Best Of The Overland/Wiseman brass Western Maryland Shay thread

[u18b]

Thanks Bob.

The bottom is much thicker yes.

But the teeth themselves are also very fine.

Here is a gear on one of my Shays that was worn out from running without regular oiling.   I obviously had to replace it.

[u18b]

This has been an interesting experience working with an expert to cut such a precise and tiny gear.

The test gear arrived today.

Before I installed, I figured I needed to be able to do a good and valid comparison (before and after).
So the first step was to tune my backup tender truck.
It took me a couple of hours because it had some problems, but in the end I succeeded in the truck passing the incline test for smooth rolling.

So I turned my attention to the new gear.

Here it is (right) on my reamer with a stock gear (left).
He cut the hole at .9mm and figured I could bore it to my liking.
This shows that it only has a small way to go.




But as I was taking macro photos and looking at it under high rez..... it became clear this test gear has problems.






So I took some notes and sent it to the watchmaker.
The gear is close, but not quite there.

[peteski]

The shape of the teeth seems way off. The edge of the gear's tooth should taper to pointy shape and that shape should remain constant through the tooth's length. At least that is how the original gear looks like.  The new gear has its teeth get wider on the wide end.  They look like little wedges, not rounded-tip gear teeth.

[u18b]

I threw caution to the wind and installed the gear last night after I made the last post.

And amazingly.... it worked.

I'll post more when I have time and can take a couple of photos.

[u18b]

Before  I move forward, let me back up a bit.

I've been trying to help in solving this gear problem for a while.

This thread documents, not only what worked... but also what didn't work.

So I spent hours searching the internet looking for tiny gears for replacements.

I found something overseas I wanted to try - even though the odds were against me.

I found some very tiny bevel gears.  Unfortunately, these didn't work.   They were two small.
Here is a gear mounted on a shaft for experimentation.




I then came across this set- both a bevel gear and a crown gear.


Unfortunately, the bevel gear was too large for a Shay.

However, the crown gear has possibilities if I'm ever in a situation where I need a new crown gear.    It may needs some mods, but the overall size and the teeth number are correct.

So in the end, this search for something stock was a failure as far as replacing the stock bevel gear.

[u18b]

Back to the new cut gear.

I would say that it was 85% good.
It worked As-Is.... but was not perfect.
The very slight bouncing of the tender hinted at some minor cogging issues.

And then, every once in a while, the tender would hop- indicating a major cogging moment.

Finally, after leaving the room and then coming back and finding the Shay stopped- I decided to address the cogging issues by shaping the gear teeth by hand.

To shape a tooth of a 2mm gear, I needed something rough and sharp.

Here is a tool I had previously sort of created (or modded).   



This is a VERY VERY thin disc I got from a dentist.    These things are very expensive (about $70 for 2).   Because this is so flimsy, I mounted it on a dremel post sandwiched between two other thin discs with a narrower diameter- thus one very thin blade sticks out.

That blade is  .13 mm



I then... by hand... (I know, very imprecise), I shaped each tooth .... using the highest mag optivisor I had.

I started in the back and sanded the boxy back end.




I then went back and shaped the outer edge of each tooth.

[u18b]

Here is the install video.

First is the tuning test with the new gear as-created with the boxy ends.

Runs 85%.

Then a re-test after shaping the teeth.   You can see it moves at a smoother less-steep angle.   Now 100%.

Even though this is a bit amateurish..... I would call this a great success.

Shay is currently running non-stop on the layout for over half an hour running at about 5 scale MPH with no problems.

[Chris333]

That cut off wheel is probably Dedeco. You can buy a whole pack for that $70. They break when you look at them, but I've broke more of them with the tool shut off than I did while cutting. They are 0.005" wide and I use them to cut gaps in turnout frogs. Each pack comes with a mandrel.

https://www.dedeco.com/ultra-005-discs-7-8x-005-100-bx/

[u18b]

Thanks Chris,

Mine are about the same size.

Brand I'm using is Abrasive Tech 927-2

https://www.therailwire.net/forum/gallery/54/medium_1277-100626221134-54921555.jpeg

A single disc can run $40-50.  Diamond impregnated flexible stainless steel (for going between teeth, I think).

https://mvpdentalsupply.com/products/abrasive-technology-x927-7-thin-flex-double-sided-diamond-disc


Ebay has one for $25 right now.  Ebay listing does say Dencoa.  May be the same.
https://www.ebay.com/itm/226984418628

I started using these to cut a groove in the frame of the Milwaukee EP-2s.  A very fine groove was much better for soldering a handrail in place.

I've never broken one by keeping it sandwiched between two other discs.

[u18b]

The shape of the teeth seems way off. The edge of the gear's tooth should taper to pointy shape and that shape should remain constant through the tooth's length. At least that is how the original gear looks like.  The new gear has its teeth get wider on the wide end.  They look like little wedges, not rounded-tip gear teeth.

Here is what the watch-maker told me (for those who are gear-techies).

"The original gear is a spur gear, the one I made is cycloidal. "

Since he is a watchmaker, he's not set up to easily reproduce this gear exactly.
I have the impression that most watches don't have spur/bevel gears in them.

He said he could make one, but it would require a new tool/cutter etc. 
An exact reproduction would have driven up the cost.

So what happened, is that I took lots of measurements (which I shared here) and he cut what he did- knowing it would require a bit more work by me.

So in essence, the gear he sent me was the test gear..... and I got it to work.

Where we stand...
Alex with the broken Shay will decide if he wants to replace the gear or me.
And then figure out how many more of these gears we want as back-ups (cost will obviously be a factor).

Keith Wiseman is out of all significant parts... so I'm glad this option presented itself.

And credit goes to Alex for thinking of getting someone to cut new gears.

[peteski]

I wonder if NWSL could make those gears for you, and what their price would be?

[u18b]

I wonder is NWSL could make those gears for you, and what their price would be?

That's a good thought.

When the dust settles on all this, I may check.

[u18b]

After a couple of months…. I’m now ready to repair a Shay.

Short recap:
I rebuilt the Shay for someone and also installed DCC (a really big job).
Shay was then sent to a professional painted- who ruined a bevel gear when trying to remove it.

So we needed a new bevel gear (covered above).

Watchmaker made a test gear which I modified and got working in my back-up tender.

Watchmaker wanted to perfect the new bevel gear (requiring no mods from me) - but that was going to cost a fortune.
So Shay owner got 4 extra gears cut just like the test gear shown above.   I'll mod to get the final shape.

So everything arrived at my house this week.




Close inspection of the driveshaft shows that the other bevel gear is damaged too- either naturally from wear, or from getting bumped while trying to deal with the destroyed one (or both).

But my conclusion is that BOTH bevel gears need to be replaced (one was destroyed).   This is probably not such a bad thing anyway.

The big black ring is a delryn piece- not sure why it’s there- probably from the failed repair from the painter.   Upon further study- it’s because at least one of the tiny brass shim/spacers is missing.




Here is a stock Shay truck.  There are three spacers present.   Two fat spacers are just to the left of each gear.    But at the right journal box, you can see there is a very small shim soldered to the left of the journal box.   This is to restrict the moment of the shaft and keep the bevel gears aligned.








Here is what I have to work with.    This is the truck I have to repair.
The gear and the shim are not in the correct places.   I’ll need to get them off of the shaft.

Turns out the gear was loose.  So after gently filing off excess solder from the shaft, it came off.





As I was getting the parts off the shaft, something did not seem right.
Sure enough, I discovered the shaft was bent.    The steel is VERY soft and probably got bent when the other guy was trying to heat it up and move parts.

I’m going to try and straighten it.

[u18b]

My first task was to deal with the bent shaft.

I took a piece of standard K&S brass tubing and drilled the inside hole to 1.1mm.

I did that for a couple of reasons.   

First, I could slide the tube over the shaft and it would assist with visually seeing where the shaft needed to be bent.



It would also become a source for more shim/spacers since the stock shaft should have 3 and I only have one.


After using a variety of methods (the brass tube, rolling on the desk, good old eyeballs judgment, and comparing to a straight edge, I was able to get the shaft straight.




The next step will be to shape the cut gears.

[Chris333]

I bought a big pack of 1mm (and 1.5mm) shafting on ebay. Unless there was a reason to keep the stock shaft?