Swytch Kit 1/15/22

In my last post, (1/8/22) I talked about e-bike mania and wanting to join the crowd to extend my riding capacity - hills seem to be getting longer and steeper. I also noted that Santa came through with a Swytch Kit from England - an e-wheel that provides assistance based on the rider's pedaling effort. In this post I will walk you through the Swytch Kit installation process on my three year old Specialized Cross Road Sport.

STEP 1 - Read the installation manual. In fact, read it through before you begin, watch some of the installation videos available on You Tube, and then read the manual again as you go, because there are easily missed details that will need your attention. Then plug in the battery back so it is fully charged when you are ready for the test run.

STEP 2 - Move your bike's front tire and tube to the motorized rim, being careful to maintain the direction of roll on the tie. Then install the motorized rim on your bike orientating the motor connection on the left and pointing downward, and properly placing the spacer washers so the motor connection is not pinched. Remember to adjust the brake pads to the new rim. (If your bike has disc brakes, you will need to transfer the disc to the new rim when you transfer the tire and tube.)

STEP 3 - Install the batter mount on the handle bars, making sure the lock and release mechanism works and it does not interfere with any accessory (e.g., bell, light, cell phone holder). Plug in the wire connection with the motor matching the arrows on the plugs, after determining the path you want the wire to follow over the frame. Use the provided zip ties to hold the wire in place on the bike frame.

STEP 4 - In a Swytch Kit, a controller, which is in the batter pack (on most e-wheel conversions the controller is separate and needed to be mounted separately on the frame), determines how much motor assist is needed by the rider by reading the rider's pedaling effort. A disk, which has small round magnets embedded in it, is placed on the left side of the crank, and an accompanying sensor, are primary in that process. Because bike crank shafts differ in diameter and the clearance between the left pedal's shaft and crank housing differ from bike to bike, installing the disk and a sensor can be complicated. On my bike, the crank shaft is large (about the diameter of a nickle) and there is significant clearance with the crank housing (5 mm). I selected the appropriate center insert for the disk based on the clearance, enlarged the center hole on that insert to match the diameter of the crank shaft, and used the provided pedal shaft support so the disk did not slip.

The most challenging part of this step, at least on my bike, was positioning the sensor so it read the small round magnets on the disk. The seat post and the lower frame post that connect to the crank housing are the primary candidates for the sensor. But the seat post had a derailleur clamp in the way and the lower frame post was triangular. The far from simple but best option was to fabricate a flat area for the sensor in between those two posts. I did so from a piece of white aluminum fascia, held in place with two hose clamps wrapped around the seat post. I first made and fitted a pattern from a note card, traced it onto the aluminum, cut it out, made a few adjustment in size and shape, and attached it.

Step 6 - The sensor needed to be positioned so it read the passing small round magnets on the disk. The sensor was initially placed by sight and held in position on the aluminum surface with the two sided tape that came on the sensor. Also, before the the e-wheel was ready for a test ride, the battery was placed in the holder, the sensor position was confirmed (a small red light on the sensor blinked as each magnet passed the sensor), a 3M Velcro strip was placed across the sensor for greater support (Velcro so the sensor could be removed if its position needed to be adjusted in the future), and a check was made that all of the new wires were securely tied to the bike's frame with the zip-ties.

2/11/22 Up-Date - On the initial early January test ride around the neighborhood (limited to a couple of blocks by COLD weather) the Swytch Kit appeared to work well. But a real-world 10 mile test ride made possible by an unusually warm mid-February day, showed the power assist from the e-wheel was not consistent. The issue was the alignment of the magnetic disk. Because that disk was positioned on a slight angle, the distance between the magnets on the disk and the senor was too large for about half of the disk's circumference. Once the disk alignment was corrected, the Swytch Kit worked perfectly proving a consistent assist proportional to the rider's peddle effort.