Chassis

Gearbox

Intermezzo: folding etches

Decent etches have etched fold lines of about 0,7 mm wide. You can see that on the motor mounting plate of the gearbox pictured above, yellow arrows. With very few exceptions folds are always on the inside of the fold. So if the etch lays flat on the table with the fold lines on top the etch will have to fold towards you. Press one half down with a steel ruler and carefully prise a (dulled) razor blade under the other half (be careful). If you reach the fold, line the blade up with the fold line and then fold up that half to the angle you need.

If the fold line is long and the parts narrow it may be wise to clamp one side over its length in a vise and then fold the other half over with a steel ruler.

There are specialised folding jigs, but have never felt the need for it. For the NS 7000 it is most certainly overkill.

Gearbox continued

The assembled gearbox.

The kit is supplied with an axle that has the main gear fixed on it. So there is no need to move and glue the main gear in place. I took the trouble to debur the brass gear meticulously and then polished it on a polishing spindle in my Proxxon motor tool. I also deburred the plastic gears by carefully smoothing the sides with 1200 emery paper. Likewise I polished the steel axle on which the plastic idler runs. This all reduces friction but take care not to overdo things.

The gearbox is simply bolted together, no need for soldering. The bolts are secured with thread lock. There is one snag: as the drive axle is provided with the gear fixed in place this axle MUST be inserted before final assembly. There is no way to get it in place after assembly. So don't forget.

The gearbox is lifted from below with the axle boxes slid on the axles and then clicked into the frames.

Frame construction

Maybe it is good idea to read about the chassis construction of my AD60. Admittedly that is a far bigger locomotive but in essence the techniques apply to the NS 7000 as well. The NS 7000 frame plates are made from etched brass so you can solder them together easily. Although DJH claim the chassis can be glued I would advise strongly against that. Learn how to solder is my motto, it is the only gateway to successfully building etched metal kits. It is not half as difficult as beginners tend to think and most people are remarkably quick to learn which end is the business end of the soldering iron.

I have no photos of the actual construction of the chassis so I will use the DJH drawings which I have simplified for this purpose.

The chassis plates (blue) are removed from the etches. These and the sheet metal frame stretchers (yellow) are deburred and decusped with a file and then placed between the frame plates. The whole frame is then screwed together with the solid brass frame spacers (red) and their screws (red). Turn the frameset upside down on a firm flat underground, e.g. a sheet of glass or mirror, with the frame spacer screws at one side a bit slack. Press vertically on the frameset so both frame plates line up and then tighten the screws. If the green tabs on the rear of the frame plates prevent the frame plates getting flush on the glass let them hang over the edge of the flat surface.

Finally solder the frame plates to the frame stretchers.

Soldering the frame must be done in stages. Prevent the build up of heat in the frame which will cause it to warp. First tack solder the tabs (red arrows) and let cool after each tack. Then fill in the seams between and outside the tacks one by one, letting cool after each seam. Check at intervals if the frameset still lies flat on the glass. Finally solder the brass screws so they will never come loose.

Move the axle boxes on the axles, install the wheels and place both axles on their respective places in the chassis. Put the chassis on its wheels on the glass surface. Check if the wheels all touch the glass. Move the axle bearings if necessary. Once all for wheels touch the glass, solder the axle bearings to the frame plates.

Using a frame building jig

With the knowledge of hindsight I could better have built the chassis in a chassis jig like the one from Poppy's Woodtech. You can build the loco to exact dimensions with minimal play.

More on this jig on my NS 5000 project site.

On the same project you can also find an example how to assemble a loco frame in this jig.

Recommended for every builder but certainly for the beginner.

Image from Poppy's Woodtech website

Completing the chassis

The manual gives good directions how to complete the chassis so I won't repeat them here. Suffice to say I glued the white metal cylinders because I was scared to solder them. I later learned how to solder white metal and believe me it is not difficult if you control the temperature of your soldering iron.

The completed chassis.

The bogie spring seems to lift the front driver off the rails. And in fact it does. But the superstructure is hefty and will correct that once it is seated on the frames.

At this stage the chassis should be tested thoroughly. Free running is paramount. Do not be tempted to think a drop of oil will solve any problems that exist. Also forget about bedtime stories about "running in". For small models like these they are fairy tales. Everything, motor, gearbox, wheels, coupling rods should work smoothly and without even the slightest form of binding.

The leading bogie is attached to the front on this bolt.

The bogie is pressed down on the rails with a spring. Some fiddling and adjustment is needed to get the right stiffness. The spring really serves a purpose: it shifts the balance of the loco from the front towards the drivers. The bogie is secured with a single nut, which on "its turn" (excuse the pun) is prevented from working loose by a drop of glue or thread locker.

Electrickery

These are the original wipers supplied with the kit.

The wipers were difficult to get and to hold in place during the whole assembly process. Personally I think running it on the tread surface is not a good idea. Dirt will get the better of them. Later I learned how to make your own wipers touching the inside of the wheel rims (see project AD60). This would have been a better solution.

Motion gear

The Walschaerts valve gear

The valve gear comes part riveted. That is both good and bad.

The good thing is that for beginners the valve gear is one of the most daunting parts of a build and it saves them the difficulty of assembling the valve gear. I later learned to solder the valve gear but that is certainly not for beginners. Might you want to read about it I wille refer you the construction of the NS 5000 motion gear.

The bad part is threefold:

• Before building it is extremely difficult to remove the etching cusps from the rods
• After building the rivets are very loose so the parts wobble all over the place.
• During building you must install the whole valve gear as one complete assembly and you have very limited options of testing the individual joints for free and trouble free running. Every single moving joint is a source of trouble and if you have to assemble the valve gear yourself you can build it up step by step, checking trouble free working after every step.

.Why this model is considered to be the beginner's model for Dutch modellers is beyond me. The NS 5500 has no valve gear at all and is consequently much easier to build. Moreover, NS 7000's valve gear has a nasty design flaw which could deter beginners forever. It almost did for me. My locomotive ran absolutely sweet without the valve gear. As soon as I installed the valve gear trouble started. And in my case it faltered every revolution. Sometimes seriously, sometimes only slightly. It took me a long time to figure out the cause. I must admit having been close to giving up.

Long story short: the top end of the radius rod bumped into the bracket arm (red arrow) which caused binding.

Click the image to enlarge
The Dutch text reads: Make a slot of 1.5 mm at the ends with a slitting disk or a file.

After I snipped off the top end of the radius rod the whole engine came to life and ran without binding. It took me several weeks and a lot of frustration to figure this stupid thing out.

In hindsight it is described in the manual but it mentions the solution without mentioning the problem so I was totally mystified about the purpose of the remarks there until had discovered what the problem was. Moreover the solution the manual mentions is bad advise.

• First you should file a slot from the top instead of the bottom, because the radius rod touches on the top as the photo clearly shows.
• Second I would strongly advise against making a slot at all as it weakens the already feeble motion bracket.
• And third you should definitely not make a slot with a slitting disk. The fast truning slitting disk (5000+ rpm) because it is likely to grab and mangle the motion bracket.

Snipping off the top end of the radius rod is really the better and easier solution.

A shot of the detailing of the chassis complete.

The position of the brake hangers need a lot of attention. Not only should they not touch the wheels, but they should also allow the wheels to pass while mounting them on the axles.

A view on the wheel bearings.