+- (https://bigbluetrains.com)
+-- Forum: The Back Shop (https://bigbluetrains.com/forumdisplay.php?fid=52)
+--- Forum: Engineer's Technical Workshop (https://bigbluetrains.com/forumdisplay.php?fid=28)
+--- Thread: Position of eccentric crank? (/showthread.php?tid=9097)
Position of eccentric crank? - FiatFan - 03-24-2020
I'm having a problem with a LifeLike 0-6-0 switcher. It will run ok in forward but when I go to reverse the eccentric arm moves out of position and locks up the engine. I'm suspecting that possibly the eccentric crank is out of position. On both sides of the engine the eccentric cranks are offset from the centerline of the axle. The one that keeps locking up appears to be very slightly more offset from the centerline that the other one. Where should the eccentric crank be positioned in relation to the centerline of the axle? I've looked at images from the internet til my eyes are blurry and can't really tell for sure. Some appear to be aligned with the centerline of the axle others not so much. I always bring the engine to a stop before reversing direction.
Any information, suggestions, and/or guidance will be greatly appreciated.
Tom
RE: Position of eccentric crank? - Charlie B - 03-24-2020
(03-24-2020, 01:27 PM)FiatFan Wrote: I'm having a problem with a LifeLike 0-6-0 switcher. It will run ok in forward but when I go to reverse the eccentric arm moves out of position and locks up the engine. I'm suspecting that possibly the eccentric crank is out of position. On both sides of the engine the eccentric cranks are offset from the centerline of the axle. The one that keeps locking up appears to be very slightly more offset from the centerline that the other one. Where should the eccentric crank be positioned in relation to the centerline of the axle? I've looked at images from the internet til my eyes are blurry and can't really tell for sure. Some appear to be aligned with the centerline of the axle others not so much. I always bring the engine to a stop before reversing direction.
Any information, suggestions, and/or guidance will be greatly appreciated.
Tom
Well Tom, for what I know, the closer you position the "free" end to the center, the less movement there is. In the few I have adjusted I go for the least movement to save wear and tear on the rods. (If we are thinking of the same thing)
Charlie
RE: Position of eccentric crank? - FiatFan - 03-24-2020
For clarity the arrow point to the rod I'm talking about.
Tom
RE: Position of eccentric crank? - Charlie B - 03-24-2020
(03-24-2020, 02:13 PM)FiatFan Wrote: For clarity the arrow point to the rod I'm talking about.
Tom
Yep we are talking the same thing. I would turn that counter clockwise about 15 degrees, and same on other side.I don't think it is real critical as it would be with a prototype.
Charlie
RE: Position of eccentric crank? - FiatFan - 03-24-2020
Thanks, Charlie. I'm assuming you mean toward the centerline?
Tom
RE: Position of eccentric crank? - BR60103 - 03-24-2020
That crank looks awfully far off center. It has to be a bit off center to work (meaning of eccentric). I would try to get it over the disc around the axle.
The actual amount is probably based on how much the valve moves in the cylinder and the geometry of the rods connecting them. Which side of the axle depends on whether the valve is inside- or outside-admission. (sorry, I don't know; might be able to look up). I think that both cranks should lead or trail the mounting pin.
RE: Position of eccentric crank? - FiatFan - 03-25-2020
Charlie and David - thank you for your help. I'll make the adjustments after the plumber leaves. Not my best day yesterday.
Tom
RE: Position of eccentric crank? - BR60103 - 03-25-2020
I looked at my Model Railroader Cyclopedia today. The pivot point varies a bit, but the edge of the axle looks common.
They had pics and plans of an 0-6-0 somewhat like yours and they were different on which side of the axle the crank went on. If you put it on the wrong side, the Johnson bar (reverse lever) would have to be in full reverse to go forward.
RE: Position of eccentric crank? - FiatFan - 03-26-2020
Thank you, David. Still trying to find a wrench to fit the hex head. Found the one I have but it's too small and I'm trying not to damage all the nice detail on the engine. I'll post the result when I get it fixed.
Tom
RE: Position of eccentric crank? - FiatFan - 03-30-2020
Update: I tried making a wrench over the weekend and that failed miserably. Got on the internet and found several wrenches that would work. First one was in a set for $35. No, thanks. Then I found a less expensive set for $20. Hmm. Getting better. Found the single wrench size I need for $6. Score. Tried to order it and the shipping was $13. The single wrench is in Des Moines, about 90 miles away. I get down there occasionally so I guess Ill wait for my next trip.
Thanks for your help, guys.
Tom
RE: Position of eccentric crank? - doctorwayne - 03-30-2020
While not as good as a socket, you could likely create an open-ended wrench from some not-too-thick sheet brass. Cut a slot in it using a blade of suitable thickness, then use a needle file to widen the slot to slip over the head.
Wayne
RE: Position of eccentric crank? - FiatFan - 03-30-2020
Wayne - thanks for the suggestion. That's one of the methods I tried over the weekend. The struggle continues.
Tom
RE: Position of eccentric crank? - BR60103 - 03-30-2020
When I had to re-do an eccentric, I started buying some hex socket bolts from an aircraft hobby store. I picked the size by comparing it to some Allen wrenches.
I later bought a set of sockets on sticks. That was either the $30 or $45 set.
RE: Position of eccentric crank? - FiatFan - 08-26-2020
Update: here's part of n e-mail I received from Walthers.
Eccentric cranks #121 ® or #147 (L) are not held in by a nut or screw but press fit their square shanks in to square holes in the drive wheels. (See attached exploded view). The orientation of the crank should appear about 10-deg off alignment to the drivers axis. The “Nut” is a decorative relief on the head of the crankpin.
I pried out the eccentric, rotated it 90 degrees, re-inserted it, and all is right with the world.
Thanks again to all who helped.
Tom
RE: Position of eccentric crank? - Selector - 06-03-2023
Eccentric cranks are typically 'advanced' by about 17 deg from the main crank, on BOTH sides of the engine. So, one side at a time, place all the main cranks at BDC (6 o'clock hour hand), and the eccentric cranks should be rotated toward the cylinders by about 17 deg.