Hi, this is my recently acquired No 70. I got it partly because I'd never seen such a simple device before and partly because it was so corroded, I thought it'd be a good demonstrator for electrolysis cleaning. It was £31 on ebay, but also came with 2 blowlamps, so maybe you could say £10. Does anyone know roughly what date it would be and more importantly, does anyone have any tips for unblocking the jet? I've tried heat and strands of wire, but no luck. I've cleaned quite a few blowlamps now with using electrolysis pretty successfully, especially in terms of effort. I use bicarbonate of soda, steel sacrificial electrodes and about 35 V and 2-4 A for about 2 hours. I then rub it with a stainless scourer and then use Silvo wadding. If people are interested I'll share more detail The tiny stove didn't sink like the blow lamps, so there's a bit that's not been cleaned, but it's a nice reminder of how bad it was. The flame diffuser, chain and cap are missing and the threads on the bell are so worn it just slots on. The meths dish was quite bent, but when i gently tried pushing it back to shape a bit fell off. The brass is so thin and worn, I think this stove has had a hard life. If anyone has any more info to share or point to regarding the no 70, I'd be interested to read it. Phill
@Phill Jackson For cleaning the jet in the nipple, you will need a fine pricker, about 0.2 mm (the jet should be 0.23 mm). Heat to very dull red, cool, prick, repeat. I wonder if the problem with the piece falling off your spirit dish was a result of zinc leaching from the thin brass during electrolysis? (Assuming it was brass, not steel - also the reason I avoid polish with ammonia on thin brass). Cheers Tony
sorry all, Phill, link i posted failed. operator error i expect. my bad i didnt check it. c.1926 -to- 1930,31 <-- there, that worked.
thanks for the info. i looked to buy some 0.2mm wire to make a pricker, but it was surprisingly cheaper to buy a pack of 0.2mm drill bits which have a little built in handle! I'll try to use it as a pricker rather than risk reaming out the jet. as for the brittleness, it's possible, but the one time i left a blowlamp in for many hours it turned orange as the zinc was removed, and this hasn't happened.
The 0.2mm drill bits arrived (for less than the cost of a bit of stainless wire) and with great care and only the smallest finger pressure I managed to work my way through the blockage and clear the jet... I then pulled the bit out too fast and snapped it! Luckily I managed to use another bit to poke it through. With a borrowed flame spreader I managed to get the stove going fairly easily. I don't think enough heat travels back down the stem because it kept going back to a yellow flame and needed a brief blast of blowlamp on the stem to get it back to blue again. The threads on the bell are almost completely worn away, so there's probably not very good thermal contact. I hadn't cleaned the corrosion off the bell and it gave a nice green flame for a while. It's not the most practical stove, but it was fun to get it working for its 100th (ish) birthday!
Well done Phill , If you're right about the insufficient thermal feedback you might try a flame spreader with more snug of a fit (akin to original form). I defer to others if that is not a primary suspect. I LOVE P70 /71s but re your "It's not the most practical stove,..." +1. What method will you use to extinguish /shutdown?
Hi Gilles, the drills were via ebay, lots of different sizes and combinations available. PCB Mini Drill Bits 0.2mm CNC Print Circuit Board Tungsten Steel Carbide x 10 | eBay UK
Hi OMC, and thanks! I just used some pliers to remove the flame spreader and it went out, i think the rush of vapours is just too fast without the spreader. I experimented trying to ignite the vapours using my propane blowtorch, but as soon as I moved it away it self extinguished. I then loosened the filler cap and left it to cool.
The shelter these came with would also help, the worse may be poor fitting, worn out parts for thermal feedback. Duane
You can wrap the threads with aluminum foil and then force the bell on to see if insufficient thermal feedback is the problem. I wouldn't suggest that as a permanent solution, though. ....Arch
