My first ebike build: custom-built KMX-based electric velomobile

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nicobie   1.21 GW

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by nicobie » Oct 11 2021 4:21pm

It will be interesting to see what you come up with for gearing for all those speeds.
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my eTownie build thread: http://endless-sphere.com/forums/viewto ... =6&t=23701
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Oct 11 2021 8:29pm

Waiting on him peddling that moped wheel at speed. Don't think he will like it. Keeping an open mind and hope it turns out. Then I would think about a more durable wheel.
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Oct 11 2021 11:59pm

nicobie wrote:
Oct 11 2021 4:21pm
It will be interesting to see what you come up with for gearing for all those speeds.
The idea is the following:

-26/39/52T triple up front
-Schlumpf HS drive with 2.5:1 when engaged or 1:1 when disengaged
-34-11T 7-speed in the rear
-20" equivalent drive wheel using 16" moped rim

For hill climbing with the motor disabled in my shortest gear, this yields 2.7 mph with a 60 rpm cadence in 1st gear in the 26T ring. For cruising 25 mph on flat ground with the motor disabled and the HS drive not engaged(for maximum pedal efficiency), I get 90 rpm in 7th gear using the 52T ring. For cruising 70 mph on the highway with the HS drive engaged and the motor enabled, I get 100 rpm in 7th gear with the 52T ring. For careening down the highway at 100 mph, I get 142 rpm. Human power could be a factor for the vehicle's entire operating range, and perhaps account for 10% of the motive force doing 100 mph in a hard sprint with a lot of rider effort(~400-500W of the ~4-5 kW needed to maintain that speed).
ZeroEm wrote:
Oct 11 2021 8:29pm
Waiting on him peddling that moped wheel at speed. Don't think he will like it. Keeping an open mind and hope it turns out. Then I would think about a more durable wheel.
It's not the rotating mass of the wheels that will hinder my cruising speed so much as it is the rolling resistance of the tires. I'm not so much concerned with the amount of energy it takes to accelerate to speed as I am with the amount of power required to maintain speed once it is built up.

I really want to see how the Mitas MC2 fare. Almost all motorcycle and moped tires have a Crr value far too high for pedaling to be viable with the motor shut off, but solar race car teams use the Mitas MC2 for its low rolling losses. I need a Crr of under 0.009 for pedaling to be on the edge of viable, but preferably under 0.008 in order for my build to be significantly faster than a normal bicycle when riding without assist in spite of the added mass.

I already pedal this thing with a heavy 17 lb hub motor in the rear wheel, often shut off, with its cogging losses making themselves known(~50W @ 30 mph by themselves), so an extra 7-10 lbs of rotating mass that induce no cogging losses in the form of heavier duty rims/tires/rotors over what I currently have will be a relative drop in the bucket. As it is right now, I can turn the motor completely off without any power to kill the cogging losses and pedal it to 35 mph in a sprint, with aerodynamics nowhere near as good as what the next shell will have, and holding 23 mph for miles at a time isn't difficult. Even at 23 mph, aero drag is still most of my losses, and aero drag matches everything else combined around 20 mph, so if I cut the drag to 1/2 to 1/3 of what it currently is, it will make a major difference and the math suggests would more than make up for the extra rotating mass in most riding conditions. If I get the aero right, cruising speed on the flat with the motor shut off should be around 25 mph with 150W at the pedal cranks.

It is an experiment for sure. I may find that the system is too lossy, and may have to go back to Greenguard tires or perhaps Marathon Pluses up front, and just keep the Mitas MC2 in the rear only just for the flat protection, given how catastrophic a rear-wheel blowout would be. But I'm after the holy grail of mechanical reliability at car-like speeds, while maintaining the ability to be pedaled with the motor shut off. Solar racing cars are what I'm looking at for ideas. Eventually, this thing will have 150W or more of solar panels on it as well, which factoring in the losses at the charge controller, would be enough power to run 20+ mph in direct sunlight without draining the battery and without pedaling, but add pedaling and push that up to ~28 mph without drawing down the battery.

I'm trying to build the ultimate apocalypse vehicle after all. Electric/pedal/solar hybrid would be very versatile, especially if it was a bicycle at its core and could be used as such if all the other subsystems failed. Using wheels that can fit a 20" BMX tire also means the most common tire size available in the U.S. can be scavenged for use from junk bicycles to keep it riding, even if in handicapped form. Too bad no one makes biodiesel fuel cells for sale, otherwise that would also be on a planned list of items to add, given that being able to carry a 1 gallon jug of cooking oil and go an extra 1,000+ miles would be sweet!
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Oct 12 2021 12:35am

Mitas MC2 seem great the speed rating is 62 mph. That is fast enough for me.
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by goatman » Oct 12 2021 6:40am

in an apocalypse, is the gallon jug of cooking oil for deep-fried roadkill?

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Oct 12 2021 9:01am

ZeroEm wrote:
Oct 12 2021 12:35am
Mitas MC2 seem great the speed rating is 62 mph. That is fast enough for me.
I also keep in mind its weight rating for that speed as well. When you account for the kinetic energy built up at 100 mph, the tire may still be solid at that speed, albeit handling performance may not be consistent!
goatman wrote:
Oct 12 2021 6:40am
in an apocalypse, is the gallon jug of cooking oil for deep-fried roadkill?
It would be for running a biodiesel fuel-cell generator, if one existed on the market. Lets say the hypothetical solar panels failed or the weather was not cooperative, and I didn't have a working electrical outlet. Mixed with some lye, the oil would be an emergency backup to keep the battery charged. And if the electric drive fails, there's always pedaling it like a normal velomobile. If the pedal drive fails but the electric drive works, a throttle and the solar panels keeps her going.

The idea is to find as many fuel sources as possible to keep it running, and design it in such a way that only one of them needs to work at minimum.

I already carry enough tools to basically rebuild the bike on the side of the road if I have to(about the only things I don't carry is a truing stand and a pocket welder), and in my 63,000 miles of use so far, I've had to use each of my tools at least once, and never had to get someone to tow it back. I often ride 30+ miles from home and I do not have AAA.

Tires, brake pads, and brake/shift cables are the currently-existing vehicle's weakest links mechanically. The Mitas MC2 in such a light weight application would almost be flat proof and might last XX,XXX miles per set(versus 4,000-5,000 miles for the Schwalbe Marathons), and heavier duty brake calipers/pads in a hydraulic braking system might list XXX,XXX miles with regen doing most of the light braking and a cable brake caliper at the rear wheel for emergencies.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Oct 12 2021 9:27am

the bike is a truing stand and they sell JB weld.
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Oct 13 2021 7:16pm

ZeroEm wrote:
Oct 12 2021 9:27am
the bike is a truing stand and they sell JB weld.
With the body shell on it, it makes a very poor truing stand. Which is one of the reasons why I made the tail section removable.

Not sure that JB weld would be sufficient to repair a broken frame, but if cracks were spotted early it might prevent them from getting worse.

Perhaps I should add a tube of JB Weld to the toolkit, just in case I need it. The steering spindles are a weak point.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Oct 13 2021 7:22pm

Always wonder about spindles. Mine have taken some hard hits and no issues yet. I forget about your trike being covered. I just use an old bike here to true my wheels. Have a roll of cardboard 5" tall with a hole in the middle and set my motor on that and start lacing my spokes then move to the bike when it time to true and tighten down. I can not sit long so it takes me 3-4 days to do one.
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Nov 09 2021 8:35pm

A list of new components that have arrived over the last few months up until today, that are sitting due to lack of time to install them(I can't take this trike out of commission because I use it for work and idiots keep smashing their cars into the Milan which was supposed to be my backup bike and is in need of repair yet again):

-adam333's rear suspension kit, w/ gas shock option
-ASI BAC4000 controller
-Leafbike 1500W motor w/3T wind built into a 20" wheel w/freewheel compatibility
-DNP Epoch 7sp freewheel 34-11T gearing range
-new KMX proprietary 32-spoke wheel hubs
-new KMX rear derailleur hangar

I'm about to order a 16x1.6" motorcycle rim with 32 spoke holes and a Mitas MC2 16x2.25" tire and matching innertube for my Leafbike motor. I've been intending to get some Schwalbe Marathon Plus 20x1.75" tires but everywhere I go they are out of stock. Currently seeking info from Schlumpf about whether they have an HS Triple available, as some have bought a Mountain Triple, and looking into a new torque sensing bottom bracket that is built in a way that I can chamfer it. I don't have any new batteries on the way yet, as I'm waiting for battery hookup to get more Panasonic 21700s in stock so I can build anything from a 20S5P pack to a 20S7P pack.

I have a lot of work to do to get this vehicle prepared for the performance it will have. The 1500W 3T wind Leafbike motor paired with a BAC4000 controller will allow car-like acceleration from a stop up to its estimated top speed of over 70 mph.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Nov 13 2021 6:55pm

The leafmotor is 36h is it not. You doing some modified lacing?
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Nov 14 2021 5:07am

It is. My KMX spindles are 32h though. Which I meant to say I needed two rims for them. I was initially intent on doing all three wheels. I still might, but I'd like narrower rims than 1.6". Looking for 1.4", especially for the front, with a 32h spoke pattern. The rear wheel is getting the 36h pattern, which is commonly available and one with a 1.4" width is already on the way. I need the rims narrow enough that I can still fit normal 20x1.75" bicycle tires if I must, but with the option of using Mitas MC2 16x2.25" tires. If the Mitas 16x2.25" induce too much rolling resistance for it to be pedalable faster than a normal bicycle with the motor shut off, then I'd simply keep just the rear tire as such and switch the front to Schwalbe Marathon Plus. The narrower DOT rims also keep the weight of the rotating masses down, which should help keep it reasonable pedalable.

Getting this right is going to be a fine balancing act. It needs to be easy enough to pedal sufficiently that it retains some of the speed advantages of a velomobile over being unfaired, while also being durable enough to cruise at highway speeds when the motor is in use. I'm also going to have to make custom spindles that are sturdier than the stock ones, and a roll cage.

If I pull this off with the KMX, I'll be able to improve upon it by making my own custom platform. That platform would ideally be suited for a range of vehicles beginning with an unmotorized but overbuilt velomobile of about 70 lbs, and ending with a single-seater car of about 150 lbs with no bicycle drivetrain at all that has roughly one horsepower per pound of vehicle and an accelerator/brake pedal/rack & pinion steering. Sharing the platform between this range of vehicles allows a wide range of applications to hopefully keep production costs down by increasing volume, with the end goal being a base vehicle that is an affordable non-electric velomobile with aerodynamics comparable to a DF velomobile. The demand for the electrified velomobile and car versions would drive production and sales of the platform up to keep per unit costs down.

The car version would be sufficiently light that it could get away with using ebike parts for the EV drivetrain, and all of the peak power density that those parts entail. A hubmonster in the back and two MXUS motors up front modified to function similarly to Grin's all-axle motors would be really sweet. It would require 4 controllers(the hubmonster is a 6-phase design) and a pack of LoneStar batteries to pull off. Imagine what 0-120 mph in under 5 seconds would be like!

That said, I'm a long way from any of this being a reality. I've got to refine my prototype a bit. Riding it on a regular basis allows a lot of issues to be discovered that will need to be addressed when I make a fully custom design. KMX made a very reliable and reasonably safe product, for traveling ~30-35 mph. I want to increase that to 70 mph while adding as little weight as possible.



Also, on the subject of my current vehicle, I did add in the second Greenway 15.6AH pack in parallel. I made a custom battery housing out of coroplast so that I can continue mounting the batteries below the front boom, and the box extends almost 1 foot ahead of the bottom bracket. I'm now getting a 150-200 mile range at 30-35 mph on a 1.5 kWh pack. The total weight of the vehicle is 90 lbs unladen. I'm still running 1,500W peak, and I may soon increase that to 2,500W. Given that my pack voltage is limiting my top speed, I have not seen a top speed increase with the second pack, even though the voltage sag at 1500W is noticeably reduced. It's still about 45-46 mph depending on state of charge of the battery and how hard I pedal. It feels deceptively stable at top speed: my Avid BB7 cable pull brakes are really at their safe/reliable limit for a predictable panic stop around 35 mph, even though I have panic stopped from much higher speeds(and it was quite harrowing to do so). I have a hydraulic brake system in my possession that is uninstalled, because I need to make a fluid reservoir for it since the stock one is woefully insufficient for the job, considering I'm not a fan of melting the brake lines from boiling brake fluid.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Nov 14 2021 7:13am

Thought you were talking about your rear wheel. My front 20" are 32h. 32h is starting to be a trend. Grin's front motor is 32h.

30 mph is about all I want to go. Feel this is the edge for me, any sand, pot holes or dodging anything gets exciting. I'm sure a wider track and more weight would help. For me to really go faster would need a heavier setup and would not hardly pedal. Can run 3200w watts. Have max set at 2600w currently which 2000w is all that is needed. There is a big difference from 1500w to 2600w, same for going to 3200. It's just more acceleration not more speed for me. 750w - 1200w will keep me at top speed until a there is a good hill.
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Nov 14 2021 11:38am

ZeroEm wrote:
Nov 14 2021 7:13am
30 mph is about all I want to go. Feel this is the edge for me, any sand, pot holes or dodging anything gets exciting. I'm sure a wider track and more weight would help.
Also, you'll want hydraulic brakes. Cable pull brakes need semi-frequent adjustments, and can even go out of tune during the course of one ride. Their lack of consistency in application can make for some interesting emergency stops, especially when careening down a hill at 50+ mph just to see the traffic light at the bottom of the hill change from green to red.

The 39" wide front track and positioning the seat as far to the front as possible with it reclined as possible(the 26" rear wheel being the limiting factor) really helps. Mine feels stable even at 60 mph, which considering I don't even have a rear suspension yet, was beyond my expectation. The 2" added wheelbase I'll get from the rear suspension and the additional seat recline that will be allowed by going to a 20" rear wheel should improve this further. At these speeds, downforce matters. I think my footholes are preventing significant frontal lift given the curved front bottom of my shell. I designed it this way for clearing speed bumps and potholes, but the next iteration is going to let less air in through the bottom in the interest of drag/lift reduction.
For me to really go faster would need a heavier setup and would not hardly pedal. Can run 3200w watts. Have max set at 2600w currently which 2000w is all that is needed. There is a big difference from 1500w to 2600w, same for going to 3200. It's just more acceleration not more speed for me. 750w - 1200w will keep me at top speed until a there is a good hill.
I find that I can do a lot with only 750W. My flat ground top speed is still the same with either, because of the low voltage applied to the motor(46.8 Vnom pack). Whether 750W or 1500W, top speed of ~45 mph requires hard pedaling to reach. Climbing hills is the only reason I use more power. 1500W is enough to keep up with street traffic with the cars being driven by idiots that accelerate faster than they need to, and 750W is enough to keep pace with drivers operating their vehicles with efficiency in mind, both settings using hard pedaling during accelerations.

There is a few pounds of unnecessary weight I could cut by ditching the coroplast and steel frame and learning to make a carbon fiber monocoque, which would free up enough weight in the budget to install a steel roll cage to reinforce the monocoque and provide crush protection, steel rear swingarm bolted to the monocoque, and a bucket seat/safety harness. Or if me or a friend learn to weld titanium and I'm willing to spend some coin, swap the steel for titanium. I think keeping it at 100 lbs and still pedalable, while able to safely sustain highway speeds, is just barely at the edge of possible.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Nov 14 2021 2:00pm

I like the idea of Titanium, can not find much to work with locally. Strong as steel but half the weight but much heaver than Aluminum. I follow your progress, hope you do well. I'm not into speed anymore so only adjust my front brakes yearly, regen does 90% of the work. Don't plan on modifying my trike maybe a bigger ah battery or a phaserunner and less voltage. In the 60's somewhere. Going to go back to 1.5" wide front tires the 1.35" slide to much. Thought about going to 24" front wheels, maybe the 22" neptronix was talking about, if tires are available.
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Nov 14 2021 4:58pm

I just took a ride at 2,500W. Holy shit is it a world of difference. I've owned cars that were slower than this from 0-25 mph. 0-30 mph took about 6 seconds with hard full-effort pedaling, so there may have been about 3,200W total going to the drive wheel(CA3 said I was pedaling with 722W peak). I was able to do 45 mph up a moderate-grade hill on this setting, same as it can do on flat ground.

I am really looking forward to a much more powerful 72V/3T wind setup with full suspension, hydraulic brakes, sturdier tires/wheels, and a significantly more streamlined body shell. Right now, it's kind of dangerous. 35 mph is roughly the maximum safe cruising speed, even though it's capable of going faster.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Nov 15 2021 7:16am

:lol: Yes, it's great. Running a 7T leafmotor at 72V 40a with a top speed of 30 mph only takes a few seconds. Slowed my ramp up a few milliseconds to take the edge off. Can out run any car off the line and across the road. Put a power limiting switch (3 levels) to keep me from wasting power. If i'm crossing a road just flip it up to 100%. Most of the time have it set on low 800w - 900w with me pedaling it pulls most hills and makes me work. Open road 2 level around 2000w is all that is needed. Can not pedal that fast (only 28mph) so it's all on the motor. I don't need the 3000w but is nice to have at the flip of a switch.
by The Toecutter » Nov 14 2021 4:58pm

I just took a ride at 2,500W. Holy shit is it a world of difference. I've owned cars that were slower than this from 0-25 mph. 0-30 mph took about 6 seconds with hard full-effort pedaling, so there may have been about 3,200W total going to the drive wheel(CA3 said I was pedaling with 722W peak). I was able to do 45 mph up a moderate-grade hill on this setting, same as it can do on flat ground.

I am really looking forward to a much more powerful 72V/3T wind setup with full suspension, hydraulic brakes, sturdier tires/wheels, and a significantly more streamlined body shell. Right now, it's kind of dangerous. 35 mph is roughly the maximum safe cruising speed, even though it's capable of going faster.
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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Nov 22 2021 11:50am

nicobie wrote:
Oct 11 2021 4:21pm
It will be interesting to see what you come up with for gearing for all those speeds.
I heard back from the company that makes the Schlumpf drive.

They can only do the HS drive in a 130BCD configuration, meaning 38T is the smallest granny I can fit. So I could have a 38T/46T/56T up front and an 11-34 in the rear. This would give me a 60rpm speed in low gear of 4.1 mph if I have a 16x2.25 Mitas MC2 tire on the drive wheel with an outer diameter of 20.5". This is borderline acceptable for a low gear. I'd be able to do 108 mph at 140 rpm cadence in top gear, and cruise 70 mph with a 90 rpm cadence.

I've inquired about a Mountain Triple as an alternative.

In the longer term, I am looking to go to a 108V+ system and one of the new high voltage FOC controllers that are going to be available soon, so that would be a good match.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Nov 22 2021 12:09pm

I copied this from another topic, but below are some simulation results, with the assumptions outlined.

Laden mass: 120 kg
CdA: 0.06 m^2 (new body shell planned. The current one is at least 3x this value)
Crr: 0.008
Pedal input: 500W (full effort)
Drive wheel: 20" diameter
72Vnom battery pack
Leafbike 3T wind 1500W motor

4kW limit with 150A phase current, I get the following:

0-30 mph 4.4 secs
0-60 mph 15.7 secs
1/8 mile 11.9 secs @ 52.3 mph
¼ mile 19.5 secs @ 65.3 mph
Top speed 71 mph

8 kW limit with 250A phase current:

0-30 mph 2.8 secs
0-60 mph 9.9 secs
1/8 mile 10.1 secs @ 60.3 mph
¼ mile 17.0 secs @ 67.8 mph
Top speed 71 mph

10 kW limit with 250A phase current:

0-30 mph 2.6 secs
0-60 mph 9.2 secs
1/8 mile 9.8 secs @ 61.1 mph
¼ mile 16.7 secs @ 68.0 mph
Top speed 71 mph

As I get stronger, the bike will get faster. If I were to do a bunch of squats and train like a pro athlete to get to the point where I could squat 300 lbs at my 140 lb weight and make about 1200W at the pedal crank for ~15 seconds at a time, I could get significantly faster, especially considering the acceleration from the motor starts to reduce dramatically after about 45 mph.

8 kW limit with 250A phase limit and 1200W pedaling:

0-30 mph 2.5 secs
0-60 mph 8.7 secs
1/8 mile 9.7 secs @ 62.1 mph
¼ mile 16.4 secs @ 69.8 mph
Top speed 71 mph

10 kW limit with 250A phase current and 1200W pedaling:

0-30 mph 2.3 secs
0-60 mph 8.1 secs
1/8 mile 9.4 secs @ 62.7 mph
¼ mile 16.1 secs @ 69.9 mph
Top speed 71 mph

Also, there are ebike controllers that can go to 130V, but they don't have the features I'd like. If an FOC controller of about 2 lbs were to come onto the market that could do 130V and output at least 250A phase current(such a controller may be out soon in fact), and I were to pedal with 500W instead of 1200W with the motor limited to 10kW, we get the following results for the ultimate theoretical configuration with this motor running a battery pack ~130Vnom:

0-30 mph 2.5 secs
0-60 mph 7.4 secs
1/8 mile 9.0 secs @ 74.3 mph
¼ mile 15.0 secs @ 84.7 mph
Top speed 118 mph

Which would be quite bonkers for a vehicle that is still perfectly functional as a velomobile if the batteries run dead. :twisted:

If things go post-apocalyptic in my lifetime, it would be the perfect vehicle to have because it would be transportation that requires as few resources as possible to keep operable, with pedal power and solar power as possible motive sources. And even if things stay relatively normal, it will be cheaper per mile than taking the bus or light rail, and a lot more convenient.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by CONSIDERABLE SHOUTING » Dec 26 2021 1:30pm

This thing is so cool Toecutter. The info you've provided is also a big help for future builds!
I have to ask, because 3-wheelers interest the hell out of me- this Velomobile, and forum favorites like the Deathbike (RIP) make me wonder just how fast one could be made. Like could you make a velocart and be laying down times at the strip with a quarter mile in the 10s? I seriously think you could with some of the data you've provided, but whether through multiple hub motors or though a dedicated motor like the transaxle on a car I'm not sure.

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Dec 26 2021 1:39pm

CONSIDERABLE SHOUTING wrote:
Dec 26 2021 1:30pm
Like could you make a velocart and be laying down times at the strip with a quarter mile in the 10s? I seriously think you could with some of the data you've provided, but whether through multiple hub motors or though a dedicated motor like the transaxle on a car I'm not sure.
I think so too, but the hubmotors available off the shelf at the moment are not up to the task. Custom motors and/or modification to existing motors will be required. Mid drives could do it, but reliability will be an issue and they will impose consequences and tradeoffs not to my liking. The battery and controller technology available commercially is certainly there, and the motor technology has existed for decades even if it may not be available to hobbyists.

My eventual goal is to build such a vehicle with one horsepower per pound of vehicle. I think upper 8s in the 1/4 mile and 0-120 mph acceleration in 4.5 seconds is possible. My current vehicle is nothing near that.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

CONSIDERABLE SHOUTING   1 kW

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by CONSIDERABLE SHOUTING » Dec 26 2021 1:47pm

The Toecutter wrote:
Dec 26 2021 1:39pm
CONSIDERABLE SHOUTING wrote:
Dec 26 2021 1:30pm
Like could you make a velocart and be laying down times at the strip with a quarter mile in the 10s? I seriously think you could with some of the data you've provided, but whether through multiple hub motors or though a dedicated motor like the transaxle on a car I'm not sure.
I think so too, but the hubmotors available off the shelf at the moment are not up to the task. Custom motors and/or modification to existing motors will be required. Mid drives could do it, but reliability will be an issue and they will impose consequences and tradeoffs not to my liking. The battery and controller technology available commercially is certainly there, and the motor technology has existed for decades even if it may not be available to hobbyists.

My eventual goal is to build such a vehicle with one horsepower per pound of vehicle. I think upper 8s in the 1/4 mile and 0-120 mph acceleration in 4.5 seconds is possible. My current vehicle is nothing near that.
That's what I was thinking too- Liveforphysics had a comment somewhere recently where he compared his bike to his Model S Plaid and what it would take mathematically, and it seems to me going full Aptera-scale aero is the only way. And at those power levels you'd have to use motorcycle gears and chains too- I think you could still pedal-drive it, but to be frank that's far out of my knowledge base and I'm basically talking out my ass.

Would the hubs not be up to it because of magnetic cogging, cooling needs, or just due to needing to take several steps in quality to remain moving at those speeds with that weight? I imagine its really a combination of all 3 factors.

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ZeroEm   10 MW

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by ZeroEm » Dec 27 2021 12:45pm

The draw back is trikes don't handle well at these speeds. Luke and dogmandan raced bikes, i'm sure you and read up on lukes and ask dogmandan about it. Seems like fun but not for me i'm getting to old and don't heal as fast anymore.

A fast velo on a race track would be something to think about.
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The Toecutter   100 kW

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by The Toecutter » Dec 29 2021 4:39pm

ZeroEm wrote:
Dec 27 2021 12:45pm
The draw back is trikes don't handle well at these speeds.
True. A lot of that has to do with their narrow track and short wheelbase compared to a car or a motorcycle. I can't speak for other recumbent trikes, but my KMX is stable in a straight line to at least 70 mph, and can confidently make lane changes on a rough road at 50 mph(both have been done downhill). As far as cornering performance goes, it is not very good compared to an economy car, although it might be able to corner with more lateral Gs than a 30-40 year old truck or SUV before tipping. I measured speed through a corner I took and later took a tape measure to the site to approximate my turning radius and found I can consistently get about 0.7 Gs lateral acceleration according to a calculation based upon the data I took. I haven't tipped it yet, but it was at its limit when taking that corner and just 1 mph faster would probably have had it up on two wheels.

Adding a rear suspension kit, which will allow me to recline the seat further back for a lower center of gravity while extending the wheelbase an extra 2 inches, in addition to potholes no longer being as capable of launching the rear of the trike into the air, will improve cornering. How much so remains to be seen.

There are tadpole configuration motorcycles that can out-corner most cars. I don't think my KMX will ever come close to those due to the unique design parameters of my project, but if I can get its cornering capability in terms of lateral Gs comparable to an economy car using cheap tires, I'll be quite pleased.
Custom electric velomobile, 2500W: viewtopic.php?f=6&t=110298

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Re: My first ebike build: custom-built KMX-based electric velomobile

Post by Triketech » Dec 30 2021 10:41am

Recently graduated to the Speedgeezer Class, an old man with an E-Trike......
Been tweaking the trike(s), Scorpion FS26 with various drives for 6 years now. Started with Catrikes, but found they weren't getting any awards with velocity and bumps and upgraded to HPV. Test rode Stein, ICE, trikes to compare before buying. I learned a few things along the way that may be worth considering.

At 50 MPH downhill on a Catrike Expedition bumps and small potholes can shove a trike over a lane. Over about 25 MPH suspension makes a huge difference for speed, as does wheelbase and Center Of Mass (COM). I mounted my battery below the boom to optimize COM and balance. Image

At 50 MPH downhill on an HPV FS26 with tuned suspension down the same hill the trike stays bullet straight. At least without a hubmotor. Add a 9 lb hubmotor and the tail begins to bounce again.

I run a MAC 10T with a 2.15 Big Ben on 24mm rims and 3 way tunable gas shock. The added unsprung weight of the MAC becomes evident at speeds over about 15 MPH by 40 MPH is capable of lets say some cheap thrills. Keep in mind I bought a trike after retiring from a decade of shifterkart racing so triple digit speeds an inch off the ground don't tend to phase me.

The majority of my riding is 15-25 MPH, although plenty of long steep elevation and 1800 watts and that may be occasionally exceeded, so my current rig is "good enough for now". :)

I think the ideal configuration is a mid drive with motor behind seat and belt drive to the suspended wheel. The motion of the suspension accelerates at a rate of velocity squared, so doubling maybe tripling the moment forces, well you get the idea.

Best luck with it, I'll continue to observe.

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