Generator Problem Report from Michael Parris

Nomad suffered a major mechanical malfunction yesterday. We suspect than a leaking gasket combined with an oil level sensor malfunction led to engine seizure and subsequent fracture of the crank case.

Liam and I went to Camp Cricket at approximately 18:30 to start the Nomad generator. Poor visibility and blowing snow this morning prohibited early start-up. A late afternoon break in the weather allowed us to reach the robot at the remote camp. The generator started easily yesterday, on the second turn of the key. Normally it takes 15 to 20 minutes of coaxing to start. Approximately five minutes after startup, the generator shut down abruptly. The loud cracking noise we heard on shutdown was unlike any I have heard from this generator before. I attempted to restart the generator with the ignition switch at the back panel. The engine did not turn. I proceeded to try the manual pull start inside the lower front panel of the robot. The engine still would not turn.

Suspecting the worst, I returned to the FACH camp to speak with the generator technicians. I explained the problem and asked them to come out and have a look. Alex, Christian, the two mechanics and I returned to Nomad. We removed the valve cover, attempted to move the valves, tried again the pull start, and verified that the engine had seized. We removed the front shell and gas tank to gain better access to the generator. The top of the crank case had fractured. Possibly, when the engine seized, the push rod broke and struck the casing.

The Nomad generator had been consuming more oil than usual. This generator has an oil level sensor which grounds the line to the spark plug, shutting down the generator if the oil level is too low. This sensor caused the generator to shut down on the evening of 11 November. The oil level was 1 quart low. The generator would not start even after adding the full amount of oil. The spark plug was still not getting power. We suspected that the sensor itself was stuck or frozen. We traced the wires and disconnected the oil level sensor, reconnecting it after the generator warmed up. This first alerted us to Nomad's excessive oil consumption. I had changed the oil in Punta Arenas, and checked it twice prior to this first incident. Until then it seemed to be functioning normally. Since then we have been trying to closely monitor it.

On 14 November, I checked the oil and added a small amount, less than 1/2 quart. Again on 17 November, I checked the oil and added nearly 1/2 quart. On the 18 November, we had difficulty starting the generator. Oil level looked ok. I disconnected the oil sensor, to eliminate one of the variables. I reconnected the sensor later that day. In hindsight, I should have checked the oil this morning. But I suspect by this point our time was limited.

The oil level sensor was connected at the time of the generator failure yesterday. I suspect the failure of the oil level sensor was caused either by faulty wiring, damaged in disconnection and reconnection, or sticking of the sensor itself, due to gelling of the oil.

An option is to power Nomad from an offboard generator. We could mount the generator on a sled to be pulled behind the robot. This too will require major effort in rewiring our main power supplies, but the downtime is likely to be only one day. The robot is already equipped to run from wall power with two in-line isolation transformers, one for the electronics, the other for locomotion. However these isolation transformer can deliver 1000W maximum. This is sufficient to drive the robot on a smooth level floor and power the computers, such as in Bldg E. It does not account for driving on hills or rough terrain. Nor does it account for the heating system, which was a late addition. Currently there is no way to power up the internal and external heating systems from the remote power source. The electrical modifications we will make will allow us to power the electronics through one of the isolation transformers, and run separate lines for the heating system and locomotion system respectively from raw power. While it is not ideal, this solution is fast and will allow us to proceed with our research agenda. It is the feeling of the group that this is our best option.

We have requested documentation of the power distribution system from Tony Nolla. Mark, Alex and I will begin ASAP. We hope to have Nomad running from offboard power by tomorrow evening.

Expedition Report from William Cassidy

25. Nov. 20, 1998, Friday: Patriot Hills Camp

Before making a decision on what to do about Nomad, Alex wanted Sib to study the wiring diagrams for the generator. We already knew that its sister, the one that had just failed, had been modified to some degree to be able to fit into the volume occupied by its predecessor, which had been a smaller model. Under consideration are the possibilities of (1) removing the broken generator and replacing it inside Nomad with the one we have in camp, and (2) cutting the old generator out of the circuit and wiring the new one in, but leaving it outside Nomad and towing it on a sled.

Alex talked to Tony over the Inmarsat phone, and Sib, in a separate call, helped him find the wiring diagrams. Tony copied them and e-mailed them to Sib. At this point, my appreciation of the Inmarsat facility we have here increased enormously.

If we can use the 5 kW generator to revitalize Nomad, we will still have two 650 W gasoline generators in camp. One is enough to run everything we have if Alex's radar experiment is not online. If Alex were to operate his radar we would have to shut off some other things.

At present, while Sib studies the diagrams, we have little to do. Until we can get a source of power into Nomad, Liam's first results and Stewart's obstacle avoidance results are frozen in the robot's computer. We all, including Nicolas, stand ready to do whatever we can to help, when the time comes.

After dinner, Sib concluded that hooking an external power source in to Nomad would be quite simple, involving cutting one cable and attaching two new ones from the new generator to the severed cable. This made our decision very easy: we will leave the new power source outside of Nomad. The alternative is no longer an option: the Polarhaven shelter is not available; it would involve a lot of work in the field, under conditions in which to touch metal with the bare hands would cost skin; and there will be a great savings in time.