Intelligent Dumb Question:

[Buffalo SpaceShip]

 Video Alert!

Well, Russ, I not only pulled my parking brake at speed... I have the video to show it!

I was only able to get up to 40mph, but it'll give everyone an idea of what it might be like faster. I then ran the same test at around 40mph for a full service brake application.

I have DD3s on my coach (air-assisted aux. diaphragms that take care of parking AND emergency stopping), and it's a 2-axle, 35' model, tipping the scales at a little over 25,000 pounds.

Rather than me ramble on about my observations, I had my kiddos shoot video of the entire exercise. I edited them together briefly into a file showing both applications (on one you can even hear stuff falling to the floor), and then I show them side by side with a time counter.

I would LOVE to see someone shoot video of spring brakes being popped on at speed... and see if I need to eat some crow about some speculations I made about springs vs. DD3s in a previous thread.

The exercise and the results were eye-opening, to say the very least. I want to thank Russ Long for suggesting it in this post!

I welcome any and all observations and points based on what you see (or don't see) here.

Without further fanfare: http://www.thefamilybus.net/videos/parkingbrake.wmv

Cheers,
Brian Brown

EDITED for DUM SPELIN ERORS on 8/8/06

[RJ]

Bump   


Watch this space for comments on Wednesday morning!

[buswarrior]

Brian Brown is my hero!!!!

If you haven't seen his video, click the link and get onto it!

Cecil B Demill got nothin' on you!

happy coaching!
buswarrior

[buswarrior]

And, hats off to you having your kids intimate with the machine!

That's how the next generation gets smarter, fill them up with all the present stuff early, so they can move on from where we leave off!

What a GREAT DAD!!!!

You guessing that spring brakes will do the job in the middle spaces between your two shoots?

I gotta get my teenagers to learn that video stuff!

happy coaching!
buswarrior

[Buffalo SpaceShip]

Brian Brown is my hero!!!!  What a GREAT DAD!!!!

Aw, shucks, Buswarrior! Now I'm blushin'.

I think the real heroes come from the likes of yourself and Russ, using your decades of bus driving and training experience to help some of us newbies learn the ins and outs of our 12+ ton machines... and be safer, more knowledgeable drivers and owners.

But thanks all the same, sir.

You guessing that spring brakes will do the job in the middle spaces between your two shoots?

Well, I did stick my neck out on a previous thread, saying how the DD3s must be superior to spring brake cans because of their complexity. After doing the test, though, I'm not so sure. If they're any worse, it'll take a looooong time to stop a spring brake coach. I have to defer to you experts... and take my licks if I'm wrong.

Sooo... If anybody has a spring brake coach, 30 minutes, and one of those handy digital cameras that shoot videos like mine, I'd be happy to edit the video for a side-by-side-by-side comparison.

This is all so very educational, gentlemen,
bb

[Happycampersrus]

I used the water truck at work for this experiment. It's a 1979 ford ex oil truck with spring brakes. I checked and adjusted the brakes before my run. Well gotta admit that I was really surprized at the out come. LOL.

That is all I'm gonna say untill RJ post.

Dale

[buswarrior]

Brian, I think I can snap a video with my Sony camera without the help of the kids. Amazing the help the camera manual can be when Dad gets desperate to learn!

Too dark here, or I'd go now.

I'll whip off a couple different in-service transit bus models tomorrow and e-mail them to you in the evening.

happy coaching!
buswarrior

[Buffalo SpaceShip]

I'll whip off a couple different in-service transit bus models tomorrow and e-mail them to you in the evening.

buswarrior, you'll likely find the files too large to email (anything over a few megs is too big). If so, drop me an email on my profile account and I'll give you a way to transfer the files directly to one of my domains.

Thanks!
Brian

[RJ]

Oops. . . trade association meeting tonight ran much longer than expected, so no comments until Thursday AM.   

Sorry to keep you all in suspense, but I promise I'll "get-'er done!" 

[TomC]

Brian- thank you for that test! It is about correct at what I've also found.  Your brakes did exactly what they are designed to do, since floating down with the parking brake wouldn't be very good performance, but the service brakes sure did work!  This test is just one of many you should do to be familiar with any type of driving situation.  I can remember as a teenager goofing around in the rain in a parking lot doing doghnuts, eventually getting it to be very controlled.  To this day that training makes emergency maneuvers controlled to the point I've never had an out of control crash.  Along those lines (not to say you should even try to do a doughnut with the bus [doesn't have enough power anyway]), practice behind the wheel at driving forward, backwards, turning, will make the inevitable tight backing into that RV space alot more relaxed on everyone!  Good Luck, TomC

[Len Silva]

Brian- thank you for that test! It is about correct at what I've also found.  Your brakes did exactly what they are designed to do, since floating down with the parking brake wouldn't be very good performance, but the service brakes sure did work!  This test is just one of many you should do to be familiar with any type of driving situation.  I can remember as a teenager goofing around in the rain in a parking lot doing doghnuts, eventually getting it to be very controlled.  To this day that training makes emergency maneuvers controlled to the point I've never had an out of control crash.   Along those lines (not to say you should even try to do a doughnut with the bus [doesn't have enough power anyway]), practice behind the wheel at driving forward, backwards, turning, will make the inevitable tight backing into that RV space alot more relaxed on everyone!  Good Luck, TomC

Have you had any controlled crashes? I thought that only happened when landing an airplane.
Len

[Brian Diehl]

Question... I don't know how this works on a GMC ...  But on my 96A3 the parking brake is regulated by a pressure regulator.  My 96A3 service manual calls for 85psi out of the regulator.  85psi is a lot of pressure to be applied to the brake actuator and while I haven't tried to use the park brake on pavement, at 20 mph on dirt it locks up my drive axle.  Have you checked your pressure regulator to make sure it is giving the correct amount of air to your park brake diaphrams?  

I'm going to be out this weekend with my bus and I will give the park brake a try at 40mph.  Well, I'll try it at 20mph first, then try it at 40.  I'll have my jeep behind me, so it should be a good test.  I'll let you guys know what I find out.

[Buffalo SpaceShip]

Have you checked your pressure regulator to make sure it is giving the correct amount of air to your park brake diaphrams?  

Brian D., from the air system schematic, I don't remember there being a regulator in that side of the system (I could be wrong, since I don't have the book in front of me).

The park brake air could also be throttled back by the ports on the inversion valve. Plus, the aux. diaphram on the DD3 cans is quite a bit smaller than the service side.

Believe me, I was shocked at how little force is applied compared to a service brake application. My fronts can't supply anywhere near the braking force of the rears, so even with them removed from the equation on a park brake actuation, it shouldn't be that different.

Ideally, my next video should show the pushrod extension of both park brakes and service brake applications, since its obviously much less on the park brake one. It's very probable that less pushrod extension on a park brake application is by design to avoid flat spotting the drums over time when busses are sitting. But I'm just speculating again. Hmm...

Any other thoughts/ ideas out there?
Brian B.

[kyle4501]

The spring brakes on my dump truck are on only one of the 2 rear axles. You must have 50 psi air to start releasing them (60 psi for the yellow pop valve to stay disengaged).

So My guess is that the spring brake applies the same force as if the service brakes were applied to ONE axle at 50 psi.

In the case of my truck, that makes for a gradual stop allowing time to het her off the road if you are in light traffic. If in heavy traffic, it allows you to get a lood look at what you are about to run over  - assuming they didn't respond properly to the air horn. 

I do know that if the spring brakes are on, you will not move the truck even with ultra low gearing!

[JackConrad]

How many pounds of air pressure do you think you are applying to the brake cans in a normal braking application. I will wait until tomorrow to tell you how much pressure I use on my MC-8.  Jack