That said, finding a cyclonic separator is not so easy, and building one would be challenging also (stainless steel conical fermentation vessels for brewing could possibly work, but the shape of the cone cannot be customized). A close approximation would be a shop vac.

So the hunt was on for a suitable shop vac.

I went to Home Depot and Lowes and purchased four shop vacs, ranging in size from 2/3HP to 3.5HP and attached them to the CocoaMojo Mark I. Lowes had much better prices for equivalent rated vacs, so the only shop vac I purchased at Home Depot was the one which mounts on a 5 gallon bucket.

The results: even the “3.5HP” vac could not suck with enough force to winnow large cocoa bean chunks using the Mark I’s 4 inch pipe. I put quotes around 3.5HP because my old Craftsman 3.5HP had sufficient power… but the Lowes brand vac did not provide equivalent performance. I wasn’t willing to sacrifice the Craftsman for CocoaMojo so I needed another solution. I figured the suction power was based on the cross sectional area of the pipe. So I switched to 3 inch PVC. This has about 3/5 of the cross sectional area of 4 inch pipe.

Testing different lengths of pipe

Surprisingly, the Lowes 2.5HP vac was conveniently smaller and performed as well as the Lowes 3.5HP shop vac, so I used the smaller of the two. The Home Depot vacs were just too expensive for their performance and the bucket head vac was terribly under powered.

The results were very encouraging.  It would surely take some tuning, but I was not finding much nib in the shop vac and most of the shells were sucked away from the nib.  I told Mike about progress and we decided to try running a batch of cocoa beans through the whole process.  I modified the existing frame to accept the 3″ pipe and got ready to grind some beans…

Briefly, cocoa beans grow in pods near the equator. The pods are harvested by farmers and the outer husk removed, leaving a pile of beans. The beans are piled up and covered to ferment, which oxidizes many of the bitter tannins and, due to the heat inside the piles, also prevents the beans from germinating (not unlike how grains are prepared for beer production). The beans are then dried in the sun to prevent them from spoiling due to moisture.

The beans have a hard center (nib) and a somewhat soft shell on the outside. The beans are oven roasted to bring out additional flavor and to dry the shell. The roasted bean is easy to crack in a grinder. The result is a pile of nib chunks and shell chunks that must be sorted.

Sorting manually is extremely time consuming, so for anything more than small quantities of chocolate production, an automated solution is needed.

A quick Google search turned up several winnower designs. My favorite thread was on The Chocolate Life about using some PVC tubing and a blower motor. The idea is to dump the output from the grinder down a tube which has a blower motor at the bottom. The lighter chaff escapes out of the tube while the heavier nibs continue and fall to the bottom. That’s the idea, anyway.

Mike provided an industrial sized “can fan” he had purchased.  I went to Home Depot and got 4 inch PVC tubing and some T joints. I built a reducer from the can fan’s 6 inch output to 4 inch PVC (mostly from duct table), a butterfly valve to vary the fan power, and a gate valve for the bean input.

You can see the results documented in video here.

The winnower definitely worked but it took several passes to sort the beans. Also, the machine was very messy and tended to blow beans out of the input hole– leaving the gate valve closed and throwing a handful of beans in, then shutting the gate again was the best way to use it. The creator of the winnower on The Chocolate Life forum had pictures of himself using it outdoors, but this seemed rather impractical for Mike’s apartment in San Francisco.

No, a second prototype would be needed…

Yours truly with the Mark I Winnower

I say all you need is a heat gun and some patience.  The oven and mold are good, only because they don’t get impatient.

I stuck an acrylic rod into the head of an EMT bender and put it in the oven at 200F for 15 minutes.  I forget the actual temperature that acrylic melts, but I doubt it mattered as the oven’s birthdate roughly coincides with the Apollo moon landings and so the temperature knob has fallen out of calibration.

Bent acrylic sanded on one side

I tried again with the range instead of the oven.  After about 30 seconds, I got impatient and cranked the heat all the way up.  Another half minute later the acrylic blistered and started to bend in my hands.  The result was pretty ugly, though functional.

So, somewhere in there is a happy medium.  I suspect around 10 minutes would do the trick.  If you can’t stand around for 10 minutes with a heat gun or oven range, then make a mold or jig.

A bike that is a poor bike without electrics added will become an even poorer bike with all the weight and power of electrification. Start with a good bike.

I had to fix some derailleur adjustment issues but the chain still slips. I will replace the chain (note: the Walmart chain I used appears to be at fault, it slips right out of the box!). The tiller steering is very annoying, and the pedals aren’t forward enough for me (the bike was built for shorter legs). Also, the seat back is not quite cushioned enough to be riding for long periods.

First Lithium Powered Commute from Peter’s Bikes on Vimeo.

November 10th, 2008

I now intend to improve this bike. The tiller steering needs to go and the front fork with it. It is too thin and the brake mounts can’t be used with the motor on at the same time, since the chain occupies the same space as one of the brakes. Devising a new motor mounting could take some effort… Alternatively, I could use a switch, some relays (to disconnect the motor from the batteries and motor controller), and a coil of stainless steel wire to use the motor for braking. If you connect the power wires of the motor together, it will brake. Adding resistors between the power wires will vary the braking force; it’s tough to find big enough resistors, but you can use a coil of wire wrapped around a plastic pipe too– just vary the length of the wire.

I added two Sterilite trash cans under the driver’s seat for cargo carrying. I placed them low enough to avoid interfering with the handlebars. Where to put the batteries now? They will likely hang behind the trash cans, but for now they are IN the trash cans.

Speaking of batteries, charging 12 batteries one by one is no fun. Each battery takes about 20 minutes tops– depending on how far it was discharged– but that’s still 12 batteries that need to be baby sat. I inquired on the Endless-Sphere forum about whether the Makita fast charger allowed charging of multiple packs in parallel and it does work. Fellow e-biker Jonathan D. hooked me up with 2 Makita LXT shells– battery packs with no batteries inside. I opened one up and soldered a wire to the + terminal and another to the – terminal and routed them out of the shell through a couple of holes near the front of the shell. I attached an anderson connector. I then tortured myself trying to work with the security screws that hold the shell together before I just dremeled their heads to turn them into slot head screws.

I then rewired the 2 packs I built to be 18v each– all batteries are in parallel. Now I can put the shell on the charger and attach it to one pack and it will charge the whole pack– theoretically. It should take 4 x 20 minutes for each pack, but at least I don’t have to baby sit it. Turns out, however, that the 7 little pins in a yellow connector on the battery report some sort of status information to the charger and the charge always fails after two minutes with the shell. DoctorBass on endless-sphere suggesting opening one of the working Makita’s and soldering the anderson connectors to it’s terminals.

Finally I fixed the kick stand; leaning the bike against stuff was getting really obnoxious as its now about 40-50lbs fully loaded and would probably get damaged in a fall.

Testing

Former partner in crime Eron V.’s holiday party provided another opportunity to test the bike. We took turns giving party goers rides and then turned the bike over to the more adventurous. So far about 12 people of varying stature and weight have ridden the bike, mostly in the tandem configuration, and I haven’t found any problems except that the seat post keeps coming lose and twisting in the socket. High speed ride and stability is actually better with two riders, but a very low speed oscillation in the steering gets worse with two people. If you ignore it, the bike moves in a straight line, but at about 2-3 mph there is a feeling that the bike wants to turn back and forth and it’s unnerving.

The greatest load carried so far has been 380 lbs with a 240lb rider in the back.

I rode from home to work twice, once alone and once with my significant other on the back.

Average cruising speed (alone): 17.5mph. The bike seems to hit some controller limit at 18.5 on the flat
Average cruising speed (two riders): 16.5-17.0mph (depending on rider). Max speed drops also by 0.5-1.0 mph.
The motor got much hotter with two riders.

Ride time (alone): 38 minutes
Ride time (two riders): 40 minutes

Battery state was

One rider: v₀=39.3V, v_f=35.3V
Two riders: v₀=39.3V, v_f=34.5V

Low voltage cut off is set below a safe level right now, but 28V would be a sensible limit. Voltage sag on full throttle acceleration is about 1.0-1.5v.

Odometer currently reads 43.8 miles.

Next upgrade is a head light! Very hard to ride through the marshes with no light.

Best upgrade so far: I fixed up the driver’s seat. I used two L shaped pieces of pipe, attached the back rest at lumbar height with a 1/4″ bolt and large washers, then attached a padded seat to the bottom by using a piece of pallette wood. The real bastard was attaching the seat to the frame. This I accomplished by welding two tabs onto the frame that fit between the two L shaped pipes that are the frame for the seat. I welded 3 small pieces of 1/4″ steel plate together and drilled a 3/8″ hole through them to make the tabs. I then drilled 3/8″ holes in the two L shaped pieces of pipe and stuck bolts through. 1/4″ is not enough! I tried and the bolts simply bent and had to be removed with the Dremel.

I placed a large exercise machine seat for the rear passenger. To give them something to hang on to, I welded some kids bike handlebars (the type with a big U shape to them) onto a seat clamp, which I then clamped onto the original seatpost.

I added under seat steering. Tom Kabat of Woodenbikes.com had this on some of his bikes and it is super comfy. I cut some kids handlebars in half and welded a 90 degree angle in between. Tom bent some pipe into a large U shape, which would be preferable, except that I can’t bend pipes (yet). I think a V shape would be ideal. Basically, with a SWB layout, the steering tube is just a little bit forward of where it would ideally be. You can put above seat steering but it has to be high up to not interfere with your legs (if you use standard handlebars). With under seat steering, the handlebars have to come back far enough to reach your hands and have to avoid interfering with your legs when you are stopped but at the same time the closer in to the frame you bring the bars, the less you can turn the front wheel at low speed (because your hands hit against the frame).

Unfortunately the Kollmorgen’s hall sensor board did not like me resoldering the wires (which were flimsy after all the work done around the motor)! Two of the traces flaked off. I had to Dremel around the board to remove it and try some surgery. So far, the fix is not working, but I’ll give it one more shot before swapping motors. Never again will I buy these sensored BLDC motors/controllers! So much trouble for too little gain.

Measure Once, Cut Twice, Throw Hands up in Frustration

Now that I have switched to lithium and the circuit work is still not completed, I have not ridden this bike much. I decided to convert it to a tandem and switch it to more conventional propulsion. I welded the old boom on to the back and then welded on two seat tubes– one in the usual configuration (almost vertical) and one at an angle, so I could attach a back rest to a seat post and place it in the angled tube.

I then spent a very long time trying to salvage a bottom bracket shell for the rear set of pedals (this is the tube that the pedals spin in). I could not use the original shell because with 20″ wheels the pedals would hit the ground. Removing the original shell would have created structural problems. So I needed to locate one higher. I would highly recommend purchasing bottom bracket shells from a place like UBI or NovaCycles, as salvaging an intact shell from rusty old bikes is not worth the $5 cost for a steel shell. I spent three evenings and three frames before I got one working shell. And that took a torch, a 4 foot breaker bar, a grinder, two dremel cut off wheels, and lots of elbow grease.

The previous seat was uncomfortable and deteriorating, so I built another one out of an office chair.

Unfortunately my other half was not around to provide measurements and I welded the shell on too far forwards. Oops. The seat also interfered with the rear riders pedaling. Oh, and I couldn’t get the chain routing worked out. I have now decided to return the bike to its original configuration except with the possibility of giving a lift to a rider on the back. I will weld foot pegs onto the rear so the passenger’s legs don’t just dangle in mid air.