# Butane gas filler



## colin (Jan 9, 2010)

Can any one help with a sketch of a butane gas filler I need to make a special one for a neighbour. He tells me they are brass and screw onto a butane gas bottle and are used to fill gas fired models. 

Thanks :bow:


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## Blogwitch (Jan 9, 2010)

Colin,

I have been asked to make these a few times by model boat men in my area.

If you download the Bruce engineering catalogue from here, and have a good look thru it, you will find that they are only 12 squid 50p each.

http://www.pollymodelengineering.co.uk/sections/bruce-engineering/docs/cat_oct08a.pdf

I can strip my one down for you and let you have a look, but when you see what needs to be done, they are just not worth making.

The difficult part is cutting the internal roundish formed thread that screws onto the can, then you have to obtain the flat seal that goes inside and a tiny circlip that holds it all together, plus deep drilling the nozzle end with something like a 1mm drill.

This is definitely one of those jobs that is easier to tell him that you can't obtain the threading tap to fit, and to buy one specially made would cost him an arm and a leg.

If you still want to go ahead, for what will most probably be a 'thank you' job, just ask and I will strip mine down and measure it up for you.

I have done a quickie C-o-C to show you what is involved.

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## shred (Jan 9, 2010)

In the US these adapters can sometimes be found at camping stores or amongst the 'Airsoft' crowd if you know anybody into that.

Update: the one I have is from Brunton: the "Brunton Fuel Tool".  If a different delivery is needed, it appears to be plated brass, so an adapter could probably be soldered on. (The wire over the top is just a flip-down guard.)


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## Blogwitch (Jan 11, 2010)

Colin,

As promised, here is what mine looks like, sorry for the quality of the pics. 
As discussed privately, I looked at the quickie ones I used to make, and I'm sorry, because of the length of the extension you require, it would just be too unstable to hold and put pressure on the nozzle at the same time.

This is what one looks like when fitted to a standard UK butane/propane can. This is a standard can for gas blowtorches, and I use the adapter for refilling my small gas blowtorches, and the odd occasion when I top up my cigarette lighter.







This bad shot shows the large o-ring, that could be a thick rubber washer, protruding a little more across the flat face at the bottom of the hole, as all it does is seal the can to the adapter. A washer of 12.5mm diameter with a 7 or 8mm hole in it by 1.5mm thick would do the same job. It looks to be a standard nitrile rubber o-ring, so the same sort of material for the washer. BTW, if making the washer type instead of the o-ring, I would make the firing pin say 1mm longer, to allow for less depth on screwing together.







This is it stripped down, my small o-ring split when getting it apart, and seems to be made of silicone. A dot of superglue and it went back as good as new.
The circlip does really need to be on there, or some sort of stop (maybe a small collar with a grub screw). It prevents the adapter falling apart and also prevents the firing pin being pushed too far into the can valve.







You can see how much of the rolled thread is sticking above can top. It was very difficult to get a good measurement from it. It is either 26TPI (imp) or 1mm pitch (metric), both very similar in size. If it was me, I would go for the metric pitch. Just internal single point until the can thread fits. I have given the thread tip diameter on the sketch, just go in very gently from that.







Now we come to the C-o-C's. I have forgotten a measurement on this first one, where the small o-ring fits, in the 2mm wide groove, the centre measurement should be about 3.2mm diameter or a tiny bit less, but no smaller than 3mm. That forces the o-ring to expand slightly and forms a seal inside the cap bore.
You have to be aware that this valve has been used continuously for the last 20 years or so, so the measurements might show a bit low in places because of wear. Rounding them up a bit shouldn't cause too much of a problem, just remember that this has to slide up and down inside the cap.
From certain suppliers these can be bought up to 75mm long, you just have to make sure you have a drill bit long enough if you want one of that sort of length.
The open end that fits onto the Ronson filler valve on the gas tank to be recharged, I would put a small 90 deg chamfer into the end so that it locates nicely onto the valve.







Just another load of numbers on here for the cap.






If you notice any glaring mistakes or missing measurements, just ask and I will get them for you.


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## steamboatmodel (Jan 11, 2010)

I was chatting with Sandy of ACS about these threads and this is part of his reply,
"7/16" x 28tpi UNS
 It is one of the UNIFIED EXTRA FINE threads and is of 60deg form.
 One thing to be aware of, when boring for tapping size, is that it needs to be a larger bore than you would expect.... the threads are of a rolled form on the canisters and therefore they tend to come up a bit big in the root dia.
 I have found that the best tapping size is 0.410" dia..... this will give appropriate thread engagement which works for all canisters.
 Taps are available from www.TracyTools.com"
I hope this helps, I haven't tried threading for making a unit yet as I have been able to find small camping burners and torches that have this thread in the second hand stores. I also found one of the Brunton Fuel Tool for $2.
Regards,
Gerald.


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## Blogwitch (Jan 12, 2010)

There you go, straight from the man who knows. Cleared the problem up nicely. Nice one to Sandy.

Because it is a one off job, single pointing would be the way to go. If you are going to buy a tap, you may as well just go out and buy a new one of these, I don't suppose there would be a great difference in price.

Steamboat, what you are saying is correct if you are just transfering fuel thru a shutoff valve, you can use old screw on fittings, I've got loads of old fittings in my shop to do it that way, but this unit is a different kettle of fish. No knob twiddling or removing from the can at the end of the top up, just push onto the Ronson valve and fuel transfer beings, let go and it stops, just like filling a lighter from a can of gas. Change it over to a new cartridge when the old cartridge is empty.

There is a cheap and dirty method to obtain the same effect, but as explained to Colin, over a certain length, it becomes unstable due to trying to apply pressure to the Ronson valve and getting the liquid flowing, and keeping the two square to each other to prevent excess leakage. I suppose you could modify it to solve the problem, but you would be getting towards the original design, so you would just go for that one anyway.

See C-o-C.

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