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My new full suspension Cruiser e-bike 250-1000W concept

14.04.2021

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As you probably already know, riding an electric bike is one of my hobbies. The decision to create my own full suspension Cruiser e-bike with a non-welded frame led me to several random test drives of similar bikes, both classic without electric traction, and those equipped with a rear hub electric system.

Turns out that the Cruiser bike offers a very special, simply unforgettable experience from the ride and, in terms of ride comfort, it is almost impossible to outperform it. An interesting and unusual appearance of the frame, wide wheels, a comfortable fit, a curved handlebar and a large comfortable saddle – all this makes this bike an excellent choice for riding both on city streets and on park paths. The upright position and comfortable seat make you feel relaxed every time you ride such a bike.

Cruiser Bikes are known for their durability and high weight, they were the most popular bikes in the United States during the 1930-50s and I think they have returned their popularity in the last decade, especially as various electric drive systems have emerged that reduce stresses on the cyclist’s feet, especially when driving uphill or against the wind.

In most cases, a steel frame is used to produce the Cruiser e-bike. This frame not only provides comfort due to its elasticity, but is also incredibly strong. It although makes the bike heavier than models with an aluminum frame. The frame prototype that I designed on my own and that is made from 6061 and 7075 aluminum alloys without welding, has already covered more than 3800 km during 2 years of stress tests in a variety of conditions. It is not for nothing that I indicate the service life, since it characterizes, in full, both the fatigue strength of the structure and the corrosion resistance of my frame.

The frame of my full suspension Cruiser e-bike concept that you can see here in the photo, is made of 3-5 mm radius corner square tube. The frame is assembled with elements made of 6061, 2024 and 7075 aluminum alloys, which are connected using Hybrid glue-rivet technology based on aircraft structural rivets and MMA adhesive. This frame design provides not only its lightness, but also strength and resilience, which are covariant with the properties of a steel frame. The frame dimensions and, accordingly, the bicycle wheelbase are designed in such a way to make it possible to lift the bicycle upstairs or transport it in a freight elevator.

My Cruiser e-bike concept will be equipped with a standard suspension front fork with a 100mm travel. After passing the first phase of prototype tests, I will try to install a vintage fork with springs or leaf springs. I have a plan to use a composite leaf spring as the main element of the rear suspension. The main advantages of such a spring are the weight, which is 65 percent lower than that of similar steel springs, and, due to the specified compression characteristics, it provides smoother and more predictable handling. A sufficiently stiff rear wheel suspension will have travel of about 80 mm and will function in conjunction with the resilient seat elements. As a result, small irregularities in the road surface will be extinguished by a comfortable seat, and larger holes by a composite leaf spring.

It was possible to install a mid-drive on my Cruiser e-bike concept, however, I preferred to keep the classic “retro” look and decided to use the Rear Hub Motor with an integrated controller. However, it should be noted that the frame design makes it possible to install the mid-drive motor on the frame. Why did I decide to install a 1000W motor? Indeed, you can use a motor up to 750W without a license in the USA, and in the countries of the European Union and the UK – up to 250W. Here I was based on three main factors:

(1) After creating a prototype, it will be important for me to load the frame rear stays to the maximum to evaluate the strength of the frame during testing over 5,000 km.

(2) According to the classic models, such a bike should be single-speed, and my range of roads includes quite steep and long climbs and descents.

(3) It was necessary to test our new battery with an increased capacity of 24.5Ah and for which the 1000W motor perfectly fit.

Thus, my full suspension Cruiser e-bike prototype is planned to be equipped with a belt drive and powered by a 1000W motor with a battery of sufficient capacity to provide a range of up to 70-80 km on a single charge. This will allow you to use your bike not only for commuting and feel free in the flow of cars, not being afraid of ups and downs, but also on weekends to leave the city and take your time to ride along the bund or travel along the park paths. When installing less powerful versions of 250-500W drives and batteries with a 14, 17.5 or 21Ah capacity, you can equip this model with Shimano Alivio 8-speed chain transmission system, which will allow you to overcome steep slopes or simply provide optimal operation, as well as to reduce the load on the battery, increasing range on a single charge.

To make it possible to move in traffic, the construction of my Cruiser e-bike provides for a large, bright LED headlight in the front part, as well as a tail light in the rear part to ensure optimal and safe conditions for night riding. To give my prototype effective braking, high-performance Tektro hydraulic disc brakes with 203mm rotors are installed on both the front and rear of my electric bike.

The functionality of my full suspension Cruiser e-bike is planned to be embroidered with a leather frame bag with a round section that is installed under the top tube, which will simulate a gas tank. I want to try installing a rear rack that can accommodate side luggage bags or trunks. The finishing touches that may be included in the standard configuration are wide fenders and a comfortable kickstand. The swept bar and comfort seat models shown here are not my final variant as I am going to test several different models to find the best configuration.

In my experience, the 27.5”-wheel diameter and the 2.7″ tire width guarantee excellent stability, and together with full suspension provide sufficient cushioning to absorb any bumps and potholes on urban and country roads while driving. Large seat, an upright seating position and a comfortable handlebar should provide the correct free body position while riding, as well as the ability to straighten the legs, preventing tension and soreness in the back, shoulders and wrists. I hope all this will make all my travels a real pleasure.

The photos of this publication shows the 3D model of my full suspension Cruiser e-bike concept. As soon as the COVID-19 restrictions are partially lifted, so that I have the opportunity to order components and make a working prototype for road tests, I will immediately do this, publish news on the website and present the real photos and videos.

Baruch Dorfman