Arnold's take on the MEM Corliss

[ths]

Nice going Arnold. I guess you're not at the extent of the lathe until you can't do it. I think you were nearly there though!  Cheers, Hugh.

[Ginger Nut]

Sticking my nose in so I know where to come back to to watch the masters.

[arnoldb]

Eric, Jo, Vince, Don, Hugh & Ginger Nut - thanks very much for checking in 
Neat tips Jo  - I have all the needed original bits for the Myford, including some rare additions (I absolutely love the clutch  )  For this project I think I'm sorted, but I'll keep your suggestions in mind 

Ginger Nut, no master here; just an amateur sharing trials and tribulations and very much also still learning along the way.

Some more slow & steady work yesterday.  There's still not much to show for it, but I'll do it anyway 

I've never had much success using carbide tipped tooling on the Myford, but to try and speed things up a bit, I decided to give the one insert boring bar I have a go.  Much to my surprise, it ended up giving a good finish, as long as I didn't try and take more than 5 thou feed at a time (that's 10 thou off the diameter) at highest back-gear speed.  With sharply honed HSS bits, I could go at 10 thou feed at medium back-gear speed, but the finish was worse.  So cuts ended up taking about the same time for both types of toolbits for the same amount of metal removal, but with the carbide giving me a better finish, I stuck to that.

I bored out the rim to meet up with the previously thinned out section at the headstock end.  It's always nice to see two separate bores that have to meet up at the same size do so very nicely after spending a minute or three really trying to clock up things as close as possible.  There is the tiniest bit of eccentricity, but I can't even feel that with my finger, and only the "line" in the cutting fluid gives it away:


The rim section is 32mm wide, and I want the insert section to be 10mm wide, so I bored out another section 21mm long 0.1mm over size to leave a ring for the insert section to seat against, using a long-travel dial indicator mounted on the bed to get the correct depth:


Once the flywheel is complete, this difference would not be noticeable to most people, and, in fact, I can still compensate for it at a later stage:


Back to the band saw, and a slightly revised clamping set-up:


I got myself a cup of coffee, and settled down to letting the saw do its bit; stopping each time the top blade guard bottomed out on the workpiece, turning the workpiece a couple of degrees (about 20^o in this case for each step), re-clamp, and repeat.  The coffee was long-gone at the 75% mark when the familiar snap sound let me know the blade had broken.  I've drooled over the nice bi-metal blades available to people overseas, but locally I can just get the cheap carbon steel blades.  Fortunately, they are cheap, so I always keep at least two spare in stock.  So, I replaced the blade and let it carry on.  The new blade made things a bit faster, and soon I got to see how closely the cuts would meet up:

Far from perfection, but close enough, and I didn't have to hack away at it like when I cut off the rim section  .  On doing what I thought to be the second-to-last cut, the workpiece unexpectedly separated from the parent stock.  Dropped right on my toes before I could get my foot out of the way.  Fortunately it didn't hurt at all - there's something to be said for steel capped safety boots besides that they are very comfy 

The two pieces after separation; the cut still looks like a dog's breakfast, but certainly better than last time around:

  Don't know where the saying "Looks like a dog's breakfast" comes from...  my mutts actually have higher expectations 

Anyhow, that bit was roughly chucked up on the lathe - by eye only, as there was absolutely no reliable references to take readings off, and then I faced it and turned the OD to get two reference surfaces:


The workpiece was then turned around and clocked up in the 4-jaw chuck again - using the faced end against the chuck jaw faces to seat it against, and the rim section within about 0.005mm eccentricity.  I wanted the rim fairly accurate, as it would be reversed in the chuck for a later operation and be clocked up closely again.  Then the inside was bored out till it was cleaned up - but not all the way to boring into the chuck jaws.  As the workpiece was still a bit long, the rest will get removed while facing off later:


I noticed some interesting things while clocking up the workpiece again...  I had some issues... I couldn't get consistent readings on the dial indicator.  After looking at what was happening, I eventually came to the conclusion that the workpiece was distorting while tightening up the chuck jaws.  I got closer readings at each jaw mount than in between them.  Maybe I was just too ham-fisted ?

  Should have taken a video of that lot....  I settled for an average reading between the low and high points.

The ring was faced off to length, and the ridge that was left during the last operation disappeared:


I stopped there for the day; I only have a rim to show for a lot of turning work:


And of course, Swarf Mountain  :


Kind regards, Arnold

[vcutajar]

Coming along nicely Arnold.  I know the feeling;  a whole day machining and nothing to show for it.  Good thing my flywheel is finished.

Vince

[arnoldb]

Thanks Vince. At least there's more to show for today 

With the inner rim coming along , I had a bit of a think about the steps to come.  It would be easiest if I could assemble the inside bits of the flywheel with the inner rim mounted up ready to turn of spoke excess without having to move the whole lot in between - sounds a bit funny, but the rest of the post will hopefully clarify that.

So first I re-mounted the rim on the ends of the jaws in the 4-jaw chuck, once again carefully clocking it to run as true as possible on the chuck.  Using this set-up, I can later on add the spokes and hubs without any of the jaws interfering and without taking the ring off the chuck.  Then I turned the OD down some more, but still left it about 1mm oversize for later machining:


I took the chuck off the lathe with the ring still mounted, very carefully so as not to bump anything and put it down out of the way.  I chucked up a bit of 30mm hot rolled steel in the 3-jaw and started turning it down to make the hub.  I've mentioned a lot in the past that this specific steel is horrible stuff to turn to an acceptable finish...  Well, I think I learned something while juggling the the big rim; sometimes less is more.  Lower speed, and a reduced depth of cut, and I got a finish from it that in the past took the application of a lot of filing and sanding.  Still not the same finish as I can get in other metals, but progress  :


Turning a boss on the end of that was easy, and then I drilled a 7mm hole through the needed length.  This hole is 1mm under-sized - the crankshaft is 8mm in my build, but I'll bore the hole out to 8mm later on in the build.  It leaves enough space to start boring, but enough "meat" to ensure a good concentric shaft hole to make the flywheel run nice and true, even if some minor miss-alignments occur later on.  I installed the dividing head on the mill and transferred the chuck to it.  I used the edge finder and DRO to locate the center of the workpiece, as well as the edge on the end.  From "experience" I know that cross-drilling items mounted like this a bit further out from where the dividing head is mounted in the vise can make it tip or flex enough that alignment is lost.  So I devised an impromptu screw-jack for support from some bits from the clamping kit.  Crude, but effective:

You might just notice the "safe" location I stored the 4-jaw chuck and ring...

My dividing head has a 60 tooth worm wheel, so to get the eight spoke locations I have to index it around 7.5 turns for each location.  That's easily done on any even-numbered hole circle, so I chose a convenient one (38 holes) and set the fingers to reflect the half-turn.  Could just as well have used a permanent marker to mark the two opposing holes, but I've gotten used to using the index fingers. 

Then I set up a little "to-do" list consisting of: "1) Remove screw-jack.  2) Index to next hole location.  3) Spot drill hole location.  4) Drill 4.2mm hole ~8mm deep with drop of cutting oil.  5) Drill 5mm hole ~1mm deep.  6) Put mill gearbox in "neutral".  7) Chuck up M5 taper tap, add drop of tapping fluid and tap hole using quill feed arm to apply light positive pressure, turning chuck by hand till it just tightens at the bottom of the hole.  8 ) Chuck up M5 bottoming tap, and follow same steps as for #7, but take care when starting the thread so that it engages the previous thread.  9) Repeat".
The "to-do" list worked well - even though it is usually frowned upon to chuck up taps in a drill chuck for tapping  .  I really need to make some tap guides to supplement the tailstock die holders.  The plans don't show detail on how to actually hold the flywheel to the crankshaft.  That's left to each builder's own preference.  I decided on two M3 grub screws (set screws for those in the USA).  It's not the neatest solution, and I don't know how the 12" to the foot engines' flywheels were secured, but it's worked for me in the past.  Even a small deviation caused by a single grub screw can make the flywheel wobble, so I settled for two in-line - so that they apply clamping force in the same direction.  As long as the bore in the hub is true and a good fit to the crankshaft, this should give the best results IMHO.  Unfortunately, after drilling and threading the first grub screw hole, I had a brilliantly stupid moment. The first hole was offset 6mm from the hub center line, and I went and spotted the second one at 8mm offset  .  After re-spotting it at the wanted 6mm offset and drilling and tapping, I had this less-than remarkable lot:

  Re-make the hub or recover from the boo-boo ? - I decided on recover...

Seeing as the rotary table was set up, I also finished off the inner hub - much simpler to-do: "1)index to location.  2) Spot drill.  3) Drill 5mm. 4) Repeat".  It was close enough to the dividing head's mounting in the mill vise that it wouldn't move easily, hence no support from a screw-jack needed, as long as I didn't get too heavy on the drilling feed:


I then spent some more time turning the hub.  To make the boo-boo I made earlier on "go away" I turned another step on the hub to clear it.  Then I sawed it off slightly over-length, re-chucked and turned a mirror image on the other side:


The completed hub - without any additional filing/emery work or anything.  Not brilliant, but shiny as-turned, and even if not quite to plan, I'm a happy chappy with the result:


Next I sawed some ~80mm long lengths of a bit of 5mm diameter silver steel rod.  I'd have preferred to use ordinary steel rod for this; the silver steel is a bit of a waste, but I had the silver steel in stock and not something cheaper.  One end of each section was threaded M5 with the tailstock die holder, and to clean the inevitable "raised"  section left after threading, I used a small file to remove the burr on each workpiece:


A test-fit in the hub, and things looked OK:


So I decided to assemble the lot...  With the hub supported by the tailstock, the spokes were screwed in - with retainer added to both the threads and the bits going through the rim.  I supported the hub on most of the un-fluted section of the 7mm drill chucked up in the tailstock chuck.  Things went together very well with copious amounts of thread retainer mixed in, and each spoke tightened down with a pair of pliers.  I'll let that lot "Go off" to paraphrase our U.K. kin. :


Hopefully more next weekend...

Kind regards, Arnold

[Don1966]

Nice save and nice set up. Your moving along pretty good Arnold. Even though you spent a whole day on the flywheel thats still good progress. Your dividing attachment, is it a myford orginal or built one? Just curious, looking at it seems to be the old style VDH.

Don

[vcutajar]

I already see a very nice flywheel. 

Good save there with the hub by making that step.  Actually you made it to plan because there was a step in the plans.

I have been thinking of how to fix the flywheel to the shaft.  I am trying to avoid if possible grub screws.

even though it is usually frowned upon to chuck up taps in a drill chuck for tapping

Don't worry Arnold, I do that all the time.

Vince

[Jo]

Looking better every time I see it Arnold 

The otherway to attach the Flywheel is to key it "on to" the shaft. My S&P flywheel is attached using a saddle key that does not actually go into a groove in the crankshaft but that follows the radius, then the outer edge is tapered so that when it is tapped home it tightens the flywheel onto the shaft 

Jo

[Maryak]

Arnold,

Great Flywheel 

Generally speaking Flywheels are keyed to shafts, sometimes with a Woodruff key, sometimes with a blind keyway in the shaft and sometime with a through keyway from the outside of the shaft to the back of the wheel hub and a gib type key. With the exception of the gib key some form of axial locking of the wheel is still required. IMHO a couple of grub screws is an effective way of achieving both on model engines, especially if the screw locates on a bit more than a dimple in the shaft.

Best Regards
Bob

[b.lindsey]

Nice save on the hub Arnold. And the spokes look terrific. Should make for a beautiful flywheel indeed!!

Bill

[arnoldb]

Thanks for checking in all 

Don, the dividing head is a Myford original - with it's tailstock and the two standard supplied plates.  Seems like the new ones haven't changed much - Myford Website, but I nearly had a coronary when checking the price for the additional plates - I only have number 1 and 2, but on occasion the other two would have been handy.  At some point I'll get some bits of plate and start making up the missing ones; I have a mad idea that there might just be a use for old CD's to make templates to in turn generate fairly accurate home-brew dividing plates 

Vince, it does have a step in the plans - mine now has an extra step - we'll call it "customisation".  I was also not too keen on using the grub screws; should have asked first 

Jo, Bob, thanks for the ideas for mounting flywheels  
I'll mill some flats on the crankshaft later on for the grub screws to have a better seat - but that have to wait for the base to get sorted out so I can get the correct location on the crankshaft.

Kind regards, Arnold

[ozzie46]

Way to go on the hub recovery Arnold.  Neat fly wheel.

 Ron

[Tennessee Whiskey]

If I may pose a question on the flywheel attaching. Back when I was working in one of my Dad's millwright crews we installed couplings on pumps and motors. They were all keyed,but, they were all shrink fitted, I guess thats what it's called, we called it sweating on a coupling. For what our engines do, would this type of fitting not be strong enough? I know if you were the unlucky soul that stuck one before you reached depth it was pure Hell getting it off. Just wondering

Eric

[Captain Jerry]

Arnold

Nice job with the spokes.  I have done it in my head many times but even there, it doesn't come out as good as yours. As has been said, these big flywheels were usually fitted to the shaft with keys, and on very large ones as many as four keys were used.  On I.C. engines, a key is necessary, even on small models engines, to handle the impact loading of combustion.  On a slow revving steam/air engine there is a much smoother power stroke.  Grub screws (always on flats) should do the job just fine.  If the screws are not seated on flats, the small scar that they put on the shaft surface may make it near impossible to remove. DAMHIK!

Jerry

[larry1]

Arnold,  Great job,  Truly like to see you work, you make it look so easy.        larry1