Tutbury Tractoring
As you might have seen on one of 2mm threads, the tractor and its test bed put in an appearance at the Tutbury gathering yesterday.
Several folks had a try at tractor driving and several politely declined. Apart from hopefully being entertaining for the budding driver it was interesting for me to see what happens with someone else at the wheel.
Full marks to Laurie Adams for being the only person to attempt and complete the full tractor shunting challenge (swap an incoming full tank with an outgoing empty one).
So apart from having a good day out and a deadline to actually make me get things done, what did we learn about using the tractor under the gaze of the public ?
- People unfamiliar with the tractor seem to start off by driving very slowly. This is understandable but I'm not sure it's a good strategy because as well as the tractor moving forward more slowly the response to the steering also takes longer and the driver has time to over correct.
- People have different 'muscle memory' of what a rotary control should do. It is a bit confusing for a long time model railwayist to be presented with a handset on which the rotary control is a 'steering wheel'. Figuring out which is left and right can also be a challenge when the tractor is pointing in different directions (not surprisingly, radio control modellers tend to be better at this). Things get more fun when you then hand them the other controller so that they can do some shunting with a loco. I don't think there is anything to do here other than to watch knowingly while they get used to it although using a Powercab DCC controller for the trains might be easier on the brain.
- The test bed was kitted out with more dummy scenery and buildings than last time so there were more opportunities to collide with the landscape. Not unexpected but if the driver keeps the throttle open then the tractor will part company with the magnets underneath. After this happens it is tricky to 'find' the magnets again... the extra stuff on top acting as a disincentive to lifting the lid to figure out where the magnets are. This is a good lesson because it won't be possible to lift the lid when the tractor is installed on the layout proper. I have some ideas about how to make it easier to get out of this pickle.
- Sometimes the control system's centre position drifts over time. This is probably because friction or collisions up top are creating more resistance than the steppers can handle and they 'lose steps'. This is a job for some more Arduino programming - at the moment it only 'finds' the centre when it starts up but with some work it can also correct for lost steps while it is running.
- I did managed to get the tractor stuck 'in a corner' once between the limit of lengthways and widthways travel so need to give a bit more thought to the way that the limits work to prevent that embarrassing situation. Luckily nobody was looking.
- More visual feedback (probably some LEDs) is needed when the magnets are moving without anything visible 'up top' before and after the gravity shunt.
On the whole it kept running for the whole day with very few unscheduled stops to lift the lid and sort things out manually. As far as I know it only went completely pear shaped once when the carriage swing arm somehow managed to swing a long way past what should be its 60 degree limit. I thnk I was watching Parkend when it happened so I'm not sure how it got into that state but the bigger concern is that even with a 'standard IT fix' (turn it off and on again) the thing couldn't sort itself out without extra manual help, so some more work needed there.
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