Framebuilding questions

I think I’ve finally got it.

For a long time, I’ve wanted to build a frame, but I don’t have any welding equipment. I didn’t want to pay someone to do it, and I wasn’t willing to lay down the 200+ dollars to get started, plus having to deal with all the extra equipment. I’ve found one relatively easy and inexpensive way to get started.

Bernzomatic has a new torch called the TS8000, which from what I’ve been researching, gets hot enough to braze, but not weld. Fine by me. Because it only costs $50.00 at my local Home Depot. It runs on MAPP gas, which is almost as hot as acetylene, but is supposedly less dangerous, and you can get it in little $7 bottles. The nice thing is that, unlike the cheap oxy-MAPP torches (which get hot enough to bot cut and weld), this one will last long enough to build an entire bike frame, meaning that it is relatively inexpensive to operate. And brazing should be fine for what I want to experiment with, especially using thin walled tubing.

Which brings me to my question. Having no experience whatsoever with welding, where do I get the steel tubing to work with? I have found it online, but I’m wondering where I can find it locally. Are there places where I can buy 2-10 feet of tubing? At Home Depot, I can find a few offerings of raw steel, but there’s not many options. They have a wide selection of conduit, but that is galvanized, which can be dangerous to work with (I have done my homework). I would prefer a place where I could walk in, buy the stuff, and not feel like an idiot because everyone there is a professional welder who would laugh at what I’m trying to do. What kind of stores do I go to? Looking up steel or steel pipe seems to give me places that deal in industrial supplies, where people are buying enough to build skyscrapers.

Eventually, I’m going to build myself a high quality Chromoly frame, but for now, I just want to try brazing a cheap frame together to see what it’s like.

In the Uk there’s a chain of stores called Metal Supermarket, who will sell you any amount of material, cut to size. I have no idea if they opeate in the US, but if so they’re exactly what you’re lookking for. You might like to look in to car-modifying shops or mail order companies, they often offer small amounts of material intended for purchase by non-professionals.

Dont buy steel cut to length. If you can transport it and you wil use it, buy it in stock length and cut it yourself. It will cost you quite a bit less, They normaly charge quite a bit to cut it to length.

i was thinking about making a frame at school next year, so they’d get the material hopefully, but i havn’t checked. i think most car body repair shops and fabrication companies may be able to get you some.

Check the yellow pages under welding. Welders and welding supply companies will know where to buy steel and it’s various permutations… Alloys. If you are serious about getting into welding some school districts offer adult classes and depending on the size or demographics of your home town, there could also be places that rent TIG or MIG equipment, although it’s something you could easily do with a torch if you found someone with the skills that could help you along that doesn’t have the equipment at home.

You should also spend the time fabbing a good solid frame jig and locating a chop saw or band saw with metal cutting blade, a hand grinder, your choice of tool for rounding the cuts to fit the joints, a milling machine for doing the bearing blocks (which could be as simple as a drill press outfitted to do simple machining)… Which may bring you back to locating a welding class with the right tools to do a good job or a friend that has a shop.

With any construction project be it wood or metal, getting good results depends on the “set up” and having the right tools, as much as it is in quality fabrication.

Hey Paco, I get my tubing from the Chassis shop. They have everything listed on their website and they have a ton of sizes and wall thicknesses. It costs only a little bit more to get cut lengths and unless you are going to build a lot of unicycles it’s worth it to just buy what you need. There could be someone in your area that sells cromoly steel tubing but you won’t find it at your usual construction steel supplier. I usualy use .049" wall thickness for fork legs and 1-1/8" .058" tubing for the seat tube this works for 1" seatposts or 25.4mm. The size that will fit 27.2 mm seat posts without machining is way to big and thick walled and if you don’t want to use a machine shop I would go with the 25.4 seat post or you can cut up an old mountain bike for a seat tube.

ok i dont have much welding experience either but that doesent sounds like something to start with (sounds difficult) and if it not gets so hot, it might brake easily
I would buy a electric welder or loan one but thats just my opinion

Brazing is realy pretty easy and with a little bit of practice it can be stronger than welding especialy if the welding is done by an inexperienced welder.

I would just try practicing on a couple of pieces of scrap first. I have built twelve unicycle frames this way starting out with no experience and I have never had a frame break.

A couple of thing that will come in handy is a 4-1/2" angle grinder with some thin cutting wheels and a flap sanding wheel, these work much better than the coarse grinding wheels that come with the grinder. A dremel tool and cloth sandpaper is also great for cleaning up the flux and black crap.

I bought my tubing from novacycles.com

They’re an excellent source for steel tubing, also Titanium.

Cheers and good luck with your frame!

Cr

What did your research tell you, exactly? Did you look at flame temperature or BTU output? Did you compare it to an oxy-acetylene setup?

The reason I ask is because, even though the flame may achieve the temperature required to melt the brazing rod, you don’t know how long you’ll have to hold the flame over your joint in order to achieve that temperature. If it ends up being a long time, you won’t achieve a strong braze at all… or if you do, it’ll be localized to a small area, and you want a strong braze all the way around the joint.

I speak from experience here, having bought the oxy-MAPP setup you mentioned for some hobby welding, and trying to do a frame repair with that setup. I found, for tubing suitable for frames, it’s only good for spot-welds, and barely passable at that.

If you’re willing to fork out $50 for a torch, you could save a little more dough and get an entry-level oxy-acetylene kit for about $150 new (half that used) and rent some tanks for cheap. Then you’d have a setup that’d actually get you somewhere, and give you real welding experience in the process.

You’re finding the right place, you just need to find a supplier that deals in small amounts. Call around and ask. If you find a “nice guy” supplier, he might even cut it for you at no added cost… I’ve found most places here include that service for free.

Make sure to buy enough for a few frames, as you’ll likely scrap your first and/or second attempts. I’d recommend that you buy the same tubing for your practice frame vs. your “production” frame as different tubing welds differently… you’d want to practice on the “real deal” if you want a good final product.

My 2c.

Thanks, everyone. I guess I’ll just have to start calling around (I hate talking to people on the phone; I don’t even own a cell phone).

I’ve read a number of b*ke building websites which say that the MAPP only will work for brazing, so that’s why I want to start with that. My problem with oxy-acetylene or stick welding is that I don’t want to spend over $100. I’ll probably be onto another hobby by next week, and I don’t want to feel guilty about not playing with an expensive toy. Some day, when I have my own house with a workshop and plenty of space to keep everything (an a real job to pay for it all), I’ll probably look at getting better equipment. But right now it’s cheap or nothing.

I live in a large enough area (200,000-500,000 people) that there should be someone locally willing to take my money. It just comes down to finding them.

Once I test my setup, I’ll report back and tell you whether or not it’s worth it. Someone’s got the be the first, right?

By the way, some people even braze with propane (although it’s much harder), so MAPP should work.

Maestro8 is right about getting the metal hot enough. You have to get both pieces hot enough for the bronze to flow into the joint like solder. If you don’t get it hot enough fast enough your flux burns away and you get oxidation and a weak joint. You could in therory use propane but only for very small things, you will never get your frame parts hot enough though.

The total BTUs is the important thing not just the flame temperature.

Also you definitly want to use 41-30 cromoly steel not mild steel. And you will have trouble finding a good variety of tubing sizes and wall thicknesses in mild steel. It’s also about how the tubing is made the good stuff doesn’t have a seam and is much stronger.

Right now, I just want to experiment. Once I’m ready to build my final frame, I’m probably going to buy chromoly online. So I’m just looking at using as cheap of tubing as I can find to start. I know it won’t be as strong or as light as it could be, but I just want to find a local supplier of tubing (even square would be fine for now) where I can get as much as I might need for the project at hand and go back if I need more. That way, I’m not worrying about messing up while I’m still learning.

I found one place around here that would work – if I don’t mind making a minimum order of 250 feet. Giant giraffe, anyone?

The propane proponents are able to braze by preheating the metal in a stove, or over an open flame, then using propane to heat it up just enough to get the brazing rods to melt. Sounds overly complicated. But the air-mapp system theoretically gets the base metal hot enough to melt the silver or brass brazing rods and enter the joint via capillary action (I went to the library and checked out three books on welding).

Source of choice of one Evan Byrne.

I just compared the price of 1/2" .049" round 4130 tubing and The aircraft spruce and specialty was $3.30 a foot and the chassis shop was $2.76 per foot and $2.16 if you buy a full length 17’-24’. and they will cut it into 48" lengths for free for UPS standard shipping.

It’s realy not that expensive for the 4130 cromo since it doesn’t take that much.

It will definitly be more if you have to buy 250 feet.

I just bought enough to build six muni frames and with shipping it was $78 only $13 apiece.

I would like to build a frame myself, seems like it might be a fun project and something to be proud of. Are you planing on bending the tubing to make a frame like the nimbus?

if i could either weld (mig) or braze chromoly tubing, which would be preferable?

From my vast experience (okay, my research), mig welding will create a stronger connection, but if done wrong on thin walled tubing, the metal may fail away from the weld because of the intense heat. The brazing will be strong enough if done right, but if done wrong, the braze itself may fail. But from what I’ve read, both a weld and a braze can end up stronger than the tubing itself, so both would work. It depends on what you have access to and what you trust yourself to work with.

And it looks like aircraft spruce is the place to buy from when I’m ready to buy the quality stuff. How much does shipping end up running? From a few sources I’ve seen online, it can end up costing as much as the metal itself.

I have made several uni frames using an electric arc welder and I can safely say that it works well.I am not familiar with mig or tig welding but I am sure although expensive would do a better job than electric arc.As for mapp gas I have got the brazing set up but I purchased it to silver solder copper water pipe which was cheaper than buying or hiring oxy-acetalene.Using the mapp gas on 1/2" copper pipe was easy however on 3/4" pipe it hat to be preheated for about 5 minutes to have any chance of a good braze/solder.I have attempted to braze some small steel sections but failed due to inadequate heat.As for welding uni frames there is a vast difference in weld strength requirements between butt joints and socket type fittings (old style pushbike)I am no expert on welding and this is just an account of my learning pathway.