Thanks for the responses, the seller has refunded my money, I understand that there is NO secondary liability and that's that. I had not really wanted to discuss this any further as I have come to a satisfactory resolution with the vendor, but since Mr. gridlok wants to go into all the gory details..........
As far as chain tension issues, the item was given to me with no instructions. Is there some way that I could have known the chain tension is to be set "tighter than you think it should be" as that seems to be metaphysically impossible. Since I did not know what I did not know (and there were NO instructions), I simply set the chain tension to what Shimano suggests for their hub. This has worked for 167 miles with only 3 derails using the stock chainwheel with a misalignment of about 3/8" to 7/16". The replacement part was installed using shims to position it about 1/16" away from the chainstay giving a misalignment of less than 1/4". In 6 miles it derailed at least 7 times: each time sucking the chain up into the chain-stay and jamming the rest of the chain between the sprocket and the drive.
3 derails in 167mi vs 6 derails in 6 miles and the new part improved the chainline, yet it derailed constantly. And when it derailed, the extra long teeth on the sprocket grabbed the chain and ground it into the chainstay something that never happened with the OEM part. One factor that contributed to the derails was the fact that each derail bent the narrow tooth nearest to the sucked chain which did not help things at all. Are these teeth usually so fragile these days? I stopped riding MTBs back in 2004 or so and I do not recall ever bending a tooth on a chainwheel Back in the Day... If this part is so fragile that it will bend after a single derail is it really suited for purpose? BTW I put the OEM part back on and the chain does not come off of it.
Now the stock Bafang chainwheel may be a horrible "steel paperweight" and it may be 5 or 6 teeth short of the correct diameter, but it refuses to derail for me despite its terrible misalignment. The aftermarket part is simply not workable in comparison. I preordered this item in good faith and installed and operated it using standard industry practices in the complete absence of any instructions otherwise, just as any consumer would. Had I known that I was expected to be a Beta Tester of a prototype, I would have postponed my order, but that never came up when I was personally handed the part by the vendor.
I have made arrangements to have the technical editor of a nationwide electric bike magazine test the BBSHD by riding my bike in early January. I had hoped that they would take a few pictures of the installation for the magazine, but my bike got a bit beat up during this whole exercise and is no longer photo worthy (thus my annoyance). Fortunately I have another identical bike arriving Wednesday and I will install a new BBSHD with no scratches for the test...... If they like it I will propose they pick a bike from their fleet and I will come back with another BBSHD and battery pack and install it while they watch (and hopefully photograph). And I guess I will be using the stock chainwheels.
Finally, I refuse to apologise for not wanting my stuff to look like shit........ It is nice that you feel otherwise as regards your things, but I feel no obligation to follow. :lol: