Progress on Nn3 Mine Equipment Project

[Chris333]

If you look here at the bottom of the page they make these cars in On30:
http://www.btsrr.com/bts7240.htm

[narrowminded]

I take it that the wheelbase is so small, so the car can negotiate some tight curves.  But, dang, that thing looks like it should fall over!   

DFF

Yes.  One of the problems is the coupler overhang from center.  It makes for quite a swing on tighter radius turns.  This applies any time that the coupler is a big distance from the wheel pivot.  I'll make some but for really tight radius track I may have to spread the axle C/L's.  A longer link or drawbar may help this, too.  I will will build some and test to find out what really works.  I'm especially worried about backing cars with this issue.

[narrowminded]

I started working on this @Chris333 .  It is TINY even as Nn3 goes.  The wheels should work but I'm still worried about the wheelbase and coupler overhang for reliable operation.  The tolerances will have to be very tight if there's any hope which makes this scale challenging, but fun for me.   

I am going to go back at the wheel design and narrow the spokes some more.  They look pretty good as they are but I think they can be a little better.  With those small holes and walls in close proximity the spokes do print about .002" larger than drawn and .002", when the part is .009", is a full 20%+ change.  I will adjust it as it seems good in all other aspects, strength being a big one.

[Chris333]

Peer pressure! 

[narrowminded]

I got some time on the Nn3 wooden ore car.  It is TINY.   These are progress photos to make sure the functioning parts will function and the details are printing OK.  The white primer is fresh so I'll wait until it dries and shrinks to give it a good look but at first glance all seems OK.  Many more details to complete including end door, brake parts, coupler, and such but I think it's going to be a good one.

And the pics:

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[Chris333]

So you made a working door?

[narrowminded]

So you made a working door?

It will be a separate piece at least with a wire through the top hinge.  I may make it operate too but would maybe make that optional as it will be time consuming to build like that as it will then need a functioning latch of some sort.  Did I mention that this thing is really tiny?   I suspect the brake parts will be separate parts too, if only for access for painting.  Plus, they wouldn't necessarily go on every car.  From reading I've gathered that at least some operations only used brakes on maybe every fifth car or so.

[narrowminded]

Got some time on the wheels today.  Thinner spokes and true NMRA RP-25 dimensions used in the design.  Because they are inside bearing and that's a concern for friction, the design uses very small diameter, very smooth finish, .015" dia. SS spring wire and the axles are retained in the chassis in a free fitting rectangular pocket with a .010" pad at the top that serves as the bearing.  These are so light and so small that even weighted as much as possible they still won't weigh much at all so there isn't much concern about wear or the need for a big bearing surface.  This makes for a surprisingly smooth, free rolling little car.   I'm happy this far.  Think the old "Hot Wheels" car designs and their axle size for an example of the concept.

Here are some pics.  They are staged on an assembled piece of track using the Code 40 Nn3 flex ties that were made about a week ago.  That design too is working well and when assembled is right in gauge, first time, every time.  I'm having huge fun seeing this progress on a several year old project.  The technically hardest parts are thoroughly tested and ready to be applied but the volume and lots of grind it out hours to complete the line remains with this kind of stuff.  The 3D printer is helping move that along at a previously undreamed of pace.

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This one shows the .008" PB wire that will be hanging the end door.  I may make it operational.
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[davefoxx]

Very impressive, Mark!

[MK]

Mark, for pictures going forward with the ore car and wheels, increase your exposure by half to one stop so we can see the details of the wheels.  Right now the camera is exposing for the white car making the wheels look dark and hiding the details.

[narrowminded]

Mark, for pictures going forward with the ore car and wheels, increase your exposure by half to one stop so we can see the details of the wheels.  Right now the camera is exposing for the white car making the wheels look dark and hiding the details.

F stop?!  I don't think this phone has that option.   And if it does, I sure don't know where it is or if I did, what to do with it.

I know what you mean though and figure I will have to do something about that at some point.   Right now that hasn't made the priorities list but will have to at some point.  Even just adjusting the positioning to improve the lighting would be helpful, I'm sure and recently demonstrated to myself, but right now I'm just taking those in lieu of my normal lifelong approach of taking no pictures, ever.     Sometimes I wish I had but I do have a variety of some key events as taken by others.  As far as appearance, that wheel is just over 1/8" diameter (.137"/ 3.5mm) and the detail is pretty darn good, especially with the naked eye.  And they roll very nicely, not much different than a typical truck as far as my limited testing has shown.  The proof will be in a train of these inside bearing pieces vs: needle point axles and how many of each will that little mine engine pull. 

Nothing was done with those parts fresh from the printer beyond washing them in alcohol, curing them in the UV light, and then some Neolube on the wheels and a squirt of white primer on the body.  At this point they are all test pieces and will receive minor modifications for the final rendering.  And my dirty fingers are getting that white primer body looking pretty hagard.

[CRL]

I find dirty fingers to be a reasonable weathering method.

[Angus Shops]

I find dirty fingers to be a reasonable weathering method.

Ha! Brilliant!