Modolo sidepull brakes- washer dimple question

I was stripping down some mid-80s Modolo sidepull brakes (name was rubbed off, but maybe one level
below their 'best'?) in preparation for installing them on a new-old bike. There are three washers:
between the front nut and arm, between the two arms, and between the back nut and arm. Black,
probably plastic, 1/32" thick.

Each washer had 4 small dimples on each side, at 90 degree spacings. On the opposite side, there
were also 4 dimples, offset 45 degrees.

Is there a technical reason for these dimples? To hold oil or grease? To prevent friction? There are
no signs of bearings riding on the brake arms at these points so I don't think that they were meant
to hold ball bearings.

Partly curious. Partly because if the brakes work out for this one bike I might machine new washers
out of Delrin as an experiment and I wonder if I will need to make a similar dimple pattern.

"Dan Daniel" <ddandaniel@pacbell.net> wrote in message
news:kpt4tv478rn2e1dburhc07cs2biq7j3ap4@4ax.com...
> I was stripping down some mid-80s Modolo sidepull brakes (name was rubbed off, but maybe one level
> below their 'best'?) in preparation for installing them on a new-old bike. There are three
> washers: between the front nut and arm, between the two arms, and between the back nut and arm.
> Black, probably plastic, 1/32" thick.
>
> Each washer had 4 small dimples on each side, at 90 degree spacings. On the opposite side, there
> were also 4 dimples, offset 45 degrees.
>
> Is there a technical reason for these dimples? To hold oil or grease? To prevent friction? There
> are no signs of bearings riding on the brake arms at these points so I don't think that they were
> meant to hold ball bearings.
>
> Partly curious. Partly because if the brakes work out for this one bike I might machine new
> washers out of Delrin as an experiment and I wonder if I will need to make a similar dimple
> pattern.

I wonder if your 'dimple' washers are like wave washers and hold pressure against the mechanism even
if the nut weren't completley tight.

On Sat, 6 Dec 2003 17:14:32 -0800, "Dave Thompson" <davetspokane1@comcast.net> wrote:

>
>"Dan Daniel" <ddandaniel@pacbell.net> wrote in message
>news:kpt4tv478rn2e1dburhc07cs2biq7j3ap4@4ax.com...
>> I was stripping down some mid-80s Modolo sidepull brakes (name was rubbed off, but maybe one
>> level below their 'best'?) in preparation for installing them on a new-old bike. There are three
>> washers: between the front nut and arm, between the two arms, and between the back nut and arm.
>> Black, probably plastic, 1/32" thick.
>>
>> Each washer had 4 small dimples on each side, at 90 degree spacings. On the opposite side, there
>> were also 4 dimples, offset 45 degrees.
>>
>> Is there a technical reason for these dimples? To hold oil or grease? To prevent friction? There
>> are no signs of bearings riding on the brake arms at these points so I don't think that they were
>> meant to hold ball bearings.
>>
>> Partly curious. Partly because if the brakes work out for this one bike I might machine new
>> washers out of Delrin as an experiment and I wonder if I will need to make a similar dimple
>> pattern.
>
>I wonder if your 'dimple' washers are like wave washers and hold pressure against the mechanism
>even if the nut weren't completley tight.
>

If so, they have completely lost that ability. They are flat, very flat. I don't know if thin
plastic has enough force to serve as a wave washer like spring steel, either. Then again,
considering what I read about Modolo's brakes, maybe things like plastic wave washers help explain
their low reputation?

"Dan Daniel" <ddandaniel@pacbell.net> wrote in message
news:5c85tvoas8kqdpnls2t6iup9fndooo52st@4ax.com...
> On Sat, 6 Dec 2003 17:14:32 -0800, "Dave Thompson" <davetspokane1@comcast.net> wrote: If so, they
> have completely lost that ability. They are flat, very flat. I don't know if thin plastic has
> enough force to serve as a wave washer like spring steel, either. Then again, considering what I
> read about Modolo's brakes, maybe things like plastic wave washers help explain their low
> reputation?

The washers are meant to provide lubrication for the brake and a certain amount of preload to
prevent play without actually causing binding from metal on metal contact. Modolo are not the only
brakes to have those plastic washers by the way. Shimano has used them in the past as well. I don't
think they are inherently bad actually or a flawed design. I always remember Modolo's problems being
more centred on the lever, rather than the caliper, but I could be wrong.

Cheers,

Scott..

On Sat, 06 Dec 2003 16:54:57 -0800, Dan Daniel
<ddandaniel@pacbell.net> wrote:

>I was stripping down some mid-80s Modolo sidepull brakes (name was rubbed off, but maybe one level
>below their 'best'?) in preparation for installing them on a new-old bike. There are three washers:
>between the front nut and arm, between the two arms, and between the back nut and arm. Black,
>probably plastic, 1/32" thick.
>
>Each washer had 4 small dimples on each side, at 90 degree spacings. On the opposite side, there
>were also 4 dimples, offset 45 degrees.
>
>Is there a technical reason for these dimples? To hold oil or grease? To prevent friction? There
>are no signs of bearings riding on the brake arms at these points so I don't think that they were
>meant to hold ball bearings.
>
>Partly curious. Partly because if the brakes work out for this one bike I might machine new washers
>out of Delrin as an experiment and I wonder if I will need to make a similar dimple pattern.

They might just be the injection ports if the delrin washer is injection molded.

On Sat, 13 Dec 2003 21:37:40 -0600, dianne_1234
<dianne_1234@yahoo.com> wrote:

>On Sat, 06 Dec 2003 16:54:57 -0800, Dan Daniel <ddandaniel@pacbell.net> wrote:
>

>>
>>Each washer had 4 small dimples on each side, at 90 degree spacings. On the opposite side, there
>>were also 4 dimples, offset 45 degrees.
>>

>
>They might just be the injection ports if the delrin washer is injection molded.

Ah, now this makes some sense. I don't know much about injection molding and Delrin, and my first
reaction is "8 ports?? On a circle maybe 15 mm diameter?" I'll have to look closer at how the
washers were made. Thanks.

On Sat, 13 Dec 2003 22:10:59 -0800, Dan Daniel
<ddandaniel@pacbell.net> wrote:

>On Sat, 13 Dec 2003 21:37:40 -0600, dianne_1234 <dianne_1234@yahoo.com> wrote:
>
>>On Sat, 06 Dec 2003 16:54:57 -0800, Dan Daniel <ddandaniel@pacbell.net> wrote:
>>
>
>>>
>>>Each washer had 4 small dimples on each side, at 90 degree spacings. On the opposite side, there
>>>were also 4 dimples, offset 45 degrees.
>>>
>
>>
>>They might just be the injection ports if the delrin washer is injection molded.
>
>Ah, now this makes some sense. I don't know much about injection molding and Delrin, and my first
>reaction is "8 ports?? On a circle maybe 15 mm diameter?" I'll have to look closer at how the
>washers were made. Thanks.

After further thought (conjecture?), they might also be the parting lines where the *ejection* pins
(as opposed to *injection* ports) reside in the molds.

At any rate, the marks probably neither help nor hurt performance, and I would be shocked if you
really needed to replicate them on a replacement.