[TheForge] New forge

Thu May 3 08:55:41 EDT 2012

Glad you're having better luck.  Remember that the orifice also
matters.  As Frosty points out, a longer orifice may give a better
laminar flow -- analogous to shooting a rifle rather than a pistol.
However, I've got quite good behavior from holes drilled in pipe walls
or pipe plugs.  Inspect the orifice to be sure it's clean and
burr-free, especially on the outside (i.e., where the propane
emerges).

Yes, do look into getting a regulator.  Like I said, some gas-grill
regulators can be modified to work.  (I've done it.) A valve alone
does not control pressure, only restriction.

If you're into electricity, it's rather like having a battery that
will lose voltage with time (or sometimes gain voltage if warmed), and
trying to control current with just a variable resistor.  Unless you
have a voltage regulator (analog to a pressure regulator) in the
circuit, the current (flow) will change as the voltage (propane
pressure) changes.  Since small propane tanks cool significantly
during use, this can be quite a nuisance.

In the case of propane, which never produces much pressure at the
tank, lack of a regulator is probably not a great safety concern.
(It's a different matter with a high-pressure -- e.g., 2400 psi --
cylinder.  Those should never be used without a regulator.)

As to flux in the forge -- it will destroy  mineral wool in no time,
and insulating firebrick only a little more slowly.  The answer is to
put a protective layer on the bottom.  You can use kiln shelf, if you
can get it, but the simplest is to cut a thin SS sheet to fit the
bottom of your forge -- and maybe a little up the sides -- and use
that whenever you use flux in the forge.

On Wed, May 2, 2012 at 7:17 PM, Geoff Nelson <gjn.pub at gmail.com> wrote:
> Thanks for the comments Bruce.
>
> I did a test yesterday evening with a 3/4 inch pipe on the Side arm by
> using a pipe nipple and reducer. Much better. I don't think I will get
> to welding heat in the current forge set-up. Not that I want to destroy
> the interior with flux. I don't use a regulator. I attach the burner
> directly to the propane tank and use the valve on the propane tank for
> controlling the flame.
>
> I need to work out a flare for the smaller burner tube to help with
> flame stability.
>
> I'll make a smaller forge specifically for welding Damascus billets.
> Made one once before form one hard fire brick and one insulating fire
> brick that were suitably carved out with an angle grinder and then
> placed together as a two brick forge. It worked very well for small
> billets as I could easily get welding heat out of it with a smaller
> burner. I think it could be a little more efficient than running the
> larger forge up at welding heat.
>
> I'll have a look around for an old regulator to see if I can do the
> modification and start working with a regulator.
>
> Geoff
>
> On 2/05/2012 9:35 PM, Bruce . wrote:
>> Geoff,
>>
>> Have you checked the available resources about burner design?
>> Here's one:  http://ronreil.abana.org/Forge1.shtml
>>
>> There's a book available (which I haven't read):
>> http://www.amazon.com/Gas-Burners-Forges-Furnaces-Kilns/dp/1879535203/ref=sr_1_1?s=books&ie=UTF8&qid=1335958147&sr=1-1
>>
>> A 1" burner sounds a bit on the large size if, by that, you mean 1"
>> schedule 40 pipe.  My burners are all 3/4" pipe.  A #70 drill orifice
>> will give you good heat but not welding heat.  You should not need
>> larger than a #60.  This assumes you have a propane regulator that can
>> be cranked up to 20psi or so (though that's not always needed)
>>
>> A side note:
>> I'd known for years that the range of a regulator could be changed by
>> swapping out the adjusting spring.  I recently discovered that some
>> regulators thrown away with gas grills have a screw-cap over the
>> adjusting spring.  These regulators normally put out low pressure --
>> probably less than 1 psi (I haven't measured it).  Swap out the spring
>> and you can go much higher.  You'll need to find, modify, or make a
>> coil spring to fit the space.  The length, OD, and flatness of the
>> ends must match the original spring.
>>
>> On Wed, May 2, 2012 at 2:55 AM, Geoff Nelson<gjn.pub at gmail.com>  wrote:
>>> Normally I lurk but it is quiet.
>>>
>>> I have managed to do something in-between working on my house and
>>> working for the money to work on my house. I built a small gas forge
>>> from an old propane tank. I lined it with wool impregnated with a
>>> rigidiser. No idea what the product is as I bought it from a refractory
>>> supplier as it was over runs from a commercial project. The bottom of
>>> the forge has a hard refractory brick to rest material on. I am using a
>>> 1 inch side arm burner. Yesterday I decided to make a stirrer for dry
>>> wall compound and got a length of 8 mm reo to forging heat in less than
>>> 2 minutes from cold. I am very happy with the performance.
>>>
>>> However I am not entirely happy with my burner so I am going to have to
>>> do some work on that. I think I do not have the correct ratio between
>>> gas jet size and burner open area. I don't know the size of the orifice
>>> so I will play with open area rather than rebuild the whole burner.
>>>
>>> Geoff
>>> Drouin, AU
>>>
>>> On 2/05/2012 1:18 PM, Mike Spencer wrote:
>>>> Dan wrote:
>>>>
>>>> dk>    testing.....I haven't gotten a letter from theforge in 7 days....
>>>>
>>>> and Frosty replied:
>>>>
>>>> jf>    Been hanging around, not much to report...
>>>>
>>>> Same, more or less. Doing odds and ends getting ready for gardening
>>>> time -- fix up electric deer fence, haul home some manure, compost the
>>>> past year's kitchen garbage, intall a new pea trellis.  No excitement
>>>> at the anvil.
>>>>
>>>> jf>    ...except it's been warm and I'm enjoying it.
>>>>
>>>> In Nova Scotia, two 80F days in mid *March* -- unheard-of.  If it hits
>>>> 80 for a week in August, everybody complains about the heat.  Now
>>>> three nights of hard frost at the very tail end of April.
>>>>
>>>>
>>>> Just keeping Dan's mailbox warm, y'unnerstand. ;-)
>>>>
>>>>
>>>> - Mike
>>>>
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>>
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-- 
Bruce
NJ