[canadian_tired]

Sometimes old tech is best tech! Thanks for this. Although, my experience suggests that using a drill bit to put holes in leather is not the way. What you want to do is punch the holes. Easy to do...find a short length of steel tube of the right diameter and grind a sharp edge on the circumference. Or, you can buy any number of punches cheap.

Most casual, but certainly all hard-core cyclists will know the legend of the Silca frame pumps. Silca has been using leather washers forever. Read more (why leather works and why o-rings don't) here: https://blog.silca.cc/uniquely-silca-the-leather-washer

[causi]

A leather hole punch is a handy tool. It's great for making holes of assorted sizes in almost any thin material. I use it for adding clean holes to my belts when they stretch out.

[mauvehaus]

Thanks for the link! MSR uses leather pump cup seals in their liquid fuel stoves, and it's nice to get some background on why this is the best choice from an engineering perspective.

I'd intuited some of the points in the article, but it's good to know that somebody has approached the subject rigorously, and taken the time to explain why leather is superior in this application.

[Xylakant]

In a fuel pump, the washer also has contact with substances that are aggressive to rubber: the stove fuel itself. I doubt a rubber o-ring would survive long in that environment.

[dwater]

There are fuel resistant rubbers available, most commonly Viton/FKM. They are commonly used in automotive applications.

https://en.wikipedia.org/wiki/FKM

[mauvehaus]

The pump cup, in theory, never touches fuel. And goodness knows MSR isn't shy about using O-rings. There are nearly half a dozen in a Dragonfly between the pump and the stove. They're using a material that holds up to fuel contact for those.

[elsjaako]

Most of this seems to be the advantage of cup-washers versus O-rings. Wouldn't that be possible with rubber also?