Of axes and axles

, my translation of my German article.


A few days ago, on 24 December 2009, I was quietly reading a Portuguese book about air conditioning. I had bought that book on 24 May 2004 from a bookstall at the north side of the “Praça do Comércio” in Lisbon, Portugal’s capital.

I sometimes read such books, on the one hand to practice the Portuguese language, which despite my interest that dates from approximately 1976 (I don’t exactly remember) I still don’t sufficiently master; on the other hand because a better understanding of the physical and technical principles of cooling technology is always useful for me: every now and again I translate manuals and similar texts on this subject, from English into Dutch, my native tongue.

The book

The 1977 Portuguese book is a translation of an American original from 1972, which in turn is a revision of an American book dating from 1948/1951/1955. Google Books knows these books, although the texts haven’t been digitised and republished yet, perhaps because nobody took the trouble to do it, or because the copyright holder did not grant permission.

The bibliographical data are:

So the books aren’t very modern and therefore cannot describe very modern technologies. However, the basic principles of useful inventions usually don’t change that much over time, so the Portuguese book remains useful and interesting for me.

The axis of an axle?

Text fragment

While reading (I usually don’t read such books from start to finish, but instead start at random pages), on page 67 my eyes fell on this sentence:

O que é um compressor de rotação?

O modelo típico consiste numa caixa cilíndrica que contém um veio cujo eixo excêntrico em relação ao do cilindro; o eixo é ligado a um rotor com estrias radiais nas quais existem lâminas deslizantes apertadas contra as paredes exteriores por inércia ou utilizando molas.


The words “veio” and “eixo” weren‘t entirely unknown to me, although I wasn’t certain of their exact meaning either.

While reading, I had the Portuguese-German Langenscheidt dictionary handy, because it is light (350 grams), small (15.5 x 10.5 x 3 cm) but nevertheless rather comprehensive (“rund 45,000 Stichwörter und Wendungen”). In that dictionary I found, among other things:
eixo = Achse; (TECN) Welle;
veio = (TECN) Welle.

So the compressor has an axle, a shaft (as a technical device), the axis of which (as a mathematical notion, the centre line) is eccentric.

Point of doubt

But then in the next sentence I’d have expected the word “veio” again, rather than “eixo”, yet there is this: “o eixo é ligado a um rotor [...]”. So it seems the meanings of these words (similar to English shaft, axle versus axis) are less clearly separated in Portuguese. That assumption is supported by the monolingual Porto Editora dictionary, which can also be consulted online under Infopedia.pt:

eixo =
peça cilíndrica em torno da qual um corpo (ou um sistema de corpos) pode ter um movimento giratório, chamado movimento de rotação
but also:
MATEMÁTICA: eixo de revolução: recta fixa em torno da qual uma linha ou um domínio plano, numa rotação completa, geram, respectivamente, uma superfície ou um sólido (de revolução);

veio =
6. peça destinada a transmitir movimentos
7. (figurado) fundamento; eixo; ponto principal


It‘s interesting that the expression “um veio cujo eixo” could be translated into Dutch as een as waarvan de as, so with the same word “as” used twice. This notable fact was the reason I wanted to write this article. I started writing it in German, because I first found German translations of the puzzling Portuguese words, and because German has the word “Welle”, that doesn‘t have a direct cognate in Dutch.

Note regarding spelling error

Until 14 July 2013, I had “excentrical” here. That’s wrong, the correct English word and spelling is ‘eccentric’, or as recognised by some dictionaries, also ‘eccentrical’.

I noticed the error while preparing this new article, which has the word in its title.

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