Chinese Pit Bike Conversion | Nucular 12F | LMX-Motor 60mm | 18s 16Ah LiPo

[Amaxophobie]

Finally a new project!!

So after looking on eBay every now and then I finally found a suitable pitbike with broken engine that would fit my needs. On this model I especially liked the engine mounts as these are two straight arms facing forward. This makes it fairly easy to adapt new parts such as motor mount etc. I bought it for a bit overpriced 80€.

Here are a few pictures from the eBay seller:




After receiving all the parts I built it up just to see if the bearings had to be replaced and everything was intact.
As Iwaited for my LMX-motor to be delivered I quickly modeled it up in CAD and 3D-printed a lightweight model with the original dimensions to find a suitable place in the frame.



Afetr that I removed all the dirt and old paint from the parts and prepared it for a new paint.



For the color I chose a matt black. After greasing all the bearings and putting everything together it looked only a bit less ugly than before

 

[John in CR]

Looks like a nice little donor for an e-conversion. If the swingarm is steel, I'd definitely weld the motor mount to the swingarm in front and below the pivot point. The purpose would be to eliminate chain issues and make it as quiet as possible, as well as obtaining the anti-squat attributes of motor attached to the swingarm. Plus it would give you more room for batts.

 

[Amaxophobie]

Yes, the swingarm is steel. I thought about mounting the motor under the swingarm too because of the chain tension but had to erase that idea due to lack of a welding machine. Another problem is that the motor would be very close to the ground and would easily hit obstacles in rough terrain.

Let's go on:

So the plan was to use 30mm x 30mm aluminium profile for the motor mounts and batteries. This makes it really easy to adjust lenghts without drilling new holes.


I took measurements from the wooden motormount and modelled it in CAD. I made a long hole on top because i wasn't sure about the exact position and wanted to have the opportunity to slide the motor back and forth until I was happy with it.


Later that week it was then CNC milled out of 7075 aluminium. Below is a quick test fit with the motor which finally came in the mail that day.


Next step was to fit a 219 chain ring on the original rear hub. The bike came with a 420 chain ring mounted which inner diameter was slightly smaller than the diameter of the 219 go-kart chain ring I ordered.



So I made an adapter that mounts on the original hub with 4 M8 screws and had 6 x M6 threads for the 219 chain ring. The difficulty here was that the motor couldn't stick out more to the side, so I had to make the adapter as thin as possible to maintain a straight chain line. Limiting factor was the head height of a M8 Bolt (8mm). After searching the internet I found M8 screws with very thin heads used for break discs on motorcycles. Perfect!!



And after waiting two more days the adapter was also CNC milled out of 7075 and fit nicely and snug on the hub.

 

[skeetab5780]

sub'd GL on the build looks fun

 

[Amaxophobie]

Let's go on with the battery housing:

With the 30x30 aluminium profile and the help of 90 degree connectors I made up a simple L-shape cage.




Batteries will be 3 x 6s 16Ah Multistar with which I am pretty happy. I already used them on my kick-scooter project and in terms of size and weight (1,5kg each) as well as performance (max. 0,02V cell drifting) they are just great if used with 6C constant and 12C peak (they are claimed with 10C constant and 20C peak).



I was so on fire to try this thing out but sadly the nucular 12F I ordered was already shipped but not delivered. So I soldered on new connectors to the motor and connected my trusty VESC6 in unlimted mode. With a lot of duct tape I secured two of the batteries (VESC is only 12s) and the controller. Only thing missing was connecting the two 219 chains I ordered and trimm them till they fit. And after carrying this heavy thing down my apartment stairs (I live in first floor) I finally took it for a first, short spin.



Here is a screenshot of a video so you can see the size of this tiny bike:



Of course the power with 160A phase and 120A battery was ... let's say not surprising. But it gave me a rough idea of the handling and feeling of this small bike. With 12s and 14/63 gearing it went 48 km/h or 30 mp/h with okay acceleration.

 

[boars]

Oh wow, my sense of scale was hugely out with this bike - I didn't realise it was so small.
I then went back through your pics and paid more attention, it's bleeding obvious when you look at all the other objects like chairs.

I really do only see what I want to see haha

What a cool little beast though, looks like a bunch of fun!

 

[Amaxophobie]

Don't worry, that's not the first time I heard that sentence :lol:

The size is right between a normal bike and a pocket bike. It has a seat height of about 780mm which actually makes it quite comfortable to sit on. As I'm about 1,90m tall I look a bit like a grasshopper while riding this thing but thats okay. The bike looks funny and me on it too so thats a perfect combination 8)

Here is the small video of the first ride I took the screenshot from.
Don't expect anything. It's just driving in a circle and testing the brakes...

[youtube]O8Q3bveO6yM[/youtube]

 

[SlowCo]

Nice work!
Get a decent road tire on the front rim (14"?) and you'll have a Supermotard :thumb:

 

[ZERONEST]

great project! thinking of also converting a pit bike myself but running a qs motor 120 70h as it already runs the standard pit bike sprockets to match the rear. also running 18s and 16-20ah, do you have any idea on what range you might get from your pack yet? or too early to say yet?

:thumb: :thumb: :thumb:

 

[Amaxophobie]

@SlowCo
Thank you!
Exactly, the front rim is 14" and the back rim is 12". I intend to use it mostly offroad so the plan is to change the back tire to a cross-profile. 200 meters from my apartment there is a big forest with lots of trails and paths. So choosing between road and dirt was not that hard :wink:

@ZERONEST
Thank you!
I thought about that motor too but it would be too overkill for this small bike. Also the size would be a problem. The distance between the two straight arms on my frame is only 220mm wide. With an overall length of 215mm the QS would stick out to one side in order to maintain a straight chainline.
And last but not least the LMX-motor is more capable than one would think. For the size and weight of the bike (55 kg) it is the perfect motor in my opinion. Also the small size makes it look underpowered and I really like understatement 8)

I uploaded a new video to my youtube channel with the nucular 12F installed. Build pics will follow in the next days.

[youtube]cm63kwO2VPo[/youtube]

 

[SlowCo]

Time for a knobbly tire then: https://www.ebay.de/itm/KR-12-Zoll-...664685?hash=item259e3e2c6d:g:GQoAAOSwKrhVaAl8

 

[Amaxophobie]

As you saw in the last video the nucular controller finally arrived.
Initially I wanted to place it in front of the batteries and behind the front wheel for cooling, but after reading a bit in the nucular controller thread on ES, it seems that it's very hard to heat this thing up. So I decided to mount it between the battery casing and the motor where it will get almost no airflow and see if that's enough. If not I can easily swap the position later.
Advantage of the mount as it is now: the controller and cables are not visible. All the connectors and colorful phasewires are located under the seat, which only takes two screws to remove.


Here you can see the (really small) nuc 12F mounted to the backside of the battery casing. I also added hard foam plates in the battery case for dampening and to make room for the heads of the M5 cylinder head screws that hold the 1,5mm aluminium sheet.



Here you see a picture from above without the seat. The only cable going to the front is for the display. Throttle and regenerative breaking throttle (left) are connected directly to the display. The hallsensor connection is currently done with 2x 3 pole servo-connectors but will be changed to something waterproof 6 pole.
Any idea for a good one?




I then cut a front cover for the batteries and mounted it with knurled head screews to realise a tool free battery installation.
Here it is all together:





Then this thing was finally ready to show me it's potential and power. I started slow and upped the amps more and more until I reached the limitation of the controller (250A phase and 200A battery). Testing this was so much fun!
With a gearing of 14t sprocket to 72t chain ring (i = 5,14) I reached around 71 km/h on flat without flux.
According to my calculations the back wheel gets around 189Nm of torque (theorectical value, without efficiency drawbacks).

In the seccond clip of the video I posted before you can hear the chain making a "click"-noise. That is because I designed the motormount moveable and the motor had so much torque that it pulled itself closer to the backwheel. Despite I secured the mount with 4 M8 screws. Memo to myself: don't make the motormount moveable again :lol:

I then also painted the aluminium side sheets matt black so it looks like this:
View attachment 1

 

[ZERONEST]

@ZERONEST
Thank you!
I thought about that motor too but it would be too overkill for this small bike. Also the size would be a problem. The distance between the two straight arms on my frame is only 220mm wide. With an overall length of 215mm the QS would stick out to one side in order to maintain a straight chainline.
And last but not least the LMX-motor is more capable than one would think. For the size and weight of the bike (55 kg) it is the perfect motor in my opinion. Also the small size makes it look underpowered and I really like understatement

Great stuff looks like a fantastic build! now if you finished the bike with some plastic fenders and dirt rear tyre I think it would be awesome!

Ive just received my qs motor and it does fit!( My frame is different to yours though more of a stock crf50 pit bike frame) and you are correct it will stick out one side more than the other but its not as issue as the original 4 stroke engine crank case does too, that said your motor really does look like a great fit for you bike and plenty of power too!

I have no idea if my bike will be over powered then as its the qs 2000w motor and only on 10" wheels hahaha

Will be starting a thread on it soon!

 

[Amaxophobie]

@ZERONEST
Oh, I read your motor designation wrong :lol:

I thought you meant the 138 70h 3000w QS motor, thats why I wrote it is too powerful for such a small bike. The motor you got I think is pretty good compareable to the one I have. It's perfect in size and weight for a pit-bike!

Hope you'll have a lot of fun building it!!

 

[Amaxophobie]

So let's begin with solving the problem of a moveable motormount. The chain jumped of around 4 times now and the last time it snapped the 219 chain master link which lead to the walk of shame with an oily chain in my hand

Instead of modeling a new mount in CAD for the CNC I chose a faster and more easy way and just drilled a hole through the profile. Then with a longer bolt I sandwiched the mount, the profile and the frame-arm.

Now this mount is rock solid and won't move anymore!






After lots of searching online I finally found the name of this bike/ frame:
It's a Orion AGB 29.

Sadly there weren't any plastic kits available for this version as it was produced back in 2006. After searching some more I found a kit (black of course) that looked like it could fit somehow with some modifying.

The package came in the mail and after test fitting I quickly realised that except for the front fender nothing fits to the bike. I thought about shipping it back, but wasn't sure if I would find something better than that.

So I started to carve. I cutted big parts of plastic away with a cutter-knife, drilled new holes, cutted new threads in the frame and after around two hours it came together like this:





View attachment 6

As you can see in the pictures I also changed the rear chain ring from 72t to 82t.

The past days when riding through the woods I always checked the speedometer to determine how much top speed I actually use on my long 14t/ 72t gearing. The answer was: I never went faster than around 70-72km/h althoughthe bike could do 80 (with flux).

So I made a simple calculation in excel to try out different chain ring sizes. Luckily the 219 chain rings are very cheap (7€ each) and go up to 97 teeth which makes it really easy to find the perfect combination.



So I found out that a 82 teth chain ring would fit my needs perfectly. Around 62 km/h without flux weaking and around 15% more with flux which adds up to around 71km/h. Perfect for my needs and more torque at the wheel!

What's next?

1. This thing defintely needs a front brake. It's quite stupid to just have a rear brake on gravel roads :lol:

2. I ordered a dirtbike tire to get better grip on loose ground.

3. Mounting a temp sensor on the motor windings. Just touching it from the outside isn't a proper way to feel whats going on inside

4. Making it more resistent to water. Especially in the front, the dirt easily finds it's way on top of the battery so my plan is to close all the gaps with rubber sealings and aluminium sheet.

5. Get some footpegs. Not only do they look better than these aluminium plates, they also don't cut in your leg when you slip

See you next time!!

 

[technotony007]

good effort fella :thumb:

looks a lot of fun, to ride.

how long does battery last ?

what sort range do you get ?

how long to recharge ?

regards

tony

 

[Amaxophobie]

@technotony007

Thank you!
It definitely is! And to make it even more fun I preordered the bigger 24F nucular controller that has double the phase amps (500A)

Runtime is heavily dependant from your driving style and enviroment. I live in a hilly area so if you always go WOT you get near 50 Wh/ km. As my Battery has just around 900Wh of energy the range results in around 18km.
But more usual it is around 35-40Wh/ km especially when riding tight trails. On the street the range is more like 30km.

The battery consists of 3 separate LiPo-blocks that are not connected to a BMS. For recharging I take them out of the battery housing and connect them one after another to a single 500w LiPo charger (ISDT Smart Charger SC-620). One battery needs around one hour with balancing to reach 4,15V/ cell. So all in all 3 hours of charging.

 

[Amaxophobie]

Installing a front break

So I ordered this brake which I thought could fit:


Turned out: it doesn't fit at all :lol:

The brake has two pistons but only on one side and was therefore floating mounted on a bracket. As I don't want to entrust my life to this chinese rubber I decided to made a hard mount. I know that this will result in the wear of only one brakepad but as I just need this thing for emergency braking it's okay.

So I started with dismounting the brake. I took measurements while holding it onto the front disc brake, created a 3D-model and printed it for a test fit.
View attachment 5
View attachment 1


Then the difficult part was to get a parallel contact surface to the brake disc on the outside of the brake. That way I could mount them onto the fork with a custom bracket.
The setup was simple: Screw the disc on a piece of wood, clamp the break around it and make sure it holds tight. Mount an angle grinder on a slideable piece of wood and work out a fiiting height with different thick plates.
View attachment 3
View attachment 4


And the result is surprisingly good:
View attachment 2

The rest was simple: laying the 3D-print onto a piece of 6mm aluminium and draw around it, mark the holes and cut it out.
Turned out quite good, only the braking line comes out in a weird angle but I can live with that. Braking power is as expected: you can break very hard but it just isn't enough for a stoppie

 

[Amaxophobie]

Adding a temp-sensor to the LMX 60mm motor

Together with the nucular 12f controller I ordered a NTC10k temperature sensor to mount it inside the motor, as the stock one doesn't come with this feature. It was my first time to open up an inrunner so it took a bit longer than I thought.

First step was to remove the long M5 screws that go all the way through the motor outter shell.



Then I took a small flat head screw driver and with the help of a hammer I carefully went into the bond joint between the endcover and the main shell. I did this a couple of times all around the endcover. Bit by bit it came lose and finally I could remove it by hand from the axis.

View attachment 8


Next I searched for a three phased thin cable with isolation rubber around it. I think it was from an old thumb throttle. As the temp sensor only needs two phases the red one was cut.


View attachment 5

Filing a small recess allowing the cable toexit the motor.



I originally bought temperatur resistance glue to glue the sensor on to the windings but turns out the cord was just as good at holding it in place.

Plus there is no fluid (-> glue) between the sensor head and the copper so the heat readings should be in their purest form.



Done!

As I wanted to play around more with gearing and the 219 chainrings a very cheap I ordered the biggest one I could find on the internet. It had 97 teeth and was bigger then expected



With a total diameter of 24cm (9,5 inch) it was exactly half the diameter of my rear tire.

View attachment 1




I went out and tested the acceleration as well as the top speed:

[youtube]abqQnRxfOFE[/youtube]


0-50 km/h in around 2,9 seconds. Front lifts very easily up to around 35 km/h. For the acceleration test I leant over the handlebars to get the front wheel down. It's very fun to ride with this much torque but a bit too slow for me.

As mentioned before I ordered the nucular 24f with double the phase current (500A). This way I can have very high torque and top speed close to 80 km/h.

Next thing to do is installing a dirt tire on the rear rim.

 

[Amaxophobie]

New rear tire and front splash-guard

The knobby tire came in the mail and it was time to install it. As it gets more and more wet outside the michelin street tire gets pretty much useless. I would have changed it earlier but there were just too many more important things to do on the bike. But finally it gets the tire it deserves




Next thing was to build a front guard to protect the batteries from water and dirt. The tire shoots all sorts of stuff directly at the cable connections and on top of the batteries. Of course it would be easier to make a watertight box with just one connector sticking out but for now I don't need this kind of waterproof. Also it would take one more step for installing and also for charging the three individual LiPo-packs.
Going through smaller puddles without worrying about water coming in is enough for me. For now :wink:




I started to cut out a piece of cardboard to get the dimensions of the frame right. Then layed it onto aluminium sheet and sawed it out. With the help of clamps and a piece of wood I bent it step by step to the angle of the frame and aluminium profile (around 80 degrees).

View attachment 11



Then I drilled holes for the M5 bolts into the sheet.

View attachment 7

Then I had to take apart the front batterie housing to mount the profile nuts for the bolts. I also drilled two holes in the frame and threaded them with M5.
After a paint job with a different style matt black ( ) I mounted it and it fits perfectly.

View attachment 6

Now that the front was protected the next step was to make a mud gard for the back wheel. It was wet but sunny that day so I decided to do it temporarily with some insulation material i had laying around. This will be upgraded to thin and flexible plastics soon.
Looks ugly but worked really well protecting damper, controller and motor.

View attachment 5


I went riding shortly after and took my helmet cam with me to film a part of the forest roads I take for testing.
Top speed of 69 km/h looks slow in the video and also feels way too slow on these open roads. But gearing it faster would take away too much torque. 250A phase current just feels far too little


[youtube]54ItgscWtdg[/youtube]


At the end I tried to climb up a very slippery road. The wheel didn't get grip and accelerated very quickly resulting in the chain waving on the underside, jumping a teeth in the chain ring and finally jumping off. The chain was a good bit too lose and I don't have a spring loaded chain tensioner at the moment. This will be one of the next upgrades.

The chain looked okay after that incident and was slack enough to mount it back on the chain ring without tools. It seems that the only damaged part was just one chain link. Luckily for me I was able to drive home carefully.



Back at home I checked the inner parts and all of them were dry. On the pictures below you can see how well both of the protections worked.

View attachment 3View attachment 2

Next thing will be upgrading the foot rests, making a proper rear mud guard and making a chain tensioner.

 

[ZERONEST]

That's coming along great!, you definitely need some footpegs!

I used to use an old large innertube cut open for rubber to use as a rear mud guard to protect the shock

 

[SlowCo]

This bike is getting better and better :thumb:

 

[Amaxophobie]

Thank you!

New footpegs and some ideas for a chain tensioner

One of the few things that survived from the first test ride till now are the "footpegs". And even with quotation marks they doens't deserve this description. They cut in your leg if you loose traction and put your foot down for stability, you slip down if you try to stand and I don't even wanna talk about the great experience I had when they became wet :lol:

It was time for an upgrade!

After some searching online it seems like no one sells a complete footpeg-module. Including the footpeg itself, leg spring and mount. That's because the 45° holder is already installed on most motorcycles. So while thinking about a whole DIY solution I came across this product on amazon for 15€:



It had the spring mechanics already included and is mounted by a single M8 bolt. Maybe not the best grip and we will see how well it handles jumps but a lot better than my current setup.

I then designed a custom mount to bolt it on my aluminium profil. Benefit from this solution is the possibility to slide it back and forth to my liking.

View attachment 10

After a few days passed it came out like this:



And after sandblasting away the milling lines:

View attachment 8

I wasn't sure about painting it also matt black as I really like the look of sandblasted aluminium.

View attachment 7

The footpeg mount on the motor side had to be slightly shortened because the motor mount reaches over the aluminium profile a bit to get the correct chain line. I really like the look, unremarkable and sleek.


View attachment 5


Next thing to fix was the chain tension. On the underside I currently have a simple rubber wheel to guide the chain. But because my motorshaft is in line with the swingarm and rear axle when the bike is unloaded my chain tension will get more and more loose when I compress the rear shock. That's not good because chains do weird stuff when you let them choose where to go :?



So I started to design a simply spring loaded chain tensioner:



As you can see on the right of the picture my intention was to mount a tension spring on the moving arm and connect the other side to the swingarm. But this makes the system prone to error as I could easily destroy the spring with my foot while driving. So my next idea was to use a leg spring instead. As I have no experience in this kind of springs, things will get very interesting :lol:

To test it all out I printed the parts, mounted the bearing and tried my first spring design with 1mm springwire.

View attachment 3
View attachment 4


It works but the force of the spring is to weak. Will try different spring wire diameters this week.

 

[MorbidlyObeseKoala]

Are you nervous those aluminum channels will bend under the stress from your weight during impacts? Aren't foot pegs usually mounted to those 2 holes in the lower part of the frame on pit bikes?

 

[SlowCo]

Wouldn't a spring mounted like this be stronger and better (moving up with the swing arm)?