Mods for the Caffin V4 stove

First the big thing – I have added a piezo ignition. It’s worth all the extra weight (very little this time) when the stove is in a windscreen. What’s nice that this type of the burner (with low velocity of the gas) lights reliably even with a weak spark, so the sparking device from a pocket lighter is enough. I’ve added piezo igniter also to my other stove, but it had to be a more substantial (read heavier) one made for grills.

The piezo is housed in a cut-down black syringe that provides nice tabs for fingers. Then there’s a length of PTFE-insulated wires (strong, heat-resistant, and suitable for high-voltage). On the stove, the wiring is housed in a block of PTFE serving as an insulator, and a stainless steel rod delivers the spark to the burner.

A second mod is a knob for the tube extending the valve. The stove works without it, but now it may be easier to handle in gloves. What’s more important, the bright orange knob will make it more difficult to lose the thing. 3D-printed, easy to design and quick to print.

A third mod is on the way – I have to add an anchor for clipping the stove to the base I’m using on snow. Now I’m waiting for a special screw I had to order.

That’s cool!!

Question: can the piezo drop be secured to the fuel line in order to keep everything neat and tight?  Inside some sort of flexible conduit, perhaps?  It would be sweet it that could be safely done; a clip-on piezo igniter would be even sweeter.  Could the guts of a regular piezo be installed into some kind of 3D-printed dingus that would serve such a purpose, or is that not possible?  Forgive me if that’s a dumb question: I never use piezo igniters because they’re always in a bad location and I find them cumbersome…thus my fervent interest.

Nice work on a cool system.  Very clever about the dual duty stove base/shovel.

Could you incorporate the piezo clicker as the gas control knob?

yeah, great mods

I really like the piezo lighters on my Soto and MSR stoves

The big knock on piezo lighters is they break.  Both of those still work, but…

With your mod, it would be easy to replace if it broke

I have a V4 stove…Jan – any chance of you selling the knobs?  Our last transaction for the saw handle went pretty smoothly…

OK, I am seriously impressed by the piezo! It is very neat and tidy.

Cheers

I wonder if the red heavier piezo would work above 10,000 feet elevation

Piezos are supposed to not work at elevation

Jerry,
I don’t think there’s any other limitation related to the elevation than having less oxygen in the air – fuel mix. For a given composition of the mixture, there’s some threshold for the energy of the spark able to light it. The big piezo certainly delivers more energy, so I suppose it would work. (This is a hypothesis based on what I learned around here, and I’ve no mountain around high enough to test it.)

+1 on Jan.

Cheers

I have read that piezo lighters don’t work above 10,000 feet

I can’t think of a time I’ve tried a piezo lighter at that elevation

There is a complex relationship here. There is an optimum fuel/air mix for ignition: too much air or too little air and it won’t light.

In addition, there is a minimum energy requirement for ignition: something has to break down the first few molecules of fuel before they can burn, and that takes energy. Of course, once burning starts there is plenty of energy around. I think that minimum energy required may also depend on the fuel/air mix: too few or too many fuel molecules in a volume make it harder for the spark to work.

So what happens at high altitude? This is my GUESS, based on what I do know. I suspect that the lower air density at high altitude means the fuel/air ratio is way off, and a typical little piezo unit, designed for use at sea level, just does not have enough energy. Bear in mind that some of the little piezo ignitors around really are quite small.

But Jan’s unit may be bigger, with more spark energy created. I do not know this however: it just looks bigger.

Cheers

To the piezo ignition:

I’ve seen some plots of the energy needed to ignite the mixture as a function of fuel/air ratio, and they looked like a parabola – there’s some optimal composition, and more energy is needed when the ratio deviates from it in any direction.

From my experiments, I also know that a success with a small piezo (used in lighters) depends on the construction of the burner, and it seems to be related with the velocity of the gas coming out of the burner.  This may be caused by the velocity itself, such as by faster cooling or blowing off already ignited region. Another possibility is that the mixture coming from such a burner has less oxygen and relies on mixing in more after it leaves the burner.

Whatever the cause is, stronger piezo works reliably where the smaller one did not, such as on my primus spider stove. The one I use can produce at least twice as long, brighter spark than the small one. The small one did not work with the Caffin V1 stove, but the same unit works great on V4 with its wider, silent burner.

And finally a photo of the third mod: I replaced the grub screw with a longer one, and screwed a pop rivet (with an M3 thread cut on the inside) onto it. The head of the rivet is held by a spring attached to the stove base – two versions pictured: a fixed one, and one that clips into the multi-use carbon one.

A stovey, definitely!