Tuesday, August 2, 2016

Building SP 5199 (Part4)

In the previous posting, Building SP 5199 Part 3, I put down the final coat of Dark Olive Green paint and decalled the car.

Today we will cover installing the Hi-Tech Diaphragms (Western Short in this case) and installing the couplers at the right spacing for close coupling.  These two steps are highly critical to the operations of a passenger car, primarily to ensure there is no fouling of the diaphragm or binding which often cause derailments.


Left-to-Right: Striker (etching), Plastic Strikers (right one with installed bellows), Bellows sprue, rubber leaf springs, etc.

Diaphragms are fitted to any passenger car in which persons must cross between while the train is in motion.  They have bellows on each side made out of rubber or heavy canvas.  A Striker plate which is designed to rub against the striker plate of adjoining cars or engine Buffer Striker.  The striker plates are sprung with leaf springs top and bottom.  Some diaphragms are also fitted with anti-rattle bars which apply spring force to the left and right edges of the diaphragm to ensure the striker doesn't pivot left and right and risk opening up a gap between the strikers, which would highly dangerous.  Often the diaphragms between two coupled cars are made safer by connecting across rubber aprons from the door frame of one car to the door frame of the other car to ensure no fingers or hands are caught in the press of the two strikers plates.

Hi-Tech's diaphragms are very nicely rendered in multiple materials.   On this car I'm using the Western Short type diaphragm kit.  Hi-Tech also offers a Common Standard profile as well.  The kit includes plastic inner striker plate, and bellows to mount to the car end and another set to mount to the striker plate.  There are rubber leaf springs.  Once the springs are glued they don't allow the striker to fall off the car.  There is also a pair of stainless steel etchings for the actual striker faces.

Partly assembled Hi-Tech Diaphragm kit.  Notice broken section at lower right.

I've installed at least a dozen of these diaphragms so far.  The particular set I pulled out for this car had some breakage on one section of the bellows.  This isn't a real problem as the break happened on a piece that will be glued together and will be plenty strong when complete... Just don't loose the parts until then!

Prior Prep Work

On my SP 5124 and SP 5069 builds I found that it's ideal on Southern Car & Foundry passenger cars to have extra clearance for the inner bellows of the Hi-Tech Diaphragms for more retraction of the bellows into the car-end while negotiating curves.  I start these modifications by marking out the area to remove with Dremal motor tool with a burr-type bit.  Burr cutters are ideal for this as they have multiple cutting knobbs and will always keep several cutting edges in contact with the work, reducing chatter.  Normal fluted endmills, even 4-fluted ones tend to chatter too much for free-handed cutting.

ALWAYS BE CAREFUL using any type of motor tool for cutting.  I always rest my forearms, palms, etc against solid objects during this operation to keep the work and motor tool steady..

Double Check that the area to remove will be enough for the "outer bellow" to still fit.

Rough milled end of car.  Some cleanup with a file and No.11 Xacto blade follows.

Small amount of filing at the top of the car end to flatten it so the bellows will fit flat and properly.  Testors Canopy Cement is used to glue the outer bellow onto the end of the body.

Assembling the Strikers

The I start by removing the diaphragm bellows from their sprues.  There are two parts; one which is a thinner part with a flat back, this mounts to the plastic striker.  The other is a full form of one scallop of folded canvas.  This glues onto the thinner part to form one-and-a-half folds of bellows on the striker part of the diaphragm assembly.  This assembly telescopes into the bellow half that is mounted to the car end.

Because of the broken thinner bellow part, I mounted it to the striker first.  Then I glued the broken fragment in place with liquid plastic glue.  Once this is done, the fracture can't be seen.  The full bellow piece is then glued on top of the thinner one.  There is a front and a back to this part.  Make sure that it sits properly into the thinner part before gluing.


There's some glossiness from the liquid glue on the back of the striker.  This will all be covered with paint later so it doesn't matter.  Notice there are two small nubs at the bottom of the plastic striker.  These are to mount the anti-rattle bars, if used.  Most of SP's older Harriman/Arch-Roof HW cars didn't have the anti-rattle bars.  A few of the diners and lounges upgraded in the late 1930s seemed to have been fitted, but it was a car-by-car basis.

The Etched Striker Plate is glued to the outer face of the plastic Striker with ACC glue.  I "painted" the etching once installed with Sharpe markers.  I generally use black (grease) and brown (rust) colored markers.  Sometimes I'll do a little bit of paint as well, but whatever you do, Don't make the striker sticky.  They must slide effortlessly on one another while going around curves, etc.  The Sharpe will tend to rub off if there's any serious contact or scraping.  Which actually looks realistic as there would be some bare metal parts of the diaphragm strikers where the friction rubbed off the rust and grease.

I trimmed a small amount, about 0.015", off the bottom of the striker bellows to ensure that they will easily fit into the car end bellow.

Mounting the Strikers

The rubber leaf springs hold the striker to the car body.  There are two ways I do this.  The Hi-Tech recommended way is to drill holes for the "legs" of the leaf springs to be mounted into the car body.  On car bodies that I can easily drill into this works.  On brass car bodies, I prefer to cut off the "legs" and ACC the rubber leaf springs directly to the car end.  Since this is a resin car body, I drilled No.61 holes at the top and bottom of the car end bellows.  I've found that I like to go slightly narrower with these holes than the instructions state.  Making them narrower will force the leaf springs out farther from the car end.  This is good on the models because it will keep the bellows from "going solid" against the end of the car body.  This is why I milled out the inner profile of the bellows on the car end several steps previously.  Also this extra space gives the diaphragms extra movement for tighter curves etc.

The upper holes are drilled just below the eave-line of the roof.  On some models there's no option but to make a pad higher on the roof line and mount the upper leaf springs higher.  The bottom holes are drilled about half way between the bottom of the car-end bellow and the bottom of the end sheet.

I always mount the diaphragms before the couplers so I can adjust the coupled length to the actual diaphragm length.

The leaf springs have a small tab which is designed to fit into the square hole in the back of the plastic striker.  Usually I ACC glue the leaf spring to the striker.  On this car with the legs still on the leaf springs, I reversed this and mounted the leaf springs to the car end first.  The trick is always mounting the second side, whichever way you have started.  I put a small drop of ACC glue on the tab and then carefully pressed it into the hole on the striker.  This is a bit trick, as it has to be done accurately the first time.

One slight problem was that when the upper leaf spring was glued it, it took a downward set.  This will cause it to sag down against the coupler.  I plan to fit a piece of phosphor-bronze wire as a spring to keep the diaphragm pulled up.

Shaking Hands... Coupler

The ideal place for the couplers to be mounted is with the inside pulling face of the knuckle fingers should be even with the face of the striker or slightly proud of it.  I do this by assembling a coupler in it's box and measuring the spacing from the center of the coupler screw mounting hole to the inside face of the coupler knuckle.

I trimmed back the centersill members and filed the remains down flat with the frame.  I don't glue the box on at this point, I expect that I will need to change the ride height of the car and the coupler still.

As seen in this photo above, the inside face of the knuckle is even with the face of the striker.  Perhaps 0.005-0.010" proud of the striker, this will allow a slight gap between the diaphragms.  Some cars will be even or slightly tight.  Keeping it slightly proud will also help when attempting to uncouple a pair of cars without a stick to pull the magnetic pin to the side.

Also per LMRC standards I rotate the uncoupling pin off about 15-20 degrees further to the side.  This will allow the car to couple to engines with pilots without fouling and causing uncouplings.

Starting the Interior & Weighing the Car

I cut a section of sheet plastic for the bulkhead between the RPO apartment and the baggage sections of the car.  I measured the distance between the two side walls as far up in the body as I could with my calipers.  Then scribe transferred this measurement to the sheet styrene with the calipers.  Next I measured up to the first step where the body narrows behind the letterboard.  I roughed out the roof contour and cut the marked bulkhead from the sheet plastic.

Bulkheads placed temporarily in the interior of the car.

Weight becomes an issue now that I'm working on the interior.  I measured the width of the floor, coming up with a width of 1.125".  Weighing the car on a postal scale at 3.4 oz., the car would need to weigh about 7 to 7.25 oz.  A quick check of brass bodied cars of equal length show at least 9 oz.  This means I need to add between 3.5 and 4 oz of lead to the car.

Styrene pads for mounting the body, can't let the weights foul these.

The weight was cut to length to provide the desired weight.  I then cut the weight in half.  It is desirable to have the weight as low as possible in the car and also over the trucks.  On some of my baggage cars I have the weight concentrated down the center floor.  However this car I plan to do more interior than most baggage cars, so I'm staying with the sheet lead and keeping it away from the various body mounting screws and pads.

Weights and RTV Silicon for mounting.

I mounted the weight halves with RTV Silicon.  Note the blue lines to keep the weight from getting too close to the coupler body securing pads.

RTV Silicon used to mount the car weights.

This is what the weights look like installed.

Weights glued in and drying.

I wanted to make the interior removable for painting and detailing.  There will also be lighting to install.  Remembering that I had glued pads into the ends and mid-sides of the body shell, I need to keep those spots clear of the extra thickness of the weights and interior parts.

Interior and weights coming together. - The holes for the screws to hold the body on are visible in the 0.015" interior floor

The interior will have the various details yet to install.  The small gusset strip styrene support the bulkhead and will form the base for the letter sorting case.

The notch in the top of the bulkhead is for the lighting installation

The preparation for the lighting has started already with the notch in the top of the bulkhead, it will be installed to have some light in both sections of the car.

Almost There...

Right side in sunlight at this point in the build.

Left side in sunlight at this point in the build.
At this point, the car's nearly done.  I could finish up the couplers, put on the glosscote and install the windows in the doors and call the car done.  However, there's still the interior detailing and the lighting that I want to finish.  In my next post in the Building SP 5199 (Part 5), I will get into the interior, lighting, and working out the coupler heights.

Jason Hill

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