CETMA Largo Cargo Bike

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kevinscargobike   1 W

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CETMA Largo Cargo Bike

Post by kevinscargobike » Jun 06 2018 10:47pm

I got my feet wet with DIY assist by converting an older Yuba Boda Boda with a Bionx kit to using a Mac 10t, Phaserunner, CA and a Sempu torque sensing bottom bracket. I figured these parts would move on to a front loading cargo bike when I found one used, but it's fun having a mid-tail cargo cruiser that's easy to park and goes 28mph.

The Boda Boda I'm riding belonged to my wife, who is now riding a Riese and Muller Packster 80. I've been shopping for a used front loading cargo bike for two reasons:

a) to have a locking "frunk" on a front loader (multi-stop shopping trips, leave a laptop bag with the bikes while chasing our kid around a playground, etc)

b) so that I can break it. The Packster is daily transportation that we rely on.

My top two choices were either a Bullitt or a CETMA, with each having different strengths and weaknesses. I like the narrowness and relatively square cargo area of the Bullitt, along with the light weight, but I dislike that it doesn't allow for wider tires, and seems like it would be a challenge to fit a 138mm Mac cassette motor. The CETMA, being steel, will fit the bigger hub no problem, and it also has room for 2.4in tires (if not larger), it's down side is that it has a wider frame under the cargo area and some trusses that make box-building a little less straightforward.

I had the good fortune to find a great deal on a CETMA Largo on Craigslist in another city where I was on a family trip over memorial day weekend, and the timing just barely worked so that I was able to sneak away for an evening test ride, buy the bike, and then the next morning I took it to a freight shipper and sent it on it's way.
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The bike is a grey color that I really like. It has a built in rack, which is something I find hugely useful, mostly for being able to lock the bike by backing up to things.... and it has a full 36v Stokemonkey classic setup, running with a belt drive to a Nuvinci N360, which I'm not 100% sure I want, but it was a good enough deal that it's almost like that was all getting thrown in for free.

The frame is bi-partable, which meant that it could be shipped on a single palette. Thinking it would arrive while I was out of town, I initially had it shipped to a friend's business, but last friday I saw in the UPS tracking info that it had already arrived at the local Fedex freight location. I left work early, parked my Boda Boda at my wife's work, took the Packster and headed over to get my new toy.
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It was a surprisingly quick process to remove the packing materials, stack the Largo box on the Packster box upside down, and then strap the rear of the Largo frame to that. The Stokemonkey parts and some extras were packed in in a box that fit down in the Packster box.
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I was intimidated to start rolling, but once I was going it actually rode fairly normally - top heavy, but easier than carrying an adult passenger.
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After a little trip through an industrial area, it was mostly bike paths to get home
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Finally, safe and sound in the driveway after a bit of a climb
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kevinscargobike   1 W

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Posts: 55
Joined: Nov 01 2017 6:47pm

Re: CETMA Largo Cargo Bike

Post by kevinscargobike » Jun 06 2018 11:37pm

When I test rode the bike, the handling was a little bit of a nightmare, even for a front loading cargo bike. I was ready to walk away from it, but the seller was leaving the country soon and really needed to sell it, and I wound up getting it for a price that I was confident that even after shipping, I'd be able to sell it for what I paid. It also helps that Lane, who builds CETMA cargo bikes, lives in the same city - so I have a leg up on support options.

After it had already been shipped, I was sitting around my wife's grandmother's house looking at the pictures I'd taken of the bike, and pictures of other CETMA cargo bikes on Instagram, and something jumped out at me.

Here's the front end of my new bike
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Here's what the front end of a CETMA is supposed to look like
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Somehow, the "stem" ended up below the fork on the front headset, which did some very strange things to the handling of the bike.

To start with, I just wanted to deal with getting the handling and basic fit of the bike sorted out, and then figure out the assist setup later. Here's how the bike looks now, with the front headset installed correctly, some ergon grips, and a stem that brings things down a bit lower for better handling.
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...and down in the basement, getting a thorough inspection and several kisses from my shop assistant
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kevinscargobike   1 W

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Posts: 55
Joined: Nov 01 2017 6:47pm

Re: CETMA Largo Cargo Bike

Post by kevinscargobike » Jun 07 2018 12:07am

With the front end sorted out enough to at least not be unsafe, let's get to the rear.

Initially, I really wanted to do a dual hub motor cargo bike. I like hub motors, I like that they can "just go" - but this bike has a belt drive, and belt drives are kinda awesome. I don't want to have to roll my socks, I don't want my toddler getting her hands all gross because she touched the chain.

Also, I'd been noticing that sometimes on my Boda when I go up to my house from the steepest side of the hill and I'm down to half a battery, sometimes it can only do 1200 or so watts....and it gets a little slow, and I know the hub motor doesn't appreciate that.

So, to start with at least, maybe I should make a hybrid of my original plan. A Mac 8t in the front, a Sempu torque sensing bottom bracket......and a Stokemonkey. Let's be clear about this, relative to everything I've owned or ridden, Bionx, Bosch, Shimano, Tsdz2, CA+Sempu+Phaserunner+Mac, the Stokemonkey feels like caveman assist. I'm sure it's the same thing that you have to get used to when riding a fixed gear bike, but when you expect to coast and the cranks keep going, it totally freaks you out.

On the other hand, I live on a steep hill, and I like moving things by cargo bike, and I have a 90th percentile toddler, so maybe I'll get more benefit from a Stokemonkey than a Mac on the rear. Plus, as it turns out, I just happen to own one now.

So, bearing in mind that now I'm apparently going to keep the Stokemonkey, I needed to deal with the broken spokes on the rear wheel...and if I was going to do that, I need to actually be able to remove the rear wheel and re-install it.

My wife had a Breezer with a Nuvinci N330, once, I took the rear wheel off and couldn't get it back on, and embarrassingly I had to tow the bike to a shop on the back of another bike just to have the rear wheel fully re-seated. So I decided to spend a couple of nights getting to know my new N360...and I think they did a great job of making it easier to deal with than the N330.
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To remove the wheel, you first remove the cables, and it's fairly easy to do. In a couple repetitions of removing the wheel and putting it back on, one of the cables started to come apart, and I was actually able to replace it (!), but in that process, the other cable got a bit mashed in the shifter, and I only had one spare on hand, so it'll have to wait to be replaced. I'm really happy with the Park Tool videos on youtube for this.

The other thing I discovered is that the steel frame that I was so excited could be stretched to fit a 138mm hub happens to currently be something more like 132.5mm between the dropouts. I'm not sure if it's worth cold setting yet, but when I dropped the rear wheel off to be rebuilt, I was happy to learn that the shop down the street has all of the Park tools for cold setting and dropout alignment.

I'm going on vacation for a couple of weeks, so everything will pause. When I get back, and my rear wheel is safe, I'm planning to re-install the Stokemonkey, as well as installing the battery and motor controller somewhere out of the way (under the cargo deck?), rather than in the box where they had been. I also have a Tsdz2 laying around, so I might also check and see if the alignment happens to be just right for the belt setup to work on it. It isn't what I'd want long term, but if it's a choice between just a Stokemonkey and just a Tsdz2, I think for a little while I might prefer the torque sensing and freewheeling of the Tsdz2, even if it has less power.

Somewhere along the way, I also need to find a buyer for my old Bionx assisted Yuba Mundo.

kevinscargobike   1 W

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Re: CETMA Largo Cargo Bike

Post by kevinscargobike » Jul 06 2018 4:09pm

My short update is that when I got back from vacation, I got the rebuilt Nuvinci wheel back, and put the Stokemonkey on.

The Stokemonkey is weird.

It's like you're on a tandem with a robot, and you have a lever that lets you ask the robot to pedal faster or slower, and then you have to match however you've asked the robot to pedal. I rode it enough to get used to it and give it a fair shot, but the real dealbreaker was that it was less powerful than my wife's Bosch CX. We went up the hill together a couple of times, once with me basically unloaded and her with our toddler on board, and once where we each had a full 5 gallon corny keg, and both times she totally dropped me.

So, the idea of doing a dual motor with a front hub and a Stokemonkey is out, because it just didn't have the climbing ability to be worth it's weight. I will say it was installed a little bit wrong, and that may have been a factor in how much torque it was able to produce. Still, it's not for me. Happily, Lane who builds the CETMA bikes lives in my hometown and loves the Stokemonkey and needs one, so I'm selling it to him cheap. Everybody wins!

In the interim, I was going to try a Tongsheng Tsdz2 on the bike. I was able to rotate the eccentric bottom bracket into position so that the motor could fit, but the belt line was 100% not even close to straight enough to work, so I abandoned that project.

The next mechanical stumbling block is that the awesome square taper raceface cranks that I thought I'd use are a very bizarre 94bcd, and the gates belt pulley I have is 130bcd, so I need to pick up a crankset. Since I'm still not really sure that I'm keeping the Nuvinci and belt long term, I don't want to spend a lot of money, so I'm hoping to find something either on eBay, craigslist or at the local bike coop.

So that the bike might also be able to leave the house again soon, I ordered a bare front Mac 8t from em3ev, along with a Phaserunner, CA3, Sempu and a whole pile of mounting and wiring goodies from Grin.

I'm still pretty unsure about where I'll be able to mount my Hailong-3 battery on the bike. My goal is not to have any of the essential electronics mounted on the cargo box, because I'd like it to work as a flatbed, and I'd also like to eventually have a few box options. Ideally, I'd probably get a pair of flatter batteries and mount them under the deck plate (even if I have to lift it a little to do that), but that's not an option for now. My best guess is that I may mount it on the steering mast using some combination of the built in box bracket and Grin bottle-bobs, or maybe underneath the top tube.

kevinscargobike   1 W

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Re: CETMA Largo Cargo Bike

Post by kevinscargobike » Jul 10 2018 5:44pm

I had fun last night seeing how cable wrap that sort of matches the paint would work out.
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I think it kind of looks futuristic, but a little clunky.

Our Packster uses black spiral cable wrap, and I think it's really effective for reducing the cable-clutter feel. The wrap I have isn't spiral, and the diameter is a bit to wide, I think.

Here's what it looks like on a Packster:

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Maybe I can replicate a touch of that "disappearing into the frame" effect by having narrower black spiral wrap join up with the silver.

kevinscargobike   1 W

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Re: CETMA Largo Cargo Bike

Post by kevinscargobike » Aug 21 2018 4:29pm

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I marked up this picture to ask Grin whether the Sempu needs to be oriented so that the wire goes straight down, or if I can come down at an angle, since the eccentric bottom bracket adds an extra complication. Angle is ok!
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Purple cranks!
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Battery fits upside down, using Grin Bottle-Bobs....but, I don't like it.
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Also can work on the rear rack, using Grin's eZee mounts, but...this is worse than on the frame.
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Fork filed just enough to fit the Mac motor
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This is quite an arrangement, I actually have to remove the linkage hardware to get the wheel off.
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Phaserunner installed under the platform, phase wires running along the linkage arm. Should I add more zip ties?

kevinscargobike   1 W

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Re: CETMA Largo Cargo Bike

Post by kevinscargobike » Aug 21 2018 9:32pm

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The bike finally leaves the basement. I wanted to get the entire install to be independent of whatever is mounted on the fame, but putting the battery on top of the platform really felt like the only sensible place. Because of the angled support struts in the cargo area, there's plenty of room to mount both a plastic tote and the original box on top. Eventually I'm hoping to make my own cargo deck & box, but screwing the battery mount on won't be a big deal.
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First living passenger, not pictured is a more recent trip where my wife's box bike had to be at the shop over night and so she and our toddler piled into the box together and I dropped them off at work/daycare.
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Lots of extra wire bundled up, plus a 6v converter for lights and a 5v converter for usb charging and animated LED strips. If you look real close, you can see the LED strips too.

Up next is a set of Shimano Zee hydraulic brakes with big ol' rotors, a Satori easy-up for easy height adjust on the handlebars, and maybe a 12v converter to run a motorcycle bluetooth speaker system that I can hard mount somewhere to just have on the bike all the time. Also new fenders - the rear doesn't really cover the wheel, and the front didn't fit at all with the new 2.4" tire.

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