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Author Topic: Inline-four crankshaft  (Read 214878 times)

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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #180 on: February 28, 2015, 12:02:09 AM »
Thanks JimL. Vibration is certainly a big concern for me, having never built an inline-4 race engine before.

I drilled ten 5/8" holes in each end plate, to hopefully "free up" the test sample somewhat. After re-assembling it, I was quite surprised that giving it a little hand-spin results in about twice as long a coast-down; maybe 7-8 seconds instead of 3-4 seconds.
« Last Edit: February 28, 2015, 12:29:15 AM by Jack Gifford »
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #181 on: March 01, 2015, 12:49:41 AM »
8,390 RPM. No destruction yet. More to come...
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #182 on: March 07, 2015, 01:17:46 AM »
Pretty poor planning on my part, not doing any calculation of power required for this test. Couldn't get more than about 8,400 RPM using the 2HP mill. So I decided to try one more last-ditch attempt before turning the task over to a "professional". Working with available stuff, I "paralleled" the 1HP motor onto the 2HP mill, with the pulley ratios which give the same no-load speed at the mill spindle. Got the sample past 10,000 RPM a couple of times, highest of 10,746 RPM. I'll do a little more tweaking, as there are variable-pitch pulleys on both the 1HP motor and on the test fixture. I had arbitrarily aimed for a 20% safety-factor (above the planned 10,000 RPM engine speed), so I'm not there yet.  However, the 10,746 is already about 15% over on radial acceleration.

I'm still not "comfortable" with belts and pulley rims moving more that 150 ft/sec next to me... but my knuckles aren't quite as white as when I began... :-o
« Last Edit: March 07, 2015, 01:34:16 AM by Jack Gifford »
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Offline wobblywalrus

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Re: Inline-four crankshaft
« Reply #183 on: March 07, 2015, 09:34:12 PM »
That looks like a picture of a Velocette on the wall.  None of those got anywhere near 10,000 rpm.

Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #184 on: March 08, 2015, 01:16:49 AM »
... a Velocette... None of those got anywhere near 10,000 rpm...
Bikes can be fun at any speed!

Tweaked the "spin test" up to 11,158 RPM. No destruction, no bodily harm... guess I'll "call it a day". The sample did see 25% more radial acceleration than the actual pieces will at 10,000 RPM, so there's at least a chance of success. I'm talking to a shop about doing CNC milling of the eight magnesium segments- which would allow a closer fit to the crank webs than my manual-milled sample. And I'll be busy for awhile doing the necessary milling of the crank's web flanks.
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #185 on: March 13, 2015, 01:41:16 AM »
I jus' don't got no respect... pay $3,600 for a Moldex billet, and then start hackin' away on it! :roll:
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #186 on: March 15, 2015, 12:38:37 AM »
Wow, what a *#&+#%# to machine! I should have asked earlier- Moldex heat-treated the whole thing up to 42 Rockwell-c. And they Nitrided it, which can instantaneously kill a cutting tool just trying to break through the surface.
Anybody got a good deal on a used cutting tool sharpener? Trying to keep C6 carbide end mills sharp, by hand on a diamond wheel, is getting VERY tedious- and obviously compromises their efficiency.
Taking it one step at a time, but... worried about the drilling/tapping needed...
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Offline fordboy628

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Re: Inline-four crankshaft
« Reply #187 on: March 15, 2015, 07:44:46 AM »
Wow, what a *#&+#%# to machine! I should have asked earlier- Moldex heat-treated the whole thing up to 42 Rockwell-c. And they Nitrided it, which can instantaneously kill a cutting tool just trying to break through the surface.
Anybody got a good deal on a used cutting tool sharpener? Trying to keep C6 carbide end mills sharp, by hand on a diamond wheel, is getting VERY tedious- and obviously compromises their efficiency.
Taking it one step at a time, but... worried about the drilling/tapping needed...

Jack,

When we were tapping some nitrided EN40B cranks, it took one tap per hole.    If reused, the taps snapped off in the holes, at max depth of course.    None of the cutting fluids seemed to help much.     Hope you have a friend with an EDM . . . .
 :cheers:
Fordboy
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #188 on: March 16, 2015, 12:16:54 AM »
Irony: I've got an old Elox EDM (vacuum tube) sitting here, that I haven't found time to get working yet!! :roll:
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Offline jacksoni

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Re: Inline-four crankshaft
« Reply #189 on: March 16, 2015, 03:16:18 PM »
Wow, what a *#&+#%# to machine! I should have asked earlier- Moldex heat-treated the whole thing up to 42 Rockwell-c. And they Nitrided it, which can instantaneously kill a cutting tool just trying to break through the surface.
Anybody got a good deal on a used cutting tool sharpener? Trying to keep C6 carbide end mills sharp, by hand on a diamond wheel, is getting VERY tedious- and obviously compromises their efficiency.
Taking it one step at a time, but... worried about the drilling/tapping needed...

Maybe it is subtley trying to tell you something.... (leave me alone....) LOL. sounds like a good piece of gear though. I have a moldex too. Has survived couple episodes of oil pressure loss under power and an excursion to neighborhood of 13k rpms when popped out of gear at full throttle.
Jack Iliff
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Offline Rex Schimmer

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Re: Inline-four crankshaft
« Reply #190 on: March 16, 2015, 05:07:39 PM »
Jack,
As nitriding is pretty thin you may be ahead to pre-grind the areas that you plan to machine to remove the nitriding. This still doesn't do anything for you in the 42Rc 4340. Nothing kills tools faster than not having a stiff set up and looking at your mill set up I think I might try to move the head down as close to the crank as possible and then pull the quill/spindle back up as short as possible and also maybe consider using a small, 3-4 inch dia face mill with indexable carbide inserts and couple it as close as you can to your spindle. Turn it slow and lots of coolant. I worked on a project where we were cutting some 4340 that was around 35-40 Rc and we were using a 12 dia indexable face cutter, 6 inch spindle, and it ran at around 75 hp to make the cut, 12 inchs wide, .2 to .3 inches deep, probably not more than 50 rpm, don't remember the feed speed but the operator had to stand over the chip pile with a fire extinguisher to keep putting out the small fires from the slight amount of spindle oil and coolant that keep starting to burn. The chips came of the part with a very nice red glow!  Just a note, the spindle was actually a 50 hp spindle but we were doing a 12 hour, 150% test to prove out the spindle. The machine was a Giddings and Lewis 6 inch spindle floor mill and we had to run this test with the spindle only extended a couple of inches any more and the cutting tool would not live.

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Offline ronnieroadster

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Re: Inline-four crankshaft
« Reply #191 on: March 16, 2015, 06:29:11 PM »
The Moldex crank made for my flathead needed a huge amount of material removed from all six counter balance areas. Why you may ask would I need to remove material that's because Moldex screwed up. Counter ballancers so big in diameter I was unable to put a cam in the block! It took only six hours in my South Bend lath to remove the material. As your learning the crank material is very hard I could only remove .005 per pass. Man what a pain in the Acura. But heck what would you expect that crank shaft only cost me $3200.00. Knife edging and detailing was much easier using die grinders and four inch grinding pads on a Makita grinder. But only after correcting their screw up good times for sure  :x
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #192 on: March 17, 2015, 01:06:14 AM »
Yes, I will do abrasive removal of the Nitride in some spots. And, yes, I did drop the mill head down a ways. A larger more rigid milling machine would be advantageous- but after 25 years of cranking work out on this little one, I've gotten adept at minimizing the problem. Generally, I keep a tool sharp enough to do a .001" cut to final dimension. But good 4340 at 42Rc is nasty- not just the hardness, but it's as "tough" as most stainless alloys. At 285 RPM, 3/4" diameter mill, and cutting only .005" at very slow feed, I'm having to sharpen C6 carbide cutting edges about every two hours.
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Offline Koncretekid

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Re: Inline-four crankshaft
« Reply #193 on: March 17, 2015, 03:06:59 PM »
Jack,
Is that a Rong Fu RF-30 mill drill?  If so, you've got more guts than I do.  .5mm lash in the lead screws (acme, not ball screws) and the Z axis is worse - - no real way of controlling other than keeping the lock tight and hoping the dial is correct!  Good on you!
Tom
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #194 on: March 18, 2015, 01:30:09 AM »
Tom- As I said, I've had 25+ years to become adept with the mill. I think you can see in the last photo, the 6" dial caliper with zero-lash mountings to read the Z-axis. I also added the home-brew motor drive for Z-axis, infinitely variable from .001" - .004" per second with adjustable microswitch stop- works great for precise cuts (boring or OD turning) with an offset boring head that uses 3/4" diameter boring bars. I also built a variable-angle tool feeder to emulate angled-cross-slide lathe work (cone-shapes, etc.). When I first got it, I carefully squared the spindle centerline to the table ways by selective shimming between the cast column and the base (within .0005" over a 12" diameter swing). Also had 2" thick spacer blocks surface ground that I can install between the column and base to gain a little more headroom (and a stand to support the top-end to install/remove the spacers)- which I needed to bore and hone Kohler single-cylinder blocks. Last summer (after 25 years) I did have to replace the X-axis table nut (bronze casting); I took that opportunity to add easily-accessible grease fittings to both table nuts (maybe get more than 25 years next time?).  Good news was that the  lead screws show zero wear. The hardest thing for me to deal with is the inaccuracy of the X lead screw- it moves 1.001" for each 1.000" dialed (but consistent across all 22" of travel). I've been promising myself to add a DRO (digital readout) to the X, but just haven't gotten to it yet. It's a Central Machinery model 590 bought from Harbor Freight. If I said I run it ten hours per week (very conservative estimate- I even had a custom-machining business for about five years), that would be 13,000 hours on it! Spindle bearings are still perfect and the ways don't have measurable wear. Of course I've lost count of number of drive belts consumed... :roll:

Oh- also had to replace the 2HP motor last summer. :-(

Milling on the crank is making progress- close to half done now. It's caused me to improve my skills at re-sharpening 4-flute carbide mills- I'm now to the point where I can get all four flutes to cut quite evenly!
« Last Edit: March 18, 2015, 01:37:24 AM by Jack Gifford »
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