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7 posts • Page 1 of 1
I have an interest in trying some home bike rack-building using 5/16" 4130 tubing and gas brazing/fillets and have been looking into what kit is needed. It seems an entry level workshop can start with gas welding and there is a recent trend to move from oxy/acetylene to oxy/LPG ( driven by the cheaper cost of LPG). There's a great & recent thread on oxy/LPG velocipedesalon (google it) on this topic for those interested in learning more.
Anyway - there's also a move, particularly in the US, to use reconditioned medical units called oxygen concentrators. These units produce O2 at up to 5 L/min at 5 to 7 psi which is sufficient for the task at hand.
These appear to have a market value around the $200-300 mark in the US making them a cheaper and more convenient alternative to bottled O2 in the long run ( LPG is a little cooler than oxy so you end up using more O2).
My questions are this:
a) Who is using O2 concentrator devices like this in Australia ?? and is there a source of reliable reconditioned machines ( & where) ? My attempts to find a source have provided some links to glass bead makers - but the machine costs are nowhere as low as reported US examples. Buying a new unit doesn't seem a sensible option. Ebay list some, but the fine print shows they usually can only deliver 1 L/min at higher O2 concentrations ( which isn't enough)
b) In Perth - are there any introductory classes to learn gas/LPG (or Oxy) brazing at the hobby level ( there's plenty of MIG/TIG welding for certificates - I'm just looking something introductory for the hobbyist).
Any Tafe will have a intorductory welding course. It's general and covers a lot of useful OH&S stuff which I think is important but oxy-acet will be 20 minutes worth of practice and instruction compared to other forms of welding. There just isn't enough of demand from industry for oxy-acet brazing so they heavily favour Tig/Mig instruction.
Oxygen accelerators here in oz are still very expensive compared to the US, as is everything else to do with welding. Oxy/lpg is still your ticket but you'll need to register with BOC or similar for your oxy tank and get a good set of regulators suited to low pressure type brazing you'll be doing with Oxy/Lpg. An local welding supply place will have what you need - it's tempting to buy used or off the web but I think you'll still need to have it checked over tested and have your local welding place and also have flashback arrestors fitted, and use good quality hose. For rack building you'll only need the smallest size tips.
Weight it all up though, it's fun to make stuff but when you look at what off the shelf items cost it's hard to justify all the expense and set up of an oxy kit for your own use.
The OP took the words out of my mouth. I've been watching for used oxygen concentrators from the medical area but the ones that put out 5l/min go for $500-800. When each bottle from BOC costs over $1/day rental, plus gas (which is also why I use MIG gasless wire at home now) the oxy concentrator is paid off in a couple of years. There is a guy in the US who uses his BBQ bottle, and most parts minus the oxy gauges of an oxy/acetylene set, with different tips
http://www.chaski.org/homemachinist/vie ... 12&t=87931
He seems like reasonable inspiration. I'd like to know what the CIG equivalents of the Victor part numbers are though.
Re training: I have looked into it with a similar outcome, except that I keep seeing references to a standard Australia-wide TAFE unit called "MEM05006B Perform brazing and silver soldering (20 hours)" which is apparently taught as part of panel beating, airframe construction, sheet metal work and a few other similar wider scope vocational courses. If someone knows how to get onto that unit by itself, it's what we are looking for.
Then there are the more expensive approaches - like paying $3-4k plus airfare to go and do a framebuilding course at several places in the US, and getting a frame out of it. For example: http://www.bohemianbicycles.com/frame%20class.html
Last edited by wqlava1 on Fri Jun 21, 2013 2:17 pm, edited 1 time in total.
2014 goal 52000m
That's the one i did!
It was great, and an excellent way to learn. We didn't cover any of the different ways of creating a flame though, just traditional oxy and acetylene. Suzy at Little Fish Cycles brazes with LPG I think, but I don't think she uses a concentrator. It's a nice idea from the sound of it. There's a frame building section at Bike Forums that might be able to help with the pros and cons of such a method, but probably not so much with sourcing a unit. The Frame Builders Collective is also another good resource.
I'm designing a workshop now and will look into the brazing equipment a bit later. Keep us informed on what you come up with eh.
It's not that expensive.
Oxy + acetylene in the size need for small scale building are $60 and $115 respectively, cylinder rental is a little under $30 per month (total for both). A complete suitable kit can be had for around $500 from Ausweld http://www.ausweld.com.au/products-page/acetylene-kits/acetylene-upgrade-kits-craftsman/. They also sell consumables but since I work with stainless* I use the Cycle Design stuff, available through Kumo http://www.kumocycles.com/brazing-supplies-for-framebuilders.html.
The market in the US is driven by the insanity that is their health insurance system. The insurers won't let you use a second hand O2 concentrator unless it's been refurbished at most of the cost of a new one, so they are sold off when the first user dies and are as cheap as chips.
* OT: if you are interested in bike specific stainless, talk to the folks at KVA http://www.kvastainless.com/bicycles.html, the product is excellent and they are much easier to deal with than Columbus or Reynolds.
Separately but germane to the discussion: I've been talking to one of the US based teachers of framebuilding courses about flying him over here to run a three week framebuilding course, possibly based in Beechworth, VIC. The cost would be greater than cost of the US course but less than that cost plus the airfare.
One question he's asked is when would be the best time for the course? He's suggesting summer or autumn, I'm thinking spring or summer. What think you?
It can't be between January and April if I am going to assist him as I'm away making wine at that time of year.
Thanks to those that replied - appreciate the information. Having spent some time in the states - I can appreciate & understand how medical insurance can be a huge factor behind the "low" 2nd hand market price in the states. ( Mdical coverage in retirement is a complex issue stateside - and locks many folk to 1 company for their working life.
To Westcoast Pete - I had already read your entries with dave in Tuscon - Its been added to my bucket list ...
To Mark Kelly: Tried to send you a PM - not sure if it got thru. Would be interested in learning more about any proposed course. Feel free to contact me.
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