Actuators for Fuel and Jaw

We are using linear actuators for the 78g butane refill cylinder operator. A solenoid could work but we could not find one suitable; 10 N to 30 N over ~3 mm. The actuators are advertised at 8.8 Lbf. (~39 N). RC servos had too much stiction and so would not auto-return. Better quality servos may do better though.

Two $5 linear actuators have arrived from California; one for fuel, one for jaw action. The fuel actuator has been installed on its mounting plate (fiberglass perfboard). The cylinder guide, made earlier of copper, is installed. Pushrod (really a "U"), and its PE bushing are installed; this passes through the frame rail. Nozzle receptacle is installed with its copper tube. The nozzle receptical is a bit of PUR tubing with a washer around it. The cylinders are easy to replace and it works perfectly!

The jaw is finally installed. 0.59" 304 spring wire is used for the hinge-pin. The original plan was to use a torsion spring, to hold it closed, but we tried compression springs first. That didn't work out since it always had too much friction. We returned to the torsion idea; it worked well and does support the 100 g payload float. That spring is made of the same 0.59" spring wire.

The jaw is opened by the pull on a cable connected to the chin. The second actuator does this. Most of the cable's length is housed in the neck. The cable is 302 stainless safety-wire, as used on aircraft and motorcycles. It was slid through PTFE spaghetti for friction and that material rides over the PVC. The mouth open wide and quickly. The payload-float, with a loop of THHN wire through it, drops immediately. A loop was used last year by another team to good effect.

Ignition

The ignitor is the module from an $8 Vipertek VTS-880-1 stun-gun. It's potted so it should be OK with water but it will be sealed even better, filtered and have its own regulator. These wires will pass through the neck.

Eyes

There needs to be a power light. We want the eyes to light up so they will double for this. Signage LEDs are on order from Digikey. I think the eyes will be ping-pong balls. Hopefully they don't melt from the fire!

Journal CW35