Author Topic: New Compressed Air Hit n Miss Engine (Read 25851 times)

cfellows · « **on:** May 13, 2011, 03:14:58 PM »

I've begun work on a new, hit n miss engine that will run on compressed air. It has a 1" x 1.5" bore and stroke with a 7" flywheel. Two to one cam gearing is incorporated to run in 4 stroke mode like the old engines. This engine is an inverted type, a design which allows the builder to use a much simpler, end-mounted crankshaft and a single, large flywheel. It should be an easy engine to build.

I'm using a new, quick release valve that will allow the engine to run in true hit n miss mode and should sound very much like it's larger, internal combustion counterparts, as in loud! Even tho the engine is pretty large for compressed air, it will be run at full compressor pressure and should only "hit" about every 8-10 revolutions not requiring much air.

Here is a picture of the mostly finished design. Still have some details to add like the governor assembly and the innerworkings of the valve.

I am designing this engine for others to build as well, so I'll provide drawings when they are finished.

Chuck

saw · « **Reply #1 on:** May 13, 2011, 03:45:37 PM »

This engine looks very intressting. I will be follow this project with great intresst.

Rob.Wilson · « **Reply #2 on:** May 15, 2011, 07:32:54 AM »

Interesting design Chuck

Looking forward to seeing the engine take shape

Rob

NickG · « **Reply #3 on:** May 15, 2011, 09:02:25 AM »

Love the vertical configuration Chuck - will be an interesting build this

cfellows · « **Reply #4 on:** May 15, 2011, 07:23:34 PM »

Thanks for the kind words, folks. I do appreciate the interest and the comments.

Got started on the build this weekend. The uprights are formed from 3" x 3/8" thick hot rolled steel, each 6" tall. Most of the work was done with my metal cutting bandsaw and vertical belt grinder. I did use the milling maching to clean up the edges and form the inside radiuses at the top and the bottom. I've included pictures with two different flywheels. I'll probably use the larger, 7" cast iron fly wheel that I had originally planned for but also kind of like the smaller, 6" brass flywheel that I had milled from solid several years ago. I guess I'll keep the option open until I get further along.

Chuck

cfellows · « **Reply #5 on:** May 15, 2011, 07:39:18 PM »

One more picture, I forgot that I had finished the cylinder several days ago. The lump of aluminum the cylinder is sitting on is just to show how it will look with the cylinder head.

Chuck

Brass_Machine · « **Reply #6 on:** May 15, 2011, 09:42:18 PM »

I always look forward to your engine builds Chuck.

great designs and great reading. Have you considered writing a book with your designs...

Eric

sbwhart · « **Reply #7 on:** May 16, 2011, 01:21:47 AM »

Looking forward to seeing this engine grow and that brass fly wheel looks real nice.

Stew

saw · « **Reply #8 on:** May 16, 2011, 05:39:30 AM »

Looking good

Dean W · « **Reply #9 on:** May 16, 2011, 07:03:58 PM »

It ought to be another winner with one of your valve designs, Chuck. I like the "old-time" style. Either of the
flywheels look good, too.

cfellows · « **Reply #10 on:** May 18, 2011, 04:43:28 PM »

Thanks again, folks for all the encouragement and positive comments.

I decided to do the base a little differently than in the original picture. I had planned to use quarter sections of steel pipe to create a cove moulding like I did with the radial. Instead, I'm using 3/8" thick angle iron. I picked up a piece of 2" x 2" by 26" at my local metal yard, brought it home, and cut it down to the size I needed, 1.375" x .625". The bandsaw made this job easier, but it was still a bit tedious to rip it down, not to mention a little hard on my arm muscles keeping the pressure on the feed. Next the piece will be cut down to the proper lengths with 45 degree angles to form miter joints on the ends. The 5/8" leg will be on the bottom, with the cut edge out to form a kind of cove. The base will have 1/4" thick steel plate welded on the top so the total height of the base will be 1.625"

Here's a picture of the base pieces

And here's a drawing with the governor and the new base

Chuck

cfellows · « **Reply #11 on:** May 19, 2011, 05:18:27 PM »

Here's some more pictures of the base taking shape. These are probably not interesting to all of you, but thought I'd show them anyway. So far I have about 5 hours into the base alone.

This is just a pic of me using an indexable cutter to smooth the bandsawed edges.

This is just two views of the lashup on my bandsaw to cut the 45 degee mitre on the first end. The angle iron is mounted upside down with a spacer indexed against the back of the built in vice. Another spacer is used underneath to raise the workpiece high enough that the clamps could find purchase on a flat spot on the back of the vise. C-Clamps are used to hold the work rather than the adjustable portion of the built in vice.

These are pictures where I'm cutting the 45 degree miter on the other end. Here, the angle is right side up.

Getting the pieces cut to exactly the right length was very challenging since it was hard to project where the blade would intersect the base of the cut. Exact length wasn't really important anyway, but getting the opposing sides the same length is important if you want a square base with tight mitre corners. So, I used a stop block clamped to the back of the fixed vice jaw to make sure the matching pieces were the same length.

Here's a few shots of the frame assembled but not yet welded. Outside dimensions measured around the bottom of the base is 5.75" x 6.75". The height of this part is 1.375". The thickness of the angle iron is 3/8".

Now I can cut out the plate that will form the top of the base.

saw · « **Reply #12 on:** May 19, 2011, 05:20:23 PM »

It's just beutifull nice work

millwright · « **Reply #13 on:** May 19, 2011, 05:25:00 PM »

Those bandsawn mitres look to have come out very good. watching the post with interest. have enjoyed your previous projects.
John

cfellows · « **Reply #14 on:** May 19, 2011, 07:49:07 PM »

Thanks again, for the comments and encouragement. Here's a couple more pictures.

The first picture is the base dry fitted with the top. The top is made from 1/4" thick cold rolled steel, 5.5" x 6.5"

And, here is the first of 2 pictures of the parts I finished so far, dry fitted.

And, a second picture with the soda can for scale.

Chuck

KB3RLJ · « **Reply #15 on:** May 19, 2011, 09:10:30 PM »

That's looking great. Keep it coming.

NickG · « **Reply #16 on:** May 21, 2011, 12:42:27 PM »

Nice work Chuck, really nice looking design and maybe even simple enough for me!

Rob.Wilson · « **Reply #17 on:** May 21, 2011, 03:53:58 PM »

looking great Chuck

i sure like the way you are constructing the base

,,,,,,,,,,,,,,

Rob

raynerd · « **Reply #18 on:** May 21, 2011, 04:03:06 PM »

Fantastic workmanship - the base is just great, really smart design..and the brass fly wheel

All the best
Chris

cfellows · « **Reply #19 on:** May 21, 2011, 05:42:12 PM »

Thanks for the comments, folks... always appreciated!

Here is the magic that will make the engine operate pretty realistically (I hope). It's a quick release valve that I discovered in an airgun book. It uses air pressure from the air source to quickly open the valve when the cam rotates to the cutout. In the airgun world, the trigger mechanism releases the valve. Either way, the 100PSI air source should exert a pressure of about 5 pounds on the air valve, more than enough to open it quickly. This first picture shows how it all works in a drawing with description.

And here are the pieces that I've made. The valve body is made from 3/4" brass rod and the valve is 1/4" drill rod.

And this picture shows where the valve body sits on the engine base

Chuck

NickG · « **Reply #20 on:** May 22, 2011, 07:02:35 AM »

Chuck,

thanks for explaining the valve mechanism clearly. What sort of pressure do you think this would work down to? I can see that it's partly due to the strength of the spring on the ball and I realise that you want it to behave as much like an i.c. engine as possible hence the high pressure but was just wondering. I guess it wouldn't sound much like an i.c. at the lower pressures but should still work? It won't take much pressure to lift the valve off its seat. I initially thought by looking at your cam you were getting the pressure to act in a short sharp burst but looking again it looks like the valve can be open for about 90 deg on the cam? = a full stroke? I guess you could play tunes with that too but the way you have it will give the most power.

Anyway, brilliant stuff

Nick

cfellows · « **Reply #21 on:** May 22, 2011, 11:44:31 AM »

Quote from: NickG on May 22, 2011, 07:02:35 AM

Chuck,

thanks for explaining the valve mechanism clearly. What sort of pressure do you think this would work down to? I can see that it's partly due to the strength of the spring on the ball and I realise that you want it to behave as much like an i.c. engine as possible hence the high pressure but was just wondering. I guess it wouldn't sound much like an i.c. at the lower pressures but should still work? It won't take much pressure to lift the valve off its seat. I initially thought by looking at your cam you were getting the pressure to act in a short sharp burst but looking again it looks like the valve can be open for about 90 deg on the cam? = a full stroke? I guess you could play tunes with that too but the way you have it will give the most power.

Anyway, brilliant stuff

Nick

Hey Nick, thanks for the input. There are a number of variables that determine how these air engines operate. I'm in new territory with this quick release inlet valve but I do have some experience now with the ball slave valve. With a lighter spring, the engines will run on lower pressure but they won't rev as high. Most of my engines are slow runners and I use a light duty spring, about 5/32" OD, 3/4" long, wire size of .012" - .015". They will run well on about 40 PSI, maybe less.

For this engine to sound as realistic as possible, I want it to free-wheel for as many revs as possible, then hit really hard when it fires. The idea is to control the speed with the governor, not the air pressure.

I finished up the valve last night to a point where I could test it. With the valve closed, there was no leakage, and the air pressed hard on the valve stem. However, I was able to hold it with my thumb and forefinger. I think this valve is going to work well, although I might have to rebuild the valve body for a smaller, 3/16" valve stem... 1/4" may exert too much pressure on the cam assembly.

Chuck

cfellows · « **Reply #22 on:** May 23, 2011, 11:34:34 AM »

I'm into the fiddley bits now so progress will probably be slower and not very exciting. I had decided to use 3-48 SHCS to fasten the two halves of the valve body assembly to the base. However, after I drilled and tapped the holes, I found that my screws were too short. So, I made some brass screws from a piece of hex rod I had on hand. Screws turned out nice:

But, when I tried to tighten them down, I promptly twisted one off. Guess brass was a bad idea in these small sizes. So I drilled out the holes and tapped them to 4-40. Had the right size screws on hand and screwed the valve assembly to the base:

Next I started on the timing gears. The small gear is made from two pieces, the gear and the hub. After the gear teeth are cut, the gear will be bored out, then loctited or hard soldered to the hub / collar. Here I've turned the gear blank and the hub at the same time from a piece of 1" 12L14.

Next I'm parting off the hub:

Here's a picture of all the gear blanks. The large timing gear was turned from cast iron and will have a pitch diameter of 1.5". The small gear is mounted on a mandrel, ready to have the teeth cut:

Today's work will include cutting the teeth on the gears and getting the smaller, primary gear assembled into one piece. Then, it's on to the cam.

Chuck

cfellows · « **Reply #23 on:** May 23, 2011, 07:47:24 PM »

Here's a couple of pictures of the gears. The first picture shows the primary gear set before assembly.

And here's a picture showing the large timing gear and 2 copies of the small timing gear with hub. The one on the left shows a pitiful attempt at silver soldering. I used too much solder and got the assembly too hot. This resulted in solder flowing into the valleys between the teeth. I tried to dig the solder out but no luck. Now I know why they call it hard solder! The assembly to the right is put together with loctite 620. It will probably hold alright... at least I've not had it fail on any of my applications yet.

Chuck

cfellows · « **Reply #24 on:** May 23, 2011, 10:27:41 PM »

One last picture for today. Got the cam finished and attached to the large timing gear.

CallMeAl · « **Reply #25 on:** May 24, 2011, 12:05:06 AM »

Very imaginative work! I am looking forward the the little gem of an engine is is destined to be.

saw · « **Reply #26 on:** May 24, 2011, 04:34:47 AM »

Nice work.

John Hill · « **Reply #27 on:** May 24, 2011, 03:48:28 PM »

A very interesting project Chuck and I am looking forward to see how it runs!

raynerd · « **Reply #28 on:** May 24, 2011, 04:51:55 PM »

Hi chuck, nice work. What setup do you use for cutting the gears and did you use purchased cutters or homemade? I'm always interested in gear cutting!!

Excellent stuff Chuck, keep it up!

cfellows · « **Reply #29 on:** May 24, 2011, 11:46:50 PM »

Quote from: craynerd on May 24, 2011, 04:51:55 PM

Hi chuck, nice work. What setup do you use for cutting the gears and did you use purchased cutters or homemade? I'm always interested in gear cutting!!

Excellent stuff Chuck, keep it up!

I used a spin index with a 5/8" 5C collet. The gear blanks were mounted on a spindle I made from 5/8" CRS. The spin indexer was modified several years ago by cutting the flanges off the base so it would clamp into my milling vice. The cutters were commercial, 24 pitch involute gear cutters.

Thx...
Chuck

cfellows · « **Reply #30 on:** May 31, 2011, 10:18:24 PM »

Managed to get a few more things done. The governor is patterned after the one Phil Duclos used on his Victorian engine. I made the 5/8" brass balls using an over-the-top ball turner that I had made several years ago. Before I could use it however, I had to adapt it to my QCTP. I used the boring bar holder and inserted a 3/4" brass bar that I had bored out to 1/2" to accommodate the 1/2" shaft of the ball turner. The small protrusions on one end of each ball will be turned off and bored to accept the swing arms of the governor.

I also made the piston and the connecting rod. The latter is made from 3/8" thick x 3/4" wide aluminum. Finally, I also finished the crank disk but still have to make the crank pin.

And, here's a couple of images with a few of the parts loosely hanging in place

Chuck

cfellows · « **Reply #31 on:** June 06, 2011, 09:44:13 PM »

Well, I think I'm within a day or two of having this thing ready for a test run. It will take a little longer to get the governor bits all hooked up so it runs in hit n miss mode, but I should have all that part finished as well in less than a week, maybe by the weekend sometime. I'm really pleased with the way everything is turning out. I think this will be a nice looking and good running engine.

Got to get it finished, I'm already thinking about my next project.

Chuck

sbwhart · « **Reply #32 on:** June 07, 2011, 05:18:27 PM »

Thats comming together real well Chuck, looking forward to seeing it run.

Stew

cfellows · « **Reply #33 on:** June 09, 2011, 06:27:08 PM »

Thanks Stew.

I got the engine running last night and made a number of improvements and tuneups today. Once I got it all together, there were several embarrassing problems that I had to correct.

- The connecting rod was too long so the piston was hitting the head before top dead center. Had to mill a depression in the head and face a 1/16" off the top of the piston.

- The connecting rod was hitting the side of the cylinder so I had to turn a bevel on the inside of the cylinder and turn the rod down to a smaller diameter.

- The valve travel was insufficient to open the valve, so I had to do some more machining on the cam. Also had to increase the dwell since the valve wasn't staying open long enough.

Today I corrected all that. I also added the plumbing to bring the air supply line out the side of the base. Now all I have left is to complete the governor and valve latching mechanism so it will run in hit n miss mode.
Got a video loading on youtube at the moment.

I will post the video as soon as it finishes uploading. Here are some pictures.

Chuck

cfellows · « **Reply #34 on:** June 09, 2011, 06:27:44 PM »

And here's the video...

http://www.youtube.com/watch?v=9xECJ4WTrf8

Chuck

sbwhart · « **Reply #35 on:** June 10, 2011, 01:20:22 AM »

Very Very Nice Chuck sounds like a big engine,

I,m intersted seeing how you link the hit a miss governor up.

Stew

Dean W · « **Reply #36 on:** June 10, 2011, 03:31:02 AM »

Really neat, Chuck. It has a very satisfying bark to it, too.
I watched through the thread as you built and had an idea of the size, but there's nothing like
seeing a guy's hand reach in there to really get a sense of size. It's pretty big.
What a good engine it is!

Dean

srm_92000 · « **Reply #37 on:** June 10, 2011, 05:49:33 AM »

Hello, I've been following the build with interest.

Love the valve system etc. and sounds just great

Shame it's not a twin or 'V' 4 though

Cant wait to see the governor link working.

Steve

Rob.Wilson · « **Reply #38 on:** June 10, 2011, 12:35:38 PM »

Hi Chuck

Now thats a very clever bit of engine design work ,,

,, you have the period look right

Great runner too

Rob

cfellows · « **Reply #39 on:** June 10, 2011, 05:19:34 PM »

First, thanks to everyone for the appreciative comments. Always enjoy knowing people are watching.

I was drilling and tapping 2-56 holes in the brass governor balls today to hold the screws that the springs will attach to. Of course, on the second ball, the tap got stock and I broke it off trying to get it out. Still not sure why it stuck. Anyway, after a few minutes of muttering and resisting the impulse to throw the part across the shop, I got the torch out to heat up the ball so I could take it off and make another. After I got it off, I was standing there looking at it when it ocurred to me, why not just rotate the ball 90 degrees and glue it back on? So, that's what I did. I put the broken tap hole on the inside where it will probably never show any.

Now if I can just drill and tap the holes without breaking a second tap... of course, I could always just rotate it 45 degrees and try again!

Chuck

Bernd · « **Reply #40 on:** June 10, 2011, 07:05:54 PM »

Keep drilling holes in it and you'll have a "wiffle ball".

Nice work so far.

Bernd

cfellows · « **Reply #41 on:** June 10, 2011, 08:46:02 PM »

Here's another video, this time in hit n miss mode. It's hitting every 3rd revolution of the cam which is every 6th revolution of the engine. Since I posted this video, I've made a couple of changes. I opened up the inlet passages from 5/32 to 3/16". I think I have one more place, the hole in the side of the valve which is still 5/32 which I will check later. Now it's hitting about every 4th revolution. I'm also going to add an o-ring to the piston and see if that helps. But for now, it runs pretty good.

http://www.youtube.com/watch?v=hNC36MoBCyw

Chuck

Brass_Machine · « **Reply #42 on:** June 11, 2011, 12:40:27 AM »

Chuck...

Very nice. Again, have you given thought to putting all your plans and designs into a book? I know I would buy one.

Watched the videos. Engine sounds great. In hit/miss mode it has a cool rhythm. My wife thought I was listening to a song on low volume

Eric

BiggerHammer · « **Reply #43 on:** June 11, 2011, 08:07:07 AM »

Very nice, one you should be proud of. Excellent on the governor.

cfellows · « **Reply #44 on:** June 11, 2011, 05:10:11 PM »

I'm considering this engine completed. Took me a couple of days less than a month from start to finish. After the last video, I opened up all the inlet air passages to 3/16" and also added a single o-ring to the piston. With those mods and a little breaking in, the engine will now coast between 10 - 12 revolutions between power strokes. Don't think I can do much to improve it now except maybe bore it out a little, but I think it sounds fine as is. Here's the final video:

http://www.youtube.com/watch?v=oR8q_vDgXD0

Recap: 1" bore x 1.5" stroke, flyball governor (5/8" balls), 7.25" flywheel

Chuck

CallMeAl · « **Reply #45 on:** June 13, 2011, 12:01:00 AM »

Great work and wonderful result! Sounds great and I like how the governor works. Thanks for sharing your work Chuck!

NickG · « **Reply #46 on:** June 16, 2011, 02:53:49 PM »

Absolutely brilliant Chuck, it runs so well in hit & miss mode now. I presume as soon as you put any kind of load on the flywheel it'll start hitting?

So cool

I agree with Eric, if you feel you've got the time a book would be a great idea!

Nick

News:

Author Topic: New Compressed Air Hit n Miss Engine (Read 25851 times)

Rob.Wilson

Rob.Wilson

Rob.Wilson