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java230 SuperDork
2/23/18 10:18 a.m.

Maybe not what your expecting, but its electric bike time!

I have previously had a 250w hub motor in the front wheel of one of my bikes, it was meh, helped a bit on hills and whatnot, but when the batteries died I dumped it. 

This will be my first mid drive. (Mid drive drives the crank, not a motor in the hub of the wheel) I wanted to do a mid for a couple reasons, a big heavy motor in the wheel really beats spokes and rims to death, and a mid can be mounted inside the frame, and you get to have the advantage of using the gears. Most clamp to the bottom bracket somehow and hang down, but I am making mounts for inside the frame.

The motors range from 500 watts to 7500+ if you go crazy. I settle on a DIY oriented kit, with a 3000w motor (if you run it at a full 72V).  Running the motor at 52V as planned is ~2080 watts, 2kw = 2.68HP, motot is rated at 100Nm torque, so lets say we take 2/3 of that like the watts, 66Nm = 48ft lbs of torque devil

The "kit" is a cyclone 3kw kit, its a Tiwanese company that makes them, and its pretty DIY. Basic BB clamp brackets are included, but its up to you to figure it out. I was planning to install in my old hard tail bike, but found a good deal on a older Intense XC frame. I want to mount it inside the frame to keep the ground clearance. This will mostly be a fun commuter bike, but there are lots of good trails around as well.

Plan for batteries is Multistar Lipo's, 52V 16ah (I already have a charger etc from RC stuff). My ride to work is 14.4 miles, so hopefully I will have enough to get there easily. I can charge at work as needed. To do this I used 2 4s packs, and one 6s, in series. These will go in a backpack.

I had the seller measure the frame opening, it looked like I would need to notch it, but it turned out to fit [i]exactly[/i] tight between the tubes. Could not have had 1mm less space.

Frame, well a whole bike, but everything needs some love. Brakes are done, need to be rebuilt and bled (I have a new set off another bike I will use), Fork needs a full rebuild. Cables are broken. So really I bought a wheel set, frame and bars, but the price was right. Its a early 2000's Intense Tracer.

Got the frame home and set it over the motor, I was super happy! It fit, just barely. If it needed to go any further to the drive side it would not have fit.

Now to build the mounts. I picked up a sheet of 3/16" aluminum, a bit thicker than the stock mounts. I wanted to use the same style, clamp in with the BB and catch the motor bolts. A little bit of CAD and I have a design. It follows the down tube and catches three of the bolts on the gear side of the cyclone. These mounts need to be pretty sturdy, the motor wants to twist against them when power is applied. The Stock mounts are known to be very flexy.

Rough cut with the jig saw (I used 3003 alu for easy cutting)

Two of the three bolt holes are perfect, the top one was off a bit. Not sure exactly why, but sharpie cardboard and had drills might be part of it. I think I will be able to oval the hole enough to make it work. Luckily this one will also be tied to the suspension pivot point so I think it will be strong enough. (no the tensioner wont go there)

This tab will help the BB not let things rotate and support the upper edge. I was only able to use 1/8" here, but its a short span.

Hanging in place! Now to do the other side.

The mount for the other side started with the stock bracket on the BB. I had to notch it a little for the suspension bolt. A piece of aluminum flat bar was cut the same width as the BB, I and drilling and tapping this through both of the mounting plates. It will sandwiching them together, adding a little shear, and also I can clamp around the down tube there if needed.

Drilled and tapped for m6x1, not perfect, but it was all held in place and drilled together by my eyeballs....

Now the two mounting plates were tied together, I needed to get something to help the motor not rotate under load. Hopefully what I can up with is strong enough, I have never done a mid drive... I used a piece of 1/8"x2, it catches the lower motor bolt, and then ties into the black plate down near the BB. Two bolts hold it in place down low.

So at the end of the night I have a motor mounted in the frame (ignore the random hardware, I need to run to the hardware supply house and get correct stuff....), I trimmed down the connectors I would not be using off the controller, built the series battery connector, and tested the electrical side. 

Chain lines are pretty decent, although the drive chain will have a fair bit of slack to take up with the tensioner.

Hopefully tonight I can get the bike side of things fixed up, replace the derailleur  cable, swap my brakes over, fill tires etc. Need to figure out where to put the controller too, thinking a saddle bag maybe? Then wire runs, replace the phase wire connectors with 6mm bullets and test ride! (and figure out what to do about the front shock....)


More coming soon. (I did d a test ride at 10pm last night, lets just say it was GOOD)

dherr Reader
2/23/18 10:36 a.m.

Cool bike, my first question was how do you do a battery large enough to have any range but also not saddle down the bike. Did you say the batteries are in your backpack? Seems like some saddle bags on each side of the rear wheel down low (like a touring motorcycle) would be better for balance and probably allow you to double your range.

java230 SuperDork
2/23/18 10:51 a.m.
dherr said:

Cool bike, my first question was how do you do a battery large enough to have any range but also not saddle down the bike. Did you say the batteries are in your backpack? Seems like some saddle bags on each side of the rear wheel down low (like a touring motorcycle) would be better for balance and probably allow you to double your range.

Lipo batteries are very energy dense. The pack weighs a bit more than I thought, but its 10lbs 1/2oz. Really not bad at all on your back. That is 16 amp hours, which in theory should give me 20ish miles range depending on speed and throttle use/pedaling. I have not really tested it at all yet, but the pack is 828.8 watt hours, which gives me ~41mins at full throttle (which is fast.....)


I was trying to keep as much weight off hte bike as I could. I wanted to stay as nimble as I can.

klodkrawler05 Reader
2/23/18 10:55 a.m.

Subscribing for more updates, I keep thinking something like this would be so perfect as a pit bike, and lower profile than zipping around on a kids motorcycle.

java230 SuperDork
2/23/18 11:10 a.m.

In reply to klodkrawler05 :

Definitely quieter and lighter, and possibly equally (or more) peppy devil

GameboyRMH MegaDork
2/23/18 11:52 a.m.

I've been having similar ideas recently, it seems that you can build an e-bike for about a quarter the price of buying an equivalent model off the shelf.

java230 SuperDork
2/23/18 11:55 a.m.

In reply to GameboyRMH :

Yes yes you can! The commercial ones are more money and less power. Most are 750w 

singleslammer PowerDork
2/23/18 12:53 p.m.

Nice, I have been considering electric motorcycles lately so I am watching with excitement. 

java230 SuperDork
2/23/18 3:01 p.m.

In reply to singleslammer :

I rode it last night, its damn close to electric motorcycle, It was 10 pm, very dark, and 20 degrees out, so I didn't go nuts.... I was in 5th gear (middle of the range basically, 9 speed bike) and it was lifting the front tire if I just punched it devil

java230 SuperDork
2/23/18 3:05 p.m.

Chains are on, cranks and pedals are on. Brakes are done. Controller is just temporarily zip tied on, its going to go in a saddle bag in roughly that spot. I put 6mm bullet connectors on for the phase wires, I have a 6pin waterproof one coming for the hall's. Only issue is the throttle/shifter interference. (I ended up just putting the throttle on the left side, time will tell if it stays there or not) I fired it up last night and it all spins nicely!

It works like this, there is a freewheel on the crank (trials crank basically for bike people), both the gear that the motor drives and the gear you pedal at attached to the freewheel. The motor also has a freewheel. This allows you to pedal with the motor off, or motor without having to try to keep up with the pedals. The rear gears can be shifted lower or higher for climbing hills or speed as needed, this helps keep the motor spinning and in its efficiency range. The motor also has a planetary gearbox on the nose of it, IIRC is 6:1 ish.

java230 SuperDork
2/23/18 4:42 p.m.

Just got home from work, half charged battery (52.3v) with me peddling I hit 35.2mph devil

adam525i Reader
2/23/18 7:56 p.m.

That's a lot of motor, I bet this thing flies!

Are you sure you want that much energy strapped to your back when things go bad? I understand where you are coming from keeping the weight off the bike if you do hit some trails but I'd feel better when I crashed knowing I could easily get away from the chemical fire.


java230 SuperDork
2/23/18 8:08 p.m.

In reply to adam525i :

It's a trade off, I have dealt with lipo batteries with my rc cars for awhile. They are not a bomb like people make them out to be. I can dump the pack quick if needed I guess. I was thinking of wrapping them in a layer of foam. 

coexist Reader
2/23/18 8:14 p.m.

Just an FYI, 

My state of WA limits electric motors to 1000 w to be considered an assisted bicycle. Beyond that it becomes a motorized vehicle, with associated licensing required. I'm not sure how they consider a 3000w potential with only 1000w being used due to voltage limit.

java230 SuperDork
2/23/18 8:20 p.m.

In reply to coexist :

Yes.... I read all the WA laws (I am in WA too) . Im ok pushing the limits. I don't plan to blast by people at 30+. I think ride carefully and safely and I hope to not have issues with LEO.


This is also why most commercial units stick with the 750w

coexist Reader
2/23/18 8:25 p.m.

Tried to find a pic of the local guy's handbuilt electric "bike " with 5Kw motor. He had it up to 60 mph.

Most of my motor vehicles can also break the speed limit, and I have been pulled over on my bicycle for excessive speed.  I am relatively responsible with my power.

java230 SuperDork
2/23/18 8:30 p.m.

In reply to coexist :

Tell me more! Pulled over on your bike?! 

coexist Reader
2/23/18 8:46 p.m.

In California,  twisty long downhills where a road bike could outcorner general traffic, and the straights were too short for the cars to get much speed.  When I was in high school I rode with my dad every once in a while, he was relatively crazy on the bike.  We would keep track of how many cars we passed riding down Mt Diablo (our record was in the 20's).  Once when I was riding alone doing the same thing, an occifer saw me pass a couple cars and pulled me over. No citation, as I wasn't carrying any ID. My dad was also pulled over in similar fashion.  Rich family heritage...

java230 SuperDork
2/23/18 8:48 p.m.

In reply to coexist :

Ok but nothing in WA? Sounds like fun laugh

java230 SuperDork
2/23/18 8:58 p.m.

Ill try the left thumb for the time being..... Bars done for now.

I know SBP says these are right or left, but it was not comfortable for me, maybe I have a short thumb.... I'm making an extension, hopefully I don't break the tab off... Its just a little piece of aluminum.
rough shape. I will bolt and glue it in place.

coexist Reader
2/23/18 9:03 p.m.

Now I live on Whidbey Island where the hills are short and steep, and I'm not so craycray.  Plus I mostly ride fixed gear, so downhills are a different kind of experience.

I have had a couple hub motors come into my life, but couldn't muster the enthusiasm to build up a bike with them. I think you're on the right track , but I would also work on frame mounting the battery, with quick release of course. If you can repackage the battery cells, could try a triangular mount in front of the crank to keep the c.g. very low.  Also incorporate a fender with it.

java230 SuperDork
2/23/18 9:09 p.m.

In reply to coexist :

Very cool, my mom is on Whidbey too.

Yeah I tried the hub motor too, this is a whole Nother ball game. Fixies beat my knees to death these days.

Frame batteries are possible, but i want to try to avoid them so far. It's only 10lbs on your back. 

Dusterbd13 MegaDork
2/23/18 9:10 p.m.

Dumb question:

Not including the bike, how much do you have in this conversion?

Id love to get back out on the trails, but my knee wont let me. 

java230 SuperDork
2/23/18 9:23 p.m.

In reply to Dusterbd13 :

Batteries were 250 ish, motor was 430 with a second throttle  (including sales tax as I bought local from sick bike parts.com)

OHSCrifle Dork
2/24/18 8:01 a.m.

Does that drivetrain have a chain guard? It looks hungry.


And awesome.

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