Baja build part 37. (Additional) Telemetry & PB Killswitch
Additional Step: Spectrum DX3S Telemetry & PB Killswitch
As the Baja SS kit came with no radio gear we opted for the (Spektrum DX3S). This was specifically chosen because it has the ability for onboard telemetry. Basically this allows us to monitor receiver battery voltage, engine temperature and also rpm/speed.
Whilst we had the engine on the workbench we decided that this was a good time to fit our temperature sensor and add our remote PB Kill Switch so that we could shutdown the car from our radio in the event that it develops a fault, the battery runs flat or it becomes sentient and decides to enslave mankind…
To fit both the Spektrum temperature sensor and the PB Kill Switch the two engine covers first had to be removed. We decided that there was no need to remove the pull start assembly at this point. Undoing the three cap head screws and the two Phillips head screws from the side engine cover allowed us to remove the entire cover. The manual kill switch was easily slid out as we laid the cover down on the workbench.
The top cover was then removed as well by extracting the one remaining cap head screw in the other side. The HT lead to the spark plug was unplugged and slid out of its retaining slot to allow us to remove the top cover entirely. We only needed to remove six screws in total to get to here!
The PB Kill Switch wires now needed to be soldered to the existing HPI kill switch1, which was first detached from the magneto (the bit that generates the high-voltage spark!) by unplugging the two spade connectors. Our PB Kill Switch wires were soldered onto the now exposed connectors and the switch re-connected. The PB Kill Switch itself will eventually connect these wires to the 3rd channel on our receiver.
To fit the Spektrum temperature sensor, the top screw holding the magneto needed to be removed and the lower one loosened just enough to get the sensor loop up around the engine head and down between the two screws (see photo below). Once this was done the screws were re-tightened whilst ensuring that the magneto didn’t bind on the flywheel. The loop of wire for sensing the temperature was positioned just above the exhaust port at the rear and one of the small silicone tensioners tightened up to hold it in place.
With two extra wires floating around our engine head we fitted a cable tie (in front of the silicone tensioner on the temp sensor wire) to ensure nothing would foul any of the moving parts.
Both covers were re-installed and the two new wires routed down from underneath the head as shown in the photo below.
1 there are many kill switches available on the market but we chose the cheapest PB KillSwitch (Kit 1). There are three PB kits to choose from; Kit 1 is the cheapest and does not come with the necessary wire for soldering to the manual kill switch on our engine. Kit 3 has the additional wiring and a pre-soldered drop-in replacement manual kill switch. Kit 5 is identical in fitting to Kit 3 (is PB allergic to even numbers?) but additionally supports a number of led head/fog/spotlights. To connect our switch to the engine we bought a red/black “BEC” lead with connector from a local hobby shop.
Apparently PB *does* make kits 2, 4, 6 and even a 7! Thanks for letting us know Kent!