Interesting picture of a chain drive vehicle in motion. Notice how the chain arches upward behind the drive sprocket.
Thank you Jay, for yet another wonderful photograph.
Hey Bill, I think that is an indication that the chains have not been properly oiled and they have gotten stiff, notice there are at least two kinks in the upper portion of the chain. This is a precursor to premature failure due to the pins being frozen in the bushings of the inner links.
Actually the chains are to loose as they are slowing the truck down, hence the bowing of the drive chain. The jack shaft is slowing and the rear wheels are trying to go faster.I had a 1 cylinder Reo chain drive truck and the very same thing happened until I adjusted the drive chains.
Finding a 1905 automotive service book the correct deflection of the chain is inch and 1/2 when vehicle is unloaded.
Notice that they are bowed outward top and bottom. The kink just visible to the left of the rear tire in the photo. I would bet the truck is either stationary or moving slowly at an even speed in the photo.