[R] produce hours greater than 23

[herodote@oreka.com]

Hy all,

I wish to use the date function to draw againt the lifetime of a motor.

This lifetime is given to me in Hours (it can go over 5000 hours)

I'm unable to find how to convert this lifetime value to something like %H:%M:%S because when R see 24H it says 1 day, i don't want that, i just want %H:%M:%S with a value of %H higher than 24...
for example: 
i've got this value in hours: 345.05 H

I wish that R gives me : "345:3:0" or "345:03:00"

What R function could do it?

I've search for as.Date strptime... but none of these seems to be able to put a value for %H greater than 23.

i've browse the help and docs and found nothing (am i blind?).

thks all
guillaume.