[tamar.nelwan]

Entry made and paid for the whole weekend

 

[tamar.nelwan]

I would second that proposal

Blast, Matt posted just as I hit enter...so I would support Tom's proposal an if I may add lib.

Don't keep us in suspense Matt, keep us in the dark

With kind regards

Tamar

 

[tamar.nelwan]

On behalf of the Belgium and Dutch racers, great track, atmosphere and races make it a pleasure to come over and take part in this event each year. So our thanks to the Rockingham crew for their time and effort to keep organizing.

As no results have been posted yet, let me share an image of a certain Belgian beauty...so guess who won concourse

with kind regards
Tamar

 

[tamar.nelwan]

Rockingham (finish line lap detection) was especially tricky for two main reasons
1 - weak detection magnets
2 - high speed at the end of the straight
The combination of these two factors led to lap counting issue.

If I may add my 2cts:
Besides the two main reasons that Maurizio mentioned, both of whom apply to the strength and placement of the magnets under the track....
There was i.m.o. a 3rd factor which influenced the number off missed laps in some of the cars..and that was the position of the Hall sensor in the car
From my personal observation I noticed that the cars most affected by the weak detection magnets were also those who had a relative high ground clearance and/or a relative thick chassis.
(as in cars with a NSR chassis/motorpod and/or 3DP chassis )

So in addition to the standing guidelines for Hall sensor placement on chassis:

1. Mount on chassis with beveled side facing down

2. Mount on chassis with min 20mm distance to centerline chassis

I would suggest to add:

3. Mount on chassis with max 1,5 mm groundclerance.

Now before you all start hollering " But we didn't run that much ground clearance "...picture this:
Even when you run your car/chassis at 0,8 mm GC, the hall sensor is placed on top of your chassis.

So add the thickness of your chassis (like 0,75mm for most 3DP chassis and 1mm for NSR chassis) and your already at or above 1,5 mm.
Add to that the height of the bit of shrink-wrap, blue tack or hot glue you used to mount the hall sensor and you can easily get your sensor at 2 mm above the track.

A hall sensor is a simple device which sends a pulse to the O2 chip when triggered by a magnetic field. (produced by the track magnets)
The strength of a magnetic field diminishes exponentionally (as in twice the distance is not equal to half the strength) meaning that a few tenths of a mm can make all the difference between counting a lap or not.

So if you run a 3DP/NSR chassis my advice would be to cut or mill a recess in your chassis to place the Hall sensor lower.
DiSCA Tech Rules allow for such a modification.

With kind regards
Tamar

 

[tamar.nelwan]

What can I add to that..other then better safe than sorry

 

[tamar.nelwan]

Specifying a magnet is all well and good, but would it make life a little easier if the strength of the field at a calibrated height be specified instead?

I don't think so, as the proliferation of magnetic field measuring tools amongst slotracers is pretty low

On a more serious note: No need Greg, in 99% of the cases just using the advised magnets will do. As it most likely would have done on the Rock Bull Ring.
But the combination of weak magnets, long straights and high speeds just compounded the issue.

I agree with all above, given that Maurizio has suggested we use the CN11, as the optimum magnet to use, wouldn't this be tested by the engineers on a STD slot it car, and be deemed as capable of its task. The Slot it could confirm the strength of this magnet, I presume it is an N52 neodymium grade magnet.
As a note I see in the catalogue the magnet part number is cn01, or is there a new magnet CN11?

I think its a typo Dave, CN 01 should be ok, in its own documentation (the PDF I linked to in your own topic) they use both the CN 0(1)1 and the CN 02 in the illustration.

Is it possible to have too strong a magnetic field?

Large, super powerful neo magnets are available on eBay for pennies, I use dozens of them in my studio, and would prefer to re-purpose some of those rather than buying more of the fragile and brittle CN11/CN01.

As a matter of fact...yes you can. In order to avoid any lap counting issues we used strong(er) magnets for the Suzuka track. No lap counting issues, but if you pass the finish line too slow...you do notice your car being slowed down even more by the magnets under the track.

Stronger magnets could stop a car dead in its track

with kind regards
Tamar