Cabling a BMX track for transponders

Timing positions.

In general the Transponder system uses 3 timing positions around the track for racing and 4 or more for training.

• Gate drop.
• Bottom of the Start Hill or 30' (whatever suits)
• Intermediate loops (at the very least a loop at the entry to the first corner is highly recommended)
• Finish line.

The Gate Drop is picked up with a cable run from the Start Controller to the Decoder running to a start pulse box.  See further in this document for details.

The First loop is put at the bottom of the Start hill.  Normally about 10m (30') from the gate, this measurement is not critical and basically goes wherever suits. 

The Corner 1 Entry loop is placed at the entry to corner 1, the main thing here is that it is parallel with the first loop.

The Finish loop is also two parallel conduits run across the track. The finish is when the transponder is exactly in the middle of the loop.  With the transponder mounted on the fork this puts the front wheel just touching the finish. 

Extra timing loops can be added at various positions around the track.  These loops give split times around the track when used with the Sqorz training software.  Uses for these intermediate loops are for coaching sessions and for commentary to assist the announcers identify the riders and positions.

Decoder Cabling.

The Decoders are normally in the scoring/registration office.  Cables are required from the decoders to the timing positions.  The cables from the loops are coax type cables (RG6 or RG59). MYLAPS coax is recommended for 2 reasons:

• it connects directly to the loop without a BNC connector (bad BNC connections can be a source of timing issues)
• using MyLaps coax means you will have MyLaps equipment from the loop all the way to the decoders

Start Pulse Cable

The start pulse cable is run from the Hill Decoder to the start controller.  Any 2 wire insulated cable can be used. It can be buried or overhead cabled, it should be in conduit to protect it.  If the Start Hill has a roof it can be run along the roof to reach the start controller.  No connectors are required on this cable.  This cable connects directly to the Start pulse box.

Cables from Mylaps.

Track cabling supplied from Mylaps comes in the following sizes:

Detection loops

• ProChip detection loop 6m
• ProChip detection loop 9m
• ProChip detection loop 12m
• ProChip detection loop 16m

Optimum loop size is the width of your track + 2m (loops can be cut to size so always get something bigger than you need)

Coax

• 5m and connector box
• 20m and connector box
• 50m and connector box
• 100m and connector box

How to install track cabling.

Below is photos of how to physically install the conduits and cabling at the track.

MYLAPS advises loops running though conduits should be 100mm deep but they can be shallower.  Basically have them deep enough that they are not going to be impacted when doing track maintenance.  If you have a concrete start hill then run two cuts in the concrete across the track 600mm (20') apart. Lay the cable into the cuts and hold it in place with some silicone/caulking.

Timing Loops

The size of that conduit will determine what elbows, t-pieces and inspection points you use. The following pictures have all been made out of 25mm (1") pipe, which is enough for the loop.

Position of the elbows and pipes in the track

The elbows (ends of the loop) need to be 50cm past the white line on the track. Therefore you need to know where the sides of your track are, and where they will always be. This may require measurement from a fixed point at the venue so you can always tell where the ends of the loops are.

This also means you need to know “exactly” where the finish line is, and where it will always be. So measurements from the jumps on the track for instance are not accurate, and will change over time. So you need to measure from something at your venue that will not move (like a drain grate, or power pole etc). You will need exact drawings because the white finish line needs to be in a very specific place and over time this buried system will be forgotten.

Finish line position

The white line marked on the track goes on the last pipe in the ground. So when travelling down the finish straight, you will pass over the first pipe in the ground, then 60cm later you will pass over the second or last pipe in the ground. The white line must go directly over the last pipe.

For this reason you need to put something in the ground beside the track to mark the finish line, or have a way of measuring exactly where that pipe is as you will need to remark it both during a race day and once or twice a year when using the finish line.

It is also very important to know where the sides of the loops are, so that you can paint your white lines in the right place each time. The track may change from year to year and move away from the correct positioning of the pipes.

Start Straight loop position

This doesn’t matter. The start straight loop can be anywhere near the bottom of the start hill. There is no specific measurement for this. It’s a good idea to keep track of the exact distance just so you know where it is when digging your track at a future date. You will also need to know where the sides are. Over time tracks get wider or narrower based on dirt work by different people, and without marking on the start hill, or some measurement, you may well end up with the track running outside your loops in the future.