Author Topic: Inline-four crankshaft  (Read 201479 times)

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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #240 on: October 28, 2015, 01:15:54 AM »
,,, are you making your engine rather than modifying one?...
Both of the above! The hemi head itself and the V8 block were both made by Mickey Thompson; everything else is my doing.

Well, the pulley combination to attempt 4,500 RPM didn't fly- it couldn't start the cam turning (springs are 290# seat/ 590# open, with 2:1 ratio followers!). So I'll scrounge some different pulleys to see just how fast the 1 HP setup can spin it.
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Offline Rex Schimmer

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Re: Inline-four crankshaft
« Reply #241 on: October 28, 2015, 06:11:31 PM »
Jack,
When you tried the 1 hp motor did you give it a little "manual assist" on the pulley? Some times once it gets turning the friction drops and it will continue to turn. Did it break the breakers on the electrical panel? Most electric motors will run at 200% if you give them some amps. Use your shop air to blow over the motor to assist in cooling. I have run some large DC motors (50 hp) at 150% for hours with out problems. 115 or 230 volts?

You are really a pioneer so keep on keeping on as it is sure interesting to see your results and progress!!!

Rex
Rex

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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #242 on: October 29, 2015, 02:20:51 AM »
Yes, I need to use a ratchet wrench on the cam snout to start it moving regardless of the V-belt drive ratio. I played around more today, using a variable-pitch motor pulley. I got it up to 1,675 cam RPM, where the 20 amp breaker kicks out after 3-4 seconds of running (single phase 115V). Not sure of my next step- perhaps drive the V-belt from my old 7 HP Wheelhorse, except that would interfere with closely listening to the OHC deal being tested.

Tonight I set up a laser tach to read the camshaft speed directly, instead of tediously measuring pulleys and calculating the speed.
« Last Edit: October 29, 2015, 02:34:59 AM by Jack Gifford »
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Offline Rex Schimmer

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Re: Inline-four crankshaft
« Reply #243 on: October 31, 2015, 04:17:29 PM »
20 amps single phase 115 volt is 1.5 HP, you might try a 25 amp breaker and blow air through the electric motor. That would give you 2 hp+ and it may be enough.

Rex
Rex

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Offline TheBaron

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Re: Inline-four crankshaft
« Reply #244 on: October 31, 2015, 08:25:59 PM »
Hi Jack,

If you put a "beam" type torque wrench to work turning the valve train and get a reading on just how much torque it takes to keep things spinning along, the Hp needed can be found by multiplying the torque in ft-lbs times 471 and then divide the result by 550....This will give you the size of the electric motor needed to turn 4500 rpm.

 I used to do this trick on the  CHAMP car engines I assembled to know the basic turning friction before and after run-in.

Robert

Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #245 on: November 01, 2015, 01:07:10 AM »
Thanks for the suggestions. I considered swapping to a 25 or 30 amp breaker, but decided it would only get me a little bit further with the test. There's no simple way to measure the torque required to keep the cam turning- at very slow speeds, such as turning it with a torque wrench, the cam "snaps" from one valve closing to the next opening. Yeah, a person could come up with a load-sensor on the motor mounting to get an average torque value at a decent speed, but that's more hassle than it's worth. I'm almost finished rigging the 7HP Kohler of my Wheelhorse to it- should have it going tomorrow. The Kohler power rating is at 3,400 RPM and I've got a pulley combination that will get the cam to 5,000 RPM- I'm confident the 7HP will do the job. "By accident" I discovered how to avoid most of the noise of the tractor running- the muffler had to be removed to clear the belt, so... now I'll cobble up a connection from the pipe stub to my exhaust hose and run the hose out of the garage!

With all the running I've done of the cam (with no faults) I've got enough confidence in the valvetrain, that I don't need to keep it visible by leaving the rocker cover off. I removed the temporary oil shields, cleaned up the oily mess, and installed the cover. Sure is much "nicer" to deal with now!
« Last Edit: November 01, 2015, 01:15:42 AM by Jack Gifford »
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Offline Milwaukee Midget

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Re: Inline-four crankshaft
« Reply #246 on: November 01, 2015, 01:42:40 AM »
1:07 AM on this post.

Making hay while the sun shines AND burning the midnight oil.

Been a long, productive day for you, Jack - 'bout an hour longer seeing as we switched over from daylight saving time this morning!  :cheers:

"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  :roll:

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!

Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #247 on: November 01, 2015, 11:04:23 PM »
Off-topic...

The sound of a one-lung Kohler exhausting through 15' of 3" diameter hose is amazing!!! The definitive "thumper" sound... :evil:
Especially impressive from outside the garage with the Wheelhorse nowhere in sight 8-)

Monday: got the cam up to about 3,300 RPM, but laser tach was inconsistent. I'll keep plugging until I've seen the valvtrain "happy" at 10,000 engine RPM... or broken.... whichever occurs first! :|
« Last Edit: November 02, 2015, 11:51:35 PM by Jack Gifford »
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Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #248 on: November 09, 2015, 12:15:47 AM »
... I'll keep plugging until I've seen the valvetrain "happy" at 10,000 engine RPM... or broken.... whichever occurs first!...
Umm... guess which occurred first? :-o

The best light I can put this in- is that the spin-test did what it was supposed to do. Can't say the same for my design skills... :-(

The good news is that examination of the break (and re-calculation of tensile stress) clearly shows the change needed to the cross-section at that point. It also shows that the 49 rockwell-C treatment was harder than ideal for the best compromise between brittleness and toughness.

The other good news is that there was no colateral damage- cam, etc.- at about 6,000 [equivalent engine speed] RPM.

The bad news is the hours I spent whittling them out on a manual mill. I guess my best approach now is to farm out the job to a CNC shop- have them scan/digitize an unbroken one, make the necessary changes, and crank out 8 of them. Then treat to ~42 rockwell and transfer the rollers and axles to them. And eventually- try again to break them... :-D
« Last Edit: November 09, 2015, 12:46:52 AM by Jack Gifford »
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Offline RidgeRunner

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Re: Inline-four crankshaft
« Reply #249 on: November 09, 2015, 06:27:02 AM »
Jack,

     Discovering "what if" and "why can't I" is what hot rodding is all about in my book.  A good light to shine, you are maintaining the proper mental altitude required for ultimate success.

          Keep the faith,

          Ed

Offline rebelce

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Re: Inline-four crankshaft
« Reply #250 on: November 09, 2015, 08:11:58 AM »
Sorry to see this! You are living my nightmares Jack. At least you have a handle on the analysis of the problem and the solution in the works.

Offline tallguy

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Re: Inline-four crankshaft
« Reply #251 on: November 09, 2015, 12:15:53 PM »
About breaking of rocker arm(s) . . .

Toughness is an indicator of "impact strength".  Since a rocker arm's load
is increased relatively gradually, I don't see it as "impact" that requires a
lot of toughness.  CNC machining could help, leaving as smooth a finish as
practical (particularly where the surface material of the arm will experience
tensile stress).  Shotpeening could also help.

Hardness is related to tensile strength.  Instead of softening the arms, I
suggest you look at the design -- for example, was the crack initiated at
a small radius or sharp corner?  Either could cause a stress concentration. 
Try to keep the radius large, and the distribution of mass a large distance
away from the neutral line (where only bending occurs, with no tensile or
compressive stress).  Think like a structural engineer . . . in other words,
design the cross section of the arm so it's much like an I-beam, with the
material spread far apart.  You could bounce these ideas off a structural
engineer (I'm not "officially" or "semi-officially" authorized/qualified as one).

Offline John Burk

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Re: Inline-four crankshaft
« Reply #252 on: November 09, 2015, 01:46:44 PM »
One way to strengthen the weak point where the rocker broke . Create a flange along where the one broke . If you're starting with a tube make a fixture around which to hammer the outward flange . A crack will no longer have a point to start . If they are machined from stock add the flange to the design .

Offline Jack Gifford

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Re: Inline-four crankshaft
« Reply #253 on: November 09, 2015, 11:52:26 PM »
Thanks for the pointers. Yes, there was an unintentional stress riser that initiated a fracture in the surface at the break. Correcting the design is straightforward; the problem for me is determining the most practical way to get there- aside from the unlimited-dollars/unlimited-time approach.

tallguy- yes, hardness is related to strength (both yield & ultimate), but it's more closely related to elastic modulus. At 49 Rockwell, these followers are so non-elastic that they can be pushed to their tensile yield point with virtually no distortion. For the next go-around I'll take advantage of the experience of others with 4140 engine parts and use about 42. The only reason for having these at 49 was to assure compatibility of their pivot sockets with the pivot balls (~45 R.c)- but I'll find a way around that.

Incidentally- if you were to watch/listen to these followers transferring ~.7" lifts with 590# springs (~1,200# at the roller, ignoring acceleration forces) from the aggressive cam profiles at 3,000+ RPM.... you might think twice about them not needing to be "tough"! [Acceleration forces were not ignored in my calculations. A rough calculation showed about another 1,200# due to acceleration @ 10,000 engine RPM, to which I added a safety factor of about 20%]
« Last Edit: November 10, 2015, 12:21:18 AM by Jack Gifford »
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Offline Rex Schimmer

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Re: Inline-four crankshaft
« Reply #254 on: November 10, 2015, 03:08:32 PM »
Jack,
Sorry to see your rocker arm failure but if you look at your design it did fail exactly where the maximum bending stress so from that stand point it did what I am sure your analysis predicted if there was a failure. I agree that Rc49 is probably to high (for this material)  and would suggest going even lower than 42 possibly 38 could provide additional toughness and with a slight redesign of your arm provide the require strength. I would suggest that you consider tapering the section of the failed part of the arm from the present dimension at the tip and increasing to the thickness dimension of the arm at the center pivot. This would provide additional section and would reduce the stresses accordingly and would have a minimum affect on the polar moment of inertia about the point of rotation. If you decide to change materials I would also recommend going with aircraft quality (this means that you can get the material certifications from the manufacture that shows the actual composition.) This would provide a pretty large improvement in both tensile and yield strength and possibly material quality. My best choice for this would be 300M which is basically a very high purity 4340. Expensive but worth it for its quality and increased fatigue properties. I would also look closely at the heat treatment process used on your arms as high residual stresses can be imposed on the material if the heat treatment is not done correctly. I agree with tallguy about shot peening the arms after they are finished machined, your arms are a perfect application for shot peening. I also think that you may be designing a little close to the materials properties if you are only using a 20% safety margin.
BTW what is the function of what appears to be an aluminum insert that is pinned (riveted?) to the failed end of the rocker?

Rex
Rex

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