Restoration of a PETROMAX 829 lantern

http://www.dr-bommel.de   : Jan Moeller, Germany


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Rebuild instructions
Chapter 3 - New seals for generator and pump check valve
Chapter 4 - Re-assembly of Rapid pre-heater and generator (lower part)
Chapter 5 - Adjustment of the gen’s rod length, assembling of gen (upper part) and valve
Chapter 6 - Assembly of frame w. pre-heater cup
Chapter 7 - Putting heat shield and glass globe in place
Chapter 8 - Assembly of complete inner hood and fitting of mantle
Chapter 9 - Adjustment of mixing tube distance 


Chapter 3 - New seals for generator and pump check valve

Usually the rubber seals in the generator foot valve (#196) and the pump check valve (#10) are dry and totally hardened. If one doesn’t at least replace the pump check valve seal one can hardly operate the lantern safely because of kero leaking from the font into the pump body, thus flooding the body and also losing pressure.

An old, hardened seal in the generator foot (#193) must in any case be replaced if one wants to pre-heat the lantern with the Rapid pre-heater later. If one only wants to pre-heat using the little alcohol cup (#35) then it is not mandatory but again highly recommended for safety reasons.

The complete pump check valve is shown in pic. 6. The rubber seal (#17) needs to be replaced. The lead washer (#83) should also be replaced. However, if it doesn’t have too much deformation you can try to re-use it, but make sure it seals tightly and doesn’t leak.
In case of any lead washer make sure you turn the parts only clockwise to keep the lead washer tight. Never turn counter-clockwise again!

The most common problems are caused by a defective / leaky generator foot valve.
When the font is pressurized, the valve wheel points to the ‘closed’ position and one starts to pre-heat the gen with the Rapid pre-heater, then some fuel might rise in the gen and come out of the nozzle. This causes the lantern to catch fire with lots of smoke and soot. If that continues during the pre-heating time one has a perfect ‘inferno’.

pic 7 shows sections of the gen’s lower part (#153), the generator rod (#104) as well as the disassembled generator foot valve with the rubber seal (#193) and the valve spring (#194).

Everything fine so far?

All parts clean, straightened-out, worn-out parts replaced and seals at hand to start re-assembling?
OK, fine! Then let’s go for the next step.

Pic. 6: Pump check valve


Pic. 7: Generator foot valve

Chapter 4 - Re-assembly of Rapid pre-heater and generator (lower part)

In general, re-assembly of the whole lantern is done in the reverse sequence compared to disassembly.

We’ll start with the Rapid pre-heater.

First make sure the mesh (#187) at the lower end of the pick-up tube is clean. Otherwise replace.
Also clean the tiny channels in the Rapid nozzle (centre hole for kero, 2 outer holes for air). This is very important to get the Rapid running properly (see also pic. 42)..

The pre-heater body (#225) along with a new lead washer (#90) will be mounted first (pic. 8). Screw the part in until it sits tight and is properly adjusted. Don’t turn in reverse direction again in order to avoid the lead washer leaking.
Next, the lever (#223) is mounted onto the pre-heater body. The lever is to be secured with the nut (#222). Now the pre-heater nozzle (#221) must be screwed onto the pre-heater body. Then the flame pipe (#220) can be put onto the nozzle (One can also put the flame pipe on after assembly of the frame).

Most probably the rubber sealing part (#229, circled in pic.) has to be replaced as well as it is worn out or edges are damaged due to improper centering.


Pic. 8: Pre-heater body 


Pic. 9. Lever and nozzle 


Pic.10: Completed

Next is the re-assembly of generator (lower part).

First comes the gen’s lower part (#152) and a lead washer (#90). The lead washer gets between the font and the lower part as shown in the picture.

It might be helpful to first screw in the gen without the lead washer to check the number of turns. Then put the washer on and screw in. Again, make sure you turn only clockwise until the gen is in the right position to avoid leakages from the lead washer later.

The opening for the valve w. the valve wheel (#114) should then exactly point to the front (outwards). Only then can one assemble the frame easily and correctly later.

Pic. 11: Lower part of gen w. lead washer

Chapter 5 - Adjustment of the gen’s rod length, assembling of gen (upper part) and valve

In order to complete the re-installation of the generator, one now has to put the generator rod (#104) in place. The rod is to be inserted in the gen’s body and turned in a way, that the receiver (#103) for the valve shaft (#105) can be seen through the gen’s valve opening (pic. 12 valve assembly).

Now the valve shaft along with the hand wheel must be screwed in. In order to allow the little pin on the valve shaft to match the receiver (#103) one needs to push down the gen rod a little. If that was done properly, one can now move the rod up and down by turning the hand wheel.
Next the upper part of the gen (#152) is carefully slid over the gen rod. Tighten the gland nut of the upper part ‘hand-tight’ only for now.
Now take the thin gen needle (#68) and screw it into the gen rod, using the special tool (#119).
Finally insert the nozzle (#50) into the gen and tighten loosely.

Most important now is to check, how far the needle comes out of the gen’ nozzle when the valve is closed (arrow on the hand wheel points ‘up’). It’s best if the needle comes out between 0.5 – 1mm.
If it comes out considerably more or less, a re-adjustment is necessary.

If a re-adjustment is required, unscrew the gen’s nozzle again, followed by the needle. Next the gen’s upper part and the valve with hand wheel have to come out again.
The 2 halves of the generator rod need to be adjusted to a proper length so that the above mentioned measures (0.5-1mm) are reached. To achieve this, the little counter nut (#102) on the ‘reception part’ has to be loosened, the length adjusted and the nut pulled tight again (pic. 15 and
16).

When that step has been done successfully, all parts need to be re-assembled as described above. Now check all connections again and pull firmly tight in order to safely run the lantern and avoid leakages during later operation.
In the optimum case the needle looks out of the nozzle as shown in pic. Proper Adjustment.

If a proper result was not achieved in a first step, one unfortunately has to repeat the whole procedure until a convenient result is achieved.


Pic. 12: valve assembly 

Pic. 13: needle mounting 

Pic. 14: No proper adjustment

Pic. 15: Adjustment of rod’s length 

Pic. 16: Secure adjustment w. counter nut


Pic. 17: Proper adjustment


Chapter 6 - Assembly of frame w. pre-heater cup

Now it’s time to assemble the frame (#121).
Set the frame onto the font and adjust right. Put the centre bottom plate (#122) in the bottom of the frame and fix these parts using the centre bottom screw (#14). If the lantern isn’t already fitted with an alcohol pre-heater cup (#35) this is the time to add one. Just put in on top of the centre bottom plate and screw all parts together. You now have the options to pre-heat using the Rapid pre-heater or make a softer start with alcohol.

Pic. 18: Centre bottom plate, centre screw and pre-heater cup

Pic. 19: Completely assembled

Chapter 7 - Putting heat shield and glass globe in place

Now the glass globe (#74) can be set in. Optionally one can also add a heat shield (# 126). This heat shield protects the font from heat radiating down from the mantle. However, it is still possible to pre-heat the gen using the alcohol pre-heater cup, if desired.
There are descriptions in old ads that one can run a lantern with fitted heat shield for some more time even if the mantle is broken. However, I can’t recommend this as the glass globe is at risk. Replace a broken mantle as soon as you notice.

Pic. 20: Fitted heat shield and globe

Chapter 8 - Assembly of complete inner hood and fitting of mantle

The complete inner hood consists of the following parts: The inner hood (#117) itself, mixing tube (#33), mixing chamber (#34) and the ceramic burner (#3).
These three parts are adjusted and held in place by the clip (#20), screw (#21) and cross bar (#22).

The mantle is put on the ceramic burner above the lower rim and roughly fixed with one knot. Then the folds are distributed evenly, the knot is pulled tight and secured with a second knot. This ensures that the mantle will get an even form when burned. Now just cut the surplus strings off and you’re prepared(pic. 23).

Pic. 21: Burner parts 

Pic. 22: Fixation of mixing pipe Pic. 

23: Mantle on

 Chapter 9 - Adjustment of mixing tube distance 

The generation of best (kero-) gas / air mixture is ensured by the proper adjustment of the mixing tube distance. The inner hood must firmly sit on the frame before adjustment. The valve must be in the ‘open’ position (arrow pointing down) to avoid bending of the generator needle sticking out of the nozzle with the Petromax wrench (#66).

Loosen the screw (#21) a little with a flat screwdriver until the mixing tube can be moved up (see
pic. 24). Now place the Petromax wrench vertically on top of the nozzle and slide it in the ‘500CP’ position. Now lower the mixing chamber onto the wrench.
Pull the screw (#21) securely tight, check the distance again and the proper distance is adjusted and fixed. The optimum value for a 500cP lantern is 14.2mm.

Pic. 24: Inner hood details Pic. 

25: Adjusting the mixing tube distance

Congratulations again!
By now all the preparation work is pretty much done.

Now fill the font with max. one liter of clean, white kerosene. This ensures that the necessary space is left in the font for pressurizing. If the font is overfilled one has to pump again within a very short time to maintain required pressure.
When done, screw the pressure gauge set (#149) tightly on. Make sure the rubber gauge seal (#11) is there and it’s undamaged.

Pic. 26: Fill up with clean kero


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