I’ve just been looking through my tacho charts, and I have noticed that although I inserted one of my tachos
at 8:01, the tacho has started the trace at around 7:55.
Is there any kind of acceptable tolerance allowed ?
I have reported it to my boss, but just wanted to know for myself.
Thanks
Maybe the clock is out .
A digital tachograph can be no more than ± 20 minutes out on the UTC time, from memory it’s the same for an analogue tachograph but I could be wrong and don’t have time to look it up right now 
Having said that, it’s easy-enough to put the time right on an analogue tachograph so there’s no reason why it should be out more than a minute or 2.
Thanks fellas.
The problem is that the pear-shaped holes in the centre of the disc aren’t cut out with any great degree of accuracy. As an experiment, with the tacho head open, put 30 or 40 cards on the spindle and then flick through them. You’ll see the time on the cards leaping all over the place.
This has been a court case example.
Grab a box of new tacho discs, open the box and take the first and last one out.
Hang them on a thin ball point with the narrow bit of the pear shape.
Make sure that they are exactly lying on top of each other.
Hold them thight between two fingers so they don’t move.
Look where the 12 noon is on th front disc, and while making sure they don’t move, fold the first one slightly back, and see where the 12 noon is on the second disc, there can be easily 15 minutes difference.
We where advised 30 years ago, after this case in court where a driver got blamed not taking sufficient rest, not to cut it to fine, and make 10:20hrs, instead of sitting with the stopwatch in your hand and jumping away when the clock hits the 10 hrs.
The difference is only relevant when changing discs, so in the day it doesn’t really matter.
Very interesting indeed. The tacho chart in question is one of the last few from the box which would suggest it’s
the chart and not the machine. Thank you for the feedback everybody, a great help as always.
I had numerous so called infringements when on agency because the analysis company’s interpretation decided that the distance trace and the speedo readings entered did not tally. Very few could be calculated to be a logical misreading of numerals. The only common denominator was that these were all from high mileage tacho heads.
You do have to be very careful not to damage the lozenge when inserting the chart because this will affect the accuracy of the time trace.
I know paper discs are virtually obsolete now, but at the time you could get 2 options the Kienzel pear shaped ones and a Veeder Root one, which had a circle hole with 2 locating pin holes, 1 either side of the circle.
The latter gave a more accurate recording as the pin holes acted as locators so were a tighter fit if you will, where as the Keinzle pear shaped ones were prone to wear and tear so they tended to move about.
I am even boring myself now talking about this crap, so I’ll shut up. 
robroy:
I know paper discs are virtually obsolete now, but at the time you could get 2 options the Kienzel pear shaped ones and a Veeder Root one, which had a circle hole with 2 locating pin holes, 1 either side of the circle.
The latter gave a more accurate recording as the pin holes acted as locators so were a tighter fit if you will, where as the Keinzle pear shaped ones were prone to wear and tear so they tended to move about.I am even boring myself now talking about this crap, so I’ll shut up.
On the Kienzle ones Rob you forgot to mention the black locking tab that went over the disk, also used to wind the clock on 12 hrs if needed!
robroy:
I know paper discs are virtually obsolete now, but at the time you could get 2 options the Kienzel pear shaped ones and a Veeder Root one, which had a circle hole with 2 locating pin holes, 1 either side of the circle.
The latter gave a more accurate recording as the pin holes acted as locators so were a tighter fit if you will, where as the Keinzle pear shaped ones were prone to wear and tear so they tended to move about.I am even boring myself now talking about this crap, so I’ll shut up.
Thanks Rob
pete smith:
robroy:
I know paper discs are virtually obsolete now, but at the time you could get 2 options the Kienzel pear shaped ones and a Veeder Root one, which had a circle hole with 2 locating pin holes, 1 either side of the circle.
The latter gave a more accurate recording as the pin holes acted as locators so were a tighter fit if you will, where as the Keinzle pear shaped ones were prone to wear and tear so they tended to move about.I am even boring myself now talking about this crap, so I’ll shut up.
On the Kienzle ones Rob you forgot to mention the black locking tab that went over the disk, also used to wind the clock on 12 hrs if needed!
Allegedly 
pete smith:
robroy:
I know paper discs are virtually obsolete now, but at the time you could get 2 options the Kienzel pear shaped ones and a Veeder Root one, which had a circle hole with 2 locating pin holes, 1 either side of the circle.
The latter gave a more accurate recording as the pin holes acted as locators so were a tighter fit if you will, where as the Keinzle pear shaped ones were prone to wear and tear so they tended to move about.I am even boring myself now talking about this crap, so I’ll shut up.
On the Kienzle ones Rob you forgot to mention the black locking tab that went over the disk, also used to wind the clock on 12 hrs if needed!
Yeh, but it was the Veeder Root with the locking type bezel thingy though, not the Keinzle.
I never understood why they phased them out and favoured the Keinzle.
Who’d have thought it eh?..ME of all people a ‘‘Tachograph Anorak’’ 
robroy:
I know paper discs are virtually obsolete now
Hey, I reckon theres lots of us here that still use these. We have a 55 plate with one, which I think is about the limit in time. OK ours are only puddle jumpers and advanced puddle jumpers (brewery drays / urban artics). From what I see there are lots of 2005 and before trucks on the road, good few of these will probably have paper tachos.
We even have one (slightly advanced) puddle jumper (10t) that is still permitted to have the limiter set at 96.5. That does seem to wind up the gods when you pass them, with a drawbar trailer on as well .