I pinched my thumb rather badly while reattaching the cotter pins that retain the wheels on my $40 Harbor Freight hand truck. Behold the blood blister aftermath! Why did I have the wheels off in the first place, though? Well, the hand truck was defective from the start. What a surprise.
When I bought it last year, all seemed well. But this spring when I was getting ready to move stuff, the tires were flat. They would not hold any air at all. So, it was time for an investigation, and learning how to change the tubes on a tiny tire.
The tires are held onto a solid axle with cotter pins, little bent bits of metal that poke through holes in the axle and wrap around just enough to secure things enough and no more. Then, the four bolts hold together two halves of the wheel. It is entirely unlike an automotive wheel where a one-piece rim is affixed to a hub with lug nuts. Removing the tire without splitting the wheel would be nigh impossible.
The problem was revealed after disassembly. Both inner tubes had small cracks about the size of my thumbnail that quickly grew at the slightest touch. No wonder they wouldn't hold any wind.
I bought a pair of new tubes from the local hardware store. I could have probably whined to Harbor Freight and gotten replacement wheel assemblies, but they would have probably had the same rotten rubber inside. Here, I might have something that might last a while. The valve stems here are brass, not easily-torn rubber, too, so that is a plus for something that might get bashed around. Sure, it cost 40% of the original hand truck price just to fix the tires, but if it lets the thing actually roll, it's worth every penny.
Odds are, of you have a small lawn mower, the repair procedure will be identical. So watch your thumb when wielding pliers to wrangle cotter pins!