Brake shoe return springs

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I am repairing the brakes on my very late production 1930 model B that used the 1931 style Bendix Duo-Servo two shoe system. Does anyone have a photo or drawing of these brakes showing the proper placement of the various shoe return springs? My 1930 chassis book pictures the old three shoe system, but has only part numbers for the later system. Both sides are different, so one side or both sides are wrong. Can anyone help? Thanks.

Tom Barrett

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They tie

http://dmacweb.com/tech/brakes/duoservo/DUO.htm

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That should have said, “try this”””

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HI Tom. I have a Bendix brake manual, and it shows the same image as is on the web page that Bill Lyons posted. They sure don’t make it easy to see the springs..

But since this type of shoe setup uses the rotation of the drum to create a ‘servo’ action, or ‘wrapping’ action of the shoes, you want the vertical spring on each side to be pulling the shoe in the opposite direction from normal forward rotation of the drum. So from what I can see, the front shoe only has the common horizontal spring connecting the two shoes together, clamping them agains the cam at the top of the assembly.

Hope this helps..

Greg Long

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Thanks guys. PASB 1989-1 tech page has the same illustrations, but Pierce must have had “improvements” to the system, as both sides of my car have four springs. Very confusing as to which ones are correct. Does anyone have any restoration photos that would show correct spring placement on the model B? It’s pretty important that these things work right. Thanks again.

Tom

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Could the extra springs have been added as a modification by someone trying to improve or ‘fix’ a problem?

Greg

A photo or two of your setup would help.

Greg

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Here’s the spring layout on my ’31 Model 42 with the two shoe brakes. I talked to Eric Rosenau at length about the spring layout and sent him photos of it. He said that he’d never seen a Bendix diagram with the exact Pierce layout but he thought that what I have is probably right.

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Another pic

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Third

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Man, they have more springs than my mattress.

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Bill, those are some great pics.

And yet another example of why PAS people are so great.

They’ll go out and pull the wheels to take pictures to help out another member.

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Tom, you wouldn’t happen to be related to the famous Barrett Brake Doktor? Google it if you have never seen one. Ed 🤔

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Bill, thanks so much for your trouble of getting photos of yours. From that layout, it’s easy to see how confusing these things can get. Here is photo of left front from my 1930 B.

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Here is another, Leigh’s front.

Tom

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Another of the right front.

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Bill,

Your set up looks like someone realized that the springs were getting weak and dragging the shoe.

It looks like they did a “Home Job”” to increase the spring pull by adding extra short springs rather than replacing the weak one / ones.

Peter”

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All four wheels are done exactly the same way and when I got the car I also got a box of brake springs that matched what were mounted. There has always seemed to be a difference in spring layout when the locating pins are at 6 and 12 o’clock versus 3 and 9 o’clock.

Without some sort of factory diagram from Pierce archives or Bendix, we’re all just guessing.

Bill

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Hmm, the Pierce parts manual for ’31 has no drawings, but I’ll check it to see how many brake springs are specified.

Bill

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Here’s the list

P/N

---

Description

---

Qty per wheel

750555 Adjusting Screw Spring

---

1

750640 Cam Lever Bracket Spring

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1

750560 Primary Shoe Spring

---

1

750617 Primary and Secondary Spring

---

1

750621 Primary and Secondary Articulating End Spring 1

750628 Pivot Spring

---

1

750629 Anchor Shoe Spring

---

1

750620 Spacer Rim Spring

---

2

Now the challenge is matching these descriptions to the photos.

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I believe that the Adjusting Screw Spring is the flat one with the open fork on each end.

Also the Spacer Spring should be the spring that holds the shoe in place and has the cotter pin holding it in place. If we remove those two from the list we have

P/N

---

Description

---

Qty per wheel

750640 Cam Lever Bracket Spring

---

1

750560 Primary Shoe Spring

---

1

750617 Primary and Secondary Spring

---

1

750621 Primary and Secondary Articulating End Spring 1

750628 Pivot Spring

---

1

750629 Anchor Shoe Spring

---

1

That’s six springs and I only see five in my photos.

Is one hidden and can’t be seen from the photo? I’m not sure.

Whaddya think?

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