The purpose of the II instrument itself is to hold the anaesthetised queen steady during insemination. This allows the tip of the syringe to be inserted into the sting chamber past the queen’s valve fold in order to inseminate her. The II instrument comprises a queen holder, two hooks to hold the sting chamber open and a manipulator for the syringe tip.
A chassis is needed to mount all the parts. Mine is made from 15mm acrylic sheet.
The feet for the chassis are stainless steel blocks measuring 50mm x 60mm x 10mm. These are tapped M6 on the top edge and attached to the chassis with M6 csk socket screws. The feet add weight and stability to the chassis. If you are making one of these, check and alter the spacing of these feet if necessary to suit the requirements of your microscope base.
The two 1/4-28 UNF tapped holes are for mounting the rod ends. If a suitable tap is not available these holes could simply be drilled to give clearance for the rod end studs. An M3 grub screw can be installed through the edge of the chassis to fix the studs in position. These grub screws can be seen in the photo below.
Syringe tip manipulator
Coming up with a solution for the syringe tip manipulator was a challenge. With only basic hand tools available in the workshop, constructing something from scratch was out of the question. The eventual solution is based on using half of a microscope X-Y moveable stage calliper.
A suitable stage calliper was purchased on-line and dismantled to give a single axis fine adjuster. This, when mounted onto an acrylic block to allow rotation, provides the required fine adjustment of the syringe tip position.
The fine adjuster from the microscope X-Y stage calliper is mounted on a base block of acrylic. This block is fixed on a 6mm shaft to allow the whole arrangement to rotate. A retort stand clamp attaches the rotating shaft to a vertical 6mm shaft fixed in hole ‘C’ of the chassis.
The long arm used to rotate the tip manipulator can be seen in this photo. The long arm allows the rotation to be made with the left hand, leaving the right hand free for the fine adjuster.
Fixed on top of the fine adjuster is another acrylic block which holds a 100mm long acrylic tube. The clamping arrangement for this tube can be seen in the rear view photo. The tube provides mounting and protection for a capillary tube.
The ventral and sting hooks are held in inoculating loop holders. These in turn slide in 5mm compression joints mounted in rotating ball ends.
This arrangement gives freedom of movement in all axes. The compression joints have been modified by replacing the brass olives with a rubber o-rings to give a smooth friction fit on the hook holders.
Here is an exploded view of the hook holder components:
The handle is an ‘Inoculating Loop holder’ as used in laboratories for Nichrome loops. It is 150mm long and 5mm dia.
In the centre of the photo is the 1/4 inch rod end, or ‘Rose Joint’. This has a 0.25 inch bearing diameter and an 1/4 -28UNF female mounting thread. I fitted a stud into the mounting hole with thread lock compound. A 5mm straight compression fitting was cut in half and a length of thin wall brass tube soldered to one half. This passes through the 1/4 inch bearing in the rod end. A 1/4 inch rod end bearing was used rather than 6mm to give clearance for the thin wall brass tube. The other half of the compression fitting is superglued on to the end of the tube. It cannot be soldered as this would damage the nylon bearing.
The brass olives in the compression fittings are replaced with neoprene O-rings. the O-rings are 5.5mm external x 3.5mm internal diameter. To adjust the tension in the rod end bearing, a small hole is drilled and tapped M3. This is fitted with a nylon plug and grub screw. The grub screw is visible sticking out at the 4 o’clock position on the bearing.
The bearings were sourced from http://www.hendersonbearings.co.uk Part number PHSB4.
The queen holder is simply an acrylic tube of a suitable diameter mounted to allow its angle and height to be adjusted. A tube connection for the CO2 is provided to keep the queen anaesthetised during insemination. Most commercial insemination devices allow the height of the hooks to be adjusted, however this is not possible in my design having used ball ends to hold the hooks. I arranged for the height of the queen holder to be adjustable instead by using the other half of the microscope X-Y moveable stage calliper.
The queen holder comprises several components.
The fine adjuster was salvaged from the microscope stage caliper. It is attached to the chassis with a small csk screw through the back into a tapped hole in the side of the chassis. Attached to the fine adjuster is a mounting plate that supports a pivot screw for the acrylic mounting block. The lock nut allows the angle of the queen holder to be set and fixed. The mounting block is fitted with two brass tubes, the lower one being 4mm o/d to fit the bore of the flexible tube from the CO2 cylinder. The upper tube is 5.5mm diameter and fitted with two O-rings. Grooves were sawn and filed into the side of the tube for the O-rings. This tube was made from a length of brass bar which was drilled out for most of it’s length at 3mm. The last few mm at the top are drilled to 1.5mm providing a small exit hole for the CO2. The two tubes are threaded and screwed into tapped holes in the mounting block. They could just as easily be fixed in place with epoxy. The upper tube extends 20mm from the mounting block. The queen holder is a push fit over the O-rings, providing a snug, gas tight fit. It is made from a 30mm length of thick walled acrylic tube with an o/d of 8mm and an i/d of 4 mm. This was carefully drilled out to 6mm along most of it’s length leaving a small taper at the end from 6mm down to 4mm.
The end view of the acrylic queen holder shows three small nicks filed into the 4mm end hole. These are to allow passage of CO2 round the queen’s abdomen.
To load the queen into the queen holder requires the use of an additional tube, the queen loading tube. This has an internal diameter of 6mm and an external diameter of 10mm. One end is capped with a piece of acrylic drilled in the centre with a 2mm hole.
The queen is encouraged to crawl into the loading tube. Once she is in place, the loading tube is butted up to the holding tube. The queen then crawls backwards from the loading tube into the holding tube. I never cease to be amazed whenever I see this.
The ventral hook was simply bent from a piece of 0.5mm stainless steel wire. The end being flattened and polished to avoid any damage to the queen. The shape of this hook proved to be critical, and took a few trial and error attempts to get it right. It is amazing just how long a queen can be left anaesthetised whilst trying out different hook shapes.
The sting hook is similar, but needs a 0.3mm hole in the end so that it can be threaded over the end of the queen’s sting when opening the sting chamber. Drilling such a fine hold in a stainless steel wire is not an easy task, so I took a different approach. I used a length of sterling silver wire, which is much softer than stainless steel, and the hole was made by hammering a sewing needle point through the end of the wire. The end was then cleaned up with a file and polished.