experience of the dahon roo el

in message <[email hidden]>, stupot

(') said:

Anyone out there got experience with the dahon electric folder?
http://www.dahon.com/rooel.htm

Is it just a bit of a gimmic?
I have heard that the power and range are poor?
Is the poor power a fault/limit with the SRAM SPARC hub?
Is the poor range due to a small battery?
- the 16.8V / 8Ah NiMH Battery is a bit unusual - other elec
bikes
seem to have 24v or 36v

I'm usually extremely negative about electric assist bikes, but this one
looks reasonably sensible to me. Combining the motor with the epicyclic
hub has got to be sensible - only one transmission, only one driven
wheel, consequently less drag whether the motor is active or not. And
the bike looks as if it would reasonable to cycle, for short distance
urban trips (which is all an electric bike is ever going to be suitable
for anyway).

I assume the voltage is dictated by the motor.

The power and range of any electric assist bike is poor, as compared to
any other vehicle on the road and particularly as compared to an
unassisted bike; they are a classic illustration of the truism that the
lazy man does the most work. This one, though, looks less of a handicap
than most.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Morning had broken. I found a rather battered tube of Araldite
resin in the bottom of the toolbag.

stupot said:

Anyone out there got experience with the dahon electric folder?
http://www.dahon.com/rooel.htm

Is it just a bit of a gimmic?
I have heard that the power and range are poor?
Is the poor power a fault/limit with the SRAM SPARC hub?
Is the poor range due to a small battery?
- the 16.8V / 8Ah NiMH Battery is a bit unusual - other elec bikes
seem to have 24v or 36v

ta,
Stuart.

The AtoB summary (http://www.atob.org.uk) says:

Dahon Roo EL (Sram SPARC power)***
£1,200
The Sram Sparc is a great idea. It's a combined hub gear and electric
motor, saving both space and weight. The downside in this particular
case is a limited power output, relatively noisy operation and
small-capacity battery. The Sparc-powered Dahon Roo will just about
remove the skin from a rice pudding, but don't expect to climb any hills
unless you're willing to pedal fairly hard. On the positive side, the
whole bike weighs 17.9kgs, making it one of the lightest around, and of
course, it's a folder.

Hope that helps

Tony

Simon Brooke said:

And
the bike looks as if it would reasonable to cycle, for short distance
urban trips (which is all an electric bike is ever going to be suitable
for anyway).

The owner of the Heinzman and Rohloff equipped Grasshopper built to
order by Darth Ben may well have issues with that particular comment...

Quoted message said:

The power and range of any electric assist bike is poor, as compared to
any other vehicle on the road and particularly as compared to an
unassisted bike; they are a classic illustration of the truism that the
lazy man does the most work.

Think you need to get up to speed with what you can do by spending an
appropriate amount of money. I don't particularly have any need or want
of one, but Heinzman equipped bikes with good batteries have high
potential for utility in at least some situations. Have you ever tried one?

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

in message <[email hidden]>, Peter Clinch

(') said:

Simon Brooke said:

And
the bike looks as if it would reasonable to cycle, for short distance
urban trips (which is all an electric bike is ever going to be
suitable for anyway).

The owner of the Heinzman and Rohloff equipped Grasshopper built to
order by Darth Ben may well have issues with that particular
comment...

Quoted message said:

The power and range of any electric assist bike is poor, as compared
to any other vehicle on the road and particularly as compared to an
unassisted bike; they are a classic illustration of the truism that
the lazy man does the most work.

Think you need to get up to speed with what you can do by spending an
appropriate amount of money. I don't particularly have any need or
want of one, but Heinzman equipped bikes with good batteries have high
potential for utility in at least some situations. Have you ever
tried one?

No, but the physics of it are fairly clear. The batteries have finite
energy density, the motor has finite weight and, when not running, adds
a certain amount of transmission drag (unless it can be entirely
decoupled - the SRAM unit can't, and neither can the front hub motor
things like the Heinzman). So when the battery is exhausted you have a
bike which is both heavier and less efficient than a similar but
unassisted bike. So what you are left with is a tradeoff between more
battery (last longer but when it gives out it's _even_ harder work) or
less battery (gives out sooner).

Or, of course, much more expensive battery. But however big or heavy the
battery, sooner or later it gives out, and then you have to lug it and
the motor the rest of the way by muscle-power - unless, as I say, you
limit yourself short distance urban trips.

If you look at Kinetics site you'll see the all up quoted weight for a
Heinzman-equipped bike including batteries is a staggering (and I mean
that literally) 28Kgs. You really, really would not want to have to
pedal that thing once the battery had died. So I stand by what I've
been saying: unless you're using them for very short distance urban
trips, these things are going to be much harder work over all than an
unassisted bike.

The Dahon Roo mentioned in the title uses the fairly light (2.5Kg
including epicyclic) SRAM unit and a fairly small battery, and has a
reasonable riding position. So it's not going to give much assist for
very long but it's not going to be a total joke when the battery has
run out. But it's still not going to be as easy or as pleasant to cycle
as it would be without the motor.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

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