Model Engine Maker

Engines => Your Own Design => Topic started by: galland on September 08, 2018, 08:46:24 PM

Title: Another air powered (maybe) Radial engine
Post by: galland on September 08, 2018, 08:46:24 PM
A number of years back our EAA chapter was discussing radial engines and some of the guys had no clue how the crankshaft and connecting rods moved so I built a very small partial radial just for demonstration of that action. It was never meant to be a running model or even finished to look complete. The first 2 photos are of what is was. A couple of months back I got it out and wondered if it could be made to run. I had made it with screw on cylinders for simplicity and had put a hole through each cylinder between the first and 3rd fin at 90 degrees to the crankshaft pointing straight at the next cylinder. At the time I was picturing tiny exhaust pipes in those holes curving to the rear. Now I was saying that sure was a dumb idea because there is no room to get in there and do anything but each cylinder has a port in it in the wrong place. Any way I went to work thinking on how to change that and not make 9 new cylinders (I hate repetition. I will explain my fix later (any ideas out there). The other photo is some of my practice rear chambers where I checked to see if I had room to put flanges on like Dreeves and Bill did on their radials. I did not want to go smaller than 0-80 screws and with 9 cylinders I kept breaking through in to the next flange hole for the next cylinder until on the aluminum one I just made it but the chamber was larger than what I wanted for my engine so I decided to go another route. The fixture was so that I could screw on each cylinder and then rotate them to where I wanted for additional work.

     Gary
Title: Re: Another air powered (maybe) Radial engine
Post by: Ye-Ole Steam Dude on September 08, 2018, 09:47:23 PM
Hi Gary,

That is a beautiful piece of art / work.

Have a great day,
Thomas
Title: Re: Another air powered (maybe) Radial engine
Post by: b.lindsey on September 08, 2018, 09:56:42 PM
I hope you can finish it up and get it running Gary. Nine cylinders is a whole lot tougher than the five Dave and I did, and even then there wasn't much real estate to play with.

Bill
Title: Re: Another air powered (maybe) Radial engine
Post by: zeeprogrammer on September 08, 2018, 10:15:43 PM
I just noticed the dime. Wow!  :o

Fantastic finishes too!
Title: Re: Another air powered (maybe) Radial engine
Post by: galland on September 09, 2018, 04:33:31 PM
After thinking on how I could go ahead and use the port holes I had already put in the cylinder/heads I came up with a solution. Unscrewing the cylinders would bring the ports back towards the rear of the engine so I started playing with gaskets to go between the cylinder and crankcase. Using a carbide scriber in the lathe and putting various thicknesses of paper and Teflon on a mini faceplate I found I could cut out good gaskets. The 9 in the one photo are .010 thick Teflon sheet. That got my ports pointing about 45 degrees to the right of center when viewing from the back. I found some .0085 thick paper and those got me about 45 degrees to the left of center. I still kind of liked the idea of mini fake exhaust pipes so I went with that thickness paper gaskets and using the fixture I made I tapped the original holes for air fittings and rotated 90 degrees and put in holes for exhaust pipes. Now the intake will be 45 degrees to the left of center and the exhaust 45 to the right. I then turned the fixture vertical and put in my 36 0-80 holes with my fingers crossed for luck (no broken tap)!!! Sorry about the lack of photos. I then needed 9 head caps so I thought I would add a little color and go brass and while at it I might as well make some fake glow plugs. Then for a break I tried my hand at making a prop. Enough for a while.

     Gary
Title: Re: Another air powered (maybe) Radial engine
Post by: galland on September 10, 2018, 02:40:02 PM
I went ahead and made a stand so I could mount the engine on. The front cover and crankcase are one piece but I put an extension on it to make it about 3/16 longer and to give it a more unique look. The rear cover is threaded on to the crankcase and I had to make a new one for the cam (air valve) to pass through it. A couple weeks back I played with several attempts at making very miniature air fittings to take brass or copper tubing for the air lines. Since the cylinders screw on and off I knew if I soldered things together it would be permanent and would not be able to do a tear down if I needed to get inside. So I gave in and decided to go with rubber lines. Here is where it stands today.

     Gary
Title: Re: Another air powered (maybe) Radial engine
Post by: galland on September 11, 2018, 11:22:27 PM
The little radial is finished. Dia. is right at 2 1/2 inches at the top of the brass head covers. Took some looking to find very small air lines. Got the tubing from Mcmaster Carr. Its .040 I.D. and rated 10 psi. max air pressure. Made a new counterweighted crank disk and its very smooth when running fast so I am happy with that. Looked at Rudy K's plans for ideas for the cam/valve. His appears to get intake air till  142.7 degrees  ATDC. I made mine to close off at just shy of the full 180. Anyway it runs but with that many cylinders and being 2 stroke I am not thrilled with the sound. Maybe a bit to busy. My 5 cylinder sounds much better but it also has 7 1/2 times the displacement.

     Gary
Title: Re: Another air powered (maybe) Radial engine
Post by: Ye-Ole Steam Dude on September 11, 2018, 11:35:18 PM
Hello Gary,

The engine is absolutely gorgeous, what a beautiful piece of machining. Thanks for sharing.

Have a great day,
Thomas
Title: Re: Another air powered (maybe) Radial engine
Post by: b.lindsey on September 12, 2018, 12:19:48 AM
Well done Gary. You made short work of turning it into a running engine. Love the stand too!!

Bill
Title: Re: Another air powered (maybe) Radial engine
Post by: galland on September 12, 2018, 03:21:20 AM
Thanks guys. Just for a comparison here he is with his big brother.

      Gary
Title: Re: Another air powered (maybe) Radial engine
Post by: crueby on September 12, 2018, 03:22:40 AM
Beautiful job!!  Any chance you could put up a video of it running?
Title: Re: Another air powered (maybe) Radial engine
Post by: galland on September 12, 2018, 02:33:57 PM
Made a video. I have commented that my expertise on posting them is not my strong point. I will try and see what happens. Am very pleased at how smooth it is because I just guessed on how much to cut off when making the counterweight. Don't know what rpm it was cranking but it never attempted to walk around on that piece of smooth paper. That was 8 psi max.      Gary[youtube1]https://youtu.be/gusJI5Bjs-M[/youtube1]
Title: Re: Another air powered (maybe) Radial engine
Post by: b.lindsey on September 12, 2018, 02:38:18 PM
Its even more impressive running Gary. What a great little radial....one to be proud of definitely!!

Bill
Title: Re: Another air powered (maybe) Radial engine
Post by: crueby on September 12, 2018, 02:39:22 PM
That runs beautiffully smooth - very well done!
Title: Re: Another air powered (maybe) Radial engine
Post by: zeeprogrammer on September 12, 2018, 02:48:17 PM
Wow! Great video. Cranking up the speed got pretty thrilling.  :ThumbsUp:
Title: Re: Another air powered (maybe) Radial engine
Post by: Hagar on September 12, 2018, 04:34:50 PM
Very clean design. I love this tiny star 9. :Love:
It seems to reach high RPM and no vibration. Pretty sound too.

Any device in the crankshaft to rout the air towards the right cylinder or every connecting tube always hold pressure ?
What's hiden inside the heads ? Ball valves ?
Title: Re: Another air powered (maybe) Radial engine
Post by: Ye-Ole Steam Dude on September 12, 2018, 06:31:27 PM
Hello Gary,

Wow, love that video.

Have a great day,
Thomas
Title: Re: Another air powered (maybe) Radial engine
Post by: Tennessee Whiskey on September 12, 2018, 07:29:19 PM
Absolutely awesome Gary. You should have a booth at OshGosh for the EAA crowd  :ThumbsUp: :cheers:

Eric
Title: Re: Another air powered (maybe) Radial engine
Post by: Kim on September 13, 2018, 05:46:18 AM
Great little runner, Gary!  Thanks for the video  :ThumbsUp:
Kim
Title: Re: Another air powered (maybe) Radial engine
Post by: galland on September 13, 2018, 04:26:02 PM
I had sent Hagar a message last night kind of trying to explain how the engine functioned. I am not sure if I am that good at explaining things. If you see this Hagar it is a sketch of how the rear case or chamber works. Nothing on it is to scale. You had asked if there were any type of seals in it to keep air from leaking. Other than my O-rings used to get the air from the base to in the rear chamber there are none. With a rotary valve or cam you just try for the best fit you can get in the bore of the chamber. I did lap the two and feel I got a perfect fit. On the engine I somewhat copied, the air valve from (Rudy K's  Radial 5) His valve or cam has one groove and one flat and the exhaust is sent through a hole into the hollow shaft and out the rear of the engine. On mine I used 2 grooves and each has its corresponding flat so one is intake air and one is exhaust air. The intake flat shoots air into each of the 9 ports as it passes them and the exhaust flat sends the air out 4 ports I put on the bottom side of the chamber (one each in the #4 thru 7 position. The flats are not spaced as shown in the sketch. It was drawn that way to see them better. Hope I didn't bore anyone to death.

      Gary
Title: Re: Another air powered (maybe) Radial engine
Post by: Hagar on September 18, 2018, 06:42:01 PM
Hi Gary,

Thank you for the sketch. The crankshaft is also a rotative valve and is machined very close to the bore + lapping. Skill instead of seals. ^-^

I note this somewhere deep inside my head. Maybe one day, something like this will appear on a future mechanical creature of mine. :naughty:
Title: Re: Another air powered (maybe) Radial engine
Post by: b.lindsey on September 18, 2018, 08:42:30 PM
Hagar, Village Press offers one of their spiral bound books that contains Rudy's radial 5 cylinder. The books are 12-15 dollars IIRC and would give you something to study and look at. Not as difficult as you may think

.https://secure.villagepress.com/store/items/detail/page/2/item/1216

Bill
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