Hi all, Got a bit of a pulsing/ flaring up (vapouriser not staying hot enough?) type problem with my 1550, i stripped it down and pressure tested under water which showed a leaking NRV so replaced that, there is plenty of fuel in the tank, 70-80 full strokes of the pump as per the instructions, 50 seconds with the quick lighter and it starts fine and runs brightly for a few seconds, i tried it first with a smaller 500 cp mantle (which ran better for slightly longer) and have just tried it with a longer 500-600 cp mantle to see if it heated the vapouriser better, i haven't removed the vapouriser as yet i just wondered if anyone had come across this before i do, Thanks.
All pressure lamps hunt to a certain degree. Sometimes it is a slow beat but mostly it is fast enough that you can't see or hear it. It is a result of the back pressure effect caused by flashing a liquid to gas in the generator. To some extent this is reduced by having a restriction in the fuel feed but that does not always control the effect you can see. It is also affected by pressure. It will speed up if you increase pressure but sometimes not enough to make it fast enough to cease. Flaring suggests lack of heat in the generator and with an Optimus the first fettle is to make sure the Preston loop is clear. Optimus seem to be affected by carboned loops more than other makes. A possible cure is to wind some fine brass mesh around the pricker rod in the lower part of the generator which will help heat transfer and also effect a more effective back pressure restriction. ::Neil::
Ok thanks Neil, a strip down and clean is in order first then, i've not done one before so i'll have to read up on it.
Well i cleaned the loop by heating and quenching a few times and managed to get a couple of strands of wire through it, it was running a lot better and was very bright and in twenty minutes of use it started and stopped pulsing five times for approximately ten seconds at a time, starting slowly and then speeding back up to normal, then it started pulsing more frequently, the gauge is showing plenty of pressure, well past the red line and pumping when pulsing has no effect, there is still plenty of fuel in the tank?
As said by Neil, wind some brass gauze around the pricker rod in the lower part of the generator Brass Gauze - Accessories - Petromax HK/CP500 - Petromax Lamps - Lamps & Lanterns Pelam
Thanks, is this any good? FINE BRASS MESH WOVEN WIRE - FILTER OIL BARGAIN - A5 Sheet 150 x 210mm | eBay How wide should i make the gauze?
Thanks Sellig, i'll get some ordered and have a go, it won't harm fitting some either way it was just a bit strange it ran fine for a while and then started pulsing, i thought that the loop may have blocked up again, i'll check when i get a chance.
Well i tried to clean the loop again, i'm not sure if there is a lip on the inside of the lower part of it but i got the wire near to the end it just wouldn't come out into the straight part, i fitted some gauze near the base of the generator and its still pulsing, it was running ok to start with then got slightly dimmer so i cleared the jet with the pricker and then it started to pulse again but quite quickly this time, not sure if the pressure gauge is accurate but i must of given it eighty pumps, showing three quarters on the gauge, it eventually blew the mantle in half, i made the brass gauze 3in long and 1in high, is that sufficient or does it need to be taller?
On some of my lamps, I put gauze on the whole height, on others only 3/4 of the height. Each lamp is different, and we must adapt the settings. It's still pulsing, so try taller to the full lenght.
Well that seems to have sorted it, i wrapped the full length in brass gauze and cleaned the base of the pricker for good measure as it was a bit coked up and its been running nicely for half an hour now, i should of remembered i had the same problem with a Coleman 214 except on that one i made a new brass spring for it, anyway thanks for the help Neil and Sellig
Yes Gilles very good news, its always nice to fix a badly running lamp, i've also ordered another sheet of the gauze for the stores department just in case, all i need now is a pair of sun glasses to protect my eyes from the lamp Thanks again.
Odd really as manufacturers mostly sold lamps that worked (other than Veritas of course but let's not go there) so we shouldn't have to fiddle with generators and such to make them run right. Kinda suggests a deterioration somewhere in these old lamps we play with. I suppose the parts must wear with use and maybe that is the root cause of most running problems. ::Neil::
Don't say that, i've got three Veritas 350's to fettle at some point, You wouldn't think much could go wrong with this type of generator would you but as you say these lamps are deteriorating all the time, some are getting on a fair bit now aren't they.
I am told they can make serviceable bird feeders. Some of them can actually be persuaded to make light but they are the exception. So fettle away and prove me wrong. I would personally prefer to fettle Tilley X246Bs and I think they are borderline 'Orrible. ::Neil::
Yes i've made a few X246B's make light that didn't really feel like it, i've got a chromed 350 that looks unfired but is missing a few parts and the others are in good to average condition, only one has an original globe, i may clean them up and pass them on as they are if they are meant to be that bad then!
Oh no don't do that. Make them run and make your own mind up. I really shouldn't say things like that. I mean they are pressure lamps which is the stuff wot we collect and someone has to love them. Just not me though. ::Neil::
Hi all, I also have a Optimus 500cp, well two actually, not perfect, but they are for use and not collecting, you know, sea fishing, power cuts all that, I was reading this post and thought, I have one just like that, a lamp that whatever I did I could not stop the Pulsing /chuffing, I started the process of placing the brass gauze in the vaporiser tube, but it just did not sit right with me, it was a work around and not a fix. So I sat down for a while and thought and thought and thought, what can be the real problem here, well it was not the Vaporiser, the adjustment on the Mixer tube, the gas chamber or the nozzle, although I am running Stainless steel nozzels and framed double tied mantles on both my lamps, one always performs perfectly and one pulses, like crazy. I have a background of Mechanics, Petrol Engines Mainly, so I started to draw parallels between the lamps and the small engines I have worked on in the past, and one thing kept coming back to me, the old SU carbs and the Spring outside of the throttle slide, if you are aware of the old SU carbs they had a Oil damper, down the middle and the spring that closed the throttle, but if there was too little oil or the spring was weak or damaged, the engine ran like a pig. I will stop waffling now, and get on with it, at the bottom of the Vaporiser lower part (the Pick up Tube), some call this the carburettor, there is a small valve, a rubber seal in a brass plunger and a small spring, I dismantled the lower section, (Carefully, as I had already snapped one before because I did not support the pipe nut when trying to unscrew the valve section). I replaced the internal spring with one a tiny bit longer and a little thicker, not going crazy, well after fitting all of the lamp back together and adjusting the mixing tube to jet height to 14.5 mm, I started the lamp, after a little warming up the lamp really burst into life, a crisp white light that it had never given before, and no pulsing, I have wasted about ten mantles on this lamp, so I was very happy, if I turned the lamp up too high it pulsed or down it went dim so it appeared to be running correct, I left it running for over an hour, pretty chuffed me not the lamp. I do hope this helps anyone else with this problem. you may just be able to stretch the original spring, to test this out and then source a new one at a later date, I was lucky I had some in my gear. Regards Duncan
G'day @Duncan Burt and welcome to CPL. The more information the better so thanks for your contribution.
The brass gauze or copper wire coil are likely to cure the pulsing problem. But then, as Neil said, we shouldn't need to fiddle with the generators as the manufacturers made them to run without noticeable pulsing. So, if anyone has a brand new generator and jet, use them on the lantern and see whether it cures the problem without the gauze or anything else. That'll prove that some wear or deterioration had taken place in the old unit.
Can I throw another thought into the pot, I may be wrong, but I believe the gauze or wire helps to stabilise the fuel column, (the fuel inside the generator) in turn dampening the pulsing, by stopping the fuel from moving freely, up and down the generator, like the sponge they use in racing vehicles to stop the fuel from moving around inside a racing fuel tank. Any further thoughts? Regards Duncan
A reasonable analogy but I wouldn't go quite as far as to say that. Certainly the gauze, wire or other packing helps to reduce back-pressure and thus the amplitude of the pulsing. Because there's an overall pressure gradient from the tank to the atmosphere, then there's a nett flow of fuel from the tank through the vapouriser and burner to the mantle. The frequency of the pulsing will be determined by this pressure differential - as long as that's sufficient, then the frequency of the pulsing will be greater than the eye can detect. Thus, together, the amplitude and frequency of the pulsing are such that the eye perceives steady light. That's how I visualise it, anyway...
Just an update, I took the Offending lamp Optimus 500cp fishing the other day, and to put it mildly, it was a disaster, the lamp proved to be unreliable and performed very badly, so after a miserable dark night fishing, I decided to strip the offending item down and match its adjustments to my other Optimus that always works great. On close inspection the Air gap from the top of the jet to the mixing tube was the same 14.2 mm, (Using a Vernier calliper) there was one thing that did stand out, or "up" in this case, it was the height of the Needle, on the reliable lamp, in the closed position, it sat 5.6mm above the Vaporiser upper, with the Jet removed (so from the tip of the jet to the top of the vaporiser it measured 5.6 mm) on the problem lamp it measured 7.8 mm, the needle stuck out the jet about 2 mm, when the lamp was turned off, so I decided I would match the settings of the good lamp, on the poor lamp, after much fiddling around I managed to match the 5.6 mm height, I cleaned the jet with a Primus Pricker, and put the lamp back together. I used the spirit preheat bowl in the lamp and allowed the lamp to preheat till the meths had almost boiled off, the lamp lit almost immediately, after a couple of seconds with a strong white light, it appears to work the same as the other reliable lamp now, but I will let you know after its been on the beach for a night. (Just out of interest, none of the fittings were loose, the Needle, the jet etc, but I did clean the jet and adjust the tip of the needle downwards, I assume to clear the fuel path) I could not find a measurement or adjustment guide for this part of the lamp, but I thought I would update my previous post, just in case it could help others. Regards Duncan
I was also very successful with stainless steel mesh, that I cut out from ultra fine in-line water filters.
