Re: (ET) Garden Pulling with the E20

["Tim Humphrey" <hump evgrin com>]

Hmmmm...

I wonder if you were limited by the motor, or the batteries.

Did you do this with floodies?

You said that on the second pull you went into higher current sooner. I 
would expect that if you didn't recharge
between runs. Maybe some AGM's or NiCads would help.

You also said "I rememberd that the more a series wound DC motor is slowed 
down, the more torque it produces (and amps
it pulls, I started to smell the current shunt) ..."

That's true. But, the ET drive motor is not a series wound, it is shunt, 
the small series winding is effectively
useless. Now if you happen to have a snow-thrower or tiller motor laying 
around......

But really I am thinking the problem is with sagging flooded batteries and 
small wiring. I suspect that GE purposely
used the small wire gauge that they did to limit current.

I was working on my Jr. Dragster just last week and noticed that the wires 
going to my motor (stock GE E-15 motor and
wires) were getting very hot compared to the rest of the system. I 
replaced them with the same wire that I'm using for
the rest of the system and those are now stone cold, with a significant 
increase in starting torque. As a side note, I
am removing the drive motor and replacing it with a snowthrower motor. I 
hope to get more low end torque, and likewise
a better holeshot.


-- 
Stay Charged!
Hump
"Ignorance is treatable, with a good prognosis. However, if left 
untreated, it develops into Arrogance, which is often
fatal. :-)" -- Lee Hart

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>
>
> -----Original Message-----
> From: elec-trak-bounces cosmos phy tufts edu
> [mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of Markus
> Sent: Wednesday, May 31, 2006 6:14 AM
> To: 'Tim Humphrey'; elec-trak cosmos phy tufts edu
> Subject: Re: (ET) Garden Pulling with the E20
>
> Hi Tim,
>
> yep, the tire was pretty good for this application.
> I have the 23x10.5-12 agricultural tires. I bought them last year, and I
> remember they were pretty inexpensive compared to other similar tires I
> looked at. The brand was DURO, here is a picture.
> http://www.tiresunlimited.com/images/duro/HF255.jpg
> I got them somewhere on the web and had them mounted at a local tire 
> store.
> Not sure if it was the company from the link above. Most of the other
> pullers had special tires, either the modified agricultural tires (cut to
> make them bite better) or the 26x12 size pitbull tires, specially made 
> for
> garden pulling.
> One comment about the tires: they were cheap and seem to work fine, but 
> they
> stink - even while my tractors were stored outside you could smell them 
> from
> quite a distance. It lasted about half a year, and by now they have lost 
> the
> odor.
>
> However, with the tire above (and low air pressure) I had plenty of
> traction, but no power left. I could've done a run in LL and may have 
> pulled
> it farther but I didn't want to go that slowly.
>
> If I were pulling with the 15hp tractors I think I could have had a good
> chance to win. But compared to the 25hp "tuned" tractors the E20 was a 
> bit
> weaker.
> I've got a spare E15 motor sitting around and thought of putting both 
> motors
> on it, but I don't want to break the gearbox or anything else. So I think
> the aim is to lighten the tractor and have my son drive it in the small
> 350kg/770lbs class.
>
> Markus