Building the 1/4-Scale 5 HP Red Wing: Part V

By Staff
1 / 10
2 / 10
The finished bushing.
3 / 10
The completed mixer
4 / 10
The mixer, as cast, in two pieces: The main body and what will soon be the bushing.
5 / 10
Arrow pointing to the 45-degree-tapered valve seat.
6 / 10
Arrow pointing to the hole leading to the needle valve.
7 / 10
Here you can see the mixer installed on the cylinder head.
8 / 10
This illustration shows where the two passages must intersect with each other.
9 / 10
Note position of the ignition stud, barely making contact with the timer.
10 / 10
The completed 1/4-scale Red Wing!

Editor’s note: This is the fifth and final installment on
building the Red Wing engine.

Hello again! This is the last part of the Red
Wing series. I have received several e-mails and even a letter
commenting on this series. It’s wonderful that something published
in a magazine is actually appreciated by the readers. Thanks for
reading!

Everything was finished in the last article except for the mixer
and how to hook up the wires. We are going to cover both in this
article! To finish off the mechanical components, lets hit the
mixer first.

Step 16: Constructing the Mixer

The mixer was the most difficult part of the engine according to
several of our readers. I still think the head was the toughest.
However, the mixer is tricky if you don’t pay close attention to
the blueprints. Let me cover the highlights of the mixer and you
can decide for yourself.

The mixer starts out as two brass castings (Photo 1). The top
portion I will refer to as the bushing and the main casting. There
is a trick to getting all of this aligned perfectly.

The bushing is the first part I worked with. I used a 1-inch
belt sander to remove the rough stuff from the casting. Then I
chucked it on the lathe. With the head of the bushing in the chuck,
I was able to turn the stub to a perfect 1/2-inch.

Next, I drilled a hole in its center so I could thread it for
8-inch pipe thread. This would be the connection between the mixer
and the head. It would also allow me to chuck the bushing in the
lathe’s tail stock for the threading process.

While the bushing was still in the lathe, I chucked an 8-inch
pipe thread tap in the tail stock and manually turned the lathe
while feeding the tap. This allowed me to get a perfectly aligned
thread before I started the next process.

To thread the stub, I put the die into the chuck of the lathe.
Next, I put the bushing on an 8-inch pipe and chucked the pipe into
the tail stock. It was very easy to manually turn the lathe while
pushing the bushing into the die from the tail stock holder. So far
this has given me a perfectly-aligned pipe thread and 1/2-inch
thread for the bushing-to-mixer interface (Photo 2).

Now for the hard part: the mixer body itself. There is a stub on
the end of the mixer casting (see arrow in photo 1) so you can
chuck it into the lathe. This stub will get cut off later, so do
everything you can while the mixer casting is chucked in this
position.

Before we go any further, I want to show you the finished mixer
(Photo 3). I think it will help some of you understand how one part
of the mixer relates to the other parts.

The top part of the casting has to be turned and faced just to
clean it up a little. Next, an 8-inch hole is drilled from the top
of the mixer casting, into the first chamber, through the second
chamber and until it is well within the stem that is held by the
chuck. The portion of the hole that is in the stem will act as the
valve guide.

The passage between the first and second chamber inside the
mixer is enlarged to allow air to pass around the valve stem. The
bottom of this first chamber will be the seat for the valve (Photo
4). It should be tapered at a 45 degree angle according to the
prints.

If you take a look at photo 5, you will see a small hole in the
valve seat. That little hole is the passage from the mixing
chamber, down to the needle valve. Obviously the needle valve is
what controls how much fuel is sucked into the mixing chamber when
the engine is on the intake stroke. This little passage is drilled
with a tiny number 65 bit.

How does the fuel get from the fuel line over to the needle
valve? This will make the sweat bead on your forehead. You must
drill two small holes into the casting. The scary part is that
these two holes have to intersect with each other without breaking
into any of the chambers inside the casting (Photo 6). I followed
the angles and directions on the blueprints and had no
problems.

The valve has to be seated just like the valves in the head
were. The only difference is this time we are dealing with
brass-on-brass instead of steel-on-steel. The valve is held in
position by a spring and keeper as can be seen in photo 3.

I have to admit that I went the easy way on one part of the
mixer. The fuel line connection and needle valve are store bought.
However, I still had to modify the tip of the needle valve by
shortening it and changing it to a 15 degree angle. The main reason
I went with store bought parts was because I was running short on
time.

Step 17: Cam and Ignition Timing

With the mixer screwed into position (Photo 7), I am ready to
test-fire this bad boy! That is, as soon as I set the timing and
attach a few wires.

The flywheel turns clockwise when viewed from the governor side
of the engine. The timing has to be set first, so start with the
piston at top dead center. Now set the timing lever so it is
vertical. The ignition stud should just start to make contact with
the metal insert that is in the non-conductive material that turns
with the timing gear (Photo 8).

The way to adjust this is to slide the whole timing assembly off
the shaft, turn the timing gear and slide it back onto the shaft.
Fine tuning of the ignition timing can be done with the lever. Now
we can move on to the cam.

To set the cam, start turning the flywheel until you have gone
155 degrees. Sounds tough, but 180 minus 155 equals 25. Does 25
sound familiar? It should. Twenty-five degrees is the angle the
bearing base on the engine frame was milled. All you have to do is
set the throw of the crankshaft to the same angle as the mating
surface of the bearing base and bearing caps.

Now that everything is in the correct position, adjust the cam
so it is just starting to move the pushrod. Remember, the cam and
timing gear turn the opposite direction of the flywheels. You will
know if you set the cam on the correct side of the pushrod by
turning the flywheel a little further. If it is set correctly, the
pushrod will start to open the exhaust valve.

Step 18: Wiring and Firing

The only thing left is wiring. These things are so simple to
wire, it almost doesn’t need explaining, but I will hit on it just
the same. This little engine uses a buzz coil as its ignition
source. I didn’t know what to expect until I saw one. It is a very
simple device that would take another article to explain in detail.
However, all you have to know to get your engine going is where to
connect the three wires. It couldn’t be simpler.

One wire goes directly from the buzz coil to the spark plug. One
wire goes from the ignition stud to the buzz coil. The other
connection on the buzz coil goes to the positive side of the
battery. There are your three wires. One more wire is added from
the engine frame to the negative side of the battery to complete
the circuit.

With the needle valve turned in all the way and then backed off
just a little, I gave the engine a spin and nothing happened. I did
this a few more times and decided the engine needed to be broken in
a little before it would start.

I disconnected the battery, then chucked a 1/2-inch drill motor
to the crankshaft and gave the trigger a squeeze. I spun the engine
for about two minutes. I reconnected the battery and gave the
engine another spin. It fired up and ran for a good 10 or 15
seconds. A little tweaking with the needle valve and my little
engine is singing that familiar tune. Hit, miss, miss, miss, hit,
miss, miss, miss.

This is the most exciting project I have ever worked on. I have
spent many hours teaching myself how to use a mill and a lathe. I
took a box full of rough castings and turned them into a work of
art! Well, there are a few rough edges on my Red Wing, but it is a
work of art to me.

I am sure there are a lot of people that would love to feel the
satisfaction of having built something like this for yourself. I
just proved to you it can be done by anyone that has a little
common sense and is willing to spend the time to make it happen.
This was my first model, but I am sure it will not be my last!

Contact engine enthusiast Richard Allen Dickey at: 246 Skyview
Lane, Yellville, AR 72687; rad2001@leadhill.net
Contact the Red Wing Motor Co. at: (660) 428-2288;
www.modelengines.com

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