A flanger and a spreader are two different machines and perform two different functions. When you have snow building up between the rails that is likely to melt and refreeze as ice against the flangeways, you need to use the flanger. If you need to wing the snow back from track to make room for more snow, you use the spreader. The pilot truck flanger that all then engines had was good for clearing snow close to the rail, but to do the job of clearing deeper snow/ice from between the rails, you need a drag flanger.
This is why they left Antonito with the flanger behind the lead locomotive. The spreader behind the second engine widened out the cuts. Somewhere in the day's odyssey, it was decided the flanger was not really needed and they needed to wing the snow wide from the track. Perhaps the snow was deep and they wanted the spreader between the engines for stability.
The drag flanger was operated by the engineer on the locomotive ahead. Main reservoir air was piped through a valve in the cab to operate the drag flanger. A similar valve operated the pilot truck flanger. The engineer had to be on his toes knowing where the hidden cattle guards, crossings and switches were to raise the blades at the right time.
The Jordan Spreader also used main reservoir air from a locomotive ahead. However it carried a large air reservoir of it's own, as well as it's own crew of to operate the blades.
It was standard practice to run all trains south of Alamosa with both locomotives on the point, then cut the lead engine back in the train in Antonito. In the winter it was common to see a plow-less locomotive on the point leaving Alamosa, with the plow-equipped locomotive, second out. At Antonito, the lead locomotive would get cut into the train, and the plowe engine would be on the front. It seems to me I have seen pics of flanger/spreader trains run like this too, but John's pic of 487 leading the way out of ALA says something different....
