Monte# 209, Clutch pedal mod & push rod mod.

[Rupunzell]

Noted from a member on MonteCarlo Consortium regarding the brake and pedal problems with the design in the ScorpiaCarlo, decided to modify the clutch pedal first while waiting for a second brake pedal to arrive.

Make an adjustable length clutch master push rod using a M8 grade 12.9 socket head cap screw.

Cut the socket head off to match the screw diameter of 0.311" ( 8mm = 0.315" but these are real world parts with variations).

Cut the 4mm radius using a corner rounding end mill.. cutting tool is a cutting tool when properly applied.

The threaded end of the push rod was trimmed to length and faced flat with a
60 degree chamfer to match the start threads.

Modify the IKO (japan, bronze liner, chrome steel ball with lube fitting)
M8 rod ends as the OEM 14mm wrenching flats are too
large to fit into the bore of the master cylinder at the far end of the pedal travel.
The 14mm wrenching flats became 12mm wrenching flats to match the body
diameter of the M8 rod end.

12mm hex done.

Cut off the OEM pins for both the clutch spring and clutch master push rod.
Carbide slitting saw does good for this.

Drill tap the clutch spring boss for 5/16"-24, this will be used for a sleeve bearing
set up in place of the OEM grooved post.. which was about to die. Yes, the hole
was "power tapped". VFD on the BP and helical tap makes this easy.

Initial idea was to use the rivered clutch push rod pin modified.. Did not work,
the pin got removed and a 0.399" OD sleeve was made as the proper fix. Ended
up making a slight pocket with radius corners to help with clearance between the
clutch pedal adjustable M8 rod end to pedal as there was just enough clearance
between the modifications and pedal box edge.

What the modified parts look like. The 10mm hex on the push rod is a M6 set nut.
drilled to press fit on the 0.311" dia modified cap screw plus RC609 Loctite. Should
be adjustment only torque. The nut was a 1/4"-28 jam nut drilled and threaded to M8.
this is essentially a small pattern jam nut tap that is not made commercially. Done to
gain clearance with the largest parts possible for increase rigidity and strength.

OEM push rod and modified push rod.

The modified clutch pedal with adjustable master cylinder push rod mocked up.
Variable length push rod allows clutch pedal position adjustment as needed.

Bit more paint prep on the clutch pedal and it is ready for paint.

~Possible this process modification could work on the exxe clutch & brake pedal.


Bernice

 

[Yves]

Bernice,
I like your thoroughness,

Best Regards
Yves

 

[RobM]

Any thoughts why the Scorpicarlo has an oversized clutch pedal return spring? The X pedal's spring isn't so heavy duty, right? All we're trying to do here is keep the pedal from riding on the throwout bearing.

 

[Rupunzell]

Spring rate of the X and Scorpiacarlo are similar, difference being the clutch spring in the X has a over center feature to alter the clutch engage-disengage pedal feel.

Real race cars have little if any clutch pedal return spring force.. They often have just enough pedal return spring to aid the pedal return and not a lot more.

BTW, next post on the Scorpiacarlo pedal box is improving the brake pedal.. which is flexi due to the bend. The bend was believe to be ok due to the vacuum assisted front brakes lowering brake pedal force.. This was just wrong from the beginning in many ways. This is one of the list of items that resulted in lesser and in ways horrid brakes in the Series One Scorpiacarlo. The bent brake pedal also produces significant side loading of the bearing causing it to wear out in ways the X pedal bearing never will.

Or why the X has much better brakes than the Scorpiacarlo as delivered.


Bernice

Any thoughts why the Scorpicarlo has an oversized clutch pedal return spring? The X pedal's spring isn't so heavy duty, right? All we're trying to do here is keep the pedal from riding on the throwout bearing.

 

[RobM]

Thanks Bernice. Enjoying your posts on this subject. PS, are you a machinist? Who's carbide inserts are you using? I work for Sandvik Coromant.

 

[Rupunzell]

Iscar, Sandvik, Kyocera, Seco. Most often used on the lathe would be CNMG432, grade varies depending on the material being diced up.

Mill varies depending on what needs to be done.

Experimented with made in China carbide inserts, these have been a disaster so far. If the machine tool has enough rigidity and power is quite remarkable how much material can be removed in short time. More remarkable, given the horrendous stress these inserts endure, they survive remarkably well.

Cobalt high speed cutting tools are also used when specific needs points to a special cutting will do a better job.

All this is done in the small machine shop in garage. One J head bridgeport mill and a 12" x 24" lathe (too small, and more) that is planned for upgrade at some point to a Mori Seiki MS850 or it's South Korean licensed clone. And a pile of tooling which allows stuff to get did.

Not a machinist, but learned how to do this decades ago from the master model maker that made prototypes at a company in the past.

Curious about your take on carbide inserts and related.


Bernice

Thanks Bernice. Enjoying your posts on this subject. PS, are you a machinist? Who's carbide inserts are you using? I work for Sandvik Coromant.

 

[RobM]

Thanks for the bio. I've been with Sandvik 39 years; retiring in April. Always been on the admin side, but I admire the product. Not sure what you mean by my take on carbide inserts, but ... it's ancient technology. I thought 20 years ago that something would replace it, but it is still the best way for metal removal. Additive manufacturing seems to be the future, or at least some combo of additive and subtractive. Sandvik is trying to figure out the best combination of techniques for manufacturing. Naturally, I've consumed the KoolAid and think we make the best tools (most expensive, too). Truth be told, Kenna / Iscar / Sandvik / Seco are all top shelf. Some may hold an advantage on specific applications. Until someone has a technological breakthrough, the difference going forward will be in service.