N Scale Business Car Build (NS/PGE/BCR/BCPM)

[BCR 570]

Thank you John; I see what you are referring to.  I will have to think of how to create those notches.  It would be nice to have the roof snap into place, but if not, I can perhaps remove the ridges and tack it in place with canopy glue or something else.

Tim

[BCR 570]

Assembly of Etched Sides (cont.)
I am continuing to experience issues with the top etched layer lifting at the ends.  I am guessing that the inherent curl is causing this:




I decided to to try thin CA in place of medium CA to see if would adhere any better:




I am keeping weights on the sides until such time as I glue them in to the shell.

I will have the same problem with the underframe parts which have an inherent curl, so am going to de-sprue those and try the hot water and weight method to see if that can be mitigated.

I picked up a Rivarossi observation car at the Nanaimo train show on Sunday, which I wanted for the curtain above the rear platform.

I also need to find some nice low profile 36" metal wheels for this car.


Tim

[nickelplate759]

Wheels are easy - ESMC has some here: https://www.esmc.com/9200/Item9202.html

[BCR 570]

Preparation of Underframe
It occurs to me that while the sides are out of the shell, there is an opportunity to clamp the underframe parts to the floor of the shell for a nice tight bond.  Unfortunately the underframe parts also have some inherent warpage, so it is time to de-sprue the parts and try to fix that.

I used cutters to chop through all of the supports:




I then used a sanding stick to clean up the edges:




Here are the underframe parts along with all of the fittings:




The underframe parts fit into the underside of the Micro-Trains shell and surround the bolster holes and the front coupler pad:




I now need to address the warpage in the underframe parts as I do not want the shell floor to take on the same warpage once those are installed.  I will try the hot water and weighting trick.

I am also missing the rear coupler mounting, as the Micro-Trains shell ends at the rear wall ahead of the observation platform.  It must be part of the underframe for the Micro-Trains observation car but I cannot seem to locate it.


Tim

[BCR 570]

Preparation of Underframe (cont.)
I decided to give the hot water treatment for warpage a try.  I soaked the underframe halves in hot water:




I then placed them on two strips of styrene as they have a tab for locking into the shell on their topside, and applied weight while they cooled down:




The first treatment did not make much of a difference, so I tried again with hotter water, a longer soak, and longer weighting afterwards.  This time there was a noticeable correction of warpage.  John LeMerise has kindly supplied a weight fashioned from tungsten weld rod which slides into each half of the underframe:




My plan is to clamp the underframe halves onto the underside of the body shell while the sides are out, as this will not be possible once the new sides are added.  There are a few issues to overcome.  The shell has a ridge underneath the rear wall which prevents the rear half of the underframe from sitting level.  Also, I am missing the rearmost portion of the shell which provides the locating holes for the rear platform and a pad and mounting hole for the rear coupler.  I do not seem to have the original Micro-Trains underframe but I have one for the business car.  I think that my best option is to cut off the rear portion of this underframe and cut the equivalent length off the rear Keystone underframe part.  This photograph shows the Keystone underframe, Micro-Trains business car underframe, and observation shell (upside down):




This will provide me with the locating holes for the rear platform and the mounting pad for the rear coupler.  The steps are not correct so I will have to cut those off and replace them with the Keystone steps.

I also sourced a banged up Rivarossi heavyweight observation car at a recent train show which will provide me with the curtain above the rear platform.


Tim

[Lemosteam]

Ah, so the obs shell is shorter overall than the car the underbody parts were designed for.  Yes the bolster boss locates the underbody rails, but I think you might have to shorten the pin that snaps into the slotted holes in the original shell, looking at the slot location relative to the bolster boss.  Trimming off the end of the underbody rails with a razor saw in a miter box and fitting the original coupler end up to it the new cut should work.

Glad you were able to remove the warp and that the tungsten parts arrived Ok.

[BCR 570]

Ah, so the obs shell is shorter overall than the car the underbody parts were designed for.

Yes, the observation and business car shells end at the rear wall, and the underframe extends past to accommodate the rear platform, steps and coupler.

I think you might have to shorten the pin that snaps into the slotted holes in the original shell

Actually your underframe fits the observation shell without modification, except for the ridge beneath the rear wall, as seen here:

Trimming off the end of the underbody rails with a razor saw in a miter box and fitting the original coupler end up to it the new cut should work.

That is my current plan.  I might make the joint halfway along the tab so that both pieces plug into the shell.  The top side of the Micro-Trains underframe has locating holes for the rear platform:




The underside has the steps and mounting for the rear coupler.  I will have to remove the steps and replace with yours to get the older correct style with three treads.  If I could locate the missing underframe for the heavyweight observation, it would likely have the correct older steps . . . . .


Tim

[BCR 570]

Preparation of Underframe (cont.)
I proceeded with cutting the underframe parts this afternoon.  I began by cutting off the rear of the Micro-Trains business car underframe just behind the centre block aft of the bolster hole:




Next, I took one half of the Keystone Details underframe and cut off the rear portion in the same location:




Here are the resulting parts after some dressing of the ends with a sanding stick:




And here they are sitting underneath the Micro-Trains heavyweight observation shell:




As you can see, I managed to get a nice joint between the two pieces:




From the topside, you can see that I managed to preserve part of the tab engaging the shell from each part.  This view also shows the rear platform in for a test fit; this part dictates exactly where the Micro-Trains underframe portion goes:




So I guess the next step is to glue and clamp these in place, and I can then install the new sides.


Tim

[Lemosteam]

Nice!

[BCR 570]

Nice!

Thank you; process went well.

Tim, unless you have removed the beads from the flange on your roof that snap into the grooves in the old sides, you would need to add them into the styrene you just added, else the beads will spread the updated shell.  Something to consider before you adhere the new sides to the old chassis.

Actually I think I will be okay with not adding the notches or removing the beads.  I went to mark the locations on the top styrene piece behind the sides and discovered that it is thinner than the distance from the roof down to the beads, so the beads will clip in just beneath this styrene strip:




Today was spent receiving a CAD tutorial from a friend and drawing up some appliance parts for the underframe and some hatches for the roof.  I have to figure out how to get the little rectangular roof vents done.  The best option would likely be to have them etched but that might be cost prohibitive given their tiny size.


Tim

[BCR 570]

Thoughts on Assembly (cont.)
I have spent some time figuring out how to glue the underframe pieces to the shell and obtain as flat a glue joint as possible.  I assembled a styrene block the same height as the rear wall and placed the shell on it upside down against an aluminum block.  I then placed the first underframe piece underneath the shell and clamped it in place in several locations for a dry test:




This seems to keep the underframe flat against the shell floor.  I think I need to glue in one half at a time to focus on positioning and clamping.  I can install the second half later by bending the floor downward, inserting the tungsten rod and then bringing the floor back against the second underframe half.  I can then glue the Micro-Trains rear underframe portion in place.

It is possible that the floor will take on a curve after de-clamping due to the residual warpage in the underframe halves, and most likely in the middle but perhaps the two-inch tungsten rod will help to counteract that to some degree.


I have also been thinking about how to attach the sides.  They need to be level with the top of the rear wall so an upside down assembly would seem to be in order; however this is complicated by the fact that the front end wall is higher than the sides above the front vestibule.  This means that the shell will not sit level when upside down.  I also need a way to keep the floor from bowing up or down when the sides are installed.

As mentioned, I assembled a styrene block the same interior height as the rear wall:




I sat the styrene block on top of an aluminum block and then placed the shell upside down on the styrene block with the front end hanging off the end.  Now the shell sits perfectly level upside down, and the styrene block will keep the floor level during installation of the sides:




With the shell sitting upside down on the styrene and aluminum blocks, I can now place the sides upside down on the aluminum block, slide them up against the edges of the front end wall, and then glue them in place.  This is a dry test of that arrangement with the right side sitting in place:




So, good to work all this out ahead of time.  Now for some critical assembly steps on the way to a complete carbody!


Tim


Tim

[dandopinski]

That's some delicate surgery there! I appreciate the step by step process.

[BCR 570]

Thoughts On Assembly (cont.)
Well it would appear that the ability of the hot water treatment to counteract the warpage in the floor is temporary, as the warpage has returned.  I think I will give it one more try just before gluing it in, to give the adhesive a fighting chance.

During my clamping tests I noticed that there was undue strain on the centre sill, and one of the centre sill pieces actually cracked.  I need a way to clamp the underframe securely to keep it flat without damaging it.

I fabricated three clamping jigs from strip styrene for this purpose (pictured below).  The one at left sits on the end of the underframe and serves to clamp the two extensions either side of the coupler pad in place.

The other two straddle the centre sills and serve to keep the underframe flat without damaging the centre sills:




This photograph shows the clamping jigs in place on top of the underframe.  You can also see that I added another layer of styrene underneath the support block so that the front end wall can hang off the end:




Here you can see the clamping jigs in place during another clamping test:




This arrangement should ensure a flat underframe during gluing, but I suspect that the shell floor will take on the warpage once released from the clamps.  I will have to hope that the glue joints with the sides will help to keep the floor straight once they are glued in.


Tim

[Lemosteam]

Tim, at this point I would recommend sawing two kerfs across the sills to relieve the strain.  These kerfs can be easily filled after the underbody is glued down and should prevent the warp being transferred into the soft plastic of the shell.

The appliances will hide them after the fact as well.

My parts never experienced this on my test model, and are still flat after many years.

[BCR 570]

Thank you John; yes that would relieve the tension in the parts.  Before trying it, however, I wanted to try a tip someone else gave me while at the Calgary Supertrain show, which was to hit the part with a heat gun and then hold it flat while it cooled.

I did this just before installation and boy did it work well.  Maybe the difference is dry heat as opposed to wet.  Without the tension in the parts I was able to get good glue joints -see next post.


Tim