A-Lines Abound: Electric drive implosion

[MattyCiii]

I picked up the front wheel tonight, mounted it and took a few spins. Gosh this thing is a ponderous beast! I geared it quite low for pedaling- which is nice, I think I can actually get it from place to place (slowly) by human power alone. The Schlumpf High Speed Drive will be useful for adding power to the (to be installed) electric drive... but without E-Drive, it's impossible to pedal the Schlumpf in overdrive even while the NuVinci is in its lowest gear.

I seem to be having trouble with the Lefty suspension, more on that later. For now, at least I have a bike I can pedal - and can pose upright while I measure for and design mount points for the Recumpense DaVinci power assist!

[fractal]

you're gettin there matt! i really want to see how you will design the mount for the drive. this is something i might be interested in doing for another project in the near future.

[MattyCiii]

You bet!

I really skimped on the pictures, because I was running out of time to put both bikes together before leaving town on a 5-day weekend. I was highly successful... Achieved all my goals. I just didn't take any build pix
I should be able to get some glamor shots though this weekend.

[MattyCiii]

Rode the bike 8-10 miles tonight with Critical Mass. Fun times, but toting all that weight around sucked the life out of me. It'll definitely be principally powered by LiPo, with human power as an auxiliary system...

[fractal]

Rode the bike 8-10 miles tonight with Critical Mass. Fun times, but toting all that weight around sucked the life out of me. It'll definitely be principally powered by LiPo, with human power as an auxiliary system...

LOL!!! what voltage are you going to run it at? I see a lot of mid drives running at lower voltages, why is that?

[MattyCiii]

LOL!!! what voltage are you going to run it at?

I'm aiming for 12S LiPo, for ~50V hot of the charger. That's all the Castle HV160 can take. I'll probably start with 12s2p, since the frame is so unfriendly to holding bricks in the triangle.

I see a lot of mid drives running at lower voltages, why is that?

Well I wouldn't exactly consider this build a mid drive. IMO a mid drive is defined by its use of the bicycle drive gears. I'll be putting e-power into the NuVinci on the left side, sort of a parallel hybrid to human power on the right.

But as an RC drive, 50V is somewhat low versus DD. That's because the controller I chose yes, but also because the KV of the motor. The motor is an AstroFlight 3220, 8 turns of wire. This gives me a KV of 84 RPM per volt. At 50v, we're talking a 4200 RPM motor! I have to reduce that speed back down to something useful, and with the large diameter of those monster tires, I have to gear it down by like 8:1.

[MattyCiii]

Here's the bike in its rideable form:

[MattyCiii]

Here are a couple of options I'm considering for DaVinci drive placement:

Option 1:
In front of and above the rear wheel. This will bring the weight of the drive closer to the suspension pivot, minimizing the impact of that unsprung weight. The down side is that it makes the chain line longer, and I don't have a lot of clearance past that 3" wide rear wheel. The suspension triangle is very curvy there as well, which will make mounting the drive a challenge.




Or:

Option 2:
Place the drive on the left upper chain stay, a little above and forward of the dropout and rear brake. This makes a shorter chain line, and should make for easier mounting of the drive system some flat surfaces and bolt holes available on the custom dropouts). Down sides to this are moving the unsprung weight rearward on the suspension, very little heel-strike clearance, and drive system closer to road debris/water splashes.

[sn0wchyld]

ill take it there's not enough space between the wheel and the bike, between the 2 swing arms? I'd think option 1 is best, but you'll want to check that you wont end up hitting the frame under full compression. I've had a small pannier attached to my seat, and even with the smaller wheel it got hit by the tyre fairly often.

[MattyCiii]

ill take it there's not enough space between the wheel and the bike, between the 2 swing arms?

Great question. It would be really awesome to have the motor right on top of the upper arm and the large reduction pulley & freewheel inside that space. Sadly the parts I have are too big. But I think if I change some variables, it will work out. For all its stiffness and cool-factor, the DaVinci drive is bigger than the V4 drive in many dimensions. I think I'll try my V4 drive here and see if it'll get the motor where I want it. Also the large belt pulley is just a smidgen too big... I got the 5:1 pulley and I know Matt sells a 4:1, so perhaps a 4:1 pulley will fit.

It will likely require custom brackets to hold things in place firmly and correctly, but I had a great experience with bigbluesaw.com making brackets for my other bike, so now I'm confident that if I can design it, they can build it.

[adam333]

I geared it quite low for pedaling- which is nice, I think I can actually get it from place to place (slowly) by human power alone.

Haha, I bet... when I run out of battery, I'm forced to pedal mine at 10 km/h max back home...

The bike look great, cant wait to see it finished .

[MattyCiii]

I geared it quite low for pedaling- which is nice, I think I can actually get it from place to place (slowly) by human power alone.

Haha, I bet... when I run out of battery, I'm forced to pedal mine at 10 km/h max back home...

I brought the bike to Boston last Friday night and rode with Critical Mass. CM moves at about 12-15 KPH, and I was able to keep up. Hills were a killer though, and the temp was about 32c/90f. So it's definitely human power capable... I'll be doing a "ride of shame" not a "walk of shame" if the electrics fail. But it will be slow, and painful!

[MattyCiii]

I seem to be having trouble with the Lefty suspension, more on that later.

So the lefty is defective. Riding the bike maybe like 50 yards/meters, the travel would slowly lose travel till flat. I could reset the suspension by pulling up hard on the steering bar (like trying to pull a wheelie, or if I stopped the bike and lifted the front end).

I placed a call the the vendor who has seen this before, it's a warranty fix and simple to do for those with the right tools and experience. I have a cycle shop down the road that can do it. Damn, there's always something!

[Alan B]

Nice bike! Tough fitting everything in.

Pedaling my Borg is tough on the uphills with only the two speeds. Especially since the chainline is not right and it may derail with hard pedaling. Not too bad to pedal on the level, but is pretty slow.

[MattyCiii]

Nice bike! Tough fitting everything in.

Indeed. I bought the DaVinci drive with 5:1 reduction, that's a 100 tooth belt pulley, about 6" diameter. The 4:1, 80 tooth pulley would be about 5", still too large to fit into the triangle space in front of the wheel. If I can source a 60 tooth, it would be about 3.75" OD and should fit into the space in front of the wheel. I'd place the motor above the top of the triangle, and have to be a little coy with routing the belt (I'll show pixonce I get a cardboard prototype built up).

I think I can get away with 60t, which is 3:1 reduction... I bought a relatively low KV 3220 (8 turn), and I have plenty of room for the secondary reduction to be big (13t freewheel to 60t chainring - both on hand - gets me 4.6:1)

Pedaling my Borg is tough on the uphills with only the two speeds. Especially since the chainline is not right and it may derail with hard pedaling. Not too bad to pedal on the level, but is pretty slow.

I might have the pedal part licked now. This morning I upped the rear cog from 16 teeth to 20. Now with the Schlumpf drive and the NuVinci I can ride the bike uphill (slower than a walking pace, mind you). On the flats it's OK, it can get up some good speed, but acceleration is nonexistent.

[Garrick_s]

Some interesting ideas here for sure and some cool machined parts (Cha-Ching $$).
keep up the good work.

Never have been a fan of those "lefty's".
Every time I see one, the words "SNAP, CRASH, and BANG" comes to mind.

[MattyCiii]

...keep up the good work.

Thanks!

Never have been a fan of those "lefty's"...

To date I'm not thrilled either. Looks like I got the runt of the litter, "malfunctioning on arrival." With the help of my original retailer it looks like it'll be fixed no questions asked under warranty. It should have been fixed no questions asked. I'm out of town * 2 weeks on business, hope it's all fixed up by the time I get back.

[Alan B]

Rode the bike 8-10 miles tonight with Critical Mass. Fun times, but toting all that weight around sucked the life out of me. It'll definitely be principally powered by LiPo, with human power as an auxiliary system...

Sounds like my Borg. Pedaling without power on level ground in low gear is a lot of work. I don't have low enough gears to climb much at all. But when the Cromotor is powered, look out!

[MattyCiii]

Rode the bike 8-10 miles tonight with Critical Mass. Fun times, but toting all that weight around sucked the life out of me. It'll definitely be principally powered by LiPo, with human power as an auxiliary system...

Sounds like my Borg. Pedaling without power on level ground in low gear is a lot of work. I don't have low enough gears to climb much at all. But when the Cromotor is powered, look out!

Thanks Alan!
Love the CroBorg & build thread. So yeah, you have the Schlumpf High Speed Drive, so at least you have one low and one high... Enough to limp home or get a little exercise while the motor is turning I suppose.

My other build, the folding bike, has the ATS drive (1:1.6 ratio overdrive) but the NuVinci in the rear gives me lots of options. On that bike, anything over the top speed I can pedal with the ATS drive is simply too fast (~20mph). I can't wait to get e-drive on the A-Line, I'll have the suspension, geometry and strong build that can take me to much higher speeds...

[Alan B]

Yes, I also have the ATS on the Borg. 12 mph low, and 20 mph high gears. Low is for flat ground no power, and high is for pedaling along with the motor at 20-25. I wish I had the high speed drive.

[MattyCiii]

I'm considering a radical new approach to the electric drive. People please chime in with your thoughts!

Outline: Stick with mounting the drive to the top of the rear swing arm triangle. But ditch the primary 5:1 belt reduction in favor of a 5:1 (more or less) gear reduction with 90 degree output shaft. If I get the right gear head and fab up some good mounts, this should work.

Details:
Motor drive would look something like the setup shown below (original ES thread here: viewtopic.php?f=12&t=2973#p60806).
.

I would install it here, in the lower left corner of this pic. The Astro 3220 should fit nicely in that curved part at the front of the swing arm.


Another view of the target location. The motor would be mounted to the suspension triangle, and the drive cog would be about center of the space between the rear wheel and the suspension parts. Then as long as I manage the chain line well I should be just fine.


What do you think?

[MattyCiii]

I realize right angle drive has been done before, and it's hard to pull off. I'm going to paste a bunch of links below that I have been reading for ideas on what to do/not to do:

• HAL9000v2.0's Turnigy hxt w gearbox from Oct 2009
• Ken's buildposted by Sk8norcal in September 2011
• Boostjuice's gear reduction in Helical Gearbox Discussionn November 2009
• More from many contributors in Changing the direction of force, May 2011
• Salwek's angle grinder drive from April 2011

Lots of ideas and inspiration...

[MattyCiii]

I've been asked a couple of times about the motorcycle wheels. Here's some additional information:

Specific rim and tire is posted here: diy tubeless tires for ebike anyone?
And a little more about the build process: Motorcycle rim?

How's the performance?
My subjective evaluation about the setup: Since my A-Line unloaded is about as heavy as my folding bike fully loaded for touring - and since their pedal drive trains are similar, one main difference between them is the rotational mass of the wheels. There's a huge difference!

PROs of the heavy wheels:
1) They're motorcycle wheels, DOT rated. I won't likely get near their top design speed.
2) Weighing hundreds of pounds less than their design load (sub 100 lb bicycle, sub 200 lb rider), I'd be surprised if I could puncture these tires even if I ride over a bunch of sharp objects. This is stark contrast to my folding bike, whose front tire has a bunch of nicks visible in the thin rubber from my recent 2-week adventure (I got 2 flats in the front on that trip, both while stopped. If I got a flat at speed, I'd be hurting).
3) Even with defective front suspension(I've had to ride with front sus locked out), the bike eats bumps for breakfast. By bumps I'm including 8" curbs, both going up and down.
CONs of the heavy wheels:
1) Price. I paid like $120 each for the rims, which is like 3 times the cost of good bike rims. I paid near $100 for the tires, also 2.5 to 3x the cost of bike stuff.
2) Pedaling - the huge rotational mass of the wheels makes pedal biking harder. Getting the A-Line up to speed requires a slow progression up the gears. Going up hill takes a lot of effort!
3) Stopping: Once up to speed there's a lot of kinetic energy in those wheels. I'm using top quality downhill bike brakes - had I gone for cheap brakes I think I'd be a wreck waiting to happen.

I also don't have long term tests, yet. The bike is at the shop at least another week waiting for the Lefty to be fixed under warranty. And considering I'm a long way off from getting electric assist installed, I won't be putting many miles on it any time soon. Keep an eye on the thread though, I plan to ride the bike down a mountain (road) & take a video of the ride over Labor Day weekend.

Welcome to the Sphere!
~Matt[/quote]

[Alan B]

I got a rear flat in my 3" Moped tire last friday. It probably took a nail, haven't dissected it yet. I tried to ride on the tire for a few blocks to get home, but the tube snuck out from under the tire (both beads are still in the rim) and wrapped around the brake mount, tearing the tube. It was a bit of work to push it home three long blocks on a hot afternoon. Luckily it wasn't miles from home. More detail and pics in my Borg thread.

[MattyCiii]

I got a rear flat in my 3" Moped tire last friday. It probably took a nail, haven't dissected it yet. I tried to ride on the tire for a few blocks to get home, but the tube snuck out from under the tire (both beads are still in the rim) and wrapped around the brake mount, tearing the tube. It was a bit of work to push it home three long blocks on a hot afternoon. Luckily it wasn't miles from home. More detail and pics in my Borg thread.

Yes I read about your puncture... Forgot you were using a moped tire. Fixing a flat myself on my bike is simply not an option. Bike's probably too big to fit in a cab. And though all the busses around here have a bike rack on the front, I think those 3" tires are too big to fit into the racks (even if deflated, since these tires are pretty rigid). I'll have to treat my friends with pickup trucks extra nice from now on...