from Rookie’s keyboard,
Hello, friends
In this post, I will discuss two of the three classic ways to assemble a steel frame.
They are:
a. Lugs b. Welding c. Brazing
I already have a post on brazing, so today I will focus on TIG welds.
TIG Welded Frames
TIG welding stands for Tungsten Inert Gas welding.
During production, two pieces of metal are joined via an arc welding process using a non-consumable tungsten electrode.
The inert shielding gas protects the welded elements and the electrode from contaminations.
- TIG welding is done with a torch that has a tungsten electrode sticking out.
- The torch heats the electrode and melts the two pieces of metal that have to be joined (in this case – bike tubes)
- The melted area forms a pool of metal bonding the two pieces.
- In the other hand, the welder holds a filler rod which melts too and adds strength to the bond.
Think of the welded pieces as two separate chocolates. If you put them next to each other and melt the neighboring ends, they will melt into each other.
The melting process deforms the ends. But if you lay liquid chocolate (e.g., Nutella – lol ) on the affected area, it will fill the gaps and make the bond stronger.
The main difference between brazing and welding is that during brazing the pieces joined together are NOT melted. Only the filler material is. During welding, the welded elements melt too.
TIG Welded Frames Dominate The Steel and Aluminum Market
Most metal frames are TIG welded (including mine).
Here are the reasons:
- Faster & Cheaper
TIG welding is not only faster than brazing but also cleaner and requires less effort to finish/smoothen the area.
A factory with well-trained workers and high-end equipment can manufacture a massive amount of welded frames per day.
To make the same number of lugged frames, the employees will have to invest a lot more time and effort into each unit.
- Easy Geometry Changes
A new set of lugs is needed when the geometry of a lugged frame is changed.
TIG welding doesn’t face such an issue because the welder isn’t restricted by a lug and can alter the angle as needed right away.
- Aluminum in the house
TIG welding can be used to weld aluminum tubing. The setup for welding aluminum isn’t cheap, but the accelerated mass production process makes up for the extra price.
- Lighter
TIG-welded frames do not use lugs and can have more aggressively butted tubes because the welded area is smaller than the lugged one.
The ends of the tubes can be thinner without fear of burning through the tube.
As the wise men say – nothing in life is only positive or negative. Welded frames are the same way. But honestly, the downsides are not major:
- Generic Look
A welded frame has a “nothing special” look whilst a lugged frame is rare and thus considered luxurious.
- The Welding Setup Is Pricey
Many independent frame builders use brazing because it’s cheaper on an individual level.
If you want to weld frames, you will have to invest 1000s of dollars into welding equipment.
On Lugs
Lugged frames look awesome but the production process isn’t nearly as flexible.
They are built of steel tubing connected via external steel fittings known as lugs. Each tube is inserted into an opening of the lug.
Then, the tubes are permanently attached to the lug and the tube next to it via brazing.
Many cyclists consider lugged frames aesthetically pleasing and stylish because:
- The connection is hidden.
- The lugs themselves represent a piece of art and can be shaped and painted many different ways.
People who are into classic road bikes often go for lugged frames simply for the appearance.
Since the brazing process is done with a torch, there’s no need for expensive welding equipment.
Brazing is done with an Oxyacetylene torch because it heats the area incredibly fast. Some makers use less powerful torches because the melting temperature of silver isn’t that high.
Since brazing doesn’t involve electricity, it can be done at locations that do not have an electric outlet.
Of course, brazing isn’t easy and has a long learning curve just like welding.
It’s important to know that during brazing, the tubes aren’t melted. Only the filler rod is. Thus, the tubes are less likely to overheat and lose structural integrity.
For that reason, brazing is considered kinder to bike tubes.
Repairability
Lugged and fillet brazed frames are much easier to repair. If a tube is damaged, the frame builder can heat the joint to melt the brazing material, take out the faulty tube and braze a new one.
Welded frames can also be repaired, but the process is more difficult and expensive to the point where most people prefer to simply buy a new frame.
Major Downsides
The production of a lugged frame is a very time-consuming process because:
- Lugs are an additional element that has to be fabricated.
- Lugs from one frame cannot be used on another unless the geometries of the frames are identical.
- Brazing is slower than welding.
Hence mass producers stay away from lugged frames. The additional labor, the extra costs, and the slower process make little sense when the demographic doesn’t even know what a lugged frame is.
Aluminum = Not an Option
Aluminum frames cannot be brazed because:
a. The filler brazing rod has a higher melting point than aluminum. The long exposure to heat will irreparably damage the aluminum tubes.
b. There are filler rods designed to melt at lower temperatures so that aluminum can be brazed, but they don’t provide enough strength to build a strong frame.
Thus, the lugged frame makers are limited to steel. This isn’t a problem because most people who want a lugged frame prefer steel in the first place.
Steel is denser than aluminum and can therefore provide just as much strength in a slimmer and more elegant package.
By the way, lugged aluminum frames exist, but they’re not brazed. Instead, the builder uses a very strong epoxy to connect the tubes to the lugs. In some cases, there’s also a threaded connection for additional security.
Currently, this process is not in fashion due to the low demand for lugged frames, to begin with.
“Ride Feel”
The frame building process does not have the greatest influence on the bike’s ride feel.
How the framebehaves depends on:
- Tube Material
- Design
- Tube length
- Tube thickness
- Geometry
A skilled frame builder can make a frame that performs as needed by the client via both methods.
And before all, most people can’t and won’t feel a difference between a brazed or a welded frame.
Strength
Some consider lugged frames stronger because:
- The tubes aren’t overheated.
- The ends of the tubes are thicker.
- The lugs add a lot of support.
TIG-welded frames are considered weaker because:
- The tubes are thinner (potentially).
- The tubes are heated to melting temperatures.
- There are no lugs supporting the joint.
Technically, if all variables are the same a lugged frame may be stronger than a TIG welded one, but in practice, the strength of a frame is dependent on many other factors suchs as:
- Tube material and quality
- Tube thickness
- Craftmanship
- Design
- Geometry
A TIG-welded frame can be made brutally strong and fairly light by using oversized tubing. Most MTBs are built this way.
A TIG-welded MTB frame with oversized 7075 aluminum tubing is indefinetely stronger and more durable than a thin road bike frame with lugs.
Until next time,
Rookie
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