Motorbike Conversion - 1985 Nighthawk 750S - From Junk

General Discussion about large electric scooters and motorcycles and other things with no pedals.
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Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 5:50pm

Hey everyone, I got started here a few years back building a recumbent bicycle that I never quite finished (may still some day), but, with a new project. I'm maybe half-done a motorbike conversion. One of my favorite things about this forum is everyone's well-documented builds, so, I figured I'd give back to the community by posting here as I go.

I see lots of builds that people document from an end perspective when they have it all figured out, so, I think I'll take a different approach and show people what an "engineering" method looks like. And by "engineering" I mean "Start somewhere and bumble your way through all the things you have to figure out." I don't have to fake the process because I'm actually bumbling my way through this. :P

Objectives:
- An electric motorbike for cheap, as cheap as possible.
- Highway speeds, (60mph, 100km/hr).
- Commuting/cross city range (15-20miles, 20-30 km).
- CHEAP CHEAP CHEAP

My goal was originally to build the bike entirely from garbage and zero resources. Partly for the challenge, partly because I'm cheap and don't like wasting money on toys, and partly because it's interesting to me to show people without many resources how to build things. People with money can just go buy things, or cut corners.

I'm too practical to stick to those principals if convenience gets in the way, as long as I feel like the project could be possible entirely from junk and no critical component or design element would change, that's what I've done.

Build log until now and then as I build it, here on out.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 5:53pm

The Bike: A 1985 Honda Nighthawk 750S. I chose it because it was the first cheap bike I found (paid $20 total, already had a failed rebuild of an engine and the guy wanted it gone). I would have bought literally any motorbike carcass for $20, but by coincidence I happen to actually really like this one.

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It was a 750cc bike with an 80hp engine capable of going 128MPH (212 km/hr). It's the original Widowmaker, the bike that term "superbike" came from. Original bike specs: http://paulsnighthawkpages.blogspot.ca/p/nh-700s.html

The style is a "UJM" or "Universal Japanese Motorcycle", very beginner friendly, you just sit on it comfortably like you would sit on anything.

An added challenge is that this particular bike is shaft drive (versus chain). More on that later. However, again, I would have bought literally any bike for the $20 I paid for this, beggars can't be choosers. The driveshaft ends in a U-Joint that couples the driveshaft to the transmission.


I've been looking to build a bike for 6 years already, and asked a friend to keep an eye on cheap bikes. He told me: "If you pay less than $500 for a bike, you're going to end up spending over $500 for it anyway. Even a bike with a blown engine is still worth more."

Well, the seller had wrecked the engine on his rebuild attempt and given up on it and stripped it down to part it out. Some of the parts were gone before I bought it.

The headlight, front brake lines, and the front fender/windshield piece were already gone from it when I bought it, sadly, and I'll have to find a way to make a facimile from sheet metal (it's $250 on Ebay, nope).

I got a rolling frame, a half-disassembled engine, and a rubbermaid full of miscellaneous parts and all the hardware.

I know nothing about motorbikes. I don't even know how to ride one. I know nothing about engines or mechanics. I am coming from a position of complete novice.

I started laying out the parts and trying to guess and group them to what they might probably be (I know some of these are labeled wrong, they were my first guess):

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And, after a bunch of heaving and pondering and figuring out exactly, barely, by an 1/8" the one possible way to tumble, twist and pivot the engine out through the frame, I got it out.

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Great. Onto the next thing, I need a motor.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 5:56pm

Motor:

I first mocked it up with a treadmill motor to see if it would turn and how hard it was to get the orientation right. It was very difficult. That in itself almost made me give up, there seemed to be nowhere I could hold the motor that wasn't clunking the driveshaft around it's enclosure.

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Yeah, that's a toilet plunger. It happened to be the right shaft size for the driveshaft's U-joint input, so I hammered it on to "machine" the matching splines.

A treadmill motor is good for 1500 watts, probably 5000 if you feed it higher voltage. So that would be decent for a moped, and for my junk-built recumbent electric bicycle from many years ago, but not for a motorbike.

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BIGGER!

I phoned a local forklift repair place and told them my goal was to build an electric motorbike from garbage, and asked if they had anything they were about to throw away that I could strip parts from. The nice folks there said sure, and let me strip a small 1969 Yale lift. They bought it for its batteries and the rest wasn't worth selling. It had sat in a flood.

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It had 3 motors. Because it was small, the biggest motor was the pump motor, and it had a pair of shorter drive motors (one for each tire).

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Big Motor Specs:
- 7.25" (18cm) diameter and 12" (30cm) in length
- Weighs 91 lbs (41 kg).
- Series wound DC (good).
- 4 brushes. Appears to have neutral position.
- Armature feels good, no detectable wear between the brush path and the edges.
- Built-in blower fan (great).
- No HP/Wattage ratings. No spec sheets turn up on google.
- Not sure what voltage it was designed for. Was probably on a 24v system.
- Female output shaft, slot cut (awful).

The two slightly smaller motors have a threaded output. They were my backup plan, but looks like I'll be okay, more on that later.

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(guess which direction it was laying in the flood?)

I clean it up and, it runs!

First Sparks!

Great, now the motor needs to mate to the driveshaft somehow.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 6:25pm

Transmission:

TL;DR - I decided I don't need one so it's gone. Ta da. Skip this if you don't care for details.

The transmission shared oil with the engine, they're the the same assembly. I could have cut the engine off, but then I would also need to:
- Plug all the oil ports.
- Adapt the electrical motor to... whatever part of the engine spins the transmission.
- Add 60 lbs of weight for the transmission.
- Take up a transmission worth of volume inside the frame I'd rather use for batteries.
- Keep the gearbox and clutch and clutch lever.
- Actually learn how to ride a motorbike (I've never even been a passenger).

So, clearly, if I can get rid of the transmission, I should.

I figure I would need to keep the transmission for 3 reasons if they're issues:
1 - If my motor speeds don't match the correct range to spin the driveshaft for the speeds I want to go.
2 - If my motor isn't powerful enough to accelerate reasonably from a stop.
3 - If my motor needs more power than it can handle at low speed hill climbing.

Let's go through those:

1 - Napkin calculations. It's a 16" tire, so, 16x3.14 = 50" tire circumference or 4.2 feet. So every tire rotation moves the bike forward 4.2 feet. 5280 feet in a mile, so, 1257 tire rotations before it covers one mile. 60 minutes in an hour, so 1257/60 = 21 RPM for each mile per hour I want to go (13 RPM per km/h).

So if I want to go 60mph (100km/h), I need to spin the back wheel at ~1260 RPM. The driveshaft to rear wheel has a 3:1 gear, which means 3780 RPM on the shaft goes highway speed.

Gut check time. Most motors this size are fine spinning up to about 5000 RPM. The limits are bearings and centrifugal force ripping the rotor apart. So it can physically handle spinning that fast.

Series motors can spin that fast no problem, I don't know how fast it used to spin, but that seems the right ballpark.

Let's doublecheck that and make sure it matches the ballpark for the original engine.

Most transmissions only exist to slow the engine speed, where top gear is just straight linked with no reduction. The bike engine originally redlined north of 11,000 RPM, but then it also had a top speed of 125 mph. 11,000/125 = 88 driveshaft revolutions per MPH. Which does not match the tire RPM to make the bike that fast (21) so, something somewhere is still gearing down by 4:1? The driveshaft:tire gear is 3:1 or so, so, sure, it's in the right ballpark. The numbers don't matter, just a gut check to make sure I'm not worlds apart and made a mistake somewhere. If it was 7000 RPM I'd be in trouble, if it was 1000 RPM I'd be in trouble. I'm right in the sweet spot, as most motors generally will be compared to their gas counterparts.


2 - Kinetic energy = Mass * Speed * Speed / 2

It's the first, oh, 40 miles per hour (70km/h) that are going to piss people off in traffic, what would be the low gears. Above that the effects of wind resistance are dominating and you're having to consider that you only have the left over power not being used just to maintain speed. So, 40mph is 18 meters per second.

Mass is probably around 500lbs of bike plus 200lbs of rider, 700-ish pounds, call it 350kg.

E = 350kg * 18 * 18 /2
56700 joules.

Joules are useless to think about, 3600 watt-hours in a joule, so about 16 watt-hours. About as much as 4 cell phone batteries holds, to bring a 350kg bike + rider up to 40mph, ignoring wind resistance.

Anything above 0.3g of acceleration is considered aggressive, anything above 0.5g is considered dangerous. 0.3g would be 6 seconds for any vehicle to reach 40mph. That's a good target, a 27hp motor should be good enough for acceleration.

3 - Unlike with wind resistance, the power needed to climb a hill is linear. If you want to climb it twice as fast, it only takes twice as much power. The total energy used to climb a hill is the same regardless of whether you do it slow or fast.

The only thing that matters for the hill climbing part of power requirements, like with acceleration, is weight. In this case, rather than making weight go faster, you're lifting a weight.

700 lbs, 350 kg.

Potential Energy = Mass * Gravity * Height

If a hill is 330 feet tall (100 meters), regardless of how steep it is or how fast I climb it, the energy to climb it will be:

350 * 9.81 * 100 = 343,350 joules. Or, 95 watt hours.

That's only 330 feet tall, as tall as a 33 story building.

If it took my an hour to climb it, it would add 95 watts to my motor requirements.
If it took 15 minutes to climb it, it would add 380 watts to my motor requirements.
If it took 1 minute to climb it, it would add 5,700 watts to my motor requirements.
If I climbed a straight vertical cliff, and wanted to do it at highway speeds, 330 feet is 1/16th of a mile, highway speeds are a mile a minute, so I'd need 91200 watts for a cliff, ignoring traction.

My motor can't put out 100 horsepower, but luckily a 20% grade is about the steepest hills there are to climb, which makes it 20% of that, so, ~20 horsepower (plus ~12 hp to maintain highway speed itself from air/rolling resisistance), on a super steep hill that they probably don't ever make highways... 32 hp total. Very close to the 27hp needed to accelerate "aggressively" from a stop.

Good enough.


Boring post, no pics.

No transmission is the way to go, so I just have to couple the motor to the driveshaft now.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 6:36pm

Motor Coupler:

The motor has to couple to the driveshaft, without a transmission.

The advantages to shaft drive are:
- Quieter than chain. (Nice for electric which is already quiet)
- They don't tend to break or fall apart. (Nice for series wound DC motors, which, if a chain ever breaks, will accelerate off into low Earth orbit in a seconds without a load).
- Nothing to tangle or grab your cuffs or shoelaces or pick up gravel/grass offroad.

The disadvantage to shaft drive are:
- Coupling to the shaft is difficult. You can't just throw a sprocket on and set the chain tight.
- Machining odd couplers is hard.
- Layout is restricted, you can't put the motor in the top triangle and leave the main frame for battery compartment. The motor shaft has to go in line with the driveshaft, on the left edge of the bike.
- Balance is an issue. The motor is on the left edge of the bike.
- Alignment is difficult. The motor shaft has to be lined up in both position and angle, nearly perfectly, or the u-Joint rattles and clanks as it maxes out. A chain drive you only have to get the 2 sprockets into the same plane, the chain does the rest.

I don't have a choice, so, I have to work with the disadvantages.

This is the old tranny output:

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This is the driveshaft:

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The U-joint couples them together.

Since the motor was the hydraulic pump motor, it is mated to a hydraulic pump. So I have 4 possible pieces.

Here's the struggle:

1 - Female splines on U-joint.
2 - Male splines on Tranny output.
3 - Female slot on Motor output.
4 - Male slot on the pump input, splines on male pump shaft that drives the vane carrier (pump internals).

1 and 2 naturally mate. 3 and 4 naturally mate. I need to mate 1 and 3 (both female), using the chopped off shafts of either 2 and 4 (males). Life umm, finds a way.

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Ideally, I would just machine down the splines on the hydraulic pump shaft to match the u-joint... but while Male #4 was made for Female #3, he isn't girthy enough to satisfy Female #1.

If I use Male #2 from the transmission output, that fits the u-joint perfectly, but then I have to figure out how to mount it into the motor. It's much easier to just cut a giant screwdriver bit out of a shaft, but it's harder to mount it.

Clear as mud? Here's the plan. Add the vane carrier to the pump shaft, then machine it down to match the old tranny output, ignore the tranny entirely:

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Still don't understand? HERE'S A MONTAGE:

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I "machined" that coupler while visiting family, without my tools, in a back alley, using a masonry wheel in a wood-chopsaw, a grinder, and sander to roughly shape it (any would have been fine on its own), and then a dremel or a hacksaw to cut the teeth.

I used the last bit of hot glue still inside the glue gun I took from the sewing room (shove it forward with a pencil) and some packing tape to "fixture" the coupler to the tranny so I could mark to mimic the splines. I had 1 dremel wheel I found under the plastic in the case, and no wheel arbor (I'm using the tip of the sanding drum, the wheel broke right after I was done marking).

When people complain about not having the right tools, or not knowing how to machine things, or how expensive it is... I drown your complaints with this splined shaft coupler I made on my first attempt with a rusty hacksaw in a back alley. Just try harder.

I cut the pump in half and mounted it all up:

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Lent my welding mask away? Haven't welded more than an hour in my life? Want to tack weld it just enough so that it holds in place and I can test the spin?

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Let's go.

How about some speed control?

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 7:07pm

Speed Control:

This seems to be one of those places you can't cut corners, you gotta spend some monies.

Supercheap Plan A:

Size the battery voltage to whatever was roughly the right amount to travel highway speeds, so, just lock the throttle on with a contactor and good enough. Then use water-cooled resistors to do speed control below that. Maybe a series/parallel switch to toggle to half-voltage.

If you say "That won't work" I direct you to my hacksawed spline-coupler and wave two middle fingers, and also to past vehicle projects where it works just fine. You pump 20x the wattage through a resistor it was designed for (to keep the size down), just long enough to give you a slow start and bring you up to speed.

Plan B:

Morning after pill. It works.

Plan C:

How was the forklift controlled? You pulled all those guts out, and labelled them before you did so you can put it all back right?

Umm...

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Well... I was in a hurry. It was dark out.

What I did do was find a schematic glued to the frame, printed on wax paper, from 1969, that sat submerged in hydraulic fluid and flood water, and was still more legible than a week old newpaper. They don't print 'em like they used to.

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How hard can it be?

Two weeks later

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GE SCR control panel using 1960s electronics.

I don't know how it works. I know how it doesn't work.

Modern controllers you use MOSFETS or IGBTs, and you provide them a small signal and they turn on, and you take that small signal away, and they turn off. You pulse it the amounts that make sense, and the average amount of voltage going to the motor spins it whatever portion of full speed you're ON for.

This uses antiquated SCRs. An SCR is like a MOSFET, except you can't turn it off. You turn it on with a signal pulse, and then it just latches on forever.

To snuff it out, you have to kick its feet out from under it with a back-voltage that overwhelms it. Every single pulse. Where do you get that big of a spike of reverse-voltage? Another SCR! How does it charge backwards? Umm... coil... capacitor.. transformer... umm... well whatever, that's the theory.

It's like swearing in a foreign language. You know enough to get the impact you want, doesn't matter if you're not fluent.

From the wiring diagram I started trimming out all the pieces I didn't need that were forklift related:
- Pump motors? Cut.
- Hydraulic controls? Cut.
- Power steering? So cut.
- Horn? Cut.
- Forward/reversing relays? Mostly cut (this is called "Plug" braking, you slam it into reverse, it bleeds energy off as heat, it's impossible to recover, standard forklift operation).
- Safety switches? Cut and/or shorted so it was always on.
- Max speed contactor (shorts out speed control, just gives max speed)? Temporarily cut.

I short or open 90% of the circuit down to the bare bones:

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After cutting out all excess stuff out, you're left with some pretty minimal connections to make:
- The motor connects to positive.
- The motor connects to the speed controller.
- The speed controller connects to negative.
- The foot pedal potentiometer connects to the controller.
- The foot pedal "power on" switch connects to a contactor, or a dummy load to fool it to thinking there's a contactor there.

GET TO THE POINT! DOES IT WORK OR NOT?

This Video Sucks, I know, don't bother complaining

The speed controller is only good for around 5000 watts though. So it's enough to test, but it's not going to work on the bike. Also it's the size of a goddamn toaster and weighs 30 lbs.

If anyone has a better controller they'd like to donate, this branch of the build has bottlenecked, it'd let me continue. I'm happy to pay shipping (to Canada), the whole "built from unwanted things" is somewhat of a mission beyond that though.

...

Meanwhile, I guess it's time to put the bike together, this might actually be a thing.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 7:09pm

Actual Mechanics/Motorbike Assembly:

I don't know what I'm doing. I never took this bike apart, someone else did, I got a bin full of parts and hardware.

Front stuff at the front, back stuff at the back, maybe?

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Sort bolts, numbers might help me figure out how stuff goes together?

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There are at least 13 wrong ways, wrong orders, wrong places, and nearly-but-not-perfectly interchangeable sets of bolts that you can use to put this bike together wrong, that require nearly-complete re-disassembly again. Some places it doesn't matter if you use the short or medium ones, until you get to the place the needed the medium ones and you used them elsewhere.

The theory with this goes: "Just keep making mistakes until the only way left to do it is the right way."

I don't even know basic mechanics. I've never touched a motorbike. I don't know what side the throttle goes on. I don't know a brake from a clutch. I don't know what bolts belong with the engine I'm not using, and which hold all the cosmetics on.

If you ever try this, I recommend starting on a vehicle that is already assembled or at least with all the pieces.

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Ta da? Close enough?

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Well most of those wires might be in the right place.


Issues:

1 - Most valuable an iconic part of the bike, shown in the photo when I bought it, is not there. It's $250 to replace it. I trade the engine/tranny Honda covers for one that's broken in half and glue it back together, sort of, whatever.

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2 - Previous owner cut and threw away the front brake lines. I order some for $20 from a scrapper. Paid using real Earth dollars. Local places want $80/line. China wants $15 but I don't want to wait.

Replacement lines don't reach the manifold though...

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Because...

3 - Handlebars are bent. No problem.

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4 - Headlight and license plate light are out. $20 for the pair. I don't know how to find compatible ones at a junkyard, so I just buy them new. More real Earth dollars gone.

5 - Brake lights out. It's because he cut the wires. There's more.

6 - Horn is wrecked. So, don't unplug the spade terminals, cut the wires off flush with the harness so I can't ever goddamn find them or know they're supposed to exist there. Thanks previous owner.

7 - All cosmetic panels are broken, cracked, shattered, ripped off. I now see why the previous owner who bought it fix it up, gave up. He wrecked everything he touched. Superglue and epoxy to the rescue.

8 - No windshield, I'll have to make one.

9 - No left grip. Ordered new ones. $3, China.

10 - Speedo cable mounting clip is shattered. JB Weld to the rescue.

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11 - Master Cylinder (I learned a word!) does nothing. Brake fluid and 3000 frustrating pumps later while bleeding, fluid suddenly appears for no reason. Hurray. Brakes hold.

12 - Honda fuse cover at the handlebars is missing. Fuses are gone. Cosmetic pieces are missing. Speedo fender mount is gone. Rear middle grab handle is gone. I'm sure I'll keep finding more. I hate the previous owner now. Enough random crap that this would be a $500 bike if I had to order it, but the international Nighthawk community is very nice and everyone has parts bikes they raided the valueless bits for me.

13 - The "still good" tires are badly cracked, I was too ignorant to know what to look for. They'll need replacing.

14 - Mirrors? Said he had them, I don't have them. $15 locally.

15 - Turn signals are rubber clamps that grip the front forks. Rubber is old. It split when I opened the C-shape up. 5 different types of glue/epoxy/cement so far, nadda. Not sure what to do next with those.

That said... I paid $20 for most of a motorbike. There are worse tragedies in the world.

I buy 5 different used helmets for $10-30 each from different old timers. I don't know what style I'll want, might as well try a bunch and then buy a new one that's what I want. I don't think I'll buy full gear, but, without wasting money, helmet and gloves aren't places to skip out on on principle.

...

I temporarily rig up the throttle cable to a bracket on the forklift's potbox just because I want to be reminded this thing spins after a few weeks of mechanical musical chairs.

She's mostly mechanically reassembled. Let's get some batteries!

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 20 2018 7:11pm

Batteries:

Of the major expense:

1 - Bike.
2 - Motor.
3 - Controller.
4 - Batteries.

... I got the first 2 nearly free, the 3rd... ehn, half assed. So just batteries now.

This project sort of started when someone told me you can buy used starter batteries at the junkyard for $10/each and I thought "What could I make with bottomless starter batteries?"

I know they're not meant to be deep-cycled. I know they will have severely short life. Blah blah. I don't care. Replace 'em every other month for that price, they're worth $10 in core charge. Revenue neutral! You still could build an electric motorbike from junk.

Half-way through the build I found out, no, $40/each. Well crap, now it's not worth swapping out.

I was going to use 4 or 5 of them in the frame somewhere. Probably 15 mile range at highway speeds.

Spoiler: Ain't nobody got time fo that.

Bending the rules here...

You're now caught up to the present day of the build. I've spent the last 3 months recycling garbage tool packs. I have around 1500 good cells. ~12kwh so far.

At 200wh/mile at highway speeds, that's 60 miles.

It's about 2 milk crate's worth of cells.

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Disassembled, charged, capacity tested and marked, recharged, and sorted.

I don't know if I have room (bulk-wise) for that much lithium on the bike. They're about 1lb for 10 cells, so, 1500 would be 150 lbs... about the weight difference between engine and motor so far.

So it's pushing it for weight, and pushing it for space.

I got lots of cable from an estate sale for free (old farmer guy had 80 lbs of batter cabling his kids just wanted out of the garage, gave it away). So that's handled.

Oh, and the batteries...

For free from a local recycler. I picked up 2 each of 4x 18650 chargers and have been running them (on top of a charging bank) for literally 24/7 and 3 months straight. Because I'm persuasive. That's the bending the rules part. A random person can't get the sweetheart deal I worked out, this isn't something the average person can find from unwanted items.

The caveat is that, after I finish my rig, and figure out how to do this safely, I'm going to keep doing it and help support local community projects at the local makerspace and such. Kids (and adults) wanting to make E-bikes, kick scooters, skateboards, mopeds, go-karts, power-wheels, etc. Taking them out of the waste stream. Which is part of why I'm doing this anyway, 'cause I wish someone would've shown me how to make stuff when I was a teenager with no spending money.

...

So that's where I'm at.

To Do:
- Fix signal lights.
- Fab windshield from lexan.
- Put together some 18650 packs (I have the 4x5 holders, $20, China).
- Fab speedo fender mount.
- Fab battery cases.
- Build a charger (variac would do for now).
- And get a controller that works.

No more blogspam. Updates as they happen.

Did you make it this far? Here's a video of it "running" 6 months ago: Yes this video also sucks, I wasn't intending to show it to anyone

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by amberwolf » Apr 25 2018 2:59am

Just so you know people are reading this...this *is* awesome stuff. ;)

BTW, if theres any reasonable way to get one to you, I have a windshield from a Kawasaki Voyager (I think) that you can have--just the bare plastic).


(I also have one from I think an old Yamaha like CHP used to use a long time ago, with the metal framework, but am planning an experiment with it on SB Cruiser; when Im done with it then if it doesnt really change anything itll be available too)

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 25 2018 5:26pm

amberwolf wrote:
Apr 25 2018 2:59am
Just so you know people are reading this...
Hey, long time no see.
BTW, if theres any reasonable way to get one to you, I have a windshield from a Kawasaki Voyager (I think) that you can have--just the bare plastic).
Thanks, but the guy who sent me the smashed up cowling was kind enough to trace and outline the shape of the original windshield. I doubt anything else would fit, it's got some pretty heavy 90' folds in it. I'll buy some polycarbonate and bend it myself, cheaper than shipping. If that comes to complete ruin, I'll let you know :p
(I also have one from I think an old Yamaha like CHP used to use a long time ago, with the metal framework, but am planning an experiment with it on SB Cruiser; when Im done with it then if it doesnt really change anything itll be available too)
I was thinking that you'd be better off with a motorbike at some point too. They can look like anything, but, obviously a bike frame can carry a lot more weight.

If you register it as a moped instead of a motorbike (you'll meet the max CC limit, and need a speed limiter), insurance is like, $50-150/year from what I've heard. Fairly dirt cheap and then you can keep up with traffic. Lotsa forklift motors available for free. It'd give you more time, prevent you from having to ride through potholes, and get you access to jobs you wouldn't've had otherwise. Food for thought. I wish I'd have known how cheap moped insurance was all those years ago. Up here you can drive one 42 mph with just a learner's permit, at age 14.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by John in CR » Apr 26 2018 9:58pm

If there's no gear reduction in the shaft drive, you'll need a gear reduction from the motor to the input end of the shaft...somewhere in the neighborhood of a 3:1 reduction is my off the cuff guess.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 26 2018 11:28pm

John in CR wrote:
Apr 26 2018 9:58pm
If there's no gear reduction in the shaft drive, you'll need a gear reduction from the motor to the input end of the shaft...somewhere in the neighborhood of a 3:1 reduction is my off the cuff guess.
There is somewhere between 3:1 and 4:1 reduction in the rear shaft drive. That was one of the first things I checked. If you scroll up, it's in the 4th post, starts off with "Transmission". Bike original redlined at 11,000 rpm at 125miles per hour.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by Dauntless » Apr 27 2018 1:06am

amberwolf wrote:
Apr 25 2018 2:59am
Just so you know people are reading this...this *is* awesome stuff. ;)
Damn, I don't know how I missed this has been here.

And I see what you mean about the thanklessness of looking for info on forklift motors. I get the idea it's a Crown motor. A similar looking one was 24v, but I saw 36-48v. People mentioned 3,600-6,000w range. Sounds a bit short on power to get a big bike to freeway speed. I get the idea that if you REALLY want to work cheap you don't use a forklift motor, those looked pricey used.

But damn, I just plain can't get a bike like that without them trying to sell junk as almost new.
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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 27 2018 3:54am

Dauntless wrote:
Apr 27 2018 1:06am
And I see what you mean about the thanklessness of looking for info on forklift motors. I get the idea it's a Crown motor.
I think you mean 'fruitless', a planting effort that yields no food. 'Thankless' would be accomplishing a task that you receive no acknowledgement or recognition for. I'd be happy for the task to be thankless, as long as it beared fruit, but it doesn't even do that :p
A similar looking one was 24v, but I saw 36-48v. People mentioned 3,600-6,000w range. Sounds a bit short on power to get a big bike to freeway speed. I get the idea that if you REALLY want to work cheap you don't use a forklift motor, those looked pricey used.
They'll be whatever voltage the forklift was, which is usually 24, 36, or 48v. And they're rated for roughly 5000 watts usually. Pretty much all forklift pump motors are the same size, 7".

However, they can also be massively overdriven without issue, same as the drive motors. It's not abnormal to be able to sustain 5-10x their rated value, with only some extra cooling. Pump motors are kinda shittier than drive motors because they are not actually designed to run non-stop, they toggle on now and then to build hydraulic pressure. They usually don't (and in my case, does not) have a built in cooling fin on the shaft, so it will eventually build up too much heat.

And yes they're expensive, but, in the context of industrial equipment, their value comes in the tasks they accomplish and the regret of not accomplishing the task they need to do (shutting down a factory, not getting product out, etc). So it's the kind of thing that, if you're the buyer, and you need one that's new, you don't mess around with salvage, you pay the $4000 up front because your factory sitting idle is trivial compared to the cost savings. Which also means that if you have used industrial equipment, it's often worthless, because no one will take a chance on it.

If you needed to buy this pump motor it's thousands of dollars. Yet, from a place where the guy's entire business is restoring/salvaging forklifts, the plan for this one before I got to it was to rip the batteries out (which he did) and throw the rest in the scrap bin. That's someone with the contacts and resources to maybe move it, still not worth the labor to strip it.
But damn, I just plain can't get a bike like that without them trying to sell junk as almost new.
I couldn't find one for years, but was just looking in the wrong places.

And yeah $20 was a great deal if I needed those exact parts, but it was actually a shitty deal for a bike salvage because it cost so much to repair all the stuff. You can get bikes from a shop, with nothing wrong but the engine blown/worn, for $300. They'll usually be called "Project bikes" or "Restoration Projects", or "Parts Bikes". If I had to do it all over again, that's how I'd go.

However, I love the look of the '85 Nighthawk, so I guess I lucked out 'cause I literally would have bought anything that rolled, I didn't even know that the number on bike models is the CCs of displacement when I bought it, I knew absolutely nothing.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by SlowCo » Apr 27 2018 4:26am

What a fantastic build and very frugal with the budget. I'll be following your build and look forward to your progress. Keep us updated.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by John in CR » Apr 28 2018 8:29am

MattsAwesomeStuff wrote:
Apr 26 2018 11:28pm
John in CR wrote:
Apr 26 2018 9:58pm
If there's no gear reduction in the shaft drive, you'll need a gear reduction from the motor to the input end of the shaft...somewhere in the neighborhood of a 3:1 reduction is my off the cuff guess.
There is somewhere between 3:1 and 4:1 reduction in the rear shaft drive. That was one of the first things I checked. If you scroll up, it's in the 4th post, starts off with "Transmission". Bike original redlined at 11,000 rpm at 125miles per hour.
Simply rotate it and check the reduction. Proper gearing is everything. While your at it, stop guessing about the motor and measure it's voltage constant (Kv = rpm/volt). Then you'll know it's torque constant (Kt = 9.55/Kv = Nm of torque per amp).

I hope it all works out well for you, good enough to wet your whistle enough that you go on to build another with what you learn so you invest a bit more in a far lighter and more capable power plant and more and better batteries.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 28 2018 12:42pm

John - Just a headsup, you've got a lot of confidence relative to how well you understand things. You seem to know a few things very well which has misled you into thinking you know all things. I don't think I'll take your advice.
John in CR wrote:
Apr 28 2018 8:29am
Simply rotate it and check the reduction. Proper gearing is everything.
Far from "being eveything", "proper" gearing doesn't matter a bit. Ballpark gearing is all I cared about. Do you think I'm going to swap out the driveshaft and rear bevel gears on a 33-year-old bike and fabricate new housings and mounting plates if the gear ratio is off by 25%? It's in the correct range, it doesn't matter. If the motor's bearings and windings can handle that rotation speed, I'm fine. It can, it's in the normal operating range, and I'm fine. Done and done.

Again, if you scroll up to the "Transmission" section, you can read that I did rotate it and check the reduction. And then to confirm that I ran the specs on the bike itself to see if it was in the correct range, which it was. There's some slop in the rotation due to the U-joints, which is why I'm not certain, also, I don't care, because it doesn't matter.
While your at it, stop guessing about the motor and measure it's voltage constant (Kv = rpm/volt). Then you'll know it's torque constant (Kt = 9.55/Kv = Nm of torque per amp).
Umm, while you're at it, stop lecturing people and learn how a Series-Wound DC motor works I suppose if you don't know the first thing about them ('cause, if you know anything about them, this is probably literally the first thing you'd know). There is no voltage constant. There is no max speed. If you give the motor any voltage, it accelerates forever until it tears itself apart, the air resistance limits the power draw, or you lower the voltage. It's a positive feedback loop where faster speed means even more faster speed.

You are probably more familiar with permanent magnet DC motors or shunt-wound DC motors which approach a certain speed relative to their voltage and then stop accelerating.

The awesome thing about Series-Wound DC motors that are used all over for industrial activity for 130 years now, is that they have ungodly starting torque. I don't have to worry about torque in the slightest. My bike is 700 lbs with me on it, and the forklift it came from was 10 or 20x that weight and it *still* has to be limited to soft start or it'll rip the frame apart. If I had a controller powerful enough, the bike would do a backflip if I told it to.
I hope it all works out well for you, good enough to wet your whistle enough that you go on to build another with what you learn so you invest a bit more in a far lighter and more capable power plant and more and better batteries.
A more capable power plant?

10 years ago it was common to use a DC motor this size to power an electric car. A common comment I've gotten from EVers is that it's stupidly powerful, that I'd never need or use the power it can put out. Pound-for-pound, they're about as powerful as you can make a motor. Brushless motors are still playing catchup, the reason you see BLDCs in production EVs now is because they're maintenance-free where as DC series motors need replacement brushes every decade or so.

And... more and better batteries?

Gee, I just don't think you know what you're talking about at all.

It will will have more batteries on it than any commercially-available electric motorbike, far as I know. It'll have 12,000 watt-hours before I add a tank-pack. I've hit the limits of watt-hours-per-kg or watt-hours-per-liter. Power-wise I'm using tool packs with now 700 horsepower available at the battery. On a motorbike. It's already a big frame on a big bike (750cc), and I'm pretty sure the amount of batteries I have so far is enough to fill every available space in and around the frame without going (much?) over the vehicle's rated weight. The top of the line batteries at $5/cell are perhaps 25% better than my used ones at testing and this much capacity would cost $7000 versus, umm, free. I literally can't add more battery to the bike space- or weight-wise.

In comparison, probably the largest manufacturer of electric bikes, Zero, makes a bike that is "far lighter" as you suggest, with a battery pack 13% the size of mine. They makes bigger bikes too, but, for electric bikes mine is at the upper size.

I'm really not sure what you're imagining this "Lighter, more capable, better and more battery" bike to look like. Any bigger and it'd need 4 wheels.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by Ribiero » Apr 28 2018 1:57pm

I am loving this build thread.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by jonescg » Apr 28 2018 10:20pm

The innards of that old forklift are amazing - the things we did before power electronics eh?

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by Dauntless » Apr 29 2018 12:37am

MattsAwesomeStuff wrote:
Apr 27 2018 3:54am
I'd be happy for the task to be thankless, as long as it beared fruit, but it doesn't even do that :p
Well, I tend to see the information itself to be all the thanks I need. Sometimes I don't get it.

See, I don't know for sure, but I'd think the pump motor would be more suited. Forklift and car batteries, short bursts of overdriven, not really electric vehicle usage. The pump needs to be the energizer bunny and just keep going, sounds more like what an electric motorcycle does. But if they really are the same motor in the forklift and the pump, well, okay.
MattsAwesomeStuff wrote:
Apr 27 2018 3:54am
$20 was a great deal if I needed those exact parts, but it was actually a shitty deal for a bike salvage because it cost so much to repair all the stuff. You can get bikes from a shop, with nothing wrong but the engine blown/worn, for $300. They'll usually be called "Project bikes" or "Restoration Projects", or "Parts Bikes". If I had to do it all over again, that's how I'd go.

However, I love the look of the '85 Nighthawk, so I guess I lucked out 'cause I literally would have bought anything that rolled. . . .
I just noticed the bent bar picture. Ah, memories of BMX days.

Oh, I've looked at project bikes, parts bikes, all of which the owner was trying to make some huge profit on. Nighthawks are among the top of my list, seriously like the idea of a driveshaft. On the subject of the cost of fixing the old bike. . . .
Donorbikes.png
Pics of NEW donor bikes. New tires, new seat, money you have to spend BEFORE realizing there are broken things. And you get to pop out a new engine and sell it, so it's costing less than that price. And sparing me a lot of work. These are some good sized bikes, the dirtbike has a 21" front wheel. And getting rid of the Chinese motor sounds delightful, eh? Put some pedals on, register as a moped, and. . . .

Easy on John, he doesn't mean to sound full of himself. And good gearing will spare you some heat, etc. Some of the problems you'll end up having aren't really intuitive, it'll make no sense that it's a problem but there it is.
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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by MattsAwesomeStuff » Apr 29 2018 2:44pm

Dauntless wrote:
Apr 29 2018 12:37am
See, I don't know for sure, but I'd think the pump motor would be more suited. Forklift and car batteries, short bursts of overdriven, not really electric vehicle usage. The pump needs to be the energizer bunny and just keep going, sounds more like what an electric motorcycle does. But if they really are the same motor in the forklift and the pump, well, okay.
I think I was unclear about that.

The pump motor only charges the hydraulic system, which is only used when raising and lowering loads. And, it can easily more than keep up with full time use of such (I think for safety, if there's a slow leak, you better be able to keep the load lifted). This is a low duty cycle. Pump needs just aren't that significant.

The drive motors (for electric forklifts, obviously), have to move the entire forklift around. They have to accelerate 10,000-30,000 lbs of truck and load around.

Pump motors are basically all the same form factor because regardless of how big a truck is, the pump load is the same. They're all 5kw rated ~7" diameter pumps.

Drive motors are scaled to the size and weight of the truck. The forklift I used is about as small as they come, and even it used 2x 7" 5kw motors with cooling fans to keep them cool (one motor for each drive wheel). They're about 80 lbs each. Normally forklift motors are around 200 lbs total, probably 9"-11" in diameter. They're designed to be used non-stop all day long. They're definitely more suited to EV repurposing.

But in my particular oddball case, the drive motors were each smaller than the pump motor (though with better cooling).

I did consider finding the rear end off another '85 Nighthawk, flipped it upside down, somehow mounting it to the other side of the wheel, and doing dual-driveshaft with the dual drive motors. I've never seen a dual-driveshaft bike, I thought it would look pretty badass. But it's 70 lbs of extra weight for power I definitely don't need, and I don't know how I'd mount the driftshaft to the wheel or if it's even possible.
Pics of NEW donor bikes. New tires, new seat, money you have to spend BEFORE realizing there are broken things. And you get to pop out a new engine and sell it, so it's costing less than that price. And sparing me a lot of work. These are some good sized bikes, the dirtbike has a 21" front wheel. And getting rid of the Chinese motor sounds delightful, eh? Put some pedals on, register as a moped
You don't need pedals on it most places to register it as a moped (sometimes called "low speed motorcycle). Just limit it to whatever the speed limit is (usually around 40mph), and be under 50ccs of engine displacement.

In Canada, you only need pedals if it's an electric bicycle, but then it has to be limited to 20mph and a 500w motor. I have a Motorino Xpd (basically an electric Honda Ruckus clone) that I ride once in a while too, and that's manufactured as an E-bike.

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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by maydaverave » Apr 29 2018 4:23pm

Great build! You should of been on junkyard wars. My first bike was a 1982 450 Honda night hawk which I still have and plan on converting to EV someday. I love that bike, I'll have to live vicariously by watching this build. That radiator might of been for oil instead of water. Could be a handy part if you want to cool that thing. I am terrified of you learning to ride on a homemade motorcycle!
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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by maydaverave » Apr 29 2018 4:29pm

Actually I'm positive that is an oil cooling radiator. Probably doesn't really matter other than being coated in oil it's much less likely to be corroded inside.
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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by maydaverave » Apr 29 2018 4:38pm

If it's heavier than stock your probably going to want to add some preload to the front fork. Get some heavy schedule pvc pipe that will fit inside of the top of the suspension tubes. Add about an inch more or less till you have about an inch or two of compression total when you sit on the bike. Might want to put some fresh oil in there and new dust caps if they look dry rotted.
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Re: Motorbike Conversion - 1985 Nighthawk 750S - From Junk

Post by maydaverave » Apr 29 2018 4:47pm

You might be able to use the regulator rectifier to step down voltage for headlight and turn signals. Two parts to it. Rectifier turns ac to DC, regulator steps down voltage but does it by shunting excess current to frame but if ground goes to battery maybe work? Anyways it's the part attached to the alternator.
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