Electric brake testing on old trailer

[Reg]

If you are careful and understand what you are doing, you can very accurately determine the tongue weight of the trailer using the bathroom scale/lever method. You cannot accurately determine the total weight of the trailer this way, you can only estimate that the tongue weight is about 10% of the total weight.

Have you looked through local ads for used trailers getting parted out, or maybe called around to local junkyards? Maybe you can find a trailer that got a little busted up that has a modern axle with brakes wheels and everything, that you can just swap out?

I suggested the method COULD be used on the end of the axles to get the "on the ground" load.
Probably only do one front and one rear wheel and it would be safest to do it at the axle flange, e.g. not on anything that spins around (-:

The 10% rule is ONLY a rule of thumb, you can't work backwards from tongue load to trailer weight.
In my opinion 10% is a minimum, closer to 15% is my preference for trailer stability - as long as the tow vehicle doesn't sag too much, then you are into a whole 'nother set of answers than bring further questions.

 

[slowzuki]

Those cheapy trailers come with used tires too though, usually.

Within a month he had to replace the tires @ $225. You see where he was at when it was all said and done.

 

[Diamondpilot]

Those cheapy trailers come with used tires too though, usually.

The whole trailer was used that he bought. My new trailer I ordered in 2003 had the option of new or used tires. I ordered it with used. 2 reasons. I did not like the brand of tires they were using, Carlisle. The other reason is for my use they would dry rot off before I wore them out. I got 6 years out of them. Never had a flat other than a nail in one. Only replaced them because they were now 10 years old and looked like they could go at any time. This go around I put new Greenball's on it, a good trailer tire.

Chris

 

[Diamondpilot]

When I was in HS we weighed my physics teachers van with 4 pieces of paper, a pencil, a tape measure, and a tire pressure gauge.

Simply pull the vehicles wheels on the paper, trace the foot print of each wheel, remove vehicle and measure each tires pressure and note, measure foot print (Length x Width), and do the math.

Say each tire puts down 6"x6" foot print and the tire pressure is 35psi (pounds per square inch), you will come out with 1260# per tire. 6"x6"x35psi=1260#

The next day on his way to the school he had it weighed and each of the 4 or 5 groups in the class that did this assignment were within 10% of the actual weighed weight. It all comes down to how accurately you trace the tires footprint and how accurately you measure that pattern.

For you you could put the two tires on the paper and do this method and weigh the tongue jack than add the 3 weights together and be really close.

Chris

 

[sailorman]

Thanks again guys ! I appeciate your patience with my questions.

Additional colected info.

Speculative :
1 ) Removed paint from tongue and it 's rated at 750 # . I know it is no where near that now 'cause I can lift it and I 'm a small 5' 6 " guy weighing 132 # . So working backwards ( roughly ) based on loaded trailer weight and max tongue weight of 15 % trailer weight, the original trailer might have been 5000 # . Seems a bit high to me based on looking at axle.

2) I already replaced old tires with new bought to match what previous owner had on it. Don 't know if he had correct load rating tires. New are C type rated at 1360 # so I guess 2 times that for 2720 #. Another oddity.

3) the actual hitch coupler looks like the original may have been cut out and this one welded in. Although that may be just how it was done back in the day. But there are obvious welds. ( I 'll try to post pix of that. )

4) Trailer has no weight distribution rig on it although rudimentory owners manual indicate it may have had it original.

Known :

1) My truck hitch is rate at max. gross tralier weight 6000 # , 600 # tongue with weight distribution and 3500#, 350# without WDS. I will be buying a WDS.

2) truck manual has a great chart explanation of all the weight stuff for towing, but I 'm still working through the understand part. The math is no problem for me.

My OP has evolved a bit away from brake stuff, but it all seems inter-related to me based on the fact I gotta get it all correct to tow safely.

 

[sailorman]

When I was in HS we weighed my physics teachers van with 4 pieces of paper, a pencil, a tape measure, and a tire pressure gauge.
Chris

Now that 's an extremely interesting concept to me as I spent 32 yrs teaching high school Physics among other sciences ! I sure do miss that job ( the teaching part ) ! Teens keep ya young and nothing like seeing the little light bulb go off in their heads even though you 've seen it a million times before.

Gonna try it just for fun and maybe see how close I come after an actual scale weighing ( when its safe to tow ). I got the tires sitting on flat cinder pads now and could check pressures, pencil trace tires, do tongue scale, and do the math.

 

[orezok]

I wonder if you could just take a spray bottle of water and spray around the tire setting on the paper. Let it dry before driving off and it should give you an exact pattern (minus a small amount of creep).

 

[sailorman]

I wonder if you could just take a spray bottle of water and spray around the tire setting on the paper. Let it dry before driving off and it should give you an exact pattern (minus a small amount of creep).

Per your suggestion, I 'm thinking maybe a semi-non porous material ( tight grain wood planks ) to park tires on. Spay around the bottoms with some sort of black paint ( so not to mess up tire too bad ) . Let paint dry and drive off. I just keep seeing paper tearing. Its an estimate, but I really don 't need to be spot on. Just ball park.

I did do tracing on cinder pads with a carpenter 's pencil for fun and got what I think was a reasonable starting estimate. Like your idea to improve area calculation.

 

[Thames Jones]

Hi Sailorman

First and foremost thing is you must go in proper direction to repair the electric brake. You should acquire adequate knowledge about Mechanical and Electrical things to repair Electric brake.

I think without pulling drum you can't get exact idea about electric brake.

Wear safety glasses setting 12 Volts on voltmeter attaching positive wire to one of the brake terminal and another to ground surface. Then after 10 sec read voltmeter should read 12.

If it don't display voltage reverse positive and negative wire and check again by operating brake paddle. Once again read voltmeter if it 0 Voltage is displayed then you have to remove hubcap placing jack underneath.

Removing drum don't solenoids, check the all solenoids using voltmeter whether it is showing 12 volts or not, if not then you replace the solenoid and do check wiring connections between solenoids and brake switch.

After completing procedure check again observing whether wheel stops or not after then pull-together all component.

 

[CurlyDave]

When I was in HS we weighed my physics teachers van with 4 pieces of paper, a pencil, a tape measure, and a tire pressure gauge.

Simply pull the vehicles wheels on the paper, trace the foot print of each wheel, remove vehicle and measure each tires pressure and note, measure foot print (Length x Width), and do the math.

Say each tire puts down 6"x6" foot print and the tire pressure is 35psi (pounds per square inch), you will come out with 1260# per tire. 6"x6"x35psi=1260#

The next day on his way to the school he had it weighed and each of the 4 or 5 groups in the class that did this assignment were within 10% of the actual weighed weight. It all comes down to how accurately you trace the tires footprint and how accurately you measure that pattern.

For you you could put the two tires on the paper and do this method and weigh the tongue jack than add the 3 weights together and be really close.

Chris

Coming anywhere close to the real weight of the vehicle was just plain luck.

The air pressure in tires does not directly support the vehicle, it stiffens the sidewalls which are what really supports the vehicle.

There are two ways to demonstrate this for yourself.

1. Draw a force diagram on the steel wheel at the center of the tire. Air pressure is uniform completely around the wheel, and can not sustain an upward force.

2. Reduce the air pressure in the tires to about 5 psi. The area in contact with the ground increases, but it does not become 6 times greater than the contact area of the same tire at 30 psi.