Forrest Edwards radial 5

[petertha]

I have every copy of this magazine and will probably not use most of the plans. Is it breaking any laws/rules for me to sell these plans to others? I did buy them in the first instance. Jack

If you look on the inside front cover page of SIC magazine I think it spells out the rights reserved aspect. I cant say that the plans show this or if so, consistently over the years. I didnt check very exhaustivley, just grabbed a few off the shelf. I think you could sell your magazine which includes the plans. I guess you could sell your plans removed from the magazine. Don't really think its right to copy the plans & sell them, legally or morally.

 

[josodl1953]

Gentlemen,
May I remind you that this thread is about building the Edwards Radial 5. Questions, remarks and discussions not concerning this engine or parts thereof should be posted in another thread.

Thank you for your consideration.

Jos

 

[Letsflyj3]

Interesting stuff. However, I had the lead already available and it worked for me.

I did the exhaust tubes too, was a lot easier with only one bend.
Finishing and polishing them took most of the time...

JosView attachment 109054

Hi Jos WHere did you get th eplans for the Radial engine your work looks great. Thanks in advance for the info.

 

[josodl1953]

Hi Letsfly,
I downloaded the plans from the internet, they were free at the time ( 2016). They come as aPDF file. Just google"Forest Edwards Radial 5" and the file should pop up somewhere. I converted mine to metric and reduced to 80% of the original , with some modifications, See the start of this thread.

If you can't find them I can post the original file here.

Jos

 

[josodl1953]

Last parts to be machined of this build were the piston rings. I followed the directions of the drawing being:
- turning a tube with the approximate dimensions of the rings
- milling a slot over the full length of the tube
- clamping in the chuck till the slot is closed
- turning final diameters
- parting off
I found that it is necessary to have the part outside the chuck should be as short as possible otherwise the slot will not be fully closed. In my case this was approximately 6 mm. The width of the parting tool and the ring both being 1 mm, I could make 3 rings in one go.

The drawing recommended the use of a parting cap placed over the ring to be parted off. I made one with bearings and a shaft to be fitted in the tailstock because I was fraid the the ring and cap would fly off after parting. Now it stays put when it becomes loose.

With this help, parting off was a piece of cake.

There were - of course - a few issues . The inner diameter was initially too big but I went on, just for practice.
So, with corrected ID I went on to find out that the thickness was 0,1 mm undersize. So I made the following ones slightly oversize, to be ground to the correct dimension when fitting them to the pistons.

 

[tornitore45]

I suppose the 1/2 hole threaded was in the original junk box piece used to make the cap.
What is keeping the cap from backing off? Does it stay put just by friction?

 

[josodl1953]

Yes Mauro, that's right. It was an old cover of a rejected pneumatic cylinder. By accident, the 1/2 hole came in really handy for removing the ring from the cap. The bearings have a strong fit on the shaft so no additional fixings are needed to prevent it from backing off.

So this is the result of 2,5 years of work, not hard work, just work..

Jos

 

[tornitore45]

Very close to making some noise!

 

[dethrow55]

tomitore 45 i see your in austin tx im here in el paso. many years ago i worked on mopac loop 1 austin. beautiful town

 

[josodl1953]

On assembly I foud that the roundness of the piston rings was .. well... less than satisfactory. So I made s set with a slight ( 0,2 mm ) oversize and machined the final OD on a mandrel. This gave better results but there were still a few that were not good, but it seems a common problem with home made piston rings: a fair amount does not meet the requirements. If you need 10 pieces, make 20...

Jos

 

[josodl1953]

After final assembly I spent the past weeks building the glow plug control panel. For 5 plugs one needs about 15 amps which is more than

the the average starting battery can provide . Luckily I had two of them , one of 9.5 Ah and one of 10,5 Ah so if I put them parallel they should be up to the job. I made switches for each individual plug, together with an ammeter so I could tets each plug without taking it off the engine.

A test with 5 plugs in a test fixture proved satisfactory.

With temperatures in the Netherlands now soaring above 30 degrees Celcius I think I'll postpone the final installation till the temperatures drop a little......

Taking it easy now......

Jos

 

[tornitore45]

Good idea about the ability to know each plug is good. I am not to that point yet but will experiment with looping the wire a few turns and use a hall effect sensor to turn an LED.
Nothing wrong with switches and Ampmeter but I like to see 5 LED in a pentagonal pattern.
Another idea I was bouncing around was to use a 6V battery and PWM control to adjest the voltage as the battery change. Rather than long wires I plan to make a ring held by the display stand feeding each plug from it. My engine will live on the display stand not on an airplane. Currently on extended vacation away from the shop, will resume in the fall.

 

[gunner312]

I just printed out a copy of the Edwards 5 drawings. I'm wondering, I have 7 pages and they seem to be incomplete, such as not raw materials list. It looks like a fairly difficult project but not unsurmountable. Any suggestions on the build?

 

[petertha]

The PDF drawings I downloaded some time ago, maybe year 2014? [A08a] are 40 pages in total. They are not dated so I cant tell you if there have been other revisions.

 

[petertha]

There are newer type single glow plug igniters like this one.
https://hobbyking.com/en_us/hobbykingr-6-24v-lipoly-glow-plug-igniter.html?___store=en_us
It must use something like a voltage regulator because it allows for a wide range of elevated input voltage (6-24v) yet delivers at requisite glow plug voltage & current draw. This would be a perfect match for common, inexpensive RC Lipo/LiFe cells which can deliver substantial current, no problem. The issue is one would have to get X number of these for multi-cylinder engines. Or figure out what the circuitry is doing. I have a feeling this is what some of the home made boards are doing. Going to have to cross this bridge myself one day.

 

[tornitore45]

Peter the device on the link you posted would work in principle but is not practical. I can see a problem with 5 of these sticking out around the engine and having to remove them behind a 20" propeller. I like the idea to have a single point of connect/disconnect fairly distant from the propeller even considering that I do not plan to mount it on a model airplane.
The ideal approach I am thinking is to use a 12V lead acid battery and a 5 phases PWM.
2/12 = 16% 5x16%= 80% therefore the battery is delivering nearly DC current at 3A
A quick calculation shows Five 10 uH inductors, MOSFET and Shottky diodes plus some small stuff for control should do it.

 

[petertha]

Hi Mauro. I agree. I was just referring to circuit board / regulator aspect, not the big spring clip connector. That connector is just conventionally used for temporary starting, then removed for flight. Its actually extra long to recah inside cowlings etc. There are much neater miniature connections that just clip onto the glow plug stem, easily home made. I know I have seen public domain glow plug igniter circuits for multi-cylinder engines, just don't have my links handy. Look forward to what you come up with. My point in mentioning the LiPo battery is they are very compact, high energy density & have no issues delivering at high current. Even a low grade these days might be 25C, so for example 2500 maH pack could deliver 25 * 2.5 = 62 amps continuous. We would never need that of course. I know some of the mini gel cell 12v batteries are getting better but generally they are comparatively low 'C' so you need larger capacity, which means a big bulky cell. But LiPo are different nominal voltage per cell (typically 3.7-4.0). So 1S = 4.0v, 2S = 8.0v etc. LiFe are a bit lower nominal per cell but still too much for glow plug voltage. So that's where I see the variable input / fixed output regulator type circuits as being useful. May well be what the PWM is behind the scenes. I'm electrically challenged For lithium batteries you also require the charger to go with it. Not a big cost these days but maybe not what you have. 12v is still such an ubiquitous standard.

 

[tornitore45]

Understand your point but I do not plan to be operational in the field so I have more options.
I used to design all sort of converter for a living. I do not relish electronic home projects because I am spoiled by the availability of industrial labs. But in this case I will give it a try.

 

[petertha]

7 cylinder driver, but its all Greek to me.
http://philsradial.blogspot.com/2013/02/glowplug-driver.html

Probably we should let Jos get back to work with his method. I know this has been discussed before on HMEM. Its kind of begging for a dedicated post.

 

[josodl1953]

On the parts and notes list of the Edwards it is stated that an onboard battery is recommended. I assume this applies to idling and low revving . When this engine eventually ends up on the nose of an R/C plane the electronic devices as suggested by you might come in handy. For the time being, the two 2Volt lead-acid batteries seem to be up to the job.

Jos