736 berkshire problem update

[Anonymous]

 first I want to thank everyone for all the great tips from my last post "736 berkshire problem".

   I now have it down to a hunk of cast iron with 8 wheels. front two sets of drivers spun freely, third set was not too free. I had to drill a small hole under the pick up plate to get oil into the center of the axle.

   now here is what I think the problem is, the r/s rear drive wheel runs out about .020". I can't tell at this point if the axle is bent or the wheel was not drilled correctly. when under load in forward the gear set forces the axle to the left making the right wheel bind intermittantly with the wobble. I guess I will have to pull off the r/s wheel to see if it is the axle or wheel. the side to side play in the rear axle is .023, is that too much?  I was looking at shimming from inside the gear box but the space between the gear and sidewall is nearly 1/8". pretty thick shim. does anyone have an idea where to get a 736 axle and wheel if needed. I look forward to your responses. Thanks, John

 

[Mimbrogno]

Hey there, it sound like you're a man who knows a bit about machining! You should have the best running Berkshire on the block when your finished! A gap of 0.023" doesn't sound like too much. At least it's within tollerance for a running locomotive of it's age, but it would definatly be a good idea to shime the bearings. The best way to do a really good job is to take the wheels off, and fix the bend it has probably developed from resting it's weight on the axle for 50 years. If you do pull the wheels, I suggest using small bronze washer shims, placed between the wheel and the outside of the frame, to bring the gap to say around 0.005"~0.010" Use two washers on each side if you can, it will in effect create a bronze bearing which will reduce wear and take all lateral wear off of the original iron parts, making the locomotive last a lot longer. The gearbox might seem like a nice place to shim as it would be continuously lubricated, but getting the shimes, gear, and wheels all lined up is quite a pain in the hands. Not to mention the fact that having the shimes on the gear won't protect the axle from lateral motion which will try to bend it in the bearing. Shiming under the wheels will give a larger area to absorb such forces, and help to prevent the wheels getting bent again.

 Have fun with the rebuild!
Matthew Imbrogno
-Mechanical Volunteer, Arizona Railway Museum
www.azrymuseum.org

[lionelsoni]

I would compare the gauge among the axles.  The easiest way to do that is to measure the step between the end of the axle and the outside of the hub.  The wobbling wheel on the rear axle may be too far out, which would make it more likely to wobble.  In any case, you will probably find that the wheel can be straightened by pressing it off-center at the hub.  On the other side, press only on the end of the axle, so as not to disturb the position of that wheel.

[Anonymous]

the gauge on all the wheels are the same and so is the end play. I will try the offset pressing method and see what happens. right now I have stored all the parts in a large tupperware cause the wife says I have other prioritys at the moment. will see what happens next week. thanks again, John

[iguanaman3]

I have had a similar problem on a MPC UP Berk that I ran quite alot. One of the rear wheels loosened and would wobble from the strain of driving the rest of the wheels. The wheels are made of powdered iron and will eventually crumble under stress. I tried epoxying the wheel back on but it soon failed. I finally got a new wheel and it has run great ever since. I don't recommend removing sintered iron wheels unless you have a replacement a they are often loosened by removal and replacement.

Neil