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Re: (ET) Re: ET reliability

Overall, the tractors that use the armature contactors for reversal have proven to be the units that will withstand operator error. In the magazine articles that appeared after the introduction of the Elec-Trak®, one of the demonstrations was a tire smoking Reverse to Forward to Reverse sequence without the use of the brakes.
Before everyone starts ripping their E20's from fwd to reverse for fun..........
The difference between the E20 and the E15 is that the E15 switches field current to reverse, the E20 switches armature current. Field current is small by comparison, and is thus switched by a small DPDT relay. Armature current is switched by four single pole contactors arranged in a push pull set of pairs.
The problem with an E15 going from moving fwd to reverse is that the difference will make a large *SPARK* across the relay points. Relay points being little things they will melt down in short order and fail.
The E20 contactors are a lot bigger and all that, however the current that they will be subjected to is much higher as well. You probably won't weld them shut (which would be bad) but you will probably pit the contactor and over time it's resistance will increase. This will cause the contactor to get hot while operating and eventually cause voltage sag. I replaced a contactor pair on my E20 (well, actually flipped it upside down to balance the wear since 95% of the time I'm hitting the fwd contactors) and it is a pain in the rear.
To prevent the sparks, both systems use MOVs across the respective points. I think that's a good idea, but a MOV will blow up if you hit it too hard or too many times.
Moral: Please don't throw any tractor from full fwd to full reverse, even if you can. I'm sure it's not good for the transmission either.
Going from speed 1 to speed 1 reverse probably isn't that bad on an E20 since the resistor band will take the brunt of the shock/arc, but it's not good at all on an e15. 

Chris









----- Original Message ----- From: "Elie, Larry (L.D.)" <lelie ford com>
To: "RJ Kanary" <rjkanary nauticom net>; "SteveS" <ssawtelle fcc net>; "et" <Elec-trak cosmos phy tufts edu> 
Sent: Thursday, November 04, 2004 12:40 PM
Subject: RE: (ET) Re: ET reliability
OOPS. Yes, E12 (NOT S) E12 26AE12HA GR17 963. Same control as E12M. The S has the electronic controls. 

I stand corrected.  Yep, THAT'S why it's robust.

Larry Elie


-----Original Message-----
From: RJ Kanary [mailto:rjkanary nauticom net]
Sent: Thursday, November 04, 2004 12:18 PM
To: Elie, Larry (L.D.); SteveS; et
Subject: Re: (ET) Re: ET reliability
Is it within the realm of possibility that there exists some confusion between the E-12 S, which has a front mount mower and electronic controls, the E-12, which also has a front mount mower, but has a centrifugal switch 
on the traction motor, traction  motor reversal handled by contactors and
the E-12 M, that has the same electrical configuration as the E-12, but has 
a mid mount mower ?

----- Original Message ----- From: "Elie, Larry (L.D.)" <lelie ford com>
To: "SteveS" <ssawtelle fcc net>; "et" <Elec-trak cosmos phy tufts edu>
Sent: Thursday, November 04, 2004 10:53 AM
Subject: RE: (ET) Re: ET reliability



I'm a bit surprised.  I've reversed an E12S at speed PULLING A TRAILER
without consequence.  An E15 under similar circumstances fried a board.
The worst I've done is overheat a thermal switch on the drive motor which reset in 10 minutes. That was disking in D2 for too long. I've not tried an E20/I5 because I don't have one. I like simple, and even if something on an E12S goes, it's not too hard to fix. BTW, my E12S doesn't even have any control boards to corrode or fry like a newer models; it's all relays, 
contactors and wire.  Very robust.

Larry Elie


-----Original Message-----
From: elec-trak-bounces cosmos phy tufts edu
[mailto:elec-trak-bounces cosmos phy tufts edu]On Behalf Of SteveS
Sent: Thursday, November 04, 2004 10:24 AM
To: et
Subject: Re: (ET) Re: ET reliability


My understanding is that an E12S is an E15 without the field-weakening
throttle positions (not a PM either). So it is a pretty simple machine.
However, mine does not tolerate reversing without stopping first - the
reverse relay gets eaten. My E20, on the other hand, seems to tolerate
indiscriminate reversing pretty well (no problems yet).

- SteveS


David Roden (Akron OH USA) wrote:


If I'm not mistaken, the later E12 had a PM motor; early production was
wound
field type.  I was thinking that the later PM model was the E12S, but
perhaps
not (or perhaps that's not the "S" difference).


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1970 GE Elec-trak E15 36vdc
1974 Avco New Idea 36vdc
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