N-Possible Coupler Announcement (Nashville 2022)

[GaryHinshaw]

@GaryHinshaw - Gary, what length M1.2 screws are you using?  Also, slot or phillips drive?  And, maybe you could tell us where you got 'em??

The ones I'm using are M1.2, 4 mm long phillips head:

https://www.aliexpress.com/item/1005002525560135.html?spm=a2g0o.order_list.order_list_main.4.1dd918021xwyDg

$2.05 CDN for 50 screws.  (I could not find a good cheap source on Amazon.ca.)  You might want to have a range of lengths between ~3 and 6 mm on hand for different installs, but 4 mm is a good starting point, and has been fine for all of my installs to date.

I also *highly* recommend a magnetic screw driver, such as this set from Ifixit: (might be a Canadian specific link)

https://www.ifixit.com/en-ca/products/minnow-driver-kit

Avoid slot-head screws if you can.  They're a real pain to get started.

[Maletrain]

What shank length do you recommend for (A) typical 1950s box cars and coal hoppers, etc. and (B) pilot couplers for Bachmann 4-6-0, (C) Bachmann 2-8-0 (Spectrum version), and (D) BLI USRA Mikado?

[Jim Costello]

Like Gary,  You can purchase Blackened steel screws thru Aliexpress very cheaply. Several years ago I purchased them in 3,4,6mm lengths in bags of 50 or 100 for about $1 a bag. They were countersunk ,Phillips head and I also recommend the magnetic screw driver bit.
Jim

[GaryHinshaw]

@GaryHinshaw  which (scale box) NPs do you use for the Rapido centerbeams?     What size curves can those negotiate, and do they need any subsequent lowering?

[Sorry for the overly long post.]

I made a 3d-printed retro-fit kit for the Rapido centerbeams.  Only one of the four pieces is for the N-P conversion, the rest are to otherwise improve the appearance and performance of the cars.  The parts file may be obtained here:

https://www.tinkercad.com/things/a7c1tKn3WMB-np-rapido-centerbeam/edit?returnTo=https%3A%2F%2Fwww.tinkercad.com%2Fdashboard%2Fdesigns%2F3d

Now that the N-P release is imminent, I'm planning to document my conversions in a new thread, but here is a quick preview of the centerbeam conversion.  The changes were as follows (listed in order from the centre of the car moving outward, with the N-P conversion listed at the end):

* Add a spacer block to make the air lines visible (the black piece just inboard of the inner axle):



* Replace the wheels with 36" FVM (or ESM) wheels.

* Remove the brake beam details from the trucks.  (It is prone to falling out, causing a derailment.)

* Add a stabilizing washer and bushing to the truck mount.  This does not change the ride height, it just makes the car track more stably.

* Trim the air line details behind the stock coupler box so it does not interfere with the wheels.   

* Replace the coupler pocket pad with a printed part that has the N-P splitter incorporated.  This is the black part (faintly) visible in the coupler box:



The conversion is fairly straightforward once you get the hang of it and (believe it or not) it makes these cars among the best runners in my fleet.  I don't know what the minimum radius is, but I can say that they navigate a 16" curve with ease, even when coupled to a shorty cement hopper:







I honestly could not be more pleased with the outcome.

[garethashenden]

Gary, when you're printing the splitter, how wide/thick should it be? Thicker than the brass shim I'd imagine?

[GaryHinshaw]

The splitter in my design is 0.15 mm thick (wide), 0.8 mm deep (along the track axis), and 1.2 mm tall.  This may not be the exact dimension that @turbowhiz has in his scale box, but it is at least very close and has been working well for me.

[Maletrain]

Warning: I tried to order the screws that Gary posted the link to at AliExpress, and had trouble trying to check out.  The site took my e-mail address and credit card and then immediately froze my account.  I am wondering if it is a legit site.  The same credit card had just worked with McMaster-Carr.

[GM50 4164]

Warning: I tried to order the screws that Gary posted the link to at AliExpress, and had trouble trying to check out.  The site took my e-mail address and credit card and then immediately froze my account.  I am wondering if it is a legit site.  The same credit card had just worked with McMaster-Carr.

I just placed a order with them as well, but I paid using PayPal. It is showing to have gone through for me and i received a confirmation email. I hope you can get it straignthened out.

[GaryHinshaw]

That's a bummer @Maletrain. Like @GM50 4164 I also paid with PayPal and had an immediate order confirmation.  The package took about 8-10 days to arrive from China.  I think it's a legitimate site...

[Maletrain]

Maybe it has a teriff problem with me being in the U.S. that you don't have being in Canada.  But, I did order the same thing from an eBay site that comes from China, without any problem.  Maybe they got hacked? Who knows that mysteries the internet holds?

Anyway, the same screws are available from a couple of other Chinese suppliers on eBay.  And they do have statements on their sites that the costs shown already include the tariffs. 

[pmpexpress]

Although they are not blackened, sold in lots of 1000 and 2000 pieces (the 2000 piece lots are quite a deal), listed on eBay are some M 1.2 x 4 mm Phillips Flat Head Countersunk Screws.

The seller also stocks M 1.2 x 5 mm and M 1.2 x 6 mm Phillips Flat Head Countersunk Screws.

[GaryHinshaw]

For what it's worth, I do not recommend countersink heads for the scale box installs. The indent for the screw head in the bottom of the scale box is better suited to a flathead screw, as you can see here:



The grip I get with these M1.2 flatheads is excellent: no box twisting and no shank compression.  The vertical clearance is generous, as you can see in this shot:



By the way, this is a short shank coupler in the scale box.  In the ~200 cars I have converted to date, I would guess I have used ~50% short shanks, 30% medium shanks, and ~20% long shanks.  But it depends quite a bit on the types of cars you plan to convert.

It's also worthwhile to be anal about coupler height consistency.  You first step should be to install a scale box in an MT-1055 gauge and use it on every install:

[peteski]

For what it's worth, I do not recommend countersink heads for the scale box installs. The indent for the screw head in the bottom of the scale box is better suited to a flathead screw, as you can see here:

Gary, screw nomenclature defines a flathead screw as the one which fits into a countersunk hole.

The screw you are using, while it does have flat surface on the top of its head, it seems more like a screw with a PF or binding type of head.
Knowing that might help someone with ordering the correct screws.

Yes I know that I'm anal, but I think you can relate. 

[Maletrain]

Gary, The drawing I have for prototype couplers indicates 33.5" center height above railheads for freight locos and 34.5" for passenger locos.  For N scale, I am just calling that 34 scale inches = 0.2125".  And that seems to be about where my MT-1055 coupler gauge puts the center of standard MicroTrains coupler knuckles.

Back in "reply #198", Turbowhiz posted "My 'ScaleBox' coupler mounts right into a 1055 gauge at the right height (by design)."  So, there is no need to shim the gauge to get the proper standard knuckle height in the gauge.  That is a good thing, because interchangeability for the smaller knuckle height seems to depend on close adherence to the standard height.

But, considering that the N-possible coupler box is thinner than the standard MicroTrains box, my understanding is that there needs to be a shim between the top of the N-possible coupler "scale box" and the bottom of an unmodified model car to get the prototype scale coupler height.  Or, the car ride height might be lowered by thinning the bolster or substituting trucks with lowered centers.  Considering the unprototypical ride height of many commercial N scale cars, that seems like a plus for scale modeling.

In "Reply 295" Turbowhiz posted "The "Hat" component that fits on the top of the box assembly . . . is designed to shim to height, as well as width, of a 1015/1016 type box."  So, my understanding is that the thickness of the "hat" is the amount that a car body could be lowered to work with the "scale box" without the "hat" to achieve prototypical couple height above the railheads.

So, can somebody tell me how thick is the "hat"?

[GaryHinshaw]

Knowing that might help someone with ordering the correct screws.

The Aliexpress link I gave above describes them as "Mini Small Phillips Ultrathin Wafer Flat Head Screw Bolt for Laptop Notebook Phone Glasses".    In the diagram you posted, they are closest to the cylinder head, or the one on the lower left (DE??).  I'd avoid screws with a taper between the head and shaft.