Motobecane 50V Conversion

RoseArk

10 mW
Joined
Oct 13, 2022
Messages
23
Location
Fayetteville, AR
I got a Motobecane 50V awhile back. Cool bike. I love the style and very comfortable to ride. I rebuilt the motor, drive train, etc but the bike is just really loud riding around my neighborhood and needs more power to make it up the hills. Wife says she can hear me a half mile away. I debated when I rebuilt the bike on going electric or not. I should have.

This is the bike day I got it. It worked fine.
39A777ED-C040-477B-B40F-69D610E93AB4.jpeg

So…I had a hub motor from an Aventon Pace 500 that wasn’t being used and a spare battery. I decided to put them on the Motobecane 50V to see how it ran and how I liked riding it with the electric hub motor. I couldn’t find much info on converting one of these bikes so I didn’t want to spend much until I had fit things up and had an idea of what I was getting into. The 500w hub motor with a cheap 18 amp max controller could get the bike to 25mph on the flats. Didn’t do so well on the steep hills. Basically it performed almost as good as the 50cc gas motor.

51029F85-118B-4634-8144-B25DE2723187.jpeg

Going forward, I absolutely want to keep the look and feel of the original bike. I made a mount for the battery where the old motor mounted using some hinges and cleaned up the wires a bit. I ended up putting on more miles in a few weeks with the electric motor than I did in several months with the gas motor. Super comfortable and quiet to ride.

75B93751-02E0-44EA-BA89-2C014C53FEA9.jpeg

With the proof of concept done…I wanted to make it better. I needed to get up the hills, add disc brakes, and gears and chain to the peddles. I ordered a Leafbike 1500w hub motor and a Sabvoton 45amp controller. I also tore the bike down for a paint job which is currently in progress. I have two major hurdles to get through as well as a battery eventually. The rear swingarm has 125mm of dropout and the motor requires 135mm. I can spread the swingarm a bit to make it fit but I still have to make some adjustment to mount disc brake brackets and fit the disc brake. I am not sure how I am going to remedy that short of redoing the whole swingarm. Currently waiting on spokes to install the rim onto the hub motor and working on paint and clear coat for the bike components.

More to come in a few weeks as time allows. Goal is to have it rideable come spring.
 
If it's useful, here's a 40T converted to a middrive some years back:
https://endless-sphere.com/forums/viewtopic.php?f=28&t=8698
 
You might be able to fab up a solution like this:
file.php

By placing the (clamping) dropout extension outboard of the swingarm you may gain the extra 5mm per side needed for the wider OLD axle spacing.

(image from https://endless-sphere.com/forums/viewtopic.php?f=3&t=74899)

ETA (after looking closer at your photos): Maybe not-- the lower shock mounts interfere.
 
amberwolf said:
If it's useful, here's a 40T converted to a middrive some years back:
https://endless-sphere.com/forums/viewtopic.php?f=28&t=8698

Thanks. I hadn't seen that one. I will take a closer look tonight.
 
PXL_20221015_151201296.jpg
This is the new motor installed on the swingarm. I think a couple things need to happen. The whole motor needs to slide to the right 1/4 to 1/2 inch. The right side cover needs to be replaced with one that doesn't have a spacer before the threads. I have the cover...just need to do it. I will have to see how things line up at that point before making a decision on brakes and adapters

I am hopeful of getting some painting done this weekend.

I also should have noted in my first post that this site is awesome. I have found so much helpful info for this build and our regular ebikes.
 
Finally getting back to this. Paint is mostly done and started reassembly today. I still need to figure out wheel alignment and disc brakes but hoping to make progress on those tasks in the next few weeks.

PXL_20221105_213953770.jpg

I was able to temporarily wire everything together and test the motor and controller. They seem to be working. My plan is to run the wires into the storage compartment (open area between seat post and rear fender so that I can access them easily but still cover up when not needed.

Up next is to get some bullet connectors for the phase wires and hopefully wheel spokes arrive next week. Slow but positive progress.
 
Looks pretty good - almost like new :wink:.

You might want to consider having washers on either side on the axle, instead of one side only.
 
A little more progress this week. Pedals with bent pedal arms installed. I need some new pedal arms but they are not high priority right now. The wheel is laced up and installed. I used 12g, 95mm long spokes. I would like to find some 13g, 90 mm long spokes as the 95's were just a bit long. The wheel needs to be trued yet and should be one of the next things I work on so I can get it centered, washers installed, and figure out the rear disc brake. I have some thoughts on the disc brake but want to get the wheel straightened out before I do anything there.

PXL_20221114_164148990.jpg

I threw on an old Puch seat to take it for a slow spin. Everything but the PAS is working. I assumed the ground, power, and signal wires were just in a different orientation than the controller but switching things around didn't work either. Looking at the PAS sensor I purchased, it states it is for a Kt controller so maybe that's the issues?

PXL_20221114_165543472.jpg

On the chain side of the wheel, I spent a fair bit of time swapping out the cover. I needed a cover that didn't have a spacer before the threads. I had received the wrong cover so that was a bit of a pain. And of course, I scratched the new cover up a bit in the process. I had to shave down a bit of the axle, creating more flat area, to free up space to add washers on the inside of the swing arm without spreading the swing arm wider. Sorry, no picture. You can also see I added a 3 speed freewheel. I just used that to give me more options for aligning the chain front to back and ensure I cleared the wheel. Doesn't look like I needed to do that...oh well.

Wires are a mess yet. I am still trying to figure out where and how I want everything. Currently debating between putting all wires in the compartment between the seat post and wheel well, putting everything in a toolbox on the back of the rack with a small seat, or mounting the controller underneath the long seat and making a compartment inside the long seat to house the wires. I also need to figure out where to mount a transformer to power my headlight and taillight. Suggestions welcome.
 
For something to mount the caliper to, if you use axle-clamping torque plates similar to what 99t4 showed above, you can include caliper mounts in the plate. Then bolt the plates to the frame itself; they can be shaped along the frame-side-mounting to accomodate the frame-tubing shape and leave the most possible space between them for the motor without having to alter the frame itself.

If the plates are made of steel instead of aluminum, they could simply replace the entire dropout of the frame itself and be welded to it.

RoseArk said:
Everything but the PAS is working. I assumed the ground, power, and signal wires were just in a different orientation than the controller but switching things around didn't work either. Looking at the PAS sensor I purchased, it states it is for a Kt controller so maybe that's the issues?
There are a few kinds of PAS sensor signals. Which kind does your controller require?

Most simple ones are only three wires, with just 5v, ground, and a single signal (which can be one of a few possible patterns). Some use four wires, with two sighals, and these come in at least two different types.

https://ebikes.ca/learn/pedal-assist.html#SensorTypes



Wires are a mess yet. I am still trying to figure out where and how I want everything. Currently debating between putting all wires in the compartment between the seat post and wheel well, putting everything in a toolbox on the back of the rack with a small seat, or mounting the controller underneath the long seat and making a compartment inside the long seat to house the wires.
If you're willing to open things up (easiest at the controller itself) you can shorten the wires inside the device itself and resolder just the right length directly to the pads inside. For things you are "certain" ;) you won't need to unplug (usually anything other than battery and motor; if battery is in a cradle then even battery-cradle wires qualify), you can even skip external connectors and solder the wires from them directly to the controller PCB's pads.


Alternately there are underseat bicycle tool/etc bags that would probably hold all the excess cabling and connectors, or of course things like water-resistant project boxes, etc. (the catch with "waterproofing" is that water often still gets in via gaps in the cabling, etc., but now it can't get out.... :( ).


I also need to figure out where to mount a transformer to power my headlight and taillight.
The DC-DC could be mounted along with your controller in the small space directly above the battery in front of the pedals. Not certain, but it looks like the controller should *just* barely fit along the tp side of the battery mounting bracket strip. There should be enough room above/behind it for small DC-DC units. If there's not enough room there for the DC-DC,

Mount both of them with wiring downwards so that any water that might to get in via wiring is not going to run down onto the PCB but instead can get back out the same way.

If you haven't already done so, you will also want the motor's axle wiring to exit downwards as well, or at least have a "drip loop" pointing down from the exit hole (if that is pointing forwards or rearwards rather than downwards) so water is less likely to get into the motor housing via the wiring.

I'd also recommend a tiny drain hole at the bottommost part of the battery as-mounted so while parked it can drain anything that gets in there while riding. If you like you can use a small screw or rubber plug to close the hole when riding if you expect to encounter water at a level that might get into it directly, otherwise leaving it open is safer (you can't forget to open it and end up with water splashed from the front wheel filling the battery enough to damage cells/etc.).
 
Great input amberworf. Thank you. I am going to have to relook at the torque plate suggestion and draw some things out to see what I can come up with.

The controller uses a basic three wire system (5v, signal, ground). Hopefully I just messed something up trying the different wire combos or something needs to be turned on. I think the next thing for me to check is if I am getting 5v out of the controller.

That's a good idea to shorten up the wires and remove items I don't need. That would clean things up a lot and I know I won't use some of the plugs. If nothing else, shortening the phase wires alone would help tremendously.

I am planning for a larger battery once I get the bugs worked out which will chew up the space in that area. 28 amps coming out of that battery is not enough for my hills. But, that area could work well for the DC-DC transformer if I don't have room close to the controller.

I did not know about the orientation of the wire or battery drain hole. I will work on that this week!

Again, thanks for the input and suggestions! Lots to consider especially as I plan out my wiring.
 
RoseArk said:
The controller uses a basic three wire system (5v, signal, ground). Hopefully I just messed something up trying the different wire combos or something needs to be turned on. I think the next thing for me to check is if I am getting 5v out of the controller.
If you post a link to the specific controller and other items to be connected to it, we might be able to suggest possible connections or tests.
 
The Aliexpress page (useful text quoted at end of post) unfortunately doesn't say what kind of PAS it needs; maybe it supports several but has to be programmed via the supplied cable for some of them (or choose it in the menu of the display). The images showing the program screens don't show anytthing for this but they don't show every menu.



The most common PAS just make pulses as the magnets pass in the forward direction; some of these just don't pulse in the reverse direction, so you can check for this (to see if it's mounted backwards) with a multimeter on the PAS sensor with it connected to the controller while turning the cranks first forward then backward. The Amazon page says "12 signal output, power-assisted response speed, can automatically identify the pedal when the forward and reverse" so it could either have no output in reverse or it could have a different signal pattern when reversed. The latter isn't usually possible to distinguish from forward with a typical multimeter, so if ti has output both directions you can just try flipping it.

Also, if this is like many display-based systems with multiple assist levels, it doens't do anything in level "0" and the levels above that may vary from each other in the way they respond to control inputs. (some have a throttle-only level, usually the highest-numbered one).


The wiring on the PAS could be anything, but it is likely that the black is ground, brown is supply voltage, and yellow is signal. A KT controller wiring diagram that can use this sensor might be more certain.

Sabvoton Mqcon Electric 45A 48V 60V 72V 1KW 1500W Bldc Ebike Motor Controller SVMC7245 With Colorful UKC1 Display and Throttle

The function for SVMC7245-APT protocol controller:
Hall Plug, PAS(5gear), Throttle Plug (0-5V), Ignition, Speed Limit, Anti-Theft, Low Brake 0V, Reverse, 48V-72V Light Power, UKC1 Display Wire, USB Cable, Flux Weakening Current.

1 Model: SVMC7245-APT
2 Available Rated Battery Voltage: 36V/48V/60V/72V
3 Peak Battery Voltage: 95V
4 Available Motor Power: 500W - 1500W
5 Peak Phase Current: 135A
6 Peak DC Current: 45A
7 Working Communication: Hall Sensor
8 Size: 190mm * 98mm * 65mm
9 Weight: 1.2 kgs
10 Throttle Working Voltage: 0V - 5V
11 Mosfets Detail: 12 FET
12 Case Material/Color: Aluminum /Gray
13 Controller Design: Sine Wave Brushless DC
14 Support Programmable by PC & Phone
15 Suitable for spoke/in-wheel motors with 120° Phase angle. It may NOT work properly with a mid-drive motor

TFT UKC1 Display
1 High-contrast 3.5inch IPS colorful matrix screen.
2 Suitable for low temperature,Max -20℃.
3 The screen can be freely switched horizontally and vertically.
4 Speed display : AVG SPEED, MAX SPEED, SPEED(Real-time).
5 Kilometer / Mile : Can be set according to customers' habits.
6 Adjusting 5 levels backlight brightness:1st level is the darkest, 5th is the lightest.
7 5-level Assist.
8 Mileage indicator : Odometer/Trip distance/ Clock/ Riding time.
9 Error code indicator.
10 Speed limited can be setted.
11 USB charging port,500mA/5V.
 
Wonderful conversion, RoseArk. That Leaf motor should get you moving down the ride nicely. Amberwolf’s suggestion about shortening the wires straight into the controller was a good tip for a super-clean build. I’ve never taken it that far, and have just snipped and shortened the wires outside the controller. It all gets hidden once the wires get covered in a loom, sleeve, or spiral wrap, anyway.
 
RoseArk said:
I am going to have to relook at the torque plate suggestion and draw some things out to see what I can come up with.
Looking at your photos of the swingarm again, it looks like you could incorporate the lower shock mount bolt into the plate, as an important anchoring fastener. Might (probably) require a longer bolt/shoulder bolt? Ideally, it could take the place of the u-bolt/pipe section.
file.php


Added bonus: make it a pinchbolt-clamping dropout, for the best in axle stabilization.
lmm6Vl.jpg
 
99t4 said:
RoseArk said:
I am going to have to relook at the torque plate suggestion and draw some things out to see what I can come up with.
Looking at your photos of the swingarm again, it looks like you could incorporate the lower shock mount bolt into the plate, as an important anchoring fastener. Might (probably) require a longer bolt/shoulder bolt? Ideally, it could take the place of the u-bolt/pipe section.
file.php


Added bonus: make it a pinchbolt-clamping dropout, for the best in axle stabilization.
lmm6Vl.jpg

I just had that "a ha" moment and totally get what you are saying now! Took me awhile but I got there. That's a helpful suggestion to incorporate it into the shock mount and pinch it closed. Thanks!
 
PXL_20221210_232051106.jpg

Well it's been several weeks. Made some positive progress and some negative progress.

The PAS system is working. Ended up just ordering the correct sensor from where I got my controller from. Should have done that in the first place. I did have to 3D print an adapter to make it fit but that was pretty easy to deal with. New, straight pedal arms installed as well.

I disassembled the old long seat. Long story short, nothing but the frame was salvageable, and that needed work as well. By the time I would purchase foam and a cover, it was cheaper to order a new, knock off, from France. It's nice, comfy, and will get the job done for now.

The seat issue kind of forced my hand on how I am mounting the controller and tucking wires. I had an old metal box and am installing that on the back rack to hold the controller and wire. I ran the wires up from underneath and everything fit although a bit tight. I hope to get it mounted to the rack this week and start removing excess wires that I won't need. I think shortening up the phase wire leads from the controller will help a lot. I suspect I will also need to add some vent holes in the box for cooling. I still need to run a new power line from the battery to the controller and get the line tucked away.

Now the bad....I had an original Motobecane speedometer that I had just rebuilt. Put it on the bike for a quick test drive to verify it was working but forgot to tighten down the axle fully. Sadly the speedometer drive came lose and wrapped around the speedometer cable. Cable and drive both toast. Oops. I have a backup speedometer drive and should be able to get a new cable if I want to use it. I was trying the old speedometer as I wanted to see about using the bike with no electronic display. While going back and forth with the display connected and not connected, I managed to connect the display to the controller while it was on and fried a ground wire on the display harness. Again oops. Definitely fixable...I just need to get a new pin for the harness. I can ride with no display so not a huge deal. Unfortunately, I may have also mucked up a hall sensor or something. The motor/controller always started and worked with no issues. Now, I frequently have to connect to it with my phone and do a quick phase test to get the bike working. Doesn't happen all the time though...just if it is been sitting for several hours. I am going to fix the display pin and then start trying to figure that out.

I haven't started on swingarm upgrades and rear brakes or connecting the lights. Just haven't had time.
 
You should see if Arkansas will let you have an Antique tag for that bike. The last section of the rules allows for certain modification if they have to do with safety. Switching from 2 cycle to Electric makes the bike "less polluting, improves air-quality and is safer for the environment".

... the worst they can do is say "no".

https://www.dfa.arkansas.gov/specialty-plates/details/antique-vehicle-license-plate-current

P.S.
Belle œuvre d'art.
 
Nice conversion! Are you gonna keep the standard battery pack hanging off the front, or are you gonna replace it for something bigger/different?

Also, good to know a 500 watt hub is similar in top speed to a 50cc two-stroke. It's always hard to explain equivalent eBike power well to people.
 
You might consider adding 15ml of ferro fluid to the Leaf, they go together like peas and carrots.

https://www.electricbike.com/ferrofluid-shell-fins-direct-drive/

In order to drill and tap a hole through the ends of steel clamping torque-arms, the steel plate has to be very thick, which makes it hard to cut. I was searching for a method to clamp the ends on a piece of plate steel that was only 3/8ths inch thick (9.5mm).

file.php
 
LewTwo said:
You should see if Arkansas will let you have an Antique tag for that bike. The last section of the rules allows for certain modification if they have to do with safety. Switching from 2 cycle to Electric makes the bike "less polluting, improves air-quality and is safer for the environment".

... the worst they can do is say "no".

https://www.dfa.arkansas.gov/specialty-plates/details/antique-vehicle-license-plate-current

P.S.
Belle œuvre d'art.

Thanks. It currently has a plate…so might be easier to switch to an antique plate. Will check it out.
 
spinningmagnets said:
You might consider adding 15ml of ferro fluid to the Leaf, they go together like peas and carrots.

https://www.electricbike.com/ferrofluid-shell-fins-direct-drive/

In order to drill and tap a hole through the ends of steel clamping torque-arms, the steel plate has to be very thick, which makes it hard to cut. I was searching for a method to clamp the ends on a piece of plate steel that was only 3/8ths inch thick (9.5mm).

file.php

Oh I like the clamping torque arms! What are / where do I find those brackets that the clamp bolts run through? I don’t know that I have seen something like that before. Am I also seeing a little notch on the plate helping prevent the clamps from sliding back?
 
RoseArk said:
What are / where do I find those brackets that the clamp bolts run through?
H'mmmm ... looks like repurposed steel cable clamps.
https://www.amazon.com/dp/B08H7XL6DL
51q4AxzMkmL._SL1001_.jpg
 
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