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Author Topic: Inline-four crankshaft  (Read 106490 times)
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RidgeRunner
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« Reply #360 on: August 13, 2017, 05:36:09 AM »

     Great news!  All the best for everything to continue to  go well now.

     Great chat with you at Loring, looking forward to another one when I'm not quite so busy.

               Ed
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wobblywalrus
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« Reply #361 on: August 13, 2017, 09:45:26 AM »

This was explained to me while I was in my early 20's so some things are sorta vague now.  Picture in your mind two moving smooth plates with one laying on top of the other and an oil film between them.  One plate is moving to the right at the same speed the other plate is moving to the left.  The oil at the boundary where it touches the plate is moving at the speed of the plate in the direction the plate is going.  The average speed of the oil halfway between the plates is zero.

The relationships between distances and velocities are "shear."  The shear increases when the plate velocities increase.  It also increases when the plates are closer together.  Lubricants have a limit of shear they can withstand.  The clearances between the moving objects need to be wide enough to keep the shear within acceptable limits.

Flexure can cause clearances to decrease between a shaft and a journal during operation beyond their values when the mechanism is static.  This can lead to lubrication failure.  The specific instance where I learned this was the outside crank journal bushing on a BSA A-65 twin.  There is no center journal on these cranks and they flex.  The clearances at the ends of the journals would be tight in some places due to this flexure.  Sometimes it would occur on the edges of the rod bearings.

What I did was to build the engine, break it in fairly gently, run it hard for a short time, and then tear it down.  Then, I would look for signs of overheating or galled spots on the journals and bushings, scrape them, and put the engine back together.  What I was trying to do was to keep the oil film shear within the limits the lubricant could withstand.   

   
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Jack Gifford
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« Reply #362 on: October 24, 2017, 11:26:18 PM »

No excitement here... which is good news- nothing gone "bang", broken, etc. grin Engine has been test-run a few times now. Still tweaking the fuel system for a reliable idle- it's down to about 1,700 RPM but air/fuel isn't optimal yet.
Firing it up has been troublesome. The cam-driven Enderle pump doesn't want to draw fuel (about 30" above the tank) when cranking. I've had to manually fill the tank-to-pump line for it to begin pumping. My alky experience has all been with a tank above the pump for gravity feed, so I don't know whether this is to be expected with such a slowly-turning gearotor pump (half of cranking speed)? Pump is new and seems to function okay once engine is running. I'm in the process of mounting a test setup tank up at the pump level, but in the lakester I won't be able to put the tank quite that high. And I won't have the option of push-starting due to the full-centrifugal CrowerGlide clutch.
« Last Edit: October 24, 2017, 11:33:02 PM by Jack Gifford » Logged

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Crackerman
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« Reply #363 on: October 25, 2017, 12:07:24 AM »

An electric primer pump and check valves installed in a certain configuration does help it start. If you can find a small electric pump tha will stand up to alcohol.
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Jack Gifford
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« Reply #364 on: November 14, 2017, 12:12:38 AM »

If it's a problem after situating everything in the car, I guess I could look for a high-flow check valve (equivalent flow of -12 lines) to keep fuel from draining out of the pump feed line when not running.
« Last Edit: November 14, 2017, 12:14:42 AM by Jack Gifford » Logged

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Jack Gifford
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« Reply #365 on: November 20, 2017, 12:35:53 AM »

Won't win any collector-design awards. embarassed
But- it will allow some test-running in the dry/heated garage while it's wintry out. Main goal is to get rid of the noxious fumes, but perhaps I'll get to listen to the engine some, instead of just the exhaust roar.


* hemi_four_collector.jpg (91.95 KB, 800x600 - viewed 96 times.)
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revolutionary
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« Reply #366 on: November 20, 2017, 02:36:50 PM »

Jack,

From all the descriptions you provided and the issues you had, I would highly recommend you send the head out to get re-heat treated. It sounds like the aluminum is all too soft.  Just my $.02.
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Jack Gifford
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« Reply #367 on: November 30, 2017, 02:12:56 AM »

Oh well... it worked a couple of times before self-destructing... embarassed


* bent_collector.jpg (96.08 KB, 800x600 - viewed 82 times.)
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bearingburner
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« Reply #368 on: November 30, 2017, 03:16:13 PM »

Had the same problem priming my Hilborn flathead dragster engine 50 years ago. Will we see you at Loring this year with or without car?
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Jack Gifford
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« Reply #369 on: December 01, 2017, 12:48:13 AM »

I hope to see you at Loring at least once this season. Having the lakester ready is doubtful though.
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Jack Gifford
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« Reply #370 on: December 06, 2017, 01:45:10 AM »

Okay... enough unblown testing. Bolted the blower back on and added SFI restraints. If the next start-up goes okay (probably be delayed awhile for decent weather), then next step will be to schedule a dyno session.

Another instance of "my own worst enemy"- I finally explained a small but persistent oil leak at the front of the exhaust cam. Before replacing the seal, I was spinning the sprocket hub to polish its seal surface and saw a small "glitch" right where the seal lip runs. Duh... dummy... oh yeah- that's the mark I had scribed there to denote the internal keyway position when designing the DOHC deal- and totally forgot about it! embarassed


* sprocket_hub_bad.jpg (92.95 KB, 800x600 - viewed 57 times.)
« Last Edit: December 06, 2017, 02:19:12 AM by Jack Gifford » Logged

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