Plenty of good ideas out there. I think foremost the question needs to be answered if once filled do you ever anticipate needing/wanting to remove what it is filled with? If the answer is yes then anything other than a liquid would pose a considerable impediment (including sand). If the answer is no then "skies the limit". Here are a few offerings with pros and cons which may or may not meet with consideration:
1) Water
Pros: Cheap, readily available, easy do-it yourself.
Cons: Even if topped off with no air space it will rust out a steel drum (think chemistry - H2O - water contains oxygen). If used year round would need to be drained. If water is left in the drum (even with sufficient air space to allow expansion) once the water freezes it will make the drum out of balance and slowly tear your equipment apart.
2) Antifreeze
Pros: Won't freeze if used in the right ratio, would require drum to be "topped off" to eliminate air spaces, an easy do-it-yourself project.
Cons: Initially expensive (unless you can acquire used antifreeze from a local autoshop - particularly one whcih services semi's) but will likely outlive the user unless a leak develops, toxic to animals if a leak develops.
3) Calcium chloride
Pros: Won't freeze, readily available.
Cons: Similar cost to antifreeze - not likely to get "used" cc, probably not a do-it-yourself application unless you have the equipment, will rust out a steel drum if all of the air is not removed (highly improbable unless you can place it under a vacuum).
4) Beet Juice
Pros: Won't freeze when applied the same as for filling rear tires, non-harmful to the environment.
Cons: Availability may be limited which may affect cost.
5) Rim guard
Pros: Won't freeze, doesn't require all of the air to be evacuated.
Cons: Likely more expensive than antifreeze or cc.
6) Sand
Pros: Easy/cheap to acquire.
Cons: May be difficult to fill drum, if sand is not 100% dry (absolutely no moisture in sand or drum) it will freeze solid and put the drum out-of-round and shake your equipment apart over time.
7) Concrete or preferably gunnite
Pros: Relatively inexepnsive, can be placed into the drum just like any other liquid.
Cons: Very permanent - you will never get it out.
8) Used motor/hydraulic oil
Pros: Readily available, won't freeze, easy for the do-it-yourselfer to apply, won't rust out the drum, allows you to re-purpose all that motor/hydraulic oil from your tractor.
Cons: Not environmentally friendly if drum leaks.
I am sure I have missed other options as well as pros/cons for option listed so hopefully others will add to the list. I know personally, my neighbor and I built a custom roller to be able to compact our gravel road (about 2.7 miles). The drum was fabricated out of an 18" steel well casing filled with concrete. In addition we built a cradle over the center of the drum (axel) to accommodate up to a 1,000 lb concrete block for addtional down pressure. It was perfectly balanced such that my 10-yr old daughter can lift the tongue. We put a standard ball hitch on it so we could tow it behind either a pickup or the tractor (when get a chance I will take a photo of it - right now it is under 4ft of snow). I am not saying this is the perfect set up but it has worked well for our application so far.
Mike
