As Steamchick says, the gas-to-air ratio is the critical part of the business and the reason I concluded burner design to be something of a black art. Making jets was another exercise, but not in futility: in fact, i though mine were quite successful. Lathe speeds just aren't enough, so I used a small pneumatic die grinder, spinning up to 30,000 rpm and this, together with mounting the jet in the grinder chuck, did the needful. Like, you, I buy those cheap Chinese drills and mount 'em in a chucking arrangement which I feed to the rapidly spinning work by hand. It worked quite well, but the jet design itself is lacking, in that I used an installation screw slot across the jet face. However, I've sourced some #mm A/F brass hex, which should allow easier access.
[/QUOTE]
K
Hi Wazrus. I was interested in your post. The "Mongolian" burner arrangement you mention has been mastered by a few - Marty burners have been quoted in some posts, and another guy (J. E. Nystrom? Someone will correct me as my memory isn't perfect!) Has published his Christmas tree design in a magazine. I know a guy with a 4in vertical boiler for his Clayton wagon who has used 3 Xmas Tree burners successfully. He rates the whole burner at 27 kW max on Propane, and has now mothballed the coal fire grate and shovel. I am trying to advise someone in the club on how to gas fire his 3 1/2" 0-6-0 loco, with a grate 45mm x 85mm... I really have no experience except some reading of others' successes, so would be glad to know of your firebox size, and your "best" burners? - jet sizes and number of jets?
On making jets... I have gone a different route. I found my 1000rpm hand grinder was too fast for 0.30mm drills and below, as the end just flew off over 8000rpm! Imperfect centre in the collet I guess... and centrifugal forces flung the drill to parts unknown.... but I have success with a very accurate chuck in the lathe tailstock.... and at a relatively slow speed
(below 1000rpm) carefully and delicately feed the tailstock mounted drill into the jet, held in the chuck. Lots of practice, and a couple of dozen drill bits later I can fairly accurately make 0.25mm drilling in brass.. I pre-drill so the jet hole is between 2 and 3 mm deep into a 1mm feed hole.
But the key to success is a centre hole, that is barely a pin-pick dot made by a very sharp conical dremel bit with a sharp centre. This too has been mounted in the tailstock, 1 operation before drilling. The accurate centre ensures the sub-mm drill doesn't wander and go over-size.
I also use hex brass rod to make jets now, but for many years simply used 3/16" round bar, and filed 2 flats - to suit a primus proprietary jet tool.
Hope this helps,
K2
[/QUOTE]
K
Hi Wazrus. I was interested in your post. The "Mongolian" burner arrangement you mention has been mastered by a few - Marty burners have been quoted in some posts, and another guy (J. E. Nystrom? Someone will correct me as my memory isn't perfect!) Has published his Christmas tree design in a magazine. I know a guy with a 4in vertical boiler for his Clayton wagon who has used 3 Xmas Tree burners successfully. He rates the whole burner at 27 kW max on Propane, and has now mothballed the coal fire grate and shovel. I am trying to advise someone in the club on how to gas fire his 3 1/2" 0-6-0 loco, with a grate 45mm x 85mm... I really have no experience except some reading of others' successes, so would be glad to know of your firebox size, and your "best" burners? - jet sizes and number of jets?
On making jets... I have gone a different route. I found my 1000rpm hand grinder was too fast for 0.30mm drills and below, as the end just flew off over 8000rpm! Imperfect centre in the collet I guess... and centrifugal forces flung the drill to parts unknown.... but I have success with a very accurate chuck in the lathe tailstock.... and at a relatively slow speed
(below 1000rpm) carefully and delicately feed the tailstock mounted drill into the jet, held in the chuck. Lots of practice, and a couple of dozen drill bits later I can fairly accurately make 0.25mm drilling in brass.. I pre-drill so the jet hole is between 2 and 3 mm deep into a 1mm feed hole.
But the key to success is a centre hole, that is barely a pin-pick dot made by a very sharp conical dremel bit with a sharp centre. This too has been mounted in the tailstock, 1 operation before drilling. The accurate centre ensures the sub-mm drill doesn't wander and go over-size.
I also use hex brass rod to make jets now, but for many years simply used 3/16" round bar, and filed 2 flats - to suit a primus proprietary jet tool.
Hope this helps,
K2
