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Nepenthes Display Modules
Overview and Selection

Nepenthes Display Modules are storage boxes with windows. The modules are strong, stack and latch together, can have wheels, and are very flexible in size and other configuration. The modules are sold as comprehensive kits comprising laser-cut Baltic birch plywood, acrylic windows, nickle-plated steel hardware and stainless steel fasteners. These kits can be assembled into high-quality modules for storing, displaying, and transporting treasured or otherwise valuable items. The system was developed from a desire to house miniature and model railway rolling stock.

The objective, on this Overview and Selection page, is to describe what is required to design a module stack, and obtain and build the necessary kits, with enough detail to give understanding and comprehension to a prospective purchaser.

Technical information and support are available on request before and after purchase. An order will be reviewed on receipt, and no manufacturing will be started without consultation and agreement about purchase price; so these pages simply provide a starting point. The best procedure for interested parties is to make early contact by email. The email address is here.

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The Nepenthes Display Module System is very flexible and permits specification of modules well-fitted to a specific task; however, this does mean that a purchaser must make a significant number of decisions. This section describes what is available and what decisions are required.
  • Basic Requirements
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    Actually, there is no required component. However, some things are naturally part of a module stack, so that, if they are not chosen, a better course might be acquisition of another storage system somewhere between a beautiful breakfront and Dexion shelving, according to circumstances. Given these observations about needing a stack of modules, a few assumptions are made in what follows.

  • Structure
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    Every module is built on a crate; one of which is shown in the image below. The sides of a module are glued together and to the crate, which creates a lightweight, strong, and stiff, box. The bottom of the crate forms a standard square plug, which engages with the square socket on the module underneath. These two modules then are held together by over-centre latches. The sides of the module, and the top, which is glued to the sides, form the socket on the top of the module. A Base and a Lid, both described below, are special in that they are terminal, i.e., they do not have a plug or socket, respectively, and thus do not support further stacking.

  • Base
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    A Base is needed. There is just one design of Base, and all, and any, modules fit on it. A Base is a nominally 2 feet square platform with the standard Nepenthes Display Module (NDM) socket on its top, together with the associated clamping latches. A base has no storage space, is terminal, and is a particularly strong and stiff module by virtue of having both a top and a bottom which are glued to its crate.

    Internally, a Base has four wood pads into which lagbolts, etc., are screwed, to mount wheels, legs, or something else, on the bottom. These pads are shown in the image above prior to installation; they are supporting the crate for the photograph, but ultimately will be installed in the corner open squares of the crate. So, even with a Base, there are design decisions: wheels, legs, or something else; small or large wheels; etc. The image at the beginning of these pages shows a Base fitted with 8 inch diameter wheels from Harbor Freight. The stack behaves rather like a grocery-shop cart; but there are handles to grab on every module.

    Design Recommendation: for smooth movement over relatively large distances or bumpy surfaces, large (8 inches diameter and up), pneumatic, wheels are best; if in doubt, choose a larger diameter over a smaller diameter. Fitted with large wheels, a Base becomes heavy because of the steel parts; however, with large wheels, a Base will roll easily.

  • Modules
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    The basic display, or storage, unit is the module. There are a considerable number of design decisions to be made; but a good starting point is the size of the module.

    Modules are specified by their internal size, in other words, their actual storage size. The length and height are user-specified, within limits; and the width is user-chosen from just two possibilities called fullwidth and halfwidth. A fullwidth module is nominally two feet wide, with an actual size of 22.85 inches; a halfwidth module is nominally one foot wide, with an actual size of 10.87 inches. Two halfwidth modules stack in the space taken by one fullwidth module; they do not need to be the same length or height, but differing heights prevent stacking a fullwidth module on top.

    The height can be anything from zero to 15.83 inches; a module with the maximum internal height is 18 inches high externally. This maximum is dictated by the laser cutting equipment used to produce the module plywood pieces.

    The length can be anything from 22.85 inches to about 61 inches. This upper limit is dictated by the laser equipment, but 61 inches is very large.

    • Size
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      Clearly, the storage dimensions must be large enough simply to fit whatever thing is to be stored. However, also it must be possible to load the thing, and that without knocking off pieces, too. Thus, the two other dimensions that matter are the window height, and, with a halfwidth module, the end window width. The window height will be 1.34 inches less than the storage height, and the halfwidth end window width is 9 inches.

      Also to be considered are module total weight and maneuverability. And one effect of these on design is the choice of a fullwidth or halfwidth module.

      Fullwidth modules have their handles on their sides, halfwidth modules have their handles on their ends. Fullwidth and halfwidth modules will fit through standard household 30 inch doorways either being carried or on wheels. Common sense limits apply: carrying a heavily-laden fullwidth module by the handles, through a doorway with a spring-loaded door, with stairs going down the other side, is going to be a tricky operation.

      Design Recommendation: Halfwidth modules were a design afterthought, but they are proving to be excellent in use. Halfwidth modules lose some floor space; in particular, it is no longer possible to put something in the "middle" of the (fullwidth) module. Furthermore, in practice, they need to be bought in height-pairs, or any height difference resolved, to enable stacking a fullwidth module on top of them. Also, two halfwidth modules cost more than one fullwidth module because of the increased parts count and greater assembly effort. But, halfwidth modules are considerably easier to maneuver, and they are lighter individually. So, considering all the pros and cons, if there is something heavy to display, then a halfwidth module is well worth considering. If there are two heavy things to display, then it is a no-brainer.

      Module length also must accommodate the thing(s) being stored and displayed. However, length also has an effect on module design and the associated parts count and construction details. The shortest length permissible is 22.85, which is the same as the width of a fullwidth module. This size of module is known as as a Main module; as already indicated, if fullwidth, it is square in plan. A Main module has the smallest parts count, is the easiest to build, and has the lowest cost per unit floor area. A Main module weighs about 18 lbs; a halfwidth Main weighs about 9 lbs; the weight of a module depends on its height.

      Design Recommendation: If it is possible to fit what is to be stored into a Main, then this is the module to choose. A fullwidth Main is the simplest, cheapest, module, with no restriction on its use. Two examples are in the image at the beginning of these pages: the module at the bottom, containing the blue train, and the second from the top, containing the green train.

      If the thing to be stored is too long for a Main module, then a Long module will be necessary; selection of a Long module is automatic simply by specifying a storage length greater than 22.85 inches. A Long module extends its sides beyond its bottom interface plug, and has horizontal platforms on its top that extend from its top interface socket to its ends. An example is in the image at the beginning of these pages: the module second from the bottom, containing the brown and cream train coaches. Above that module is another Long, halfwidth, module, containing a locomotive with an arrow on its side, which is alongside a Main halfwidth module of the same height.

      There is a variation of a Long module which is called Extended. An Extended module is long enough to exceed the capability of the laser cutter to produce parts in one piece. Thus, an Extended module is longer than 30.50 inches, and has some built-up components. The immediately obvious differences between Long and Extended modules are increased cost and construction time, due to the greater number of parts. However, also, Extended fullwidth modules can store a lot of items and quickly can become heavy and difficult to handle in use. Items long enough to require an Extended module probably are better housed in a halfwidth module, unless the items are light in weight.

    • Openings
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      For any module the specification can be for zero to four windows, one to a side; each window is of standard size that cannot be altered. Also, the top can be closed or open. An open top reduces considerably the stiffness, strength, and ruggedness of a module, and, so, must be specified with care.

    • Floor
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      The module bottom is largely open since it is the structural crate, but normally a floor is mounted immediately on top of the crate. Floors are in two pieces so that they can pass through at least one module opening, and are screwed to the crate. The floor is intended to include the user-created attachments for the stored item(s) - all of the train parts in the stack image are held down to their module floors. The floor is not structural, and is removable. This arrangement permits changing the floor, which enables use of a module for multiple duty or changed requirements. One plywood floor is supplied as part of a module.

  • Stack Configuration
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    A stack of fullwidth modules is a simple and obvious concept. Any fullwidth module stacks on top of any other fullwidth module; height is not relevant; length has no significance (for stacking); and all the handles and latches are on the sides of the modules. This was the original concept, and the only non-extraordinary thing that can go wrong is the omission of latching the modules properly, i.e., operator error. The introduction of halfwidth modules makes possible two other types of stack configuration; and these configurations have both positive features and restrictions, including extending the possibility of operator error.

    • Halfwidth Stacks It is possible to put two stacks of halfwidth modules onto one Base module, and the two stacks can be independent with respect to the lengths and heights of component modules, as with fullwidth stacks. However, each of the stacks is latched with just two latches per module on the outer side of the stack, and this makes it possible for the stacks to tip over the side edge of a module; one tipping to the left, the other to the right. There are two ways of dealing with this problem. One way is to have both stacks (not necessarily each component module) the same height, and then latch a fullwidth module across the tops of the stacks. This approach prevents tipping of a sensibly high stack. This type of double stack configuration is potentially very useful for storing heavy items; but it does require the discipline of using a bridging top module for safety.

      The second way to secure a stack of halfwidth modules is to put latches on the ends of the modules, and this mechanism is provided if specified. End mounted latches can be seen in the image at the beginning of these pages, on the Base and a couple of modules at the top of the stack. If every halfwidth module has latches top and bottom, then each stack is completely independent and protected from tipping. However, a limitation is that all except the top module are restricted to being Main modules because there is nowhere to put an end latch on the top of a Long or Extended module. It is possible to put end latches on the bottom of Long and Extended modules.

    • Mixed Width Stacks A stack of mixed width modules is quite possible, as is clear from the image. The potential usefulness depends on what is needed in any particular case. The difficulty with a mixed stack is simply that it must be designed carefully since some modules cannot be put on top of others and so the assembly order may matter in use.

    Design Recommendation: Avoid end-mounted latches except where it is clear that they are the solution. For example, the halfwidth module at the top of the stack in the image at the beginning of these pages is end-latched to a bridging fullwidth Main module because, since it has a Lid, it cannot have another module on its top.

    The important thing to absorb from this section on stack configuration is that specific requirements can be met because of the flexibility of the system. In practice, the restrictions are not serious difficulties, provided that care is taken in design.

  • Lids
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    A Lid is not a module, but fits to a module, normally an open top module. The module at the top of the stack image, and shown below, is a halfwidth Main with no window, an open top, and a Lid; it is used as a toolbox.

    A Lid is terminal in the same way as a Base is terminal, although there is no equivalent of wheels with a Lid. A Lid on a module prevents further stacking onto the module. Lids are available in both halfwidth and fullwidth configurations. Halfwidth Lids are screwed to the module, as shown. The lids in a fullwidth configuration are identical to halfwidth lids, but there are two of them screwed to a cross-member. Fullwidth Lid configurations are detachable as well as openable to enable easy access to large objects; the left image shows a fullwidth Lid configuration detached from its module.

    It is sensible to identify a module as one that is to be fitted with a Lid, since such a module does not need top latches, and will be provided with a socket configuration that is better suited to a Lid than a standard socket.

  • Materials
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    The modules are constructed of 3mm (1/8 inch) and 6mm Baltic Birch plywood. Structural members such as the crate are the thicker material. Either material can be specified for the box sides; however, the thinner material normally is adequately strong and is lighter. Windows normally are 3/16 inch Acrylic, but can be something else, such as plywood, in which case they become access panels rather than windows.
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Construction instructions are on this website. What is below is a small subset of the construction instructions, to indicate various facets of the process, including tools and level of construction skill required.

This image shows the kind of tools required.

These images show something that typifies the most complicated procedure required. There are four corners, and each corner is assembled as shown in the first image. The tools comprise four long bar clamps, ten spring clamps, and four assembly squares. Note the old desk top being used as a flat assembly surface; the shiny stuff is waxed paper, used to keep off glue from the surface. The green tape prevents glueing the straight-edge clamping wood to the job.

A complete corner pillar, this is two layers of plywood in addition to the outer skin. Once the top is glued in place the structure becomes quite sturdy.

Detail of corner joint structure, and handle and latch attachment.

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A stack of Nepenthes Display Modules costs hundreds of dollars, and requires time, effort, and some wood-working skills and tools. An approximate price guide is below; since the system is flexible, so is the price. Advice about reducing costs will be given if cost reduction is possible. An agreement about purchase price will be established prior to any manufacturing.

If help is needed, it will be necessary to have some sort of inventory of what is to be stored. Quantities, sizes, and weights, are rather obvious. But, also, it will help to have some idea of the style and size of module(s) envisaged, including any preference about the importance of displaying any particular item.

If you would like to make enquiries of any kind, please use the Contact Information.

Price Guide
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The approximate prices below are for module kits, not including glue, wheels, or shipping. Otherwise, the kits are comprehensive, and comprise all plywood parts for the main case, plywood floor, hardware, and acrylic windows, as applicable. The current shipping estimate is $25, and this may cover more than one module when they are shipped together.
  • If wheels are desired, then a Base is necessary.
  • The sizes for Main, Long and Extended modules are actual storage sizes, i.e., internal sizes.
  • The sizes for Base and Lid are nominal, neither has any storage space.
Width [inch]
user chosen
Length [inch]
user specified
Height [inch]
user specified
Cost [$]
Base fullwidth2424-190
Main fullwidth22.8522.85< 15.83330
halfwidth10.86522.85< 15.83290
Long fullwidth22.8522.86-30.50< 15.83420
halfwidth10.86522.86-30.50< 15.83350
Extendedfullwidth22.8530.51-61.00< 15.83490
halfwidth10.86530.51-61.00< 15.83410
Lid fullwidth2424-200
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last-modification-date:  7 Sep 2013