Time for a Radial

[Deanofid]

Wow, it sure is looking good, Chuck. Really nice!

 

[steamer]

I'm really liking the brass......Haven't figuried out the valve thing yet...but keep going...I'll catch on.

Dave

 

[cfellows]

Thanks for the comments, Stew, Dave, Deanofid. After a lot of noodling and mind changing, I think I've worked out the details for the back end of the engine. The cam will have two lobes, 180 degrees apart and will turn at 1/4 the speed of the crankshaft. The cam will be coaxial to the crankshaft with double reduction gears 12/24, 12/24 to arrive at the 1:4 reduction. So here are a couple of pictures of the back crankcase cover. Here I'm machingin the back side and the timing gears will be inside the hollowed out part. The valve lifters will be set into the ring that has been formed. Further maching will be done on the ring and, in the end, it won't be a ring. Hard to explain what I have in mind, guess you'll just have to wait and see it.

The ring part, btw, is 1 7/8" OD x 1 3/8" ID.

Chuck

 

[cfellows]

Got some work done since the last post. Here are some pics of the timing gears. The two larger ones are 40DP, 24 teeth, 1/8" thick and about 6.5" OD. The smaller gears are on the 3/8" rod and haven't been parted off yet. They will be 12 teeth and are .35" OD.

One of the 12 tooth gears will be loctited onto the crankshaft and drive a 24 tooth gear below it. The 24 tooth gear will be ganged to a 12 tooth gear, which will, in turn, drive the other 24 tooth gear which turns freely on the crankshaft. The double lobed cam will be attached to the second 24 tooth gear on the crank and will turn at 1/4 the RPM of the crankshaft.

Chuck

 

[cfellows]

Got all the timing gears done. I decided to make the primary gear and shaft one integral unit rather than trying to loctite or solder the gear to a shaft. The second and third gears are ganged and soldered together. Then, the fourth gear rides on the crankshaft at 1/4th the speed of the crankshaft. The cam will be attached to the fourth gear, probably with a mechanism which allows for timing adjustments.

Chuck

 

[Captain Jerry]

Hi Chuck

That is really nice work! I was wondering how that first gear was going to work out on the shaft. Making it integral with the shaft is a great solution.

I have been watching this build with a lot of interest. You do a great job of explaining the design options and solutions. Your ball valve and slave exhaust valve is really interesting.

I have been kicking around the idea of implementing your valve on one of my oddball engines and have a few questions about the details. I'm not particularly concerned about making a four stroke operation and the sound is secondary. I'm mostly interested in avoiding the sealing problems associated with a rotary valve on the crankshaft.

The engine will be a two cylinder double-acting design with 90 degree offset for self starting. Its a little more complicated in that there will be no rocker arms. The valve actuator rods (push rods) will be in direct contact with the cam, sort of like an OHC design.

Is sealing around the push rod a problem? Does the push rod need a separate return spring or is the spring tension against the ball enough? How well would this valve work for self starting and low RPM? What should the cam profile look like? Would a conventional eccentric work?

Lots of questions, I know. Hope you don't mind the distraction.

Jerry

 

[cfellows]

Jerry, thanks for the kind words and your interest in the ball slave valve. Let me first say that my slave valve arrangement is mostly designed for the sound it makes and is not particularly efficient. However, to answer your questions, sealing around the push rod is not particularly important as long as the fit isn't really sloppy. You may get a little leakage, but you'll hardly notice since most of the air is going into the cylinder. Depending on which of my design's you're referring to, and there are many, you probably won't need a spring on the push rod. The valving arrangement works fair for self starting engines, but isn't 100%. For my engines, I like a very sharp cam profile with a short lift, but that's mostly for sound. A conventional eccentric would work OK as long as the inlet valve is completely closed by bottom dead center of the piston.

Since controlling air leakage is your first priority with self starting being a close second, let me suggest the following vave design. It runs quietly, can be made with virtually no air leakage, and produces a powerful engine. You could substitute a ball valve for the poppet valve if you want and it would work well.

As you can see, it uses a single push rod and a cam with a little higher lift than usual. As the cam (or eccentric) first engages the push rod, it closes the exhaust port. Futher motion of the push rod then opens the inlet valve and provides the power stroke. I don't have a video of this engine and have since modified it to use a slave valve, but it did run very well and I think it would be more suitable to your application.

Let me know if you have questions.

Chuck

 

[cfellows]

I think I've wrestled all the remaining design questions to the ground so the worst part is over. Today I made the back timing gear cover or back cover for the back crankcase cover which is confusing, I know. I've also drilled and tapped the holes.

Next, I'll be cutting away a significant part of the back cover and the sides of the ring to look something like this:

Chuck

 

[rleete]

I saw the first pic and was just about to ask what happened to the open design. Glad to see you're exposing the inner workings.

Any plans for a clear cover, to keep out dust (and curious fingers)?

 

[cfellows]

I'm not seeing any clear covers in finished engine. Leaving it open aids in the lubrication process. I don't think there will be anything dangerous to little fingers.

Today I got started opening up the timing gear cover. Milling, filing and sanding are not my favorite operations, but it did turn out OK.

Here you can where I've got the back part of the crankcase in a 4 jaw chuck on a rotary table. I'm using a 1/4", 2 flute end mill to do the hogging, taking .050" per pass.

Here you can see the whole lash-up.

For the last pass of the cut, I've switched to a ball end mill to give me a radius at the bottom.

Here I've moved over and am cutting out the waste on the other side.

I've finished up all the work with the end mill.

Several operations later, I've removed the rest of the waste, and filed and sanded to get it prettied up.

The next series of pictures shows the part on the engine in various positions so you can kind of see what it's going to look like.

Still have a little refining and tuning to do, then I'll get on with cam...

Chuck

 

[vascon2196]

How do you do all of this so fast!!!

Great job Chuck!

Chris

 

[kanvelchoudhary]

hi chuck
no doubt this project is as good as all previous ones and more challenging.
nice job done.
i hope after this you might think about starting you glow plug engine design.
you left it in mid way
will you be uploading the drawings and designs as you did of your 4 opposed cylinder compressed air engine.

 

[cfellows]

How do you do all of this so fast!!!

Great job Chuck!

Chris

Thanks, Chris, it doesn't seem like it's going very fast to me, but, I am retired so I have quite a bit of time to spend on it.

hi chuck
no doubt this project is as good as all previous ones and more challenging.
nice job done.
i hope after this you might think about starting you glow plug engine design.
you left it in mid way
will you be uploading the drawings and designs as you did of your 4 opposed cylinder compressed air engine.

Thanks. I will get back to the hot tube engine eventually. I need to do some test builds of injector pumps and injectors to see if I can get them to work. Then, I'll get serious about the engine.

As to plans for this engine, I will probably put together some drawings.

Very nice work Chuck.
Thanks for sharing it.

Thanks!

Chuck

 

[cfellows]

Tonight I made the cam for my radial. I was able to use my new rotary mounted chuck and it worked great. The cam is made from a 1.125" diameter brass disk about 5/32" thick. The lobes of the cam extend 1/16" so the disk diameter that is left is 1" diameter. In this first picture I have started cutting the disk. I advanced the disk .030" into the cutter, then turned the chuck with 28 turns of the crank. This rotated the cam 140 degrees. Then I raised the cutter above the work and turned the crank another 8 turns, rotating the the disk 40 degrees before lowering the cutter back into the disk. Then I repeated the procedure to cut the other half of the cam. I made two more passes advancing the part .020" then another .015" for the final pass.

Here is a picture of the whole setup:

Here is a picture of the arbor setup I used to hold the disk for milling:

Here is the timing gear and cam setup as it will sit in the engine:

I still have to round off the cam lobe tips and fasten the cam to the final gear in the gear train. I will probably cut a radiused slot in the cam disk so I will have some timing adjustment available to me.

Chuck

 

[tel]

Very pretty work Chuck - especially the gears! Thm:

 

[cfellows]

After a week of being sick and a couple of weeks working on projects deemed higher priority by the chief financial officer, I finally got some work done on this engine. I completed the profile on the cam disk, attached it to the final timing gear and made and fitted the valve lifters. Running the assembly with my drill proved it to be a smooth working assembly. I think this part is going to be particularly interesting to watch when the engine is running slow.

Chuck

 

[cfellows]

The work I finished yesterday and today doesn't look like much, but I am happy to report that all the engine internals inside the crankcase are completed. Also completed is all the timing gear and cam assembly including the valve lifters. All that remains are the pistons, the the rocker arm assemblies, push rods, air supply hookups, and exhaust pipes. Fit and finish to this point all seem as good as I've ever done and the engine turns over smoothly with a drill, albeit, still a little tight.

Here you can kind of see the master connecting rod and a bit of the crank assembly.

Here's another shot of the cam gears and cam, lots of oil on everything.

The front of the engine, showing the beefy, 5/16 crankshaft.

And and overall side shot, again showing the cam and cam gears.

Later, I'll post some pictures of the engine disassembled to better show off the internals.

Chuck

 

[agmachado]

Hi Chuck,

That's very cool... or better saying, absolutely fantastic! :bow:

Cheers,

Alexandre

 

[swilliams]

Really nice Chuck, great creativity with the design :bow: :bow:

 

[Noitoen]

Nice work. You could make a transparent cover for those gears and cam