Elmer’s #5 Geared Engine . . . maybe

[stragenmitsuko]

might I suggest a curved spoke ( filip duclos ) flywheel .

 

[nel2lar]

Bob
Very nice work.
Nelson

 

[bmac2]

Thank you Nelson

Stragenmitsuko I thought about that and I think they look great on my Webster. Yep, this thing started out as “I wanna build a Webster”. I deviated from the plans just a little bit.

https://www.homemodelenginemachinist.com/threads/water-cooled-webster.23224/

I didn’t get much done today what with work, eating dinner and having a nap but I did get the flywheel roughed out. Environment Canada has issued a heat warning for the rest of the week so with the shop being in the basement (a nice 19c down there) I hope to get it finished during the week and start on the gear over the weekend.

 

[bmac2]

When doing a spoked flywheel I like to map everything out in CAD labeling all the drill points and use the center as zero. From there I create a drill chart showing me the X and Y offsets for each hole.

This is my cheater for setting up the 4” rotary table. It has a .375 shank that fits the holder with a plug that’s a snug fit into the center of the table and a handy .25 reamed hole. It may not be as exact as indexing but it’s very close and real fast to setup.

Then by putting a short piece of drill rod into the hole in the plug and I can use it to align the flywheel blank on the table. Clamping on a small table can be challenging, the setup looks dodgy but it feels very solid. One of the things I like about this setup is that everything is at my “0” mark.

Used a 1/8” end mill to drill out all the end points then milled out to top of the openings. My wife reminded me that I had to go to work in the morning so I returned everything to “Zero”, locked down “X” and “Y” and called it a night.

 

[bmac2]

Today it’s 30c outside, but it’s nice and cool in the shop. Without the check list and a DRO there is no way I’d attempt stopping in the middle of this. But thanks to my handy highlighter pen it only took me a minute or two to get back to making chips. Finishing the spokes didn’t take long, just had to set the angle and offset and mill them out.

It came out just like the drawing and it looks good . . . . But Stragenmitsuko had brought up curved spokes and that got me thinking. With a flywheel it’s the mass along the outer diameter that counts. With a spoked flywheel I don’t think the spokes add much so I decided to add a little style by running the mill down the middle of each spoke. I like the look but I’m thinking I might have to add some weight around the rim.

I got the notch cut out in the base and I’m calling it a night.

 

[stragenmitsuko]

that is an absolutely beautifull flywheel !

 

[bmac2]

Thanks Stragenmitsuko.
Hay You started it. I’m so close to where I have to think about the gears I would have probably stopped with the stock one.

 

[Brian Rupnow]

Very nice work and great documentation.--Brian Rupnow

 

[bmac2]

Thank you Brian I’ve been following your Double Oscillator build.
Somehow I knew you were going to work a pulley onto it.

 

[bmac2]

I didn’t get much done on the weekend, our anniversary was Sunday, but did manage to sneak in a few hours on Saturday.

Knocking out the eccentric was just some simple off set turning in the 4 jaw with a little drilling and reaming.

And I guess this is where the drawings turn into more of a guide line. I’m fairly confident in my math so I guess the only way to see if this is going work is to just do it.

The gear arm is as in the original drawing with the offset for the orbiting gear was reduced to .312. The hole for the piston rod screw is drilled for a no.6 because as it turns out I don’t have a no.5 die.

I need is a 21 tooth gear with a .6155 diameter. That didn’t work out with the gear cutters I have but after trying one in aluminum it fit the ring gear ok(?) so I went ahead and cut one from brass.

In the instructions it says “Piston rod screw must be exactly centered between two teeth”. I may look out a bit in the pictures but it’s about as close as I can imagine getting it. The plans call for silver solder here but for now Loctite will have to suffice.

 

[stragenmitsuko]

been wondering as I followed this build .
You've already made the piston and cilinder , right .
If a smaller ring gear is used , that ought to affect the stroke of the piston .
Did you adapt the dimensions of the cilinder/ piston also ?

Pat

 

[bmac2]

Hi Pat. Yes the gear arm is .063 shorter than Elmer’s plans so the cylinder and connecting rod need to be 1/8” shorter . . . . . . . unfortunately I forgot about that when I started, and made them straight off the plans. This will leave an extra .063” (1.5mm) between the piston and the heads at dead center but I don’t think it will affect performance. If worst comes to worst I’ll just make a thicker piston to fill the void.

 

[stragenmitsuko]

Bob ,

I think I understand now .
The stroke is twice the pitch diam of the internal gear .
Crank throw and gear arm have to be of equal length , that makes it 4 times .375 from tdc to bdt
on the original plans wich results to 1.5 inch stroke .
At tdc the crank centre is on one end of the internal gear , and the con rod on the other end .
Dividing it exatly by 2 for any angle , wich results in the straight motion .
Hence the importance of the centrelines passing trough the teeth centres .

Does that sound about right ?

Been also looking at my box of internal gears , but all I have are ring gears with odd numbers of teeth .
45 , 47 and 53 teeth . Those won't work for sure .

 

[bmac2]

This thing is hard to explain isn’t it?

Hang in there for gears. There have to be thousands of dead drills out there.

Every time I saw someone build on one of these things I’d start messing around in CAD.

This is what I’m going on. I don’t feel that the size of the ring gear is all that critical. As long as it has an even number of teeth and the orbiting gear is half the size it should work. Then so long as the holes in the gear arm set at half the diameter of the orbiting gear this will put the piston rod screw running along a line with the center of the crank shaft. In this drawing the diameter of the gear could be 2 inches of 2 feet and the geometry stays the same. It would have to fit within the envelope of the engine of course.

Sorry, I’m not sure if that even makes sense to me and I wrote it!

My plan is to make an adaptor ring with an outside diameter the same as the gear called for in the plans and bore a hole into it to fit the gear I’m using. This way most parts are per the drawings.
You’ll notice that the orbiting gear runs in the opposite direction of the crank shaft.

 

[stragenmitsuko]

Nice cad work , and it makes perfect sense .

Tell me , what cutter did you use to make the gear ?
21 tooth gear with a .6155 diameter , I 'de say it's a 0.7 Mod gear .

 

[bmac2]

Oh the gear . . . . The math just didn’t work out with the cutters I have. On top of that I couldn’t come up with a way of measuring the ring gear teeth. What I ended up doing was making a couple of gears from aluminum and just trying them. In the end I used a Module 1 PA20 No.3 and a small V file to tweak the teeth a bit. It is going to be noisy but it should work.

 

[bmac2]

I got the crank and piston rod screws done, these are straight forward turning made from the drawings. Then slotted them with a Dermal cut off wheel

 

[bmac2]

I’m using a ring around the ring gear for 2 reasons, one it gives me a way to mount the gear and 2 it simplifies things immensely by keeping as many of the dimensions as possible the same as in Elmer’s original drawings. As things normally go I need something 2 in. in diameter and all I have at hand is the 3 ½ in. I used for the flywheel.

After a bit of scratching lines and procrastinating I faced off the blank, and reamed a .25 hole in the center. Then using a piece of drill rod I aligned the bearing mount on the blank and used a transfer punch to mark the positions of the mounting holes.

Back on the lathe I took the outside down and started boring it out.

 

[bmac2]

That done it was time for some major cleanup. I was ready to hall it out to the bin when my wife spotted it. She thinks she’s found where the “tree rat” (pronounced Squirrel) has been getting under the garden shed and was off to fill in the hole with aluminum shavings.

 

[bmac2]

The gear looks to be MIM (https://en.wikipedia.org/wiki/Metal_injection_molding) and feels very hard with 4 tabs that are not evenly spaced. After some layout I broached 4 shallow notches and parted off the ring. This turned out pretty good and the gear is a firm press fit into the ring.