Re: (ET) Snow's over, E20 is tired...

On Mon, Dec 21, 2009 at 12:48 PM, Chapin, Tim <tchapin bf umich edu> wrote:

My guess is you will always have a problem backing up a hill with a
blower hanging off the front of the tractor regardless of the weight on
the back. I would think the only shot you have is to turn around at the
bottom and drive up the driveway.

Last week the school bus driver tried to do the same thing with a school
bus to turn it around. I am sure if he would have turned the bus into
the side street and back down the hill a bit (instead of driving down
and trying to back up into the side street), the bus would have drove
right up and out.

-----Original Message-----
From: elec-trak-bounces cosmos phy tufts edu
[mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of Graham
Allan
Sent: Monday, December 21, 2009 12:40 PM
To: elec-trak cosmos phy tufts edu
Subject: Re: (ET) Snow's over, E20 is tired...

So what would you say is the major factor in not getting stuck? Weight?
I've tried either blowing or plowing my driveway with my E15 with dismal

results. The driveway is probably around 30 degrees, downwards from the
house, and when it comes time to reverse back up the hill one wheel will

simply lose traction and spin. So I have given up for now (knowing
mainly, I am missing something critical). I've had chains on the drive
wheels but no extra weight, which is probably a big mis-step given the
huge weight of blower or plow blade up front. But I was never convinced
that weight alone would make the difference, given the open
differential... hopefully I'm wrong on that?

How much do you have in the weight box (besides the additional 120 lbs
of lead)?

Graham

On 12/20/2009 12:07 PM, Christopher Zach wrote:
> Well, the snow is over. 20 inches, wet and heavy here in Relay.
> Shoveling it would be very un-fun.
>
> I'm glad I did some blowing yesterday during the storm, enough to make
a
> single-width path and turn-around up the driveway when it was about a
> foot. Because blowing a full 20 inches of snow is tough. Easier to do
> about 3/4 of a blower-width at a time when charging up the hill in L.
>
> Putting the weight box plus 120 pounds of lead stops the wheel
skipping
> problem. The tractor can now blow up the 40 degree driveway in L and
> keep it's chute full. Go too slow or too little snow and it can clog.
>
> Today I widened the scope to the whole driveway. I also hooked up the
> E-Meter to one half of one string to get it working again (since the
> DC-DC exploded probably due to voltage spikes from the dead varistor).
> When going full blast into a 20 inch pile of snow each string is
pulling
> 200a. So the whole tractor+snowblower can pull a peak of 400 amps from
> the pack.
>
> I wonder at what point the wiring in the tractor will start to become
a
> factor.
>
> This also explains why I need a >60ah pack. However the fact that
these
> 30ah cells can put out 7C in 32 degree weather is pretty nice. I like
them.
>
> Right now the pack is on charge. When I looked a few minutes after
> starting it was going at 10a per string (10.5/9.5) for a total charge
> rate of 20a. So in 3 hours or so the pack should be full and I can
> complete the top of the driveway (which includes the slush/snow from
the
> street plows). Then maybe I'll trundle over to the neighbors.
>
> But overall I'd say tractor+blower+chains+weight box+120 pounds=will
not
> get stuck.

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