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[3DRoboGuy]

Hi,
First time on the forum, so introductions first :
my name's Ian.
I'm an electrical/electronic engineer to trade and am reasonably handy.
I now live in France where nearly all the 14+ year-olds ride a 50cc petrol bike / scooter - least-ways my son and all his mates do ! Man, they're noisy, stinky, leaky and almost always needing repaired - the scooters, I mean !
 
After a bit of googling for some parts one day, I became distracted by emission control regs, scooters being banned from cities or charged for daily access to them... It seems that many thousands of older 'dirty' 50cc petrol scooters are facing premature scrapping (Netherlands / France) due to their age and the fact they are considered 'dirty'.

I'm pretty passionate (in a calm and resigned way, I think) about the planet, weather changes, greenhouse gas / small partical emissions and started to think of how I could make my son's (and his mates') scooters more eco- (and noise) friendly.

Anyways, I need a project and thought I'd convert one to electric.
I already have the scooter : 50cc chinese in good nick but with an annoying oil leak and intermittent spark problem.

My thoughts so far :
a 3Kw mid-mount AC or BLDC motor and compatible controller
a 72V LiPo battery pack - 20S8P (2Kw - can add to this later if required)
a small 12V LiPo battery pack for ignition / start-up etc
a 72/12V converter to charging the 12V LiPo pack and supplying lights and horn etc
a pair of SSR contactor(s) - 1 hi-voltage (72V) and 1 x lo-voltage (12V)

a similar acceleration & top speed (better if poss. but no worse)
20Km+ range / autonomy (with the internal 2Kw pack)
an onboard charger (4 to 5 hour charge period)
provision for an additional 2Kw of LiPo (increase range to around 40Km)

I intend to keep chassis / original equipment mods to a bare minimum - except the switch from ICE to electric and I'd like to think that as many decisions as possible will be based upon maintaining DIY simplicity / transfer to other makes of scooter. I don't really know the implications re: re-licencing / MOT / TuV but believe it to be pretty simple (having spoken to the DVLA) in the UK.  In France, it's most impossible (currently) but everyone 'upgrades' their 50cc 'scoots' and no-one blinks an eye. No idea about the Netherlands and further afield.

The 'donor' scooter is to be the 'el-cheapo' Chinese RPS scooter in great nick, the parts could always be sold on - if I can find a buyer.
I'd like to think that 800 - 1000 Euro would do the trick. Considering the current London ULEZ charges (12£50/day) this would equate to a 3 - 4 month (5 days a week) reclaim period... seems pretty reasonable IF it can be done...

I'm thinking of documenting the whole project with a view to enabling others to copy... I'm most deffinitely not a You-Tuber but I could update the forum with progress and even make a website for posterity

Does this sound feasible ? Any ideas / advice / thoughts ?

[Bill822]

I have wondered about this myself. Small scooters have considerable volume inside with fuel tank removed. Replacing the engine/transmission unit may be easier than adapting the existing part. I will be interested to follow your progress.

[MotoRyder]

Count me interested, Ian !!
Simplicity, Reliability, and the rewards of electric power are worth this conversion.
I like the values, beliefs, and hopeful outcomes expressed in your original post, and am very interested to follow along.
 

[3DRoboGuy]

Hi Bill822 and MotoRyder.
Thanks for the encouragement. Whilst I find the conversions 'grips' me with all its little challenges etc I'm not (normally) one for writing to forums / websites and social media, so I'm trying it out with this project.
Here's the scoot as it arrived.
I ordered the motor / controller over the weekend and have stripped most of the ICE kit off / out of the scoot ready for me to 'play' about with battery, motor, controller (and other smaller item) placement.
I'll take some pics and put them up later.
Again, thanks both; its great to see others interested in the idea. If you have any pearls of wisdom you'd like to share I'd be only too happy to hear them. Like I say, I live in France, am Welsh by birth and although speak conversational French  reasonably well / passably, I struggle to find others both interested and with whom I can discuss technical things easily.  Hence my thoughts towards trying the forum.
Anyways...

[Richard230]

Cute scoot.   

[3DRoboGuy]

Thanks Richard230,
The scoot's all stripped down now and ready for 're-fitting'.
I'll post up some pics later on.

[Demoni]

Great project and totally doable.

I previously worked for a company called Scoot. They do smart phone activated scooter sharing. The first 300 bikes in the fleet were Chinese manufactured electric scooters similar to what you have (image of the Scoots below)

https://techcrunch.com/2012/09/26/scoot-sf-launch/

We upgraded the bikes stock components with more reliable higher quality and performance pieces.
They ran a 1.8 kWh LiFePo4 batter in an 48v arrangement
The ran a hub motor (best option for lower power vehicles)
The ran a ASI3000 motor controller

As the bikes were classified as "mopeds" in the US they were governed by legal limitations of 4hp and 30mph (48kph) top speed. They were pretty zippy bikes quicker off the line than a 50cc 2 stroke. With that battery configuration we were seeing about 25 miles of range (40km).

There should be tons of room under the seat for the battey pack and the controller you decide to go with. As your bike uses the motor and transmission as the swingarm you will need to replace this with a different unit. The swingarms from our scoots were a simple H pattern made of steel. Should be easy enough to source or fabricate.


Good luck with the project!

[3DRoboGuy]

Thanks Demoni,
I was hoping to utilise the existing swingarm simply because I would prefer to keep the scoot as 'standard' as possible.
The 'downside' with this approach will be how to 'handle' the inbuilt 14:1 (or thereabouts) reduction gearbox that is integral to the rear end of said swingarm. The upside is that the (rear) wheel and internal drum brake will remain totally standard.
Well... that's the idea at the moment

Here are the pictures I was talking about last week - I'm a little further advanced in these...

[Bill822]

Wow. Really not much to it once the body is off.
Using the reduction gearing would allow a lower torque motor (at higher RPM, of course), but cost a little mechanical efficiency. Will be interesting to see what fits.

[Demoni]

I was hoping to utilize the existing swingarm simply because I would prefer to keep the scoot as 'standard' as possible.

Totally understandable. I was just suggesting a hub motor because it would probably be the easiest solution besides the new swingarm.

The 'downside' with this approach will be how to 'handle' the inbuilt 14:1 (or thereabouts) reduction gearbox that is integral to the rear end of said swingarm. The upside is that the (rear) wheel and internal drum brake will remain totally standard.

So the reduction opens you up to other options for a drive motor. RC motors spin at a much higher RPM that you can use directly so a reduction is required. I am not sure if 14:1 is enough, but depending on the voltage you are planning on running you might be able to find one with a low enough kV rating.

I found a youtube video I saw ages ago of someone trying to Convert a Aprilia RS50 over to EV. They replaced the crankshaft with a RC motor and used the bikes internal transmission.


Don't think he ever finished it but there is a forum post here
https://endless-sphere.com/forums/viewtopic.php?f=12&t=83316&sid=59a72f3e1f355f56490f0298e808cf00&start=25

[Richard230]

Speaking of Aprilia RS50 conversions: Here are two photos of my old 2003 ICE bike which (after the engine exploded) was bought by a fellow in the San Francisco East Bay, converted to electric power using discarded Zero components (or so I heard) and then ridden at an EV event at Laguna Seca.

[3DRoboGuy]

Hi Demoni,

You're absolutely right - hub motor and swingarm !
I think the hub motor would provide the most elegant solution provided I could manufacture a swing arm. I'm 'scared' of that and also how to replace the existing internal drum brake with an external (disc, I guess) brake and the switch (or not) from cabled actuator to hydraulic. I think if I were to be doing this as a conversion for a 10, 20 or 30+ of this particular scoot then a replacement swingarm, hub motor and hydraulic brake would undoubtedly be the better option.
To be frank, when I dreamed up the idea I hadn't taken the internal rear-wheel gearbox into consideration and that's come back to bite me... Live and learn, I guess but...

With regards to the RC motor (Aprilia RS50), I'd considered this approach (I think I'd stumbled upon the same or similar vid) but ruled it out (probably too early and without enough consideration  ) mainly due to :
1: I couldn't find a powerful enough motor 3Kw (+ at the time)
2: the motors I *did* find, that could maybe be considered, were all far to large for the available space, without a non-DIY amount of machine shop work
3: my final concern was how to 'adapt' the crank shaft to the motor shaft...
I gave up the idea as being too complex for your average DIYer on a one-off project (maybe I was wrong  )
The solution I have come up with is undoubtedly a compromise but I'll post some pics etc of the motor and 3D printed (test) bracket I've come up with. If it looks like the idea will fly then I'll knock up a bracket in 5mm aluminium and see how that goes...
More work and pics coming up...

[3DRoboGuy]

Time for an update ! I've made some progress with the motor :
The motor controller arrived !! Yaaay !!!

Initially, I removed the cylinder head. Once that was done, the swingarm was next. I found it easier to leave the swingarm attached to the scoot for the major kit removal as it helped support and hold the crankcase etc during the work. So, after the cylinder head, it was the turn of the oil pump, the starter motor and the ignition system.
I'll need to design some covers / blanks for the holes. I intend to route the motor cables through the square, oil pump hole so will make a blank specifically for that purpose.
Once the cylinder head, oil pump, starter motor and ignition system were removed I began to 'play' with possible motor positions; the crankshaft was 'annoying' me though - it seemed to always be in the way and I knew it'd have to come out for re-working or... something...
I tried all sorts of ways to remove the crankshaft... and couldn't... In the end, I used a trolley jack - I tried but couldn't move it any other way. The trolley jack did the job in a couple of minutes - live and learn, I guess !
The swingarm was placed, upside-down, on the trolley jack and 'tied' down with tie-straps all the way around the outside of the jack. The crank shaft was located centre of the trolley jack 'saddle'. The jack was slowly and pressurised, the 'saddle' extended BUT the swingarm itself was restrained by the tie-straps. Slowly, very slowly, being careful so as not to distort the swingarm itself, the crank shaft popped out - as per the centre image above. The whole lot was then cleaned up.

There simply wasn't enough space to mount the motor within the engine casing - even if I had the mind to attempt it ! Looking at the various 3Kw motors available I don't think I can get one much smaller regardless of the amount I'd be willing to pay and even then, the mechanical / machine shop re-work would be extensive (and, therefore, expensive !). In the end I began to see that the motor could be mounted in lieu of the cylinder head if I designed a suitable bracket. Out came Sketchup and then the 3D printer and in an afternoon I had an ABS bracket knocked up (in pieces - much as I would eventually need in aluminium) and welded them together with an acetone/ABS slurry. Effective !
Once I'd determined that the the bracket was correct for the motor, I went about mounting it to the 4 threaded holes vacated by the cylinder head studs - all the time being very careful not to break my template ! And, once I'd done that and noted the correct positions of the 4 x slots in the back panel for the new cylinder head machine screws. I say 'slots' - these are 4 x horizontal 20mm x 5mm slots allowing the bracket to be mounted to the crank case in a way that there would be 20mm +/- of lateral movement to enable future alignment of the motor pinion with the rear, gearbox, sprocket.
I then cut out and welded the same pieces all over again BUT, this time, in some 'scrap' 5mm aluminium I re-tasked from the skip at the local scrapyard.
Now I had something like the images below. I actually began to feel pretty pleased with myself... starting to believe the whole crazy idea might just work !!

The three holes in the bottom strengthener / spacer are to enable any water to drain more easily.
The motor is held rigid by the two pivot bolts at the bottom bracket and then the short arm at the rear of the motor (left hand side in the images) to help prevent twisting. The long arm on the top of the bracket, at the pinion / drive side of the motor allows the whole motor to rotate forwards / backwards (in relation to the scoot) and thereby enable the chain to be tensioned - much like an alternator adjuster-arm.
To be fair, after a wee bit of filing some rough edges, the whole system mounted up in 15 minutes

My job with the motor was almost done. All I had to do now was blank off the old / no longer used crankcase holes for the starter motor, crank shaft and oil pump etc being careful to route the motor cables through the now empty, crankcase and up towards the back of the scoot where I planned the electrics & controller would go !

Next is the Gearing, tidying up the electrics and batteries...

I was limited to 4 images... but... I have documented things on my (new) blog at www.ianwatts.online. You're welcome to see more stuff there...

[3DRoboGuy]

An update re: my (rather hopeful?) gearing...

I'm not sure this will work (given the gearing) but I have to start someplace !
I figure that it will be easier if I can the existing rear variator / clutch assembly (in some modified manner) to pass the drive through the gearbox to the rear wheel. I'm hoping the clutch / gearbox will be beneficial / not pose any significant problems... although some math with the ratios indicates a top speed of 11kph !! Hmm... To be frank, I think I'm going to need to re-visit this one BUT, at the current time using the existing variator / clutch assembly is the easiest way to get drive into the gearbox... I certainly can't see any way at all (bar a hub motor) of 'ignoring' or bypassing the gearbox - although I have looked at switching gear ratios within it (costly and of (at first glance) limited benefit !

So, to make a start and fit the new sprocket to the rear clutch ass'y, I stripped down the whole assembly and through-welded the sprocket to the two clutch plates (they will not be needed as the rear section of the variator anymore so...

I started by removing the nut from the splined gearbox input shaft. The clutch bell housing (right hand side in the image above) may then be removed, followed by the variator itself.
A large nut will be visible once the bell housing is removed. If you're planning on doing this yourself, then be VERY careful stripping the variator - it's under pressure from an internal spring (image below). I held the variator plates shut (their natural position under spring tension) and removed the large nut. In doing so the spring tries to release - keep that pressure applied, remove the nut fully and all comes apart as per the next image.
I then stripped the variator guide plates from the shaft and welded the 69tooth sprocket to both plates. To ensure the new sprocket remained central / true I made up a plastic spacer (again, using Sketchup and the 3D printer).

Reassembly was the opposite of disassembly (above) - apply pressure to the spring and start the nut off on its thread. Lock up the nut and refit the whole assembly to the gearbox input shaft.

If I find (as I'm pretty sure I will) that the clutch assembly is just too inefficient / isn't needed then I can always lock the clutch. I can also lengthen the gearing somewhat...
But... that's for another day !

[3DRoboGuy]

After my recent gearing work came the original / as-fitted electrics and their sorting out and tidying up.
Once again, like the strip down, this was pretty straight forward. Unfortunately, the Chinese used a strip, twist, solder and tape method of making joints within the wiring loom. They also had multiple earth / ground connections (using the strip, twist, solder and tape method) which in turn connected at both ends of a common (green) wire to the chassis. None too neat or pleasant to work with and definitely not simple to fault find. The cause of the intermittent spark did become apparent though - just a little too late for this ol' scoot !!

All the 'strip, twist, solder and tape' -type joints were removed and each item was individually tidied up. In all cases (there's not a lot of current involved here and it's all 12V) the earth cables were directed back aft to a common earth bolt.

Once the cable loom had been opened up it became possible to begin removing cables; the battery cables first, then the ignition and charge system (c/w CDI and regulator)...
At the end of an hour all that was left was lighting, ignition, side-stand down, fuel gauge, starter, kill switch and low oil cables.
The kill switch was modified (with an additional cable) from connecting the low-tension side of the spark ignition system to earth (thereby killing the spark) to being a pass through switch intended as an interlock for the controller/motor HV relays.

The fuel gauge cable was isolated as was the low oil level cable. These will be re-tasked later.
The idea is (once the scoot is 'up and running') to re-task the :
[1] low oil (red) warning lamp to be a low Voltage lamp (something like, 72V battery pack below 65V)
[2] the fuel gauge cable (full scale deflection at 0V / connected to ground/earth) to indicate battery pack voltage and, therefore, a kind of battery level indicator. An AVR Tiny will be used to pulse the gauge at a preset rate depending upon the battery voltage it detects (thereby adjusting gauge needle deflection)... Crude... but I don't like unused controls / gauges and it would be a helpful indicator whilst employing the existing panel gauge. An improvement may be to switch out the programming of the AVR to be a coulomb counter and, therefore, make it MUCH for useful... we'll see... that's a later-date project !

I have a made a small 12V Li-Ion pack (Panasonic 18650 cells again) (which will be charged by the DCDC convertor) and used to 'power' the ignition switch, via the modified 'kill' switch, and thereby energise the Controller <Enable> line and two (one HV/72V and one LV/12V) relays / contactors or, in my case SSRs (solid state relays).

All lights have been switched out for low-power LEDS, including the head light (VASTLY improved over the original headlight). The only challenge here was the standard method of earthing the indicators was 'novel' in that the Chinese manufacturer used the instrument panel indicator 'On' tell-tale as a ground for the active ones. Due to the extremely low power required by LEDs, this simply meant that ALL indicators flash when either direction is selected. The way I chose to work around this was to trace the two, left/right, indicator cables at the panel tell-tale and insert standard 1N4001 diodes into each. This way one indicator direction cannot back-feed the other. Hey-presto - all LEDs including panel lights.

Finally the new 'loom' was routed through some braided sleeving with cables exiting at their required points along the route.

Now onto the main EV electrics !!!