Piston and crankshaft

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Adding rings is only needed if you are increasing the compression ratio, as in diesels, because the blowby will increase as consequence. But then you'll need to reinforce all of the others components (conrods, crankshaft, bearings) and rebalance both the crankshaft as well as the secondary balance shaft, but that is sometimes ditched when an engine get modified as it only benefit comfort reducing the vibrations felt.
As for the point about flammability Steamchick was making, that is true and a real danger in some settings; like in a laboratory or in confined spaces where the hydrogen can mix with air. But in case of storage/transport tanks (as in vehicles) it is pretty safe because tanks are made and tested to withstand a much higher pressure than what they see in real use and the gas inside is pure and compressed so much that is impossible for air to get inside and form a "bomb". The hydrogen used by the Hindenburg was inside cotton bags at atmospheric pressure, not really the best storage method for an highly explosive gas...
Also Hydrogen is also much lighter than air so any small leaks will gust rise, causing accumulation only if under roofs or ceilings.
 
My point wasn't about proprietary tanks leaking by permeability. But that Hydrogen leaks through materials and joints better than anything else can, because the molecules are the smallest in the universe. Sub-atomic particles are smaller but that is irrelavent here.
In the UK, for plumbing hydrogen lines inside a building, we had to engage a specialist contractor with certification, at a high cost, to install the system. The Co tractor fitting-out the lab didn't have that certification because hydrogen requires such special controls. Gas piping could be steel, copper, etc. But hydrogen must be seamless steel tubes with metal to metal joints, etc.
On fuel tank so we used helium leak testing for the plymer tanks. The smallest inert gas molecules that permeate most plastics.
I don't know, but have an idea that Hydrogen carbon fibre tanks have a layer of aluminium foil, as the polymers would leak without it. Like crisp packets and other hermetically sealed wrappings.
But don't quote me. DO YOUR RESEARCH. CHECK REGULATIONS. They are there to keep everyone safe.
K2
 

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