Chris's Marion 91 Steam Shovel

[ddmckee54]

You might want to check their time-sheets.  I'll bet they REALLY took the sharpening firm' name andwere "on the clock" while they waited for the chisels to be sharpened.  If they were, be sure you get the union steward involved - don't want them to file any grievances on you.

Don

[crueby]

You might want to check their time-sheets.  I'll bet they REALLY took the sharpening firm' name andwere "on the clock" while they waited for the chisels to be sharpened.  If they were, be sure you get the union steward involved - don't want them to file any grievances on you.

Don

Those....

[steamboatmodel]

Hi Chris, I wondered whether the broach tool would be adaptable to the smaller engine as soon as I saw your 3D printed model pic. Through the side on the smaller one will likely be far less involved. Good luck with the detail dimensions today. Hope the elves don't get miffed about the thicker webs. Must be an eye-straining job sharpening all those tiny cold chisels every day while they hand carve out a crank from solid ....

The side of the recess is so thin that it will be quicker to just cut through and cover it with some shim stock, though the broach setup would work as well.
The elves got hold of my credit card and started sending the chisels out to Sharpen-While-U-Wait till I saw the next bill....      Lazy little swarf-heads!   

Chris you have big problems with your Elves, while having coffee and cookies with the Big Guy he warned me about "Sharpen-While-U-Wait " , It is a gambling joint.  "Sharpem" is an old elfin gambling game played with cards (two decks), eight sided dice (3 sets in 3 colours) and knuckle bones. I tried to get my Elves to show me and we played the kids version (no knives or hammers allowed), within 20 minute I owed them $45 each (three players), I quit then and checked my credit cards.
Gerald.
PS they actually do sharpen tools while they play, but they are expensive, they bill you for the Band-Aids used.

[ddmckee54]

Are you SURE some of your shop elves haven't devolved into shop Gnomes?

Better watch your back, and maybe even start packin' some heat when you go in the shop - you never can tell.

Don

[crueby]

Love to be there when someone new to the site gets to these kinds of posts... 

[cnr6400]

When I first got onto this site a flak jacket and sidearm was not yet required......

Maybe things were under control with the elves a bit better in egg nog season with the rum ration. Now they are into the summer and the cold ones, how's the pile of empties under the ash chute piling up? 

[crueby]

When I first got onto this site a flak jacket and sidearm was not yet required......

Maybe things were under control with the elves a bit better in egg nog season with the rum ration. Now they are into the summer and the cold ones, how's the pile of empties under the ash chute piling up? 

Fortunately the shop vac cleans up thier empties quickly.

[crueby]

All right - on to the last subassembly for the Marion 91 model!   

To start the steering engine, cut a length of 1144 stressproof steel bar to the length of the crankshaft, plus 5/8" on each end for holding with the drive dog. Chucked that up in the lathe, trimmed the ends square, and center drilled the middle for the lathe centers. Then moved the part over to a 5/8" collet in the square holder, centered it in the mill with the collet holder indexed at the edge of the vise, and drilled two more holes, on the centers of the crankshaft pins.

Then, keeping track of which way I was turning the collet holder, turned it upside down, checked that the center hole was still centered on the mill head, and drilled the matching holes at that end. Since I had rotated the vise left/right, the hole on the right on the first end is now on the left, so moved that direction for that hole.


That gives me lathe center holes for the main shaft and also the crank pins, but not for the eccentrics - the distance of the eccentric offset is too small, and would overlap the center hole too much. So, the eccentric offsets will have to be done with the 4-jaw chuck, or maybe will trim off the ends and drill a new set of holes.
So, with the first sets of holes in the ends drilled, time to start turning down the crankshaft. First went up to the grinder and sharpened the parting tool on the fine wheel (thanks for the reminder Bob! ), and got the first pin turned in:

The 1144 turns very nicely, with no warpage - nice stuff to work with. Now, I will glue in a spacer for the gap and let that cure up, then I can cut the second pin without worrying about the part flexing at the gap...

[Stuart]

Now that’s a cunning plan   

[crueby]

Thanks Stuart!  All these methods I learned from others, with gratitude!

Second pin turned in, using the second set of holes in the ends:

Glued in another bit of brass in that slot, and setting up for turning the eccentrics. Took a look at redoing the end holes and at the 4-jaw, and it turns out that for this smaller crankshaft the blank fits into the center hole of the 4-jaw with plenty to spare, so I got out the dial indicator and centered the shaft, holding it at one end with the space for the eccentric just outside the jaws. The pin at that end was centered on one of the jaws, and then the two jaws opposite that one were offset to find the center of the eccentric, using the indicator to get the distance correct. Also checked that the center had not moved in the other direction when re-tightening the chuck.

So, the part is all set up and ready to turn in the first eccentric. First, a read/nap out on the porch, and touch up the sharpness on the parting tool in case all those interrupted cuts dulled it any (I leave the fine-grit wheel on the grinder set up with the support at the right distance/angle for this since it needs doing so often - its a slower speed grinder (800 rpm?) so it does not heat up the cutter much, and frequent dunking the tool tip in water keeps even that heat away - coup[le light passes on the wheel and its back sharp).

[crueby]

This evening saw the rest of the bearing surfaces turned to shape, went easier than I expected, partly being smaller there was less time needed per slot than on the other engines. I showed the setup for the eccentric cams in the last post, so this evening cut the first cam:

As with the other engines, I am putting a slot in the center of the cams for a ridge in the center of the followers to, follow. With that one done, carefully turned the part around and gripped the other end, lined it up with the angle from the crank pin, triple checked it about 4 times, and cut that cam as well:

Now, you will notice on this second cam that I did not bother with a spacer like I did for the crank pins - the cams span across the center of the part, so the tailstock center is pushing down the length of the part through both cam positions, so no need for any extra support.
Then set it up with the three-jaw chuck holding one end, and supported by the live center at the other, and turned down the first side shaft to size:

The very end is still tapered a bit, the tool would no go out to the end with the center in place, but that is why I left extra length on the bar at the beginning, that end section will be cut off. Then, you guessed it, turned it around and did the other end...

Pulled the part from the chuck, popped out the brass blocks, and we have a functional but not quite finished crankshaft:

You can see some of the superglue residue in the slots, that will be scraped out, then will set up to cut the crank webs to shape, as well as the center section. Surprised that all that was done in a few hours of shop time, I guess pertice does make prefect.. I mean parktise marks perfeect... Practice Makes Perfect! Yeah, thats it!   And not perfect, but looks good, and measurements are all working out so far.
 

[gbritnell]

Excellent crank work Chris. I wonder why more people don't try this method. To me it's easier than fiddling around trying to make a crank from pieces.
gbritnell

[cnr6400]

 

[crueby]

Excellent crank work Chris. I wonder why more people don't try this method. To me it's easier than fiddling around trying to make a crank from pieces.
gbritnell

These cranks are the first time I've done them from one piece, all my others were built up. Couple of reasons in my case, looking back:

- did not know about 1144 stressproof then, other metals had warpage issues- inexperience with the parting tool, especially with interrupted cuts, put me off

- larger cranks on some models would have meant removing a LOT of metal deep into a cut with the parting tool extended out, problem on small lathe. My model of the MEM Corliss twin would have started with a massive piece of steel, lots to remove for a 15" long crankshaft with two throws

- long crank means needing tall clearance on mill to drill end holes - on my twin corliss I could not have done it with my mill.

- just being intimidated by the procedures shown in books for this as a beginner

[crueby]

Too hot to be outside this afternoon, so went back into the shop and milled off the crank webs from the raw round bar. Started by putting a spacer back in one end, and gripped the part in the collet block again to mill off the center section flats.

Marked out the diagonals in the center section, where it connects the two crank pins.


Can't get into that area with an end mill without hitting the webs, so took off the bulk with a hacksaw, will finish it off by hand.


Then put the rotary table up on the vertical stand, held the part in the 3-jaw vise, and milled off the excess from the crank webs. Did just the one closest to the vise, then turned the part around to do the other end.

Here is the crankshaft so far, ready for filing to clean up the center sections and smooth off the corners of the webs.

So far so good!