Engines > From Kits/Castings
PMR #1 Drilling Engine - Mike's 4th Engine
mikehinz:
After a bit of a gap in posting due to various personal issues, I'm back and I hope to make steady progress on this project as well as the Webster!
I'll make 2 posts today, first regarding the flywheel and the second regarding other bits of the engine that I've been working on.
First up is some fine flywheel fettling! I used the belt sander on rim OD to knock down some flashing and to smooth up the seam a bit and then went over to the vise and removed the flashing from the spokes and from inside the rim. Shown is the collection of files that I ended up using.
The next thing that I discovered is that Jo was absolutely correct. My 4J could not grip the inside of the rim due to the spoke placement and the size of the jaws. Jasonb did give me a clue and that was 'faceplate'. Shown is the flywheel laid on top of the faceplate that came with my lathe. The faceplate is 10" diameter and that leads to the next problem. There's no way to directly hold the flywheel to the faceplate due to the respective sizes!
So what I ended up doing was as follows. I have a tooling plate that I used on my 6" rotary table. I took that and drilled 4 more mounting holes that allowed me to mount the tooling plate on the faceplate.
Also in the pix is shown how I propose to hold the flywheel to the tooling plate. The holes in the tooling plate are tapped 3/8"-16 which is commonly used for hold downs for 7/16" and 1/2" slotted tables. I took 4 pieces of 3/8" flat AL stock and cut them to 1" x 3.5" and drilled a thru hole thru the center of each of the bit of the AL packing material. That way I can catch 4 of the spokes and hopefully secure the flywheel well enough to take some light cuts on the first side and get the hole drilled and reamed thru the center. It's a little hard to see on the pix, but the AL packing does clear the ID of the rim.
So does everyone think that this approach will work OK? Is this method secure enough to hold the flywheel for some light operations? All input is certainly welcome!
I'll have another post in a bit.
Enjoy!
Mike
mikehinz:
This post is regarding various parts in various stages of progress. My high-level plan is to do the base of the engine first as many other parts need to be fitted to it during the construction. Of course I soon realized that I need various other parts to check if the base is correct in the first place. In any case, here's the tale.
I spend some time on this collection of parts with the belt grinder and files. My goal was just to remove most of the flashing so as to allow easier holding on lathe and mill. Also most of these parts will need to be fitted to the base fairly early in the build.
Based on Bill L's posts regarding this engine, there's a possible issue when establishing the height of the crosshead slides vs the centerline of the cylinder vs the top of the frame matching the top of the cylinder. So I spent a bit of time with the height gage looking at the frame and figuring out how much I could mill away on the frame crossline bottom guides. I'll spare everyone the math but I believe I need to mill away about .055" from the top of the crosshead slide guides so as to make the centerline of the cylinder end up in the correct spot. My assumption was that the top of the frame (where the cylinder is bolted up) won't have any material removed (other than a bit of filing for smoothing) and hence will be used to establish the centerline. Note my old Starrett 254 Master height gage. Its a great old instrument but the older I get, the harder it gets to read accurately even thought its about as easy to read as any vernier instrument. One of these days I'll probably trade it for a digital just to be able read it!
Then on to milling the bearing caps flat. More work to do down the road but this gets them started. That's the old CentreDex insert end mill. Still works good on CI!
Both of the caps laying on the print. Both are flat and are to width. I still have to put the 'step' in each of them.
After a bit of contemplation and reading other threads on this build, I came to the conclusion that I needed a tooling plate to hold the base of the engine for the various options that needed to be done. This pix shows a piece of .75" AL that cut to size and flycut smooth on both sides. I'm just contemplating if this will work and where the hold-downs should be placed.
This pix will make more sense in a bit, but here I have the engine base bolted to the tooling plate in a couple of places and I'm making sure that the engine base is as close aligned with the X axis as I can make it, given that it's a rough casting.
After I got it aligned as best I could, I used a 1/4" extended length end mill to make the 6 areas where the base bolts will go as flat as possible.
Shown after I had all the bolt-down areas milled flat.
Drilling thru each flat area with a 1/8" drill as per the drawing. It was a bit challenging to get the hole in the center as it has to be done pretty much by eye and I'm not that great at that job, but the holes ended up close enough, I think. I may use a small brass washer under each bolt just hide my sins!
After the thru holes were drilled in the base, I removed it and then drilled and tapped 4-40 at 6 places based on the dimple from the thru drilling operation. You can see the 3/8-16 drilled and tapped holes for the hold down hardware. Plus I lightly scribed lines around the engine base so that i could get it back into place as closely as possible.
And here's the engine base screwed down to the tooling plate in the final position that I chose. I plan to leave it screwed down as shown plus add up to 3 additional hold downs depending on the operation I'm doing and the need for clearance. Hopefully this will be rigid enough for all the operations needed.
I decided to try to use the casting for the crankshaft vs a built-up crankshaft, mostly since I want to see if i can do it this way.
First, i wanted to get center holes into each end of the crankshaft casting. As you can see the crankshaft will go entirely thru the center of my 4J so I shoved it thru.
Then I tightened the 4J on the crankshaft and centered it up as closely as possible as shown.
Then faced the end off flat.
Then center drilled each end.
That pretty much catches me up with progress pix. I'll keep working on the base and crankshaft assembly as well as the parts that need to be fitted to the base.
All for now.
Enjoy!
Mike
b.lindsey:
You are making some good progress Mike. Good to see an update on this one.
Bill
mikehinz:
This reply originally was about the failure of the spindle adapter on the collet closer on my lathe. Rather than posting only indirectly related info in this build thread, I've started a new topic in 'Supporting / Tools & Machine'. I'll post anything relating to the failure, part design, and hopefully eventual repair in that thread.
For convenience, the lathe repair thread is linked below.
http://www.modelenginemaker.com/index.php?topic=8867.new#new
FYI.
Mike
MJM460:
I share your sorrow, Mile, I use my collets a lot too. (But just a manual drawbar closer.)
Hard to believe a manufacturer turned that bore with so little clearance, I wonder if the previous owner wanted to use a larger bar and had to skim it out.
Will be interested in how you go in the thread cutting for the replacement. Please keep posting. Keeping the lathe in operation is surely relevant to the build.
While on the topic, I often wonder just how much solid metal you have to leave between a thread and a hole through the centre. Clearly the root diameter is less than the tapping drill size, can be calculated, but what about any micro cracking from the threading process? And it has to be strong enough to take the torque from the thread cutting or hole boring process. One of those design decisions that always leaves me scratching my head.
MJM460
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