My son bought an old road bike, we didn’t notice that one of the small bolts connecting the two front chain rings was missing and he has now twisted and broke the inner chainring. I’ve been able to remove the smaller inner chainring. Is it safe to use the bike with just the larger outer ring or does the design rely on the two rings to be connected together for strength and rigidity and therefore likely to buckle/break?
You can remove the inner chainring without compromising the strength of the crank.
However, this will mean you will have to 'cross-chain' from the outer large ring to innermost largest rear sprockets to obtain lower gear ratios. Doing this accelerates wear on the chain, sprockets and chainrings.
Small chainrings and bolts are not expensive. Installing might require pulling the crank off the bike though.