Building a pocket bike with CA120-70 [8.6kW]

[olaf-lampe]

Hi guys,

a friend of mine is driving in the dutch mini bike race series for a few years now. He also builds his own frames:

65cc Puch motor w 15HP limited power

pocket%20bike.jpeg (22.29 KiB) Viewed 7220 times

He was kind enough to sell me an old frame and helps me to convert it to electric.
It'll be driven by the turnigy CA120-70 running at 8s/53AH Kokam cells. Controller is still under investigation. I ordered the watercooled turnigy aquastar 240A. Another option is a (soon to be modded) 18 FET infineon controller I already have as spare for my recumbent.

Today I started to take some pictures to discuss the packaging of components:
The motor will drive an adjustable centrifugal clutch. I'll use a 4:1 - 8:1 single reduction with common mini bike chain and sprockets.
Target speed is 35-70km/h depending on the race track.

motor_side.jpg

ca120 above the rear frame

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The 8s battery will fit between the tubes of the frame. I have to cut off the Puch motor mounts to place the battery a bit lower and move it closer to the rear tire. I will also mount them with the connectors upwards. The controller will fit under the seat. Waterpump and other stuff will be placed under the fake tank. Radiator will be in front of the battery or also under the seat.

ground clearance.jpg

8s kokam 53ah between the tubes

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To cover and protect things, I have Polini side covers. I have to modify them to suit the different airflow.

ground clearance w cover.jpg

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I hope to have the bike running in three weeks. Than there is a 2 hour endurance race comming up. I hope, we find some time to introduce the e-mini bike to the public.

BTW: I'm looking for a cool name for the pocket rocket... any suggestions?
-Olaf

[Arlo1]

Well I named my bmx "bad Idea" so thats taken.
But good work great idea.

[Jay64]

Looks like a cool project. Look forward to seeing the finished project.

[olaf-lampe]

A colleague of mine suggested: mean-e-bike
This is my favorite for now.

-Olaf

[vanilla ice]

Great! What is the projected run time? Are you going to swap batteries for the 2h race?

[olaf-lampe]

Great! What is the projected run time? Are you going to swap batteries for the 2h race?

A usual heat is 15 minutes. I will not race with it in the 2h endurance race.
The battery has ~1.5kwh which is enough to deliver an average power of 6.5kW over 15 min. Than I have to recharge in 1h before the next heat starts.

-Olaf

[Gregory]

Looks great.

Paint it green and be the "Green Mean-E"

[vanilla ice]

That would be cool if you could charge in 15 minutes. Then you could do an endurance race with only two packs..

[olaf-lampe]

That would be cool if you could charge in 15 minutes. Then you could do an endurance race with only two packs..

The only cells I know that can handle 4c charge rate are a123 pouches. Hard to get these days.
Actually I would like to try a 30Ah cell instead of 53Ah. For the same weight and space, I would then get a higher voltage and could reduce the gear ratio. But we only have these Kokams on stock now.

I received a new clutch housing. It comes with an extra support for the sprocket. The baseplate of the centrifugal arms will be threaded directly to the motor bell.

I'll add a picture later...
-Olaf

[Arlo1]

That would be cool if you could charge in 15 minutes. Then you could do an endurance race with only two packs..

The only cells I know that can handle 4c charge rate are a123 pouches. Hard to get these days.
-Olaf

Lipo??????????????????? Just used Lipo!!!!!!!!!!

[Arlo1]

Looks like he already has lipo lol!

[olaf-lampe]

Looks like he already has lipo lol!

Kokam cells have a bit different chemistry in that size. They don't catch fire like the LiCobalt cells for RC-purposes. IIRC it's LiNiCoMn...something.
Fast charge is rated 2C for them.
-Olaf

[olaf-lampe]

Here are some pics of the radiator and the clutch(-es. They are available with 6,7,8,9,tooth ). Nothing spectecular, but they fit like a glove.
I also have a slightly larger aluminium radiator which is a lot lighter, but will not fit as easily.

radiator side.jpg

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clutch.jpg

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I have a MES-DEA waterpump that runs on 12V but I don't know where to get 12V from?( maybe I put a separate 3s Zippy Lipo under the tank)
The other option is a mechanic waterpump driven by a belt from the rear wheel, but I want to cool the controller down, even when the bike isn't rolling anymore.
If the turnigy aquastar isn't up to the task, I consider a watercooling-mod for the 18FET infineon. That'd require a higher voltage and different batteries. I hope the aquastar does the trick...
-Olaf

[johnws6]

I think this may work for your application to drop down the voltage to 12 volts if you want to run the water cooling idea. I think if yo ucan find a surplus automotive washer pump motor it may work. Anyways here is what i saw on ebay.

http://cgi.ebay.com/Powerful-DC-24V-12V ... 53e2a36b37

I'm also wondering, where did you go about finding 53 ah kokam cells? Are these LiMn cells or lipo cells?

[olaf-lampe]

Thanks John for the link.
I guess a common windscreenwasher-waterpump will do, My MES-Dea pump is way to big for the task.

I'm working at http://www.ececars.nl

IntroECELotus.jpg (8.55 KiB) Viewed 6966 times

Most of our cars are powered by these LiNiCoMN Kokam cells and some are not fulfilling our qualitytest and are therefor available for such fun projects. ( approx. 1-2% are slightly bent or have small marks in the pouches whereas the foil is stressed)

-Olaf

[scouser-nick:)]

looks like fun to me wont water and lecy clash if something goes wrong....like a crash?

[olaf-lampe]

looks like fun to me wont water and lecy clash if something goes wrong....like a crash?

Good question,
at hobbycity they claim the controller is waterproof, but several users have reported different stories of leaking water and fried controllers.
I'll take it apart and seal it before use.
The batteries will be mounted with the connectors up. I'll protect the connectors with 'conductive grease' that keeps the water from the battery tabs.
Even a rainy day or wet track shouldn't harm them.
Another issue is the motor sitting above the rear wheel. We have to protect it against any obstacles that may fly around.

-Olaf

[AussieJester]

Run Fluid XP instead of water then if it leaks it wont matter its non conductive fluid some use
when watercooling PCs ...

KiM

[olaf-lampe]

Run Fluid XP instead of water then if it leaks it wont matter its non conductive fluid some use
when watercooling PCs ...

KiM

Good advice, thanks KiM!
I used to use demineralized water in my overclocking days.
I flooded the cpu-socked and the graphic card several times with no problems.
-Olaf

[scouser-nick:)]

huh cool good luck should be interesting to see this!

[olaf-lampe]

I had the chance to use our workshop for some private jobs today.
So I started to build the battery:

kokam_stacking.jpg

two copperstrips and a little conductive grease

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Kokam_whole_top.jpg

the first and last connectors are longer to attach cables

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I could fit 8 cells between the frame but without any room for protection covers.
So I decided to add another two cells to the pack and put six cells in the frame and two cells on each side.

Kokam_frame-side.jpg

Lots of room left for the radiator

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Kokam_frame-top.jpg

The outer cells 'spoon' nicely between the bends of the frame

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Now I have to develope a nice rack for the cells and a quicklock for the battery poles to be able to exchange the whole battery in less than 10sec. ( Mr. Shai Agassi will be proud of me )

-Olaf

[Bluefang]

Hey mate, Have you made any progress on the bike recently? How well does the clutch fit with the motor, are you using a transmission from the pocket bike to gear it down abit or going direct drive? I have been looking at some pocket bikes and you can get some cheap ones with 3-4 speed sequential automatics, seeing as you know abit about the pocket bikes do you think that those gearboxes can be separated from the engine and adapted for use with a electric motor?

[olaf-lampe]

Hi Bluefang,
thanks for reminding me to update the blog.
Things are going slow in the welding department and also the aquastar-controller is giving me a hard time to set the parameters right.
I already bought a nice PC watercooling radiator with integrated 12v pump and a big fan ( i won't need the fan )

radiator_w_pump.jpg

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As backup plan I bought a 'naked' 12 FET infineon controller from ES member Lyen, which will have watercooled irfb3077 FETs and my homebrew 'overkill' massive copper power traces. ( more of that soon )

In the meantime I made an adapter from nylon for the clutch. Unfortunately all clutches I got from my college aren't fitting in the clutch bells I had. So I have ordered another clutch, then finish the adapter.

clutch_adapter.jpg

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clutch_adapter2.jpg

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clutch_adapter3.jpg

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On sunday I will have my first practice session on a 49cc chinese pocket bike on an indoor kart-track.
Man, these things are weird to drive
-Olaf

[Bluefang]

So you are attaching the clutch to the bell of the motor and not to the shaft on the other end where the motor mount is? I am looking to attach a CVT to a electric motor eventually like http://cgi.ebay.com.au/X-2-X-8-R-6-Pock ... 5ad3d49139. I have never worked on these and i was just going to buy one and see how to directly connect it to the motor, but i assume all i need to mount it to the motor properly with a clutch is make a adapter plate that mounts on to the motor that the CVT can bolt to with a clutch pack fixed to the motor shaft on the inside of that bronzy colored bell on the CVT. This will all be very useful if i use a CC controller on the motor

FYI these CVTs have been used on another forum http://motorbicycling.com/#motorized-bicycle a fair bit and seem to be able to handle some fair abuse when used as the primary reduction.

[olaf-lampe]

It's an interesting CVT box, but it would only be useful when the motortorque is too low. In my case I have to limit the torque with the clutch to keep the controller alive. If I'd use the CVT instead, it would imediately switch to the fastest gearing ( in my imagination at least)
I wouldn't suggest to use the motorshaft to drive something. The power of the motor comes from the bell. The shaft should only work as the guiding centerpoint.

Here in the Netherlands it's not allowed to have gearboxes with more than one gear. ( I'm talking about the dutch minibike challenge) Therefor I didn't look much into those semiautomatic or CVT gearboxes. There is also no room left in the engine department. Even less in an electric version...
Probably for dirt-bikes or midi-bikes?

Anyways, today I had a few nice laps on the karttrack.
I had several technical problems with the carb and exhaustmounts. ( all solvable and not unexpected )
I twisted my left knee and ankle, when I cornered too hard. In other words a perfect racing day

I spoke to the admin of the dutch minibike forum and he was interested to see some pictures. My workmate who sold his selfmade frame to me, will start a buildblog in the dutch forum and hopefully next spring we'll have something to show.

-Olaf