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Old 04-08-2010, 08:11 PM   #1
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harbortj
can electric brakes be used while parked?

Just wondering if one could pull the brake cable or find another means to activate the brakes while parked without damaging anything. Haven't yet investigated the brakes or understand if tehre is a solenoid involved that could burn up?
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Old 04-08-2010, 08:19 PM   #2
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I think it would use such an incredible amount of power that you wouldn't want to go this route. When the breakaway is pulled, it gives the brakes full power, or probably the equivalent of 10 on your brake controller. They would probably cause things to get somewhat hot, despite the absence of friction. You'd also have a noticeable hum coming from every wheel, indicating the electromagnet in action.

I don't know of a solenoid anywhere, the system is relatively simple as a whole.

Since that system runs off the battery, and your converter re-charges the battery, I imagine this would be such a draw that at some point the charging system couldn't keep up and if the trailer wasn't on fire by this point, the battery would lose power more and more and eventually the brakes would release.

I'd guess maybe you'd get an hour or two of solid holding power?

They do almost need to put a second pad inside the drum that is cable driven for a parking brake...

Jon
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Old 04-08-2010, 09:10 PM   #3
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Even if there were no electrical issues, it wouldn't work. Electric brakes don't work like car brakes. When you energize the magnet, it only sticks to the back face of the drum, that's all it does. When the trailer is rolling forward, the drum rolls the magnet forward with it, which operates a lever to make the shoes spread against the ring of the drum and stop the trailer.

So after maybe 1/4 wheel turn forward, or rolling about 20 inches forward, it might hold the trailer. But it wouldn't hold it at all going backwards.

A parking brake is a good idea. I'm surprised nobody has come up with it before (or maybe they have). One might be able to take a car parking brake setup (use the cables, adjuster, and center console lever). Feed the cables through the backing plate. Maybe make some slotted plates or something to attach between the cable ends and magnet levers, so the brake levers can travel normally when the parking brake is not engaged and the cables are not pulled tight. I'm just thinking out loud. It's been ages since I had electric brakes on my trailer.

Now if you had disc brakes like I do, you would burn up the hydraulic pump if you tried to use the energized brake unit as a parking brake. But they do make hydraulic locks that you can put in your brake line. I think they use them for racing. Don't know how well they work, or if they leak over time or not. Another way to do it with disc brakes would be to use car rear calipers that have the built in parking brake. But those are super expensive. Now I think back, I did think about doing that when I designed my disc setup. But there was nowhere near enough clearance between the caliper and the body of the Sunline for the extra levers and all. There was barely enough room for plain calipers as it was.

It would be a neat project to see, but I personally would rather just block the wheels.
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Old 04-08-2010, 10:09 PM   #4
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Re: can electric brakes be used while parked?

Quote:
Originally Posted by harbortj
Just wondering if one could pull the brake cable or find another means to activate the brakes while parked without damaging anything. Haven't yet investigated the brakes or understand if tehre is a solenoid involved that could burn up?
Hi Tim

Here is the inside working.



Iíll add some here that was not yet said as I think you get the message this is not an intended thing to do for a parking brake.

The magnets are coils/solenoids. While the wire size on the breakaway switch limits the amount of current that can pass thru it, you can still get in the neighborhood of 10 amps of current if you have 4 brakes. About 1/2 of that if you have a single axle.

The coils have a duty cycle to them related to the dissipation of heat. 100% duty cycle for hours on end Iím sure will give the coil insulation some serious longevity issues. Not to mention 10 amp hours of power draw from a battery if you are off shore line power. Pending the battery size that 10 amps can use a lot of battery storage capacity in short order. While it is not exactly linear, 10 amps for 6 hours is almost 50% which is time to recharge if your on the group 24 battery. And that means nothing else is using the battery.

If you are on shore power, that 10 amps may be 33% of your converter if you have a 30 amp unit not leaving much left to run the camper and recharge the battery.

Your question is a good one as some do not know. And that is OK to ask as that is how we learn.

The brakes are made for intermitting stopping and they do OK for that. As a parking brake, no, not good. Wheel chocks are the way to go and both sides of the camper ideally.

Hope this helps.

John
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Old 04-09-2010, 11:44 AM   #5
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brakes

Well, I knew there was good reason for it or everyone would use it.
Just didn't know why.

Seems that if these are very similar (and they look similar to rear brakes) that someone would have come up with a retrofit along with somehthing you could find in junk yard or JC Whitney to create a parking brake.

I know it is easy to think up ideas and another to execute it.
Anyway, it is something I might look into at some point- that would be that much less to carry.
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Old 04-09-2010, 12:05 PM   #6
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Re: brakes

Quote:
Originally Posted by harbortj
Well, I knew there was good reason for it or everyone would use it.
Just didn't know why.

Seems that if these are very similar (and they look similar to rear brakes) that someone would have come up with a retrofit along with somehthing you could find in junk yard or JC Whitney to create a parking brake.

I know it is easy to think up ideas and another to execute it.
Anyway, it is something I might look into at some point- that would be that much less to carry.
Tim

Actually they do sell a parking brake. I remember seeing them in Alkoís or Dexter. BUT that all costs money and I think comes with the hydraulic wheel cylinders. What we have is RV Industry standard and is the cheapest you can go in running gear. Yes it works but with the price competition so severe this has never changed. This is not a knock on Sunline as I have not seen any high end brand that has electric drum brakes have anything more then we have. Heck they do not even self adjust... in the 50's automotive created self adjusting brakes. It is only now that some brands are offering them and some offer rubber equalizers. You can buy self adjusting brakes now as a retrofit kit. I upgraded a year ago and they work well as long as the brake drums run true. It only took 60 years to have self adjusting brakes come to the RV industry.

H'mm maybe the parking brake might show up in 2070... and then disk brakes in 3,050Ö Iím joking here of course but this is a sore topic for me.

Hopefully some day they will offer available upgrades in running gear at least and I for one would pay the $100 upcharge in parts difference if it is even that for self adjusting brakes, greasable pivot pins, rubber equalizer, balanced tires, adjustable axle seats and I may even go whole hog and get disk brakes.
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Old 04-09-2010, 06:25 PM   #7
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harbortj
Now John,

You're just being greedy.

I just wanted a parking brake.
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Old 04-09-2010, 09:18 PM   #8
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Quote:
Originally Posted by harbortj
I just wanted a parking brake.
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Old 04-10-2010, 09:50 AM   #9
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harbortj
now that's a parking brake

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