Oxy-Acetylene vs Acetylene-Air?
 

I was hanging out with a guy last night who does very high end tubing fabrication -- not bicycles, but tubing assemblies for things like torpedoes and flight deck arresting gear. He's also a master welder -- another person there told me that he had seen the guy tig weld beer can material together.

Anyway, we were discussing my first frame, and he asked me what type of torch I was using...I told him Oxy-Acetylene. He asked me why I wasn't using Ait-Acetylene, mentioning that O-A gets really hot, and the A-A torch actually makes it easier to silver braze because the temperature is lower.

Is this true? As I begin shopping around for my first torch, should I be looking at Air-Acetylene rigs? Does A-A get hot enough to do brass brazing if I needed to do so?

Thanks

Pete

Well there is a guy (Velonomad) who's quite build a few frame with your hardware store air-Mapp torch. So yes! The BB and crown will be difficult though, I think he used a piece of steel to reflect the heat. I actually fillet brazed 7/8x0.049 tubes w/ brass on a air-Mapp. I brazed on top of a thick piece of angle iron as a "hearth".

So yes O/A is very hot as you waste the heat away most of the time, and it's easy to char/distort your work. But without it you have to resort to tricks that will make your life harder, and you risk of heating the work for a longer time and on a greater area.

Also w/ air-A or mapp you'll be limited to silver basically unless you have a hearth.

Another option is oxy-propane. It's the set-up I'm building up.

Unless you build professionally, I would suggest against anything acetylene, with or without oxygen. I emptied my last oxygen and acetylene bottles over 6 years ago and have been tickled-pink ever since. I now use oxy-propane via oxygen concentrator and 20 lb. BBQ bottles. I figure I lost about 400f, but I also 'lost' expensive refills and back-breaking bottle handling. O/P functions best with alt-fuel tips and mixer, and you'll need to purchase a 'T' rated fuel hose, but little else. I use a Victor J-28 handle, Victor VTS-710 fuel reg and 'TEN' series nozzles w/UN-J mixer. Be advised, however, welding (as opposed to brazing) with O/P is not for the faint of heart and more difficult than O/A. This is from someone who has over 30 years with oxy-acetylene

Thanks for the info...Oxy-Propane sounds like a good option, as I'm not wild about the sooty floaters that Acetylene creates...my workshop is in my basement and I'd hate to get soot all over the house. And, of course, I can just go to Sears and pick up a Blue Rhino tank for $20. The only time I think I would weld would be if I planned on cutting/grafting lugs together for sloping top tubes and that sort of thing. PaPa, I googled for oxygen concentrator and all I found was for medical applications. Do you have any more info on what to look for in an oxygen concentrator?

Thanks,

Pete

Pete,

Medical OC's have been, and continue to be used for glass working (beads, etc). Most seem to be rated for 3 to 5 LPM @ 7 to 9 PSI. (I typically braze at 2-3 LPM @ 5-6 PSI). Oxygen purity varies from machine-to-machine. Just about anything above 85% purity seems to function fine, the higher of course, the better. My first was an older, $150 Invacare, but I happened across a low hour, DeVilbiss 505DS w/OSD with a cracked HEPA filter a few years back for $20 at my local secondhand - cost me $25 for a replacement filer. Most OC's have hour meters so look for low numbers (below 10k is preferred). My old Invacare has 37,000 and still works fine. Be patient and selective and spend time on Craigslist.

Hey Papa that's a good idea for the oxy concentrator! Definitely safer and probably cheaper (In my neck of the woods you rent a oxy tank for ~130$ a year -includes delivery- and fill ups are about 50$).

Pete sorry for the hijack, but Papa where did you get your victor tips? I just bought a J-28 w/ UNN-J nozzle (propane compatible I believe) but it came w/ a #00 TEP tip that may be too small for propane.

Late edit: actually renting an oxy tank is 60$/year + 30$ refill, the above prices are for oxy AND acet

The place I got nozzles years ago, is no longer.

Nozzles labeled "TE" are for acetylene - "TEN" is for N/G and propane. The only visible difference that I can detect between the type "TEN" nozzles and the "TE" nozzles is that the TEN's have a recessed orifice while the type TE's do not. The TEN's are less sensitive to breezy conditions and flame settings remain more consistent and stable. However, I occasionally use a TE nozzles, so don't automatically assume the TE's won't work, because they do, just not as well.

Victor type "TEN" P/N's... (I spend more time with sizes 3 and 4). IIRC the threads are 5/16"-27

0311-0485 (size 2)
0311-0486 (size 3)
0311-0487 (size 4)
0311-0488 (size 5)

Try here for nozzles: https://weldingsupply.securesites.co...F:OR:0311-0589

BTW, I first bought a UNN-J (N/G specific) mixer but wasn't pleased with the results, so I switched to, and continue to use the UN-J (acetylene specific) mixer. IIRC, the UNN-J is for low pressure N/G (typically 11 in. mercury), or perhaps maybe I got a defective mixer.. dunno.

This conversation fascinates me. I have been using MAPP, which works well enough for silver, but have wanted a "proper" torch for some time. The stumbling point is that I work in my attached garage and am not willing to bring acetylene into the picture.

Do I understand that you folks are using the common "cylinder exchange" propane bottles available at gas stations, Home Depot, etc., along with medical oxygen concentrators? If this is the case, I will pursue it, but it seems to me that there must be some innovative plumbing involved. Is there anyone willing to hold my hand and take me through detailed steps necessary to set this all up?

Sure, but unless you're female, i'd rather not :)

Most OC's have, or come with a barbed, tapered fitting so most any 3/16" and 1/4" oxy hoses will just slip-on after removing the brass fitting. The initial downside, is that you are limited to the OC's internally set line pressure of about 7-9 PSI. I used my for several weeks before pulling the OC cover and tweaking the machine's internal regulator - but I'm picky, even though I could've continued using it as-is.

On the fuel side, if your acetylene regulator has a CGA-510 bottle fitting (most mid-sized and larger regs do), then simply screw it on the propane bottle.

edit: Corrected hose sizes above - originally stated 3/8" but that was incorrect (I use 3/16")

I found some documentation saying the UNN-J works with NG and LP. I'll see that when I receive it! Otherwise many thanks for the link and advice.

tuz,

Briefly, I started with a new UNN-J, and the 'optimized' flame looked OK, but was puny. I cranked the reg up to 10 PSI and saw little difference - even tried different nozzles. Acted like the mixer was restricted. If yours proves different (and I sincerely hope it does because they ain't cheap) then please let me know.

Mixer? Is that because of the propane or because of the concentrator?

Neither. The mixer is positioned between the torch handle and the nozzle (tip). Typically, the screw-on acetylene tip assy comes with mixers - the UN-J and the UNN-J mixers however, have replaceable nozzles.

Oxy-Propane - 5 psi fuel - 6 psi oxygen w/oxygen concentrator
Victor type TEN tip - size #4 (.073") For size reference the nozzle is 1.5" long - O/P typically produces a longer inner cone than O/A, otherwise they look almost identical.

http://i47.tinypic.com/e680te.jpg

The image below was taken about 4 years ago. The coupon is .200" (5mm) thick and brazed with off-the-shelf, 64kpsi LFB in a single 15 second pass using a #4 tip fed with Oxy-Propane w/oxygen concentrator. It was then allowed to cool and bent in AWS coupon bender.

http://i48.tinypic.com/6ro5xd.jpg

So there is no O2 regulator -- you just run the O2 line directly to the torch handle from the concentrator and whatever pressure you get is what you have to work with?

Actually there is an internal reg, but yes, you are essentially correct. As much as I like to tweak line pressures, I have rarely felt restricted with this setup. Between 5 nozzle sizes and the mixture adjustments on the handle, the range is quite broad. Easily from .010" to .250". Maybe someday I'll plumb an external oxygen reg, but so far, I can't honestly say it'd be justified.

Well, I'm off to shop for an O2 concentrator. Thanks for your help!

i dont see what is so scary about keep acetylene in your garage. yes, it is very explosive, but as long as you are educated and safe its not a big deal. there are about 10,000 plumbers driving around right now with acetylene bottles in the back of their van!

Thankfully, no one here is suggesting that you shouldn't.

Acetylene is no more dangerous than any other fuel gas and less dangerous than many.
Acetylene is lighter than air, if the system leaks, the gas will dissipate, unlike the LP gases (Propane) which are heavier than air
and will literally pool in any enclosed areas.

Acetylene tanks are low pressure at 150 PSI full.

I agree that generally speaking any of those gasses are safe, considering how rarely accidents occur. Flashbacks risks are the same with acet or propane. Yes propane pools down but both systems should be used in a well ventilated area. Soot? I'm guessing w/ experience you set your flame quickly. And propane is noisier from what I hear.

I think propane is slightly more practical since it can be easily transported and refilled. This advantage is negated on a high production since it needs more oxy than acet. And using those OC is certainly interesting. I'll look into it as well.

FWIW, I checked the local fire codes before I decided to go with an oxy-acetylene torch. I was a little surprised to find that are were fewer restrictions on oxy/acet then there are on oxy-propane.

Believe it or not I am not allowed to have more than two of the 1-pound handheld torch cylinders in a residential structure (section 3809.9.2), and there seems to be no allowance for doing hot-work with LP-gas in a residence outside of construction/renovation work on the building itself (section 2605.4.2.1.1, 105.6.23)

On the other hand, I can work with individual acetylene tanks up to 40 c.f. (or 150 c.f. with a permit) and totaling up to 200 c.f. (or 1000 c.f. with permit) in a residence (sections 2605.4.1.3.1, 105.6.8, 105.6.23)

http://www2.iccsafe.org/states/Seatt...e_frameset.htm

Propane has two big drawbacks: it's heavier than air and will fill up a basement or garage if it leaks. And if a tank ruptures in a fire it is very violent (acetylene less so because it is limited by how fast it comes out of the acetone solution)

Propane can be run at higher pressures than acetylene, which is nice for cutting thick plate (not much call for that with bicycles, though) and for use in manifold systems.

In the safety sheets acetylene is referred to as "inherently unstable". So while I always appreciate unsolicited off-topic opinions from strangers on the internet... :lol:

With all due respect, 'tis not the chemical, in-and-of-itself, that gets you in trouble,.. it's the user's ignorance and/or recklessness that destroys buildings and puts innocent victims in the hospital. Please don't ask me how many times I've spotted plastic gasoline containers (for lawn mowers) inside and on the floor of the very same structure they use for welding and grinding.