Working on a 1938 Petromax 828 (Rapid)

Today l also worked on a Petromax 827 with a "Drehrapid".And I noticed that it is very important that there is not too much fuel in the tank.

 

Too much fuel will risk having the liquid fuel become ingested into the air circuit of the atomizer making the torch shoot and spill liquid fuel instead of a fine mist. Too much fuel also means you'll lose pressure quickly making the rapid torch go out due to less air.

 

@Reinhard
I don’t see that instruction regarding fuel level in the extracts you’ve reproduced/translated.

 

The instruction is a personal experience of mine that I had this afternoon and only has something to do with the advertising paper in a broader sense.

 

Since the patent DE645164 for the E&H drehrapid under the Deutsche Reich is in German, I suppose not everyone would be able to understand the contents well. Just for interest, I have attached both the original and a later US patent version that was based on the earlier German patent here.
Although they aren't exactly the same but these are what I have in my files:

 

Actually, the latter US2279924A patent does not correspond to the German patent DE645164.
It is instead, a US patent that was based on the German patent DE678687C.
The inventor at E&H Aktiengesellschaft, Max Marowsky had actually continued to make some improvements to address some shortcomings on the preheater design of the original DE645164 patent. This had resulted in the later DE678867C and US2279924A patents.

The translated (English) version of the original DE645164 can be found here:
DE645164C - Pre-heater for lighting and heating devices fed with liquid fuels under air pressure - Google Patents

 

Typo: not E&H but E&G.

 

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

Apropos of our earlier conversation about the gap between the two lower hex components of the “drehrapid” (parts #14 and #15), I discovered a 1mm thick paper or fibre washer at this join very on my Petromax 882:






Interesting…


Cheers

Tony

 

Interesting indeed Tony.

John

 

Now that is interesting. Is it supposed to be present at that position?

 

No, never seen that.

 

I've never seen that too. Maybe a solution to overcome problems with leaking when the metal rim inside is not sealing properly any more.

 

I would first remove the feed tube carefully,
then polish the rim of the tank part with steel wool and depending on damage lay a fine line of soft solder on top. Smooth that out with fine sandpaper. I don't think the part would get that hot that the solder would melt but if then use hard solder. With the upper part as a counter part you can see marks on the solder and smooth it out. At a certain point you will have a perfect seal again.
I learned that metal seals start to wear on each other so that you can't change parts.

 

Re-reading my last night’s post, I thought I should make it a bit clearer where the washer was found:








Cheers

Tony

 

I think I have understood your description correctly. The point where the gasket was inserted is where an air leak can/could be repaired, even if the contact surface of the actual gasket (brass) is damaged.
I have also tried the same thing with some PTFE tape in the thread, but the success was not so good. In the end, only replacing the defective lower part of the preheater helped.
Please mind that even the slightest leak at this point leads to a gradual loss of pressure, which drastically restricts the lantern's operability (as do hardened seals in the newer Rapid preheater designs).

 

Thanks, Martin.

I'm having fun gradually working through these "drehrapids".


Cheers

Tony

 

I'd be curious to know why the previous owner had inserted the fibre washer there.
Was it because there had been a leak or was it for some other purposes.
Perhaps you could ascertain by testing it both with and without a fibre washer.
If there's a leak, perhaps many alternative sealants could also be used.

 

Coming back to this discussion of the “drehrapid” Petromax pre-heater on the early Optimus “Rapid” lamps and lanterns.

As I was working on the Petromax 827 that is the subject of this thread (and now posted in the Reference Gallery here), I thought “what if I drilled holes around the base of the Rapid flame protector tube? Would that allow more air into the mix and make the flame bluer?”

I didn’t do it as I thought I’d try it on my next “drehrapid” which is a Px 882.

But… as I was going through my spares I opened a new flame protector tube, and low and behold:





It has a row of holes all the way around.

When I fettle my 882 I’ll test this and compare it to an old one without holes.

Stay tuned (for a while, as I’ve got another Petromax project to do first).

Cheers

Tony

 

I believe opening more inlet holes around the base of the flame tube can only help to a certain extent.
How much air being drawn in through the openings depends strongly on the velocity of the fuel-air stream leaving the Drehrapid's jet orifice.
This is in turn dependant on both the operating pressure and the size of the jet orifice.
A smaller orifice creates a discharge stream with a higher velocity. High discharge velocities would help create a lower pressure zone around the tube's air inlet hole(s) to draw in more air.