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2019 159 EXT HR (3500) in WA
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Discussion Starter · #1 ·
I am doing an electric parking mod (similar to @83Grumman's electric parking brake mod).

I took it out for a road test today and it certainly works well as a parking brake.

However, I can actuate it fully (450 lb actuator) and it will not skid the tires on gravel. This is not what @83Grumman saw:

. . . It will lock the rears if activated at low speed and will drag the rear wheels if I try to drive forward from a standstill. . . .
Apparently, I should have done some more testing with the original brake before I took it apart !

So my request is:

Could you go 10 ~ 15 miles an hour on a gravel road and then apply the parking brake as hard as is reasonable, and let me know if that will skid the rear wheels?

If you cannot lock the wheels, I will trust my math and call it done. If you can lock the wheels, I'll need to get a beefier actuator.

Thanks in advance for your help.
 

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2019 159 EXT HR (3500) in WA
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Discussion Starter · #7 ·
I don't know where I would find a 20% grade . . . .

I tested it on the steepest hill I could think of nearby, but I don't think it is anywhere near 20%
 

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MMXVI - L2H2 in Indiana
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I don't know where I would find a 20% grade . . . .

I tested it on the steepest hill I could think of nearby, but I don't think it is anywhere near 20%
I was trying to image what a 20% looked like, I got some around here that might be close, short roads dropping into the flood plain.
video 20% FF to :34 sec

trying to figure how to convert that to degrees
 

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2019 159 EXT HR (3500) in WA
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Discussion Starter · #9 ·
The linear actuator is rated for 450 lbs at 6 amp - - this is a rated maximum.

I increased my maximum current from 6 amps to 8 amps.

If it stays linear, 8 amps should give 8/6*450 = 600 lbs. With this setting, I can definitely feel the brake pulling, but I do not think it is close to locking.

According to my math, this should be about equivalent to pulling up on the handle with 60 lbs force.
 

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2019 159 EXT HR (3500) in WA
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Discussion Starter · #10 ·
The sin of 20% is about 0.19 so if the van weighed 8500 lb I can see if it took 1600 lbs to pull it :)

But then I just traded one problem that I can't measure with another problem that I can't measure.

I think it's good enough as it is I just wanted a confirmation that I'm not completely out of the ballpark.
 

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2019 159 EXT HR (3500) in WA
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Discussion Starter · #12 ·
I actually like the idea of the parking / emergency brake being an entirely different system (mechanical + drum) from the main system (hydraulic + disk + ABS).

A disc brake with a worn out pad will not work any better with an electrical actuator. Although I have seen systems with an entirely separate caliper and pads for the emergency brake.
 

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2019 159 EXT HR (3500) in WA
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Discussion Starter · #14 ·
WOW , if you can lock up the rear wheels when "parked" it's good . If you can lock them up when turning , holy Bat Turn Batman ! ! !
Wait - - my electric brake does not lock them, I'm wondering if a stock brake can. So get out there and try a bat turn for me!
 

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2019 118" Silver
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Tried it on gravel at the trailhead this morning. At 10mph the left wheel locked right up and dragged about 4 feet before I released the lever. Didn't know it was just the left wheel until after I got out and walked over to look. The van is empty.
 

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May try the same test on pavement later since I want to know how well it works. It does hold the van at what I would guess to be about a 10 deg slope no problem. There's a road near here with what appears to be a 20+ deg slope and I may see if it will hold on that as well. Since it's called a 'Parking' Brake and not an 'Emergency' Brake I'm not expecting much but the more it holds, the better.
 

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2019 159 EXT HR (3500) in WA
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Discussion Starter · #19 ·
Thanks, @h1k3rb, for the data.

It makes me wonder what's going on with only one wheel locking up though. There's a little balance mechanism that make sure the force on both brakes is identical.

Were you pulling up with super-maximum hard jerk force or just firmly easing it up with one hand?

I really wish I had taken some comparison data before I took my mechanical parking brake all apart.
 
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