1977 3 wheel -New Toy, My experiences so far - No speed control full or none

SteamPower

Good afternoon everyone, I thought I would signup and say hello, and pose a question. Before I do, let me share what I have done so far.

So, browsing craigslist, I seen a golf cart for $100, well that sounds like a good deal to me. So with $100 in my pocket and a trailer, I head down the road, only about 7 miles away. I pull up, and find a 3 wheel golf cart by EzGo. I was told it is a 1977. I know nothing about golf carts, but am a decent mechanic and electronic tinkerer.

The vinyl seats and backrests looks original, and have no tears at all, which impressed me, as they are that old. I removed the seat, and there is quite a bit of rust in the trays that hold the batteries, but that can always be fixed. The guy told me he put a new solenoid on it, and a new stud on the wiper assembly. All those parts were in a pile, not hooked up.

We push it up onto the trailer, and I get a chance to test the brakes, they worked great, stopped and locked.

Not one to waste time, I get it home, and want to test the motor. I don't have enough batteries to make 36v, so I grab 2. The wires were already off the motor, and it took me a minute to figure out how to wire up the motor manually, realizing you have to go thru the field coil then out to the brushes. Anyway, the motor did nothing, no buzz, hum, nope it wasn't going to move.

So, time to take it apart, thankfully that wasn't too difficult, but the darn thing was heavy to dead lift out of the cart. Got it up on my bench, was loaded full of carbon dust. Once I got the armature out, I seen the problem!! The field coil had broken away from the stud.

Woah, easy fix I thought. I cleaned the stud and the lead wire off really good and fired up my soldering iron. Well this is where things didn't go as planned. The stud would take the solder, but what I thought was tinned copper, turned out to be aluminum, and that wasn't going to solder. I also think the studs are brass.

So digging around on the net, I found that harbor freight sells some special welding sticks called alumiweld, about 15 bux for 8 of them. I went out there, got me a pack, and some other useless stuff that I always buy because I have a coupon. Who couldn't use another set of Chinese screwdrivers for a buck

I get these sticks home, and fire up the torch. Took a few minutes, but figured out that the blue propane wouldn't work, so I switched over to the yella tank. Got both pieces very hot and the sticks flowed very nicely, sticking to both the stud and the field tap. I went ahead and did the other one just to make sure it was good.

So now, get that bugger back together and ready to test again. sitting on the frame, I hit it with 24 volts. The motor jumps to life, and slams the cart backwards into the garage door, leaving a dent- real nice clark! So, we know it goes backwards, lets try forwards, switch the cables on my little battery pack, and zing, it flies backwards again, creating another dent in the garage to complement the other. I then figure out that I need to swap the field coil wires, I do that, this time, open the garage door just to prevent a 3rd mark of glory, and zip, it goes forwards! Right into my grinder stand. Oh well, I got both directions! I push it out of the garage, and head down the road. Granted, I am using 2 alarm system backup batteries to test this thing. It worked great, although that was quite a bit of juice to pull out of these little guys.


My next step is to wire everything up the right way. I clean the oxide off of all the connection points and hook it all up. I also have to find some batteries. I determined I wasn't spending $600ish bux on 6 volt batteries, so I found some Econo Deep cycle 110 amp hr 12 volt from Interstate. I got 3 of them, and made some jumpers out of a old jumper cable and crimp on ring connectors.

Now, its time to really test it. I step aboard the beast, along with my co test pilot, my father inlaw. We face the driveway, and gently press down on the petal. It lurches forward, verp verp verp, its jerking like a horse causing me to bounce and not keep steady pressure on the petal, like a new kid learning to drive a manual transmission car. I try to ease into it again, but it takes off full speed, but as we are on the drive, no big deal. She gets up there, to what the GPS on my phone says 18mph. Pretty fast for my first test.

So with great luck on the blacktop, time to take her off road. This was a little more bumpy, and with only full speed, it made for an interesting ride, finding out that a 3 wheel can turn really sharp, almost too sharp. I end up getting boxed in where I can't get out of some brush, so I switch the lever to backup, and at full speed, head backwards, into another brush pile, we're both smiling, as this is pretty fun.

We have to get off of the cart to push it out of the brush pile, so we pop off, switch to forward, and I tap the petal while we push. It takes off full speed, but with one major problem, we were not in it! I am now chasing my darn cart across the yard, and with every bump, the steering wheel seems to magically turn another direction, as if the ghost in the machine had its own mind for me not to catch it. It headed for the house, and I am able to catch up to it, and jump on. The petal is not mashed, but she won't stop. I thought about hitting the brakes, but didn't want to burn up my motor. I turn off the key, which does nothing and I am fiddling with it full speed on my property, where there is a tree about every 10 feet. Dodging hickories I grabbed the shift lever, and it decides to be difficult. Pushing the lever while driving, I finally get it into neutral, and the cart stops.

I decided to push it back to my garage. I put it up on jack stands, and regardless of the key position, when I shift to fwd or rev, runs wide open. I whack the solenoid with a screwdriver and it stops. I try again, same thing. The solenoid appears to be sticking on, not good. So I dig thru the pile of old parts that came with the parts, and the other one was in there. I put it on and test, it clicks as it should, and the motor responds, but only at full speed.

So after all that, and hopefully your still with me :) What is the best way to test the resistor coils? I tested the voltage coming back from each connection point, and each time its 36volts. I was going to check the resistance of each one, but wanted to get yalls opinion.

Thanks!

BGW

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SteamPower

This morning, I removed the resistor coils, the connections were rusty, but eventually got them off. I took all the ends to a wire brush and shined them up. While I had them off, I tried to measure resistance, but they seem to only have about 2 ohms each, does that sound correct, otherwise my cheapo meter is just poor tolerance.

I hooked them up again, but still we have full speed no matter which stud the wiper is on. Any thoughts?

Thanks

Sir Nuke

CONGRATS on the ride, and Welcome to our happy little corner of the net, and to BGW. There is a BIG fridge on the back porch with anything you can think of in it...help yourself...of course only take what you can LEGALLY have. Make yourself at home on one of the big fluffy couches, kick your shoes off, put your feet up on one of the tables, yes we are allowed to do that, mom's, wive's, husbands, girlfirends and boyfriends here don't care....and take it easy.



oh...btw....every once in a while a food fight breaks out...so you may not want to wear nice clothes here.

Welcome!!

Volt_Ampere

Yes the resistor coils are only a couple ohms.

JohnnieB

The resistor coils don't have many Ohms and I believe all three have different values, but I can't find the specs at the moment.
Anyway they are additive, so in the slowest speed, the current passes through all three in series and at the fastest speed, all of them are by-passed and the battery is connected directly to the motor.

There are three or four flavors of resistor carts, but most of the difference is in the solenoid activation circuit and the high current circuit is pretty much the same in all of them.

Here is the schematic that best shows how the resistors are connected.
And two copies with the high current path highlighted. One in Forward and the other in Reverse.

Hope this helps.

BTW: 18MPH is mighty quick for a resistor cart. 10MPH is typical.

Attached Images

	Resistor cart - Schematic.JPG (87.4 KB, 0 views)
	Resistor cart - Schematic - High Current Traced.JPG (93.5 KB, 0 views)
	Resistor cart - Schematic - In Reverse.JPG (89.8 KB, 0 views)

SteamPower

Ah Ha! That first drawing enlightened me. When I wired everything back up, I had assumed (wrongly) that all the connections on the wiper board were just fine. It looks like someone along the line decided to just put multiple wires on the same lug, so no matter what position the brush is at, you always get full speed. Im headed back outside to see if I can untangle the dangles.

BTW, where do you guys host your pictures at? I have some pics of the cart I wanted to share.

JohnnieB

Photobucket.com

Also, go to the advanced post or reply window and the paperclip icon next to the smiley-face will attach stuff to your post. That's how I attached the drawings.

SteamPower

Well that did it!! Got the wires hooked up correctly, gently pressed down the petal, and I experienced a gentle backwards motion! Each speed selection seemed to do its job. As I took her onto the grass, I got the added experience of a custom smoke screen.

Being a bit careful, I had a fire extinguisher on the back where the clubs go. Little to my knowledge when I was bouncing around the yard, the pin had came out. On a tight turn, the extinguisher fell over, hit the trigger and discharged a giant yellow cloud of baking soda stuff. I thought I had just blew up the batteries and motor. Thinking it was on fire, I jump off to grab the extinguisher, but then I see it was already self discharging, I pulled it away, and things settled back down into a big powder cloud.

So now I have a big yellow spot in my yard, and an empty extinguisher, but, I am thrilled because the speeds actually work! The wife won't be nervous to drive it, and that's always a good thing.

After that, I decided to head down the driveway again, at slow speed. For a minute I thought I was about to have a repeat of the smoke accident, because I was smelling smoke, I turned over my shoulder and could see smoke, but I had the little cover off, and found that it was coming off the resistor coils. They must have had paint, dirt, or other stuff that it was toasting off.

That made me think, am I using the same amount of energy when I am wide open vs slow speed just because the resistors are acting like a giant toaster? I am wondering about running time at slow vs wide open.

JohnnieB

Run time will be roughly the same at all speeds. That is simply the nature of the beast.

There are kits available to convert resistor carts to controller carts, but I don't know it there are any for a '97 3-wheeler.

The problem is mechanical. The controllers typically used in the conversion used a 0-5K potentiometer for the throttle and getting linkage from the pedal to the pot-box might be a challenge. However, if you like to tinker with electrical stuff, you can turn it into a 5-speed controller cart by just adding a controller and rewiring the existing wiper arm switch type throttle assembly with five fixed resistors that add up to 5K. That would give you 0-5K in five steps instead of being continuously variable like it would be with a potentiometer.

Someone post a picture of that setup a few days ago and it took me a while to figure out what was going on. I'll see if I can find the picture and post it here.

------------
Found it.

Looks like they used five 1K resistors, but you could play with the values to customize the speed at each step.
Check out the throttle input values for the controller you use and stay within the max resistance value for the entire series chain of fixed value resistors.

Attached Images

Five speed wiper switch.JPG (163.8 KB, 0 views)

SteamPower

Cool, thanks for the info. So far, I only have $250 in the cart (100 for the cart, and 150 for 3 batts), so I don't think I can spring for a controller, as they look kinda expensive on ebay. I am going to go root around to see where I can come up with a charger, as right now, I am just charging each battery one at a time. :). I did try to go up a steep hill, and she made it, but very slow.