Mysterious wire

tculpepper

I had a post earlier about burning my wiper board and movable contact up. I think I know why. There was a wire going from the rear side of the solenoid to the first resistor contact. I think this we causing problems. I took this wire off. The cart still works fine. What was this wire originally for?

BGW

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JohnnieB

Its purpose is to prolonging the life of the wiper and first contact.

Without it, full pack voltage hits the leading edge of the wiper and first contact the instant they touch, and the motor is at rest, so the amp draw is high and the leading edges tend to melt from the high current density that flows before they are fully engaged.

The cable from the solenoid to the first contact, shifts the peak instantaneous current flow to the solenoid contacts, which have a larger contact area that the leading edges of the wiper and fist contact.

The voltage difference between the wiper and subsequent contacts is far less than full pack voltage once the motor starts spinning.

tculpepper

That's makes sense.

I was having an arcing issue between the first operating contact and the second. My though was the electricity was making a circle around this wire and arcing between the two. It was almost like the wiper was sitting between the two and it was going to both.

Does electricity flow from the solenoid to the board, or the board to the solenoid? Completely different question.

JohnnieB

1. There will always be some arcing because when there is current flowing through the three resistor coils, there is a voltage difference between the contacts on the wiper board and the greatest of these voltage differences will be between the #1 and #2 contacts, so that transition is will have the most arcing. Other than that, I suspect excessive arcing is more a mechanical issue than an electrical one. Burnt contacts arc more that pristine ones, so the more they arc, the worse they get.

Maybe cleaning or replacing the contacts will help.

2. There are two schools of thought on which way current flows.

The early electrical pioneers assumed and decreed that electricity flowed from Positive to Negative. In their honor, we have what is known as Conventional Current Flow. The direction the arrow points on schematic symbols for diodes, transistors and the like, are part of this legacy.

It was later discovered that carriers of electrical energy (Electrons), flowed from Negative to Positive. This is know as Electron Current flow.

So the answer to your question depends on which of the two diametrically opposed definitions of current flow is used, but the bottom line is that it doesn't make much, if any, difference, since it flows nearly instantaneously at all points in the circuit.

Making the question even less answerable, the direction of current flow through the solenoid and board depends on whether the F/R switch is in F or R is some Resistor Carts. See attached.

Attached Images

	Resistor cart - Schematic - High Current Traced.JPG (93.5 KB, 0 views)
	Resistor cart - Schematic - In Reverse.JPG (89.8 KB, 0 views)

tculpepper

And that is why I ask question! Somebody always knows the answer! All of this started when I broke the fourth resistor stud. I replaced it. It became loose and wallowed out the mounting hole. I had to get a new board and ever since then, its been acting up. My brakes are gone from the addition of the new tires. When you are riding and it keeps going when you let go of the pedal, it wakes you up quick! I'm working on getting up the funds to swap over to a controller system.

simple man

I'd get brakes first!
If you ever have a runaway condition, put the F-R selector in neutral. This interrupts any current flow to the motor.

tculpepper

That's what I have to do when it acts screwy. When I get home I fiddle with it and fix it. I can pull everything apart and have it back together in a few minutes now! I'm on a very tight budget, so I just have to live with it. Brakes are high! I guess they're worth it if they keep you safe.

simple man

First time you clobber your wife's car with the cart, you'll find out how cheap those brakes are!

kellybell

I had a "mysterious wife" once. She was great!