Let’s dive into the world of electric bike design. When it comes to using traditional bicycle frames for long-range e-bikes or high-speed models, the challenge is quite significant. It's a bit like trying to fit a gasoline engine into a horse-drawn carriage. While Carl Benz managed it successfully, his design wasn’t exactly robust — as shown by his wife Bertha’s famous road trip with their children. In the photo, you can see what that early model looked like.

 

Courtesy of Mercedes Benz

It doesn’t look much like today’s cars, does it? That’s because early inventors used what they had on hand. Carl Benz used a cart, while modern engineers tried to use regular bicycle frames. But this approach didn’t last long. Using standard bike frames for electric bikes often led to structural failures, just like how early engines struggled with the weight of carts. The problem lies in the different distribution of mechanical loads. Electric bikes require large batteries and powerful motors, which create more stress than traditional human-powered bikes.

Unlike classic bikes, which rely solely on muscle power, electric bikes are driven by strong motors that generate high torque. This puts more pressure on wheels, rims, and spokes. Even aluminum frames, commonly used in bikes, aren’t designed to handle such forces, especially when the motor is mounted directly on the axle. Engineers have tried to adapt these frames, but they still break down — at welds, bolts, and joints. That’s why unique e-bike frames are now being developed. Delfast followed the same path and created our own specialized frame.

But let’s talk about the battery. A high-capacity rechargeable battery is more than just a single unit — it’s a block made up of multiple cells connected together. These blocks are big, heavy, and essential for long-distance travel. Here’s what one looks like:

The size of the battery directly affects the range. The bigger, the better — especially for e-bikes meant for longer rides. A 20 km range isn’t enough for most users. So, we use a real battery in our e-bikes. And because lithium-ion batteries are flammable, we need solid mechanical protection. Unfortunately, traditional bike frames aren’t suitable for this — they’re too small and can’t hold large batteries safely.

That’s why many urban e-bikes only have small batteries, usually placed where a water bottle would go, along with a motor controller in a plastic box. It’s not very efficient and looks a bit like the first cars. But for larger, more powerful e-bikes, this design doesn’t work. The battery is too big, and there’s no safe place to put it. Plus, it needs proper temperature control and should be positioned low to keep the center of gravity stable.

This is why Delfast developed a special frame that acts as both a battery housing and a protective structure. It’s similar to a computer’s system unit — compact, secure, and well-organized. Here’s what it looks like:

This design lowers the center of gravity, making the bike more stable and easier to ride. The frame’s size depends on the battery and electronics, and it has a consistent shape. It’s more like a motorcycle frame than a regular bike. And here’s the best part — it’s adjustable! By changing wheel sizes or adjusting the seat height, the frame can fit riders from 166 cm to 180 cm and taller. Just consult your sales manager before purchasing to find the perfect fit.