After finishing a wash cycle, one of the drum paddles came out together with the washed clothing.
I thought that it was just worn out and that the clips had broken off because of it, and so I wanted to replace the paddle with a much stronger piece of PVC pipe. As it turns out after cleaning the heating element I had pushed the element back into the drum on top of the metal holders, instead of inside the holders where it was supposed to go. During centrifugation the clips of the paddle probably hit the heightened heating element breaking off some of the clips of the paddle. A subsequent hot wash cycle softened the drum paddles and with a few clips missing they started to come off one by one.
As a replacement PVC paddles suffer from the same problem as the plastic of the original paddles: "PVC products have the disadvantage of having a low heat distortion temperature (softening temperature) compared with other plastics of similar molecular structure (source: PVC.org)."
The PVC paddles don't come off entirely but loosen after a hot wash. After several months of washes at 70 degrees Celsius however, the PVC paddles do hold their shape and stay in place using regular PVC as shown in the pictures (the original pipe has an outer diameter of 40mm, and a 3mm wall thickness).
Alternatives to PVC
Polycarbonate has twice the heat deflection temperature of PVC (source: Professional Plastics - Thermal Properties of Plastic Materials), but will also be twice as hard to soften and bend into shape. The most common form of polycarbonate is made from bisphenol A (phenol and acetone). BPA may be released from polycarbonate into the water especially at high temperatures. Biopolymers such as poly(limonene carbonate) and polylactic acid may not be as resilient as petroleum based plastics but can be fortified.
"While it is difficult to make causal links with epidemiological studies, the growing human literature correlating environmental BPA exposure to adverse effects in humans, along with laboratory studies in many species including primates, provides increasing support that environmental BPA exposure can be harmful to humans, especially in regards to behavioral and other effects in children." -- Bisphenol A and human health: a review of the literature
C-PVC (Chlorinated PolyVinyl Chloride) can withstand temperatures up to 90-100 degrees Celsius. If you're using standard PVC, the paddles should be able to withstand up to 60 degrees Celsius, but not much higher.
Health and hygiene
"Although it had been known already earlier that washing machines accommodate bacteria and fungi in visible and non-visible biofilms that can often result in malodour of clothes inside washing machines or laundries in healthcare facilities and residential homes. Different species of the bacterial genera Acinetobacter, Bacillus, Clostridium, Corynebacterium, Escherichia, Micrococcus, Pseudomonas, and Staphylococcus have been the most frequently isolated (Robinton et al. 1968; Blaser et al. 1984; Smith et al. 1987; Perry et al. 2001; Panagea et al. 2005). In comparison, fungi have been reported less frequently and belonged to genera such as Alternaria, Aspergillus, Candida, Capronia, Cladosporium, Cryptococcus, Fusarium, Penicillium, Rhodotorula, and Trichosporum (Munk et al. 2001; Hamada 2002; Gattlen et al. 2010; Kubota et al. 2012; Stapleton et al. 2013)."
Definition and function of drum paddle
The drum paddle or drum lifter in your washing machine is a triangular prism shaped piece of plastic or metal, with holes in it or not. It fits on the inside of the drum where you place your clothes. There are typically 3 or 4 in the machine, and they are the raised attachments that can scoop up water when the drum is turning and drop the water when at the top, also they are designed to agitate the clothes while the drum is turning.
During washing, the drum rotates and the paddles help to lift the laundry slightly before its falls from the paddle, thus improving the stirring action compared to the situation if the drum was completely smooth. The drum is also usually provided with perforations in the jacket surface, so-called drainage holes, through which washing and rinsing water can pass in and out.
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Step 1: Remove Old Paddle and Cut Pvc Pipe to Length
Measure the length of the broken drum paddle and cut a piece of pvc pipe to length. Make a lengthwise incision in the PVC pipe for instance with a grinder. Keep the old drum paddle for future reference of leg/clip positions.
Step 2: Cut Holder Legs and Bend PVC Pipe Into a Drum Paddle
With a or bench saw or a grinder cut out the legs to hold the PVC pipe in place inside the wash drum.
After that heat the pipe with a hot air gun. PVC becomes very pliable when it gets hot enough.
- Bend the legs outward
- Push the two halves of the pipe inwards
- Stand on top of the pipe to flatten the bottom
- Bend the legs down so they fit inside the wash drum
- Remove the heating element of the washing machine at the back of the wash drum
- Heat one leg of the PVC paddle with hot air from inside the drum to prepare for bending it in place
- Insert a long piece of metal into the heating element opening at the back of the drum
- Push the hot and flexible leg up against the wash drum from underneath the drum with the long piece of metal
- Repeat with all legs
This turned out to be more of a hassle than I thought it'd be. But the replacements are definitely stronger than the previous paddles. They're also heavier, so replacing just one paddle would result in slightly unbalanced centrifugation.