My concern with the Chain-ring/spider was that there could be a step if one was flat and the other rebated and, as I'm not trying to 'cobble it' together on the cheap I would rather go for the right tool for the job..
My SS project was just a way of using a frame/fork which had been donated to me. I had enough spare parts to build most of the bike and only had to add about £70-80 worth of new bits so it
was done on the cheap, but that was always my intention. I wanted a bike that I enjoyed riding, but could use for shopping trips without worrying about it getting stolen. I would not be happy if it did go, but at least it wouldn't have cost me a lot of money. Also, the fact that it is fairly obviously a 'hack bike' means that it is much less likely to be worth someone risking cutting off the huge D-lock that I use.
@ColinJ you suggested washers but on which side of the chain-ring did they go? Are they possibly to eliminate the 'step' that I've mentioned? Did that mean you used the original length bolts too?
On the inside of the spider. I used the original big ring but removed the little ring, which left those 'steps'. I had to file flats on one side of the washers to get them to fit. Yes, bodgery, but I wanted to see just how cheaply I could build what was still a pretty decent bike. The washers are hidden away on the inside so they are not obvious at a first glance. Everything looks normal from the outside. Yes, the original bolts were used.
With regard to the chain tension, I also thought about eliminating any slack by carefully choosing the right size chain-ring/sprocket combination but how would I know without going through an expensive trial & error process?
I already had a spare 52 tooth big ring and had decided to use that. I worked out that a 19 tooth sprocket gave me the best compromise gear ratio with that ring (high enough to not spin out too often, but low enough to get up Cragg Vale - a 5 mile local hill with an average gradient of 3.2%, and with just a short stretch at about 8%). It turned out that a new chain with that setup had almost no sag on my 58 cm frame. The chain tensioner was barely touching the chain. Pure coincidence though, I hadn't calculated it!
I didn't realise that the chain stretched so quickly as I already have a lovely steel Genesis SS road bike and can only ever recall altering the tension when fixing a puncture.
It was a big surprise to me! The tensioner was almost quiet with the new chain but it didn't take long for the chain to elongate and the tensioner to start working. The chain elongation seems to happen quite quickly at first and then slow down. Or maybe it is just that the initial wear is so obvious - going from no sag to some sag is more obvious than some sag to some
more sag!