reikiman's picture

Drag Coefficient, Range, and doing More with Less

Phase 2 of my Lectra project is coming. Phase 2? Read back in my blog in previous Lectra Conversion Diary entries for more details. In Phase 2 I have a full fairing which is meant to make a shell around the entire motorcycle and make it extremely aerodynamic. The idea is to explore vehicle efficiency as a way to increase range.

I've been doing some research .. Cabin scooter and faring design resources from around the Internet .. Go-one Velomobile .. Velomobiles .. 5th generation civic hatchback - improving aerodynamics .. Basjoos Tells All About His "95 MPG" Aerocivic .. and it seems that there can really be a lot of gain from aerodynamics. I came across a couple forum websites where people are discussing ideas on improving aerodynamics of gas cars and other ways to increase gas car efficiency, and they're getting good results. Yeah, they're still 100% addicted to oil but at least they're doing something about the underlying problem and they are getting good results.

Yesterday I did a bit of measurement so I could have a baseline to compare future performance. I found a simple way to ... Measure the drag coefficient of your car ... If you click through to the instructables site you'll find formulas and a spreadsheet. I haven't run the calculations yet, but I've got some numbers. The process is very simple. You take your car or motorcycle or whatever, accelerate up to approx 70 km/hr (45 miles/hr) speed, and then start coasting (in neutral) and measure how long it takes to coast to a stop and speed at various intervals during the coast-down. The formulas in the spreadsheet are able to tell you the actual drag coefficient number. But there is an interesting pattern even without having yet done the number crunching.

I went out with three vehicles (below) and made several runs with each. I have an ipod with a Belkin voice recorder attachment, and during the coast down I called out the speed at 40/35/30/25/20/etc miles/hr intervals. This afternoon I listened to the audio and wrote down the time points for each of the speeds. Making several runs lets me get an average and to account for differing wind conditions (there was little wind) or terrain (it's very flat around here) etc.

1999 Chevy Tracker: 40->10 miles/hr takes approx 60 seconds

2004 Honda Rebel 250: 40->10 miles/hr takes approx 40 seconds

Lectra: 40->10 miles/hr takes approx 25-30 seconds

The idea is that the more quickly the vehicle coasts to a stop, the greater the wind resistance, or put another way the worst the drag coefficient. But this also measures rolling resistance.

I'm a little surprised the Tracker came out the best here. It's shaped a bit like a box, with very little in the way of aerodynamic niceness to it. But on the other hand motorcycles do have these bits hanging out all over the place ..sooo...

The Rebel has a windshield.

The Lectra, since it doesn't have a transmission, that may have introduced some electrical or mechanical drag. With both the Tracker and the Rebel I could put them into neutral (both have manual transmissions) and coast properly, but the Lectra doesn't have a neutral because it doesn't have a transmission.

I think the weight of the Rebel and the Lectra is comparable. The Lectra is a lot shorter than the Rebel, but it has 220 lbs of lead acid batteries on board.

Oh yeah, doing more with less...

That is a phrase Craig Vetter said during his DVD discussing the motorcycle efficiency contest and the fairing I have .. he says he got the phrase from Buckminster Fuller, who he 'followed around' for a couple years. When I heard that phrase come out of Craig's mouth it crystallized for me an idea I've carried for years.

What makes compact fluorescent light bulbs interesting is they emit the same number of lumens by using less electricity. That is doing more with less.

A vehicle that's more aerodynamic can move and use less energy to achieve the same end. I think the Honda Insight, for instance, gets most of its fuel efficiency gain from being small, light, and aerodynamic. The Geo Metro after all got 60 miles per gallon without having a hybrid drive train. Mini-experiment: the wrath of roof racks is a meditation on the negative effect of roof racks on fuel efficiency.

Popular science and Portland

See this is why I love Oregon ;)
Portland was ranked #1 for America's greenest city

"The PopSci folks looked at electricity use, transportation habits, "green" living, and recycling habits".
"It says half its power comes from renewable sources, a quarter of the workforce commutes by bike, carpool or public transportation. And it has 35 buildings certified by the U.S. Green Building Council".

I am suprised that San Francisco ranked number 2 on the list!

reikiman's picture

The three wheeler could be running soon

One of my vehicles is a three wheel motorcycle...


I got it 1 1/2 yrs ago through an ebay auction, meaning I did not build the thing. I started to register it last year but during that process the thing stopped working. So for the last 9 months it's been sitting idle while I've focussed on the Lectra. It's been this big white elephant sitting in the driveway to walk past and occasionally think about and get frustrated. I tried several times to get it running but.. no luck.

This afternoon I decided to wire up a controller to the motor completely bypassing the existing wiring. And.. it runs. Yay.. meaning, now that the Lectra is pretty much finished I can spend a few cycles on this trike and get it running too.

Let's see how many electric motorcycles I can own...

Electro-saki conversion saga

Feb 8, 2008
I've started a project that I hope will have me commuting to work, when spring arrives, on an electrified motorcycle. I've owned a couple motorcycles and now ride a Triumph Bonneville 750cc. The Bonnie is a great bike, but I'd like something 'greener'.

I began by buying a Kawasaki 400 from someone here in Syracuse.
It has a disc brake up front and a moderately heavy frame which I think will accept the weight of the batteries. I've removed all of the ICE parts and gas tank hoping to sell bits and pieces. so far I've recouped 90% of my purchase cost.

I have not bought any parts of the conversion yet, just been doing lots of research here and other places on the WWW.

My plan is this, so far: MARS Electric motor (mounted under the seat - above the swingarm), a Sevcon controller, belt drive and separate LED lighting powered by something like the new DeWalt LiFePo 32v pack. I think I'll try a 48 volt system
(maybe 70 Amp hours per battery) and see how it goes. No solid thoughts yet on the BMS/charging portion or the gauges.

For now, all I have for pictures are the donor bike on the trailer &
then stripped of all Kawasaki motor and in the workshop.

davew's picture

The Right Tool

There is an old experiment. You take a bunch of students one at a time and give a them two boards and a rope. You tell him/her to cross a room as fast as possible without their feet touching the floor. Most students tied the ends of the rope around the boards, held the rope in the middle, and shuffled across the room. Some tied the boards to their feet and walked across the room. The average time for these students was a little over two minutes. Then they performed the experiment again with a different set of students. This time the experimenters provided one board and a rope. Without exception these students tied one end of the rope around the board, grabbed the other end, and hopped across the room. These students averaged a bit over a minute and a half. Better. One last experiment and a fresh batch of students. The instructions were the same except this time no boards and no rope. These students crawled across the room on their hands and knees. Their average time was 23 seconds. I was in college twenty years ago when I read about this, but in made an indelible impression. The finding is that our thinking can be handicapped by the tools at our disposal. Sometimes the best solution is no tool at all.

Before I gave up my car I took the time to figure a bunch of stuff out. How to do the shopping, how to get to my hair cuts, and dentist, and doctor, and work, and how to cruise for sweet chicks who are into nerds. Actually I never figured that last part out, but I took the plunge anyway. A couple of things I hadn't figured out yet like how to get back to Iowa to visit my mom. Well it's been a little too long now so I need to figure out how to do it. In the interest of full disclosure I actually I did go back once a while back when my dad fell ill. I rented a car (mea culpa) and drove 14 hours each way (may the Sierra Club have mercy on my soul.) I am bound and determined to get to Iowa again this time without laying waste to the Midwest.

The solution is simple, slick, and actually way more convenient than flying or driving. Did I mention cheap? It's cheap, too. Amtrak! I'd heard about it before, but never ridden it. Get this, from 100 yards outside my front door I catch a little local bus. Five minutes later I'm in downtown. That's $1.50. There I catch the Denver bus to Union Station. That's $3.75. Then I catch the train to Iowa. Add another $83. It will actually be necessary to have a car at the other end, but only for 60 miles (mea maxima culpa) so add another $69. This is a grand total of $245.50! Not too shabby compared to an airfare of $560 plus the mysterious charges that get tacked on after you agree to the rate plus the usurious airport parking charges not to mention the date rape of the lower atmosphere. The other cool part is... remember I said a car takes 14 hours? Well so does the train. Except I don't have to drive. And they'll cook hot food for me. And it's over night so I can sleep away most of the trip without risking a head-on. And I can take my bike if I like. A friend of mine rides this train to Chicago six times a year or so and he says the seats are more comfortable than business class on an airplane. Totally sleepable. Did I forget anything? Oh, yeah. You don't have to strip naked and get probed before you get on a train. You just walk on.

Cars are tools to be sure (as well as some of the people who drive them), but so frequently they are the wrong tool. It's just the guys in the white coats handed us one so we feel obligated to use it for just about everything. Once deprived of this crutch so many more options open up and most of them are better. I may be crawling on my hands and knees, but I'm having the time of my life.

jstept's picture

The Rezistor - building the drivetrain

HUGE thanks to my friend Arden for helping me assemble the drivetrain. A fellow member of the Oregon Scooter Club, Arden has an amazing shop with machining and welding capabilities. He probably saved me over $100 in machine shop costs, as well as providing some of the raw materials.

First I had to cut the fat end off the axle (lots of pretty red sparks!). The fat end is normally where the gears go, but I have no need for it and it's in my way. Arden used his lathe to cut a 1" hole in the center of the sprocket so it could fit over the wider ends of the axle. We then machined a steel ring with a 17mm I.D. and 1" O.D. and then cut it in half; this allowed us to center the sprocket on the axle.


I had to cut a big slot in the V9A engine case near the left bearing to provide clearance for the 33-tooth sprocket and chain. Things were still pretty tight inside the swingarm, so putting the sprocket on the axle was a fairly convoluted procedure. We first had to position the sprocket, then slide the axle through the sprocket and bearing, then attach a split collar that clamps to the 17mm axle shaft with set screws, then fit in the split steel ring between the sprocket and the axle. I adjusted the location of the sprocket to center it in the swingarm slot, tightened the set screws on the collar, then Arden welded the sprocket to the collar and the collar to the axle.


The advantage of using an old engine case for a swingarm is that the front connection to the scooter frame, the rear connection to the shock, and the axle bearing are all exactly where I need them and perfectly aligned. The main disadvantage is that I now cannot remove the axle from the swingarm without cutting the welds on the sprocket (or maybe by removing the left bearing; I haven't tried this yet). Hopefully I picked the right gearing and won't need to change the sprocket. Arden almost talked me into abandoning the engine case and going back to my idea of building a swingarm from scratch (see my previous posts with photos of the wood 2x4 swingarm mockup). I still think this would have been more work, with a lot more welding and potential alignment difficulties. If it turns out that I weakened the engine case too much with all the cutting, I may have to start from scratch anyway.

To mount the right bearing, Arden had some 3/8" aluminum plate from which he cut two 2"x3" pieces, then used his lathe to bore a hole in one of them with the same O.D. as the bearing. I needed two plates because the axle stops just over 3/8" short of the motor mount plate. I fastened the plates to the motor mount plate with a screw in each corner, after aligning them using the engine case (which now includes the captured axle). Although I was careful to position the bearing plates such that they were clear of all the various internal bits of the swingarm, I didn't pay attention to where the screws fell relative to the motor, so I ended up only being able to install three of the four screws. Redundancy can be helpful sometimes.


The next step is attaching the 3-phase Etek motor to the motor mount plate using four 3/8" screws into the outer four holes provided in the motor. Positioning is fairly critical, so I first used my plywood template to locate the holes and make sure they were clear of the internal swingarm bits. I fit the chain around the sprockets to check the tension, and discovered I needed to locate the motor shaft a little further from the axle; this required that I cut more out of the engine case (fortunately it's aluminum). I also learned that the 11-tooth motor sprocket will need to sit really far out on the shaft to align with the axle sprocket, so I'll probably have to extend the motor shaft with some of 3/4" rod and a screw into the hole in the center of the axle.


jstept's picture

The Rezistor Headlight

The Vespa 50S Special originally had a 6V 15W headlamp. The old lens was partially obscured with overspray from past rattlecanning, but the previous owner gave me a brand new headlamp when I bought the scooter from him.

In any case, I wanted to switch to more efficient LED lighting and run it at 12V, so I bought five MR11 LED lights on eBay. I think these are intended to be replacments for the halogen spotlights commonly used in low-voltage lighting systems that you commonly see with exposed wires. Each of them is a cluster of 19 LEDs emitting "cool white" light, as opposed to the warmer yellowish light of halogen and sodium incandescents. I'm hoping the brighter white will produce a more distinctive effect and help make the scooter more noticable. Each MR11 is rated at about 0.78W, so the entire headlamp should draw less than four watts. I think this is a big improvement over incandescent.


First I spent a while rubbing the lens of the old headlamp with paint thinner to remove the spray paint. Then I sawed off the back end of the curved reflector and found a spider that had died inside. The five MR11 lamps just fit inside what remains of the reflector and the front lens. I cut a piece of black acrylic plate to about the size I needed to mount the lamps, then created a template to help me align the lamps on the acrylic. I drilled a hole for each of the lamp leads, used JB-weld to attach the lamps to the acrylic, then wired them all together in parallel. Then I epoxied the acrylic plate to the lens with some bits of plastic scavenged from an old wireless mouse transmitter.


I had originally planned to use the bottom three lamps as the low beam and the top two to be the high beam, but I abandoned this scheme to simplify both the alignment and the wiring. Also, I figured that for an urban vehicle, the primary function of headlamp is to make you more visible, with the illumination of the road in front of you being of secondary importance. Plus, I'm pretty sure that Oregon doesn't require a high beam on vehicles.

Interestingly, I didn't need to pay attention to the polarity of the leads for these lamps, which is not usually the case when working with LEDs. The internal wiring of the lamps seems to include a diode to allow current to flow in both directions.


Overall, I'm pleased with the results. Each of the lamps produces a fairly concentrated spot, and I did a fairly good job of aligning them all, but the lens spreads out the light somewhat. There is an adjustment screw in the bottom of the headset with which I can aim the light higher or lower. I think it will still be pretty visible and a big improvement over the old lamp.

jstept's picture

The Rezistor - Main Power Check

I figured it would be a good idea to check the function of all the major components, so yesterday I hooked up the motor, controller, contactor, throttle, and one of the batteries. I have not yet purchased the main power cables, so I had to make do with whatever spare lengths of monster cable and bits of 18 ga wire salvaged from previous LED and cold cathode lighting projects. I also haven't purchased the switches yet, so some of the final contacts were made just by touching a wire to the contactor lead (this will be a keyswitch that initiates main power) and then touching two more wires together (this will be a rocker switch to engage forward or reverse motion). This probably wasn't the safest approach, but it was good enough.

After some fiddling, I finally got the motor shaft to turn, both forward and in reverse. (My creation LIVES!!! Bwahahahaaa!!!) I spun it up to full throttle, and didn't have any problems with the BMS of my 20 Ah YESA battery cutting out due to high current draw. But keep in mind that this was under no load, after all.

Two important things I learned through this exercise:

1) I will need a separate switch to engage forward motion after I engage the main power and before I start turning the throttle. If I turn on the main power while the forward switch is engaged, this results in a controller fault message. I was hoping to just be able to turn the key, twist the throttle, and go, but I suppose pressing one more button to engage the drive isn't much different than pressing the starter button on my ICE scooter.

2) THERE IS A MISTAKE IN THE WIRING DIAGRAM that was included with my controller. This took me a couple hours to figure out. Beware of this error if you are using a Sevcon Millipak SBPM controller. I don't know if this one-page diagram was produced by Sevcon or someone else, but the wiring is shown correctly in Sevcon's user manual. Basically, the throttle lead should connect to pin 10 on the molex connector instead of pin 11, otherwise you will get an "accelerator wire off" fault message from the controller.

Now I need to fit all these pieces in the scooter and figure out how much 4 gauge wire to buy. At $3.50 per foot for the stuff, I don't want to get much more than I'll really need.

Hybrids just do not make any sence to me anymore

Okay so I had some time this morning to write up a quick entry for the issue that kept racking in my brain at 6am
this morning before I went to work. So had to jump on the forum of course and write a blog about it! :?

The issue that I am dealing with is about Hybrids and how they are still half gas/half electric.
Why is it that electric vehicles have been around since the 1800's???? if it seems like we have the technology
and resources to build them and sell them and take less gas vehicles off the streets, why isn't this happening??
I have been pondering over this all morning.
I of course understand that this will take quite some time for this to happen.
Just why isn't more and more of it happening? Does that make any sence ? :?

CONVERT IT - By; Michael P. Brown

I happened to borrow the Convert It book from David. I startd reading it over the weekend
this would be a great book to really read through and gain information on how to build an EV, especially
for those who are completely new to the Ev world such as myself.

As it makes sence to me " Don't replace your car- Recycle it"

Convert it; explains why Ev's are so much more cleaner and more simple than the Internal combustion engine.

I am still reading the book and find myself getting more and more excited about electric vehicles
I also realize that I am seeing and realizing a lot more about our environment (still) than a lot of others around me.
Which kind of freaks me out but I feel like my view points are changing and I am changing to be indifferent :)
One day at a time ~

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