BBSHD on a Sun EZ-3 USX-HD
My build is not “totally custom” but it had a few challenges that are not likely encountered by most. I am adding motive power to a Sun EZ-3 USX HD trike.
I began with the battery. I purchased the 24Ah 52V pack. I was looking for a battery with high output and huge capacity. This met the need. The battery pack is well built with good quality connectors and very flexible cables. The included triangle bag is nicely constructed. It is a little large… For a frame mount, the extra space may improve their utility. (easier mounting, extra storage?) Because I am not mounting within the confines of a frame, I had to devise a means of filling the space with something that will protect the battery. I recovered some EPE foam from a packaged I had received. The EPE is a dense closed cell foam that provides good shock absorption and memory retention (springs back to the original shape)
I cut the EPE to fill the extra space. Because of the mounting location, I needed more protection on one side. The mounting location will be under the back of the seat, above the frame. The pack is suspended from the seat frame. The bottom of the pack (with the thick pad) rests on the top of the frame tube.
With the battery located, I turned to dis-mounting the bottom bracket to mount the BBSHD. The first challenge I had to overcome was the steering linkage. As an under seat steering trike, the steering linkage runs under the bottom bracket, from the middle of the bike to the front fork. The current configuration interferes with the mid-drive. I tried to relocate the linkage but there was no way around the BBSHD. I had to fabricate a new steering linkage.
I began the new linkage with a length of 3/4 “ EMT conduit as it was a piece of surplus material from another project. I machined a pair of plugs to weld into the ends of the tube and tapped them to accept the heim joints from the previous linkage. After a few bends and tweaks I came to a shape that cleared the mid-drive and tucked in behind the crank arm. It wasn’t pretty but it was functional. As I progressed further into the build, I became less and less happy with the results of my handiwork. I picked up a length of ½” EMT and machined a new set of plugs to weld in. The new linkage (shown below) was much more elegant and fitting of this build. I guess the first one was an opportunity to practice my tube bending.
The initial mounting of the mid-drive was straight forward, with no interference. The location of the motor is similar to most 2-wheeled bikes, under the down tube. I was fortunate to learn the BBSHD fits through the bottom bracket without modification to the frame or BBSHD.
Now I can begin to lay out the cable routing and management. I quickly learned the main cable assembly, once connected to the BBSHD, was long enough to reach my handle bars, but not much more. The brake sensor wires in combination with the magnetic switches were long enough to mount without modification. They were the only ones… I chose to lengthen the cable rather than add extensions for reliability. (fewer connectors, fewer connections, fewer opportunities for corrosion, easier to troubleshoot – In my opinion…)
My background in cable assembly provided a useful set of skills. The wiring diagrams I found on the Forums was a huge help. (Thank you to Sebs for the detailed diagrams) It provided the correct color coding and connector pin-out for confirming the work I was about to do. I began with the speed sensor, as it was an easy choice. I mounted the sensor and measured the amount of additional cable needed. I created a short cable to add to the middle of the cable coming off the sensor. I used a cordless drill to twist the wires together to achieve about 3 turns per inch (easier to manage a small group than 3 strays)
With a little planning and a LOT of shrink tubing, I was ready to install the main harness.
The handlebars for the under seat steering do not provide any reasonable mounting locations for the dash panel or user switches. Time to fabricate a mounting location. I mocked up a sample with some plastic tubing to get an idea where to bend the tubing and a starting point for the length. I worked with 1/2" EMT conduit for the tubing. (inexpensive, plentiful, easy to form, inexpensive) To attach the mount arm to the handlebar, I purchased an 8” handlebar extension that came with 2 mounting clamps. (donor parts) The conduit tubing was a little smaller than the original tube the clamps were intended for so I made an additional rubber shim to ensure a secure mount. I gave the conduit a few bends, did a few test fittings, a few more bends, more test fitting and finally arrived at the form in the pictures. They position the dash panel forward and above the right hand controls. I was able to position the throttle and selector switch within easy reach as well.
The gear sensor was also added to make shifting a little easier. The only reasonable location to mount the sensor was on the rear of the frame, near the derailleur. Because of the proximity of an adjacent cable, I had to mount the gear sensor on its edge to make it fit.
So… Battery mounted, Mid drive mounted, controls mounted, time for the chain ring. I started with the Lekkie 42T Bling Ring on the front because it was the same size as the middle ring of my former triple set. It also looks really cool. I added the provided cranks my Shimano PD-530M pedals.
Time to test the result… I powered up the unit and watched the display come to life. Slowly I began to rotate the cranks and the BBSHD kicked in. I ran it up and down through the gears, watching and listening. Everything was running pretty smooth and quiet.
I took the trike down from the stands and powered up the display again. The system made no noise or attempt to move. I wasn’t quiet sure what to expect… I mounted the pedals and began to rotate them when the BBSHD engaged. It was set on PAS 1 so it pulled gently, applying less than 200 watts, but providing a noticeable amount of effort. As the grin on my face began to grow, I tapped the “+” button to go to PAS 2 and headed down the driveway. This thing was amazing! I pedaled the length of my driveway for a few laps to listen to the bike and listen for new sounds. It all seemed good so off to the street. I rode the length of my street, shifting gears and listening for anything out of the ordinary. All was good.
By now I was really excited, I turned around and grabbed a handful of throttle. The bike quickly accelerated and down the street. 15… 20… 25… still pulling hard and I’m running out of space. I made a few more passes and called it a day, satisfied with the results.
Over the next few weeks I put about 200 miles on the trike. The BBSHD performed flawlessly. After about 100 miles, I pulled the Lekkie Bling Ring and installed the 46T steel ring that came with the kit, to decrease my cadence. I will purchase the 130mm ring adapter to reinstall my former 42T and 52T rings.
I have made several rides of more than 50 miles, without a concern. (used about 60% of the battery) Hills are no longer intimidating. Now I can ride at any speed I choose, and easily stay with the pack on group rides.
I am definitely one more satisfied Luna customer.
UPDATE:
I have now ridden more than 500 miles with the BBSHD in place and no issues with the mid-drive, battery or associated Luna parts. I have broken the chain twice (separated links - May be my fault??) I can cover more than 80 miles on a single charge using the PAS. Spend a lot of time picking bugs out of my teeth because I can't stop grinning!!!!
Cost Breakdown
| Item | Description | Cost (USD) |
| Trike | Sun EZ-3 USX HD (purchased in 2011) | $ 1,599 |
| Motor | Bafang BBSHD 1000 Watt Mid-drive kit | $ 679 |
| Battery | TRIANGLE 52v Panasonic GA 18650 24ah | $ 799 |
| Display | Luna 750c Full Color Display | $ 45 |
| Gear sensor | GearSensor for Derailers | $ 45 |
| Programming cable | Bafang Programming Cable | $ 20 |
| Brake Sensors | Magnetic sensors to use your own brake levers | $ 15 |
| Chain ring | Lekkie Bling Ring black, 42T | $ 90 |
| Charger | 52V Advanced 300W Ebike Charger | $ 80 |
| Wrench | Luna Wrench | $ 19 |
| Chain | Shimano HG40 6/7/8-Speed Chain (2X) | $ 36 |
| Cassette | Shimano 11-34 Freewheel | $ 18 |
| Tubing | 1/2" EMT (local hardware store) | $ 4 |
| Misc. Hardware | Nuts, Bolts, zip ties | $ 10 |
| Mounting hardware | Handle bar Extension | $ 16 |
| Total | $ 3,475 |
Attached Files
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