An open source design for NHP chairs
** WORK IN PROGRESS **
Neuroscientific research in NHPs requires a number of very niche products, which manufacturers are able to charge exorbitant prices for. The NHP testing 'chair' is one such item. Typical NHP chair designs (McMillan, Bloomsmith & Prescott, 2017) consist of two main parts: a box structure that the animal can climb into and sit in without escaping, and a base structure that is used to elevate the box and is typically on casters to facilitate moving the chair around. The main constraints on the materials and construction of NHP chairs is that they need to be able to withstand the high temperature and pressure of regular cage wash, as well being able to safely contain an adult NHP. However, they also need to be light enough to move around fairly easily and designed with ease of use and the safety of researchers in mind. NHP chairs for use in MRI scanners places additional constraints on material choices and dimensions, which this design is not intended for.
If your lab has the money, it's always nice to buy ready-made solutions so that you can focus on research instead of engineering! Here are some commercial options for typical NHP behavioural testing chairs, which cost between $5,200 - $14,000 each:
Polycarbonate (e.g. 'Lexan') is a popular choice of panel material for constructing the box section of NHP chairs, since it is available in a clear format that allows researchers visual access to the animal once seated in the chair. Polycarbonate panels are inexpensive and can be cut to custom shapes using a water-jet cutter (although they cannot be laser cut). The downside of polycarbonate is that it becomes brittle through repeated exposures to high-temperature cage wash systems, which combined with the mechanical forces applied to it will eventually result in cracks, especially around screw holes. The use of nylon or other non-metal screws and hardware, and larger through-holes (rather than tapped holes) can ameliorate this problem.
A more durable alternative to polycarbonate is aluminium, with the obvious trade-off that you won't be able to see through it. Using a marine-grade aluminium alloy like 5052 for the side panels of the chair box will improve the chair's structural stability and chemical resistance, while vent holes cut in these panels can give some visibility and improve air flow.
Extruded aluminium 't-slot' profile is a simple and cost effective means of constructing the chair base. Many companies offering NHP chairs commercially will use t-slot, although this construction method is less durable than a welded frame, and may require re-tightening over time. A benefit of t-slot profile is that it makes it easy to attach additional components to the chair, such as guides to help position the chair in a stable and reproducible manner in the testing rig.
In addition to the t-slot hardware and locking casters needed for the base, a hinge and latches are needed for the rear door, handles for moving the chair around, corner brackets for attaching the panels to each other, and a removable waste pan.
| Vendor | Description | Quantity | Cost each ($) | Use |
|---|---|---|---|---|
| TAP plastics | Polycarbonate sheet, 3/8", 12 x 21" | 1 | $33.12 | Front panel |
| TAP plastics | Polycarbonate sheet, 3/8", 12 x 26" | 1 | $12 | Rear door |
| TAP plastics | Polycarbonate sheet, 3/8", 12 x 8" | 1 | $12 | Rear panel |
| TAP plastics | Polycarbonate sheet, 3/8", 12 x 26" | 1 | $12 | Neck plate A |
| TAP plastics | Polycarbonate sheet, 3/8", 12 x 26" | 1 | $12 | Neck plate B |
| TAP plastics | Polycarbonate sheet, 3/8", 12 x 26" | 1 | $12 | Neck plate C |
| Midwest Steel | Polycarbonate sheet, 3/8", 16 x 16" | 1 | $37.24 | Base panel |
| Midwest Steel | Polycarbonate sheet, 3/8", 11 x 26" | 2 | $48.70 | Side panels |
| Midwest Steel | Polycarbonate sheet, 3/8", 12 x 10" | 1 | $21.95 | Seat |
| McMaster-Carr | Hinge | 1 | ||
| McMaster-Carr | Latch | 2 | ||
| McMaster-Carr | Stainless Steel, 5" pull handles | 2 | $10.06 | Handles |
| McMaster-Carr | Thumb screws | 5 | ||
| McMaster-Carr | Bolts | |||
| McMaster-Carr | 5086 Aluminum 2x2" corner bracket, 11" long | 2 | $28.73 | base brackets |
| McMaster-Carr | 5086 Aluminum 1x1" corner bracket, 14" long | 2 | $18.41 | front brackets |
| McMaster-Carr | 5086 Aluminum 1x1" corner bracket, 14" long | 2 | $18.41 | top brackets |
| McMaster-Carr | 5" square stem casters | 2 | $24.25 | Wheels |
| McMaster-Carr | 5" square stem casters with brakes | 2 | $35.86 | Wheels |
| McMaster-Carr | 1/4"-20 bolts, 3/8" | 80 | $ | Fasteners |
| 8020 | 1010: t-slot profile, 14.5" | 4 | $5.29 | Frame struts |
| 8020 | 1010: t-slot profile, 16" long | 4 | $5.63 | Frame struts |
| 8020 | 1010: t-slot profile, 15.5" long | 4 | $5.51 | Frame struts |
| 8020 | 4119: 2-hole inside corner bracket | 8 | $2.90 | Fasteners |
| 8020 | 4151: 5-hole corner plate | 8 | $6.30 | Fasteners |
| 8020 | 10 series t-slot nuts | 80 | $0.21 | Fasteners |
