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Strange Brake Arm?

Discussion in 'Early CJ5 and CJ6 Tech' started by Mcruff, Mar 18, 2018.

  1. Mar 18, 2018
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    I received this arm from member "maurywhurt". It was rather dirty and still had a little paint on it, he wanted it rebushed and thought that it already had a bushing in it that just needed replaced. Well it turns out after I cleaned and glass beaded it that the entire arm is a solid piece of bronze, anyone ever seen one like this? It was on his 1966 model (I think), it has the proper part numbers and all. I've never seen anything like this or even heard of anything similar to it.

    bronze brake arm.JPG
     
    Danefraz likes this.
  2. Mar 18, 2018
    PeteL

    PeteL Member 2020 Sponsor 2019 Sponsor

    Hills of NH
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    I think we've seen this discussed before on this site.

    Wasn't one theory that they may have been inventory leftovers from some kind of wartime expedient? Although I'd have thought bronze was more precious than cast steel.
     
    Focker likes this.
  3. Mar 18, 2018
    PeteL

    PeteL Member 2020 Sponsor 2019 Sponsor

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    Focker likes this.
  4. Mar 18, 2018
    Rick Whitson

    Rick Whitson Detroit Area 2020 Sponsor 2019 Sponsor

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    I have to polish that, Good Luck.
     
  5. Mar 18, 2018
    Bowbender

    Bowbender I'm workin' on it! 2020 Sponsor

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    Mine is like that too.
     
  6. Mar 21, 2018
    maurywhurt

    maurywhurt Member 2020 Sponsor 2019 Sponsor

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    I sent Moses Ludel, who wrote several well-known books on classic jeep rebuilding, a link to this thread and asked if he had any thoughts as to why some 1966-67 CJ5 V6 brake arms were solid bronze, rather than steel. He brought up the idea that perhaps the bronze arms might have been "leftovers" from the M38A1 military jeeps that were intended for duty in some kind of harsh environment or other.

    I thought this was an interesting possibility, and did a little investigation. It turns out that though they are very similar, the M38A1 brake arm is not identical to the CJ5 V6 brake arm. The two arms have different part numbers as well.

    Below is a comparison of an M38A1 brake arm at top with a brake arm from a '71 V6 CJ5 at bottom. (The steel brake arm from the '71 is exactly the same shape as the bronze one from my '67 jeep Mcruff posted a photo of above.) Note that the "bends" in these two arms are slightly different:

    [​IMG]

    There must be a reason that some of the CJ5 V6 brake arms were made of cast bronze, but so far it's remained elusive.

    On a side note, like the M38A1 brake arm, the one from my '67 has the smaller pin for the early single-reservoir master brake cylinder. The one from the '71 has the larger-diameter pin to accommodate the later double-reservoir master brake cylinder. Here's the (dirty, unpolished) bronze brake arm from the '67 above the one from a '71:

    [​IMG]


    However, despite the significant difference in the master cylinder pins, these two brake arms have the same part number, 941416. Why Jeep would make them with two very different pin sizes but not change the part number is a mystery to me.

    [​IMG]
     
    Last edited: Mar 22, 2018
  7. Mar 21, 2018
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Cool. It's like the "Willy Wonka's golden ticket" of jeep parts!
     
    TIm E, Bowbender and 47v6 like this.
  8. Mar 22, 2018
    maurywhurt

    maurywhurt Member 2020 Sponsor 2019 Sponsor

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    Moses later shared this further thought as to why some brake arms on the '66-'67 V6 models, which were differently shaped than those used on earlier jeeps, may have been forged from bronze rather than steel:

    "If the arms were limited production at the onset of the V-6 models, Kaiser may have done short orders (small quantities) of these arms, and maybe they were easier to manufacture in bronze at those smaller production numbers. It would be worth comparing the cost for limited production iron versus bronze."
     
    Last edited: Mar 22, 2018
  9. Mar 22, 2018
    PeteL

    PeteL Member 2020 Sponsor 2019 Sponsor

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    I'd buy that. Molten bronze is WAYYYY easier to handle than steel
     
  10. Mar 22, 2018
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2020 Sponsor 2019 Sponsor

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    Son-in-law has a bronze one on his 66 CJ6.
     
  11. Mar 25, 2018
    maurywhurt

    maurywhurt Member 2020 Sponsor 2019 Sponsor

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    More feedback from Moses:

    "The shared part number could simply be an accident. Perhaps an iron arm was supplied to the job shop for duplication in bronze with a request for a new shape to the bronze arm. The iron arm/pattern had the part number embossed, and perhaps the supplier (or Kaiser/Jeep personnel) took it for granted that the short run of bronze arms should be the same part number.

    The pin in the re-bushed arm is clearly a press-in or fitted item, so it may also be that the arms are considered the "same part". In this case, the arm's press-in master cylinder (pushrod) pivot pin determines the application. If I'm guessing right, the arm came alone with a separate part number for the stud. The installer would press the correct pin into place. Replacing the arm would be an alternative to your re-bushing an OEM arm.

    I have an original 1962 edition of the Jeep Universal Parts List. In that era, the parts guide shows a common part number 637408 Brake Pedal Stud for the CJ-3B, CJ-5 and CJ-6 (plus the DJ-3A). The brake pedal "Assembly" is part number 800527, again common to all of these 4-cylinder models. Likely the pin ("Stud") was a service replacement part installed on the original arm. We know that the arm's pushrod pivot pin is wear prone. "​

    Moses' theory very well may be correct. The brake arm and the associated pin may have been differently numbered parts in the Kaiser Jeep Parts List. If so, this would explain the apparent discrepancy that the brake arms with the earlier smaller pins have the same part number as those with the later larger pins.
     
    Last edited: Mar 26, 2018

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