sheet steel, approx 1.2mm thick
approx 30cm (12inches)wide
approx 17inches or 43cm long
sheet steel most easily welded with mild steel, and same with the 12mm diameter 50mm long round tube or bar, try to have both made of same material if possable, for better weld strength.
sleigh will weigh only very light, perhaps a kg or two?
unless you want to use stainless steel? it will last longer, look nicer, be a touch heavier and be harder to bend to 30% without the right tools.
if you know knowbody at all with a welder, try the local Trades collage, apprentices there doing it for free?? if that fails, perhaps you could try a “Locktite” , its a special trades glue available from your local tools store, they could guide you to the proper stuff, they may even be able to weld the bar/tube on??
i have one made from galvanised, approx 1.2mm thick sleigh, possably now down to 0.8mm from yrs of usage? only 1 problem in the past 6yrs, is at one stage lost a shackle, but a tempary split pin worked till i fixed that!
On crap grass track, it worked smooth, fast and the pull was very even. And that was at times towing 15kg. Handles corners (if you want) by following the lane you are in and not swaying off to other lanes, unless you do yourself?
Sometimes though, if big chunks of tuff grass or if the shackle comes undone, then things go silly, to be expected though. Just make sure things are tight, rope is secure, track is clear of debrie and welds are good each outing, common sence stuff.
not if your using gym disks. depends on the weights your using to the length of the tube/bar. normally a disk is around 1" thick, or so. so an extra 1" to stop it bouncin out. Adding extra plates will lead to longer bar, or just use a heavier plate? 100mm or 4-5" or 10cm, any longer than that and it just looks silly, and starts taking up more room in the boot of your truck as it becomes an awkward shape. So, if you got the room, go for the longer rod.