Merlin Tech ~

"What makes a Merlin so special?" 

We asked the tech-heads at Merlin this question and here is their detailed response:

 Many high-end frames are made of exotic materials without much explanation of their use. Tag labels such as carbon fiber or titanium to a bike frame and it automatically shoots up in price. But evaluate what is so special about the material in its specific application and see if it’s a better value; is it better than what exists? Evaluate the material itself. Is it the best that can be had for a bicycle frame? Companies unable to compete with Merlin's quality, compete with less expensive frames and with less technical know-how, selling with hype and price point. Often their end result is more expensive than many existing frames yet lacking any net gain in performance or quality.

Merlin, however, can explain every aspect of their frames and the material they build with. They make optimum use of their material of choice – titanium. Merlin is probably the most widely imitated frame made. They preceded the titanium bike craze. In fact, they created it. All current titanium frame manufacturers are riding on Merlin’s coattails. But Merlin's standards for certification are the highest in the industry. Higher in fact than some aerospace industry standards for certification. Merlin is responsible for a number of innovations in titanium frames: first titanium mountain bike frame – 1986; invented double butted seamless 3-2.5 tubing; first Grade 4 seamless commercially pure tubing; offset S-bend chainstays and seatstays.

Titanium's Design Advantages

Because of titanium's high strength to weight ratio, the design of a titanium frame can be "fine-tuned", or manipulated with greater accuracy and gain than steel, aluminum, or plastic. There is a greater ability, when using titanium, to place stiffness where stiffness is needed and compliance where compliance is needed while increasing overall strength and reducing frame weight. Ride quality, durability, and weight are the three primary features that need to be addressed to create a bike frame. Titanium, better than any other currently used material, enables a frame designer to encompass all of the ideal properties of a bike frame: torsional rigidity, vertical compliance, high fatigue endurance, light weight, corrosion resistance. Of course, this is true only if the titanium is of the highest quality and of a suitable alloy. It needs to have exact alloy specifications, exact wall thicknesses and diameters, superior straightness in tube lengths, and it has to be worked in such a way that none of its properties are lost. This is why Merlin specifies their own tubing to meet and exceed (straightness and surface finish) aerospace industry standards. This is the difference between the certified grade Merlin uses versus the sport grade and scrap grade other frame manufacturers choose.

Certification And Precision

Certification enables Merlin to use only materials with specific levels of quality. Tubing that is not certified to meet specifications varies widely in its properties. The primary qualities that are measured in the Merlin certification process are purity of alloy, tensile strength, yield strength, elongation, straightness and dimensions, radial texture and surface finish. Other makers use lesser grades of tubing, non-size specific tubesets, lower levels of workmanship and often employ tube manipulations that alter the positive properties of titanium. There can be neither consistency nor any guarantee of the overall quality of their frames. They will be titanium. They may even be certified. But, they won't be certified to Merlin's standards, nor will they embody the best features of titanium required for a bike frame.

Merlin's exactness, or precision, has elevated the status of their frames beyond their competitors. This must be explained because precision can be hard to see. Merlin uses only size specific tubing. Starting from the most popular frame sizes (17.5" mountain and 56cm road) all other sizes are designed to have the same ride properties. Hence, Merlin uses tubes to suit each size and model made. Different wall thicknesses, different diameters and geometry adjustments will be found through all sizes. This ensures a 49cm road will have the same properties as a 56cm road, so that from size to size all Merlins ride consistently.

 In order to copy Merlin, one would have to buy every frame in all sizes and reverse engineer the entire line. That means measure each wall thickness, internal diameter, external diameter, each tube length, butt length and taper, all frame angles, and bottom bracket heights, etc. Then, source tubing that meets or exceeds Merlin standards. This would be a burdensome undertaking, and it would mean owning 46 Merlins, over $100K retail in frames and forks, and cutting them apart! This should give you an idea of how detailed Merlins are, and how much the line is geared toward serving the rider and maintaining the integrity of the exclusive Merlin design.

Construction And Design

Merlins are built by the following procedure: tubes are mitered, cleaned of all contaminants then tack welded and checked for alignment. From here, the frame is welded, checked halfway for bottom bracket alignment, and then welding is completed. Once again, overall alignment is checked then small-parts are welded into place, followed by another alignment check. The head tube and seat tube are reamed and faced and then the bottom bracket shell is machined, threaded and faced; one last alignment check and then the frame is finished, decaled and ready to ship.

 The alignment of a Merlin frame is checked five times when it is being built. This way cold-setting is minimal and alignment precision is maintained from start to finish. The bottom bracket shell is cut, threaded, and faced after the entire frame is welded. Tubes distort when they are welded, especially tubes where the most welds are concentrated: bottom bracket shell, head tube and seat tube at the collar. By finishing these parts of the frame after welding, they are guaranteed to be round and straight with their axis perfectly perpendicular (BB shell) or parallel (head and seat tubes) with regard to internal frame alignment.

 Merlin's welders use a double pass weld where the second weld is a puddle. This is not just structurally sounder than a single pass, but in the right hands it is also an aesthetic touch. The first weld ensures 100% penetration of the filler metal. With the second weld the welder allows the weld wire to puddle, covering more surface area and filling the joint with more material. This maximizes the strength of the weld. The welder's skill guarantees this is done properly; this is not something that can be mechanized. In 1994, in an independent test using x-ray, Merlin was the only frame of seven tested not to have defective welds! Welds are created 1/4" to 1/2" at a time, not only to prevent oxygen contamination and overheating, but also because different joints must be welded in sequence to maintain tube straightness allowing for heat distortion. The welder actually moves to other welds before fully completing one. It requires an average of four hours to weld a Merlin frame!

 The various manipulations of Merlin's tubing are measures to exploit the properties of titanium, as applied to the design of Merlin's frames. These would include: the specific placement of tubes, size specific tube diameters and wall thicknesses, S-bends and V-bends, external butting, the use of different titanium alloys and even the use of 6-4 plate in the rear dropouts. Because tapering titanium causes the molecular orientation to be compromised, meaning brittle tubing and reduced fatigue endurance, chain stays and seat stays are not tapered.

 The S-bends and V-bends have several design advantages. The first is that the shaping of the stays allows for a larger diameter stay. Space is a consideration on a bike frame in order to accommodate tire clearance, rider position and component placement. The bends actually fit the stays to the rear triangle. Brake placement is more efficient since the caliper bosses are positioned on the center line of the stay where they are most supported and provide a stiffer feel. Increased crank clearance permits low Q-factor bottom brackets and ample pedal stroke clearance. And, there is room for oversize tires. Narrower diameter seat stays provide some vertical compliance, while 7/8" diameter chain stays add lateral stiffness.

The use of 6-4 plate in the dropouts is critical. Merlin's dropouts are so nearly indestructible that often a hanger bolt breaks off inside the dropout threading before the dropout bends! 6-4 titanium is not as ductile as 3-2.5, hence it has not been extruded into tubing yet where its strength exceeds that of 3-2.5. But in plate form its strength is a great deal higher than 3-2.5.

Merlin's straight gauge double butted tubing begins as "tube hollows" almost twice the outside diameter of the finished tube and with wall thicknesses of nearly 3/4 of an inch. Through cold working and annealing, the tube hollow is transformed into MTS325. The interior of the tube is supported with a mandrel and rockers work the tube externally, literally pushing material outward to the ends of the tube. It requires numerous steps and annealing to bring the tube to its final configuration. This process creates a tube that is free of surface notching, has a proper grain orientation, and is not embrittled. The butting of MTS325 is external and done by a process, proprietary to Merlin, that creates a butted tube without any surface degradation and with correct grain orientation. Internal butts, designed to work with lugs, are swaged which causes significant alteration of grain orientation. An externally butted tube, as used by Merlin proves to be stronger than an internally butted tube of the same weight.

Ride Description

Riders typically ask about "stiffness" and "lightness". Stiffness is what consumers learn primarily from the aluminum bike market and such stiffness is usually dead feeling. A Merlin is laterally stiff yet it also has a brightness, a liveliness that is lacking in other frames. 

Of course, a Merlin is plenty light. But, every concession to lightness, whether in a frame or a derailleur, is a concession to strength. Titanium still offers the highest strength to weight ratio of any popular frame material. And, Merlin's MTS325 is still the best bike tubing to be had in titanium.

Precision is a key ingredient in the way a bike rides. And, precision has everything to do with the way Merlin's ride. The frames are built to a very high level of exactness. And as we've pointed out, the tubing they are built from is created to the highest level of exactness in the industry. Such precision means the frames ride consistently for riders of every size, the handling characteristics are dependable, balance is better, components fit better, the frame last longer and encompass all of the positive qualities necessary in a bike design. 

Merlin's use of certified tubing, Merlin's level of workmanship, and Merlin's design are proven in the ride. The bikes look elegant and they ride beautifully. Remember these three points: Merlin certified tubing, size-specific tubesets, precision workmanship and design. These are the proofs of Merlin's passion and what it takes to build the finest titanium frames in the world. No other company has investigated titanium as thoroughly as Merlin and it shows in the ride! 

This page was last edited on 10/10/2006