Elmer Engine Number 14 - Wobble Plate

[propforward]

Thanks Fellas, I really appreciate the input. I'll do exactly that on the jaw guards.

There's as much work making jigs, fixtures, tools and accessories in this hobby as there is in making the actual engines. Yesterday I had to make some simple small V blocks for holding small diameter components. It is all part of the fun and interest.

[propforward]

A few more hours in the shop today - and a bit more progress. It was a case of one step forward, one step back, then two steps forward. A bit frustrating, but that's the way it goes.

I made the lever arm pivot today, but it took me two attempts. I won't show pictures of how badly the first one turned out, but it was a real mess. After wasting time on that, I took a breather, and instead of machining installed my coolant reservoir and pump on my lathe. Didn't take long, but I had to make a hole and install a hose fitting in the chip tray. That gave me just the breather I needed to gather my thoughts and try again.

First time I made the pivot, I used aluminum. The second time, I used brass. Only because I had decided that having the brass pivot would add a little more contrast to the engine when finished.

This is pretty obvious, but it's an easy step to short cut, and do yourself a disservice, especially as a novice like me. I have made too many scrap parts lately, so now I have started by sketching the part I am making up on my whiteboard, and writing the steps I intend to take. This helps me think through the part before I start.



So I took my piece of brass, and first of all got it nicely squared up in the lathe, then transferred it to the mill, where I used an edge finder to locate the part.



Then I milled the sides away to form the "upside down T" shape





Then I mounted a center drill and spot faced the part for the two mounting holes.



Then drilled the holes out



After that I turned the part round in the milling vise, and spot faced the three pivot hole positions



Then drilled those out.

Then I set up the slitting saw, and made the slit for the lever arm.



After that I removed the part from the vise, and transferred to the lathe. I chose to machine this component from an over length piece of bar stock, just to have plenty of material to hold. So after making the holes and doing the bulk of the machining, I used the lathe to part the component off, leaving extra material, and then finished the part to size in the milling machine.



This worked out quite well.



It is not perfect - but it is reasonable. As usual, it is set up and checking everything is square and true that I need to focus on. Getting the basics right makes for a better part. So I am more and more forcing myself to slow down at the start, not just jump in, and this is leading to better parts, with better finishes.

I should get back to the shed next weekend, and keep this going.

[b.lindsey]

Well that second one turned out just fine Prop. You shouldn't have too many more bits to make at this point!  I think you are really going to enjoy watching this one run!!

Bill

[propforward]

Thanks Bill, it's great to have you following along.

All I have left now is the lever arm, and 3 pins (valve pin, lever pivot pin, piston pin), flywheel and input tube for the steam (or more likely compressed air). I also have to solder the cylinder head and wobble plate assemblies. Then it's a case of polish it up, assemble and test.

In order to solder the wobble plate I need a jig. I had hoped to make that today, but having two goes at the lever pivot block put paid to that. 

[sshire]

As to planning before cutting, that's exactly what I do. If there are more than a few operations, I do write them down. This generally prevents me from "painting myself into a corner." It's usually something like removing something that I need to hold the part for the next step. I'll even do the part in my head to see if I can pick up any problems. I too had to learn to slow down. Keep at it.

[propforward]

Well, moving right along now - I managed to get a few more hours in the shop. It was supposed to be two days - in which case i would have had this finished - but things conspired to prevent that.

Anyway - I set up my wobble plate and hub with a 1/8" spacer to hold the plate, and soldered the plate into position.





Looks messy, but cleaned up just fine.





Although the errant blob of solder is a bit annoying. I should be able to polish that off though.

I also set up the cylinder and head assembly



And soldered that



It still needs a bit more cleanup, but is looking OK. I don't have a pic of the cleaned up assembly at the moment.

I started making the pivot pin for the lever arm



And also started on the lever arm itself.

Marking up:



And spot drilling the holes



As well as that, I started work on the flywheel. I faced one side, and then set the wheel up for a 45° tapped hole for a set screw to lock it to a shaft.





That's as far as I got today. So close now.........

[b.lindsey]

Great update prop. Yes you are so close now. I predict a runner very soon!!

Bill

[zeeprogrammer]

I think that wobble plate looks great.
It always amazes me how things clean up.

But you make me feel ashamed too. My clamping kit looks pretty messy. I guess it's time to do some deep cleaning. 

[sshire]

Prop
It's really coming together. The bits completed so far look great. Looks like a winner.

Zee
What is it you do with your clamps that require deep cleaning? 

[propforward]

I soooooooooooooo wish I could have had all weekend in the shoppe, I'd have this finished. Not to worry - nearly there. I have brought most of the parts away with me to start clean up for assembly, so once the lever arm and flywheel are finished I can put it together and test it. 

And, er, the reason my clamp set is so clean is that it hasn't had nearly enough use. Must get more shop time in. 

[propforward]

So let me ask this - or rather let me describe my sequence for machining the flywheel, and then ask - does that sound right? Or do you use a different method?

1. Hold flywheel on the cast OD in the lathe chuck.
2. Face off front edge of hub and outer wheel.
3. Center drill and drill / bore hub
4. Drill and tap set screw thread into hub.
5. Mount flywheel on a shaft.
6. Use the shaft to hold the flywheel in the lathe chuck.
7. Machine OD of flywheel to size
8. Face off / clean up hub and wheel faces.

Is this how you go about it? I can't see another way of holding the flywheel so that you can get a nice, clean, uniform finish across the OD. On some flywheels where the hub is a large size and gives you some good material to hold that is possible of course.

Any other tricks?

[b.lindsey]

Prop, the problem with holding the flywheel on a shaft is that it isn't rigid enough and you are likely to get some chattering when cutting the OD of the flywheel. Your first three steps are fine but I would suggest turning the underside of the rim while everything is still square in the lathe so it will be concentric with the hub/bore. This then gives you an ID surface to chuck on once you turn the flywheel around. If the bore is still concentric with the lathe axis using the three jaw chuck then fine. If not you may have to use the 4 jaw and an indicator to get the bore centered with the lathe axis. Then you can turn the OD of the flywheel with a more rigid setup. I would also suggest tailstock support since you may not have a lot of surface are to chuck on (depth) but even so this will be much more rigid IMHO than mounting the flywheel on a rather small shaft.

Bill

[propforward]

Ah yes, OK, makes complete sense. Thanks Bill, I'll do that.

This wheel has a fair bit of material to get jaws in to hold the inside of the rim - I see now that that will work very well.

Looks like I'll get to practice with my 4 jaw and center finder again!   

EDIT: I also just found a nice article by Marv from his website, with some good advice.

I intend to move on to a casting kit after this engine is finished - and the reason for adding this (somewhat oversized) casting to this bar stock engine, is simply as a first look at castings and the additional work / different techniques required to work with them.

[mklotz]

I'm with Bill...machining a wheel held on a shaft can lead to chatter. 

If you're comfortable with holding it by the inside of the rim then go with that.  In cases where you might not feel good about doing that an alternate approach is to clamp the partially machined wheel to a chunk of stuff using straps over the spokes and leaving the rim exposed.  Clamp the chunk in the 4jaw and get the wheel bore running true, then machine the rim.

What article of mine did you find?  The one about centering stuff in the 4jaw?

[propforward]

What article of mine did you find?  The one about centering stuff in the 4jaw?

This one

http://www.schsm.org/html/machining_small_castings.html

In it you describe the approach that you mentioned above.

I like both approaches. When I am back in the shop I'll see which seems most appropriate.