Forrest Edwards radial 5

[tornitore45]

The plugs should stay hot once the engine is revving but, as you say, is nice to have some form of assist to guarantee a slow idle.
It was an idle thought of mine back when I was flying to make a controller that kept the temperature constant by measuring the resistance of the plug when the PWM phase is off and closing the control loop on the sensed resistance.
Using a cold plug and artificially increasing the heat could possibly result is some form of advance control. The current required should be much lower that during starting. Most likely this is just idle dreaming.

 

[josodl1953]

So, with everything assembled, this is what it looks like:

The only thing that remains ... the all-important question... Does it run?

Yes, it does... watch the video on

Jos

 

[josodl1953]

Well, what next? Of course there are some loose ends to tidy up. Idling is not optimal, for the initial runs I used new old stock plugs I got from my brother with whom I was running R/C speedboats a long time ago , to save the expensive 4-stroke plugs during running-in. Also I will need a collector ring for the exhaust because now oil is all over the place, especially because I run the engine a bit on the rich side. And it may be worthwile to do a bit of research on electronic devices to provide low weight glow power.

So, it is not the end of the story but the most important milestone is reached.

Jos

 

[tornitore45]

Great sight. What prop are you using and what RPM you are getting? Granted that those values means little before break in.
What is the difference between 4 strokes plugs and 2 strokes plugs? 4 stroke should be hotter I suppose.

 

[aka9950202]

Weĺl done. Love your work.

Cheers,

Andrew in Melbourne

 

[propclock]

Fantastic! the only thing I would change is go spark and gas.
wonderful build post thanks for your efforts at sharing.

 

[Johno1958]

That engine purrs .
Cheers
John

 

[Tim1974]

Hay you got there I’ve been following this for so long what a inspiration well dun to you

 

[josodl1953]

EPILOGUE

Well, this build was a long and winding road for the past two-and-a-half year but it was worth the effort.
I hope that it encourages other " apprentice" home model engine machinists to build engines even if they do not posess fancy CNC equipment or even a mill. I made this engine only with a lathe, a drill press.. and some elbow steam. It takes a lot more time, ingenuity and perseverance if you have simple machines but hey, this is a hobby, take your time , have fun, and go for it.

I planned to go R/C flying with this engine but before doing so it has to prove its airworthyness with respect to power, longevity and reliable throttling. Eventually it should fly a Boeing Stearman.

It should look like this

About future engine projects, I have been thinking about an Erwards Radial 9 . There are some interesting differences
between a radial 5 and a radial 9, apart from the number of cylinders of course. The camring of the 9 has double the amount of cam lobes (8) compared to the 5 (4). Also the camring of the 9 turns at half the speed of the 5.

I think the main dimensions of the cam housing can stay the same, probably a bigger OD of the crankcase will be needed to get enough room for 9 cylinders.

Of course there will be ready-to-go designs for model radial 9's but this engine would be easier for me because I could use a lot of tooling as used for the radial 5.

This is, however, is a project for the distant future. I find a flat four more appropriate as a next project.
Using the cylinder and head design of the Edwards, I came up with this.

It has a vertically split crankcase, a built-up crankshaft running in 3 ballbearings. One of the crankwebs in the middle is clamped to the middle section of the crankshaft to enable fitting of the middle ball bearing. The camshaft is fitted in a cam housing bolted on the bottom of the crankcase and driven by gears at the backside of the engine, just like my flat twin (see avatar). Now this is a preliminary design so do't expect a thread on this engine before next year.....

If you have any questions just PM me and above all... keep the chips flying!


Jos

 

[josodl1953]

Mauro, I forgot to answer your question about prop and RPM. The recommended prop for the full size Edwards is a 22-8 or 20-10 at about 6000-7000 rpm. I chose a 18-10 for my downsized version. I was so overwhelmed by the fact that the engine started right the first time that I forgot to take RPM readings. I let you know as soon as I have done the next test run.

Jos

 

[WOB]

There is no need to separate the flat-four opposing con rods by a crank web. They can live side by side on the same journal as is common on auto engines. Makes a shorter, simpler crankshaft and a shorter engine. If you make the center bearing a split bronze sleeve, you can have a one piece crank which is always better. Also no need to have a split crankcase. You can do it with a rear removable plate only so a total of 2 pieces for the complete crank case.

This engine illustrates what I'm saying. It's a 4-stroke glow ignition with 1"cylinder bores. Turns an 18-10 Zinger at 7200 RPM. It is a 2X scale-up 0f this engine originally published in "Strictly IC" magazine: http://www.strictlyic.com/ser01.htm

PEEWIT, by Eric Whittle
A 5.5cc, Horizontally-Opposed, 4-Cylinder, 4-Stroke, 15oz, 3 ¾ " long, 3" wide,
Air Cooled, Glow Ignition Aero Engine. 10" X 6" prop at 8,000 RPM’s.
Issues: # 57, 58, 59, 60 & 61.....$8.00ea.....TOTAL: $40.00

WOB

 

[josodl1953]

As far as I know boxer engines always have crankpins separated 180 degrees for each set of opposed cylinders (BMW, Beetle, Honda Goldwing). Is there a cross-section of this engine?

Jos

 

[tornitore45]

WOB, I suppose the PEEWIT is a 5.5cc per cylinder totaling 22 cc. Right?
It may be the next engine I build.

 

[WOB]

WOB, I suppose the PEEWIT is a 5.5cc per cylinder totaling 22 cc. Right?
It may be the next engine I build.

No, it was a total of 5.5 CC . The original engine as published had 1/2" bores. It was too small for my taste. I upscaled it 2X get 1" bores, This made the new displacement 44 CC. Easier to build and swings a good size prop with authority. If you build it 2X, it looks a lot like and sounds just like this:

WOB

 

[WOB]

As far as I know boxer engines always have crankpins separated 180 degrees for each set of opposed cylinders (BMW, Beetle, Honda Goldwing). Is there a cross-section of this engine?

Jos

You are right, of course. Don't know what I was thinking. In my defense, it has been 20 years since I built the engine.

The connecting rod little ends on this engine are offset slightly to allow the cylinder bores to be a little closer together than normal. This partially compensates for the crank web thickness between journals Sorry, I no longer have a copy of the magazine engine articles.

WOB

 

[tornitore45]

I love the stand and the starter. I would make it a 2X as well.
I am curious where did you insert the one way clutch for the starter? I would not want to see the big gear spinning after starting.

 

[WOB]

That is not my engine. I was just trying to show that the 2X PEEWIT is similar to the commercial OS FF-320 and that video popped-up when I searched for OS FF-320. I probably should have posted this: https://www.towerhobbies.com/cgi-bin/wti0001p?&I=LXBY71
Sorry for the mix-up.

WOB

 

[WOB]

Regarding a possible electric starter for the Peewitt, it would be easy to extend the crankshaft through the timing gear housing on the back end of the motor. You could even use the cam shaft instead and the 2:1 gear reduction built in. Then it would be easy to add the starter motor and over-running clutch concealed behind the motor mount backplate.

WOB

 

[tornitore45]

Yap, that is the best way to do it.

 

[petertha]

Excellent runner Jos! Congrats for your hard work & perseverance.
What is your fuel of choice right now? (like commercial RC fuel containing oil, or homebrew methanol/nitro no oil,,?)
How is the lubrication pump system working? No issues?

I'm confused by your Edwards-9 radial & Edwards flat-4. Do you mean using the same Edwards-5 cylinder components but essentially layout assembly of your own design?