also want to add, that it is best to get someone to walk behind with you, prior to getting her to pull the wheel. Get this person to drag a broom or rake, and then progress to a plastic feed bag with a little gravel or small stones int it. This can be shaken as you walk, to create a variety of noises. Also later, once she is pulling the wheel, get another person to hit the wheel with a stick as you longrein. Start little taps and then louder, start on the rubber, and when she accepts that without worry, progress to hitting the metal rim as well, lightly, but a bit louder as you go on. Put variety into the sounds which your helper makes. Don't do it all at once, do different noises on different days, later you can do sessions where several different sounds are made. Do all stages gradually so that horse just gets used to a lot of different noises behind her. When she is going well, it is also a good idea to get her pulling the wheel over various surfaces- when you get onto the ashpalt or tarmac road surface, that rim is going to make a lot of noise. ( grating and clanging) so she needs to be prepared. After she is happy with the road sound, try her on gravel, that is a different sound again, and also so through some tall weeds or grass to get a good whoosing sound. And if you are agile going over rough ground with dips and uneven surface is good. Try to aim the wheel so it goes over potholes part on hole and part out of it, so that the wheel dips and the traces will be felt against the horses side. She will also feel an uneven distribution on her chest. All of this is going to make for a horse that will not panic when the unexpected happens when you are driving, so it is well worth taking the extra time, in terms of weeks, to achieve a bombproof relaxed horse. Also I would not put her into any sort of shafts, until she is bombproofed with the wheel. When she is unfazed by all of the stuff the wheel wheel gets her used to, you then move on to introducing the shafts. Before I go on to shafts, I personally use 2 timbers or even straight branches cut from a tree, they need only be the length from about 6" in front of horses front leg- (dont let go past front of chest) to the horses end of rump. Aim for about 2" diameter..get someone to lead at head, while you longrein, she will need help in turning left and right to begin with as the shaft will come into play against her side. Once she gets that, add the wheel again, making sure that the shafts wont get caught up in anything, and spend a few sessions letting her get used to having something rigind against her sides, while pulling weight. But definitely I would not even think of introducing shafts until she is unflappable with the wheel. And I strongly recomend always having an assistant with you.... also, the wheel should have a swingle tree attatched to it, which is a piece of wood tied on across the top of the rim- you will need to experiment and position it so the wheel doesnt turn over. Tie it to the holes in the metal rim, so it doesnt come apart, but with enough play to let the ends move forward and back about 1". This will prevent soreness to horse, and also keep the traces apart. I carve out a notch all around the diameter, about an inch from end, to loop baling twine around which is then attatched to the traces- that way the loops don't come off, and if you have to get the wheel unattatched in a hurry, your assistant can always doit quickly by cutting the twine. Also, always have a knife or scissors with you so you can cut her free in an emergency, and always have someone to assist you, especially when introducing new things.