Re: (ET) Elec-Trak E20 fixing up and modifications (including Curtis conversion)

[Robert Troll <roberttroll hotmail com>]

Thanks for the shout out Ben! Your restoration, and design look great. 
Really did a fantastic job.



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Subject: Elec-trak Digest, Vol 19, Issue 106

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Today's Topics:

   1.  Elec-Trak E20 fixing up and modifications (including Curtis
      conversion) (Ben Carter)
   2. Re:  Elec-Trak E20 fixing up and modifications (including
      Curtis conversion) (David Roden)


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Message: 1
Date: Mon, 8 Nov 2021 03:48:28 +0000 (UTC)
From: Ben Carter <ibekoolman yahoo com>
To: "elec-trak cosmos phy tufts edu" <elec-trak cosmos phy tufts edu>
Subject: (ET) Elec-Trak E20 fixing up and modifications (including
        Curtis conversion)
Message-ID: <132738343 1342477 1636343308326 mail yahoo com>
Content-Type: text/plain; charset="utf-8"

Hey all,
As I promised a few weeks ago, here's the first bit of what I've been 
meaning to share with the group - taking my E20 from "as found" in rough, 
nonfunctional shape to a good working machine, with some healthy 
modifications on the way. I'll write about the loader build and drum brake 
conversion in later emails. Photos of all this are below, and some 
explanation below. Note the loader build starts with the photos of cutting 
a chunk of metal out of the large blue box; anything after that I really 
haven't talked about below except for the lights.
Photos:?https://photos.app.goo.gl/WEffiGGADUV77G9L8
When I got the tractor, it had been sitting for approximately 25-30 years 
and so the batteries were long since dead and gone. I scrounged up three 
marginal automotive starter batteries and used those for testing of the 
tractor. Testing didn't take very long because nothing at all worked 
except the lights - no drive power at all. I pretty quickly decided to go 
with a motor controller rather than have the ancient wiring potentially 
cause trouble time and again - assuming I could even fix it initially!

MOTOR CONTROLLER
Credit to Robert Troll on this list for providing me with advice to get 
started and even selling me some spare small parts for the conversion! I 
bought a used Curtis 1205-105 (400A) from eBay, and from my understanding 
a 1204 would work pretty much identically. With this in hand, I decided to 
gut the entire wiring of the stock tractor rather than deal with corroded 
connections, worn or broken insulation, mouse chewed wires, etc. 
Additionally, this allowed me to rewire all battery connections and the 
motor armature with 2 gauge wire to avoid power loss at higher amperage 
draws. This benefit could be debated but as I was starting from a clean 
slate, I felt it was worthwhile. The PTO and accessory outlets were wired 
with 6 gauge, and everything else (including the motor field) was wired 
with 14 gauge. I believe the only stock electrical parts which were reused 
are two contactors, the accessory breaker, the dash gauges and the key 
switch. Though I suppose the motor counts and the motor breakers as well.
To perform this conversion, I designed the circuit in Visio before I 
actually put anything in motion. This was extremely useful, and helped 
prevent me from making mistakes both in circuit design and execution. 
Below are links to the Visio file as well as a PDF for those who do not 
have Visio. PLEASE NOTE: I am not liable for any mistakes in this diagram 
nor any mistakes or accidents you may have in adopting this circuit to 
your tractor. It's sad I have to say this but always remember you're 
driving a nearly 1,000 pound machine and have a contingency plan in the 
case of electrical failure which causes unexpected acceleration, braking, 
etc.
Visio Circuit 
Diagram:?https://drive.google.com/file/d/1rx7dp2zZz6aDppXKAqzwbBoNP70Wcqe6/view?usp=sharingPDF
 Circuit 
Diagram:?https://drive.google.com/file/d/1L2YTvUkH-FPkGedO3FNPynL7Pz44mHRy/view?usp=sharing
For the new throttle control, I bought a genuine Curtis FP-6D from this 
site:?https://www.tecknowledgey.com/curtis-fp-6-fo-7-footpedal-throttle.html?.
 Yes, there are knockoffs available for about half the price, but this is 
such a critical component I wanted one of good quality build and 
engineering. It wasn't worth it to me to save $70 or so and have something 
which could potentially fail in a way that could cause a serious or fatal 
accident. These throttle controls always have a microswitch to detect when 
the throttle is closed or has been opened. This is useful for designing a 
"high pedal disable" circuit meaning if a safety switch is opened or the 
tractor is flipped from FWD to REV, you must let off the throttle first 
before power will be applied to the field and the armature. Mine came 
wired with the opposite configuration from what I needed for the HPD 
circuit, but the microswitch inside had both normally closed and normally 
open contacts available. I opened the throttle box and simply added a wire 
for the other contact.

CHASSIS AND TIRESThe tractor was covered in surface rust and generally 
looked like heck. I didn't want a show queen but wanted something I could 
be proud of, so I took a hand drill with a wire cup brush and took off all 
the loose paint and rust. Then I hit it with rustoleum primer and 
rustoleum sunburst yellow (IIRC). I did all this after stripping the 
tractor of the wiring and all. I also painted the underside when I had the 
transaxle off and the front axle removed. I didn't bother to fill or patch 
any dents or holes so while it looks pretty good, I'm not afraid to use it.
I replaced the steering pillow block and added whatever flat and/or 
belleville washers I needed to get a good tight mesh of the steering gears.
The tires were all shot and the front wheels were very rusty. I cleaned 
them up as best I could and painted them. The rear wheels are fine but the 
fronts leak air and go flat over several weeks, so at some point I'll add 
tubes or replace the rims. I went with WDT P328 24X12.00-12 4-ply?ag lug 
tires in the rear and?Power King Straight Rib 16X6.50-8 4-ply tires in the 
front. Both front and rear rims are flipped to give a wider track.
The original seat was totally rotted out so I got a replacement seat from 
Tractor Supply. I think it was from their County Line brand and it slides 
back and forth which is pretty neat. It's comfortable and does the job. 
Though it's heavier than the stock seat, so I had to add washers 
underneath the spring which lifts the seat in order for the seat switch to 
work reliably.

FRONT LIFT TO WINCH CONVERSION
My front lift wasn't in good shape, and I figured a small winch could 
double as both a lift and as a way to pull things, or pull the tractor if 
it got stuck. The Harbor Freight 2,500lb ATV winches are cheap, readily 
available and come with a nice wireless feature. I wanted mine hardwired 
to a switch in the original location, so I took apart the original control 
box, removed the contactor and mounted it to my upper dash panel. I used 
two winch backing plates also sold by HF. The pictures show only one on 
the top side of the metal (at the bottom of the front battery box), but I 
later took it off and added a second on the bottom so the original metal 
is sandwiched by the heavy backing plates. The purpose of the bottom 
backing plate is to expand the footprint of the winch so the force is 
spread over a larger area. I also made a roller out of steel to replace 
the stock plastic version.
The winch drum is a bit off center, and I mounted the fairlead to the 
bumper. It's not quite ideal but it works fine. I haven't had to use it 
for anything strenuous, but it should hold up.

ONBOARD SMART CHARGER
I went with a Minn-Kota MK-345PC 12v 3-bank, 15A per bank smart charger. 
The charging amperage could be higher to meet the C20/10 rule, but all in 
all it works fine, it didn't cost a fortune, is reasonably compact, etc. 
The each bank is wired to charge two of the 6v batteries. Given the only 
tap I have is 12v for the winch, this works out very well and generally 
speaking I should not have any imbalance in discharging/charging 
especially because the winch is used infrequently.
You can see in the photos I mounted it to a board above the front 
batteries, where there is plenty of space. I did have to cut out the 
rearmost hood brace to accommodate the charger. I know one member on the 
list wasn't a fan of this charger, but I do think it's a decent 
value/compromise. It does get hot while charging, and knowing heat tends 
to kill electronics I have taken to plugging in a fan to blow on it while 
charging. It's on my to-do list to add a 12v fan + transformer permanently 
mounted in a place where it blows on the charger when the tractor is 
plugged in for charging.

LIGHTS AND OTHER MISC ELECTRONICS
There are myriad different kinds of 12v LED vehicle and work lights 
available from HF, Amazon, and other retailers. I got a rectangular kind 
and after removing the end caps and doing some cutting they fit pretty 
well into the stock headlight openings. I got a third light of a similar 
kind and mounted it to the back of my seat. All three lights are wired in 
series and draw approximately the same amperage so each light sees 
approximately 12v. I don't use them too much, but they are nice and bright 
and good to have when I need them. I recommend the rear work light because 
with all three on you get pretty good illumination all around.
I got panel mount LEDs to use as FWD (green) and REV (red) indicators. 
They are powered by the field voltage and the appropriate LED lights up 
based on the polarity sent to the field. I had to add resistors in series 
with these LEDs but even so one of them burnt out and had to be replaced. 
It's been close to three years since I set this up, so I don't quite 
remember the details. It's not happened again, yet, but I'm probably 
overdriving the LEDs to some degree.
The main disconnect was replaced with a modern version. I recommend this 
as any resistance here is needlessly wasted power. I did have to drill out 
the hole to fit the new disconnect and IIRC I used a tri-flute bit meant 
for tile or something which I bought at Home Depot. I wanted something 
with 3 or more flutes so it would self-center in the existing hole. 
Drilling this on the drill press or milling machine wasn't feasible and 
using such a big 2-flute drill in aluminum with a hand held drill is going 
to be painful.
The PTO and accessory outlets were replaced because they are cheap and the 
original ones were likely corroded on the interior contacts. The seat 
switch was also replaced with a new one.
Once the tractor was proven and working I replaced the starter batteries 
with six proper 6v golf cart batteries. I made all the jumpers with 2 
gauge wire and bolt on ends purchased at an auto parts store.

I hope this proves useful to someone as it took several hours to collect 
my thoughts and write!
Regards,Ben
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Message: 2
Date: Mon, 08 Nov 2021 01:36:59 -0500
From: "David Roden" <etpost drmm net>
To: "elec-trak cosmos phy tufts edu" <elec-trak cosmos phy tufts edu>
Subject: Re: (ET) Elec-Trak E20 fixing up and modifications (including
        Curtis conversion)
Message-ID: <61887F3B 30228 59774271 etpost drmm net>
Content-Type: text/plain; charset=US-ASCII

Ben, that is mighty impressive work.  Well done.

> this allowed me to rewire all battery connections and the motor
> armature with 2 gauge wire to avoid power loss at higher amperage
> draws. This benefit could be debated but as I was starting from a clean
> slate, I felt it was worthwhile.

I don't know who would debate the benefit.

The original wiring was probably deliberately designed a bit undersize, to
limit current to some extent.  That would give the motor some protection.
Since you have a controller that (we hope; see my previous posts on this
topic) properly limits motor current, you can probably use larger wire
safely.

One thing I didn't see you mention is a main breaker or fuse between the
battery and the controller.  Do you have one?  If not, you really should.
A good DC rated breaker could replace the original disconnect, though not
in the same location, I don't think.

> For the new throttle control, I bought a genuine Curtis FP-6D

When I was planning to install the 4QD in my R36 rider, I looked at a
couple of Happ controls, intended for arcade games.  They aren't cheap, but
they seem pretty darn sturdy, even more so than the Curtis potboxes.

As part of installing the Alltrax in the E15, after also looking at a Happ
arcade pedal, I almost used a homebrew pedal and a GE forklift potbox.

In the end, I decided I wanted to stay with a hand control, and used a
Solectria potbox that I had on hand.

BTW, I still have that GE potbox, if anyone is interested.  It's a beast.

> These throttle controls always have a microswitch to detect when the
> throttle is closed or has been opened. This is useful for designing a
> "high pedal disable" circuit meaning if a safety switch is opened or
> the tractor is flipped from FWD to REV, you must let off the throttle
> first before power will be applied to the field and the armature.

I think of high pedal disable as requiring a return to zero after powering
up the controller with the accelerator potentiometer set high, but that's a
good use for it too.

The Curtis controllers don't have HPD built in?  It seems like basic
safety.  A couple of on-road EV Curtis-precursor series motor controllers I
had 30-35 years ago (PMC DCC-96 and PMC-25) certainly had it.

> I didn't bother to fill or patch any dents or holes so while it looks
> pretty good, I'm not afraid to use it.

Very sensible.  Not that I'm opposed to making an ET a showpiece!  It's
just that to me a work tractor shouldn't be too handsome or you won't want
to use if for real work.

I think of the guy who delivered hay to us years ago, and griped because
his shiny new pickup truck got a few mild surface scratches from the brush
along the path to our barn.  I'm an old guy.  In my world, pickups aren't
daily drivers unless you're using them for actual WORK.  Who delivers hay
with a pretty truck?  And who mows and pulls stumps with a pretty tractor?
End of sermon.

> The rear wheels are fine but the fronts leak air and go flat over
> several weeks, so at some point I'll add tubes or replace the rims.

Not uncommon with these old wheels.  My R36's rims are pretty leaky,
especially the used one I got recently to replace a stripped original.
Tubes will be going in soon.

> FRONT LIFT TO WINCH CONVERSION

I'll be keen to hear how this works out with the mower deck and other front
accessories.  We've discussed replacements for the front lift many times on
this list.

> I went with a Minn-Kota MK-345PC 12v 3-bank, 15A per bank smart
> charger.

I hope that works ouit for you.

One thing to watch out for with modular charging - before starting the
tractor, make sure all the battery blocks are actually charged!

If one charger bank fails and you don't notice, you'll be left with a pair
of battery blocks that didn't charge fully, it at all.  Once you start
using the tractor, they'll go flat in a hurry.  You can easily end up
reversing and ruining those uncharged blocks - or worse, get what a friend
of mine used to call a "Trojan Teakettle."

I use individual 12v chargers, and have almost had this happen a couple of
times.  It's easy to forget to check.

> add a 12v fan + transformer

Why not just use a 120 volt AC muffin fan?  Parallel it with the charger
input.

> 12v LED vehicle and work lights

Sounds like a huge improvement over the dim stock incandescent lights.

A couple of years ago I looked at small LED light bars for mounting on top
of the hood, or maybe on the grille, but I never followed through.  Fitting
them to the stock headlight buckets is much more elegant.

> I got panel mount LEDs to use as FWD (green) and REV (red) indicators.

Good idea.

When I converted to the Alltrax, I added a forward/reverse toggle switch/
For a while, I'd forget to put it back into forward after backing up, and
get a suprise.

Eventually I added a reverse beeper.  The Alltrax had an output for one.  I
don't forget any more. :-\

> I'm probably overdriving the LEDs to some degree.

If you put a milliammeter in series, and add enough resistance to limit the
forward current to 20ma, they should last for many years.

> I made all the jumpers with 2 gauge wire and bolt on ends purchased at
> an auto parts store.

Those work, but they're actually meant for temporary use.  Crimp on
connectors are a better choice for the long term, especially with flooded
batteries.

A really good hydraulic hex crimper and a few dies will empty out your
wallet, but you'll be able to hand it down to your grandkids.

Hammer crimpers work OK but don't do a true hex crimp, so they're a bit
controversial in the road EV conversion world, what's left of it.

A manual hex crimper is fine, if you have the chest and arm muscles
required to work it.

If you do, here are instructions for making a low cost manual crimper from
a pair of cheapo-tool-store bolt cutters:

http://evdl.org/pages/dubecrimper.html

Or you can buy a cheap and cheerful Chinese hydraulic hex crimper online.
Mine leaks a bit, but is still hanging in there.  The dies are metric
sizes, but they're usually close enough.


David Roden - Akron, Ohio, USA

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