Mack 45 ton switcher

[Chris333]

Also the gear ratios. You know how everything in N scale runs fast. The motors spin fast and they just transfer that to the wheels as easy as they can.

On this last chassis the motor will spin 66.6 times to get the wheels to spin once. So the higher the number the slower it will run.

The tiny gear on the motor is 12T, the big one is 40T. So The motor spins 3.3333333 times to spin that center shaft once. The Kato wheels have 20T gears so the center shaft will have to spin 20 times for the wheels to spin once. 20x3.3333333 = 66.6666666.

You can also factor in things like how fast a certain motor will spin, but once you reduce it with gears that it is less important.

Those older Kato pocket chassis were probably like 15:1 so they run kinda fast.

All this Star Wars high tech it just to make sure when I'm done it runs nice and slow.

[peteski]

Do I understand this correctly in that you are using the 3D-printed resin as bearing surfaces for the thick plastic axle tubes?  That sure is an unusual design.

I guess with such a high gear ratio, the friction of the (large diameter) plastic-on-plastic surfaces will not be much of an issue, and since this loco is not going to be ran 8 hours  per day on some hobby shop display, durability is not much of an issue either.   

[Chris333]

There are several other chassis out there that are made using a 3D printed chassis block.

I do not know if there are such a thing as 1mm ID bearings I could buy. But I can use hypodermic tubing to sleeve the lay shaft.

http://www.narrow-garage.com/NarrowGarage.html
http://www.tomamw.com/ca16/294/p-r-s/
This is a whole HOn30 Shay kit that is 90% 3D printed parts including all of the chassis
http://www.tomamw.com/ca34/288/p-r-s/

[u18b]

Also the gear ratios. You know how everything in N scale runs fast. The motors spin fast and they just transfer that to the wheels as easy as they can.

Well, not everything.     

 My brass Shay runs 7.6 scale mph with the throttle wide open-- actually slower than the prototype.

[Chris333]

In was a general statement 

I just ordered these bearings.
https://www.ebay.com/itm/384637200649
I will build up this chassis to make sure everything is fine. If those bearings look promising I can make the hole bigger to fit them.

[mmagliaro]

Beautifully made, Chris.  Your chassis is solid and elegant.
If you want just plain sleeve bushings with 1mm ID, look around the net for Bergeon clock bushings.  They make a few different styles with 1mm bore.

[Chris333]

Are the clock bearings bronze?  I have some bronze rod, I could make my own.

[peteski]

There are several other chassis out there that are made using a 3D printed chassis block.

I do not know if there are such a thing as 1mm ID bearings I could buy. But I can use hypodermic tubing to sleeve the lay shaft.

http://www.narrow-garage.com/NarrowGarage.html
http://www.tomamw.com/ca16/294/p-r-s/
This is a whole HOn30 Shay kit that is 90% 3D printed parts including all of the chassis
http://www.tomamw.com/ca34/288/p-r-s/

If I understand it correctly this loco uses outside-bearing wheelsets.  Wouldn't the easiest thing be to use the metal cups and pointy axles (just like factory Kato low-friction trucks).  That would also solve the electric pickup problem.  If the meta lplates are not available separately, just buy a 6-axle Kato truck, and extract the pickup/bearing plates.  If the spacing is wrong, cut those plates up and maybe solder them at proper spacing to a piece of brass?

[Chris333]

I have done that before and I have 3 Kato 6 wheel trucks now. I might do it. Instead of a hole I'll make a slot for the Kato wipers. When the poke thru the top I can solder them all together up there.

The wheelbase is off. That is why I made my own chassis. If I scaled the whole model off the Kato wheelbase, the locomotive looked too big.

[Chris333]

Pete made me do it.  I even made a 3D jig to hold them in place to solder. Put a piece of .020" wire along the back.



Now printing another chassis block with the notch to fit the pickups through. See that is how printing works. You think of something and print it. Then you think of something else and print another...

[narrowminded]

That will be worth the effort.

[mmagliaro]

Are the clock bearings bronze?  I have some bronze rod, I could make my own.

The sell both: brass and bronze.  You'd want to be sure to get the bronze ones.
And yes, if you have a 1mm drill (or slightly smaller), you could just make your own from some phosphor bronze stock.

Another option would be to swipe the bearings out of some old Kato GS-4 drivers (the ones with all the cracked axle tube problems).
Those were very tiny, and are 1mm bore.  I know this because I used them in my "Rocket" model.

[peteski]

That will be worth the effort.

Yes, I'm also glad Chris went that route.  There are probably tens of thousands of N scale locos out there successfully using this bearing/pickup design.

[Chris333]

I sure hope this is the last re-design 

The sideframes needed a little tweaking after the Kato pick-ups were in there. Once I got the sideframes to fit they sort of trapped the pick-ups so there would be no way to take it apart once they were glued on. So I make them screw on at the 4 corners.





I haven't ran it yet because I'd need to glue the worms to the shaft. To get that apart I'd need to soak in Acetone. So I'll wait for the bearings to show up.

[peteski]

Did you put enough screws in there?  And I thought I over-designed things . . . 
Seriously dude , that's awesome!     I still can't get over that you can just design and manufacture models at home. Scratchbuilding on a whole new level.  Welcome to the 21st Century.