Aero e-bike concept

[tomv]

I've been drawing on the backs of the envelopes various ideas of e-bike I'd really want and they began to stabilize somewhat, so here are share them for you to criticize/improve/show that it's really bad design/etc.

Criteria that I want are:
1) Have safety cell that would protect the driver. This is to improve chances of being hit by a truck. Inspiration BMW C1 - safety similar to small cars.
2) Have drivers head position / overall height similar to cars on the road. This is kind of obvious, but see #3
3) Be very aerodynamic. Inspiration for this are Human powered bicycle record designs - always low racer recumbents. But those are completely non road worthy, could be run over by a truck without being noticed
4) Be very lightweight. Idea here is to achieve similar power-to-weight as cars but use much smaller motors.
5) Use off the shelf e-bike components

Plugging in some numbers that becomes:
1) Weight goal.
- Bike frame, wheels, and hardware 15kg, same as most bikes, should be achievable
- Two x5 motors 20kg
- Fairing/safety cell 30kg
- Batteries LiFePo4, 20kg, 2kWh
- Driver 80kg
Total: 165kg

2) Aerodynamic drag coeficient.
- Cessna 172 is 0.027 and best cars are 0.25. I think hitting 0.15 should be realistic.
- Frontal area of less than 1m^2. So CdA is 0.15, or 4 times less than good cars (say Lotus Elise or Honda Insight)

3) Power: 2x x5 motors using 72V, 40A controller, providing 6kW power draw and approx 4kW at the wheels.
- Max speed then would be really high, way higher than max speed of Clyte motors. So it would easily go to 100kmh or so.
- Acceleration is a bit tricky to calculate.
Time to accelerate is a bit tricky to estimate. Online calculators put at arround 16s for 0 to 100km.

4) Range. If Tesla roadster is getting 120Wh/mile and CdA and weight for it are 4 times larger, then efficiency should be about 40Wh mile. Range then would be 40 miles with 2000wh pack.

5) Component cost should come out to about $3000-$5000.

 

[cerewa]

I've thought about this sort of beast for a long time. If you want a power to weight ratio like a car, you will need two x5 motors but if you don't mind having all the acceleration/hillclimbing of a bus (or of a Prius that's being driven for top fuel economy) you can go with just one motor. Using only one motor will also encourage you to avoid the kind of hard driving that uses up your batteries quicker.

Another way to keep it light would be if you can figure out how to build a strong all in one frame/fairing, as one of BMW's engineers over in germany did. (He had a website about his [unmotorized] bike, but I don't think the site exists any more.) He also kept it simple with only two wheels, and holes in the bottom for his feet.

 

[TylerDurden]

I've been ruminating and sketching too... velomobiles with side-by-side seating.

One feature I give priority is entry/exit of the vehicle: I think it should be intuitive and manageble while holding a cup of coffee.

 

[tomv]

One feature I give priority is entry/exit of the vehicle: I think it should be intuitive and manageble while holding a cup of coffee.

True, that's important. My idea is more towards glider/fighter jet cockpit more than family SUV vibe here though..

It kind of ties in into the whole driving experience thing too. Big sedan might accelerate to 60mph in 5s, but I bet sitting in fighter jet like cabin and going 60mph would give a whole different level of adrenalin.

 

[Toshi]

[youtube]Aq8F_FY7sqw[/youtube]

http://www.bugev.net/

 

[tomv]

BugE looks great! Never saw it before. I still think they compromised too much for convenience I want something that looks like a rocket, no creature comforts for me

More seriously I'm still pondering whether to put two wheels in front and one in the back or the opposite.

From some recumbent discussions I see that tadpole (two wheels in front) have instability when braking because each wheel gets somewhat different braking force and that steers it in unintended way. Put it another way - if one wheel locks and other still turns, CG will be behind them and it will spin the whole vehicle arround. That's why most aeroplanes are most often trike setup and not tail dragger. Steering is also easier to implement with one front wheel. I'm not sure of other pros/cons of this. Do you know of any other tradeoffs?

There are car desings for both T-rex is tadpole, VenturiOne is regular. Aptera EV is tadpole. I guess it's possible to have acceptable performance in either setup...

 

[TylerDurden]

IIRC, it's easier to flip a delta than a tadpole.

That said, I favor the delta since the seated human is wider at the hips than the (forward) extended legs.

Here's another feature I hope to include in my first velo:
A seat that is mostly upright for entry/exit, but slides forward & reclines for travel.

 

[Jeremy Harris]

The reason that aircraft are more stable with a tricycle undercarriage is to do with the relative position of the centre of gravity to the fixed wheels and the lateral centre of pressure. For a taildragger, the centre of gravity is behind the fixed wheels, for a trigear aircraft the C of G is in front of the fixed wheels. For a car or trike, the fixed wheel(s) will usually be at the back, so the C of G will always be in front of it(them).

With three wheel cars two wheels in front is more stable, but the braking equalisation issue does need to be fixed. With hydraulic brakes (like some high end bikes use) this is easy, as all that needs to be done is connect the front brakes to a common cylinder. The pressure is the system will be equal, so the brakes will be evenly applied. It's also fairly easy to arrange the front steering geometry to remove brake steer, or at least reduce it to the point where it's not a problem.

A look at successful three wheel cars shows that some of them with two wheels in the front were pretty close to being as stable as some four wheelers, even at very high speeds. The Morgan racing trikes are a good example. On the other hand, here in the UK we had a state-provided invalid carriage for disabled people, the Invacar, that had a single wheel at the front and was a real death trap (I got to drive one - it was a terrifying machine!). We also have the Reliant three wheel cars over here, but they are only stable because they have such very poor performance. There are several three wheel kit cars available, all use two wheels at the front as far as I'm aware.

I've a feeling that one or two land speed record cars have been two-in-front three wheelers in effect. It's a configuration that fits the aerodynamic requirements better than having two widely spaced wheels at the back.

The final reason for going with two wheels at the front is looks. Tadpole trikes just look so much better. See here for a really neat example: http://www.aptera.com/

Jeremy

 

[Miles]

It's a bit of a slog, but there's useful info here: http://www.btinternet.com/~jhpart/bkencl3.htm

 

[Miles]

http://www.tonyfoale.com/gallery/Trike/index.htm

Love the QT08 8)

 

[TylerDurden]

don't forget about the twike:

http://www.twike.us/

 

[tomv]

I'm really rooting for Aptera, hope they pull it off. For now they do have vaporware feel...

So going into a bit more detail about stability. Seems that tadpole is more stable than delta in turns when braking. Brake and turn tadpole and it will roll over. And solution to that is tilting. I would definetly enjoy leaning into the turn like a bike/motorcycle rather than going in flat and having my head pulled to the side. Wonder how hard is to do something like Carver1/VentureOne.

Here's an example of tilting tadpole trike that's in production! Could be good platform for elecrifying/putting a fairing on:


I was also thinking.... This might be more a bit too sci-fi... Never saw that before. How about retractable gear EV? I mean it's two wheels, completely faired like in Varna Diablo. That thing goes 60mph with 1kW of power. The problem is it plops on the side when stopping. So just add retractable side wheels that lower automatically when speed goes under say 5mph

 

[Miles]

This is a good reference: http://www.maxmatic.com/ttw_index.htm but it hasn't been updated recently.

 

[Miles]

http://www.slashgear.com/ventureone-tilting-trike-to-be-sub-20k-163945.php
http://www.flytheroad.com/

 

[tomv]

Ok, so battle of big boys. VentureOne vs Aptera. Which layout would you like better?

Pro VentureOne:
- Tilts into the turns (more fun to drive, can take turns faster)
- Tandem seats (less frontal area, better visibility, more fun to drive)

Pro Aptera:
- Seems to focus more on light weight/low drag/efficienty
- Less complex chassis probably.

 

[docnjoj]

Those tiltbikes are really amazing. They lock when stopped so U dont do an Artie Johnson, but remain upright. The lock releases at about 5mph, and U balance like a 2 wheeler. I think Dons Raptor did the same, but his is a 2 wheels back and 1 front. Too bad it never got produced!
David

 

[Miles]

Ok, so battle of big boys. VentureOne vs Aptera. Which layout would you like better?

I'm leaning towards the tilting delta layout, at the moment..

 

[Miles]

There's lots of info, videos etc. on the Carver, out there.
http://www.carver-worldwide.com/Home/Index.asp?nc=1

Not electric, though, and more expensive than the VentureOne will (hopefully) be.

 

[Miles]

This stuff is much more exciting than the Tesla yawn Roadster et al...

 

[Toshi]

I'm counting on whatever design gets brought to production in sane numbers for sane prices. Delta vs. tadpole doesn't matter to me as long as it works properly and the design issues inherent in each are addressed in development, not by failures experienced by the end-user.

(Purely emotionally I'm rooting for Aptera, however. The Automotive X-Prize will separate the wheat from the chaff soon enough... http://endless-sphere.com/forums/viewtopic.php?t=3638 )

 

[TylerDurden]

Somewhere between the Funcycle (tilting trike) and the Twike is a tilting e-velomobile that anyone can build.



I am working with flat sheets, since most folks don't want to form plastics or use stinky resins.



It should be possible to get the Cd low (~.024?), even with flat panels.

 

[www.recumbents.com]

Hi All. Long time lurker, first time poster.

I have been thinking about this for some time. Current idea is for a side by side "social" tandem. It would be a faired tadpole trike with gullwing doors.

Power would be pedal plus electric. The idea is to have it be fast enough to run with city traffic (30MPH). I have a couple more projects to complete before I start this one, but it should be very cool.

Current commuter e-bike page: http://www.recumbents.com/wisil/e-bent/default.htm

-Warren.

 

[Papa]

So grab a torch and start making it a reality. The plans are free: http://www.jetrike.com

 

[TylerDurden]

Welcome aboard, Warren.

Welcome to Papa too. (great link!)

We could make a bike here. :wink:


Warren: Sorry to hear about yer finger. Glad to see it hasn't turned you off of the process... the pod looks very nice.

 

[Ben]

I favour the tadpole trike for the stability (more weight spread over two wheels) and aerodynamics.

Something like the Aprilia Magnet concept would be good. Tilting Tadpole.

Doesn't offer much in the way of protection though (let's just say I wouldn't want to have a head on crash in that thing). Also, aerodynamics could be better.