Custom Build Gallery, Paul Brodies 2013 NAHBS eBee

March 6, 2013
Submitted by renowned mountain bike frame builder Paul Brodie. This is one of the most beautiful custom builds we have seen.
 It started last March as NAHBS 2012 (North American Handmade Bike Show) in Colorado was winding down. I wandered over to see Sam Whittingham in his Naked booth, and we chatted about the show. After a while we got onto the subject of what we might do for this year’s 2013 show, and I volunteered that I was considering an electric bicycle. Sam said, “You know what? If you do an electric bicycle, half the people here will love it, and half the people will hate it, so DO IT!”  His comment really helped me commit to this project.
My very next Framebuilding 101 course had 4 students, and 3 of them owned electric bicycles. Of those 3, one student, Justin Lemire-Elmore, owns Grin Technologies (, a business that specializes in supplying motors and parts to convert standard bicycles into electric bicycles. I was very surprised to find out that he has eleven employees! I still had not ridden an electric bicycle, but that would change very soon.
Another student, Mike Clegg, came to my shop with two electric bikes in the back of his SUV. They were cruisers, and had the BionX electric assist. This means that if you didn’t pedal, you didn’t go…I liked that. I pedalled down the street, and it felt like a big helping hand was pushing me along. I came back with a big grin on my face. Another friend was over, so I told him to go up and down the street. He said no. I insisted, and he too came back with a big grin on his face.
My time was all filled up for most of the year, but I could start working on the electric bike full time on November 15. In September I started sketching out a few ideas. I had no idea what this bike would finally look like. At first I wanted to hide everything Electric away under a carbon fibre clamshell. That was my plan. I wanted to build it on a modular platform, to allow for future design changes, if necessary. There would be a tubular trellis frame, and the motor, controller, batteries, and swing arm would all bolt to this:

I did another, more refined drawing, and now the Electric components were all suspended below the frame. The idea was to get the motor down low between the crankset… to build the equivalent of a motorcycle road racer for the street. I was sold on “Mid-Drive”; where the motor is between the wheels. This way, the motor drives the BB, and you can use the bicycle gears as a transmission to get more efficiency out of the motor.
Most electric bicycles use a motor in the rear hub. It’s the cheapest way to build an electric bicycle. However, no matter how many gears the rider has, the motor is still only one speed. Your top speed is limited, and you can only climb a certain grade before the motor starts to overheat.
I wanted to be able to do 30-MPH on the flats, and be able to climb any hill. I wanted suspension, big fat street tires, and good brakes. I knew it would have a motorcycle influence, and it might blur the lines between bicycle and motorcycle. I did some research on the Net, and found videos of some very fast electric bicycles. They’re running at 72 volts, a couple at 110 volts! Top speed is 60-MPH. More voltage means more power. A lot of the technology comes directly from the R/C world, which has made huge strides in the past decade. There is now a 5-HP motor that fits into the palm of your hand…Bikes like this can wheelie up and down the street, and the rider never needs to pedal. That was not what I wanted.


 I went to see Justin at Grin Technologies, and he set me up with one of their new red Stokemonkey motors. (pictured below) These are known for their torque, making the power delivery very linear. The motor shaft is fixed, and the motor body turns at 350-RPM maximum. That would require a jackshaft with a 3.5:1 reduction ratio. Designing and building this bike was like assembling a giant puzzle; a lot like designing a very small motorcycle with 3 chain lines. Trying to get all the components to fit into a compact package that operates efficiently and looks good at the same time was a real brain teaser. This is my workbench as I am figuring out the side plates  for the first time:


eBee’s name came out of the blue. I wasn’t trying to find a name; eBee was just into my consciousness, suddenly, one afternoon, so I wrote it down. eBee is short for Electric Bicycle.
Below is the frame jig used to build eBee’s frame. Pretty straight forward. Head angle is 69 degrees:



I made a fixture that held both top tubes at once for the mitering process, shown here in the shop milling machine:



Because the motor exerts a lot of torque, the shafts have to be held very firmly, and aluminum just isn’t strong enough. Here, I’ve milled out the aluminum mount to hold a 304 stainless steel insert, to be held in with a couple 5mm countersunk allen screws. The slot is made using a boring head, and moving the mill table sideways. Depth of each cut is .025″




The axle holder is flipped over in the mill vise, and bored out to fit the BMX freewheel. Ultimately, it got redesigned and thrown in the scrap bin:



I had planned to hide everything Electric away under a large carbon fiber clamshell, but the motor shaft was wider than I expected, so the New Plan was to get the motor shaft outside of the crank arm circle. Which meant, upwards and forward. Instead of hiding everything Electric, I would now showcase the motor and everything else. I’ve always felt that each part should be able to stand on it’s own in terms of function and artistic design. I had an idea, but no actual drawing as I started making parts out of metal:



I used a 44mm head tube from Paragon Machine, and the tubing is 3/4″ 4130 with an .049″ wall thickness. The smaller cross braces are 5/8″ True Temper 4130 with an .035″ wall thickness. Tube bending from Andrew at Pacific Bending in Maple Ridge (Thank you!). Tig welding was used to join all the tubes together:



These are the rusty plates of steel I am using for the rear dropouts. I have made a sketch and have a few measurements, and that is good enough. I thought the plates were mild steel, but as I started machining, I realized I had picked up some tough steel that had a very good carbon content. These will help to hold the Rohloff rear hub securely, giving eBee a 14-speed transmission:



There’s my cardboard template, and you can see the basic slot outline has been done in the milling machine, using a sharp end mill:



I hadn’t been happy with the angular shapes of the 2 side plates, and one afternoon I had the idea to really enlarge the radiuses around the bolt holes, and then scoop out the material between those arcs. That looked much better. Here, the left side plate is mounted on the rotary table and a cut made to give chain clearance. I do not have a CNC mill. Figuring out 3 chain lines made me scratch my head quite a bit:



In total I made 5 sets of side plates before I “got it right”. Could I have figured this all out on a 3D drawing program like Solidworks? I don’t know. I think I need to have the metal in my hands, life size: 



I made a new rear dropout to replace the original Rohloff item. Because the rear frame is so low, the brake caliper mount can be canted forward much more. Material is 7075 aluminum: 


electric bike drop outs

Setting up the chain stay jig to build the rear end. The Hope brakes and front hub have arrived. Nice stuff! 


electric bike jig
The chain stays have been Tig-tacked, and now the seat stay jig and a big C-clamp hold it all in place:


The seat stays are now on, and it’s time to see eBee’s shape evolving and coming together. Yes, that is Bill and Hillary on my wall, in happier times:



Detail of the fillet brazed dropout holders, Hope rear brake, and Rohloff hub. According to Justin, the only two hubs that will stand up to continuous electric motor power are the Rohloff and Nuvinci hubs:



On the spot wiring diagram, courtesy of Justin:



This is the complete package for eBee, minus the motor: (left to right) the 25 amp controller, Cycle Analyst computer, Thun BB, and the lithium polymer batteries. The small but powerful batteries are normally for R/C hobby airplanes. They are connected in series to produce 52 volts, giving the Stokemonkey motor an output of just over 700 watts, which translates to about one HP.

The Cycle Analyst display is from Grin Technologies, and is the latest 3rd generation model. You can program when the motor starts to assist the rider, and by how much. It tracks battery life, and will automatically partially shut down when the batteries get too low. It can tell you how much energy you put into the ride, and how much the motor put in…The Thun BB has integrated magnetic sensors that detect the mechanical strain on the BB spindle, and sends that signal plus the cadence signal to the Cycle Analyst, which tells the controller how much juice to send to the motor. A very slick system!



Other parts. This is a mount for hanging the batteries and controller from the (2) side plates:



Now in the mill vise, having the centre section lightened with a 1/4″ end mill:



Finished, except for anodizing:



I needed sprockets for the jackshaft, so I went to my local bearing supply house and purchased these two beauties, plus (2) bearings:



Sometime later, they were thinned, lightened, drilled, bead blasted, nickel plated, and ready for assembly:



I needed to make sprockets for the $35 crankset I got off Ebay, so I found an 1/8″plate of 7075 aluminum. Here it is setup on the rotary table, and 52 teeth means one cut with a 5/16″ end mill every 6.923 degrees. A little bit of concentration was required:



The boring head spins with a carbide insert tool and makes very smooth holes. The sprocket fits an 1/8″ X 1/2″ pitch chain:



eBee is starting to come alive!  There is still LOTS to do:


I needed to build a new stem cap to hold the Cycle Analyst computer and the fairing. I took two pieces of aluminum, held them together in the mill vise, and bored a 31.8mm hole. When I opened the vise, I had 2 pieces that looked like this:


In the front is the original cap, and above is the new one, about half done. Quite a lot of metal got removed:



Finished, and waiting for a coat of red paint:



I needed a head tube badge, so why not start with a solid chunk of aluminum?



The 6061 aluminum is bored to the same size as the head tube OD. The decal was photocopied and enlarged to 160%, then traced onto the tube:


Quite a bit was done in the mill vise with a 1/4″ end mill, followed by some hand filing and sanding. It would get anodized pewter: 


A lot of aluminum scraps got converted into eBee parts. A total of (46) machined parts were sent out for anodizing. This chunk of aluminum got used for the Cycle Analyst / fairing mount:



Here, the mount is slowly taking shape in the mill vise:



The finished part:



These are the holders for the (2) Rohloff cables, under the left seat stay. The radius on each end was done on the rotary table: 



Figuring out the shape for the fairing. The shape is developed using aluminum welding rods and a glue gun:



View from behind.



The welding wires were covered with masking tape, and fiberglas matt covered that, followed by bondo. This was sanded smooth to the desired shape, then primed, sanded, painted, polished, and finally waxed 5 times. This is the “plug”:



Here, gelcoat has been sprayed over the male plug. This is the start of the female “mold”. Over this many layers of fiberglas matt will be laid… this forms a very strong mold: 



This turned into a disaster when the plug refused to separate from the mold. It had to be chipped out, and the bondo softened up with successive coats of paint stripper. It was winter here, so a lot of the painting, stripping, bondoing, fiberglassing, etc. happened inside. I’m sure my shop was not the healthiest place to be. When the plug was finally out, I had a damaged mold, so that had to be repaired before I could lay up the little fairing: 



When eBee was mocked up, I took circles of masking tape, and placed them on the side plates to see where holes might look good. The side plate was then clamped on the mill table, and the centre of each circle was marked with a +. After the centre of each hole was located with the mill spindle, I used the digital readout to save time when going from hole to hole. The numbers in red felt pen are the X/Y co-ordinates: 



This is the final version of both side plates, ready to be sent out for anodizing. The colour will be pewter: 


Everybody has a Chris King headset, it seems. I like Chris King; I think he’s a great guy. However, I had some aluminum, and believe it or not, some spare time,  so I decided to make my own. It will be anodized black:
One of the last processes was to create the battery box covers, which are suspended under the electric motor. Working with fiberglas / carbon fibre involves making a plug, a mold, and finally, the part. The two parts have to mate, and have a certain depth, so I cut 2 pieces of aluminum to match. Then an aluminum standoff was machined and located:


Using bondo, some 2X3’s and plywood were glued on, and the rough form is starting to taking shape:



More bondo as the final shape emerges:



This is the desired shape, so now time for hi-fill primer, and the top coat:



Painted and waxed several times… shiny!  That’s me taking the photo. These are the plugs. Now it’s time to make the actual molds: 



The plugs get sprayed with gel coat, left overnight, then coated with many layers of fiberglas matt to create a strong mold: 



The molds have been separated from the plugs, trimmed, and mounted to plywood. Coats of wax to follow, then PVA mold release:



This is the carbon fibre cloth: it’s a very flexible weave, and quite delicate. From all the work in the shop, my hands aren’t exactly smooth, and little rough spots on my fingers would catch the cloth and separate the weave. I’ll bet the majority of people laying up carbon fiber in China are women…



The cloth has been cut and placed in the bottom of the  mold, and now additional strips of carbon fiber will be added up the sides. I think the bends are too sharp to only use one piece of cloth:



This is not true carbon fiber work, as I am adding layers of fiberglas matt over top. I do not have pre-preg carbon, and an autoclave and vacuum pump in which to cure it. My parts will be heavier, but I will have that carbon “look”: 



These are the finished battery covers. They are not perfectly smooth. They could be sanded and clear coated numerous times, but there are only a few days left before the show, and my list still has many items left: 



Pinstriping by Paul. UFV sent me on a pinstriping course about a year ago, and I learned a few skills there. I don’t have the patience for the “classical” pinstriping where everything is symmetrical. I like quick, flowing, and random. Classical pinstripers would probably be horrified, but it works for me:



This little handlebar fairing to house the Cycle Analyst is fresh out of the mold, and needs to be trimmed and mounted:



It is now Tuesday evening before NAHBS. Justin (Grin Technologies) is helping with the final settings and wiring tweaks before eBee’s First Ride. We also got the speedometer hooked up, which is important, he told me. Our schedules are completely opposite. I have been getting up at 5:40am to teach Framebuilding 101, and Justin regularly stays up to 4am. It is almost midnight, and I have had some gin, so maybe that is why the photo is a bit fuzzy. The night is cold and clear, and Justin is first to ride eBee soon after this shot was taken: 



The Cycle Analyst is completely programmable, and also tells a story. Justin returned from his short ride, and eBee had gone 48.7 kmh, which is basically 30-MPH. Average speed was 30.2 km/h, including the turnaround at the end of the block. It is now my turn. I am exhausted, it is after midnight, I have my work boots on, and my blood sugar is low (I am a diabetic…) I ride anyway. eBee definitely needs some more setting up. The tires are too soft, forks need a lot of adjustments, and the Rolhoff that shifted well on the stand, doesn’t want to now. Probably the cables have stretched.

It is pitch black except for the very bright LED headlight that is plugged directly into 52 volts. I cannot even see which of the 14 gears I am in. I pedalled about 3 crank revolutions and then the motor kicked in, and eBee accelerated! She definitely has a bit of go. How soon the motor kicks in, and how hard, is all programmable. During the evening, I managed to talk Justin into coming down to NAHBS, and he booked a flight. He’ll be there Saturday and Sunday. He’s definitely the man to talk to about this very slick electrical system:



It is now Wednesday AM, and another night with 5 hours of sleep has come and gone. I have to mount the battery boxes, do the final photo shoot of eBee, buy some clothes for NAHBS, and pack the bike and stand into a box. We leave tomorrow at 5:30am.

eBee was created in 90 days from start to finish. Unlike the 1888 Whippet, where I didn’t keep track of my actual hours, I can tell you that eBee consumed 485 hours of my life. I learned a lot, and have no regrets!  Thank you all for reading my story.
Paul Brodie
Written by Eric, March 2013


Eric has been involved in the electric bike industry since 2002 when he started a 6000 square foot brick and mortar Electric Bike store in downtown San Francisco. He is a true believer that small electric vehicles can change the way we operate and the way we think.


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