not supported in the form given. bilingual dictionaries are not suitable for entries in LEO, since any errors there cannot be checked. LEO requests dictionary entries for both languages.
I agree with Stefan that this would be a useful entry, but I think that this is probably more BE than AE


http://idioms.thefreedictionary.com/at+a+rate...:

at a rate of knots (British & Australian)
if someone does something at a rate of knots, they do it very quickly. She did her homework at a rate of knots so that she could go out with her friends.

UK:
"at a rate of knots (colloq) - very fast " http://www.chambersharrap.co.uk/chambers/chre...

It's probably used in other places, like Australia, but you can just choose one country from the list.

Im Deutschen gibt es den tollen Ausdruck "ratzfatz".
Sie machte ratzfatz ihre Hausaufgaben damit sie mit ihren Freunden weg konnte.
Evtl. passt das ja.

ratz|fatz <Adv.> [zu mdal. ratz = schnell, rasch (wohl lautm. nach dem Geräusch schnell reißenden Stoffs od. Papiers) u. fatzen = zerfetzen, zerreißen] (ugs.):
sehr schnell:
Was sie in den vergangenen Jahren versäumt hat, das holt sie jetzt r. nach: Die Kirche sucht den Zeitgeist, oder hechelt sie ihm nur hinterher? (Tagesspiegel 25. 4. 99, 10).
[Quelle: Duden: Das große Wörterbuch der deutschen Sprache in 10 Bänden.]

Providing dictionary evidence to DH's suggestion.

As pubs disappear at a rate of knots, Last Orders celebrates the publican and what we are in danger of losing.

In any case, don't forget the [Brit.] [ugs.]

British informal Very fast.

I agree with Hecuba (#8).

Macquarie Dictionary, 3rd ed.:

The Aussie perspective.