I occasionally receive questions asking about how the size of the drum affects spin efficiency. This is quite a technical question, and not something people are generally aware of. However, the size of the drum does make a difference due to the physics of it.
I know that in gearing, the smaller the drum pulley wheel is, the faster the revolutions of the drum, so presumably the larger the drum the faster the motor has to spin to achieve the same revolutions. I have done a little bit of research and found that the larger drums do appear to have a better spin rating compared with washing machines spinning at the same speed but with smaller drums. But there are anomalies, which means it’s not easy to make a direct correlation between the size of the drum and it is spin efficiency.
For example there is a Bosch 1400 spin washing machine with a 6kg drum which is rated B for spin efficiency, but there is also a Hotpoint 6 kg drum washing machine which spins at 1600 rpm, but despite having the same 6Kg drum, and spinning 200 rpm faster, it is also only rated the same B for spin efficiency. This shows there is more to spin efficiency than just the size of the drum and the spin speed. The design of the drum, how many holes, what size holes, the pattern of the holes and also exactly how long it spins for must also have an effect.
Within the time I spent researching washing machine stats I found that most washing machines with a 6 kg drum and 1400 spin speed were rated at B for spin efficiency, where as most washing machines with 8 or 9 kg capacity drums spinning at the same 1400 rpm were rated A for spin efficiency. I don’t see this as conclusive proof because there are several anomalies but it does tend to give credence to the idea that the larger the drum the more centrifugal force and the greater the spin efficiency.
The following chart shows some of the ratings I observed –
|MAKE||SPIN SPEED||DRUM CAPACITY||SPIN RATING|
At the end of the day the bigger drums tend to have the higher spin efficiency rating. However, there is probably less difference between A spin efficiency and B spin efficiency than most people are likely to assume. Here’s an article I wrote looking at the difference between tumble drying loads spun at different spin speeds and how much extra that is likely to cost – Washing machine spin speed efficiency figures and drying costs