I would be grateful if someone could tell me. I attached a 250cp nipple, needle, and mantle to an old 300cp Petromax lantern. Because I can't get a 300cp nipple. I opened the distance between the nipple and the j-tube by the distance marked 250cp on another Petromax accessory. This way the mantle doesn't catch fire, but it only glows bright enough to slightly see the mesh of the mantle. I'm trying to increase the distance between the tube and nipple, thinking that maybe there isn't enough air, but if I open it too much, the mixed gas doesn't get in properly, and it's hard to light. I've checked to see if there are any leaks by submerging it in water. Also, the nipple is not worn out. Is the distance between the tube and nipple wrong? Does anyone know the correct distance for the 250? Or if I adjust the spacing between the 250 nipple, mantle and tube on a 300cp lantern, will it be so bright that the mesh of the mantle is obscured? Thanks.
The norminal distance between the top of the jet or nipple and inlet of the J-mixer tube is 12.2mm, perhaps +/-0.5mm on a 200/250cp Petromax. You can vary this to suit the specific needs of your lantern. However, I believe the main problem isn't the gap distance on this lantern. The 300/350HK Petromax has a J-tube which is bigger and longer than that on the 250cp version. By using a 250cp jet/nipple on a 300/350cp Petromax, there might be an issue of the fuel-air mixture not getting 'fully-delivered' to the ceramic burner. It might also tend to back-burn into the J-tube. This will cause the mantle to glow dimly. Try to also reduce the gap below 12,2mm and see the response/result of the glow or flame. It might not be easy to optimize this. At the same time, use a much higher fount pressure for this. Say around 3 to 3.5bar. (The resulting heat using a 250cp jet would be very much reduced or dissipated, especially in a large 300cp lantern. You would want to get the lantern to burn as hot as possible).
***note: increasing the gap distance on this one will only make the fuel-air mix leaner and at the same time, reduces the mixture's overall flow velocity further. This will make it hard to light or might not light up at all. The 250cp jet needs a shorter J-tube between the inlet and the burner for optimum results.
@MYN Thank you. I learned a lot from this. I will check the distance when I get home. If you know, please let me know. How far is 300cp supposed to be?
@MYN I just tried changing it to 12.2mm while keeping the 250cp, and it's brighter than before the change. Thank you. It looks like I can get 300cp from another manufacturer, so I'll try 300cp nipples as well. Thank you for all your advice.
