Removing stuck eccentric crank 1938 700E

MrAllied posted:

I have an original, 1938 version 700E.  One of the eccentric cranks is broken and I wish to replace it, but I am unable to remove the portion that mates with the pin on the wheel, as it appears to be frozen onto the it.  I have tried grabbing it with pliers and gently rocking it back & forth, but it will not budge.  Any ideas would be much appreciated.  Thanks in advance.

Try using some WD 40 to loosen the piece and then try and pull it off.

MrAllied posted:

I have an original, 1938 version 700E.  One of the eccentric cranks is broken and I wish to replace it, but I am unable to remove the portion that mates with the pin on the wheel, as it appears to be frozen onto the it.  I have tried grabbing it with pliers and gently rocking it back & forth, but it will not budge.  Any ideas would be much appreciated.  Thanks in advance.

Try using some WD 40 to loosen the piece and then try and pull it off.

Here is my guess:

The crank casting probably suffered from “zinc pest” (as is often true of early 700E castings).  One of the things that happens with pest is that the zinc expands.  Because the portion of the casting you are trying to remove is located inside a non-expanding metal tube, the zinc is now squeezing the crankpin stud.  This is why you are having trouble removing it.

 I advise against trying to pull or wiggle the casting off of the stud because you might wind up loosening the stud or perhaps even pulling the stud out of the driver.  If you were to do that, repairing the damage correctly would be extremely difficult.  (700E crankpin studs are not the same as the postwar 773 studs.  You'd need access to the back of the driver in order to secure a 700E stud correctly.)

 I suggest that you gently try to break apart the zinc casting.  It is likely to be brittle, another well-known side effect of pest.  This type of repair is outside my area of expertise, but I think what might work best would be to use a low-speed Dremel tool with a very narrow diameter drill bit, and then drill into the zinc casting just inside the interior edge of the metal tube.  Several holes may be needed.  Do not drill near the center of the casting or you may damage the crankpin stud.  After you have degraded the structural integrity of the casting, especially if you are able to shatter it, the casting should come off pretty easily.  Good luck!

In looking at all the white powder around the fracture point on the eccentric crank, it looks like there is considerable zinc corrosion.  When zinc corrodes it expands.  The sleeve around the outside of the eccentric crank is probably constraining the corroding zinc, which then clamping the crank insert.  You may not want to try rocking the broken eccentric crank, as there is a risk that this will loosen the crank insert in the die cast wheel center.  I am assuming that you were able to remove the screw completely and it is not broken off in the crank insert.  If I was facing this problem I would probably try to cut the sleeve off the eccentric crank with a high speed Dremel abrasive cutting tool.  Then grind, cut , file away at the eccentric crank shaft until you can get it off the crank pin insert. In my mind the challenge is to protect the crank pin insert as I would not want to get involved with trying to put a new crank pin insert in the original wheel center. I believe that both the eccentric crank and the sleeve were remade for the 1990 1-700E, and these parts are still available.   Given the condition of the eccentric crank on this side, it might be prudent to also change this part on the other side. 

To help minimize any additional corrosion, it would be best to keep your locomotive in a cool dry environment.  

Best of luck to you and please let us know how it comes out. 

Instead of WD40, I would use penetrating oil - it is designed for loosening rust nuts/bolts, and may help you here. You local hardware store will have it.

I am not familiar with this, but I assume you are trying to remove the inner part, not the outer part. This being the case, I would try to find a screw that would just tap itself into the hole, but can not to big to expand that inner cylinder you are trying to remove. Once threaded in, and giving the penetrating oil a chance to work, you can try to grab the screw and pull out.

Combining @700E and @David Johnston ideas from above, if you have a dremel tool, you can purchase burrs as in the attached screenshot. Using a very small burr, you can grind out the zinc, or as I would try, make a slot in the zinc vertically down the hole to allow you to then use a small screwdriver or awl  the break the zinc, the slot allowing you space to deform the zinc into.

First of all, thanks to everyone who offered advice.  It was very much appreciated.

As it turns out, I had another, broken, 700E eccentric that I happened to find in my junk box.  As I looked at it, I wondered just how tough the steel casing was around the cast metal tube.  So, I got a pair of side cutters and the thing collapsed pretty easily.  SOOOOOOO, being very careful, I just sort of started to nip away at the one in the photo.  I’d grab a bit of the thin steel, pull it and sort of curl it—all the time being very careful not to put too much stress on the wheel—and as I did this, the cast inner tube sort of crumbled.  It took some time and patience, but I finally got her off clean, with no damage to the wheel or the pin.  By the way, I did try WD40 and 3 in 1 penetrating oil, all to no avail, as it was really stuck in there and did not come loose until I had virtually all of it cut away.