Since my rocket activities in the summer are low – I get distracted due to the other fun stuff – it turns out I do a lot of the APCP mixing in the winter My workshop for mixing doesn’t have permanent heating, is poorly isolated anyway and temperatures regularly drop to 5-10°C. At these temperature the HTPB and thus the propellant mix get really vicous.
So to be able to consistently mix and pour at these lower temperatures I added bowl heating to the 10L bowl of my Hobart A200. This consists out of a 180W – 6m long silicone heating wire which includes a 1m long “cold” wire integrated to both ends. I used a 4-pin Neutrik XLR connecter (for the heating wire and temperature sensor) in combination with a STC-1000 temperature controller / thermostat mounted into a Hammond Electronics 1554PGY universal housing.
The 180W easily and quickly warms a 6kg batch of propellant to 25-30°C (pending on the set point) with little overshoot.