BLI Mikado - Connecting Rods are Jamming and Locking Up

Model Railroader General Discussion (Model Railroader)
1

I bought a BLI 2-8-2 Mikado around 9 years ago.

I never did anything about it, but the connection rods jam and lock up on occasion. The most recent time that it happened, I called BLI about the problem. They will repair it for $65, but the original parts are no longer available, so they would use parts from the current line of Mikados and put my shell on top of the rehabbed chassis. Fair enough, but I am too cheap at this point to spend the $65.

To free up the connecting rods in the past, I have had to remove the plastic plate that holds the driver wheels and connecting rods in place and fiddle with the driver wheels.

This time, I decided to look more closely at the problem. If you look at the first photo, a shot from the side of the loco, the area inside the green circle was where I initially thought that the problem was occurring. The rods that slide on the top and bottom of that assembly had fallen off to the side of the assembly and locked up. However, over time, as it jam and lock up occurred, I noticed that the connect rod itself was bending, as seen in the area inside the red circle.

But, now, if you look at the second photo, a shot from the bottom of the loco,I have circled a third area in blue. That square bronze bearing doesn’t stay in place with lateral movement of the wheels. The other three driver sets and their square bronze bearings hold into place on the first three driver wheel sets, but not on that rear set of driver wheels. Usually, this is not a problem, but in the event of a derailment, this excessive lateral movement causes the connecting rods to slip, jam, and lock up.

This doesn’t happen often because derailments do not occur often except in the case of operator error. But, when it happens, the connecting rods jam up and lock. And, of course, the resulting bending of that connecting rod has weakened it.

I have checked with an NMRA gauge and the driver wheelsets are all in

2

Hey, Rich,

I have a 2-3 yr old BLI mikado and have not had the problem, but I’ll dive in a bit anyway. I may just need to reread your description (e.g., is it the main, connecting or eccentric rod that bends, and what is it hanging up on?) but am not clear on what is binding and locking up (what hits what first, or is that bronze bearing block sliding out of its slot?).

On my 2013 Athearn challenger, I had a problem where the eccentric rod could come around and hit one of the connecting or main rod nuts and it got bent. It turns out that is not uncommon on the Genesis 2013 challengers and 2014 big boys. I managed to bend the eccentric crank out a bit but bent the rod too much and managed break the rod. Consulting with Athearn’s repair tech he sent a free replacement rod & crank and advised how to check the clearance, etc, so I got past that successfully. All this just to make the points of determining the interference issue exactly and if bending things that seem bendable, some of these parts have limited flexibility.

Perhaps more helpful to your situation, if the rear driver lateral movement is the real source of the problem, perhaps that movement can be limited. On my BLI mountain (not the current Paragon2 but the prior ones) it is my most finnicky regarding derailments, e.g., backing over a curved not entirely flat turnout the rear driver tries to climb over the rail. My LHS guy thought the springs might be changed to help this, but it did not. (I think it had non-stock springs as that release needed several adjustments, but he thought some NWSL springs might help, but it did not). Getting to my point, he made thing much better by doing two things. The first was reducing the rear (and front, I think) drivers lateral play by adding washer shims, some Kadee gray fiber washers with a slot cut out so the washer could simply be slipped onto the axle. (They are not so

3

Rich,

I have a pair of BLI Mikes. If you look at the bottom cover plate, you will see a series of pins that hold the main driver bearings in place. The bearings have to be inside the pins on the cover plate to limit the side play of the drivers. this should solve the problem of the side rods binding. That said, it’s a real bugger to get all of the bearing inside the pins at the same time. A good pair of magnifiers and a couple of small screwdrivers help. Hope that splves your problem.

PS

4

Paul, thanks for that reply. It was very helpful and got me thinking even more about the problem and its cause.

I am not sure at this point what is causing the connecting rods to bind and lock up the driver wheels. But from everything that I have studied about it when it happens, I am convinced that either the square bronze bearing is falling out of its housing or else it is the excessive lateral movement of the third set of driver wheels (perhaps caused by that bearing falling out of place).

I am not all that familiar with the names of the various connecting rods, but it is the outermost rod and it connects the second and third set of driver wheels (eccentric rod ?). If you look closely at that rod, inside the red circle, the rod is bent in the middle.

Your comments about adding a washer to the axle to restrict lateral movement is interesting. Would I need a wheel puller to remove the wheel in order to insert the washer?

Rich

5

You need to determine if the rear axle play is engineered into the unit or is caused by wear.

6

Part of the problem may be that the eccentric crank (the short, vertical part on the third driver in your first photo) is improperly positioned. Its bottom end in the photo should be pointing roughly to the mid-point of the counterweight on that wheel.
You may have to remove the hex-headed screw which holds it in place in order to re-align things. Also, check for the same problem on the opposite side of the loco.
The problem of the lock-up, though, sounds to me as if you have an out-of-quarter driver. It’s not on the side of the loco showing, though, as all of the wheel counterweights are in roughly the same position relative to one another. Check the other side to see if their positions are similarly relative (they should all be in a different position from the side shown by about 90°).

Wayne

7

I concur with Wayne. Theres something not right about your eccentric crank in the side view photo. Put her in ‘rods down’ position and check both sides. Not that model locos conform to the real action of side rods, but they must work close to it to keep from binding or locking up. This should also help in checking if the drivers are correctly quartered.

Check too to see if (not likely but…) a driver isnt loose on the axle, giving it the ability to ‘freewheel’ against the rods. This would cause a lock up or bind. This is rare however it happens. I had once a loco (Rivarossi) with a split in a driver right at the axle housing. With the play that is inherent in model rods, this caused the wheel to move out of synch with the rest of the drivers. And ofcourse, a bind.

Douglas

8

Wayne here are photos of the right side and the left side (problem side) of the locomotive. I simply rotated the loco on a box for the photo without running it.

Do the position of the driver wheels and eccentric cranks look right?

I am wondering about something else. The first three sets of driver wheels are geared but the fourth set of driver wheels is not geared. So, is it supposed to have more lateral movement that the geared wheelsets?

Rich

9

The drivers seem to be quartered from the pics.

This is what I do in these situations: I remove the boiler and remove the motor. This allows me to (gently) roll the wheels freely to see what’s going on. In 95% of the cases, I will locate the problem and fix it (could be a screw or a rod rubbing against something). Now in your case, you say that the bronze bearing is not staying put. Are you sure that the bottom cover is fastened properly? I had a bowser that gave me problems because of this. If the screws are not on tight, it would move around. As mentioned earlier, all the components need to fit in snuggly. Normally, these components should not move, but most locos of this size (with flanges) will have some play in the middle drivers to negotiate curves.

Let us know what happens.

10

I agree with Wayne and Douglas. Built quite a few Mantua & Bowser steamers, once learning how, they will roll without Motor on a sheet of glass. Some lateral movement is necessary on drivers.

Take Care! [:D]

Frank

11

Rich, some additional thoughts:

  • on my BLI mike, I decided to lube it and when doing so, I managed to mess up the spring arrangement so something was out of whack and had to send it in for expert help

  • some comments above talk about quartering problems. If I understand correctly, the loco runs smoothly when not derailing, so that sounds like ok quartering. If the binding occurs only when derailing due to misthrown turnout or track abnormalities, I’d guess the key problem(s) don’t include quartering getting off, or it would just run funny (lopping). (how do you spell “loap-ing”?). I suggest figuring out what can cause it to derail consistently and then make it happen repeatedly and closely observe what happens first (e.g., rear driver moves lots laterally?), second (connecting rod mechanism binds?), third (binding distorts whole rods mechanism and eccentric rod hits and gets hung up on rod bolt and bends???), if at all possible. Oh, the split Kadee washer just slips onto the driver axle shaft between the bearing and wheel. It’s easy to get on, but hard to grab to pull off as it requires real thin tweeers to grab the edge of it when on.

I still suggest talk with BLI some more or Mike at S.A. Dibbles Hobbies if he doesn’t mind as he may have specific insight to this situation. I was impressed by how much Mike knew about the very slightly used (earlier version) BLI Mountain that I bought there. Apparently that run had some key problems such as poor driver bearing machining, driver springing being substandard (I my be remembering the spcifics wrong) and/or other things where most (as opposed to a few) of the run 's items needed significant work.

Oh, as I learned on my Athearn challenger issues, the main rod is the one that goes from the piston to the driven wheel, the “connecting”

12

I am going to have to examine the driver wheels and connecting rods much more closely the next time that they lock up.

Normally, the loco runs just fine, even at top speeds, with no jamming or lockups whatsoever. It is only when a derailment occurs, and that is not often - - only through operator error on a turnout.

If I turn the loco upside down and move the driver wheels back and forth with my fingers, there is some lateral movement, but not enough to touch the plastic cover plate. This is true for the first three sets of driver wheels. However, the fourth set shows much more lateral movement, touching the plastic cover plate.

It is my feeling, right or wrong, that when the loco derails, the lateral movement of this fourth wheelset reaches the plastic cover plate, whereas when the loco is on the rails, there is little lateral movement. This excessive lateral movement of the fourth wheelset causes the eccentric rod to jam and bend, knocking other connecting rods out of position, locking up the entire set of 8 driver wheels.

Incidentally, the three screws that hold down the plastic cover plate are completely screwed in, securely holding down the cover plate over the driver wheels and bearings. I still cannot help but wonder if the square bronze bearing on the left side of the fourth driver wheelset is not machined properly, causing this whole series of catastrophic events.

If I can figure this out, I will get back to everyone.

13

Rich, the drivers appear to be in-quarter on both sides, but that left side eccentric crank needs adjusting. In its current position, the motion through the connecting linkage means that the movement imparted to the valve stem occurs at the wrong time and may actually be causing the free end of that valve stem to drop out of the valve chest. When the valve gear moves through the next cycle, the stem wouldn’t be able to move forward. That may not be the cause of the bind, but it’s probably the easiest to correct, and would, at worst, eliminate one possible cause of the bind.

Wayne

14

Wayne, thanks for bringing that issue up again. I inadvertently overlooked it in my earlier response. I drew an arrow to the position on the wheel that I think you are suggesting. Is that the correct position?

Rich

15

Do you see any signs of wear on the rear driver bearings or frame?

16

Jim, that is a good question. Let me take a look.

Rich

17

Yup, that’s it. [:D]

Wayne

18

Rich, I don’t own any steam but have been following this thread with interest. I see your logic in your analysis…if it runs fine but only locks up on derailment, then the jolt from the derailment might be causing hings to dislodge.

Instead of trying to replace the bearing, could you try to make the slot it fits into smaller, thereby keeping more secure? I was thinking to add small strips of styrene to the slot the bearing fits into to reduce its size. If you coul

19

Rich, on the issue of the eccentric crank position, a couple of considerations basis my Athearn challenger learnings, recognizing there may or may not be similarities. On the Athearns, IIRC the eccentric cranks fit on the driver bolt in a special way; i.e., the bolt has a portion near the threads for the nut that is not round, but oval or ellipitical. And the similar shape hole in the eccentric crank therefore has to fit on one way or 180 degrees opposite to that. That fixes the eccentric crank relative to the driver so the crank can “drive” the eccentric rod to the valve gear. I mention that because if yours is similar in design the crank bolt hole posssibly could have been rounded out which could allow it to get out of position or have movement relative to the driver. If so, I’m not sure if it would be more suceptible to binding or other issues. Just a thought, but perhaps unlikely as your loco normally runs fine.

The other point is I didn’t know what to do for driver bolt wrenches as when I measured the bolt head of one it didn’t seem to fit any of the Micromark wrench set items so I didn’t know what to get. The Athearn spare driver (w/o tire groove) came with the appropriate wrench for the challenger and big boy driver bolts but I still don’t know if my other steamers would require special or typical small metric wrenches should I have to fiddle with them.

20

Thanks, everyone (Wayne, Jim, Paul, Doughless) for your recent replies.

I called BLI again today to discuss the problem with the loco. BLI is going to send me new springs to replace the current ones under the driver wheels. Some, but not all, of the springs have weakened significantly. I am not sure if that is part of the problem, but it can’t hurt to replace them.

I also spent considerable time running the loco today at various speeds including the highest speeds. No problems, no lock ups, no derailments. The most recent derailment that prompted me to start this thread was on a faulty turnout that I have now replaced on the layout.

So, that is where the situation stands as of now. I am not sure what to do about adjusting the eccentric rod and crank. I don’t have any mini wrenches and I am not sure how easy or difficult it will be to adjust the position of the rod and crank. I have not yet checked further into the wear issue on the bearing or its surrounding housing. I may wait until the next lock up occurs or until the new springs arrive, whichever comes first.

That’s all I have to report at the moment.

Rich