Pennsylvania A3 Switcher (Kozo)

[fumopuc]

Hi Kim, I like the jig.

[Roger B]

Wood always has it's uses   

I often wonder how accurate the quartering and rod bearings must be  There must be an fair amount of play to allow for suspension movement. I remember someone over tightening the drive chains on a small 2' gauge petrol locomotive. It promptly derailed on the first set of points it drove over 

[matthew-s]

Was that a bad call? (he asks in retrospect? - learning for the future.)
Kim

Well, as I’ve completed exactly zero model engines, I am no authority.  Others are better to ask.

I have made some jigs from wood. I am betting you will be all right. Setting the wheels is a low force activity.

 I have slight binding in mine in one part of the wheel revolution that I suspect will go away as the bearings are worn In.

I won’t personally cast stones at Kozo, but someone who seemed to have experience commented the specified tolerances are too tight for the realities of running a model steam engine over an imperfect track!

[kvom]

I quartered mine on a surface plate with the aid of v-blocks and gauge blocks, so quite precise in theory.  Any flexing when running is accommodated by the rods.  Once both axles are mounted to the frames you'll see how smooth the motion is.  Once I had the frame and axle assembly, a tow around the track was a good test.

[Kim]

Thank you Achim, Roger, Matthew, and Kvom,

Appreciate your insights and thoughts on this.  I guess we'll see how it turns out and have another data point on the accuracy of quartering

Thanks,
Kim

[Kim]

Chapter 13.1 – Side Rods

After Loctiting the pins in place on the drivers, I started work on the side rods.  To help make the side rods the correct length, Kozo creates a crafty little jig that lets you adjust the length between holes. It has one fixed pin and one that has an offset eccentric pin.  By rotating that pin you can change the length +/- by just a smidge.  But it seemed like a great idea, so today I made one.

It's all pretty simple operations so I didn’t show any specific machining except for the eccentric pin. After drilling a hole on center with the 7/16” portion of the pin, I offset it by 0.020” in the 4-jaw and created a slightly smaller eccentric secondary pin.


Here are all the pieces to the drilling jig.  When yo put the eccentric bushing in one side, you can rotate it and it will vary the distance between the two 7/16” pins by +/- 0.040”.  As I said, I thought it was pretty ingenious!


Here’s the jig assembled.  The fixed pin is Loctited into place. And the eccentric one is left to be able to turn.


Here I’m fitting the jig into the axle bushings on the engine frame.  Once I found the right distance between the axle bushings, checking BOTH the left and right side of the frames, I put a drop of Loctite on the eccentric bushing and left it to set.


Here’s a shot of the jig setting next to the axle bushings on the frame, just to help you see what’s behind the jig.


Next time I’ll be using that jig that is now set for the exact length of the side rods.

Thanks for taking a look,
Kim

[crueby]

Neat setup!

 

[propforward]

Excellent - yes very ingenious idea for that fixture. Definitely putting that one in the memory bank.

[Kim]

Thanks Chris and Stuart,

Yes, very slick little jig.  Of course, I can take no credit, it came straight from Kozo's book.  Or maybe the only credit I can take is having read the book! 

Kim

[Steamer5]

Hi Kim,
 Nice work on the jig.
If I’ve got it somewhere close to right, if your jig isn’t exactly 90 it isn’t the end of the world, as long as both are the same which your jig should do.
The side rod jig is a neat idea, if you have got it so it fits both side you have done some very good work!

Cheers Kerrin

[Admiral_dk]

Re the quatering - disclaimer I have never done any ....

Logic dictates that the angle isn't the most important - BUT that the angle is exactly the same on ALL driver wheels that are connected with siderods ....
If Not - you will get a more or less partly lockup when turning the wheels ...!

I wish that I could claim the origin for the siderod adjustment too Kim - simple and elegant.

[Kim]

Thanks Kerrin and Per,
Yes, that sounds right to me.  Guess we'll find out soon enough!   

Kim

[Kim]

Something I've been meaning to ask - does anyone know where you can get some 3.5" track?   I've looked around some and haven't found too many options.  At one time, I found a place where you could get a track-shaped piece of steel (I-beam kind of thing) that was scale size for 3/4" - it was like a 6 or 8 foot length. But I can't find that now.  I'd take pre-made track sections too, but I haven't been able to find that.

Any pointers would be very welcome!
Kim

[matthew-s]

Something I've been meaning to ask - does anyone know where you can get some 3.5" track?   I've looked around some and haven't found too many options.  At one time, I found a place where you could get a track-shaped piece of steel (I-beam kind of thing) that was scale size for 3/4" - it was like a 6 or 8 foot length. But I can't find that now.  I'd take pre-made track sections too, but I haven't been able to find that.

Any pointers would be very welcome!
Kim

Man, I'd love to know this too.

Research I did early on lead me down the path of "rolling your own" using LGB-sized rails and your own scale-sized wood ties.
That was really for static display purposes though - not for running from what I can tell.
I liked the idea but set it aside in lieu of model progress!

[crueby]

Something I've been meaning to ask - does anyone know where you can get some 3.5" track?   I've looked around some and haven't found too many options.  At one time, I found a place where you could get a track-shaped piece of steel (I-beam kind of thing) that was scale size for 3/4" - it was like a 6 or 8 foot length. But I can't find that now.  I'd take pre-made track sections too, but I haven't been able to find that.

Any pointers would be very welcome!
Kim

Kim,
Contact Jason at The Train Department, he carries a few brands. You can ask him for either individual rails or made up sections. I had bought a couple 6' lengths when I built my Shay, still have some and can mail you some chunks if you cannot get them elsewhere. They are shaped like the real thing, just smaller, and are available in a couple different metals. The makers are usually smalll home-businesses, and some from the past have gone away as they retired. Here is his website:
https://www.thetraindepartment.com/track-and-switches/

If you cant find what you need there, let me know!
Chris