Jump to content
Model Cars Magazine Forum

Different Types of Truck Air Brakes


Recommended Posts

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

Link to comment
Share on other sites

5 hours ago, plastic trucker said:

I think they were called wedge brakes.

Wedge brake air cylinder, like on your instructions:  Wedge Brake Air Chamber for 5 Ton Military M900 series 6x6's Truck ...

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

Filter Minder® - Air Brake Application

 

2 hours ago, howsthat1959 said:

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

 

Edited by Ace-Garageguy
Link to comment
Share on other sites

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.

1658641475_Reo4.jpg.99441a9d87240b6390d7ccc2ca45eb62.jpg

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

765347384_reo1.jpg.218ad7fbe456e15c3b198b1fcc5a4fe7.jpg

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

2095106638_reo2.jpg.0ed0b303ce9860a00d0a78734bc0a496.jpg

  • Thanks 1
Link to comment
Share on other sites

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 by DRIPTROIT 71
Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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?

Link to comment
Share on other sites

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:

1162354665_wedgeautocar.jpg.78b62aa0d68676e7604255f09adea8b1.jpg

 

660503904_wedgeautocar1.jpg.6c245435b42780b446bf7ba4aa8303ac.jpg

 

85527404_wedgeautocar2.jpg.52d196fde9e25a5233c5a7adbc64feb5.jpg

 

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

1853099900_WedgeIh.jpg.415dc710f32271e01af1f869a0fe220c.jpg

 

Edited by DRIPTROIT 71
  • Thanks 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...