Full Version: nachoman 2021 do something clallenge, part 3
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Well, the first challenge is about done, less paint and a few details.   

My second challenge will happen as it happens, and is just to encourage me to get out more.

So... how about a third challenge  2285_ Goldth

I mentioned this in the Hobo Camp Fire a while ago.  I have a MDC Harriman 2-8-0 kit from 20+ years ago that I never truly put together.  The superstructure is done, save a number plate. It runs, but doesn't do well on sharp curves due to the one-piece side rods.  Plus, right now I am using an old open frame motor.  At one time I bought an expensive can motor and flywheel that I thought would fit, then I thought would not fit, and now think I can make it fit.  And my tender is still a coal tender.  

My goals here:
1) Make segmented side rods so that it can negotiate 18" radius curves without slowing down.
2) Add an oil bunker to the tender.
3) Find a way to adapt the new motor and install it.
4) Any remaining details and painting.

Step one was to design an oil bunker and send it to be 3d printed.  I went this route because in the future I will probably want to convert more tenders..
Here are photos of the tender to be converted to an oil tender, and the motor I wish to swap out.  The motors are close in overall size, no wonder I thought years ago that it would be an easy swap.  Turns out the extra width of the can motor means it has to sit slightly higher.
The 3d printed parts arrived, and after looking at them I've come to realize I have some more work to do here.   The gearbox/motor mount design is fine, but looks like I did not make the axle spacing between the two gears quite wide enough.  As in maybe 0.1mm too close.  So I will tweak the design and try again.

The oil tank looks okay, but rivet details don't work well as well in this material when printed on a vertical surface.  For my HOn3 oil tanks, I printed the sides and top separately and glued together, but this time I tried all as one piece.  As a result, the sides are too rough.  This one is useable, but I either have to delicately sand the sides around the rivets, or sand the whole side smooth and use rivet decals.  But, the size is fine and the top looks great.   In any event, I need more for future tenders, so I have modified the design to print the sides and top separately and will likely try again.
I redesigned the oil bunker as a "kit" that I have to glue together.  The purpose is to make sure the riveted sides all face "up" to make them come out smooth.  It will take about 15 minutes to glue together and should look quite nice.

I also modified the gearbox so space out the gear axles a little bit more, but it is still too tight!   GRRR.  3rd times a charm, right?  One problem with 3d printing is that the parts aren't 100% dimensionally true.  Many methods are close enough for modeling purposes, but when you are trying to get gears to mesh well it can be a little trial and error.  I think that may be what happened here - the axle holes are about 0.1 mm too close together.
I am amazed with what can be done with the 3d printing. When it first arrived I was skeptical of its uses. Now I see otherwise.
Well, I glued the multi-part oil bunker together.  Didn't do the best job at it and glued my finger to the model at one point and broke off one of the lift rings, but I think it looks okay after a coat of primer.
(05-24-2021, 09:08 AM)nachoman Wrote: [ -> ].... glued my finger to the model at one point...

Well, we do get attached to our models, especially when we've invested time and money into them.

It's shouldn't be too difficult to fabricate a replacement lift ring using sheet- or strip styrene.

(05-24-2021, 09:33 AM)doctorwayne Wrote: [ -> ]It's shouldn't be too difficult to fabricate a replacement lift ring using sheet- or strip styrene.


And that is what I did.
Looking good!
Installed in the old Bachmann tender.  Needs some touch up painting, some new steps and a few grab irons.
Well, 3rd time is a charm.  This one finally works - and the gears mesh smoothly.  Still have to mount the motor, but my guess is this will run well.