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Old 03-24-2003, 12:01 PM   #15
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Brake magnets

Round brake magnets cannot be replaced with the oval magnets.

If someone wants to update their brakes to the more efficient "oval" magnet type, then the entire backing plate must be changed.

The round magnet 12 inch brakes have 5200 pounds maximum braking power, per axle. The 12 inch oval brakes have 7000 pounds per axle.


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Old 03-24-2003, 12:16 PM   #16
 
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Andy

As far as we know, our brakes are OK for now (used trailer only 160 miles, haven't looked at brakes yet).

We have a question for the future:

Do you know what magnets they would have used originally on an Excella 32' 1990 ?

When did they start using oval magnets, and are the round magnets discontinuted ?

Thanks
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Old 03-24-2003, 12:23 PM   #17
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Round magnets are still available.

Oval magnet brakes have been used since the mid 80's.


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Old 03-24-2003, 08:46 PM   #18
 
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Andy : thanks


Nick,
Quote:
I find it useful to be able to disconnect the wires behind each wheel and measure the current to individual wheels when the brake line is activated.
Are you arguing against making a solder joint to each magnet? Or is this process a one time only affair?
Quote:
I use a digital voltmeter with a 20 amp capacity.
It looks as though I'm about to buy one myself. There are several ways I'll need it in the near future.
Quote:
...imbalance in braking, indicated by differing hub temperatures between wheels after a trip.
Yes. I always check the temperatures at the hubs, drums, and tires after the first few miles. After that I check at fuel stops or any other opportunity.
Quote:
...but for Airstream brake lines I use exterior grade wire nuts ...
Is this because, knowing you'll be replacing magnets occasionally, you don't want a permanent connection?
Quote:
...exterior grade wire nuts ..., pre-filled with silicon ...or fill my own empty wire nuts with silicon calk.
Sounds like a good way to keep the water out. Good idea.

Many thanks


John, Thanks for several good points:

Quote:
use heat shrink tubing over a splice. it acts not only as an insulator but also provides strain relief. It also keeps the water out.

not running a ton of solder into a joint helps too, don't fill the wire up! just the joint.
pre thinning helps this so less solder is used.

use crimp connectors with a good quality tool

connectors that terminate at a screw ... slide the wire through the connector just enough to be captured by a washer.

loom your wires!

you get what you pay for with connectors! ....... buy good stuff

voltage drop, more than a couple of percent, then change the wire size.
Regarding soldering: "don't fill the wire up! just the joint"
I take it you mean not to let the solder creep up the wire, away from the joint?

As far as good tools and connectors: I tend to buy at NAPA, but as I mentioned, I'm not delighted. Is there a better place to buy? Tool-wise, I bought the best crimp I could find, but I'd say it's only marginally better than the stamped steel one I already had. Where do I find a good one and what do I look for ?

Somebody on the Escapees Forum told us:

" If you are bothered by the common crimp connectors (especially under your trailer) you could use the GM weatherpack connectors. These are available from any good parts store. Hot rodders use them when rewiring a car. They are wetherproof and you can get them with 2 or even 10 or more contacts. Soldering is still required. "

We have not been able to find them. Any idea ?

Many thanks
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Old 03-24-2003, 09:54 PM   #19
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yup

"I take it you mean not to let the solder creep up the wire, away from the joint? "

yes that's right!

as for tools, i believe the good ones are made by an outfit called AMP.

i'll look around and see...

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Old 03-24-2003, 10:06 PM   #20
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mike

i'm sure your napa tool is ok, this is what i am reffering to...

crimper

this kinda stuff is way out of my budget!

if you ever find one, let me know if i can borrow it!

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Old 03-24-2003, 10:17 PM   #21
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Amp makes good tools, look somewhere like Mouser or Newark electronics for good crimpers. Weatherpacks are expensive and you are not going to be tearing this apart enough to make the expense worthwhile IMHO. You would be better off making a good connection as John said, shrink tube over it, liquid electric tape over that if you don't think it is sealed tight enough.

Connectors are good for something that must be constantly removed. By adding them to brake magnets all you are doing is making 2 connections to add a plug and jack where you would only have 1 in a normal install, and giving yourself twice as many connections to fail.

John
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Old 03-25-2003, 07:32 AM   #22
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Femuse, the method I use suits my particular situation, but I would prefer to solder and heat shrink I if had confidence that I would only be unsoldering the joints every few years. However, my trailer was 14 years old and poorly maintained when I bought it. I had many problems with the braking system. One brake electrical wire had broken inside the frame (try fault-tracing, finding and replacing that!), two wires inside the 7 pin connector had disconnected, the magnets were worn out, the brake shoes were cracked through, the cable from the 7 pin to the converter/charger had been damaged in a tight turn, the breakaway switch was u/s, the Airstream dealer sold me the incorrect brake shoes which caused the wheels to lock up completely. In all, I stripped down the brakes twelve times over a period of months in a field teeming with fire ants. What a nightmare! (The main problem was diagnosing the lock-up fault, in consultation with Dexter and Airstream. Ultimately it was established that there was a change in design of brake shoes some years back, leading to incompatability and jamming of the actuating lever on the metal of each shoe. In the future, when anything wears out, I will replace the entire back plate assembly including magnets, shoes, levers and springs. They're now an economical option). So you can see why I like to be able to disconnect my brake wires easily! The other reason is to check that equal current is going to each magnet when balancing the brakes. You need to measure currents in the order of 12 amps at the 7 pin, (3 amps per wheel, and 4 wheels on my trailer), so a digital voltmeter of 20 amp capacity fits the bill. The one I use is excellent, and costs $40. It is Metex brand #M3800, JAMECO part# 27115, from JAMECO, 1355 Shoreway Rd., Belmont, CA 94002 (800) 831-4242. (www.jameco.com). I disconnect the magnet wire at the wire nut, and connect the meter in series by clipping the meter leads to the two disconnected ends of the brake wire. With the tow vehicle disconnected (important), I pull out the pin on the breakaway switch and take the reading on the meter. If the readings from the four wheels are within a few % of each other, I know to look elsewhere for brake imbalance. I purchased my meter on the advice of Fred and Annie at Phrannie.org. This site gives the distilled wisdom of very experienced full-timers, and is the best source I know for RV wisdom. If, like me, you become a Phrannie disciple, you will have a Jameco meter, you'll fill your black tanks with ice cubes, use Eco-save, throw away your duct tape, chuck out your furnace and refrigerator circuit boards and replace them with Dinosaur boards, etc, etc!! Have fun, Nick.
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Old 03-25-2003, 09:50 PM   #23
 
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John HD

maybe the Forum could build a library of tools that are too extravagant for any one person. We could Fedex them around as needed.
Either way, if I get one of the fancy ones you can borrow it.


John #2,

Thanks for the pointers to Aap, Mouser, and Newark. I'll take a peek.

Also, the point on the superfluous joints that using Weatherpacks would entail is well taken. I'll most likely take another route on that one,

thanks


Nick,

Hmmm... Fire Ants. Lovely little critters. We discovered them while we were broken down by the side of the road in South Carolina. I'm so glad we had an exceptionally cold winter this year, it probably set back their northward progress by 5 years.

As this discussion evolved, it became apparent to me that I'd probably want the brake magnet connections to be easy to work with. I expect to replace them nearly every season, given the mileage we put on.

Regarding current measurement at the magnets. I understand that you wire the meter into series with the magnet, but I'd expect a different reading depending whether you metered on the positive or ground side.

You obviously had a very interesting time working through your trailer's problems. We've been dealing with early 70's trailers from the start. Our first Airstream was 21 years old when we bought it, the second was about the same. While we enjoyed them immensely, we were constantly locked in a battle to keep up with mechanical problems. We've certainly seen some bad wiring. Somehow, I've managed not to buy adequate test equipment, but I think that's about to come to an end. I'll look into that Ammeter from Jameco.

On our 74, 29 footer, after one minor snag after another, we finally decided to replace the entire brake assembly on all four wheels. It helped. At least we now had balanced and reliable braking action.

Our "new" trailer is a 32 ft 1990. I am much better armed this time around and I have no illusions about a free ride. Fortunately this time we're not going it alone. My wife, as you are probably aware, is digging out or sorts of information we can use, from this and other forums. The knowledge and experiennce of folks like the 3 of you is absolutely invaluable.

Phrannie.org looks like an interesting stop. We hadn't heard of it before, thanks.

So far I haven't done much more than crawl under the trailer to find out where things are and what's already in place. Before I begin any physical work I plan to re-read all the accumulated messages and distill them into coherent notes.

Thanks very much,
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Old 03-26-2003, 12:20 AM   #24
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Soaking it all up. First time dealing with a trailer big enough to need brakes.

Few things to comment on. I do a LOT of automotive wiring in the course of my job ( I run a repair shop for Cingular). For crimping I have found Kline brand crimpers are about the best bang for the buck. I have a set of proper $70 ratchet crimpers but I really find these more usefull and a LOT cheaper.

This style is listed as non insulated but they work fine on insulated once you get a feel for them. Why I like this style is it folds the crimp inside it's self instead of just flattening out the connector. I have found that it is less likely to fail and let the wire slip back out. Some crimp connectos will "Relax" after a while. 3M seems to have the least problem with this but they also tend to be the most expensive. My big issue is crimp connectors have a high failure rate when exposed to weather and water. They are fine where they will stay dry. If I have to put one where it might get wet I shrink wrap it or at the very least I'll squeeze some die electric grease in before crimping (most auto parts stores), sometimes both.

Meters...I like Fluke. I have 2 for my personal use including a DC ampereage inductive device. no need to have to put it inline it just measures the magnetic feild with a clamp that goes around the wire and is pretty acurate. Not cheap for a DC model. My work meter is a Certified since I do a lot of work on electronics and the manufactures I do warranty work for require it. With fluke products I have found my non certified meter to be every bit as acurate as my certifed. They have to be recertified every so often and the three times I sent that meter off it has stayed with in a .05% tolerence according to to documentation that comes back with it. I checked my meters against it and then seemed to be right on the money for what I do with them and $150 less for a comparable model. Course the average person can't see the need for a $180 meter with another $200 in accessories (the DC current deal was over $100 wholesale through my bud who was a MAC tool distributor). That's my uncertifed model. The one my work footed the bill for I have $600+ with accessories and 3 recertification at about $120 each with shipping.

Average person would proably do fine with a nice $50 meter tht checks resistance, voltage nad amperage up to 20 amps. Once you have used a few goodies like a wire peircing test lead and specialised probes and clamps you get to looking for more neat toys to go with it. I love this thing and have broken a couple of the clamps I use it so much. Spring loaded deal that clamps around wire from 24gage up to 8 gage. Has a needle that sticks through the insulation so you can check the voltage on the wire real quick. VERY handy for what I do.
This is new version of one I have That's a kit I have the meter with the silcone deluxe leads that you can change the ends. The amperage clamp, and a temperature probe (hay it was on sale!)
Couldn't find a picture of the clamp on lead. www.fluke.com

Course this is what I do for a living so I get my jollys with nice meters and electronic test equipment stuff. My little repair shop has 5 computers and a $50k test monitor that is about to get a $10k GSM service modual installed and a $1000 recertification LOL


Soldering:

Many people don't understand that electricity flows ON the wire strand and not in it. When you make a solder connection it usualy is not able to carry the same current as the stranded wire alone. There is less surface area. Like was pointed out if you make a big blob out of it is the worng way. You want to be able to see the strands. It will have more surface area when you can. THe BIG gain with a solder connection is there is no possiblility of electrolises forming at the connection and in most instances this gain out weighs the other losses.
I have a little butane solder torch made by weller that I like a lot! Nice not to have to drag out a power cord. ( I have a $700 Metcal Solder station on the bench in the office )

Wire and current: A 10 gage stranded wire will have less voltage drop then a 8 gage solid wire (in Gage the lower the number the thicker the wire/material for those that may not know) . Back to the surface area thing I pointed out. The more surface area the less resistance in the wire. A fine strand wire will have much more surface area.


Tools: Don't buy cheap, it will cost you more in the long run. Cheap tools fail often and not have a decent replacement warranty and most good hand tools have a lifetime warranty. Get Craftsman, Husky (home depot), Kobalt (Lowes). Those are decent tools. Snap on and Mac is awsome but that's not stuff you can find in your local stores. Life time warranty does you no good if you don't have a truck coming by every week.
Tools are a lifetime purchace if you take care of them. I have tools from my dad that I still use all the time. I recently broke a 20+ year old craftman ratchet that was my dads and had no problem exchanging it. I put up the 40+ year old ones that were my grandfathers for sentimental reasons. Still work fine though
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Old 03-26-2003, 12:30 AM   #25
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Ground dwelling insects:
Hit Home depot and get Ortho Terimite and insect treatment and a 2.5 gallon sprayer. I keep a batch of this stuff ready at all times. It will take out a ant hill in a couple of hours, same with yellow jackets. Treat the area around the base of my house a couple times a year and it takes care of spiders as well.
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Old 03-26-2003, 09:33 AM   #26
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Femuse, you wrote: "Regarding current measurement at the magnets. I understand that you wire the meter into series with the magnet, but I'd expect a different reading depending whether you metered on the positive or ground side."

I don't know how familiar you are with DC circuits, so forgive me if I'm teaching my grandmother to suck eggs! A DC circuit is analagous to a water hose with water running through it under pressure (volts in the DC circuit). The water, measured in pints (Coulombs), runs through the hose at a number of pints per second. (1 Ampere = 1 Coulomb per second). If you put a load ,such as a turbine, (Resistor, measured in Ohms, such as a magnet) part way along the water hose (circuit), the water (electricity) will do work to overcome the resistance of the turbine (magnet), but the amount of water (current in amperes) entering the turbine (magnet) will be the same amount that exits it. The same applies to the brake circuit. The current is the same amperage in both wires leading to the magnet. The magnet wires are interchangeable, so which one is connected to which on the trailer is irrelevant. (Conventionally, current is considered to flow from the + battery terminal, through the circuit, and back to the - terminal. In fact, electricity is a flow of negatively charged electrons. These are repelled by the - terminal and attracted by the + terminal, so the electron flow is from negative to positive. The ammeter will show the same current in each wire, unless there is a short circuit to ground fault in the section of the circuit including the magnet.)
This simple analogy has always helped me understand DC circuits. I hope I understood the point you made. I don't know much about electro-magnets, so if I've been talking BS, I apologize, and I'm sure someone will put me straight. Good luck. Nick.
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Old 03-26-2003, 09:44 AM   #27
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Nick.

The analogy you stated is the same that I was taught back in the late 40's.


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Old 12-07-2009, 11:18 AM   #28
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Good looking picture of new wiring, here, several posts down, from a junction box (and other good info):

"Trailer Brake Evaluation" on RV.Net (post by JBarca)
http://www.rv.net/forum/index.cfm/fu...d/23429121.cfm
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