crusader cooking unit & alcohol stove

[oops56]

A picture would help on that photon ok try this click on picture to make bigger als put a cover under it put some alcohol you may not be priming long enough

 

[Glen]

Graham,

I made a small photon for my crusader but canot get the meths to light in the fuel cup around the burner. I think it's lack of oxygen in the narrow 'trough'. Any thoughts on that?
for size info, my photon is made with a toast toppers / mini coke can and is about 25mm high.

Not had that problem myself, toast toppers / redbull can but designed in such a way that there's some alcohol that sits ontop of the stove. Blowing very gently across the top and lighting from the side or back might cure it, being very carefull of invisible flames, as that should get a more few fumes to rise from the trough into more oxygenated air.

 

[oops56]

ok i made lots of stoves that type needs a priming pan on bottom the prime from top is not long enough to make the alcohol boil just like water you dont boil it from top boil from the bottom

 

[Glen]

ok i made lots of stoves that type needs a priming pan on bottom the prime from top is not long enough to make the alcohol boil just like water you dont boil it from top boil from the bottom

Sorry, I wasn't very clear, In my case I have a little ontop as well as that around the side.

Though to take your analogy, to heat water evenly heat it from underneath, if you just want to get a little water vapour fast you can heat it from near the top at one side you can get a small section to boil without hardly raising the temperature of the rest of the water,

I don't think it's actually priming from underneath as such, I figured it actually heats the internal alcohol from the sides, top down.
Some of the faster priming ( and burning ) minibull design stoves have a bolt or stud to conduct heat down from the flame directly into the alcohol. Also very little of the stove actually touches the priming pan, just the outer rim.

Also the priming vapour is burning above the level of the well in the crusader burner, whereas with a priming pan it can burn right down to the pans surface.

In a reduced airflow situation, like there is between the ministove wall and the crusader well, having a little ontop alight helps keep an airflow going, the moving hotter air creates a lower presure, air from outside is drawn in which then scoops up vapour from the sides into the flow, the centre alcohol also keeps a flame burning that relights the side vapour as it rises if it's gone out. In my case in the top of the burner I've got 4 jets that are well inside the inner ring of the burner, so it also lights any vapour coming out of those long before that vapour could travel to the outer sides of the well, they might be having more of an effect during the priming than I previously thought.

 

[oops56]

ok one more thing how does the stove burn by itself just sitting on a bench northing over it not in the crusader cup burner its now all most 3 a.m. here i do a 2 or 3 test burns on mine see whats whats in the morning

 

[Glen]

ok one more thing how does the stove burn by itself just sitting on a bench northing over it not in the crusader cup burner its now all most 3 a.m. here i do a 2 or 3 test burns on mine see whats whats in the morning

Burns about as well as any other I've made of that type that I've also made that short, ie pretty much as well as a full height one, with the same amount of fuel, but a more difficult prime. In that situation having the extra ontop doesn't make very much difference but as I designed it that way for an easy fill ( the alcohol pours through the inner 4 holes and air vents out the jets in the outer rim ) I don't bother mopping it out or messing with trying to pour it into the priming pan that I use when in open air configuration. It's just that I've found in the crusader config it helps with what is a slightly more dificult prime.

It was noticing the slightly taller stoves prime better that made me start looking at how the priming happpens.

What seems to be happening (in an open air situation ) the fumes evaporate off the alcohol on the priming pan and burn a few mm off of the surface of the pan. This produces the heat which is hotter slightly higher up than very low down. The stove wall conducts the heat from the part that's in the hotter part of the flame down and transfers that heat to the alcohol inside Best way I've devised to show this is to put a stove filled with water on the priming pan and then treat it to a very short faux priming. Blow the priming flame out and pick up the stove with pliers, I've found that, to the touch, the top and top of the sides is hotter than the bottom and bottom of the sides. ( Wouldn't it be nice to have the outside wall made from a coulour changing temperature sensitive material ) The biggest temperature gradient seems to be at the fill level ( try it with different ammounts of water in ) That suggest that the initial interal alcohol evaporation would be coming from the top layer next to the outer sides ( things are different if you've got an Trangia type internal burner in which case I'd expect it to come from the top layer of the internal sides )

When used in the crusader cooker the shorter stove is only a few mm taller than the well and about 5-7mm smaller in radius. That only gives a small area ( a donut shape ) from which the initail priming fumes can evaporate and start the heating. As it's a shorter stove the the heat from the centre prime contributes ( proptionally ) more to the overall effect than it does with a open air config with a taller stove and priming pan, where it contributes only very little.

There probably be sweet spot where ( for open air priming ) the height of the stove will be best withing certain limits, but for use in the crusader, the stove has to be shorter than normal to fit nicely together in transport, hence why making them with a flat bottomed tin, to keep overall internal volume up.

It's occured to me, while typing this, that one way to get it to prime quicker would be to have 2 pieces of wire looped into 4 jet holes sticking up into the priming flames, conducting more of the heat straight down into the alcohol, hmm something else to play with

 

[oops56]

Hear is mine 3 Penney stoves all diff number holes on got two rolls of holes the pink is a small alum. hair spray can cut down then the Jeffy heat and a trangia the one on the left needs two rods to hold cup so it don't block the holes them holes with v cut is to let the flame come a little bit or it will not burn right the one one the right the punch on wrong side but still can be used with a diff. pot set up ps you need them holes at the top to get a good up draft to big holes on the back side are to low for a alcohol stove them holes makes a down draft with alcohol stove with the hex esbit tox they are above the fuel so you get a up draft with these tabs

 

[atross]

just found this as I am finding the gel not so great. It may just do the trick

http://backpackinglight.co.uk/product129.asp

 

[British Red]

There was a fairly large buy on those run by outdoorcode. IIRC feedback wasn't very positive

Agree on the "fire snot" though - utter rubbish!

Red

 

[Graham_S]

i tried out a triad stove and compared it to a photon stove.
photon is cheaper, lighter, and boils water faster.
the triad stove had a nasty habit of flaring up dangerously if it's nudged while cooking.
i didn't rate it at all.