Thanks for all your replies - my thoughts are:
- Sorry, I should have been clearer - I am not expecting pedal power to be significant at 50mph, just that it should be significant at 30mph - I already calculated that a velomobile that needed 200W at 30mph would need 900w at 50mph, but a lot of the time, certainly in the UK, you will be on 30mph roads, especially given than 80% of car journeys in the UK are under 10 miles. But when you are on a 40 - 60mph road I think it is safer to match the traffic speed, than to constantly have vehicles overtaking you if you are only doing 30mph which is why I wanted to see how feasible a velomobile is at speeds greater than 30mph.
- Although 1kw maybe enough to maintain 50mph, you need a lot more than a 1kw motor as you need to be able to get up hills and you need a lot of energy to get to 50mph and these 2 are proportional to the weight so a vehicle that is twice as heavy will need about twice the amount of energy to get up a hill and twice the amount of energy to get to a given speed which is why I was looking at getting a vehicle as light as is safely possible.
- For stability, I watched the Aging Wheels videos on the Twike which was fun to watch and yes the Twike looks unstable, much like the Reliant Robin. I think with 3 wheeled vehicles it is more stable to have the 2 wheels at the front and more aerodynamic and even better for stability is to have the 2 front wheels on the outside of fuselage like the Arcimoto FUV and Northern Light 630 so that is has a wider wheel base. But for stability, maybe you need a certain amount of weight to be stable at 50mph - this is where I am really not certain. You have motorbikes like the SUNRA Robo-S which is only 100kg and this can do 50mph, but 2 wheels handle differently than 3.
- For crash worthiness, from a legal point of view, this is not required, and as someone has already said, if you compare this with a motorbike, a motorbike has zero crash protection whereas even with a fragile shell used in traditional velomobiles you have some protection - like this guy crashing at 40mph in a velomobile with only minor injuries. That is not to say crash protection is not important and newer velomobiles have a lot more protection - the NL 630 is designed such that:
“the narrow ends deflect the majority of impacts and the crumple zones are massive. The safety cell around the pilot is double skinned for side impact and incorporates a roll hoop. Even the claw at the rear is designed specifically to ensure that the vehicle is deflected in impacts from the rear”.
The Begorett, at only 40kg, has an aeroespacial aluminium space frame:
“designed to support up to 5 tones in any direction. Constructed with aeronautical grade aluminium. Deformation areas design to absorb impacts.”
So although these are not on a par with modern cars, they are a lot safer in a crash then motorbikes and maybe possibly even on a par with cars 20 - 30 years ago where many didn’t have crumple zones, side impact bars or airbags.
- For wheels, for a pedal bike the rims are 1.5 - 2kg and the tyres 200-300g so each wheel can be under 2kg, but for a velomobile, even classed a moped, they are a lot heavier as the tyres must have a rating so the weight is at least 3 to 4kg. Potentially you can put motorbike tyres on a bike rim as done at 30mph UK road legal electric bicycle , but certainly at speeds of more than 30mph you would want to use a motorbike rim which I think is at least 4kg. I don’t think tyres rated for 50mph are much heavier than those rated for 30mph so potentially there is not much increase in weight required for a 3 wheeled vehicle when up-rating from a moped at 28mph to a motorbike at 50mph. However, one big caveat here is that the forces on a wheel for a bike are different than the forces when used on a velomobile as when a bike corners, the wheel tilts, but it does not on a velomobile and therefore a velomobile will have more lateral forces on the wheels when cornering and this is where I don’t know how strong the wheel would have to be and whether motorbike rims are not even appropriate and if car rims would have to be used which would add a lot of weight.
I would love to see a light aerodynamic vehicle with up to 1 passenger in tandem, where pedalling could be used, not just to give some meaningful input at 30mph, but also to improve health. But, I am under no illusion that it could replace the car(s) in a household, but it could replace the 2nd car as in the UK, nearly half of the households that own a car, own 2 or more and the majority of journeys will be short distances with no passengers
1. This comes down to aerodynamics. On flat ground, after about 1.5 miles of hard full effort sprinting, I can
REACH 50 mph in my Milan SL. It currently has no motor in it, so that is 50 mph purely under pedaling. 50 mph needs about 500-600W of effort to maintain. The Milan weighs 70 lbs, I carry about 15 lbs of stuff, I weigh about 150 lbs, and I'm using bicycle wheels with 20x1.25" Continental Contact Urban tires up front and a 26x1.25" Schwalbe Marathon Greenguard in the rear. While I can't hold 50 mph for long, cruising 30 mph is no problem. 150W is what the manufacturer claims is required to hold 30 mph on flat ground, and that sounds about right. An electric velomobile or a microcar with the aerodynamics of a velomobile and no bicycle drivetrain is subjected to the same laws of physics as this vehicle, and could be made to be every bit as efficient or every close to it. The more aerodynamically streamlined the vehicle, the more that pedaling can contribute to its motive force even at highway speeds. I could foresee a vehicle build lined with 200W of solar panels to where solar power plus 100-150W of pedaling by themselves would be enough to hold 40 mph without draining the battery at all in direct sunlight, with the vehicle built to be robust enough mechanically for cruising at 70+ mph, but still efficient enough to pedalable to 40+ mph in a sprint or cruising 25+ mph when purely under human power not using the motor(s) and with a fit rider. Or roughly 1.5 kW to hold 70 mph, with a moderate pedaling 150W pedaling effort still able to account for 10% or so of road load, if you have the gearing on the bicycle drivetrain to allow it.
2. I'd recommend the 17 lb 1500W Leafbike 3T wind PMDC motor for this. It can do about 2 kW continuous/4kW peak without any added cooling. With cooling, perhaps 4 kW continuous/10 kW peak(which I've done). A Cyclone 3kW mid-drive, Astroflight setup, or a Lightningrods kit would also probably do the trick if you don't want to use hub motors. If you get the aero half as slippery as a Milan SL(twice the CdA value), you'll be holding 90 mph on 4 kW on flat ground with everything upgraded enough not to mechanically fail, in a vehicle potentially weighing under 100 lbs.
3. The delta platform of the Twike coupled with its unoptimized weight distribution, unoptimized aerodynamics, and poor steering geometry are the real culprits in its instability. My much lighter and flimsier custom build direct-Ackermann-steering KMX-trike-based velomobile with a coroplast body shell(the "flimsy kayak" as Chalo calls it) was dynamically stable at 50 mph and didn't
feel scary at all, which was deceptive because the brakes I used were not up to the task, nor were the mechanicals robust enough. But dynamic stability was certainly there, and was still there when doing 70 mph downhill! Not bad for a 91 lb vehicle. The Milan SL is also stable at 50 mph(although the steering is twitchy after 45 mph and a few mm of movement could put you in the next lane) and this vehicle has seen 89 mph down a long and steep hill. The Milan has Sturmey Archer 90mm drum brakes, which while they don't stop as fast as the Avid BB7s, they are a lot more consistent and reliable in their performance, and are trustworthy enough to stop the lightweight Milan from 50 mph(the tires are a more limiting factor than the brakes). Regarding aerodynamics, if your center of pressure is not behind your center of mass, at highway speeds you are going to have lots of trouble!
4. The crashworthiness can probably end up as good as a compact car from the 1960s with careful design considerations(eg. little British sports cars or 1st gen VW Beetle). Roll cage, safety harness, and crumple zones are all a must. Even then, it will still be a death trap, but most accidents will be survivable. Not all. And risk of injury, disfigurement, disability, and/or dismemberment will always be there even in minor crashes. But it would still be a massive improvement over a motorcycle.
5. DOT wheel and tire weight aren't that much worse than heavy-duty bicycle parts if you're careful about component selection. Regarding my KMX corovelo, front rims are 16x1.5" DOT-rated 32-spoke count fit with Mitas MC2 16x2.25" tires. My rear is 16x1.5" with 36-spoke count also fit with a Mitas MC2 16x2.25". When it came to maintaining flat ground cruising speed, the wattage difference between the bicycle parts and DOT parts was not noticable, but ONLY because I was picky about the parts. Normally, DOT parts would be extremely lossy/heavy compared to bicycle parts, but I found a happy medium fit for my application where I gave up a tiny amount of efficiency and added not too much mass for a level of mechanical robustness necessary for highway speeds(at least when it came to wheels and tires). With the motor disabled, the rolling resistance was about equivalent to pedaling around with Schwalbe Marathon Plus 20x1.5"(very similar diameter to 16" DOT tires). While I found this setup to be very usable, the extra 2.5 kg or so total added rotating mass vs bicycle tires/wheels was noticeable and a bit punishing when accelerating from a stoplight purely under pedal effort with the motor disabled, especially up a steep hill on a hot summer day. I do have to rebuild those wheels because I didn't have the right kind of spoke nipples on hand, and will have to track them down, and may ask this forum for wheel building advice so I do it right the 2nd time around lacing the rims to my new front hub motors and so that I don't kill myself.
Here's where I got the rims:
Find many great new & used options and get the best deals for Rim Chrome Steel Italcerchio Wheel 1, 50x16 Holes 32 at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Find many great new & used options and get the best deals for Rim Chrome Steel Italcerchio 1,50 x 16 Holes 36 Wheel at the best online prices at eBay! Free shipping for many products!
www.ebay.com
And the tires:
super sava race tire, MC2 16 x 2.25. also tomos OEM part # 229079
www.treatland.tv
