Rear engined E-FF layout (PNG)

Here's a general layout of a rear-engined E-FF for information. Wheelbase is 1575 (approx 62") seat height is 400mm, 100mm less than a Skoda Fabia Greenline. Ground clearance 100mm. 17" wheels. Rear wheel shown with full bump and tyre clearance as extra lines. Provides a battery box, mounted across the vehicle of 200mmx300mmx600m, which I think is quite a good size. Rider is based on an actual human with 38" inside leg (outside 90% Euro male size) which would allow, in my case 10" more room for battery/motor. Obviously more room in the keel for electronics, more batteries, etc. It seems from this that using an ICE motor mounted 'sideways' with shaft drive would require a longer wheelbase or a shorter rider. Rider sits further back than Monoliner, allowing better frontal shape (less drag) but this could be compromised. No attempt made here to optimise fit detail, more or less a cut'n paste of previous designs. Anyone in possession of a crashed E-motorcycle should be able to use this to establish feasibility of conversion - (or sell it to me) Could form basis for Cargo E-scooter. Front suspension stock Mk11 Voyager HCS

Rear engined E-FF layout (PNG)

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Is that battery box really necessary?

Hi Royce, it's good to see this diagram here, but is that battery box behind the rider really necessary? Going by the size of the 14.4 kWhr batteries currently used in the Zero SR/F, DSR and SR I would have thought that there is ample room
for a bigger battery in the keel alone, under the rider's legs, right up to the size of the 20kWhr units fitted in the 168mph Energica MotoE racers.

Battery location

Sorry but to upload picture I had to do my reply as a blog. 48v battery pack location. yours Dave

I'm not advocating for it,

I'm not advocating for it, but one can see from the diagram that a standard head stock mounted front end would in no way impede the rider's forward vision.


I actually talked about this in a mail to Dave Athur, written a few minutes ago. The keel looks attractive, but par it down to the best aerodynamic form, a narrow keel below the wheel spindles, fit the leg protecting cutouts and provide clearence over the top and it's a suprisingly small space. The biggest available box is behind the rider.


Oh yes! You can fit a telefork front end to an FF. And see over the top of it. But I've got a Mk11 Voyager unit so I don't need to. I've also got a BMW C.1 front fork assembly, better than simple tele's, perfect for a lightweight E-FF should anyone be interested.

Real-world potential for this space, in kWh of battery.

I shared the link to the above drawing to the Facebook FF group and it provoked two very interesting comments:

Richard Hatfield, of world record-breaking Lightning electric motorcycles fame writes: "200mm x 300mm x 600mm = 36,000,000 cubic mm/ (1,000,000 ccm per liter) x 600wh / liter = potential of 21.6 kWh pack in the Battery box space in Royce’s diagram. With optimal aero well under 100wh / mile can be achieved. This volume of pack could potentially provide more than 210 miles range."

Herbert Feuerstein, who actually owns a very rare Electric Monotracer adds: "My yellow E-Monster has a capacity of 19,5 kwh gross. Approx. 2-3 kwh not usable, to avoid deep discharge.
At 120 km/h on the highway with 2 persons approx. 230 km distance are possible. Slower ride, means more distance.
At today´s time with new LiIonen batteries approx. 29 - 30 kwh gross charge capacity should be possible, the experts mentioned to me. So in case, some time my batteries will be defect... I know what to do".

That should do it...

That's very interesting from Richard Hatfield and Herbert Feurstein. Real experience and knowledge of actual vehicles.

We can take this a bit further, the above CAD is a "Roadised" development of the Monoliner development racer* I did for Colin Russell. This returned a CDa of .21 in the MIRA wind tunnel on it's first outing and provided enough information to suggest that sub-.2 values were achievable**. I've increased the seat height in the 'Malcolm Newell'(MN) to 400mm., from the 275mm of the racer, to provide good street compatibility and ergonomics, and this will increase drag. But, we can delete the radiator intakes of the Monoliner, add the tweaks learned at MIRA and improve the nose shape (The Monoliner was pushing wheelabase limits, so the rider was placed right forward)

FJ probably makes about .28/9, slightly better than the .3 of 002 (calculated from 'run down' testing) so I think it's reasonable to guess at a CDa of around .24/5 for MN. Obviously I'd like to improve on that, but I expect that there are brains involved here that can come up with performance extimates based on that figure and the 20-odd KWh pack Richard suggests. I did some very basic calculations of the likely performance of Monoliner, with the 90BHP BMW motor and the results were pretty alarming! I believe that for an EV range is the key factor, acceleration and top speed isn't really an issue. So ultimately it is all about the drag figure.

I'm working up the MN as a self-indulgent piece of fun. It's just a single seater. I just fancy doing an E-FF as a finale (and taking bodywork a bit further). But it could be turned into a two seater easily enough, or a cargo scooter, even more easily. But if BMW or Amazon won't do it, why should I?

*The Monlliner was built to then-existing E-racer rules, but fitted with an ICE motor to reduce costs and allow long duration testing without having to wait for battery charge. I don't think it's run under power yet.

** NSU 'Hammock' record breaker CDa .191. Kawasaki 'Ninja', rider in racing crouch. .5. I've seen other race bikes advertised as .44