Inverted Hit n Miss Engine, Compressed Air

[cfellows]

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

 

[metalmad]

An elegant start Chuck :bow:
Pete

 

[cfellows]

Thanks, Pete.

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

 

[Dave G]

My how I love scratch builds, this thing will keep me interested. Very nice Chuck, Dave

 

[cfellows]

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

 

[kcmillin]

Great project Chuck! I love how you incorporate IC characteristics into air engines. It really makes then unique.

That brass flywheel looks great, I don't think I could ever get the first cut done on such a large piece of brass, too nervous. :big:

Kel

 

[Brian Rupnow]

Looking very good Chuck. I will be watching this one.---Brian

 

[cfellows]

Thanks, Brian. No issues with valves that won't seat on this model!

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.

 

[cfellows]

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

 

[mklotz]

Tell us, Chuck... What's it like to never sleep?

Seriously, looking great, as always.

 

[cfellows]

Tell us, Chuck... What's it like to never sleep?

Seriously, looking great, as always.

Thanks, Marv, high praise indeed coming from you!

Well, I do have to sleep, but being retired, I don't have to work, as long as I can stay below the significant-other's radar...

Chuck

 

[maverick]

Another nice build Chuck, very elegant. But take it easy will ya. You're making us guys with day jobs look bad.

Regards,
Mike

 

[Chaffe]

looking very traditional, and heavy! brilliant

 

[cfellows]

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

 

[ShedBoy]

Wow Chuck that looks great. Can't wait to see this one running!

 

[bearcar1]

Oh I do like the way that base turned out for you Chuck. And kudos for showing us how it was done. Were you a cabinet carpenter in your previous life? Those mitered corners really turned out quite well. Thm: And BTW, you must stay very low under the Mrs.' radar to have enough time to accomplish all of that in such a short time. :big:

BC1
Jim

 

[Brian Rupnow]

Well Dang!!! I'm sure glad the world didn't end afterall---I would hate to have missed this build!!! Chuck, about 20 years ago I was involved in a research project on pneumatic "Impact cylinders". They were interesting, and very scary whe they "fired". Imagine, if you can, an air cylinder with a double ended rod. the rod at one end is exposed in the normal fashion, but at the other end, the rod passes thru an airtight gland into a second chamber which is filled with high pressure air at 100 to 150 pounds. To fire this cylinder, low pressure air is admitted to the back side of the piston, and the piston rod begins to extend the way you would expect. Then about half way thru its stroke, the back side of the rod pulls out of the gland seperating the low pressure side from the high pressure chamber and all of that high presure air in the high pressure chamber floods thru the now open gland in a big rush, driving the piston the rest of the way thru its travel like a cannon. I think that is similar to the way pneumatic nailers work. The force (impact) generated was beyond belief.---Brian

 

[b.lindsey]

Looking wonderful Chuck. Just a great design all the way around...certainly looking forward to seeing it run...which won't be long at this current pace...lol

Regards,
Bill

 

[cfellows]

Thanks, Bill. Hopefully I can keep up the momentum.

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]

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