I reviewed the illustrations again, and I now noticed what did not sink in before; on the plate posted by Hans - Karl Weiss here: http://www.napoleon-series.org/cgi-bin/forum/webbbs_config.pl?page=1;md=read;id=122094

The strakes on the wheel show distinctly. Looks like nailed strakes, the nails would be grouped at either end as shown in that plate. I have just realized that the nail pattern seen there is identical to that which I instinctively chose for the wheels on a 1:12 model of a stake-side spring wagon for seige-cannonball transport, based on a Napoleonic era motion-picture fiction. I had read about the 5-nail pattern in Sturt's book, though he did not illustrate what actual pattern he used in his shop (his small-town practice would have used what was traditional to the family business).

It's hard to tell at this scale, but the gaps between the strakes are probably drawn slightly exagerated for clarity. The plan view and overall detail of that plate makes a lot of things clear.

The front-axle view shown is very similar to the average farm wagon axle assembly of the period. The part marked "B" which overhangs the hub is called the "sandbar," and helps keep dirt and mud from falling into the open rear of the wheel-box (the actual internal cast-iron bearing inside the wooden hub). In the larger front view shown in a previous post, the lower iron bearing-surface of the axle-arms appears to be one long iron band reaching from the end of one axle-arm across the bottom of the axle-tree to the other, and with the bearing-ends curved and inlet into the bottom of the axle-arms.

The wagon-box support above the sandbar has a specialized name too, but my memory is getting fuzzy and I don't recall it. On a removeable-box gear there would be two upright braces, one on either end of that piece, and the box, or other cargo (logs, for example) would fit between; the rear axle assembly upper piece would approximately match this.

I feel that I did not clarify the main purpose of a "reach" spar; mainly to tie the front and rear running-gear together, providing some rigidity which would otherwise have to be provided solely by the wagon body.

Since the caisson box does not appear to be intended to be removeable in the multi-use sense, the construction requires the offset spar, as the rear-axle assembly shown has been made a little simpler than that on a removable-body/multi-use farm gear, and the spar as shown would indeed have some flex to it. It would not , however, provide for a smoother ride (in the way that a spring-wagon would), so would not be a shock-absorber in that sense, but in the sense of contributing to the overall sturdiness and flexibility of the vehicle for rough military usage.

Regards, John