Matt is well-known in custom electric bike hot-rodding circles. This is the fifth time we have written about something he has built, and that is a new record. This time? He mounted one of his twin motor DaVinci drives to a Qulbix Raptor.
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Choosing the Qulbix Raptor
We wrote about the Qulbix Raptor back in the spring of 2014 when we saw a lot of garage builders using this frame-kit. All of the major parts are steel, and although you might think that this makes it heavy, it also means that it is easy to cut and weld onto (as you will see below), and that’s good if you are the type of person who likes to customize your off-road ebike.
With the rise in the use of high power-density 18650 cells in 2015, the HUGE battery box of the original Raptor 140 (the “140” means the main part of the frame is 140mm wide , or 5.5 inches…roughly the length of a dollar bill) was heavier than needed for many Raptor enthusiasts, so…Qulbix came out with a narrower and lighter Raptor Q76R. The narrow 76mm wide battery box could hold 18650 cells on their 65mm-long side, and if you filled up the battery box with cells, it could still hold quite a few Watt-Hours (WH) of cells.
Be that as it may, Matt is very experienced, and when he gets started riding, he likes to ride for hours! So…he decided to build up one of the original Raptor-140 frames, so he could fit the maximum battery capacity possible.
The initial lay-out for the frame and drive-mount
Most Raptors are built up as a simple rear hub system. Matt wanted a mid-mounted motor to keep the rear wheel as light and nimble as possible. Moving the weight of the drive system to the frame also improves the ebikes balance and feel. Most mid drives take advantage of the bicycle gears to give the motor several gearing options. This build, however…was going to have enough power that it would break bicycle components, so…it would need to be a one-speed that is connected directly to the rear wheel.
Matt Is the owner of DaVinci Drives. He has gotten so busy that he occasionally farms out some of the machining, but he started this business from scratch, and accomplished all the design work and machining by himself. His main focus is producing drive systems from the Astro Flight line of RC motors. These high quality units are made in the USA, and to get their full power, they must be spun-up to ultra-high RPMs. Then, in order to get the power down to wheel-speed, a significant reduction must be designed and added.
The primary reduction between the motor and the rest of the drive system is often a belt, which can run quieter than a chain (at high RPMs). The pic below is one of Matt’s most popular units, a single 3210 motor, with a robust White Industries flanged freewheel that is integrated into an aluminum pulley.
An Astro Flight 3210 with a belted primary reduction
Although this prototype was going to be geared for off-road, the size and weight of the significant battery meant that…in order to get the level of performance he wanted, he would have to spec one of his exotic twin-motor drives.
The first order of business was to create a space at the lower corner of the frame for a complex idler and chain-guide system, since the power will be flowing to a rear suspension that cycles up and down. This is the main reason most Raptors use a simple rear hub, but…Matt is not the type to shy away from a complicated challenge.
An air-driven die grinder with a thin abrasive cutting disc is just the tool for making sparks…Use eye protection. I have a lot of scars, but I don’t screw around with my eyes.
With the bottom corner cleared away, Matt will cut and weld-in some flat sheet to create a foundation for the chain and sprocket magic.
Here is the robust sub-plate that Matt designed and fabricated in his shop.
The custom chain-guides and their support framework.
The outer frame of the chain-guide above is 3mm thick carbon-fiber, just like the side panel of the battery box, below.
Carbon-fiber for the chain-guide outer plate, and also the battery box side-panel.
Matt has been working with carbon fiber for a long time, and this allows him to do custom work in his own shop, without having to wait for another shop to get to his order, and then ship it.
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Battery Pack
I’ll be honest, I’m not a fan of LiPo for anyone who is new to ebikes. LiPo (Lithium Polymer) requires a more complex charging system, and it also requires thoughtful care to remain safe. That being said, Matt is very experienced with these systems, and on this build…he wanted to pack every possible bit of airspace with battery.
MultiStar 4S bricks. Each rectangular foil cell has 16-Ah, and each green brick shown has four of those…
The C-rate (C is for Current) of Multistar LiPo pack is “good”, but…over-rated by the factory. Each cell is a whopping 16-AH, so some early adopters assumed they could run an ebike with a 1P string of them. These were designed for RC aircraft, and ebikes are much heavier, so…any acceleration phase that is longer than a second or two caused the voltage to sag a little, leading some builders to call them “Multi Sags”. They don’t sag for Matt, and here’s why.
Having a non hub motor (as opposed to the common large rear hubmotor), means that you can design the motor to spin at very high RPMs, where the motor is happy and efficient. Remember, at 28-MPH (45-km/h, the California ebike speed limit), a common 26-inch wheel is only spinning at 362 RPMs…Matts motors are spinning at around 10,000!
Fitting Multistar LiPo into a Qulbix Raptor frame
Of course, the obvious second reason is that…Matt is using five parallel strings of the 16-Ah packs for extreme range, with the side effect that they will stay cool at his amp-draws, and also…there is more than enough Watt-Hours to make sure that the performance never sags. 5P X 16-Ah is 80-Ah (not a typo).
If you look back at the pic above, Matt has 15 of these that will fit, so we divide by 5P and the series-count is three X 4S, meaning this is a 12S system. At a nominal average of 3.7V per cell, that’s (3.7V X 20S =) 44V. Of course, when fully-charged, This ebike will spend a few moments at (4.2V X 12S =) 50V, at the start of a run.
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Swingarm Modifications
Matt learned early on that wheelies are fun…for a while. However…once you get that out of your system, you want to wheelie less and accelerate more. One of the ways to help with that is to make the swingarm just a little longer. If you are going to cut and weld a swingarm, the first order of business is to brace the pieces so they are held in perfect alignment during the entire process, as shown in the pic below.
Bracing the swingarm before making the cut.
I cringe every time I see anyone else about to cut up a perfectly good frame, but…when Matt does it? I can’t wait to see what he is going to create.
Matt made sure the finished splice was stronger than the original.
The extension may only be a couple of inches, but that’s what Matt calculated would be the ideal amount to accomplish his goals.
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Powder-Coating and Reassembly
Once the cutting and welding were done, the next step is to send them off for cleaning and powder-coating. It is easy and cheap to get a frame this size painted, but powder-coating provides a much tougher and more scratch-resistant finish. For this project, Matt chose a bold canary yellow, with black accents.
The parts are finally starting to look like something.
Getting the parts back from the shop to start the reassembly phase is an exciting time. This is when you get to see if all of your planning and hard work will turn out the way you envisioned.
Once the wheels are added, it’s easier to move it around the shop. Check out the massive 200mm front discs.
Popping-on the wheels during reassembly immediately gives you a feel for how the overall look will present itself, and it also makes it easier to move the prototype around.
The dual motors apply power onto a belted reduction on the right side of a jackshaft, and then the chains are routed to the rear wheel on the left.
There’s something very satisfying about assembling high-end parts onto a complex mechanism, like watching a German clock being assembled.
The rear disc and drive sprocket are both on the left side.
Matt wanted the drive system to power a single-speed chain to the left side of the rear wheel. After much consideration, he designed and made a custom “top hat” adapter to hold both the sprocket and the disc brake. I immediately asked about chain-lube getting onto the brake disc, but Matt assured me that after properly cleaning and lubing the chain, he never lubes to the point of it being able to drip. Then…when you make the first spin-up after a chain maintenance session, any remnants that might come off the chain are flung outwards. Matt has ridden this ebike hard, and lube on the disc has not been an issue.
Assembling the motors and primary drive.
Astro motors and controllers are every small and light. Since the motor spin at very high RPM’s their sound is more high-pitched than the electric motors you might be used to. I’m not going to claim that they are quiet, but many enthusiasts actually like the sound, in the same way that a Ferrari V12 has a music all its own.
This build is using two 3220 motors with a fast 3T winding that is terminated in WYE. Matt started out with the ebike geared for a 40-MPH top speed, but it was drawing too many amps from the controllers, which were hitting the high temp alarm too often. Once he reduced the gearing to to a 32-MPH top speed, everything was performing great.
The two tiny controllers are Castle Creations “Edge” HV-160’s. Although they are rated for 160A peaks, Matt has found they can reliably hit 200A each (44V X 400A is about 18,000W)…as long as you don’t get them too hot. Of course, his continuous amp-draws are MUCH lower when he is just cruising along through the snow.
The carbon-fiber splash-guard.
This bike was not designed and made to be a “trailer princess”, to just be polished and transported to hot-rod shows as a vendors advertisement. Matt lives in Ohio, near some beautiful trails, and this ebike was going to be hitting those trails, so…he knew from past experience that he should add a mud-guard over the mid-mounted drive system. This is another application where his carbon-fiber skills came into play.
Eating snow and spitting out fun.
Once a project is completed, you just have to get outdoors and have a run. The date on this pic says “May of 2003”, but its from just a couple months ago, in the winter of 2016. Matt laughed and said he is too lazy to set the correct date when he changes the batteries. I know a lot of words to describe Matt, but “lazy” is not one of them.
Two bright and efficient LED headlights, for those times when you are having so much fun, you don’t make it back home before the sun goes down.
Once you start running on an off-road ebike that has a massive battery, you keep running until the sun goes down! So…Matt added two very bright LED headlights.
If you want to read the original build discussion, you can find that here.
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Other Astro builds
The lightweight full suspension
The Dual Astro “Dogati” built by Ben Chiu
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Written by Ron/spinningmagnets, January 2016
