2 Stroke E-chaser

August, time to vamp up our race bikes! The E-crowd is talking up Sept15 as ‘the world championship’ of motorized bikes and there's Oct race at Grange as well. I even heard there was some crazy guy driving down from Michigan. So, a day to build, a day to post, here goes:

For me, running mid-pack with a tire just in front, someone else’s tire under an elbow, is more fun than leading a race if out in front alone. So I’m bumping this mid-size 9-Continental 2806 to its’ limit (maybe beyond); gonna chase me some peppy 2 strokers.
http://www.ebikes.ca/store/store_motors.php

Issues: Replaced the dead headset and bouncy pogo forks with CaneCreek and RockShox forks on sale, $25 & $110. The fork was still too springy so set the lockout halfway; works. Also upgraded the mechanical front disk brake with a sweet ballbearing activated Avid B5.

I hope this thread becomes worth reading for 'ya Paul. Tantalizing outline:
Day1 Intro & safety upgrades

Day3 Modding the rear drops

Day5 Gearing, trueing, protection, reroute shifter cable, spacing

Day7 Beefing up motor phase wires

Day9 Amped up controller & connectors

Day11 Electric calculations, fancy batt box, tucking lipo harness

Day13 Tire selection (hope to uncover a surprise)

Day15 Lap times/impressions at Adams Kart track

Day17 Speedometer (bye bye CA), lights/reflectors, squirrel tail

Sure thing Paul, a properly maintained bike is safer at 30mph than a poorly maintained one at 15mph!

Nothin' like the free market Baird. You're a bit innovative and less volunteer work in the infield let's me join the e-crowd to cheer my buds to victory! I've always wanted some of those motocross gals that carry the big cards that no one reads cause of pretty belly buttons.

Gonna be some robust power with 100% of the torque getting transmitting to the axle. That is, the hub motor uses its’ axel as the motor shaft (a roundabout design). The shaft (axel) is fixed to the frame with nuts. A spinout can result in ripped out electrics and a discharged rear wheel, dangerous!

Turns out the wide spacing of the Chinese 150mm dropout is perfect to build in torque arms (without arms!) as part of the rear drop outs. A long 5/8” black chainring bolt replaced a shorter ¼” chrome shifter hanger bolt. Both sides have 3 screws and ample 3M DP-460 epoxy securing the aluminum inside the dropout zone. There’s now an added ¾” to clamp the torque and achieve spacing.

The 53T front ring and 13T rear sprocket enables pedaling out of turns. http://www.sheldonbrown.com/gears/ (29mph@100cadence)
To remedy sluggish shifting there’s trimming, shaping, and rerouting of the cable. Now it’s 5th gear off the line and quick click to 7th. Going from 6speed to 7speed freewheel helped center the wheel. After much obsessive tweaking, the interwoven 2cross Sapiem 13ga spokes yield a strong and <1mm true wheel. ¾” painted pvc with hose clamp provide protection for the motor wires exiting the axle.

Day 7 beefing up motor phase wires

In peak performance situations, one electric weakness is hot motor phase wires. Getting 12ga wires thru the axel was a challenge which I botched. In the struggle to fit 12ga I removed a clear layer of insulation. When trying to force the wire thru, the inner insulation split exposing the copper.

Wimpy me opted for 14ga to replace the stock 16ga. At the time, I wasn’t sure there was a quality non-sensored controller around. So in hindsight, I could’ve pulled out the 5 tiny hall sensor wires and inserted the 3 beefier 12ga motor phase wires with the sensorless controller I've now decided to go with. I'll be noting the temp of wires at the track.

Once apart, the wires attach right out on top out in the open. Careful putting the side cover back, the magnets are powerful enough to decapitate a finger as it snaps close.

Two regrets: 1) modest 14ga rather than 12ga and 2) could've machined out the slit in axel from 1/2" to 1+" (eliminate the need to cap the axel with pvc, there is plenty of axel protruding on the left side where the motor wires exit)

Hey Rich,

I’ve pushed the lyen 6FET controlled to its’ limit, 30A up to 84V(20S), maybe as high as 2.5K off the line at the June16 Baird race. For 40Amps, Ed (Lyen) sent me his MarkII 12FET sensorless controller housed in a bigger box; can you say bigger ‘heatsink?’ He also programmed these for me. I think the 12FET one is set for about 105-110 phase amps with the 6FET at 80 phase amp. I've wondered about bumping the timing to 115% for a little extra performance but seems to me you'd get the same results by running 45A. Really think above 35A for the modest 9C is getting into diminshing results.

Lyen has been the most reliable person I've ever done business with.
http://lyen.com/

I’m fitting all my controllers with the same connectors: Andersons for the power as they are practical to plug/unplug 1,000s of times; tiny hard to see JSTs for the 3 wire throttles. The blue painters tape is to hold down the stout Radio Shack velcro 'till the 3M DP-460 epoxy sets.

I'll be getting into the lipo, and simulator calculations later this week. Building the batt box is kicking my butt.

Rich, did I miss sump'in? What are you pushing 50A/4500+W thru?

The 4 5S 8Ahr lipo bricks can power 12-15 racing laps but voltage would sag below 64V. Another 4 smaller 5Ahr bricks should keep the voltage 68+volts to the checkered flag. The 4 5S 8Ahr lipos are in series for nominal 74V just as the smaller 4 5S 5Ahr lipo bricks are. The 2 series packs will be connected in parallel for 13AmpHr of power at 20S/74Voltage or 20S2P.
http://www.ebikes.ca/simulator/

Though I'd see 3K+ spikes approaching 4K, a more constant and realistic power level would be:

Fresh charge 84Volts; under load 76Volts: motor power 2388/750W= 3.2 h.p.
After 12 laps 76Volts; under load 68Volts: motor power 2134/750W= 2.8 h.p.
Average = 3 electrical horsepower
(almost equivalent to a 6hp gas, not fast as a 5.5hp Morini, close to competitive with modded China Girls yet certainly not dominate)

I'd love to find out I could push a little more power (?45A) and not melt down in 15min!

Pic1 The batt box challenge:
Pic2 Not sure if this helps but these lipo bricks are paired in series to double the voltage up to 45V. Then the pairs are connected to other pairs in parrellel to increase the available Amp hours. For diagram, click on this: http://http://scriptasylum.com/rc_speed/lipo.html My lipo configuration is 5S in 4series with 2 packs in parallel. Since there isn't 20S, just tell it 4series in the 1st diagram. Then at the bottom instruct it to show 2packs in parallel.

A series of unfortunate setbacks. A dull drill bit melted the lexan in 3rd foto. Different brand connectors didn't quite fit, ect. . . be back on track this weekend!

"Im just thinking...." As I am, and it's an intriqueing line of thinking that we all follow when looking for that last drop of power! Disciplining oneself to not run WOT can get very expensive. More later in a "amps vs volts" and "heat; the evil limiter" discussion.
[Edit: max performance can be had running 24S higher voltage, but. . the 20S allows top speed to be reached where the amp draw falls off and the motor gets to cool a tidbit. I dropped $1500 for 14laps of riding in Oct2011: didn't have time to install current limiting and self discipline evaporated once the race got underway; flamed an 8brick lipo pack and later smoked my new Astro3220 inrunner]

The batt box challenge is coming together;
1 soldered bullet connectors onto controller,
2 shortened lipo power wires as needed
3 padded lipo brick from box,
4 added shrink tubing to wires traveling between the lipo,
5 screwed and epoxied 3/16" lexan/1/16" 7075 aluminum,
5 cut/epoxied velcro strapping.

Weight is 16.4lbs close to 2lbs per brick & 0.4lb for light thin walled box. Dropped the box from 30" on its' corner several times. Note the red oval on bottom. The box wedges perfectly into the frame. With only 2 straps and 1 plastic tie, it'll remain solidly fixed and would be tough to dislodge when I crash.

Time spent building this box has taken almost half the time of entire bike. Don't know about you, but building a motored bicycle is pretty enjoyable.

Gonna look it over for safety, see if I can reinforce a bit.

And the batt box is finished. This took a really long time, partly cause of our heat wave but more importantly, my remark about just a single plastic tie latching the world's highest energy density available to the public, in place, got me to thinking. After my big lipo pack flamed last October at Grange, figure my reputation can't take many more hits, and why not be safe?

Added 2 small reinforcers, tiny #2 screws 'an epoxied slivers of sheet aluminum. Several packs of velcro squares, mixed a bit of super glue with the adhesive backing, provided padding plus you could hold the bike upside down and the lipo bricks would stay put. Found a spot for another small plastic tie. A little electrical tape on corners, super glued, on some of the corners. It's been an honest effort to make the lipo safe.

The build is all downhill from here. Install tires, slap it together and ride. In pic2 notice the big plastic tie top of center box wrapping around the seat tube, maybe a' hold 100+ pounds.

Settled on the Schwalbe Big Apples as they were closer to being slicks than the Kiniptions, though both look good. Both the stock tires and the BAs are stated to be 2.15". The stock ones measure 1 & 13/16" wide with a diameter of 24". The BAs measure 2 & 1/16" wide with a diameter of 24 & 3/8", good for an extra 1/2mph top end.

They have some flat protection and along with some pretty thick thorn resistant tubes, I can trust 'em.

Didn't realize how sleek this build would turn out. The wheel, chain, and brakes aligned perfectly. But check out how close the tire comes to the battery support bar now. There's 1/16" (2mm) to spare.

I've got a Century run coming up Sept 1st (other bike) but am charging right now. Should get time to take it for a spin 'round the neighborhood Monday 8/27.

Additional edit: One issue e-racers deal with that gassers don't, is 'charging' at the track. One either needs a 2nd(3rd?) lipo pack, or an efficient charging setup. Charge too fast your lipos swell and die a few charges later. Charge too slow and you're not 100% for the final race. http://www.bmsbattery.com/alloy-shell/27-alloy-shell-600w-lifepo4li-ionlead-acid-battery-ebike-charger.html This 600W charger takes an hour to charge back 8 laps of hard racing. Charges 6A/84Volt; easy enough on your lipo, usually just in time for your next heat or race.

OK, I'm happier now. Picked up the back end for the good 'ole back tire spin and . . . the pedals spun with the wheel ???#@*?? Everything looked perfect but the 13-28 7speed Harris Cyclery freewheel had an inner diameter of 44.5mm. The 9Cont hub motor had a ball bearing protrusion of 46mm diameter. Snipped plastic ties, pulled wheel/hub off, used a dremel to grind the soft aluminum to a 44mm diameter, remounted wheel;

Whaa-laa, 39mph on a 90% charge, front brake is smooth enough to progressively release when diving into turns, BigApples stick noticeably better, and the extra 16% power (30 to 40Amps), though still modest, is definitely felt. When I 1st ran 30A, the speed sorta scared me. This upgrade doesn't quite do that, so my impression is that it's not really monsterously fast.

A school bus passed, pulled off in front of me, with blinkers going. Rather than get caught behind 'em, I jumped out into the car lane WOT in a 40mph zone. Didn't take long to match the flow of traffic; it's fast enough! 5 short laps sprinting around the park warmed the motor phase wires a bit but not hot to touch. Gotta keep an eye on this. I may install some proper 12ga wires before 9/15.

Total bike weight, 66lbs.

Last June, I ran:
18S/90% charge, 1min:18sec p lap
20S/100% charge 1min:15sec p lap; both at 30A

My calculations for this revamped 40Amp setup is 1min:9.75sec p lap, yet I sense not so much.
Gotta get out to Adams soon for lap times, heat monitoring, and general checking out this setup.

Heat after 8miles of juicing, 200f on the motor, the motor wires warm, but not worrisome. If I can get time to drill cooling holes for the motor and bump wiring to 12ga, maybe 45amps, maybe.

The issue with amp limiting in the controller is: I want lo-speed thrust, but that's where both motor and controller heat derive. The bike will run 39mph for 14+min, but give it a 15% grade/22mph (sorta like accelerating out of corners) and the motor magnets fail after just 4min. Not much point in setting for more power then expecting myself to hold off on the throttle in the adrenline of the race.

Tires stick a bit better but the 60psi rear/55psi front didn't inspire. Will run softer tires next neighborhood trek.

Need every little advantage considering such a marginal e-motor. For a dark track, hows about a mini-headlite! Found a 140 lumen headlite at Lowe's for $23.69. Cut out a foot of wire, resoldered epoxy/velcroed it to my front number plate. The 2 kitties are the main reason it takes me a long time to get much done. They're young and a blast.
Foto1my buds Foto2 solder Foto3 headlite Foto4 bike Foto5 fence 90'

Lipo's a bit new, need to cycle some, yet ready to race, which is only a day away.

Ran 12ga wiring into the motor, got rid of the PVC protector and ground on the axel end so that it (rather than a stob of pvc) now protects the wires when I crash.

Drilled axel center a little to 9/32nds; fitted 2 12ga wires, stripped the insulation off 3" of yellow & super glued 100lb mono-line there then overlaid heat shrink and lastly some vaseline lip jelly (Foto2) Tough to get thru, but managed by pushing/pulling on both ends. Sewed cotton protectors over the insulation and added a plastic tie to keep the wires away from moving parts. Halls removed as the controller is sensorless.

42mph top speed in 550' at start, with 39mph at the finish. Cornering improved with 55psi rear and 50psi front tire pressure. 8laps of hard running raised external motor temp to 145f in 85f air; 250f OK: running a 12lap final would be no biggee except. . . 45min later, the enclosed motor read 115f: the heat issue is this, "Can I start the final race with a cooled down motor?" [Edit: Cooling between races didn't prove to be a great issue, 45min to an hour for the motor to cool without a fan.]

Saturaday am I'll be picking up some dry ice in Bako before heading over to Adams. The fan in foto4 will blow over the dry ice and into the motor venting holes.

None of this will mean as much as tomorrow's Bairdco's race at Adams (then MBR's at Grange Oct)

Foto1 12ga upgrade Foto2 3rd wire a toughie Foto3 finish Pic4 machined motor casing

Had a blast at Adams 9/15. Motor an easy going 200f after 6 lap heat1 run. Set out a block of dry ice with batt fan blowing over it into the motor. Oh what a difference, the motor cooled in half hour. The cooling holes and fan are all that are needed, (unless ya have almost back to back races). After the 12 lap main race, inner coil read 109C/228f degrees. About right with a tad to spare.

The 40A/74V was perfect. No melt down on a hot 100+ day. However I believe the power max has been reached. It'll handle 45amps but it would just turn into heat with no output power gain, or very minimium. [Edit: Later at Grange Race, 45A ran even cooler not to mention there was greater torque; I'm changing my mind that the 9C can really race at 50A! recommend 18S/45A with hi-125phase amp setting in the controller]

1st heat: ran with the mid-speed class, mostly modded 66cc China Girls
Hit 41mph (once 43) down the 660'? straight with acceptable thrust out of turns, but not quite what I had hoped. Had clipped in to pedal and was 1 legged at the start only 9th into turn1. Had I skipped the clip in and stood to pedal think about 6th of 12 into the 1st turn was possible. Finished last about 100yds behind next to last racer. These guys can really throw their light weight 2strokes around the turns and I guess make mid-40s topend. Impressive little racers.

2nd heat: ran with the less competitive stock class
still got a mid pack start due to clipping in (drat, no problem clipping on my full 26" bike, just not this lowesh tuck in racer). Actually led 1 lap but Edion? #8 rode well in the turns and away from me in the straights (212cc HarborFreight) Finished 2nd.

Main 12 lap race:
It was a repeat of heat2. I pulled up beside #8 once but never took the lead. Pedalled my butt off, tucked low up the straight (light worked great). Finished 2nd.