I’m working on a basic model that shows all the key components in place. This model (attached at the end) is pretty close.
Here we see two bar end shifters. One will drive a 10-speed Shimano cassette that is compatible with the Bionx electric motor hub. The left one will control the front derailed and will be used as an index shifter. The right one will control the intermediate drive, which will have fewer than ten gears. The shifter will need to be used without the detents.
The model has a hidden geometry that shows the sweep of the pedals. Generally we like to keep the controls outside of the sweep of the pedals.
The shifters fit between the pedal sweeps, but we need room there for the caliper brake. We’ll have to play with the fact placement of the shifters, which will probably be a clamp-on weldment that will move up and down the pedal tube.
From this side we can see the two clusters and the two derailleurs. This gives us a wide range of gearing, which is key for up and down hills. Even though the bike as an electric assist, we’re designing it to work well with no power at all.
The front wheel showing the Bionx electric motor mounted in a 20” wheel. A Shimano 10 speed cluster will probably go 12 to 36.
The intermediate derailleur.
We will re-order the cogs in a cluster. We’ll keep the largest and the smallest. A smaller cog (shown in the lighter color) will be used to drive the chain to the front derailleur.
The front wheel showing the two brake. A cable-operated disc brake, and a V-brake caliper.
Front end showing the disc. The disc brake caliper is not in the model. The disc itself is shown here at about 125 mm diameter.
V-brake shown without brake pads. This is a nice solution because we don’t have to worry about mounting a caliper brake close to the tire.
The pedals will be old-fashioned square taper mount. This is because we need a smooth axle for the backpedal brake (see later in this post) The model is showing a bottom bracket that is probably different than what we will use, but you get the idea.
We need a small drive cog, about 25 t. We’d probably machine off the rest of the spider.
The v-brake will be run by some handle mounted as shown.
The Bionx comes with a display and controller. I think this will mount between the pedals for good visibility. We’ll have to see if that works to get to the controls, especially while pedaling.
The Bionx comes with a throttle when you want power without pedaling. I assume the red button is stop (at least stop the power)
A closeup because I’m proud of my 3d modeling of the device.
Here’s what the actual Bionx throttle looks like.
Looks like it allows you to control everything without pecking at the screen buttons. That would be great for the Electric Handcycle.
Their new display is much smaller.
Looks more like a regular bike cyclometer, with more of the controls on the throttle (on the far right of the photo)
The red handle here is normally folded up along the pedal upright tube. When backing up, for example, to get out of an elevator, the backpedal brake will engage and stop you. So flip down the red handle, and it will eliminate the cable tension in the brake. Back up while holding this lever down. When you let go, it springs up, and cable tension is restored. (Note the older display is still shown in the model)
The backup release shown in the stowed position. The brake cable will pass by the base of this, which will be have a cam or an off center element. Rotating the lever detentions the cable that is running by. (not in the housing, and not shown)
The backup brake shown from the New England Handcycle, with the pedal removed.
The yoke shown removed with its cam follower attached. Note the brake cord where it inserts into the bottom of the yoke.
This is the roller clutch. This is why we need a smooth axle that we can get by using square taper pedals. When the crank moves forward, this clutch does nothing. But as soon as you backpedal, the clutch engages, which make the cam (that it’s pressed into) rotate. The follower rolls up the cam, and that pulls the brake cable.
Just for the heck of it, here’s how to buy one of those roller clutches.
Click below to download the model. You’ll need Sketchup 2015 or higher.