Time for a Radial

[cfellows]

Figured it's about time for a radial engine. It'll be compressed air using my ball slave valve arrangement. Operation will be 4-stroke using a 2 lobe, coaxial cam turning at 1:4 ratio to the crankshaft. Here's the beginnings of a concept picture:

I started out rough cutting a hexagon out of 1.25" thick aluminum tool plate with my 4 x 6 band saw. Then used a 1" arbor to chuck it up in my 5C hexagonal block. I used a 2" indexable carbide mill to face off each of the 6 faces.

Wound up with what seems like a respectable hexagon 1.25" thick and minor diameter of 2.443" (Yeah, I over shot the target diameter of 2.500" :-[)

Chuck

 

[b.lindsey]

Looks like a great project Chuck, and already off to a good start too. Will look forward to seeing it come together.

Bill

 

[1hand]

Chuck

I'm on board! Whats the bore going to be?

Matt

 

[dreeves]

Chuck,

Just when I thought I was done with radials you had to hatch this plan. well Im in I need another :big: :big:

Dave

 

[Brass_Machine]

Woot. Another one to watch! Go Chuck go!

Eric

 

[cfellows]

Looks like a great project Chuck, and already off to a good start too. Will look forward to seeing it come together.
Bill

Thanks Bill, don't have all the design details worked out yet, but that's pretty normal for my builds.

Chuck
I'm on board! Whats the bore going to be?
Matt

Hey Matt, it'll be 5/8" bore x 3/4" stroke (give or take a few thou )

Chuck,
Just when I thought I was done with radials you had to hatch this plan. well Im in I need another :big: :big:
Dave

Thought you needed another project, Dave... 8)

Woot. Another one to watch! Go Chuck go!
Eric

Thanks, Eric, I'll try to keep it exciting!

Chuck

 

[Metal Butcher]

Chuck. I'm looking forward to watching your build.

It's gonna be a dandy!

-MB

 

[swilliams]

Looks like a fun build Chuck. I'll be watching

Steve

 

[doubletop]

Chuck

I'm watching as well

Pete

 

[cfellows]

I finished a prototype of one of the cylinders today. As you can see in the drawing, I've made a change in the design. Instead of using 2 long studs on either side of the cylinder to hold the cylinder and head in place, I decided to make the cylinder and the head one integral piece and use 4 SHCS's to faster the cylinders to the crankcase through a square flange in the base of the cylinder. I don't like the look quite as much, but it will be easier to build.

I still have a little work to do to the cylinder before I'm finished with it.

Chuck

 

[Brass_Machine]

That's a good looking cylinder. Whats the external diameter on that?

Eric

 

[cfellows]

That's a good looking cylinder. Whats the external diameter on that?

Eric

Thanks, Eric. The external diameter is 1.125". The square base is also 1.125" on a side. The fins are 1/8" deep. Overal length of the cylinder and head is 2".

Chuck

 

[cfellows]

I made a few more chips today. I'm proceeding cautiously since I'm still designing as I go along. The first thing I did was radius the edges of the fins and the head on the cylinder. I was trying to make a radius form tool but decided in the end I was overthinking the problem. I ended up just using a small file and sandpaper to make the radiused edges. I also started doing some milling on the crankcase. I may leave the outside profile this way or I may go ahead and finish radiusing the parts of the crankcase between the cylinders like the drawing. Finally, I started work on the master connecting rod spool. It was my first foray into machining 12L14 steel (a piece I inherited from Shred, I might add). Lovely stuff to work with.

Chuck

 

[ttrikalin]

Beautiful! :bow: :bow: :bow:

I admire you for designing it as you go. Undoubtedly a result of extensive experience and superior mechanical understanding and intuition.

Take care,

tom in MA

 

[cfellows]

Beautiful! :bow: :bow: :bow:
I admire you for designing it as you go. Undoubtedly a result of extensive experience and superior mechanical understanding and intuition.
Take care,
tom in MA

Thanks, Tom. Mostly, I just find it hard to stay out of the shop. I get impatient and also have an easier time visualizing in the solid. Unfortunately, sometimes I get the steps out of sequence and make life difficult for myself.

Chuck

 

[zeeprogrammer]

Very nice looking cylinders Chuck.

And I like your philosophy too.

 

[cfellows]

Managed to squeeze in a little more time on the radial. I'm designing and making different components to see a)if I can, and b)whether they'll fit together as planned.

In these pictures, I'm making up the components of the connecting rod assembly. There is still a lot of finish work to do on the pieces, but there's some tips here I thought worth sharing.

First picture is an overall shot of what I'm trying to get to. You can see the master rod in the upper left. The 5/16" curve at the bottom fits snugly against the center hub of the spool.

The three little pins are 1/8" diameter and are shouldered down on the end to accommodate a 2-56 thread. The pins slide through a 1/8" hole in the top of the spool and thread into 2-56 holes in the bottom of the spool. The pins will be cut off flush with spool and a screwdriver slot cut on the top end. This was the method Rudy Kouhoupt used on his 5 cylinder radial air engine.

So the first problem is to shoulder down the end of each pin to .085" for a length of 1/8" I wanted to use my minilathe for accuracy and to take advantage of the freshly sharpened tangential tool bit.

Since I don't (yet) have a carriage stop, I engaged the lead screw and used my leadscrew crank on the left end of the lathe to control the length of the cut. Since the leadscrew is 16 TPI, 2 full turns advanced the tool bit 1/8".

The next trick was to cut a 2-56 thread (squarely) on the shouldered end of the 1/2" long pins. So, I mounted the pin in the chuck of my tapping guide and laid the die, mounted in a die holder, on the table. This worked very well to cut the threads squarely.

Chuck

 

[Captain Jerry]

Chuck

Thats a good looking design. Your 4 cycle style valving ought to add a lot of interesting detail. How do you plan to set up the gearing?

Jerry

 

[cfellows]

Chuck

Thats a good looking design. Your 4 cycle style valving ought to add a lot of interesting detail. How do you plan to set up the gearing?

Jerry

Thanks, Jerry. Current thinking is that the valve gearing will be on the back of the engine, although I would prefer the push rods to be on the front of the engine. I also haven't made a final decision on the gearing. I'm currently leaning toward the option of using a 9 tooth pinion on the crank and 3 separate 18 tooth cam gears, 1 for each cylinder. The other option is to use 2 sets of 12/24 tooth gears with the primary, 12 tooth gear fixed to the crank and the final, 24 tooth gear freewheeling on the crank. This latter option would yield a 4:1 ratio and would require a cam with 2 lobes 180 degrees apart. The second option is more interesting and kind of apealling but requires more space.

Chuck

 

[cfellows]

I'm pretty pleased with way the crank assembly is turning out, especially the 3 shouldered screws that hold the connecting rods in. This fiddly little pieces tend to give me problems, but I took my time and they turned pretty good.

I plan to do some additional milling on the center spool to remove some weight. I may also do some light shaping of the connecting rods so they look less clunky.

Chuck