Working on a 1938 Petromax 828 (Rapid)

Part 1

This is the first Petromax Rapid that I've brought back to life from a non-working condition. Note that it has a "Cat Brand" hood (vent) that it came with.

The very first thing I did was to read through Jan Moeller's guide to restoring a Petromax 826 (attached to this thread below).


As it came:






1. The plastic lens in the manometer was cracked and ruined, so I fixed that first.




The lens taken out.



I used some mica to cut a new lens, having found out that the standard plastic replacement lens does not fit this old manometer.



When fitted to the tank with a new washer, the manometer appeared to work properly so I left it with just the lens repair.





Next, I pulled down the lantern to its component parts following the method attached below.


2. The Rapid preheater.

The preheater was removed and disassembled:



The air and fuel jets were cleared with very fine tapered needles. The needle for the very small air holes was 0.12mm.




The needle for the very small air holes was 0.12mm.

Before reassembling the Rapid I cleared the fuel pickup tube with compressed air. The flame tube for the rapid was somewhat crushed at the top and distorted so I used the taper on a hole punch to straighten it out.




3. The vapouriser.

First I took off the Preston loop vapouriser, and carefully unscrewed the pricker (with the Petromax pricker tool).



I then unscrewed lower vapouriser components from the tank noting the number of full turns it took.





I then disassembled the control shaft from the lower vapouriser; cleaned all the parts and laid them out for reassembly.



Note that I replaced the bottom washer and brass cup with a new part. New cup and washer on left.





4. The lantern came without an NRV in the bottom of the pump tube, and no pump cup holders on the end of the pump tube. I used an NRV from a Solar lantern, and modified the thread of its cup cup holders, and fitted a new Petromax pump cup.







5. I disassembled and cleaned all the components of the burner.



I used a high pressure hose to clean up the burner inner casing.





NOTE: The Petromax spanner with the gap measurer for the vapouriser/burner is very useful, as is the Petromax pricker tool. the washers, tools etc for this and my line up of other Petromaxes were supplied by The Base Camp (UK).


/Part 2 to follow...

 

Part 2

Re-assembling...

New lead washers.


Fitting the rapid components.







Fitting the lower portion of the vapouriser.




Fitting the conducting rod and excenter.



Fitting the Preston loop vapouriser.




Fitting the cage bottom plate.




Checking the pricker needle.



Assembled inner casing.




Testing

The lantern was first tested using a Tilley wick pre-heater.



Next, the rapid preheater was tested. After re-cleaning it, it is still a little over-rich, but does not soot up the glass on use. I will return to this rapid pre-heater after servicing a few more.





Up and running.






Thanks to all who gave me advice on this fettle. I'm happy to receive more advice and corrections etc.


Cheers

Tony

 

Well done Tony. Now that you've done it, it's not that hard to service a Px or Px style lamp.

One thing I did notice is that it has an Aladdin 1A flame spreader. The original must have broken at some stage and this is what they used to get it working.

 

Well spotted, @Nils Stephenson.

I’ll check what’s in the shed (when it gets above zero here) and see what Petromax parts there are. I may even have a new one in my spares (I know I have a new ceramic).

Cheers

Tony

 

@Tony Press

Nice to see there is also a Petromax with "Drehrapid" in Australia that has been brought back to life

 

@Reinhard

I have a couple more “drehrapids” to do (all found in Oz.).


Cheers

Tony

 

@Tony Press
I’m enjoying drawing comparisons with my Aladdin Petromax 828 of the same era Tony.

Fresh from fettling a couple of those Tillite pre-heaters you sent me with the consequent research into spray nozzle theory I’m inclined to use different terminology from the ‘rich’ mixture usage we’re familiar with in respect of vapourised fuel in burners.

With a pre-heater it’s droplet size and their velocity and that of the air that surrounds them when they are ignited on emerging from the pre-heater jet outlet that affects the colour of the flame. Those variables are in turn influenced by the characteristics of the air/fuel mixing arrangements within the spray nozzle and the consequent air velocity and angle at which it impacts on the fuel emerging from the internal jet. The Tillite instructions mention that if air pressure is allowed to drop too much during pre-heat, flame colour will become more yellow, so air (and fuel) pressures are factors too.

My pre-heater for the Aladdin Petromax has the same flame characteristics as yours, with no soot deposits on mantle or glass.



Your example and mine are too small a sample to confidently say, “They all do that” but the outer jet orifice measures a modest 0.18mm and the internal air and fuel outlets are unworn, so I suspect the device is close to its design specification.



John

 

I also have two Petromax Lanterns with that kind of preheater (an Aladdin Petromax 828E and a "normal" 828), and both of them perform that same way. I also guess that the fuel droplets are a bit larger than those from the more modern Rapid preheaters due to the construction with the outer needle valve part.
The small droplets produced inside could combine again in the valve and the duct by deposition on the walls to form larger droplets and thus produce the yellowish flame pattern.

 

@Martin K.

Then how do the Col-max and 238B rapids burn clean? They have a similar twist knob design. I own one and it's mostly a blue flame.

 

Unfortunately I don't have any of these. My only observation is that this type of "Drehrapid" Petromax preheater always seems to burn a little yellowish. Perhaps not yet fully developed. I also don't understand the need for the outer nozzle cap with this kind of construction.

<edit> It came to my mind that I have a third one of that kind, I'll test it on occasion.

 

It looks like you done a great job restoring that lantern back to 'life'.
Only the drehrapid eheater might still improve with some further touch ups.
You can examine the cross sectional diagram as I have mentioned in your other post.
Unlike the later preheaters, this one has a relatively long fuel-air path, #17 after the valve:-


Besides the size of air holes, #13, the amount of air entering to mix with the fuel would be determined by the tiny gap between the hollow cone, #16 and the cone, #9.
If in any instance, the preheater upper valve block part, #15 had been screwed down so much as to cause the sealing part, #14 to get compressed too much, then the gap between #16 and #9 would be effectively narrowed below its ideal point. In such a way, the amount of air would reduce below adequate.
It might not be due to what I've described here but you check if anything changes by slightly unscrewing part #15 so that the gap between #16 and #9 widens a tiny bit more.
The orifice on the outer cap, #18 only serves to limit the amount of fuel-air and to increase the discharge velocity further. This might assist to improve the Bernouli effect to draw more air near the tube/shroud's(#22) air inlet(lighting hole) #23.

 

Slightly unscrewing the metal-to-metal seal will immediately cause an air leak and could only be done for testing the preheater. For a permanent repair, a thin paper gasket would probably have to be inserted to increase the gap slightly.

 

Exactly, Martin and @MYN

Fuel and air collide at the point of the green arrow and the whole length of the passage circled in red allows some merging of droplets, like drops of rain on a window combining as they trickle down.



An Optimus pre-heater with different internal anatomy burns more cleanly.

 

Indeed, MartinK and Prescall.
In addition, I do notice that there's no longer a gap between parts #15 and #8:-


That could mean that the gap between #16 and #9 is now narrower that what was originally intended.
If slightly unscrewing part #15 is necessary, you'd need to ensure sealing by some means as mentioned by MartinK.
There isn't very much thread left to be unscrewed. Only a very slight turn.

 

Well fettled and well posted!

 

You can replace the lower part of the rotating rapid with a new connector #224 with suction pipe and filter.Then the rapid works as it should, powerful with a blue flame.Visually ,this is hardly noticeable .

 

This would be an indication for @MYN 's thesis that the distance between the lower and centre part is decreasing, possibly due to frequent dismounting and remounting

 

Interesting @Reinhard

@MYN I think the mating surfaces between those components are internally as the patent drawing suggests and not the surfaces I’ve indicated. If that’s the case, the width of the air passages are set by the factory.




I’d need to take a closer look at the pre-heater to confirm that however.

@Tony Press I may have initiated the discussion on this sub-topic of the pre-heater but trust you’re in agreement it’s relevant to fathoming the identical performance of our pre-heaters!

Personally, I’m not unhappy with the partially-blue flame. Unlike a rich mixture of vapourised fuel no soot is generated by the burning of the atomised fuel droplets. I see it as comparable to the yellow and blue flames seen in burning alcohol in a priming cup or burner. Not aesthetically as we’d wish perhaps but of no consequence.

 

Great discussion, @presscall, @Martin K. , @Dashwood, @MYN , @Reinhard

Thank you.

As noted above, I’ll work though my other “drehrapids” carefully, and then return to this one. I’ll be paying attention to the relevant surfaces and gaps.

Cheers

Tony

 

I find the slightly rich yellow flames to be more striking for those watching, great conversation starters.

 

I would believe so, @presscall .
Part #15 would stop screwing in further once its internal bottom has reached and tightly sitting at position #14.

 

Hi,
1.

- my 238B rapid does not burn clean blue flame: Coleman 238B, Belgian military set
2. Attached photo of completely disassembled old 828 Rapid, rapid intake tubes etc.
3. This particular example has damaged (cracked) part 221 - nipple for Rapid. I compared with later nipples (1940, 1963, 2020) and later parts are different - longer.
4. The bottom washers are quite easy to make out of some big 3mm thick washer or Viton sheet.
5. I see that my lamp has different (ribbed/reinforced) generator upper part

 

@Piotrek

Interesting, mine burns a nice blue flame with very little yellow.

 

Here are my other two "drehrapids" that I'll take my time restoring:











Cheers

Tony

 

It could be either you've been fortunate enough to find one that works just about perfectly or its due to the design difference between the E&H drehrapid and that of the Coleman 238B atomizer.

There is a particular aspect of the 238B atomizer design that is markly different from that of the E&H drehrapid. Other sections are in principle, almost similar.
In the 238B's atomizer, there is an obvious and deliberate construction of an atomizing chamber, #52:-



If you read through the actual patent carefully, you'd find that the exact manner in which the atomizing air interacts with the fuel is different: "...impinge against the surface 23 to be diverted laterally at right angles into the atomizing chamber 52 and across the jet of liquid fuel discharged through the orifice 49,...".
My intuition would lean towards this resulting in a more effective breakup and atomizing of the fuel prior to further mixing in the channel/port #24.
As to whether this would actually result in a cleaner burn remains to be further examined or evaluated.
The 238B atomizer Coleman patent was filed by the inventor, Mr. Boyd W. Tullis on a later date than the E&H drehrapid patent.
I'm not sure if he had already made certain improvements based on the Petromax drehrapid or was it an entirely independent invention.
You can certainly tell from his various patents that Mr. Tullis was indeed a brilliant person...the Coleman 242, etc.

 

@MYN

Infact the rapid on my 238B burns so clean and hot that the tube it emits from starts to dull glow red after 10 seconds.

A thing to note if you're servicing these Coleman rapid torches is the seperate atomizing jet part #55 I think, one can easily mistake and install it upside down and possibly have a rich sooty burn as the incorrectly installed jet isn't atomizing properly. Luckily I didn't make such mistake as I took pictures and cataloged every thing where it goes along with the documentation such as the one you shared.

I saw another 238B owner who demonstrated their rapid and it was burning very rich.

 

@Dashwood ,
The separate cylindrical tip piece, #55 needs to be installed correctly. That's because it has a thinner section at the top where the tiny orifice, #60 is located.
This orifice was intended to create a fine jet of atomized fuel-air mixture at high velocity. The high velocity is necessary to create sufficient 'Bunsen' effect of drawing in more combustion air via the lighting port, #38 or from any other holes(if present) located around the lower periphery of the preheater's mixing tube/nozzle, #16.

It(part #55) won't do well if installed upside down.

 

This also explains the necessity of the outer nozzle on the Petromax Drehrapids

 

@Martin K.

It's also not exclusive to the drehrapids but to all blow torch designs that are naturally aspirated. Exceptions are torches that have their own oxygen supply like for cutting and welding.

The venturi effect is critical to feeding the flames the air it needs.

 

Yes. While the outer nozzle isn't a critical part on the Coleman 238B's atomizer, it is important for the Petromax drehrapid. That's another design difference.