Like starting to smoke hot (don't tell Jim!). Right from the brushes -
actually one set I think. Could be they aren't set yet as the motor had
just been rebuilt. All the brush holders were fairly hot to the touch.
The motor housing was cool. I should have run the brushes in with no load.
I didn't measure amps - left my Palm with the Alltrax software at work,
but I bet I was pulling over 300 motor amps.
I know riding around slow in the yard on grass (the bike) is probably
worse case, but I really would like a bit more low end. My problem is I
have to climb a gravel driveway when I get home, so I need decent low
speed power at a lower SOC on the battery.
I know you run a lower ratio too Damon, though I think my rear tire is
bigger - 19". I calculated I get 2.33 MPH/100 RPM. That gives me 63MPH
at 2700 RPM, so I really can afford a higher gear ratio, as I really
don't need to go over 50 or 55. The bike seems to roll easily. I did
some pull tests with a spring scale on a flat concrete floor and it
pulled easily (I forget the value...).
In any case, I already tore it down and started planning out how to run
a chain reduction to the drive shaft. Actually I think it'll be a better
setup physically. Just have a bit of chain noise. BTW is there a source
for drive belts? I would think that would be quieter. Since it's before
the final 3.36:1 ratio it doesn't have to as beefy as a final drive belt
would be - more like a primary belt (if anyone uses them there). I don't
know much about chain and belt drives having owned shaft drives for so
long now.
Anyway, I was grinning a bit!
- SteveS
damon henry wrote:
I would not give up on the shaft drive just yet. What do you define as
hot? It's likely that the insulation in your motor is rated up to 180
deg Celsius. Try measuring the brushes with a temperature probe after
you heat things up. How many amps were you pushing through the motor?
More amps will give you better acceleration (and make things heat up
even quicker). And finally, what speeds will you be doing most of your
riding at, what kind of RPMs will your motor usually be turning, and
how often will you be riding up hill? Lugging the motor at low speed
around home will heat things up because there is no air flow being
generated by the internal fan in the motor. Pulling the same amps to
maintain a higher speed, the motor will run cooler because of the
higher RPMs.
I have been running my motorcycle for years with a chain and a 14
tooth (now 13) front sprocket and a 41 tooth rear. That overall ratio
sounds to me like it is close to what your shaft drive setup
provides... unless I am reading your ratio backwards.
Having said all that, I can ride my motorcycle around all day long at
low speed without any heating issues at all. The times that my motor
has been the hottest has been in the snow when I have used it to drag
the kids around the cul-de-sac on a sled at very lows speeds. That's
easily remedied by a well placed armful of snow, but the extra drag of
towing the kids really heats things up. How well does your motorcycle
roll?
damon
------------------------------------------------------------------------
> Date: Sun, 2 Nov 2008 08:26:43 -0500
> From: [EMAIL PROTECTED]
> To: listserv@electricmotorcycles.net
> Subject: [ElectricMotorcycles] BMW update
>
> Another milestone (of sorts) in my BMW motorcycle conversion journey. I
> had played around with an Elec-Trak motor direct to the shaft drive,
> which proved woefully inadequate. From taking with several people it
> seemed that I really needed to go to a higher gear ratio (the
'built-in'
> ratio is 3.3:1); or, possibly, a bigger motor. Jim Husted found a nice
> 7", 8-brush, motor for me. I thought I'd try it direct just to see,
> which I did yesterday. It did pull away (slowly) from a stop and
> actually had ok acceleration, but the brushes got hot from my low speed
> driving around the yard.
>
> So I guess I'm finally convinced I need to add a gear reduction. I had
> hoped to use a planetary gearset, but really couldn't find anything
> appropriate, so it looks like chain and sprockets. Now I have my winter
> project.
>
> Too bad, as the direct drive was absolutely quite; really sweet.
>
> - SteveS
>
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