Your tractor looks great, and is indeed built strong. I too have built some with 2x4, and realized that 2x2 is sufficient. I have been taking 2x4 and ripping on my table-saw and saved a bunch in that most 2x2 cost the SAME as 2x4.
I want to say you have given us a great concept for wheels! I have been trying to figure a way to get 'flip-up-wheels' without buying the commercial type that costs $20 each!
I want to say you have given us a great concept for wheels! I have been trying to figure a way to get 'flip-up-wheels' without buying the commercial type that costs $20 each!