Electric Helios E- Bike
Unfolded and Folded views shown below
Stock Helios Bike
Unfolded and Folded views shown below
Dahon 20" Helios (YA 20") Folding Bike with
Birkestrand "Electric Wheel" Kit (38 lbs.) with E-Kit, P/N, aluminum frame, 20 mph, 20 mile range, 500 Watt, 24 Volt System. Includes 8 AHr NiMH batteries less charger and shipping crate.
Dahon 20" Helios (YA 20") Stock Folding Bike
Frame: Custom-drawn 7500 Aluminum, High polish
Suspension: ProMax Plush (41mm)
Gearing: 3 spd. SRAM hub or 7 spd. SRAM 5.0 derailleur (stock bike)
Brakes: ProMax Polish V-brakes and levers
Wheels: 20” x 1.35” Primo Comet tires w/ alloy rims
Seat Post: Oversized, T6 6061 Aluminum
Folded Size: 28 x 56 x 81cm (11” x 22” x 31.9”)
Weight: 10.8 kg. (23.8 lbs.)
Folding Time: 10 seconds
Color: High Polish
In the near future you will be able to click on this box to buy it on-line
IMPORTANT: When ordering one of our Dahon Demonstration Machines (Item #1, from the price list), you will also need to order:

A) either Item 3 - NiMH Smart (2 Hr.) Q-Charger OR Item 4 - Solar Charger (2 Hr.).

B) Item 5 - UPS Collapsible Shipping Crate (Optional) AND

C) Item 6 - Motor Relube Gun

To order and learn more about each of these items click on the corresponding buttons above.
Click here to return to price list.
Our systems are specifically designed to bolt onto stock bicycles with minimum modifications; we do this first to make things easy, but most important, secondly, because we believe some presently developed bicycles to be works of higher art and we wish to preserve that. When you purchase the Dahon demonstration machine with our E-Kit, you do not have to do anything but, unpack, unfold, recharge and go, which we recommend as a first step if you are contemplating putting our system on your own series of bikes. We selected this Dahon model as it had the required width on the rear dropout, the brand is known and available worldwide and we liked working with the Dahon people; we are their customers only and are completely independent.

Installation of our E-Kits: Our E-Throttle clamps onto the stock handlebar, directly replacing the derailleur twist grip actuator. Twisting the E-Throttle grip CCW accelerates the bike, releasing from this position allows the bike to coast, twisting the grip CW at any time progressively actuates the regenerative braking and the neutral home position is "off". A signal cable plugs into this throttle body, is secured by a cable tie to the handlebar and threads its way back to the battery pack and controller; an integral LED glows green when power is on and changes red when the voltage is low and it is time to think of recharging or if the voltage is too high from overcharging.

The Birkestrand E-Hub with single speed freewheel (14 tooth standard) replaces the existing multispeed mechanical hub & freewheel; it is suitable in most cases, to functionally replace the approximately 2:1 ratio cog set, since the motor has about a 10:1 speed range. You can still use a multispeed crank if you prefer, and we normally leave the derailleur jockey sprocket in place to take up chain wear and provide slack side chain tension. You can fairly easily pedal the bicycle with the motor off or should the battery die, as the drag that is present is mostly from the oil seals and not from back driving the high ratio motor rotor as you might expect. On 20" to 28" wheels we prefer to use 36 spokes instead of the 28 spokes on the stock Dahon "Helios" in order to accommodate not only the slight extra weight from the batteries ( about ten pounds), but mostly for the E-Hub torque.

There is a small torque bracket from the freewheel side center hub that clips onto the frame and is secured with a plastic cable tie; we found that without this, the motor torque exerted by the shaft mounting flats is enough to spread the frame slots, destroying the rear dropouts and your bike. Consequently, removing this torque arm, and operating without it, voids all warranties; however, in order to relube the E-Hub motor, you need to remove its mounting screw in the E-Hub shaft center, but not the torque bracket itself, as this allows you to screw the Relube Gun into this hole and inject BIRKESTRAND "Superlube" into the E-Hub interior. This "Superlube" is a composite mixture of SAE 10W-30 wt. motor oil, PTFE and other additives having particles which adhere to the gear teeth surfaces, lowering their friction. You need enough "Superlube" splashing around inside the hub to: 1) lubricate the gears and 2) transfer the heat from the inner stationary motor stator windings to the inner surface of the rotating outer hub shell that spins in the oncoming air stream, which is great for heat dissipation.

At the touch of your hand, this hub motor will never normally feel hot and at the most slightly warm, reflecting its very high efficiency at all speeds in both motoring and in particular in its regenerative braking mode. If however, the unit is allowed to run out of sufficient "Superlube", the gears will start to get louder and eventually grind themselves away; the motor on hot days without sufficient "Superlube" under heavy long loading may get locally hot enough to melt the winding insulation and short itself out against the motor case, initiating regenerative braking and stopping the vehicle. As a built in safety feature, in no situation can this type of failure cause motoring. Putting in too much "Superlube" causes no harm, and at the most, if you fill it above shaft level when the E-Bike is upright, you might get some seepage or leakage out the shaft seals as the normal heating and cooling from routine operation can cause a harmless pressure buildup inside the hub. For this reason, you should be careful when removing the torque mounting bracket screw to screw in the "Superlube" Gun as oil can unexpectedly squirt out of this hole; when the "Superlube" is up to this hole, it has enough.

The practical E-Hub motor stator/gear options available for the Dahon demonstrators include the three stator windings #1S, 3S & 4S with the normal LO-speed bike gear set, but also the #4SH high speed gear set (see chart for top speed determinations); normally we ship it with the #3SL stator/gear option as this is about right for most customers and it fits many government imposed speed regulations, but we offer the other options for your trials.

Opposite the freewheel side of the motor is the integral three phase A.C. shaft plug socket. Our custom right angle plug that plugs into this shaft socket is automatically correctly keyed for phase rotation and is secured to the bike frame with a cable tie; it allows you to quickly and flawlessly change the wheel in the middle of the night if you need to. This plug is directly connected to the controller sitting atop the battery pack. We made custom light weight brackets to mount to the battery pack and bolt to existing attachment points of the frame; the brackets are designed not to unscrew from the pack and we "locktite" the mounting screws to the frame. We did not make the pack instantly removable as our thinking was reliability was the most important consideration and that one would not park the vehicle outside, but bring it inside for charging and security. Simple light weight brackets (we use chrome moly steel tubing) of this type can of course be easily made to fit any bicycle. The battery pack has a lidded compartment at its front end to contain the motor and throttle inputs plus room to connect the batteries to the controller and integral battery charging port. We purposely make it out of tough light weight glass filled nylon to eliminate corrosion and electrical problems. The integral charging port can be used both for the Q-Charger (utility) and the S-Charger (solar); it can also be used as an output port for various appliances (TV, lights, computer, etc.) at your campsite or boat.

The 8 AHr "D" cells are good for about a 25 mile range with light pedaling and in most cases the pack can be substantially recharged in about one hour as most people will not totally discharge it. One could mount the "F" cell Quad Pack for extra range or perhaps carry along two "D" cell Quad Packs.
The controllers for a given "series" are all identical because of substantial cost and lead times to make changes and do the required testing. Even though the maximum output power is controlled by and can be changed by the value of a single resistor, it cannot be effectively changed without extensive retesting and resizing of many other parts. Later we expect to introduce different "series" that will look and be identical on the outside, but with different power rating and suitable components on the inside. Basically this series, the 500W Series, is a good choice, suitable for many applications and offering a nice balance between performance and range and we hope that you will like it, but we fully expect that some of you will need different options for other applications. While we will be happy to work with you on these applications, we will continue to work to make reliability, function and cost improvements on this series.
This E-Kit can be bolted to the rear dropout of almost any mountain bike, most road bikes, many recumbents and some folding bikes; however, the 500W Series hub motors are too wide to bolt onto any known stock bicycle front forks; if you can make and/or wish to make front forks wide enough to fit our hub motors, please contact us.