RC Turnigy 80100, FS Kona Cowan DJ, A123 build.

kfong

100 kW
Joined
Sep 2, 2008
Messages
1,957
Location
SE Michigan, USA
I’ve been working on this for a while now, but waited till I had something to show. I’ve wanted to do an RC build for a long time, but the noise turned me off. I eventually gave in because of the power level and what I plan to do with the bike. My local park has put in a small BMX track with some good size jumps. This would be a riot with a bike powerful enough to accelerate into the jumps and balanced enough to make it fun. A mid drive setup was needed and to keep it light an RC motor would be the best call.

The bike is a Kona Cowan DJ frame that had a lot of BMX parts on it. It's really built to take a beating. I wasn’t sure how easy it was to modify the bike but it turned out that bike parts are fairly interchangeable.
I was able to remove the Oddessy Spanish bottom bracket and replace it with a conventional Isis bracket. This allowed me to use a Cyclone crank with a freewheel I had built earlier with this bike
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=11542
I decided to gut the parts from. If anyone has a spare cyclone crank arm. I’m looking for a set to get that bike together again.

Here is a picture of the Kona,
Cowan Dirt jumper 1.jpg
The cranks setup installed. You can see the I have clearance if I go with the 44t. Most likely I will try to find a middle ground since I plan to leave it as a single speed setup and don't really plan to pedal this bike except when needed.
cranks.jpg
cranks2.jpg
clearance.jpg
The motor I will be using and the Nuegart 8:1 gearbox
Motor and gearbox 1.jpg
I have to redo the mounts because it’s setup currently for the left side. I decided to go through the cranks instead so I would not have to deal with chain growth. I will be cutting down the motor shaft but will wait till I see what type of cooling fan I will be using.
Motor mount input.jpg
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The batteries will be A123's. This bike will be used mostly for messing around a BMX track. I want to keep it as light as possible, but putting Lipos on such a bike would be quickly damaged during a fall. The batteries will be mounted in the triangle where they will have some protection. This worked well with my BMC Motobecane setup. I will have the motor mounted under the bike but high enough so it won't get in the way. I'm hoping to get it all done by spring.
 
*Subscribed* Theres another member here, 'Rodgah' who has a Turnigy and a Nugart ready
to go into a frame, be interesting to see these up and running.

best of luck

KiM
 
I've been busy redoing the motor mount and finally the mounts that go onto the frame. Here are pics of it. It's a similar setup to my Motobecane build. This has been working out really well holding the battery and controller. 1/2" aluminum, it's probably over built but with the jumping I plan with it, I would rather play it safe. I will probably remove a little more material once I know where the connecting columns go. It took a while to figure out how to do the CAD work and mill the shape to fit the bike. The frame isn't a simple tube like the Motobecane build. There is even a flat section to deal with. I still have to do some tapping and fitting, but the trial fit is looking good. You can see how I had to reverse the original motor mount.
 

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Some more progress on the RC build. This was the hardest section of the build. Really happy so far with the results. The motor and gearbox are not going anywhere, even after a big fall it should hold together really well. The mounts pretty much cradle the bottom tube and use the 2 bottle holders to prevent any twisting. This was a bit more difficult to make since the bottom tube wasn't round and had flat areas as well. Clearance is very close to the pedals, but overall it's placed optimally. The front tire should clear as well, even after a big drop. Working in the house currently, the garage is just too cold to get anything done. Should be a fun setup. I still have to add sensors to the motor once I get all the hardware done.
 
I have a cheap 10"x12" lathe so it was an easy task to make a shaft to mate them together. You can see pics of the shaft in one of the earlier drawing show with the #25 chain. I still need to figure out how to do a keyway without having to resort to a keyway broach. I don't think setscrews will hold in this application.
 
Hard to say, since I'm going though a gearbox and don't think the load would be too bad on the Turnigy. The Neugart looks very solid so I'm not too worried about that section. I'm going to see how it works out, and can add a bearing support later. I've read people removing the skirt bearing due to the high drag, but I hoping that such a large bearing will work out in this setup. If not then that would be a good time to redo the bearing setup. I can easily replace the motor if it fails, and they seem to be available again.
 
What's the gear ratio? Your shaft was cut a bit too short to be useful? I have a spare motor plate I'm selling, it's setup for a left side chain drive though. I changed the design so I had to mirror it. Easy enough just to rotate to suit your needs, but I had rounded the corners and didn't like the look.
 
The shaft on the C80100 is not cut. It's actually case hardened 304 or 316. I just moved it across for the time being.

Thanks for the offer, but I'd rather make the mount out of steel and weld it to the Avanti D8. It's already a bit too wide.. The ration is 12:1, dual stage.

I've fitted Hall sensors, but they might be 30deg advanced. Got to redo them..
 
full-throttle said:
The shaft on the C80100 is not cut. It's actually case hardened 304 or 316. I just moved it across for the time being.

Thanks for the offer, but I'd rather make the mount out of steel and weld it to the Avanti D8. It's already a bit too wide.. The ration is 12:1, dual stage.

I've fitted Hall sensors, but they might be 30deg advanced. Got to redo them..


Yeah, that's one thing you need to watch out for with the Neugarts, the higher the ratio the longer the body. 12:1 is a good ratio though. I have to bump mine up externally.
 
I got my Nuvinci hub back from John Holmes. I had him lace a Sun Rhino wheel with it. Undecided where I want this Nuvinci drive. It weighs a good amount and won't be ideal for a bike that is meant as a jumper. I originally planned to install it on my Cyclone but sure looks nice on the Kona as well. All that weight in the back put me off the idea. Will have a better idea once I ride it.
 

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The RC setup is nearly complete. Here is a picture of the idler I had to build with my CNC. The wheel is out of black ABS with an internal skateboard bearing. Works very well. I also have the controller finally mounted. Quite happy with how everything is coming together. Currently I have the Turnigy on the bench to be fitted with hall sensors. I still have to build the battery packs out of A123's, but might use Lipo's to get it up and running. The shafts have all been keyed so the only things I expect to break are the chains. Alignment looks good, and I can adjust out any chain issues. It should be a fun bike to jump with all the components near the center. Very solid, should take a lot to break it. It won't be very stealthy but it's sure to turn heads.

final setup.jpg

Controller, I kept the mounting hardware light when possible.
Controller mounted.jpg

 
Kfong, looking good, can't wait to hear how it rides and jumps. Where did you
get the Nuegart gearbox from (and do they have 12:1 as well) :?:

OT Have followed your various builds and always been impressed w/ your work.
Wished you had a Bosch 36V interface board like your Dewalt version ...
 
Thanks Kevo,

The gearbox was pickup on eBay. I wish there was a better source.

I'm sure the Bosch would be just as easy to do, but it's not a battery I own.
 
In Germany you may have a gearbox to build en ebike from almost every producer if you ask kindly ( here in Germany there are alot of transmission producer).
I guess if you ask very kindly, almost any supplier would gain you a sample, if not for free when you have commertional interest. So it should not be too exhausting to get another of your 8:1 drives.



Btw suggest to keep distance betwenn BB and your motor box with a direct connection like i did in my (250W) tongxin project.
Chain tensioner:
bultaco-montesa-rear-alloy-chain-tensioner-pair.jpg


Chain tensioner for fools but better than nothing
c2h25epd56atx057o.jpg

flew away at 1,2 ridden meters but now i've got sth. better... just develop ... :D (that's all the fun you'll get... besides of ... riding..?)
 
It's hard to tell if that's #25 scooter chain or a standard bike chain. If it's a #25, your bound to have troubles. I'm only using #25 for my first stage. My output stage is actually 1/2 link BMX chains. Much stronger than standard bike chain. The bike suspension itself pivots around the bottom bracket. No chain growth to worry about. Different from most suspension frames. I really don't expect to see any chain issues, other breakage. If that happens I will truly be impressed.
 
I finally have the sensors installed in the motor and running on the bench. Going to make a custom throttle for this bike. I don't want the position my right wrist gets during full acceleration or during jumps. Something similiar to a brake lever for the index finger is what I plan to make. The motor is running good with a 7.2 amp no load draw, WOT at 48 volts. The skirt bearing is probably causing the higher current draw. The winding is stock. Going to leave things alone till I see how it performs. Should have it wired on the bike today and finally tested.

Just got it wired up. Wheel spins fine, current is about 8 amps at WOT. I need to setup a temporary throttle. I really like how this build is coming along. I plan to put a small A123 pack in the triangle to keep the bike light. It's already easy to lift as is. Balance is at the triangle, so it should be a good jumper. Throttle response seems smooth and gradual. Can't wait to start playing with this ebike. This was a slow build, but I'm very happy with how it turned out.
 
Finally took out the bike with my Topeak 12s lipo pack duck taped to the top tube and straddled between my legs for support. Temporary till I make a custom pack. Started down the street, but notice the current limit was set low. Made it to the end of the block and on the way back I could smell the motor. Something wasn't right. Current now on no load is spiking past 25amps. I think the factory windings are shorted. So much for Turnigy quality control. Will have to take the motor apart and get it running again. Wasn't able to get full speed so first test run was disapointing.
 
That sucks. Sounds like the motor is toast. This is the sort of story that will force me to open up my 8085 and inspect it all before I even turn it over.

If I was a betting man I would guess the windings were not tight, and one of the strands come out of a slot and got mashed between stator and magnets. I know some other have had issues like this in the past.

+1 on the awesome build. I am just contemplating doing a full suspension build with my 8085, and really like to see how others solve the problems. Cheers.
 
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