Several Yuba Mundo Builds

[Kiwi]

I have been playing around the last few days with my new ezee mundo. I slapped a rear 8x8 in it along with leaving the front ezee. Both on seperate systems, 8x8 48v20A, ezee 36v22amps. Can run around on the 8x8, then when the hills come hit the ezee. With both motors it hauls up hills, even with low power setups on each motor. Its not a bad set up as I still get regen braking, but am not turning a DD motor on the front. Motor speeds with this set up seem to work well together.

[teklektik]

Kiwi - I think our riding experiences with dual motor rigs are very similar. However, I chose to use the same BMC V2S gear motors front and rear so the load would always be equally shared regardless of load, speed, and throttle setting. This may not be necessary, but it has worked out well and the result is a system that reaches a few percent higher speed on the flat above what a single motor will do, but gets there PDQ. The nifty part is the available torque for hill climbing: Running rear-only, a hill may cause the bike to grind down under 10mph, but kicking in the second (front) motor will suddenly accelerate up the hill. Having the manual thumb toggles mentioned above lets you switch to two motors in advance so you don't actually ever experience this kind of slowdown and recovery... when you eyeball an impending demanding climb, you just back off the throttle briefly, kick in the second motor, and sweep up the throttle to maintain the current speed smoothly but with twice the torque on tap. With freewheeling gear motors, it all happens in a blink without a glitch.

I run the motors current limited to 800W each - 33% above the rated 600W but they are never more than warm to the touch. This dual motor approach seems a good way to easily and safely pull 1600W while keeping the ability to be thrifty on the flat. By suppressing the CA limiting for a few minutes, you can easily pull 2.4KW to crest tough hills. I have a solid 30+ mile range on a 48v 20Ah Headway pack (to 80% discharge) over mixed hilly/flat New England terrain with occasional short 15+% grades. Time will tell, but the rig does not heat or protest in any way and operates smoothly and effortlessly.

There is really not a lot of available descriptive material on dual motor builds but it seems safe to say that many of the conventional anecdotal experiences with single front motor builds may not be directly applicable - a dual motor build is (or can be) a different animal in the same manner that AWD cars offer advantages over certain (similar) troublesome control and traction characteristics of FWD.

For those readers that are leery of reported gear motor failures (stripped gears or melted windings), I can only note that most appear to have arisen from gross overpowering and high power dead starts. A Cycle Analyst is a 'must' and can easily limit power to keep these torquey motors in the specified operating envelope, making them an attractive choice for hauling a heavy cargo bike up substantial hills. I use a single standalone CA that limits total power to 800W when running a single motor and 1600W when switched to two (on the fly) with a common battery, shunt, and CA (this gimmick would not be as effective if the front and rear motors/controllers/wheels were not identical...).

[Kiwi]

Our main Yuba, me and son taking a 200l barrel full of bird netting to neighboring farm. Had to counter balance about 10 deg.

[Rifle]

Ha! If only you had to take two of those.

Finally got my friends bike together like 2 months late (just in time for winter... :/) cuz he destroyed the BMS. Gonna run 72v 22amp on a 9C 2710 rear. Might up the amps to 25 if it doesn't climb well enough. That'd put us at slighty more watts than your dual set-ups but I'm bettin' probably still not as good hill climbing since there's no geared motor in the equation. His lady lives up probably a 10% grade. Hopefully it's enough to get them up it.

[Kiwi]

I turned up at the BMX track with my kids on the back of the cargo, one of the senior racers asked for a go. This is what happened. Spent the next hour taking kids for rides around the track.

[ryan]

Hahaha! Awesome! I want to see it get some air.

[thewall241]

Nice Kiwi, good to see the yuba tearing up the track. Hey there is a cromo-lite frame on TM at the moment, not quite a d-8 but could still be a pretty solid start for a FS build.

[Kiwi]

Yeah I saw that. I really want the d8 as the shock is out of the way. I plan on cutting the frame and mid mounting a dd hub motor driving a nuvinci at the rear. I might be better off to start from scratch.

[ryan]

Hi fellow Yuba builders. Just wanted to let you know that I'm gaining ground on my v4 build with running board battery enclosures. The last of the parts are coming in over the next few weeks. I figured I'd share a couple shots along the way.

running-board 1.jpg (131.14 KiB) Viewed 571 times

running-board 2.jpg (152.77 KiB) Viewed 571 times

running-board 3.jpg (155.18 KiB) Viewed 571 times

Any other builds lately?

[ohzee]

I am going to do one in about a month or start and wow I think I know what I want to emulate.

love your holders how does that extra weight feel front wheel seem any different ?

Great work man.

[ryan]

Lol. No weight just yet. All talk so far.

My batteries get here later this week. I'll be running 18S4P (roughly 66.6v32Ah or 2131W-hr) in the running boards. It's going to be a tight fit, but I'll make it work.

My new motor (x5404) is still in China, so who knows when it gets here. I'll run the 5304 until it comes.

Here's the build thread.

[teklektik]

ryan- To minimize flex you may want to consider bolting up a front-to-back piece of angle or square tubing roughly parallel to the chainstay, under the bottom sideloader and inside the Mundo sideloader frame. An alternative might be a long rectangular solid inner panel fastened between the top and bottom decks on the inside face with cutout on the bottom for axle nut/derailleur. When you hit a bump, sideloader batteries pretty much try to launch into orbit and then re-enter to the core of the Earth. There's a lot of mass in play there that really wants to have its way; if it's attached to the sideloader, the unsupported area of the sideloader near the axle nut tends to flex up and down while bolted points around the edge are held in place.

With a separate metal/rigid battery box hung out on the sideloader things aren't too bad, but in your case the Mundo LDPE decks may result in cell assembly twists and flexes on every bump (Bzzzt! Bzzzt!).

I have sideloaders made of HDF which are loads more rigid than the Mundo ones, and they still get twanged pretty good by attached battery boxes. Anyhow - just a heads-up for something to keep your eye on - or maybe a little time-filler add-on while you're waiting for parts to arrive .

[itselectric]

Hi fellow Yuba builders. Just wanted to let you know that I'm gaining ground on my v4 build with running board battery enclosures.

Ryan:
That is an excellent idea for battery storage! May I copy your idea on my next Yuba build?

How are you planning to keep the enclosure water proof?

Ken

[Kiwi]

Hi All.

I have ordered 32 Yubas!
Anyone in NZ want one?

Also in development, universal battery case internal 300x150x110 (ping upto 36v20 or 48v15) or lipo.
Designed for Yuba but will fit most rigid frames.

Front and rear torque plates available, also nuvinci rear adapters available, both static and adjustable for chain tensioning.

Perhaps, later, a midmount bracket. Have worked it out on paper, still cant fit a 9C or xlyte, maybe if we turned of the spoke flange.

In build a 72v conversion using ezee batteries, lyen controller, NC 2808 front.

Kiwi.

[ryan]

Ryan:
That is an excellent idea for battery storage! May I copy your idea on my next Yuba build?

How are you planning to keep the enclosure water proof?

Ken

1) You can only copy if you promise to improve it. (and then share it here for others to improve on)

2) I'm unsure right now. I'm thinking of wrapping the packs in some yoga mats for padding. And then heat shrink most everything else. I don't typically ride in down pours so if it's generally resistant I'm probably alright. Any other ideas?

[ryan]

teklektik - You're absolutely right. As I'm laying everything out it's becoming clear that the boards are not as solid as I thought. Your strut support may do the trick. I wonder if I can cut a square tube at the ends to leave a single panel at both ends. Then drill some screw holes and screw that piece into the first and last running board screw holes. If that makes any sense.

[teklektik]

Makes perfect sense - I considered the same approach. But, after thinking about it, I don't believe there is much gained by fastening to the Mundo tube. Just bolting the stiffener tube end to the deck adjacent to the sideloader tube leaves little measurable deck to flex. But, if your stiffener tubing is thin enough not to shim up the deck too much (steel instead of aluminum), it certainly won't hurt to do as you describe.

My current batt boxes and decks are temporary but I tried to do a fair job with the decks because of the heavy Headway cells I'm using. So far they are working out okay without the extra strut. I did counter-bore the bottom of the decks to clear the protruding insert tops so the decks lie flat on the sideloaders for support, but I think you already may have this effect because of the mounting slots in the Mundo decks...

[teklektik]

ryan - Apologies if this is obvious but just trying to pass along some past Mundo-think :

Flex in the long narrow sideloaders isn't in itself bad, it just needs to be appropriate for the inherent dimensional stability of the internal cells and the flexibility of the cell interconnects. Something like a long naked Headway battery composed of Headway plastic spacers and bus bars or cylindrical cells with spot-welded bus tabs will do badly with much flexing. But, break this into several smaller bricks with internal stiffeners then interconnect those with flexible wiring, and all is well.

So - the plan seems to be to do the best we can with the twangy sideloader nightmare and then package up cells appropriately instead of necessarily relying on dimensional support from the decks...

On another front - here's a little anecdote that you can make of what you will:
I am temporarily using heavy plastic toolboxes for battery enclosures with flat plywood stiffeners in the bottoms. They are quite sturdy and are rigidly affixed to the sideloaders. A couple of weeks ago I ran over a 1" stick about 24" long on the roadside - no big deal for fat tires. Except this time The Evil Spirit of Jousting caused the branch to leap up and jam between the immovable Earth and unstoppable front of the right battery box. A split second later I had a thoroughly impaled and shattered battery box . Fortunately the boxes are intentionally oversize for battery experiments and the upper impaled 1/3 was empty of vital organs...

Definitely a freak accident but it brought home the increased vulnerability over frame packs -- sideloader packs can do with any help we can afford to protect them from bits of the world that will inevitably get in the way.... (e.g. Kiwi's steel ammo boxes)

[ryan]

Ouch. Any photos of the carnage?

[teklektik]

Nope - no camera at the time and I couldn't ride with the piece of forest sticking out of the bike for a later shot. If there had been flames, sizzling, and melting, the discarded case would have been photo-worthy.

[Alan B]

Lining with plywood in the forward and inside sides might be prudent. Even thin plywood would slow down a blunt spear significantly.

[teklektik]

Very good idea - no room on the side but I can slip a little armor in the front w/o problem. I'm done experimenting with different XsYp setups and so hopefully can replace these boxes with a final aluminum 'thick deck' version this Spring.

[ryan]

I want to see some closeups of your build, tek. Do you have a build thread up? Post pics here if you have them.

[teklektik]

I've been putting a build thread together with a fair bit of detail.
Thanks for the interest - I'll get it posted very soon.

EDIT: 2WD Electric Yuba Mundo Build

[es2150]

Things looked great until I realized yuba has no disc brakes.