# Machining flywheel "windows" with rotary table on mill



## Brian Rupnow (Oct 21, 2008)

At some point later today I will be doing my first set-up on the rotary table to machine "windows" in a spoked flywheel. There seem to be a number of ways to do this, one of which is to drill all the corner holes first, in all the windows, then use the rotary table to rotate the part and let an end mill cut arcs between the outer holes and between the inner holes. then traverse the bed to cut the straight sides of the windows. I an exploring a second option that involves drilling fewer holes. Since my flywheels have 6 equally spaced spokes (and 6 equally spaced windows). I an thinking of laying out 6 lines at 60 degrees that all intersect the center. I will set the rotary table up so that the centerline of the rotary table is in line with the quill of the mill, parallel to the right to left axis of the mill. Looking at this from the aspect of one window, I would use a 3/8" diameter endmill to plunge cut the first outer hole on the center of one of these lines, but about 0.030" closer to the center than it should be. Then with the cutter in place, I can move the mill table, thus being able to "sneak up" on a point where the cutter just kisses the inside of the outer rim of the flywheel. Then I can rotate the rotary table, first "x" number of degrees clockwise to cut half the outer arc cutout, then return the rotary table to 'zero" and rotate it "x" number of degrees counterclockwise to cut the other half of the outer arc cut.----I can then rotate the rotary table 60 degrees and do the next window, and keep on doing that untill all the outer slots are cut. The same procedure would be used to cut the inner slots.----Why would I do this---Well, because I like the idea of being able to "sneak up" untill the cutter just kisses the inside of the outer hub and the outside of the inner hub, so that everything stays uniform. If I drill the holes first, that doesn't give me the ability to "sneak up" on those dimensions, and I can see the possibility of getting my holes out of place a bit radially--then the radius cut by the endmill will not be in exactly the same place as the radius which was previously cut on the lathe.---I hope this makes sense.---advice please.--Brian


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## kellswaterri (Oct 21, 2008)

Hi Brian,...your idea seems sound enough to me...though I would suggest a Slot mill cutter to plunge cut rather than an end mill...will be doing something akin to this myself soon.
All the best for now,
              John.


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## kvom (Oct 21, 2008)

I made a 6-spoked flywheel in the past couple of weeks (pics posted in another thread).  Unless you think your mill/rotab are particularly inaccurate I don't see the necessity of sneaking up on either the inner or outer rims, and it will take proportionally longer.

I don't see the necessity to layout the spoke lines; just set your starting angle on the rotab to a multiple of 60 degrees, and doing the rotation math will be simple.

The number of degrees you need to rotate away from the center of each spoke is determined by how you want the spokes to taper. Since you have CAD expertise I imagine you can easily draw the wheel so that the spokes look pleasing to you, and then have the program cakculate the appropriate angles. Similarly, the diameters of the inner and outer holes affect the look as well.


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## SandyC (Oct 21, 2008)

Hi Brian,

Nice idea, however, by only doing half the outer cut in one direction and the other half in the opposite direction (from a table angle rotation point of view) you will be CLIMB milling on one or the other direction.
I would avoid this like the plague.

Better, and safer, to follow the edge of the spoke, from hub to inner rim, and then do the whole outer arc in one direction.

If you get your spoke side angles correct you should be able to cut the whole window using a combination of rotary and linear traversing.
I am sure one of Marv's programs has the calculations for doing this.

Just a thought.

Best regards.

Sandy.


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## Brian Rupnow (Oct 21, 2008)

Sandy--I unserstand the concept of climb milling when one edge of the cutter is in the material and the other side is not. However, forgive my ignorance, but when both edges of the cutter are engaged as when milling a slot, how can it be climb milling?--Brian


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## SandyC (Oct 21, 2008)

Hi Brian,

To clarify..... yes what you say is partially correct, however, if you change the direction of the cut then the forces applied to the cutter will tranfer to the opposite side of the slot, therefore one half will cut on the inside of the slot whilst the other cuts on the outside.

Even a slot drill will cut a slot slightly larger than itself for reasons of this deflection...by reversing the cut direction each half of the slot will have a slightly different radius...leaving a small step at the interchange.

Not a big step, but enough to make final cleaning up a PAIN.

Best regards.

Sandy.


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## Brian Rupnow (Oct 21, 2008)

Okay Sandy--I'm convinced. I will cut all my slots in one direction. Other than that, is the rest of my premise workable?


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## Brian Rupnow (Oct 21, 2008)

kellswaterri  said:
			
		

> Hi Brian,...your idea seems sound enough to me...though I would suggest a Slot mill cutter to plunge cut rather than an end mill...will be doing something akin to this myself soon.
> All the best for now,
> John.


John--nice idea, but I don't have a slot cutter. The material is phospor bronze, which cuts easy, and I am only going thru the web of the flywheel which is 1/4" thick.


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## SandyC (Oct 21, 2008)

Hi Brian,

Please don't think I was trying to be smart, nothing could be further from the truth, just an observation from your proposed plan.

The deflection I refer to is common to all milling and can become a problem.
How much deflection is determined largely by the depth and rate of cut, the dia of the cutter, the type of cutter, the direction of the cut, the material being cut and, above all, the rigidity of the machine/setup.

A slot drill (having only 2 cutting edges) will perform better than an end mill (with it's 4 cutting edges) on this score, but it will still deflect.... yes, even on a large heavy machine.
Try it on some pieces of scrap materials on your own machine, at varying depths of cut, and you will see the result for yourself.
It can be a good way of learning your particular machines characteristics.

Best regards.

Sandy &#160; ;D

BTW, we posted at the same time, so I did not see your last post....... If you don't have a slot drill then don't try plunging with an end mill (unless it is a centre cutting one) drill a smaller hole first and then use the end mill to open it out.


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## Brian Rupnow (Oct 21, 2008)

Sandy--I didn't think you were "being smart". I appreciate your help and suggestions. I am quite new to this entire machining business, and there is a great deal that I truly don't know. Thank you for your help and suggestions.---Brian


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## SandyC (Oct 21, 2008)

;D

Hi Brian,

No problem my friend, just though I would mention it to try and avoid any unneccessary dissapointment for you on your final results.

I have just read your other post thread, and it would appear that your material is one of the free cutting phosphor bronze alloys, such as Colphos 90 or SAE660, both of which have some LEAD added (similar to gunmetal), hence the fine dust like swarf.

Pure phosphor bronze is a lot more copper looking and is horible, sticky stuff to cut.
It would require some sort of cutting fluid and the swarf comes of in long spirals.... a bit like mild steel.

Take your time and your plan should work Ok, other than what we have discussed.
Look forward to seeing the final result.

Best regards.

Sandy.   ;D


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## mklotz (Oct 21, 2008)

I have to agree with KVOM. Given that the part is on an RT, I see no necessity for layout lines or "sneaking up" on said lines.

Drill the six inner holes and then the twelve outer holes. Lock the mill table and lock the RT as each hole is drilled and the holes will be on the same radii to within the accuracy of the RT. Using an endmill slightly smaller than the outer hole diameter, cut the outer arcs. Depending on the mill oomph and the security of the clamping, you may want to make these through cuts in more than one pass. Now, using an endmill of the same diameter as the holes, go back and take a (non-climbcut) pass to finish the outer radius to size. Since you're only removing a small amount of material, the finish should be very good.

Repeat the small endmill - final size endmill sequence on the sides of the spokes to free the six web segments. Be careful when you make the final cut that frees the segment to ensure that it can drop free and not jam between the endmill and the sides of the hole.

Aside: If you're worried about jamming, cut until the waste piece is supported by only a thin web of metal. Then use a small chisel or saw to free the piece by hand. Make a final pass with the endmill to clean up the jagged edge left by the chisel/saw.


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## Brian Rupnow (Oct 21, 2008)

Marv--Obviously you are a far braver soul than me.--Or at least far more comfortable around a rotary table. I do have a rotary table. I have used it exactly once. I will use layout lines, because I am far more sure of my layout work than I am about my ability to use the rotary table correctly. After I have made at least this first set of flywheels without ruining them in the process, I too will tell people-"Rotary table!! Oh Heck Ya, Nothing to it, why, anybody can use one of them!'---For now, I'll stick with my layout lines.


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## mklotz (Oct 21, 2008)

There's nothing wrong with layout lines as a sanity check - I do that myself some times.

Most of my post though addresses the nuances of making the cuts. Keep those points in mind while working - especially the cautions about freeing the web segments.

Another hint for future work: Centerdrill the blanks when you machine the outer rim of the blank. Then you'll have a guaranteed concentric reference for future centering - on the RT or in the lathe when drilling the mounting hole.


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## Cedge (Oct 21, 2008)

Brian
I just cut the curved spokes a few days ago... my first machined flywheel. Being a little hard headed, I ignored a couple of strong hints from the venerable Philip Duclos.... much to my later regrets.

Go ahead and drill the holes. They give you an important fudge factor by providing the cutter an escape. You'll be moving quite a bit of metal, which will require several passes for each cut. Trying to make the cuts in one go will cause cutter deflection which can really ruin your day. The "exit holes" take the worry out of being close at the end of each cut. I did follow Duclos' advice on this one and his advice saved me a whole lot of sweat.

The other tip he gave, that I didn't heed, was to do the cuts in two stages. The first roughing cut should be about 1/64 from the final line you'll want. He gave two reasons for this and they proved to be prophetic. The first is any cutter deflection is pretty much rendered harmless and can be corrected in the clean up cutting session. 

The other reason was the fact that a normal cut presses chips into the metal, creating a rough surface. With a small cut and a relatively stiff setup, one can do light climbing cuts to make nice clean finish surface. I went directly for the finish line and tried to cut to the final finish in one go and wound up with a lot of additional hand filing to do. 

Be careful if you choose to do the climbing cuts. Make sure the work piece is secured well. With a gear driven RT you shouldn't encounter the run away I did when I discovered how to make the S spokes...(grin). 

The one other suggestion that he made that I went along with was to cut the spoke lines first and then cut the outer rim cut last. It proved to be the easiest way.

You've spent a bit of money on the brass.... you don't want to screw it up by getting in any hurry.

Steve


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## cfellows (Oct 21, 2008)

Brian,

I've cut several spoked flywheels from solid, and I agree with your earlier premise. 

Everytime I've tried to cut to the line on first pass, I wind up taking out more than I wanted resulting in skinny or uneven spokes. Maybe I'm just not an accomplished machinist, but I prefer to cut the window out leaving the line, then some, and going back and cleaning up to the line after all windows are first cut out. Takes a little longer, but this always results in a better looking flywheel, for me at least.

Chuck


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## rickharris (Oct 21, 2008)

We teach the kids that there are 5 phases to manufacturing anything:

1. Mark out the parts
2. Cut out the parts
3. finish to size
4. Assemble
5. Test (this may be an interim test or on the final product)

Modern technology using CAD CAM has in some cases reduce the first 3 to a single process although finish to size may well stil be required in the form of a final polish or Bling.

Personally I never try to cut direct to size as I always seem to get it wrong.


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## BobWarfield (Oct 21, 2008)

Modern tech still does the marking out first, it just does it on the CAD screen!  :big:

Even better is to combine the two and paste a life sized CAD drawing onto the rough workpiece. I'll be working with such a piece later today in fact.

The pro machinists among us will know you just can't cut a slot to size in one pass. The cutter deflects and you get a slot that is wider, has walls that aren't perpendicular, and that usually has a wonky finish to boot.

Here is another thought borrowed from the CNC world. Where possible, rather than plunging your cutter, try to lower it while moving one axis or the other so it "ramps" down into the cut. You'll find this is a requirement if your end mill isn't center cutting (so much talk of slot drills from across the pondz--the nomenclature varies), but even if the end mill is of the center cutting variety, I find things go a lot smoother.

As Cedge mentions, you can get a prettier finish with a light cut on one side while climb milling. The latter has the unfortunate risk of sucking the cutting in hard and creating lots of problems (some safety issues too), so you need to be sure of your technique and machine before attempting any climb milling. With a rigid setup, and very light cuts, I find climb milling a very useful tool in my arsenal.

Last thought: if you're comfortable moving the mill table and rotab to precise coordinates, there is still time to taper those spokes! It's a question of lining up the taper line so you can feed along one axis or the other. 

Cheers,

BW


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## Brian Rupnow (Oct 21, 2008)

Having scared myself near to death with inadvertant "climb milling" I don't think I'll be doing that!!! Taking a closer look at what I'm doing here, If I make one "outer" hole, I should then be able to index the rotary table 6 times at 60 degrees to place the 5 other outer outer holes all in one set-up. Then if I go back to my original hole and using it as a "starting point" I should be able to rotate the rotary table 34.07 degrees to pick up the outer hole on the 'other side" of that window, then repeat that 5 more times. Its just that I'm not sure how to get 34.07 degrees on the rotary table. (see circled dim. on drawing)--I just noticed that I left the spoke width off the drawing. The spoke width is 0.27". That being said, If I set the rotary table up so it is not centered on the quill, but is offset half of 0.27" towards the front or back of the mill, I should be able to traverse the table side to side to cut the sides of the spokes on one side of the window.---Shouldn't I??/


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## Cedge (Oct 21, 2008)

Brian
The RT is marked out in degrees, minutes and seconds... here is a converter from decimal to minutes etc

http://id.mind.net/~zona/mmts/trigonometryRealms/degMinSec/degMinSec.htm

Handy little bugger... it is... yessss ( in best Yoda tones)

Steve


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## kvom (Oct 21, 2008)

Regardless of how you make the cuts, it is crucial to get both the RT and the flywheel blank centered over the spindle first.

On mine I centered the RT using a DTI and indicating the inner hole. I was told that this more accurate than using the outer rim of the RT. Zero your dials/DRO once this is done and don't change them until the entire piece is finished.

To center my flywheel on the RT, I first drilled and reamed the center hole. I then mounted a drill or mill of the same size in the spindle, pushed it through the blank center hole, and then lowered the spindle and blank onto the RT where I could clamp it down. You can verify that all is centered by then rotating the wheel around the drill/mill; should be no binding.

For moving the tool to do the cuts, I found using the Y-axis to give better visibility.


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## mklotz (Oct 21, 2008)

Brian,

You've discovered why my FLYWHEEL program produces two solutions. The first is the mathematically correct one given the desired spoke widths. Almost inevitably, this leads to oddball angles between the two outer web holes - as you've discovered. Since exact spoke width is seldom critical, the program then goes on to compute a solution that produces integral spacing between the outer holes at the expense of a slight change in the spoke width.

You can, of course, do this yourself but the math, though trivial, is messy enough to raise the probability of computational error.


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## Cedge (Oct 21, 2008)

Brian
Round off the angle and then cut all tapers on one side only. Flip the flywheel over and cut the other 6 sides. The angles will match and you're head won't hurt...LOL

Steve


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## kvom (Oct 21, 2008)

Assuming your outer hole angle to be rounded to 34 degrees, then the distance between holes across a spoke is 26 degrees.

To make it more "idiot proof", why not set the RT to 0, then make one hole at 13 and another at 347. Then rotate to 60 and make two holes at 73 and 47. And so forth. That's how I did mine, and having the same last digits on each pair of holes was a useful mental checkpoint.

Having all the critical points being even degrees makes everything easier.


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## mklotz (Oct 21, 2008)

kvom  said:
			
		

> To make it more "idiot proof", why not set the RT to 0, then make one hole at 13 and another at 347. Then rotate to 60 and make two holes at 73 and 47. And so forth.



That will work assuming you're not suggesting turning the RT in two directions. To avoid backlash problems you should only turn the RT in one direction. This would suggest a procedure where you make an ordered list of all the holes to be drilled and then drill them in sequence while always rotating the table in one direction.


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## Cedge (Oct 21, 2008)

Kvom...
Stand back... I think his head's about to explode....LOL

Steve


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## Brian Rupnow (Oct 21, 2008)

Good Lord!!!--And I thought "sweating bullets" was only an old wives tale---- I've got the first 6 outer holes in at 60 degrees each. Now if I can just understand the rotary table instructions on how to get a decimal of a degree---


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## CrewCab (Oct 21, 2008)

I think at this stage I'd be taking Marv's earlier suggestion and breaking out a piece of mdf ;D

Good luck Brian ............... you'd best be quick though, don't think we can hold our breath much longer 

CC


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## Cedge (Oct 21, 2008)

Brian
I feel your pain there dude....LOL. It got pretty intense here too. After the fact, it seemed like a lot of worry over something that was much easier than expected. Yeah... I needed a good shower and a stiff drink after that first session too.

Steve


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## rake60 (Oct 21, 2008)

Don't be afraid to be scared Brian! 

As has already been stated here, layout lines on the part are a waste of time.
I always DO the layout thing myself.

Here's a perfect example from my "recycle box"







Lines are in the right places, but those would be some very WIDE spokes.
You'll notice the last two center drilled holes were never drilled.
It's kind of hard to do that when the piece is flying across the shop to the
"That Didn't Go So Well Corner."

Rick


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## mklotz (Oct 21, 2008)

Maybe now you guys can appreciate why I wrote a program to produce a complete cutting schedule for this task.

My first "freehand" attempt to make a spoked flywheel looked remarkably similar to Rick's "recycle box" example box above. Nevertheless, I didn't instantly discard it, as Rick did, but continued machining it to uncover other problems (hence my remark about doing a test piece first). That's why it had a huge gouge mark from where the newly-freed segment jammed between the endmill and the window creating enough torque to move the head on the round-column mill/drill.  Hence my previous cautions about that final cut that frees the scrap piece.

On another note, I just noticed something. Look carefully at Brian's flywheel drawing and the innermost corner of the triangular window. Normally this is formed by drilling a single hole but Brian's drawing shows it developed from two overlapping holes.  If he really intends to build it that way things are going to get a good bit more complicated for him.


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## spuddevans (Oct 21, 2008)

rake60  said:
			
		

> Don't be afraid to be scared Brian!
> 
> As has already been stated here, layout lines on the part are a waste of time.
> I always DO the layout thing myself.
> ...



I hope you dont mind, but looking at your "mistake" made me think of a possible way to recover it.






Just a few mins work in photoshop, imagine that the parts colored that beautiful green are the spokes, it'd make a pretty groovy flywheel. ( although a pig of a flywheel to machine !!! )

Tim


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## Cedge (Oct 21, 2008)

Tim
You have an excellent eye. I'm right in the middle of writing up a post showing how that very same type of flywheel is made. It should be up in another hour or so. 

Steve


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## GailInNM (Oct 21, 2008)

Also to recover, a second set of holes on the outside offset 30 degrees and the offending holes will be milled away when you make the cutouts. Gail in NM,USA


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## spuddevans (Oct 21, 2008)

Cedge  said:
			
		

> Tim
> You have an excellent eye.


Not really, I just like puzzles and also like form that flows, I used to do a lot of woodturning and I think that is where it comes from. Now if only I could make my hands ( and machines ) produce the flowing forms that I can imagine in my head!! :big:


> I'm right in the middle of writing up a post showing how that very same type of flywheel is made. It should be up in another hour or so.
> 
> Steve



Well I really look forward to reading that as I'd love to make a flywheel like that someday.


Tim


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## Brian Rupnow (Oct 21, 2008)

Can you say "Nervous exhaustion'??? So far I have been successful. No, I actually didn't use any layout lines. I had quite a time figuring out just what the heck all the divisions on my rotary table meant, and how many marks represented one minute of arc, but I think I won. I bought a new 2 flute 3/8" endmill for the outer arcs, and found it really "grabby" as I went around the outer arcs. It acted like it was climb milling, and made my whole set up vibrate a couple of times, and like to scared me to death, but nothing broke and nothing bent. I advanced the rotary table in very small increments and held my breath---The flywheel web is 1/4" thick, and I was taking a full depth cut, with the end of the end mill actually extending about 1/8" thru the far side of the web. I am going to go upstairs now and soak my sore feet--they are not used to supporting a fat old man for 8 hours straight. I live my life in my computer chair most of the time, so my old dogs are really barking tonight. Tomorrow I attempt to cut the rest of the windows.


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## Kludge (Oct 21, 2008)

rake60  said:
			
		

> Here's a perfect example from my "recycle box"



Rick, pull that piece back out for some really fancy spokes. I don't quite have it completely visualized but start by drilling a reasonably large hole on a line centered between two smaller ones so it gives a fair web thickness between it and the inner holes and falls just short of the rim. (The rim can be machined smooth later.) Now, mill a curve so that it comes from an outer hole and meets the new hole at a tangent then back down to the little hole on the other side of the new hole making kind of a "pointy end of an egg shape". 

Once they're done and happy, you may be able to drill a really small hole somewhere between the newly milled cutouts just outboard of the inner holes and mill out a curve that matches the curve of the big holes but taking material out from between them. 

If I'm visualizing this, you should wind up with a rather unique almost filigree spoke arrangement that absolutely no one else will have. Well, unless they read and can follow this pre-coffee IV description.

I don't have a CAD program loaded (or a scanner) or I'd draw it out for you.

BEst regards,

Kludge


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## CrewCab (Oct 21, 2008)

Brian Rupnow  said:
			
		

> Can you say "Nervous exhaustion'???



You certainly can ............... pull up a chair and rest a moment 




			
				Brian Rupnow  said:
			
		

> I was taking a full depth cut,



Well done Brian ............. enjoy a well deserved soak 8)

As for me ......... and this just my approach, and because my Mill is fairly small, .......... I would have done several passes to take out 1/4" of brass, each one would have been a lot quicker .......... so overall the time spent milling would probably be a little longer but, ........... a bit less stressful ;D

as I say ........... just my way, an that don't make it right.

CC


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## wareagle (Oct 21, 2008)

Brian, it looks great! Hang in there! No need to sweat that much over a little flywheel... It's not for the Space Shuttle!


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## Cedge (Oct 21, 2008)

WE...
You are so right... it's not for the space shuttle. It's more important than that... it's for HIS steam engine....LOL

Steve


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## wareagle (Oct 21, 2008)

Cedge  said:
			
		

> WE...
> You are so right... it's not for the space shuttle. It's more important than that... it's for HIS steam engine....LOL
> 
> Steve



Okay Steve, you are right. This is a very important project indeed, and my comments were less than supportive to Mr. Rupnow. I stand corrected.  :-[ 

Brian, please disregard my last post... You are free to loose sleep, worry and sweat all you want!  ;D 
	

	
	
		
		

		
			





 :big: 
	

	
	
		
		

		
		
	


	




All kidding aside, you really are doing great!!


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## Brian Rupnow (Oct 22, 2008)

ALLRIGHT!!! here we go. Its a success. Not an "unqualified success", but a darn good one for my first ever flywheel with spokes cut on a rotary table. These pictures are "hot off the mill". I have filing to do, and general clean up, but I'm happy. I have learned, as someone already pointed out, that the inner "point" of the window closest to the center should not be based on 2 seperate small holes. They should be based on a single large hole instead of 2 small holes that overlap. Also, as I believe Kvom pointed out, it would have been much easier if I had drilled and reamed the centerhole on the lathe BEFORE moving over to the rotary table to make it easier to get everything centered to start with. My rotary table is a Chinese job, but of relatively good quality. Four turns of the handle give one degree of rotation at the table. The round handle that you turn has 120 evely spaced lines on it. This means that one turn of the handle equals 1/4 of a degree. In that 1/4 of a degree of turn, there are 120/4=30 evenly spaced lines. I infer from that that each evenly spaced line equals 2 minutes. That is the math basis that I used and it seemed to work. Of course, the instructions are in Chinglish, and clearly state that""The micro collar is graduated in steps of one min." which is totally wrong and lead to some initial confusion. Now if I can just get the other flywheel done with the same degree of good fortune, I will be away and running.


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## SandyC (Oct 22, 2008)

;D ;D

Congratulations and well done Brian, but I do hope that is not your lifes blood staining the work!!!

Hopefully it is just marking fluid.

A bit of carefull work back on the rotary table would allow you to get rid of most of the remaining material and then finish with some filling.
By the time you have finished the second flywheel you will be looking back and saying...what the hell was I so hung up about. ;D ;D ;D  :big: :big:

On a side note: -

Are you sure about the Maths you presented?...... I agree with the final 2 minutes, but I got there from a different calculation.

On your drawing you have jotted 1 turn = 4 degs. of rotation, which would be correct for a 90:1 gear ratio table, a 
typical ratio for a lot of the current models available.

4 degs = 240 minutes...divide by the 120 marks on your handwheel gives 2 minutes per div.

on the other hand: -

If, as you suggest in your write up, it is 4 turns per deg of rotation, this would be a 1440:1 ratio....I must say I have never come accross a rotary table with such a high ratio.... I am not saying they don't exist though.

If it is as you wrote, then 1 turn would = 1/4 deg.

1/4 deg = 15 minutes, which divided by 120 would give 7.5 seconds per div.

Just curious.

Keep happy.

Sandy.&#160;  ;D


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## mklotz (Oct 22, 2008)

Brian,

I'm having trouble understanding what you wrote here. You say 1 handle turn = 1/4 degree of table movement (I find that hard to believe but more on that below...).
If what you say is true then:

1/4 deg = 15 min

15 min / 120 divisions = 0.125 min/division

1/4 deg per turn would mean that the table has a gear ratio of 4*360:1 = 1440:1. You would have to turn the handle 1440 times to rotate the table one revolution! I've never heard of an RT with such a fine gear ratio and, frankly, don't believe you have such.

Now, most of the Chinese tables have a 90:1 ratio. Thus one turn of the handle corresponds to 4 (not 1/4) degrees of table movement. Then we have:

4 deg = 240 min

240 min / 120 divisions = 2 min/division

Somehow, you arrived at the right conclusion (2 min/division) but your writeup doesn't mesh with the mathematics involved.

I'm not trying to be a nit-picker here but rather trying to help you avoid future mistakes based on an incorrect conception of how your table works.


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## mklotz (Oct 22, 2008)

I see Sandy beat me to the punch.  Ah well, at least we both came to the same conclusion.

On my RT, Brian, every 30th division on the handwheel is marked with a number - 0,1,2,3 - which corresponds to a degree of table rotation. If yours has just 120 undifferentiated divisions, you may want to consider marking every 30th with paint or a punch dimple to make it easier to dial in integral numbers of degrees.


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## Brian Rupnow (Oct 22, 2008)

Told ya I was confused.--Yes, one complete turn of the handle equal 4 full degrees of table movement. Each of the small graduations equals 2 minutes. One quarter turn of the handle equals 1 degree of movement af the rotab. I was very confused, because the Chinglish instructions stated that each small mark was 1 minute, which is incorrect. I did figure it out correctly, then made a mistake when I posted.---And no, thats not my lifes blood, perish the thought.--That is layout dye. I did cover the visible side with layout dye and make scribe lines along where the cuts should be when I started to cut the straight sides of the window, just to reassure myself.


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## Brian Rupnow (Oct 22, 2008)

Not nearly as much drama with the second flywheel---yet anyways. Once I figured out the rotary table, things went a heck of a lot easier. I am amazed at how heavy these little buggers are. When I built the "beam engine at double scale" I made the 5" diameter flywheel out of aluminum, and was dissapointed in how light it was. Its a good thing this new engine is going to be twin cylinders--It is going to take a lot of "Chuf" to get these 4" diameter fellows turning.


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## Brian Rupnow (Oct 22, 2008)

The End ;D ;D :big: :big: :bow: :bow:


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## Philjoe5 (Oct 22, 2008)

Bravo Brian. Your flywheels look great.  :bow: :bow:

Cheers,
Phil


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## Cedge (Oct 22, 2008)

Well done, Brian. A little clean up and you'll have some real bragging rights.

Steve


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## Maryak (Oct 22, 2008)

Brian,

Way to go man, great job
	

	
	
		
		

		
		
	


	



Don't ever think you aren't a machinist 
Best Regards
Bob


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## BobWarfield (Oct 22, 2008)

Isn't it just the best feeling when you're getting good results from a new tool?

The rotab is a complex beast that offers lots more learning opportunity, but this is a wonderful start. Pretty soon you'll be putting arcs of various kinds into all sorts of parts just because you can.

Cheers,

BW


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## wareagle (Oct 22, 2008)

Brian, great job! The RT is an amazing piece of equipment. There's just so much that can be done with one...

So, you have a crankshaft and now two flywheels... What next??


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## cjparsons (Dec 6, 2013)

Cedge said:


> Tim
> You have an excellent eye. I'm right in the middle of writing up a post showing how that very same type of flywheel is made. It should be up in another hour or so.
> 
> Steve


Hello - I am going to have a go at using my new rotary table to make my first spoked flywheel over the weekend (and probably a few after!) using Marv Klotz's excellent tapered spoke calculation program (thanks!) and wondered if you ever did the write up on the curved spoke creation?

Regards

Chris


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## chucketn (Dec 6, 2013)

Thanks Chris, for asking what I was going to ask before I got to your post. 
I'm making patterns to cast a Rider-Ericsson hot air engine and want to make a curved spoke flywheel.
Chuck


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## cjparsons (Dec 6, 2013)

Hello Chuck - think I have found the post;

http://www.homemodelenginemachinist.com/f25/curved-classic-s-spoke-flywheel-construction-2811/

But as you will see all the images are missing which makes it pretty hard to follow?

Hopefully if cedge (Steve?) reads this he might be able to help?

I see he has his own website, perhaps put a page and the images up on this? pleasepleaseplease...

Best wishes from the UK

Chris


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## Sshire (Dec 7, 2013)

Brian
When I did my first cutout flywheel, for Elmer's Pumping Engine, I,  like you, had used the rotab very little. 
I used Marv's program to do the calculations. Then, I put a Sharpie in a collet on the mill and did a "dry run." the Sharpie-drawn flywheel was perfect, as was the "real" one with an end mill. (thank you, Marv)
As with any new operation, it's a bit unnerving the first time. Go slowly, avoid interruptions ( phone off; no visitors). Work safely. Trust me, it will work. 
My latest mantra when doing a new op is "It's just a piece of metal. I have more"
My other philosophy is to make one part until it's perfect ( or close enough). My current build, a Liney RV2, has just about enough "not close enough" parts to make a second engine.


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