Uncle Pan

35th Anniversary Bike

Update 15/07/20

Fork Rough Assembly Part 1

Screeching machines, glowing chips, metal hits metal. Iron is brought into shape under heat and pressure.

What sounds like a heavy metal music video is currently taking place in our production halls. For our 35th Anniversary Bike we have brought up heavy weapons.Where we used to machine aluminium, our CNC machines now work their way through hard steel.

The pictures will surely tell the experts among you what it is all about. And for all budding professionals – we build our own heavy duty Springer front fork.

Andreas had already hinted several times in the past that he wants to build something “really crazy” now,… and our showroom is already filled with some “really crazy” bikes.

But therein lies the idea and the “madness” of customizing. To implement something that no one has ever done before. From this idea the 35th Anniversary Bike will be developed in the coming weeks and implemented by the whole Thunderbike Team. You can experience it live in weekly steps, just like with our last big building project, the Emperor, for the King of Kings competition.

Once a rough draft of the bike is finished and the approximate dimensions are determined, such a large bike project always starts with the visualization on the computer. In this way the proportions and the later overall line of the bike can be determined in advance. Here, further detailed drawings can be gradually added at a later stage in order to be able to manufacture the individual components.


The necessary parts for the fork, apart from the springs, are completely manufactured in our halls. Initially, the triple trees are made of the same steel as the fork tubes. Steel has the decisive advantage of being twice as strong as aluminium. This is very convenient for us, because the wall thicknesses of the fork tubes can be kept particularly narrow. However, the manufacturing process is much more extensive. The milling machine alone requires four times as much time as machining a workpiece of the same size in aluminium. This is mainly due to the fact that the tool and the material to be machined have the same strength, which results in enormous friction. The resulting heat quickly brings the material to its load limit. Here it is necessary to work with calm and foresight to create the beautifully shaped parts from the massive block of steel.

Learn in the next step how the parts are assembled and welded together.

Fork Rough Assembly Part 2

The previously milled parts are joined and welded together in the next step. The finished Springer fork must have enough elasticity on the one hand, and of course enough strength on the other hand to withstand the extreme suspension forces. Therefore full concentration is required from the very beginning to ensure that all welding seams are meticulously even. The beautiful side effect is of course the noble appearance of the shapely seams

The previously milled parts are joined and welded together in the next step. The finished Springer fork must have enough elasticity on the one hand and of course enough strength on the other hand to withstand the extreme vibration forces. Therefore full concentration is required from the very beginning to ensure that all welding seams are meticulously even. The beautiful side effect is of course the noble appearance of the shapely seams.

During the planning of the triple clamp, small holes were planned in, which later serve as a starting point for welding. So the triple clamps can be connected not only to the fork plates, but also to the rigid fork assembly.

At the upper end of the main body of the fork, the spring holder, also made of steel, is attached according to the same principle and even pinned so that it can absorb more forces and is directly in balance.

The receptacles for the two movable short swing arms in the fork rocker later form the link between the two fork parts and hold the front wheel.

Learn in the next part how the fork development continues, as well as the rest of the bike construction.

Fork Rough Assembly Part 3

It’s a bit of a premiere, our first conventional Springer fork which is completely manufactured in-house.

From the planning to the finished product, we’ve opened all the registers of our skills.

The assembly is pretty straightforward, because all the fork parts fit together perfectly. This is where good pre-planning on the computer pays off and on the other hand our colleagues in the polishing shop grinded and polished all the surfaces of the parts with full dedication to high gloss.

With the Springer fork as an example, you can clearly see that at Thunderbike modern and traditional craftsmanship almost always interlock to meet our own high standards.

Many of you should already know where the journey of our 35th Anniversary Chopper is heading, it’s getting really oldschoolish.

Check back regularly to follow the next steps.


Wheel Production

Nothing screams chopper like 5-spoke wheels!

Even 50 years after the start of this trend, the big star rims have lost nothing of their appeal.

Anyone who has followed the construction of the 35th Anniversary Bike so far knows that it is all about big dimensions. The long Springer fork will later carry a 23 inch custom made front wheel.

Build not bought – this is probably the most appropriate term for our newly designed front wheel, because there is not a single wheel on the accessory market that meets the required standards.


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As a starting point we use the original front wheel of a Harley-Davidson Rocker, which our CAD designer and constructor Andre transferred virtually into the computer and adapted to all our requirements. By the way, the original wheel is still in use and serves as a new, rebuilt rear wheel for the project bike.

In the next step, the newly designed rim is machined from the billet in our in-house production. This requires good preparatory work, because the data from the CAD sketch must be converted into work commands for the machine. The machine, which is mounted in 5 axes, performs more than 100,000 work steps and needs about 40 hours to produce the wheel.

Thanks to our own production facility we can of course determine the exact dimensions so it’s possible to plan for a reasonable double disc brake setup. Furthermore, the wheel gets a free standing hub and folded rim edges, in which the casing can be clamped later on. The tire must be driven with 4 bar air pressure to prevent the tire from slipping off the rim. This is also where the type designation of the tyre comes from: Clincher tyre from the English to clinch.

To round the production process off, the rim is polished to a high gloss and will be a further highlight besides the fork.

Fuel Tank, Engine Bracket, Engine

Meanwhile it will be clear to anyone who has followed the construction so far that our 35th Anniversary Bike is becoming really old school. 5 spokes front wheel, Springer fork and of course the drive is to be taken over by an appropriate unit from Harley history.

Andreas has spent a long time studying the different engine generations for the project bike. Flat-, Pan- or Knucklehead? Which engine can be combined with which construction style and surface finish? In the end the choice fell on a Panhead engine. We won’t give away the overall picture of the project here, but the tank and engine mount give a good insight.

The fuel tank of most bikes is not only used as a fuel reservoir or as a carrier surface for advertising purposes of the proud manufacturer. The shape of the fuel tank is also decisive for the overall line of the bike.

High up or flat over the engine, large volume with enough fuel for a round-the-world trip or just enough juice to get to the ice cream parlor and back.

The 35th Anniversary Bike gets a shapely teardrop tank (drop-shaped) installed. Welder Mike moves the filler neck to its highest point and aligns it meticulously horizontally. Later a shapely milled part will surround the tank cap like a collar. Two further milled parts cover the tank ends and let the tank merge into the frame in a visually gallant way. The parts are again polished to a high gloss in our polishing shop and then chrome-plated outside the company.

The panhead engine is held by a specially designed engine mount, once again showing the symbiosis of modern and traditional craftsmanship. The beautifully shaped milled parts were designed by our constructor André using a CAD program and milled in our machine park. The round steel arms of the holder were bent and adapted by hand under heat by welder Mike.

The 35th Anniversary Bike is built according to the old Thunderbike tradition “BUILT TO GO – NOT FOR SHOW!” Therefore Andreas deliberately chose a faithful replica engine from Luz Fuhr aka Bill from Motor Technik Mag. This makes the bike a faithful companion in every situation and a long service life is also guaranteed.

More Vintage Conversions


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