I picked up a, 09 16' Ultimate Multi Sport Propel that came with a Smart Cart.
I have several Kayaks and carts, and use my golf cart to pull them to the lake about 1 mile away. I have to do this since a locked gate prevents me from just driving down to the lake.
I pulled my 16' on the Smart Cart very slowly. about halfway there the center part of the axel snapped. I had to leave the Kayak there and go get my truck to get it back home.
So I started a search locally to see if I could find a piece of aluminum pipe with the right dimensions that I could use to make a replacement part. I had no luck until I tried Home Depot and found a stainless steel closet hanging rod. It comes in two parts with the smaller one being the perfect size for replacement. It was over twice as long as the piece the broke. I cut it exactly in half and ended up with two pieces about three inches longer that the original center axel. Using a 7/32 bit I drilled a hole dead center through the new pipe. This accepts the original clip perfectly. Using the broken axel as a guide, I drilled two holes about 1 " from the end of each side.
I reassembled the axed and it is better than the original. I give provides a 1-1/2" wider stance for the wheels on each side. I had had trouble with the wheels rubbing the side of the Kayak when pulling it. This 1-1/2 "extra gives plenty of clearance.
In addition, the stainless steel rod is stronger than the aluminum that comes with the Smart Cart, partially because Stainless Steel is stronger than Aluminum, and the walls of the new axel is actually a bit thicker than the original.
In addition, I removed the two straps that came with the cart and replaced them with ratchet straps. This allows me to get the straps a lot tighter that the originals for a more secure.
Hope this idea may help anyone with a broken axel. I'm sure I'm not the only one.