Hey Guys,
Just out of curiosity, I was wondering what your ideal hard edge full suspension bike consist of? (I am talking a high-end bike with a price tag around what a Stealth costs.) This would be a downhill style bike.
I do not want to hear "20,000 watts, 200 mile range, and $1,000 price". I want realistic suggestions. :wink:
First of all, for the sake of argument, I assume it would be a monocoque/box frame. But, would your ideal frame be aluminum or steel? Chromoly maybe?
I really like the idea of a monocoque/box frame, with a mid-drive in the bottom bracket. In particular, I like the idea of (and have been looking at designing) a monocoque frame with a removable bottom bracket drive unit; that system would have the upper portion of the frame reserved for the controller and the batteries, while the drive unit would contain a motor with a single or double reduction (as appropriate), as well as (if possible) an 8-speed IGH interfaced with the BB to allow multiple speeds with pedal power. From there, it should be possible to use a single shaft to transmit the combined torque from motor and rider to the rear wheel. I'm currently teaching myself Autodesk Inventor 3D, with the drive unit as my learning project; the idea would be to use a 15mm HTD belt for the primary reduction and then either #25H or #219 kart chain for the secondary (that's being designed to mate to a C80100; the RV120 would only need a single primary reduction because of its low KV).
If I were building it myself I'd build the frame box and power unit out of 1-1.5mm 4130 Chromoly sheet steel, with thicker plates made out of 6061 or 7075 aluminum and bolted to the shell (primarily because I can TIG weld steel reasonably cleanly, but can only kind of lay beads on aluminum); if I had infinite money and either a really talented welder or a high-quality CNC welding machine I'd get it done out of 7068 aluminum (roughly the same density as 7075, but 15-20% stronger) because it's incredibly light and strong. Swingarms would probably be waterjetted 7075 aluminum around 1/4" to 1/2" thick; that way it'd be reasonably possible to minimize weight, and the lack of a massive hub motor in the rear means that you no longer need absolutely massive dropouts to keep the hub from spinning out.
How about forks?
I'd ideally go with the Boxxer race upfront; they're designed to take a decent volume of bumps and bangs at 40-50mph, which means that 40-70mph onroad speeds should be reasonably safe, and Boxxers should allow for a decent amount of abuse (stairs riding, singletrack with decent jumps, etc.) even at a 100-150lb overall bike weight. It's a fairly useful all-around on- and offroad fork and it'll run you around $700-750 (which means it won't necessarily break your budget, especially if you do production runs instead of sourcing the forks one at a time off Amazon).
Suspension travel?
8 inches up front and 7-10 in back would be ideal; that should be more than enough to smooth out the road bumps and should be enough to allow for use on most dirtbike tracks and DH slopes.
Wattage? (let's be realistic)
Ideally 10-15kW peak, and 6-8kW continuous; in particular I've been looking at designing the drivetrain I described above around the Turnigy C80100 and/or the Revolt RV120. Ideally, I'd be running them at 24-28s (88.8-103.6V) through an 18-FET IRFP4568-equipped Lebowski controller; the idea would be to run the system at 150 battery amps peak and 60-90 battery amps continuous. It would be perfect for the RV120 and could easily stress the C80100 a fair amount; a C80100-equipped drivetrain with those specs really should be tested to destruction before it gets sold to the general public.
Brakes?
Variable regen lever attached to the Lebowski controller, and then a set of Shimano Zee disc brakes with 203mm rotors on the front and rear hubs as a backup.
Seat style (bike seat versus motocross style seat)?
I'm quite happy with the MX seat; it might make pedaling somewhat more difficult/uncomfortable, but it makes it much easier to stay on and move the bike around at high speeds and torques.
On-board charging, or off board charging to save weight?
Onboard charging; it should be possible to build a 2-4lb bulk charger (especially at high voltages and low currents) that can do 2-4kW worth of CC/CV charging. Onboard charging also lets you use it on longer commutes and trips and plug in as you go; offboard charging will save you some weight on short runs, but on longer trips you're going to need to carry the charger anyway and it's better to have that weight low and in the center of the bike than it is to have that in a backpack or rear rack.
How about range (remember, higher range means more weight and higher cost in batteries)?
I'd like a great deal of range (2-4kWh) overall, which should be doable for cheap if you use Hobbyking packs (which would be my plan); you can put together 5kWh of 4s Turnigy hardcase packs for $1300-1500, which is pretty reasonable.
Would you prefer performance, or range?
I'd like to have at least 5-6kW of power and at least 30-50 miles of range overall.
I am wondering what the market is specifically. I know, in general, what the market is. But, I want some specifics.
If you could design your own bike with realistic goals and attainable performance (not vaporware, unobtainium stuff), what would it be?
Let's dream, here! I know you have all dreamed of your ideal full suspension dirt bike. So, what would it be?
Matt
