Pocket Rocket w/ Outrunner

[Metallover]

Hey all,
I got the chance to aquire a pocket rocket for $30, so I jumped all over the chance. It's a sweet little bike, but the 18v 150w brushed system was a little lacking... :| I decided to put my outrunner in there! Here's my motor, rated for 2400w. I'm guessing I'm getting 1200-1500w out of it, which is more then enough for this little thing. Right now I'm running 10ah 24v sla batteries, which seem a little weak. I'm charging them up right now so I can get some serious speeds out of this thing next ride. I got up to 25+ today after a 1.5 hour charge. If these batteries don't cut it, I'll got for a nice 10ah 6s lipo setup. Should bring the weight down from a heftly 40lbs...

Right now, I'm using the stock gears, which is a 5x15 belt. I'm geared for just over 30mph. Too much. The belt is also showing wear after 20 mins of runtime and the pinion is off-centered after I bored it out with a drill. :lol: I have a 72t #25 chain sprocket and freewheel I can swap out for the existing plastic pos and I'll order some chain and a new pinion from mcmaster car. My question is, can a machine shop bore this out to 10mm to fit my shaft? I would like some set screws too.. 8) I will get a 9 or 10t sprocket for my pinion to be geared for low 20's in speed.

One reason I need to gear lower is for startups, which is very poor on the existing setup. If you aren't going 3-5mph, the motor loses sync and makes a great whining sound. Temps are fine, 90-110 on the motor/controller (supersimple 100a aka suppo 100a aka hobbycity SS 80 or 90a, $30). I might gear up in the future if everything is right.

One thing besides the drive system I want to change is the throttle. The servo tester has a 5k pot. The thumb throttle on the bike is close to 10k, but has variable "levels" of throttle. I measured the ohms, if you want to know them. What are the solutions to a good thumb or twist throttle to work with my controller/servo tester? The magura is a little expensive considering the bike cost me $30 and the electronics cost me about $90. I had the batteries.. $120 is a pretty good deal, is it not? I'll probably knock the total up to $140 with my new gears.

I have some great closeups of the servo tester too. It's the cheap one from hobbycity. Let me know if you want to see them I'll post em up.

I'll take a video once we get all the kinks worked out. I would like to get the gears and throttle problems worked out, and maybe the brakes.

 

[archer-ca]

Awesome Ride!! Great job so far. Yeah brakes might be sorta nice, eh? I was just wondering that as I was checking out the pics.

Keep us posted!!

Norman

 

[johnrobholmes]

Hey there Great little project!

A machine shop can do anything for you if you pay them. How will your geardown change with the chain system? How was the motor temp?

 

[Metallover]

Using BrianG's calc, I'm at just over 30mph. With the geardown, I'll be around 22mph iirc. Has anyone experienced dealing with machine shops for small projects like this? How should I go about asking them and how much will they charge?

I've seen my motor at anywhere from 85 to 105 degrees, so I'm not in any temperature danger. The main reason I'm gearing down is to make startups smoother. I also want to replace the crappy belt system..

I think the cheapest throttle solution is to get a sliding 5k pot and us that for the throttle. I can put a spring/rubber band on it so it returns to neutral and it should be easy enough so it's easy to operate.

 

[Metallover]

Small update today.

I messed around with the settings on the esc a little. I don't know what the timing was set on before, but I changed it to 15* for 10-14 pole outrunner motors. Startup is now much smoother.

I have the option of 1* for 2-4 pole inrunners, 7* for 6-8 pole motors, 15* for 10-14 pole outrunners, and 30* for 10-14 pole high rpm outrunners. If one of the other settings would be better for me let me know. Startup is much better now though, but still not perfect.

Since this setting change and the improvement on startup, I think I'll just run my 11/72 gears I have now geared for 27.27 mph. I'll see how it goes and I always have the option of gearing down later. Right now I'm geared for low 30s.

Since I don't need the sprocket from mcmaster, this will allow me to try and find the chain locally to save some money. Would your standard lowes/home depot have #25 roller chain?

Left on the to do list:
figure out throttle, 5k sliding pot would be nice
get chain
switch freewheel on rear tire to allow #25 sprocket to attach
Make a switch like this, I could attach it to a keyring - http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6581&Product_Name=Heavy_Duty_Switch
and optionally, I could fix the brakes. I don't really care about that though. :lol:


AND BTW, hobbycity has some 40c rhino packs in stock. Click on new Items. They only go up to 2550mah at the moment, but they'll probably get more in soon.

 

[johnrobholmes]

If there is a machine shop supply (like welding gas, steel supply) they probably have chain there. Or a farm supply place.

 

[chet]

If you can find a small one man shop, you will have better luck than a jobber shop. you will be surprised how many machine shops are in a basement or garage.
I'm lucky, my school mate has a shop next door to me.

 

[Metallover]

Hmm, good info on the shops, thanks. For now, I'll just keep my 11/72 #25 gears I already have. I ordered 3' of chain, a master link, and a sliding 5k pot the other day from electric scooter parts. Besides the electronics, I doubled the money I put into the project. :lol:

I'll take some pics and maybe even a video when I swap the crappy belt out for the chain.

 

[vanilla ice]

We're running 3 of those 10ah bricks on our pocketride right now. Looks like yours will fit a 3rd in the tail, that is if your electronics will take it. Makes for a heavy little bike, but it fits and its cheap capacity. I bet it'd ease the amp load on each bat and make gearing easier.

 

[Metallover]

We're running 3 of those 10ah bricks on our pocketride right now. Looks like yours will fit a 3rd in the tail, that is if your electronics will take it. Makes for a heavy little bike, but it fits and its cheap capacity. I bet it'd ease the amp load on each bat and make gearing easier.

I'm thinking I'll need 4 to do a a 2s2p configuration? My electronics won't take a 3s configuration; 24v is just about the limit.

Out with the old, In with the new. The old freewheel had to be completely dissasembled to be removed, so I'm not sure if I'll ever be able to put it back on. It's a pos anyway, so I guess I don't need to worry about that now! 8)

Awaiting chain, a few bolts, and a new throttle pot. Can't wait.

Sorry for the blurry pics too; my $70 camera sucks.

the old freewheel

I can fill up the tire now!!

just awaiting chain

here are some other pics I have. The guy on the bike is my friend troy, I am about as big as him if you're wondering. I'm 5'7".

charging setup. I just swap out the series connector for a parrallel connector and charge the packs with a car battery charger at 2a. I'm not sure if the batteries will take 6a which is the next step up. Let me know if they can. They're 10ah 12v sla batteries.

 

[vanilla ice]

I've charged 7ah sla at 5amps, but IIRC 1.5amps is what is recommended on those. I'm not sure if it hurts lifespan yet, likely does but it works.

10ah's maybe 2 or 3 is recommended. Here's a 10ah that says 3.6amps max charging:
http://www.ragebattery.com/batterystore/SLA-10-12.html
Not sure how similar that one is to yours though.

I've been looking for wand that will let me fill through the sprocket of my scoot for weeks. Let me know if you find one. On the pocketbike I grinded one hole out to fit the wand we've got.

Its not going to be easy to fit 4 10ah's on there! Maybe you can be our guinea pig and run a hybrid parallel setup.

 

[Metallover]

I've charged 7ah sla at 5amps, but IIRC 1.5amps is what is recommended on those. I'm not sure if it hurts lifespan yet, likely does but it works.

10ah's maybe 2 or 3 is recommended. Here's a 10ah that says 3.6amps max charging:
http://www.ragebattery.com/batterystore/SLA-10-12.html
Not sure how similar that one is to yours though.

I've been looking for wand that will let me fill through the sprocket of my scoot for weeks. Let me know if you find one. On the pocketbike I grinded one hole out to fit the wand we've got.

Its not going to be easy to fit 4 10ah's on there! Maybe you can be our guinea pig and run a hybrid parallel setup.

Hmm 3 would be pretty easy but 4 would be a challenge... Putting the third above the back tire would work and the fourth might be able to go under the scale "gas tank". Maybe also strapped to the front fork or behind the front tire...

I took the uninflated wheel to a few gas stations and one finally took their wand, screwed off the end, and he was able to fill it up to enough pressure with just a tube thing. This was with an industrial conpressor system, so you might need a lot of pressure. Te place I took it to was an oil/tire change place with air powered machines like the tire mounter and countless impact wrenches.

I think if I upgrade the battery, I would go for lipos. Zippy or turnigy. They'll be more expensive, but the performance and weight difference will be immense. Price is $240 vs ~$100, 20ah vs 10ah, Simlar voltage, less voltage drop with lipos,,, I don't know about the cycle life of sla's, but the best lipos have 600-800 cycles and I expect 250-400 out of the zippys if I get them.

 

[vanilla ice]

If you could figure out a way to mount the turnigy's in parallel with your two bricks, that would be easy to fit. The 6s 5000mah is a good deal per kWh but its "22.2v" so I'm not sure how that matches up with "24v" of lead. Maybe you could run 4s and 3s Turnigy's in series together for 7s total, two 7s strings in parallel, then put the lipo in parallel with your 24v of sla?? That would be cool if it worked.

The SLA is close to 28v fresh off the charger so you prolly would have to be careful. If it'd even work at all. Whats a 3.7v lipo cell peak out at fresh off a charge??

 

[Metallover]

A lipo is 4.2v off the charger, so a 6s lipo would be 25.2v. The thing is that with your lead batteries, the voltage will drop more then with the lipos. Say it drops from 24v to 19.5v under acceleration with the leads, but the lipos might drop from 22.2 to 21v because they are so powerful. Say your bike draws 40a at speed. With a 10ah pack, that's a 4c discharge. Here's a graph of a leading lipo pack. Under a 30c load, the pack stays over 3.5v the majority of the discharge.

http://www.flightpower.co.uk/Images/dischargeCurve.jpg

And a lead acid discharge curve can be found here - http://www.elationebikes.com.au/Battery%20Technology.htm

A lead acid battery will drop to about 11v for a couple minutes at a 4c discharge, then just die. A LiPo battery at a 4c discharge, will stay flat at or above nominal voltage. So that's 22v short runtime vs 22v+ with a long runtime. If you nail it under acceleration with each pack, the LiPo will BLOW AWAY the lead battery.

I guess I went on a little rant there. The point is, a 6s lipo setup will outperform a 24v lead setup. Sorry if it came off as offensive too... :lol:

 

[vanilla ice]

No offense taken, rant on. Imo tis a shame peeps feel like they got to apologize for typing a normal post..

Short charge the lipo to only ~28v so it perfectly matches the sla voltage, then flick a switch linking them in parallel. Now you're ready to ride hybrid guinea pig stylez! Yay!

 

[Metallover]

Got some stuff done.

[the chain in the background isn't long enough]

Better esc location and mount. It's solid as a rock.

I also spent 89 cents on nuts and bolts and bolted up the rear sprocket to the freewheel. I need to put on the chain and hook up the pot and she's done for good.

 

[Metallover]

I got my stuff today! Good news and bad news. The good news is that the chain installation went off without a hitch. I measured the length, and hacked the heck out of a link until my master link would work on it. Now the bike has the old electric scooter whiz sound I remember.

Bad news is that the 5k pot I got isn't the right pot. :diablo:

I re-tested the pot off the servo tester and it is a 20k pot. :diablo: Is there any way I can make my 5k pot work? Maybe add some resitors or change some settings on the esc?

before tightening

 

[Grinhill]

There's a good chance the 5K pot may work, if the circuit uses it as a voltage divider, i.e. it provides 5V across the pot and the wiper (middle leg) gives you a percentage of that 5V.

Give it a try!

 

[northernmike]

Capacitance on the front end of that ESC been upgraded yet?

 

[Metallover]

Capacitance on the front end of that ESC been upgraded yet?

No, not yet. Should I? What are the benefits?

 

[vanilla ice]

Helps keep them from blowing up from those bursts of high current like you would get from a 1/1 scale human mounted on a 1/4 scale r/c motorcycle..

 

[johnrobholmes]

The Pot will probably work, but watch the heat on the driver board as the current will be higher.


Extra capacitance is a good idea too, I have popped enough caps to agree

 

[EVTodd]

My cheap servo tester needs a 20k pot too. I tried a 5k pot (throttle from ev warrior) and it wouldn't accelerate all the way. I ended up getting a 50k pot and making my own throttle. I recently found a 25k pot locally and swapped it out. The 50k pot worked fine but it accelerated too quickly for my taste.

 

[12p3phPMDC]

I like your kill switch/key.
It's small and simple.
I'm gonna have to do that too with a pair
of 75A Andersons.

 

[Metallover]

****Performance Report****

I measured out a 1 mile loop. The terraing is extremely smooth asphault. It's ideal conditions minus a little wind. With the 10ah 24v sla pack, I got 5.5 good miles out of it and it died at 5.75 miles. I was able to limp back and finish the 6th mile. Average speed was about 10mph and avaerage mile times were about 5:30-6:00. Temps were about 105 controller, 90 motor, and the batteries were ambient. I don't know what top speed is, but on a fully charged pack it's probably 20-25mph. It seems like it's haulin when you're riding it.

I had a more detailed, much longer post made up but I lost it all when my browser crashed.

Here's the video. It's after 4 miles, so most of the top end is gone. I edited the video my way.

Photobucket blocked my video with copywrite, and I'm sure youtube would, so here ya go on imageshack.

VIDEO - http://img190.imageshack.us/i/rangetest.mp4/

Here is the test route

And here is my town. With a 5.5mi range, look at all the places I can go!