Holmes' #4, the mini bike (build 3ish)

johnrobholmes

johnrobholmes

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Joined
Jul 7, 2008
Messages
3,963
Location
Missouri
Sometimes you feel like a nut...


12s lipo
Castle HV110, maybe smaller
Magura throttle
Bafang rear laced to a 16" Rhyno Lite rim



I cut my own spokes and laced up the wheel yesterday. Not happy with the threads, so I am having Dan's competition cut some new ones that will be radially laced in. Stupid spoke threader not worth the scrap it is forged from.

This is gonna just for fun, an attention getter around campus and party time activity. I have already started planning a little dirt track in my back yard for drunken fast-lap parties :lol: Tough part will be getting good brakes on the back. Second shot compares the project bike with a mountain bike.
 
Hey JohnRob! How do U ride that teeny little thing? You gotta be less than 3 ft tall! I believe U are taller! Do U hire little people?
otherDoc
 
hehehe i think the size of the bike is to initiate drunken stacks Doc... imagine 6 foot college students full of piss trying to out do each other will be quite comical :p
 
I am indeed 5' 10". Took her for a little ride today. Almost got thrown off the back a few times since I tested it with a throttle box. The little wheel accelerates faster than expected!


It is quite fun to ride. With a few more mm of space I can get a freewheel on and have it pedal too, then I will add rear pegs so that there are options for feet placement. It actually rides on the pedals while standing rather well. Now I just need more voltage :lol:


Looks like this weekend I need to have a party! Who can run 4 laps around my back yard the fastest?
 
johnrobholmes said:
Looks like this weekend I need to have a party! Who can run 4 laps around my back yard the fastest?
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While holding a can of bud...seconds will be added for spillage :p

Better add B.Y.O Beer and Battieries to the invite to ;-P
 
Minis were the new tall bikes a couple years ago. Portland's "Zoobombers" is a mini bike gang with lots of bizarre video and web presence.

I can't ride a stock one very well. It hurts. But they can be adopted to adult size riders. My little bikes have twenty inch wheels*, longer cranks, bigger gears and their seat heghts are the same as all my other bikes. They're some of the handiest and most comfortable bikes I own.

Mark's is the coolest one I rode. It's a fixed 16" wheel bike with drop bars. It felt too twitchy riding on the tops but when you get into the drops, it all came together. Donald' is the tallest mini in Cascadia for sure.
fxas1u.jpg

Don't try bombing parkade ramps with this one.

There've been SFU bombs locally. Your bike's gotta fit in a hockey bag to get it on the bus to the top of the mountain. Assemble your bike and bomb back down, disassemble, put back in bag and go up on the next bus for another run. Mount Hood in Oregon and Mt. Seymour in BC have been sites for mini bike bombs. 35MPH on those things is nuts. Faster is totally insane.

Kids bikes sometimes have smaller diameter steerer tubes so getting a suitable riser stem and handle bars may require searching or fork swapping.
Higer rise handle bars are easy to get. Long and strong cranked-back seat posts can be had for BMX bikes. Crank length should be longer if you hope to pedal it comfortably. Theyre even pretty good for court polo when you get them set up right.

Looks like you're off to a good start! Good luck with your project. You've got lots of room to mount batteries vertically on the back side of the seat post. I think that would be a good place to put them for retaining control over such a short wheel base.
The front hub motor can't induce wheelies so moving weight even behid the rear axle wouldn't be a problem in that regard.

*Yorick, my chopper, has a 16" average wheel size. Twenty inch rear and a cheap 12" wonky tire front of an extended fork that's not quite perfect.
It gets interesting at 30+ KmH but is a babe magnet like you wouldn't believe.
Yorick 08.jpg
458511185
 
Thats great! We have a group around here that have high bikes and crazy chopped concoctions. There was actually some contest on "bike art" here locally. I thought about entering but didn't have the time to put into it.

This bike has a rear hub motor. I may put a front hub motor on there too, but that will certainly increase the cost a lot. Right now having wheelies on demand isn't all bad. I did a bit more work today. To get around the non standard headset size I welded 1" threadless cups onto the headtube. Much easier than replacing the headtube or crown race on my fork. Since my welder sucks and isn't very adjustable, I just ran a series of tacks around the join.

Now she is rideable and with strong brakes. I want to run a full length seat from headtube to rear next, but that will mean either making a seat or stealing one from my pit bike. Neither option sounds tempting.
 

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Took her for a spin around the house last night. Perfect!! She groans a bit up the hills, but that is to be expected from such a tiny motor!


Total weight with 12s1p a123 is right on 35lbs. I am looking around for the lipoly that I will use. I think some Air thunder 5000 mah 6s packs look good.
 
Johnrobholmes


Finally someone that has used a sensorless controller in a hub motor!!!!!!!!!!!!!!!!!

How has the Castle Creations controller been working?

Nice not having a controller the size of a piece of 2x4 lumber mounted to the bike.
 
It works very well actually. I need to mess with the PWM and timing a bit to see what I can do noise wise, but I don't see myself going to any other controller unless i need High voltage or testing time.


Gonna pick up a HV 30 and 45 to see where the line can be drawn. The HV 30 is one ounce. ONE!
 
johnrobholmes said:
I have already started planning a little dirt track in my back yard for drunken fast-lap parties
Click to expand...
FFS that sounds dumb, dangerous and maybe illegal. If I lived close I would totally go for it.
 
johnrobholmes said:
I want to run a full length seat from headtube to rear next, but that will mean either making a seat or stealing one from my pit bike. Neither option sounds tempting.
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Why not just use the old fashoined banana seat (http://www.amazon.com/s/qid=1223584477/ref=sr_nr_n_0?ie=UTF8&rs=3375251&keywords=banana%20seat&bbn=3403201&rnid=3375301&rh=n%3A3375251%2Ck%3Abanana%20seat%2Cn%3A3403201) :twisted:
 
I had a 16" bike with a rear hubbie too. Didn't get around to fitting a rack so I put the controller and 48v pack in a backpack. Extremely uncomfortable to ride lemme tell you..
 
Yeah, this ride isn't all peaches and cream to actually get from A to B. Biggest problem is the seat and wheelies right now. I'm gonna scrounge around for a banana seat, we have a local guy with all kinds of used bike parts.

Add a bigger seat, and I will be golden for comfort. It actually sits nice with the feet on the front pegs. If I keep having problems with the wheelies I may add some weight up front. Front and rear hub motor anyone? :lol:
 
Got in some new spokes the other day, so I relaced the wheel. It is much better now, the spokes are not bending at the nipple. The radial lace is needed since the rim is so small compared to the hub diameter. My helper seems to sneak in about every pic I take.

This little ride is fun. I just got in a 72v Chinese controller, so I will try the sucker on 24s a123 now :twisted: It is sure to throw me off a few times at least! A banana seat is in order so I can shift my weight better. What great times shall be had!
 

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A Bafang in a 16" front wheel @80V sounds like the hill climbing solution I've been after for my streched cruiser.

Would the current limiting in a CA make the use of an ESC anymore practical/possible? As long as I wouldn't have to peddle up the hill I'd be willing to stick to the legal 750 watts. Or close to it anyways. :wink:
 
hehehe he's a cute puppy :) An Alsatian i believe? Is he one of those dogs that has to be with you everywhere you go? like a shadow LoL I had a BullTerrier like that. Anywayz...look forward to next update AND of course some pics of the lads tearing around your backyard full of beer and an inflated belief of their own abilities hehehe..
 
She is a German Shepherd. Very much a shadow that follows me everywhere. She tries to act like she is in control.


You could use the CA to keep amp draw down on hill climbs, or you could just watch the amp draw and throttle back.
 
Now I have her running at 24s a123 with a shenzen controller. She is a wheelie machine at any speed! Not exactly what I was looking for, so I may change back to a lower voltage battery. Part of the problem is that the controller doesn't have the throttle modulation I need, there is one particular spot in the throttle where it bursts power. I can hear the discrete steps in the throttle with the wheel off the ground. :lol:


Maybe I will put this beast on a 20" bike so that the rear end is longer. I really wanted to have more power on my little bike, but it seems that I can't let anybody ride it now!
 
As she sits now. I rode it around some today, and the biggest issue is low speed throttle. Once I am rolling about half speed (10mph @72v) it isn't so bad, but around 1/10th throttle it surges horribly. This makes offroad and low speed driving near impossible.

Very fun however, put a big grin on my face :mrgreen:
 
Maybe with a wheelie bar....


On another note, this thing climbs hills like a goat! I can't pedal fast enough to help, so it was pulling my steep hill in front of the house at about 15mph. Need to get a wattmeter on there to see how the amp draw compares to my 26" wheel on 1/2 voltage. I like the 16" wheel build, I think I may put it into a pusher cart or something.
 
I'd cover that seat with camo duct tape. Justin did that to fix the cracks in the seat of his cross country bike and it looked awesome.
 
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