Monte# 209, Double Brake Pedal

[Rupunzell]

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After making a SAE660 bearing bronze replacement bushing for the pedals, Dennis G from MonteCarlo Consortium mentioned brake pedal flex noted after he did the nearly identical fix to the Monte pedal box. Dennis solution to this flexi brake pedal was to make a boxed section brake pedal:

Inspired by Dennis, went looking for a spare brake pedal. Thanks to the Generosity of Tony F, a spare brake pedal arrived.
Set it up in the BPM to center the machine tool spindle to the brake pedal bushing with a Blake Indicator (these work, the imitation ones sort of work).

Apply boring head running CCW until the bushing weld has been removed.

Remove the brake push rod pin by cutting off the riveted end.

Center the BP spindle to the brake clevis pin hole on the first brake pedal:

Hole measured 0.399", ream hole to 0.406".

Make two alloy steel bushings on the lathe:

Press the alloy steel bushings into the reamed hole in to both brake pedals.

Set up the double brake pedal for brazing the two together at the bushing:

Set up the torch, flux, heat, add filler bronze:

Check double pedal alignment with each other. There will be inherent offset due to the angles and distance
between the two otherwise very similar stampings.

Set up the double pedal assembly in the BP, make a spacer on the lathe to -0.002" less than the
now fixed spacing between the two pedal stampings. Drill and tap the first hole. Apply screw to clamp in place.
Set up to drill and tap the other three holes. The top two holes are 5/16-24 threaded on one pedal, the other pedal
gets a 5/16" clearance hole with 100 degree countersink. The bottom two near the pedal pad are 1/4-28.

Last hole set.

Slit saw part of the old pedal pad to be used as pedal pad extension for the first pedal pad.

Make a 0.062" thick steel backing plate. Clamp it all together, flux, prep for brazing.

Set up the torch, heat, add brazing bronze, SST wire brush clean up.

Prep double pedal for final assembly:

Prep NAS1580 torq-set titanium flat head screws and alloy steel spacers for assembly.
The rod end based brake master cylinder push rod is in front.

Apply Loctite RC609 to the threads, torque 5/16" screws to 250in/lb.
1/4" screws to 150in/lb.

Set up the double pedal assembly in the BP to drill and tap a hole for lube (Zerk) fitting.

Tap hole 1/4-28 tpi.

Countersink threaded hole entry.


Clean up, prep for primer and paint. Front.

Back side.

Detail of the brake rod end push rod area.

The NAS1005-16 bolt got it's threads shortened to fit as needed:

Prep for primer, paint and finish up next post.


Bernice

 

[lanciahf]

Wow Bernice, nice work. Thanks for sharing

 

[kmead]

Impressive as always. Amazing work.

 

[RobM]

Professional!

 

[Rupunzell]

This home shop stuff creates bills, does not pay the bills ("professional")..


Bernice

Professional!

 

[RyanG]

Bernice - just curious. I’m not a machinist. Why did you braze the pedals and bushing as opposed to welding? Are the materials different? Do you want to be able to disassemble them? Wish I had the tools and ability.

 

[Rupunzell]

Could have gas welded the pedal parts, apply more heat then filler rod making a bead..

Problem with welding, the higher temperatures involved tends to cause differential hardness as they materials cool at different rates. This is not avoidable due to the differences in material thickness-cross sections involved. Brazing preserves most of the strength of this low carbon steel and avoids the differential hardness problem. Having hacked off enough welds on machine tools to know welds have hard and soft spots within the welded area. These hard spots can grow cracks and fractures as the parts involved are cycle loaded. Eventually a welded part like this WILL fail. This is one of THE most common disasters at LeMons, where teams apply the wire MIG welder to "glue" stuff back together then have the "glued" back on part fly off at the worst time.

Welding is one of the most difficult joint making methods due to the complexities involved.. generally not appreciated.

Brazing is more than good enough for a pedal pad. In this case, the brazing bronze was "goooo_ged" on to fill gaps and such as needed.

What is not often appreciated about brazing, it can be stronger than a weld if there is enough stressed surface area and if the joint space is small. Ideally the joint gap for a really strong brazed joint will have a gap of 0.002" or so and plenty of stressed area.

Another advantage of brazing, it is one of the few methods of joining dissimilar metals.

As or tools and ability. Tools are not difficult to obtain. Ability is learned as with many things in life. Having a mentor that was a master model maker machinist decades ago helped lots. And no, do not consider myself a Machinist.


Bernice

Bernice - just curious. I’m not a machinist. Why did you braze the pedals and bushing as opposed to welding? Are the materials different? Do you want to be able to disassemble them? Wish I had the tools and ability.

 

[RyanG]

Thanks for the explanation. Sounds like brazing might be a good skill to develop. And I imagine it doesn’t require a lot of specialized tools, just a good torch setup? The only “brazing” I’d tried is with that aluminum alloy rod stuff and it was for decorative use. Lots to learn here.

 

[kmead]

@Rupunzell Really dumb question, what pedal pad do you intend to use on that? Is that the width of the 124 pedal pad?

With wider pedal surface will you be able to heal and toe properly? Or possibly drag on it as you use the accerator?

 

[Rupunzell]

No such question as a "Dumb" question, there are only questions and possible answers.

Not 124, Saab 9000 since there are many spare pedal pads in the parts pile and they are about the correct size.

Double up the pedal stamping results in the added pedal offset towards the clutch pedal and moves the point of pedal force (foot) towards the clutch pedal reducing the potential side load of the oem Lancia pedal point of force.

Both X1/9 and Scorpiacarlo brake-accelerator pedal distance is set up oem for toe-heel / heel-toe. There is no good reason to alter this as what was originally designed works good. They both have a slight curve at the bottom of the accelerator pedal to further aid in toe-heel / heel-toe. These are often un-noticed design details that are not appreciated.

Few if any modern cars today have brake-accelerator pedal distance this close or set up this way today due to what happened to AUDI 5000's "un-intended acceleration". AUDI got crucified in the public eye for driver's stomping their right foot on the accelerator pedal instead of the brake pedal. AUDI place the pedals this way to aid in toe-heel / heel-toe. Lawyers got their way and the rest is now history.

Hill hold by toe-heel is very doable and effective instead of using the hand brake or_ .
Essentially pedal positions can make BIG differences in the driving experience. Note the adjustable master cylinder push rods, these will be used to put the pedal where they need to be instead of where they end up being by default.

Bernice

@Rupunzell Really dumb question, what pedal pad do you intend to use on that? Is that the width of the 124 pedal pad?

With wider pedal surface will you be able to heal and toe properly? Or possibly drag on it as you use the accerator?

 

[darwoodious]

<technical-talk>

~Note to Forum Admin, the once portrait oriented images have been flipped to landscape orientation with no means to correct this problem. This identical problem has appeared on other forums~

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</technical-talk>