[Baxsie]

I oiled my cables just to make sure there was binding. My bicycle/motorcycle/industrial experience has taught me the importance of free moving cables.

It appears that the cables that go from the splitter to the hub have some kind of a plastic sheath over the interior metal rope. I assumed that this is a low-friction material.

I suppose I could get some kind of lubrication at the very end of the flex cable, or maybe at both ends if I took apart the hub.

What kind of lube would be appropriate? Silicone spray? Super Lube - - which is some kind of a synthetic PTFE grease?

 

[Baxsie]

I’ve done it at around 15mph in loose gravel and slid about 5’

Cool, thanks for the data. How heavy was your van at the time ?

 

[fishhb]

Not sure but I got 1500 136 high top a queen bed, fridge, sink with 6 gal tank, 130# battery plus 100# of climbing and surfing gear so kind loaded but nothing like a work van would be

 

[h1k3rb]

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.

Yes, wonder about that too and it's partly why further testing is indicated. It was on a packed gravel/sand mix that was wet damp and the left side was disturbed, the right side not at all. I use the parking brake all the time, plus I've kept that linkage area lubed by spraying penetrating lithium grease so if there's a problem it might be at the wheel. Will look for other surfaces and see what happens.

 

[h1k3rb]

Ok, just got back from a series of stops/holds at various angles. Guesstimated using this guide:

Calculating Slope and Common Slopes in Architecture - Archtoolbox

Formulas for calculating the slope of lines or surfaces, plus tables of common slopes used in architecture.

www.archtoolbox.com

At a +/- 10% grade I was able to lock both wheels rolling at 7-8mph and even slid a bit on slightly damp concrete. Was able to hear the right wheel slide too so that seems ok. I'm guessing I hadn't pulled up that hard before the left one locked up earlier and I released it before pulling slightly farther to engage the right.

Went to the steeper hill (asphalt) which could be close to a 20% grade (maybe a bit more) and did the same. Wheels locked, tires slid to a stop and parking brake easily held the van to where I felt it would do well on an even steeper hill. So it seems to be working as designed and I'd even feel fine using it in an emergency stop. It's not going to do nearly as much as the front but would still be better than nothing, unless of course you're about to head into the 'chasm', where it might only give you a few extra moments to review your life as it flashes before your eyes.

 

[83Grumman]

Yes, wonder about that too and it's partly why further testing is indicated.

Maybe you've seem my suggestions about wearing in and maintaining the p brake shoes. I believe that they won't give great grip unless they are worn to the drum, high spots scrubbed off. I occasionally apply mine lightly while driving to keep the surfaces fresh and mated. They will never 'wear in', seat and stay fresh if only used while stationary.

I would expect to find a layer of rust on the parking brake drum if the parking brake is never applied while moving.

I've never seem a brake drum that didn't have a layer of rust if not regularly scrubbed by brake shoes. Look at your discs when parked wet and left for a few days. I guess it might be different if you live in the desert but not where I live.

 

[h1k3rb]

Maybe you've seem my suggestions about wearing in and maintaining the p brake shoes. I believe that they won't give great grip unless they are worn to the drum, high spots scrubbed off. I occasionally apply mine lightly while driving to keep the surfaces fresh and mated. They will never 'wear in' and seat if only used while stationary.

I would expect to find a layer of rust on the parking brake drum it the parking brake is never applied while moving.

I've never seem a brake drum that didn't have a layer of rust if not regularly scrubbed by brake shoes. Look at your discs when parked wet and left for a few days. I guess it might be different if you live in the desert but not where I live.

Had not seen that but after my experience today I have to completely agree. I'm surprised at how well they now work after 'exercising' them a bit.

 

[83Grumman]

Had not seen that but after my experience today I have to completely agree. I'm surprised at how well they now work after 'exercising' them a bit.

Try dragging them some more while driving, off and on. You might notice a change in the sound as well, less scraping as the corrosion wears off.

 

[Baxsie]

There may be something to that wearing in theory. I had my left rear lock twice on wet packed muddy gravel out of perhaps 6 tries.

I am at the point where I am going to call my electric parking brake done. I wrote it up and tagged it onto the bottom of @83Grumman's post.

Thanks to you brave folks that helped me explore the envelope of parking / emergency brake function.

 

[jwork399]

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:



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.

jwork399 - I haven't done an electric brake yet but am thinking about it. from the builds I have seen since it's an add-on, suggest you check that the electric actuator hasn't reached the end of it's travel before parking brake cable reaches it's limits. If the electric actuator isn't pulling the emergency bake cable to end of it's travel, you won't have full braking power. Just my $0.02 thoughts.

 

[Baxsie]

Good point.

The brake cable travel is short, easily less than 1". The actuator I used has 4" of travel - - hopefully I'm good.

ref: 2 Electric parking brake conversions - electric...

There is a video in that post that shows the travel: