need advice for homade propane furnace



James/Stan, thanks I will definitely pick up some tips. The next step is likely another drilled hole but as you can see I like to have several options as far as config goes.
Thanks again,
- Ben
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James Waldby wrote:

The mig tips I have found are threaded 1/4-fine
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Ron Thompson
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James Waldby wrote:

If you go the contact tip route (a good idea) you can save yourself a lot of misery by drilling most of the way through from the back side (the threaded end) with a larger drill bit, then drilling out the front end with the small one.
The changeable tips allows you to try different sizes in progression, then put in a new tip and drill it to the size that worked best. Mounting the tip so you can adjust it fore and aft to vary the air draw is handy too.
Cheers Trevor Jones
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On Mon, 16 Apr 2007 23:10:28 GMT, Trevor Jones

=========http://www.use-enco.com/CGI/INLMK32?PARTPG=INSRAR2 #61-#80 set--20$US #1-#60 set -- 28-173$US above includes index
by the drill [check for minimum quantity typically 6 or 12] http://wttool.resultspage.com/search?p=Q&srid=S9-3&ts=custom&lbc=wttool&uid 6095168&w=number+drills screw machine length 0.45$US ea. jobber length 0.33$US ea.
Unka' George ===============When we are planning for posterity, we ought to remember that virtue is not hereditary. Thomas Paine (1737-1809), Anglo-American political theorist, writer. Common Sense, ch. 4 (1776).
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On Mon, 16 Apr 2007 23:10:28 GMT, Trevor Jones

another tip if you have problems drilling small diameter holes -- use what is called a jiggle pin.
basicallly a much larger hole, with a wire inserted and bent over to retain it in the hole to reduce the area.
much easier to drill and less likely to clog.
Unka' George ===============When we are planning for posterity, we ought to remember that virtue is not hereditary. Thomas Paine (1737-1809), Anglo-American political theorist, writer. Common Sense, ch. 4 (1776).
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F. George McDuffee wrote:

Geez, George. You really gotta work at your attributions when you reply to posts.
You replied twice to answer a question that I did not ask. :-)
Cheers Trevor Jones
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F. George McDuffee wrote:

I don't think this would be too good in this application. The high pressure propane uses it's velocity to mix with the air. The jiggle pin would disrupt the flow. These burners work best when the gas is introduced directly down the middle of the burner tube. One good idea I saw (I think from Rupert Wenig) was to use water to check the alignment. Put the water through the mig tip and see if it is centered.
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Trevor Jones wrote:

Why drill them at all? Just but one of each available size and swap them until you get what you want.
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Ron Thompson wrote:

Because of a couple reasons. Firstly is that the tips, come in sizes for wire, not always the optimum size for the jet you want. The main one is that you only have to buy one pack of tips.
The drills will be useful at a later date. :-)
Tips, only if you have a mig welder.
Cheers Trevor Jones (who pounds brass rod into the end of a pipe nipple, shapes the outside, and drills as required)
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A real hardware store ought to handle number bits at least to #60, some even have the weenie #61-80 sets. Some of the forge burner makers are using MIG welding tips for fuel jets, the part of the MIG handle that the wire feeds through. These are relatively cheap and available in several hole diameters, check with a local welding supply. If you screw up with redrilling, they're cheap enough to discard and get another.
Stan
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Ben wrote:

A lot of burner designs use a mig tip for the orifice. They are easy to swap for tuning.
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Kind of the same problem. Its not one or the other, but the proper mixture of both.

I bought one of those 115 drill bit kits from HF for this. I've been slowly replacing the high use bits with good bits, but its nice to have one of everything.
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Do a Google on "Forge Burner" ( I'm sure you have but I don't remember which site I saw it on) somewhere I saw a chart listing the hole diameter of MIG nozzles and the recommendation to use them for the metering jet. Also there is considerable discussion of jet sizes and recommended pressure regulators on several sites.
The burner I built is a copy of the Rex design as it seemed to be the most efficient type, although in actual practice it may not matter. I don't remember the actual sizes but to select the metering jet size I arbitrarily decided on 10 PSI fuel pressure and then drilled the jet so that was as close to a neutral flame as possible.
Re drills,:any mechinery supply shop should be able to supply either individual drill bits to #80, or a set thereof.
Bruce in Bangkok (brucepaigeatgmaildotcom)
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I don't know much about gas burners but I do know that changing the orfice size does not give exactly the same effect as changing the gas pressure. In addition to the amount of gas flow, the velocity of the flow is important. High pressure and a small orfice will give higher velocity than low pressure and a large orfice. The velocity needs to be appropriate for the flame propagation velocity or the flame will pop back (velocity too low) or blow off the burner (velocity to high). It seems to me that best tuning would require adjustment of both ehe orfice and gas pressure as well as the air flow.
Don Young
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On Mon, 16 Apr 2007 09:18:54 -0500, Ben wrote:

Use MIG welding tips for a jet. Available in a variety of sizes, and cheap. The thread on the end is usually either M6 or 1/4", depending on the brand
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Ben wrote:

Sounds like too much fuel for the air. The oliver design doesn't allow enough outside air into the burner, IMHO. Try making the holes into slots.
See the link below to the castinghobby group. We'd love to have you join.
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