Late 70s Optimus 00

IvanN · Aug 25, 2020

This is my first 00 bought new in the late 70s. It’s been my favorite ever since.

Haggis · Aug 25, 2020

An old and faithful friend

The Warrior · Aug 25, 2020

Nice Ivan. I'll bet you've created some fond memories with it. The 00 is a helluva nice stove.

Tony Press · Aug 26, 2020

Good piece of kit, Ivan.

Cheers

Tony

Sternenlicht · Aug 26, 2020

Nice kit!
I have an Optimus 00 from the swedish military which looks exactly the same, so I think it has a similar age.
I cannot push the pump shaft into the pump tube, if I do, it directly comes out a few centimeters. The pump shaft of your 00 also is not completely pushed in, is it the same with your stove?

Ciao, Bastian

kerophile · Aug 26, 2020

Hi @Sternenlicht please see comments on reasons for rising pump shafts:

kerophile said: ↑

Hi, @Metropolitantrout and others.

This thread describes how the majority of air pumps on classic stoves work:

Typical pump assembly

The NRV valve opens at about 10psi pressure, and allows air to enter the tank.The pump has to overcome this 10psi, plus any existing pressure in the tank. At the start of pumping this is only the hydrostatic head of the kerosene in the tank. However, as you keep pumping the back-pressure becomes greater. The 10psi NRV pressure setting, at rest, is really there to stop kerosene flowing back into the pump cylinder.

1. The pump does not fully empty the air cylinder on each stroke as the piston cannot get to the bottom of the cylinder. The head of the NRV protrudes from the base of the cylinder and the piston itself is fitted with a downward-facing pump bucket.

2. When you stop pumping, the pressure of this pocket of air remaining in the cylinder will be the same as the tank pressure so could be around 2 bar, or approx. 28 psi. This back- pressure will cause the piston to rise, as you have observed, until pressure in the trapped volume equalises to atmospheric pressure. The piston will typically rise an inch (25mm) or so and then stop.

3. The better the quality of the pump and pump leather, the better the seal, so a rising piston indicates a pump in good condition.

4. If you want to avoid a rising piston just give the pump rod a “wiggle” from side to side, at the bottom of the pump stoke, when you finish pumping. This usually allows the trapped volume of air to leak past the piston assembly, equalising pressure.

NOTE. The above remarks apply ONLY to a pump in good condition, with a non-return valve (NRV) which is operating as intended, and not allowing fuel to leak back into the air cylinder.

If the NRV is leaking and fuel enters the cylinder, the piston can be pushed all the way to the top of the cylinder, and leak fuel out of the pump cap. THIS CAN BE VERY DANGEROUS AS THE FUEL MAY IGNITE AND BURN.

IF YOU SEE A PUMP ROD RISING OUT OF ITS CYLINDER, MORE THAN AN INCH OR SO, AND CONTINUING TO RISE, RELEASE TANK PRESSURE IMMEDIATELY USING THE AIR-RELEASE VALVE, AND ENSURE THE BURNER IS EXTINGUISHED.

Trust this helps.
Best Regards,
Kerophile.
Click to expand...

Sternenlicht · Aug 26, 2020

@kerophile
thank you very much!!

Ciao, Bastian

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