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Technical Mechanical brakes

Discussion in 'The Hokey Ass Message Board' started by sgtlethargic, Jul 1, 2020.

  1. How are all four mechanical brakes (37 Ford, if specifics are needed) actuated by the brake pedal at one time?
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 55,933

    squirrel
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    like this? Kind of hard to see the pedal and linkage, though.

    Flathead_Brakes_37.jpg
     
  3. @squirrel
    Wow, the system is complex. You're right about "hard to see." Where's the pedal (2455?)? Is that top detail drawing the handbrake?
     
  4. Moriarity
    Joined: Apr 11, 2001
    Posts: 30,773

    Moriarity
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    looks like 2455 is the pedal....
     

  5. I'd like to hear and/or see how the pedal mechanism pulls the cables (from opposite directions; fronts versus rears).
     
  6. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
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    Motion is transferred through a series of levers and rods and later cables. A very good, unfailing system, when lubed and adjusted properly. That’s why Henry hung on to it so long. At that time hydraulic systems were prone to total failure.








    Bones
     
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  7. By "later" are you saying that early brake systems didn't have cables?
     
  8. Did other cars have hydraulic brakes?
     
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  9. Deuce Lover
    Joined: Feb 15, 2009
    Posts: 1,047

    Deuce Lover
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    Ford's from 28-38 were mechanical, operated by rods until 1936 then cables 37-38.Hydraulics in 1939.
     
  10. Moriarity
    Joined: Apr 11, 2001
    Posts: 30,773

    Moriarity
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    General Motors had hydraulic brakes a few years before ford did. As a matter of fact one of Henry Fords sales slogans in 1938 was “the safety of steel from pedal to wheel”
     
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  11. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
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    Yes, Henry was one of the last to go to hydraulic. Seals were just not that good at that time. Henry felt like he could depend on mechanical brakes better. Mechanical brakes work just fine, if they are in good shape. Most people don’t know how to adjust them properly.
    99 % on the 100,000 lbs semi truck rolling down the road have air operated mechanical brakes, today, and a lot of them are not properly adjusted!






    Bones
     
  12. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
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    A lot of motorcycles kept the mechanical brakes well into the seventies! I had a 1968 Triumph that had rear mechanical brakes. Just a touch on the brake it would slide the wheel! I now have several bikes with hydraulic rear brakes that suck! It’s not hydraulic vs mechanical that defines the braking ability of a system, it the design and maintenance that makes the difference!








    Bones
     
  13. I've been and might still be a truck driver. In thinking about air brakes I asked myself why trucks have them. I think one main reason is the semi part of semi-truck: It's not a singular unit. As with trains, also.

    ** What pros/cons might there be for air brakes for a hot rod?

    And this has reminded me of figuring out the unmarked bunch of brake rods when I helped restore a steam locomotive. I methodocially went through the reasonable configurations and saw what happened until I figured out what looked like the way they were designed to function.
     
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  14. arkiehotrods
    Joined: Mar 9, 2006
    Posts: 6,803

    arkiehotrods
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    1937 Ford mechanical brakes equalizer actuator
    Screenshot (99).png
     
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  15. Good points.

    I have some Honda Trail 90 stuff. Independent, two-wheel mechanical brake mechanisms are simpler (easier to actuate).
     
    Last edited: Jul 1, 2020
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  16. Where's that part in the above drawing?

    Would the pedal be ~directly~ attached equalizer?
     
  17. squirrel
    Joined: Sep 23, 2004
    Posts: 55,933

    squirrel
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    That is the part that is operated by linkage from the pedal (the bar hanging off to the left), and pulls the cables that go to each wheel (the four clevises).

    how much force does it take to actuate the brakes on an 80,000 lb vehicle? Probably more than you can make with your leg! Air pressure really helps.
     
    Last edited: Jul 1, 2020
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  18. arkiehotrods
    Joined: Mar 9, 2006
    Posts: 6,803

    arkiehotrods
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    There are several for sale on eBay right now. 1937 Ford brake cross shaft assembly
    s-l1600 (33).jpg s-l1600 (32).jpg
     
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  19. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
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    There is a reason air brakes came about was when the “ Semi” became popular. The word semi mean one half, hence a “ semi” is one half of a truck! A tractor with no bed.
    To make the brakes work of the time, hydraulic, everytime you changed trailers you would have to bleed the brakes! Hence the air operated brake system was developed to eliminate bleeding of hydraulic brakes and contamination of the tractor brake fluid with that if a old trailer. Hydraulic brakes , with boost, can easily stop a big truck. The air brake was just easier to use.
    The first air brake systems were like the single hydraulic brakes were. About the same time dual hydraulic brakes came out, so did the daul air brake, ( fail safe) system showed up.

    Also a small leak in an air brake system will not cause the air brake system to fail, but a small leak in a hydraulic system will fail the system.
    Just a few facts on air brakes.

    Also notice the grease fitting in that equalizer. Most of the time on old cars that area was bone dry, no grease! As were other spots on the brake system.



    Bones
     
    Last edited: Jul 1, 2020
  20. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
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    Some brake systems had a “leading “ brake shoe, usually the shorter of the two. This shoe , when applied , would add pressure to the longer shoe. Kinda a free “ power” brake. When properly set up these systems do not require a lot of force to work.
    The problem with a system like this is, it only works good one way! Very poor brakes in reverse. But you are usually going slow in reverse. That’s also why you see these systems on motorcycles, a lot.
    I had a shop truck that I would set the emergency brake every time I parked. I would some times forget to release it while backing out of my shop. No problem, couldn’t even tell the brake was on! But when I tried to go forward, it would lock the truck down and it wouldn’t move!








    Bones
     
  21. arkiehotrods
    Joined: Mar 9, 2006
    Posts: 6,803

    arkiehotrods
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    It's "2458 ASS'Y" in drawing, bottom middle of drawing inside large circle with a line going to where it fits.
    Flathead_Brakes_37 (1).jpg
     
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  22. So, I have a 37 (I believe) Ford front axle/end that I'm wanting to use for a one-off project. I happen to like wide fives. I'm going to consider using mechanical brakes. What other parts, that aren't usually attached to the front and rear axles, would be needed? Any other concerns in setting up?
     
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  23. sunbeam
    Joined: Oct 22, 2010
    Posts: 6,213

    sunbeam
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  24. hemihotrod66
    Joined: May 5, 2019
    Posts: 968

    hemihotrod66
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    I have used mechanical brakes on a couple of restored old Fords and if adjusted to factory specs they work fine... But they were designed to be used on cars of the era and not at the speeds we have today...Some things are better left in the past and those braking systems are one of them....
     
  25. squirrel
    Joined: Sep 23, 2004
    Posts: 55,933

    squirrel
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    They definitely make life easier for tractor trailer drivers!

    But buses also have air brakes...there's more to it than easy trailer swapping.
     
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  26. My project idea would be a grocery getter, so it wouldn't be driven too far nor too fast.
     
  27. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
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    One of the first things you need to concern yourself about mechanical brakes is to have good linings and adjust the shoes with the shoe adjustment. It’s a little harder to do than shorting the rods, so most people just shorten the rods. If you do that the lever that applies the brake will no longer be at a 90degree angle when compared to the rod at max brake. That is the biggest issue with mechanical brakes! Improper adjustment.
    The exact same problem a lot of semis have that are barreling down the highway with 80,000 lbs and more! That is why states have to have inspection sites! To catch these things! Same on older cars!






    Bones
     
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  28. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
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    Theres a whole lot more to it now, but the catalyst that got the air brake movement, way back in the about thirties was easier trailer changing. During that time and a little before there were several systems tried, but the air brake system won out. Obviously due to ease of trailer swap and excellent operation.
    One of the systems tried is the same basic system that is used on rental trailers today, that uses the mass of the trailer, While braking to apply pressure to the hydraulic trailer brakes!







    Bones
     
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  29. hemihotrod66
    Joined: May 5, 2019
    Posts: 968

    hemihotrod66
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    They also require a woven lining not like the material new brake shoes have...
     
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  30. woodiewagon46
    Joined: Mar 14, 2013
    Posts: 2,269

    woodiewagon46
    Member
    from New York

    I've had several Model A's and rebuilding a stock mechanical brake system takes a lot. Every lever, bushing, pin, roller's, wedge's, etc must be replaced in order for it to work properly. I think '37s are even harder to rebuild. I don't know about building your own mechanical brake system from scratch, the pull on each lever must be exact. Hydraulics might be a heck of a lot easier.
     

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