.
-
Might want to swap the piston too. There might be one of those funny 3-piece jobs in there.
Phil
-
Yes, no point in just changing the cylinder. I don't have a problem getting the head off, just did not want to risk marking a rare Cox head that is still good!
Thanks again,
Andrew.
-
Hi Andrew,
But if you replace the cylinder, glowhead and piston with something more modern, it will no longer be a Thermal Hopper and you won't have the "Thermal Hopper Experience"!
Let me explain what the "Thermal Hopper Experience" is:
As a young lad in the 50s, my mate and I flew 1/2A airplanes powered by our trusty old OK Cubs. My mate's paper route supplied sufficient funds for him to buy a new engine... the just released Thermal Hopper. Yes, we read all the hype about this engine's performance but were skeptical.
We removed the Cub, installed the TH and went out to fly without even running the engine on a stand (the ads said it didn't need breaking in). Contrary to the oft cantankerous Cubs, the TH fired up right away which startled us but when the needle was turned in to a good 2-stoke, I knew I had a tiger in my hands... What a sound and what pull!
I launched the plane and it spun my mate around so fast that after the flight, he fell down... now that's performance and the TH Experience... you never forget it!
Orv.
Orv.
-
Hello Orv,
I would love to have the Thermal Hopper experience, but glowheads seem to be fabled and totally unobtainable, unless you have the odd one or two!
I remember reading about the Hopper when I had my first Aeromodeller engine encyclopedia. The outputs was by far the best of the 1/2A engines tested. I never expected to own one, but almost 60 years later and voila!
Anyone have any glowheads? Maybe I can make one from a standard Cox head, you never know your luck.
Andrew.
-
I have fired up the Hoper with some 25% glow mix and my goodness it really does cut the mustard, as we say this side of the pond. I am well impressed and to think that this was around almost 60 years ago. It must have upset the other 1/2A engine makers!
Well that is it, I am not going to burn out my one good glowhead, so it is high days and holidays only. Otherwise it will be a TD head and cylinder!
Thanks,
Andrew.
-
Which version of the Thermal Hopper do you have? The one with the bird cage mount or the version that mounts flat on the firewall which requires you to drill a hole to clear the carb? (David)
-
The "bird cage" was a separate accessory. The engine was never sold with it. Now a hard to get item!
-
Looks as if I am lucky, mine has the birdcage mount!
Andrew.