Different Types of Truck Air Brakes

[howsthat1959]

Most truck air brakes have the actuators mounted to the axles and rods that enter the brake drum to apply the brakes. Some AMT kits (including the current new refuse truck with C-900 Ford) have little cylinders mounted perpendicular to the backing plate. I have had no luck finding any information on these things. I'd like to know how the air lines are plumbed to them and how they work as well.

If you can point me in the right direction, I'd appreciate it.

Thanks

[plastic trucker]

I think they were called wedge brakes.

[howsthat1959]

I'm referring to the item circled in red in the picture.

Thanks

[Ace-Garageguy]

5 hours ago, plastic trucker said:

I think they were called wedge brakes.

Wedge brake air cylinder, like on your instructions:  

OPERATION: see page 17 of the manual for perpendicular orientation of the brake cylinder (AKA "chamber") to the wheel backing plate       https://www.axletech.com/at-admin/resources/Manuals/bsm-0381ewedge-brakes.pdf

PLUMBING: Dual lines to each rear air cylinder similar to what you're used to, below

 

2 hours ago, howsthat1959 said:

I'm referring to the item circled in red in the picture.

 

Edited October 12, 2022 by Ace-Garageguy

[howsthat1959]

Wow. Thanks for all the information, pix, vid and pdf. Great!

[DRIPTROIT 71]

The air brakes that you are describing are known as wedge air brakes. Some wedge systems only have one air chamber per wheel. I have not built any of the C-cab Ford kits, but all of the AMT kits with wedge brakes that I have built have two air chambers per wheel. Just like with S-cam style air brakes there are two types of air chambers. There is a single diaphragm (air simply applies the brakes) and the dual diaphragm (one air line applies the brakes, one air line releases the park brake which is engaged by a heavy spring). The single diaphragm is the smaller chamber and only has one air line going to the chamber. The dual diaphragm has two air lines going to the chamber. You will notice the slight difference in the kit parts. The ones that I have seen have the dual chambers mounted at the rear on the rear drive axle and at the front on the front drive axle. The single air line from the single diaphragm chamber comes over the axle next to the backing plate and ties into the air line on the dual chamber line.

If you look closely, on the right rear wheel you can see the single air line come over and tie into the line on the dual air chamber.

This one is harder to see, but you can barely make it out on the left rear.

This one you can barely make it out on the right rear.

[DRIPTROIT 71]

16 hours ago, howsthat1959 said:

Most truck air brakes have the actuators mounted to the axles and rods that enter the brake drum to apply the brakes. Some AMT kits (including the current new refuse truck with C-900 Ford) have little cylinders mounted perpendicular to the backing plate. I have had no luck finding any information on these things. I'd like to know how the air lines are plumbed to them and how they work as well.

If you can point me in the right direction, I'd appreciate it.

Thanks

I tried to put this quote in the post above. I don't know how it ended up down here.

Edited October 12, 2022 by DRIPTROIT 71

[Gary Chastain]

Love this post. One thing I am noticing is the model air chambers appear to be small in scale compared to real life or are there multiple sizes of air chambers? Thanks Ace for the diagram, copied to my photos   

[DRIPTROIT 71]

38 minutes ago, Gary Chastain said:

Love this post. One thing I am noticing is the model air chambers appear to be small in scale compared to real life or are there multiple sizes of air chambers? Thanks Ace for the diagram, copied to my photos   

The piggy back or dual chamber that is in these pictures appear to be the same size as regular s-cam chambers. The ones that I have seen in person (from what I remember) are smaller and closer to the model style.

[Gary Chastain]

Then I wonder, could I use the dual chambers s-cam on an older year model truck to replicate a heavy duty brake system? Directly mounting dual chambers to backing plate. Assuming dual chambers where used on a heavy truck and single chambers used on light duty truck. If this is true, then about what year would the manufacturers stoped using this setup?

[Muncie]

Brake chamber size is related to brake power - the more weight, the larger the chamber

More truck stuff here with a bit on both wedge and S-cam air brake systems - unfortunately, some of the pictures are gone.

 

[DRIPTROIT 71]

1 hour ago, Gary Chastain said:

Then I wonder, could I use the dual chambers s-cam on an older year model truck to replicate a heavy duty brake system? Directly mounting dual chambers to backing plate. Assuming dual chambers where used on a heavy truck and single chambers used on light duty truck. If this is true, then about what year would the manufacturers stoped using this setup?

Most of what I have seen have two chambers per wheel. The single chamber on one side of the axle and the dual chamber on the other side. We always called the dual chamber; "piggyback" chambers because of the heavy spring in them that actuated the park brake. You could pick some good looking piggyback chambers and do a test fit to see how they look. You may have to make a short mounting post. If you are wanting to upgrade to heavy duty, I would just convert to S-cam brakes.

More reference pictures:

 

 

 

This is a Loadstar single axle and it doesn't have piggybacks.

 

Edited October 12, 2022 by DRIPTROIT 71

[Gary Chastain]

Thanks Brian and Steve, good info. In my younger days I learned to drive a GMC cracker box hauling grain in a hopper box then on to better trucks. But I never did any mechanical work. 

[howsthat1959]

Thanks for all the info. Now I know more about this braking system than I ever thought possible.