Author Topic: Nn3 1922 Mack AC Railbus  (Read 1261 times)

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160pennsy

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Nn3 1922 Mack AC Railbus
« on: January 27, 2020, 03:38:20 PM »
+4
Purchased this Nn3 3D printed kit designed by Tom Knapp on Shapeways. Initially he wanted to release it in cast metal but chose to put it up on Shapeways instead. The kit is made to fit a Searails PowerMAX with the front geared axle removed and a new bottom plate installed.  A Micro Trains Z-Scale Andrews truck is mounted in front with the coupler & draft gear cover removed. I added Fox Valley Z-Scale 33" metal wheels. The front & rear headlamps are made to fit nano LEDs. Some of the details on the shell are VERY fragile and care must be taken to avoid damaging them (I broke off the front headlamp and both rear stirrups but will replace them later with a small styrene tube and soldered brass wire).

https://www.shapeways.com/product/RBNG7JQEH/1922-mack-ac-railbus-n-nn3













The Railbus runs ok as is on my test track but there is room for adding weight inside the shell. Also might need to add electrical pickup to the front truck since only the two wheels on the PowerMAX are providing juice to the motor.



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Chris333

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Re: Nn3 1922 Mack AC Railbus
« Reply #1 on: January 27, 2020, 03:47:14 PM »
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Wow that is turning out great!

GaryHinshaw

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Re: Nn3 1922 Mack AC Railbus
« Reply #2 on: January 27, 2020, 08:45:27 PM »
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Very cool!  I think we need the proverbial oversize penny in one of these shots to really gauge the size though. ;)

Chris333

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Re: Nn3 1922 Mack AC Railbus
« Reply #3 on: January 27, 2020, 08:55:48 PM »
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Now if I could just get that file for the Photon...

160pennsy

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Re: Nn3 1922 Mack AC Railbus
« Reply #4 on: January 28, 2020, 09:35:12 AM »
+1
Wow that is turning out great!

Thanks Chris. BTW I had to swap out the rear geared axle on the PowerMAX since there was noticeable wobble during the initial test run


Very cool!  I think we need the proverbial oversize penny in one of these shots to really gauge the size though. ;)

Per your request Gary




Now if I could just get that file for the Photon...

Chris, you might try getting in touch with Tom Knapp regarding the file. I have drawings & protype info if you want me to forward the links.
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randgust

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Re: Nn3 1922 Mack AC Railbus
« Reply #5 on: January 28, 2020, 10:58:16 AM »
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I got a FUD-printed Mack AC and had the same issues - even getting the parts out of the bag shattered the front suspension springs.

Resin would be a whole lot tougher here and probably a better surface.

Now, here's a tip.  If you don't mind blowing about $20 for a Rokuhan Z shorty, that would give you a perfectly usable 4x4 idler pickup truck with all metal wheels in Nn3 (Z) to replace that front truck with.   That's what I'm using on my Climax adaptations and its working really well.   

As cool as this is you'll have a devil of a time getting it not to stall with only one pickup axle; that front truck could be changed out.   I have measurements and photos of that idler truck if you need them - PM me.

The Shorty SA chassis run like rockets but the basic geared truck, etc. are pretty good quality.  I got mine from Plaza.


Missaberoad

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Re: Nn3 1922 Mack AC Railbus
« Reply #6 on: January 28, 2020, 11:38:19 AM »
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Nice job on the build, looks amazing so far...

I would love to have one in standard gauge.
It would make modeling Winnipeg Hydro very tempting...



Ryan in Alberta

160pennsy

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Re: Nn3 1922 Mack AC Railbus
« Reply #7 on: January 28, 2020, 12:26:30 PM »
+1
I got a FUD-printed Mack AC and had the same issues - even getting the parts out of the bag shattered the front suspension springs.

Resin would be a whole lot tougher here and probably a better surface.

Now, here's a tip.  If you don't mind blowing about $20 for a Rokuhan Z shorty, that would give you a perfectly usable 4x4 idler pickup truck with all metal wheels in Nn3 (Z) to replace that front truck with.   That's what I'm using on my Climax adaptations and its working really well.   

As cool as this is you'll have a devil of a time getting it not to stall with only one pickup axle; that front truck could be changed out.   I have measurements and photos of that idler truck if you need them - PM me.

The Shorty SA chassis run like rockets but the basic geared truck, etc. are pretty good quality.  I got mine from Plaza.

Hello Randy. Agreed that resin would be a better choice with more durability. If Chris succeeds in getting the .stl file then maybe we’ll see how the Photon prints turn out. Since the PowerMAX are currently unavailable then the file could be edited to use the Showcase Miniatures Nn3 power chassis instead. The Z Shorty idler truck wheel base is too long to replace the MT Andrews front truck. What I might try are these phosphor bronze axle wipers from SBS. Maybe stack two (with thin nylon washer in between) on top of the MT truck with one wiper going to each axle.



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randgust

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Re: Nn3 1922 Mack AC Railbus
« Reply #8 on: January 28, 2020, 02:03:44 PM »
+1
I've spent a lot of time tinkering with critter drives, and the curse of tiny stuff is always pickup and weight.     On my trackmobile, I could make it run on straight level track, but even the alignment of a curve was enough to tilt the axles so that one wheel of four would lift and it would run erratically.

Ended up putting on the scale test car just as a dummy pickup truck, and that beat it.   It's a champ now.   Same thing with the Burro crane, mated it to a flatcar with 8x8 pickup (Kato caboose trucks) and it's completely steady.

I've done a series of GE 25-tonners, if I can get the one axle to flex a bit I'm OK until I hit a turnout, then I better be moving as one wheel will always drop enough to tip the opposite wheel out of contact.   Developing an equalized suspension on a truck that small has made me nuts.   And you just can't have a plastic frog turnout anywhere.

So, given the choice between a wheelbase being a bit long, and constantly nudging it with your finger when it stalls.... just sayin'.  You have the advantage that the front truck can flex even if the rear axle is fixed, but there's no such thing as too much pickup.

But that's such a cool build.   Meanwhile, I'm still studying hirail truck concepts like Ron Beardon did once.   

 I noted that there's a bit of a schism between Searails on the power truck and Showcase on the Climax/Shay kits; Walter seems to be intending to develop his own drive unit and Searails is trying to make their own Shay:   https://www.showcaseminiatures.net/n_scale/n_scale_locomotives/5006.html
Searails http://www.searails.com/shay/shaystatus.html

There's a story there somewhere..... I won't speculate.     I'm a huge Walter Vail fan though on everything he's done.   And he's proven that if something actually works he can do it in pewter - the Nn3 log cars moved from way-too-light FUD over to pewter and they are great.   Only reason I did my Nn3 Climax A was the availability of Walter's cars.


160pennsy

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Re: Nn3 1922 Mack AC Railbus
« Reply #9 on: January 28, 2020, 04:13:48 PM »
+1

So, given the choice between a wheelbase being a bit long, and constantly nudging it with your finger when it stalls.... just sayin'.  You have the advantage that the front truck can flex even if the rear axle is fixed, but there's no such thing as too much pickup.

But that's such a cool build.   Meanwhile, I'm still studying hirail truck concepts like Ron Beardon did once.   

 I noted that there's a bit of a schism between Searails on the power truck and Showcase on the Climax/Shay kits; Walter seems to be intending to develop his own drive unit and Searails is trying to make their own Shay:   https://www.showcaseminiatures.net/n_scale/n_scale_locomotives/5006.html
Searails http://www.searails.com/shay/shaystatus.html


Randy, trying to use that Z Shorty idler truck would require moving the bolster hole back so that the truck can swivel without hitting the back of the cow catcher - too much work! I agree that more pickup is the way to go so I’ll first try the SBS axle wipers or second choice, the home made version using thin .012 PC board with small phosphor bronze wipers that Tom Knapp documented in N-Scale magazine Nov/Dec 2016. Still searching for a source that sells low quantities of the  .012 copper clad PC board material.

I priced out one of the Searails custom order Nn3 Shay’s and it’s around $424 RTR. Now that Walter Vail has his own Nn3 power chassis that fit his Nn3 Shay & Climax kits a more affordable option is available for those who don’t mind building kits.

For those modelers looking for small 4 wheel power chassis in N & Nn3 in various wheel base lengths (looks very similar to the PowerMAX) there’s a vendor in Japan (scroll down towards the bottom of the page) selling them for approx $49. I might order one or two to see how they perform.

http://www.narrow-garage.com/NarrowGarageE.html
« Last Edit: January 28, 2020, 04:16:00 PM by 160pennsy »
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Chris333

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Re: Nn3 1922 Mack AC Railbus
« Reply #10 on: January 28, 2020, 04:28:50 PM »
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I bought a couple of those Japan chassis. The main part of the frame is just 3D printed resin so they are light, but otherwise work fine.

160pennsy

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Re: Nn3 1922 Mack AC Railbus
« Reply #11 on: January 29, 2020, 08:33:36 PM »
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Work continues on the Railbus - I first built a new headlight out of styrene tube and a bracket underneath filed to shape from square stock. To keep it from breaking off again small holes were drilled in both the shell and bracket and brass wire was used as reinforcement. After gluing it to the shell I checked to make sure a nano LED would fit.







Next step was to replace the rear stirrups that broke off while taking the shell out of the Shapeways bag! Bent two u-shaped stirrups from .015 brass wire and then soldered a third wire in the middle. Drilled holes in the shell where the originals were located and then CA’d the wires from inside the shell. I think the headlight & stirrups came out ok. The grab irons on either side of the doors will be added after I spray some primer on the shell to see if any sanding is required. Have not picked out what color to paint the body. Need to see some more prototype photos in color first.



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Santa Fe Guy

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Re: Nn3 1922 Mack AC Railbus
« Reply #12 on: January 30, 2020, 05:13:23 PM »
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That Mack looks super cool. Great work.
Rod.
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