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Re: (ET) E-15 not getting out of first speed & reverse relays
I'm more of a mechanical engineering type then an electrical one so I go
with what are obvious signs.
I found that the simples and fastest way to correct it, (once I noticed
excessive heat in the front resisters + sluggish performance and quick
drain on the batteries), was to pull out the throttle and replace all the
micro switches.
After that all works fine, except for the ongoing reverse relays that have
a tendency to fuse up. I consider them the Achilles heel of the tractor
for the last 35 years. Even with all new boards and "up graded relays"
they tend to fuse up and then blow the middle 20 amp fuse.
Thanks,
Hank
-----Original Message-----
From: Briggs, Michael [mailto:Michael Briggs unh edu]
Sent: Monday, May 22, 2017 10:27 AM
To: Kim Petty <kim coveside net>
Cc: elec-trak cosmos phy tufts edu
Subject: Re: (ET) E-15 not getting out of first speed
Kimball,
The main reason I'm not sure that's it is because I have a vague
recollection of fiddling around in there at some point several years ago
as I was disconnecting the instrument gauges (and also reconnecting them),
and I accidentally shorted a ground wire something to the main disconnect,
causing some nice sparking. So it's possible that those burn marks are
from that, rather than from overheating due to excess resistance. Maybe I
should check after running the tractor for a little while to see if the
disconnect feels hot to the touch?
Here's something that would be nice to know - with a fully charged pack
(regular flooded batteries), if someone turns on the mower deck and
nothing else, what do you typically measure for the voltage drop over the
pack? I'm getting 35.6 Volts or so (I think... it might have been 35.5 or
35.7). Is that reasonable?
Thanks,
Mike
________________________________
Michael S. Briggs, PhD
UNH Physics Department
(603) 862-2828
________________________________
________________________________________
From: Kim Petty <kim coveside net>
Sent: Monday, May 22, 2017 10:12 AM
To: Briggs, Michael
Cc: elec-trak cosmos phy tufts edu
Subject: Re: (ET) E-15 not getting out of first speed
Mike, You sent me a picture of your main disconnect switch with a melted
plastic terminal insulation .This indicates too much resistance in the
switch. It could be the contact area or the terminal connections. If you
don't want buy a new one ,I think you will have to remove the old switch
and clean to bright shiny metal all parts including the threads and nuts
on the studs. I don't think just tightening the nuts at this point is
really going to do the trick. What do others think about the main switch
being the 1st problem to tackle here?
Kimball
Sent from my iPad
> On May 22, 2017, at 9:16 AM, Larry Chace <RLC1 etnainstruments com>
> wrote:
>
> Hi, again, Mike. The various models of tractor use various means to
> control the acceleration. Your E15 uses time delays to control the
> speed advance from electric speed #1 to #2 to #3 to Field Weakening;
> each delay is about 2 seconds.
>
> The E12 uses a centrifugal switch to make sure the motor is turning fast
> enough before switching from speed #2 to speed #3 (the higher speed for
> an E12). Other permanent magnet motored tractors also use this
> technique.
>
> Early E20s use some transistors and diodes to check the motor voltage
> before allowing Field Weakening, thereby disabling electric speeds 6, 7,
> and 8 if the motor is working hard.
>
> Later E20s (and my I-5) use a relay to sense the motor voltage and
> thereby control the use of electric speeds 3 through 7.
>
> So, for your situation, the other tractor models aren't relevant even if
> they have exhibited similar problems. (Though it is really difficult to
> imagine *what* could be causing the problems you've seen...)
>
> GE was experimenting, you might say! Also, the foot pedal controlled
> E20 and I-5 perhaps didn't need as much automatic control as did the
> hand operated speed controls. I use both types of controls and each has
> its own advantage.
>
> I've found it useful to have an extra toggle switch that disables the
> higher field weakening speeds. On the E15, that switch permits the
> electric speeds 5, 6, and 7, so when I push the hand throttle full
> forward, I get electric speed 4 (one stage of field weakening); that's
> just a small increase over speed 3. On the I-5, the switch permits the
> use of speeds 4, 5, 6, and 7 (all of the field weakening speeds). That
> lets me just floor the pedal while remaining in speed 3; that is similar
> to the "cruise control" but isn't locked in, so I can lift my foot to
> slow down or stop. Another small modification provides for dynamic
> braking by keeping the field energized (from the shorted armature acting
> as a generator!) until the tractor stops (which happens rather
> suddenly!).
>
> Too much blathering -- sorry!
>
> Larry Chace, Ithaca, NY I-5 and E15
>
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