another bmx build(friction drive)

[def215]

here are some pics of the latest build i put together for my older brother. i let him ride my little rc-powered kick scooter and he liked it, so he asked me if i could throw one of these motors on a bike for him so i did. :

the bike is a dyno gt from the early 90's i believe.

the powertrain on it. untidy, but it was just put together. ill clean it up in the future.

the throttle setup. works pretty well for a DIY one.

other than cash, i paid for labor with my blood and sweat, LITERALLY.

acoording to the gps on my phone, thats my top speed, i ran out of road to accelerate since i had to stop every block for traffic.

and this project came about all because i let him ride this little scooter:

another E-convert!

p.s.- if you see this evtodd, thanks for the inspiration. your friction drives always inspired me to put one together.

 

[EVTodd]

Thanks def! I always love seeing people enjoying friction drive. It's such a cheap and easy way to get into this hobby.

Now you've just made me want to electrify one of my old BMX bikes! I suppose I should finish my current project first.

 

[def215]

thanks todd. i agree with ya. it didnt cost much to put together. putting it together was fun too. its simple but it does its job. but i think i need some time to get it as sophisticated as yours, adrian_sm, or keplers drive.

i cant wait to see your tidal force friction drive build done todd

 

[def215]

so i let the rightful owner of this rig to take it out on its maiden voyage. i came along also on the ride with my bike. so we take it around the block a few times and just cruise with an occasional race here and there. all i can say is that i need a faster bike since that bike is faster. but as soon as we were ready to go in and was around the corner from home all hell broke loose:

those are the remains of the controller after it burst into flames.its extra crispy and charred...lol. i kept it as a souvenir to offer it to the gods of speed. :lol:
i havent experience destruction like that ever, and the person to experience it was a non-EV person. well theres parts coming for it next week which includes a new controller(obviously) and some lipos, then it will be back on the road again. until then its out of commision for now.

 

[EVTodd]

Wow! That really let loose! I've always been afraid my gf's controller would do that but knock on wood so far so good.

I wonder if the smaller diameter wheel had something to do with that.

Was that the 80 amp esc?

 

[def215]

yeah, that controller really let loose on that ride. when i came back around the corner to see why my brother hadnt came back yet, i come to see the sight of the controller sitting on the ground smoldering. it also left a burn mark on the asphalt from where the burning controller was sitting. :lol: at the time i was running the mystery 60a controller. my scooter runs the 80a controller and the magnets have came loose before on it. but the scooter is still ticking *knock on wood*

i just got a dynam detrum 70a controller from hobbypartz along with some lipos(bought it form a US seller because i didnt feel like waiting 2 weeks), and it seems like its holding up so far *knock on wood*. i just notice the motor and controller produces a fair amount of heat. maybe because im running high kv(670kv), but im trying to offset it with a small spindle(a 0.750 inch spindle). im also trying to dissipate the heat by putting the heatsink face down on the motor mount so it will sort of act like a big heat sink.

i just got a speedometer on the bike too and this is as fast as i got it up to for now:

i still need to gps-verify my speed though, then ill be truly happy.

 

[EVTodd]

How many volts where you running with the 60a esc?

 

[def215]

i was running 6s lipo on the 60a. IIRC its only 5s.

i got another 80a mystery controller since they seem to be the most bulletproof, cheap esc i can find on ebay. this bike is now running fantastic but the controller and motor puts out a lot of heat still. its hot to the point i can put my hand on it and i can hold it there for a little while, like 5 seconds or so. right now i dont want the risk of blowing another controller or letting another magnet come loose. so it only comes out for 2-3 mile spurts of speed runs.

i also changed out the motor shaft on this for a longer and stronger shaft that i ordered from mcmaster-carr.

but on my latest test run, everything went well:

i was riding this thing in the bike lane and out of the corner of my eye i see a car right beside me. we both hit the stop light and he pulls up beside me and the driver asks,"did you build that thing yourself?" i answer, "yes." he goes, "that thing is awesome!" so i scream back, "how fast was i going beside you?" he answers, "about 25-30 mph." and im like, "wow thats awesome, i didnt know this thing had all that in it!" so that was that highlight of my ride. too bad my spycam wasnt working or i wouldve had the actual video of it.

but this thing gives me the EV grin, and im sure it does it for the owner of it also, which is my older bro. now i need a faster bike.

 

[EVTodd]

I think the 60 amp version says it can handle 6s but I'm sure that's pushing it especially if you're pulling bigger amps.

Are you still using the original 80 amp esc you had on your bike? We are still having great luck with the mystery 60a on the gf's bike. After seeing the picture of yours fried I'm always a little nervous when she goes up big hills but so far so good (knock on wood).

I'm helping a friend build a friction drive bike right now and he went with the 80 amp version. He only weighs around 90 lbs and wants a 20 mph top speed so it should be great for him.

 

[def215]

im not on the original 80a esc. i went through a few of them. the 80a controller on the bike now has been swapped over from this bike and scooter several times, but its been a while with this controller. i feel like the mystery 80a esc has treated me the best for the price of it.

yeah, your friend should move on a friction drive bike. im ~130lbs and this bike pulls nicely with the motor i have. having someone thats 90lbs, well that should be interesting.

this bike exceeded my expectations with how fast it is. i thought it was going to act similar to my scooter, because the both of them have the same exact setup on them, except for the spindle size. my brother and i went for a ride, and i decided to take off full throttle because i was expecting him to give pursuit, which he did, and his bike(the one in this thread) blew by me like i was standing still. but i guess im happy since my builds are in working order(knock on wood).

hows the tidalforce build going todd? i ran across that thread the other day but i havent seen an update on it lately.

 

[EVTodd]

Just posted a quick update on the Tidalforce. It's almost done. I finally ordered batteries and they should be here before this coming weekend. Should be a lot of progress very soon.

 

[MrBoots]

Nice setup there my friend. After seeing all the awesome work you hysterical have done, I'm inspired to build up my own friction drive rig. I love my chaindrive bike now but it has two key weaknesses, chain alignment and weight. Having the chain pop off when going over 40mph is not fun!

 

[def215]

Thanks mrboots!

Even though there are people who disagree with friction drive being a viable means to drive a bike, i find it to be a fantastic way to do it. I would definitely recommend building a friction drive bike, as long as the bike doesnt see wet conditions(well none of my stuff sees wet conditions, even my chain drive bike. Thats why i went this route) i think itll be a great bike build to do.

Ive uploaded a video of this bike yesterday of me doing a top speed run and i was able to hit 30.4 mph(i think i possibly have it overgeared).
After that run, i smoked the controller so ill be swapping the rc esc for an ebike controller, im just doing the research on what i need to get it to work. ive gone through a few controllers on this bike and i dont want reliability to be an issue anymore.

Heres the video:
[youtube]gP_mrs_LhX8[/youtube]

 

[adrian_sm]

What have you been doing to smoke the controllers? I haven't killed one yet on my friction drive.

The two main controllers I have been using are these. With the most kms on the 85A vesion, which is cheap and has an on/off switch I really like.
- TURNIGY K-Force 100A Brushless ESC
- Turnigy Brushless ESC 85A w/ 5A SBEC

The main motors I use (driving off the outside of the can) are:
- HXT 63-74 200kv Brushless Outrunner
- TGY AerodriveXp 90 SK Series 50-65 270Kv

I usually run 5s LiPo, which means I am "geared" for about 40-45kph on the flat.

Let's see what else could be different.
- I always pedal a bit before hitting the power. (too much power at low speed I believe can smoke controllers)
- my drive disengages when not in use, so the wheel never tries to drive the motor (which could smoke controllers)
- more recently I have been using a throttle interface that limits power amongst other things.

Just curious why you seemed to have been so unlucky.

- Adrian

[EDIT] Oh I did kill one controller but that was from trying to drive a melted motor. I was dumping >2kw into the little 5065 motor up a long hill and killed it.

 

[def215]

ive been using the mystery 80a esc, but i run 6s lipo. my drive doesnt disengage from the tire. those things possibly did it. but i do pedal before i throttle up.

im going to try the ebike controller this time around. i always wanted to try it so hopefully i will be successful with it. :lol: im trying to get it so it can be somewhat reliable.

its strange because my little electric goped runs the same exact setup as the bike and its been running very nicely within reason(push off before i start, running WOT to prevent low voltage amp spiking, etc). the only difference between the two is the spindle size, which the bike is a .75 inch and the scooter is a .65 inch.

 

[spinningmagnets]

It looks like you have added a single fat capacitor to the power input. Is it a low-ESR cap? According to the long "adding capacitors" thread, if it is a normal range resistance cap, they cannot sponge in-and-out the voltage ripple very fast, and the spikes can fry electronics inside the ESC, leading to a cascading failure of other parts.

They low-ESR caps are about $2 each, so other than the annoyance of soldering, why not start out with 4 of them? If that ends up being more than neccessary, it wont hurt anything.

Low ESR caps thread
http://endless-sphere.com/forums/viewtopic.php?f=30&t=22194&start=45#p382837

 

[EVTodd]

That's interesting. I didn't realize your roller was that small. That should actually help keep the esc alive. I'm also starting to wonder if you're getting a bunch of regen killing them. My castle hv85 seems to be able to handle some of that but the mystery esc might not.

My gf's bike is now set up on 6s and still running the 60 amp esc. I doubt it will last long but we'll see. I have a castle esc ready to go if/when it takes a dump.

I'm sure you said before but which motor are you running? According to my calcs you need well over 13000 rpms for 30 mph with that roller.

 

[def215]

todd,

im running a exceed rc monsterpower 46, which is basically a 50-55 sized motor. it has relatively high Kv which is 670Kv. the reason for it was that at the time, i was looking at the HK motors, but none of the similarly sized motors were in stock, so i looked at some US sellers, and their larger motors were out of stock, so i bought this motor as an experiment, which was to see if a high Kv motor will work if i used a small spindle to drive it. the regen can be killing it too but the throttle was set up to be on or off with some adjustability. maybe im just doing everything wrong. thats probably why it went. :? ill be trying the ebike controller soon since i just ordered one yesterday. hopefully i get good results with it.

right now i can say its working for one of my projects, but not the other.