forceX assembly instructions

(3D-printed v.1)

I. Resources and further reading

The forceX setup is a reproducible advancement of the design introduced by Herrel et al. (1999) and was published in the following article:

Rühr, PT & Blanke, A (2022): forceX and forceR: a mobile setup and R package to measure and analyze a wide range of animal closing forces.

The ‘forceR’ package for closing force analyses (written in the programming environment R (R Core Team, 2021)) is available at CRAN.

A video of the assembly instructions is available on Youtube:
https://youtu.be/xabIewPMVuU

II. Parts lists for forceX measurement unit

Table 1: 3D-printed components. All components should be printed in PLA filament, since this material is less flexible than other common materials like ABS, ASA or PETG.

Table 2: Generic components.

The 12 mm diameter rod should be cut into the following pieces:

• main rod: 90 mm
• microscope rod: 100 mm
• camera module rods: depending on focal range of camera. We used two 100 mm rods for a 5-MP RPi Camera (B) rev. 2.0 with adjustable focus (Waveshare, Shenzhen, China).

Table 3: Off-the-shelf and custom components.

III. Parts list for power source

Table 4: Parts lists for power source.

IV. Parts list for charge amplifier

For the parts list of the analog charge amplifier see IX. Schematics of custom electronics: Charge amplifier. For help in building this device, please contact M. Dübbert (Scientific Electronics & Experimental Design, Group of Prof. Büschges, University of Cologne).

V. Additional parts

Table 6: Additional parts list.

VI. Assembly instructions

The following pages will guide you through the assembly of the forceX measurement system. At the end of this document you will find overview drawings of the whole setup and photos of additional components such as the custom charge amplifier and power source.

Step 1

Screw the M3 bolt into the main body. The bolt will act as the fulcrum for the lever.

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Step 2

Insert the M1 hex nuts into the recesses on the lower side of the bottom tip element holder using a soldering iron. Then, use the M1 bolts to fasten the tip element to the bottom tip element holder. Make sure to hand-tighten the bolts so that the tip element does not bend.

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Step 3

Insert the M3 hex nuts to the main body and tighten the bottom tip element holder to using the M3 bolts.

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Step 4

Insert the Kistler 9215A force transducer into the hexagonal hole in the main body. Use the M3 bolts and M3 hex nuts to secure the force transducer in place. Insert the M2 threaded rod into the force transducer. Attach the Kistler 1651C1 cable to the force transducer.

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Step 5

Screw the M3 bolts into the lever. These add stability to the lever and prevent bending. Attach the second tip element using the M1 bolts and hex nuts as described in Step 2. Place the lever on the main body and secure the M2 hex nut on the M2 threaded rod in the force transducer. The position of this nut on the rod defines the rotation of the lever and thus the gape distance at the tip elements.

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Step 6

Insert the main rod (e.g., a 90 mm piece of a hollow, aluminum rod with a dimater of 12 mm), into the base plate and attach the main body on its upper side.

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Step 7

Use the M3 bolt and hex nut to secure the main body on the main rod.

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Step 8

Insert the head of the M5 bolt into the 3D-printed M5 knob using a soldering iron. Use the M5 bolt assembly and the M5 hex nut to secure the main rod on the base plate.

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Step 9

Attach the microscope rod (e.g., a 100 mm piece of a hollow, aluminum rod with a dimater of 12 mm) to the microscope flange. Use the M5 bolts, washers and wing nuts to attach the microscope flange to the base plate.

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Step 10

Attach the M5 knob to the M5 bolt as described in Step 8. Attach the microscope slider to the main rod and use the M5 bolt assembly to secure the slider in place.

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Step 11

Take a short, one-stranded piece of electrical wire and wind it around the base plate battery holder outer holes so that the poles of the batteries will be connected.

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Step 12

Take a two-cored piece of cable and wind one strand each around the base plate battery holder inner holes at the 'plus' and 'minus' signs, respectively.

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Step 13

Screw the microscope (we used a Bresser Junior Stereo 3D) to the microscope slider. Make sure that the microscope cable slides through the big hole of the slider. Use the M2 bolts and washers of the microscope to fasten it on the slider. Connect the two strands of the cable of Step 12 to the microscope cable s, observing polarity.

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Step 14

Slide the two AA batteries into the base plate battery holders, observing polarity as indicated by the 'plus' and 'minus' signs on the base plate. Once the batteries are in place, the microscope LED should automatically switch on.

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Camera module

Note that the above description does not yet show the camera module. However, we think that the following figure should help in setting it up. Python code to run the camera on Raspbian is available on Zenodo: .

VII. Schematics of forceX measurement unit

Overview

Exploded view and component names

Projected views (all directions)

VIII. Schematics of tip elements and exemplary edge shapes

IX. Additional diagrams and photos

Charge amplifier for piezo-electric force transducer

The plus pole thread of the 2-threaded wire coming from the BNC output of the amplifier is attached to the LabJack with the screw at AIN0, and the negative pole wire at the GND screw. Make sure the wires don't touch each other to prevent a short circuit.

Power source

Full setup

References

• Herrel, A., Spithoven, L., van Damme, R., & de Vree, F. (1999). Sexual dimorphism of head size in Gallotia galloti: Testing the niche divergence hypothesis by functional analyses. Functional Ecology, 13(3), 289–297. https://doi.org/10.1046/j.1365-2435.1999.00305.x
• R Core Team. (2021). R: A language and environment for statistical computing. R Foundation for Statistical Computing. R Foundation for Statistical Computing. http://www.R-project.org

Prusa

i3 MK3 MMU 2

No

No

300 um or smaller

20

Print settings can be changed according to personal taste. The lever should be printed at 100% infill, and the main body with at least 3 top and bottom layers and also at higher infill settings (>= 35%) to provide decent stability.

Using PLA is advisable because it is less pliable than ABS, ASA or PETG.

We used no supports or rafts except for the hinges of the rod cam connector.