Minimum acetylene tank size for frame building?

[Lars1]

Hi,
Im aspiring to build my first frame and Im interested in an oxy acetylene setup. Ive concluded that bigger=better (provided I can transport and store them safely). That being said Im having a hard time finding large tanks in my local market and small acetylene B size tanks seem to be a dime a dozen. My concern is that I can't find a definitive answer as to the acetylene withdrawal rates during frame building and accordingly how big of a tank i need to keep acetylene use within the 1/7th withdrawal rate rule. Ive seen users here (or maybe on mtbr?) citing use of B cylinders and even MC cylinders but the tank size discussion seems centered around cost and refill intervals, and not withdrawal rates. Are these smaller tanks suitable for the more gas intensive processes like fillet brazing, fork crowns etc.?

FWIW Ive used oxy-ace in the past, just never for frame building and I will probably setup an oxy-propane rig as well to see what I prefer. Leaning towards a victor j-28 torch if that matters.

Lars H.

[e-RICHIE]

http://www.velocipedesalon.com/forum...rum-36866.html

[Lars1]

Hi,
Im aspiring to build my first frame and Im interested in an oxy acetylene setup. Ive concluded that bigger=better (provided I can transport and store them safely). That being said Im having a hard time finding large tanks in my local market and small acetylene B size tanks seem to be a dime a dozen. My concern is that I can't find a definitive answer as to the acetylene withdrawal rates during frame building and accordingly how big of a tank i need to keep acetylene use within the 1/7th withdrawal rate rule. Ive seen users here (or maybe on mtbr?) citing use of B cylinders and even MC cylinders but the tank size discussion seems centered around cost and refill intervals, and not withdrawal rates. Are these smaller tanks suitable for the more gas intensive processes like fillet brazing, fork crowns etc.?

FWIW Ive used oxy-ace in the past, just never for frame building and I will probably setup an oxy-propane rig as well to see what I prefer. Leaning towards a victor j-28 torch if that matters.

Lars HEDIN.

Seems I'm breaking rules already… My apologies. Couldn't find an edit feature so my last name is bolded in the quoted text.

-Lars Hedin

[e-RICHIE]

Seems I'm breaking rules already… My apologies. Couldn't find an edit feature so my last name is bolded in the quoted text.

-Lars Hedin

Thanks, Lars.
I'll fix it.

[e-RICHIE]

Hi,
Im aspiring to build my first frame and Im interested in an oxy acetylene setup. Ive concluded that bigger=better (provided I can transport and store them safely). That being said Im having a hard time finding large tanks in my local market and small acetylene B size tanks seem to be a dime a dozen. My concern is that I can't find a definitive answer as to the acetylene withdrawal rates during frame building and accordingly how big of a tank i need to keep acetylene use within the 1/7th withdrawal rate rule. Ive seen users here (or maybe on mtbr?) citing use of B cylinders and even MC cylinders but the tank size discussion seems centered around cost and refill intervals, and not withdrawal rates. Are these smaller tanks suitable for the more gas intensive processes like fillet brazing, fork crowns etc.?
Lars Hedin

By the way - I have no idea what any of this ^ means, but I still make the frames daily. I'll replace a
gas tank 2-3 times a year. I'm on the road now and going from memory. My tank is about 4' tall atmo.

[Jonathan]

The tiny tanks will leave you seriously wanting. If you're working out of a home shop get the largest tanks you can transport and afford. Most gas forms won't deliver to a residential addy even if used commercially. Another option is to look down below at the thread dedicated to propane. There are some ideas about using standard hardware store propane and an oxy generator.

[crumpton]

80lb is what you want. they come from the airgas or similar supply in your area. not the home center.

[Lars1]

To clarify the technical aspect of my question:
My understanding of acetylene systems is that that pressurized Acetylene is stored and stabilized in liquid acetone and that the acetone is only able to release acetylene at a rate of 1/7th the tanks capacity per hour. If you attempt to use more than that rate you draw acetone through the system and wreck your reg's, hoses, torch etc. Therefore the size of your acetylene tank limits the pressure and size of the tip you can use safely. (If Im missing something or incorrect about any of that Im all ears.)

All this considered, how big of a tank do I need to braze safely?

Of course Id still like to go as big as possible. I just want to know what my minimum safe size is and ill work up from there.

[e-RICHIE]

This won't answer your question, but it might - the total torch time on a frame and fork won't exceed
an hour, and that's over 2-3 days at the rate I make them. So if you're new at it, maybe consider this.

[jclay]

I use an AC3, either 65 or 75 cu ft. That's adequate for any of my brazing tips (5 meco midget) but would come up short for a rosebud (which is totally unnecessary). As to trying LP and acetylene to see which you prefer, something that in my opinion I wasted time and money on years back, I think you'll get better, faster if you pick one, learn it, and stick with it. The choice of fuel gas, and switching back and forth, won't make you better; practice and learning one tool well, will. Acetylene will allow a tighter flame cone which is nice for braze ons. I think most builders see it as the more versatile compromise but LP certainly works (and burns through O2 about 3x as fast. My choice would be based more on logistics, not the characteristics of the fuel/flame.

Good luck!

[progetto]

Those gas rates are probably only applicable if using a cutting torch on really heavy plate. I use the small size bottle and never had a problem with pulling liquid acetylene even when using a cutting torch. I have the small as I was a plumber in a former life and they are easier to drag in and out of my truck and around job sites.

[Doug Fattic]

Lars, the orifice size on brazing tips for bicycle frames are small enough that you don’t have to worry about your tank size and flow rate. Get whatever size is convenient for you as far as how often you want to go get a refill. I teach framebuilding classes so I own the biggest size possible that doesn’t have to be rented. However one time I rented size B tanks to give a brazing demonstration at a bike show and was surprised at how long they lasted after I got home just wanting to use them up. It was 3 or 4 frames. Keep in mind that a typical student takes about 3 times longer to braze a joint than a pro.

You might want to consider using propane because of convenience. A full tank costs $50 to own and a refill is $20. I can get about 3 times more brazing time with one of these standard BBQ tanks than my large acetylene tank. You can find them everywhere at all hours at gas stations and every other kind of store. There are no regulations about transport or home use. If you combine propane with an oxygen concentrator, that removes all transport issues and home use restrictions.

Having the right tips makes using propane much easier. With your J-28, you will need the UN-J mixer elbow and TEN – 2 (and 3 and probably 4) tips. You also need T rated hoses. I like the light one from TM technologies.

I give my students the option of choosing either acetylene or propane and the majority prefer propane after trying both.

[crumpton]

late edit, cu ft not lb.

80lb is what you want. they come from the airgas or similar supply in your area. not the home center.

[sam]

I use a 35cuft acetylene, and 40 cuft oxygen. I get about 5-7 frames out of it. In my area this is the largest size you can own the larger tanks I have to lease. I never use it for cutting so I got a smaller matching size oxygen tank, and dont really use it for anything else other then frames.

[Alistair]

Hi,
Im aspiring to build my first frame and Im interested in an oxy acetylene setup. Ive concluded that bigger=better (provided I can transport and store them safely). That being said Im having a hard time finding large tanks in my local market and small acetylene B size tanks seem to be a dime a dozen. My concern is that I can't find a definitive answer as to the acetylene withdrawal rates during frame building and accordingly how big of a tank i need to keep acetylene use within the 1/7th withdrawal rate rule. Ive seen users here (or maybe on mtbr?) citing use of B cylinders and even MC cylinders but the tank size discussion seems centered around cost and refill intervals, and not withdrawal rates. Are these smaller tanks suitable for the more gas intensive processes like fillet brazing, fork crowns etc.?

FWIW Ive used oxy-ace in the past, just never for frame building and I will probably setup an oxy-propane rig as well to see what I prefer. Leaning towards a victor j-28 torch if that matters.

Lars H.

I have a #3 Acetylene tank, which is 75 Cu. ft. I consider it to be a handy size. Big enough to do a few framesets, easy to move around and exchange at the LWS.

Recommended max draw for that tank is (75/7) 10.7 SCFH. Victor lists the flow rate of it's no. 3 size tip (for Acetylene) at 8 - 18 SCFH, over the range of the recommended operating delivery pressure. Flow rate for a No. 4 tip is 10 - 25 SCFH.

From that you can see that a No. 3 tip is probably the largest you'd want to go with that size of tank. Maybe you could drive a No. 4 off it if you really wanted to, I don't know. You would run the risk of drawing Acetone into your regulators, generally not good. Multi port rosebud tips aren't going to work well off a tank of that size eithr (according to the Victor numbers. Never tried it myself).

Alistair.

[Lars1]

Sounds like maybe my concerns over small tanks and withdrawal rates are not so relevant in practicum but there seem to be a lot of votes for tanks in the 60ish-80ish cu.ft. range. I guess Ill shoot for something around 75 cu.ft. since it seems like a safe size from a technical standpoint and will minimize the 40mile drives to my local air gas. Thanks for all the input guys.

[jclay]

I just ran into some updated withdrawal information reportedly from the Compressed Gas Association. They've apparently revised the withdrawal rates for acetylene down from 1/7 cylinder capy per hour to 1/10 for intermittent use and 1/15 for continuous use. The short article is worth reading.

Fuel your safety knowledge - TheFabricator.com

I realize that heretofore I had been exceeding the old recommendations, never mind the revised ones. A 300 cf cylinder, difficult for me to transport, is what I'd need for the largest tips I use. That's the reason I recently decided to switch to LP for lugs, crowns, BB shells. My 75 cf Acetylene cylinder is only for the smaller tips and frame items now.

[Ken Holmes]

I use 40 cf cylinders, the B type. I have consistently gotten nearly 3 fillet brazed frames out of them, usually using up the acetylene before the oxygen. I would have 80cf if I could to save on fills, but transport is more of a pain for me. I bought mine outright years ago, which has certainly paid for itself and reduced headaches around rental fees.

[EricKeller]

the total capacity is important because of how many frames you can make with it, but also because of how fast you can remove the acetylene. My LWS was reluctant to rent me tanks, and I ended up with the largest they would sell me. I think it's 80 cu ft. I did the calculations once, the largest tips that fit on an A1WA will draw gas at a higher than recommended rate. This is mostly useful if you are brazing lugs with brass. The standard AW 205 tip will not overdraw the tank. That's plenty big for fillet brazing a bottom bracket or dropout.

[jon_norstog]

I used "B" tanks for years, because that's what I had. I could build 4-5, sometime 6 frames with one tank of acetylene and have O2 leftover. They were nice for jobs where I had to hump them in on my back. It's an expensive way to buy gas. I've got bigger tanks now. Whatever you get, own your tanks.

Good luck!

jn

"Thursday"