[DeTomaso] Clutch master cyl

Joseph F. Byrd, Jr. byrdjf at embarqmail.com
Sun Jul 1 19:11:06 EDT 2018


I found this online photo where a member here had posted.

That decade ago, I noticed the arrangement was a classic mechanical model of a "four bar link with slider crank".  (a typical 1st year MAE homework)  So I took measurements, wrote the equations and solved for displacement/force in versus out.

In summary, the original pedal had a 5:1 ratio, the linkage increases the mechanical advantage at full pedal down to 7:1, thus making it easier to hold down and let off.  But with an increase in mechanical advantage comes the lost in cylinder stroke, so to compensate, the linkage reduces the mechanical advantage at the initial pushing down.

A key point to note, 
if the initial angle of the links is excessive, you lose that initial increased travel and resulting in loss of slave stroke.  If the initial angle is too shallow, the initial force to press the pedal can become excessive, damaging the pins at least and locking up the pedal at worse.

Now, the rest of the story...
A couple years ago, someone told me the bell crank in my math was "backwards".  Thus my thought was, no problem, I'll redo the math and see how much it really matters.   BANG...It hit me hard, I have forgotten how :(
   




-----Original Message-----
From: DeTomaso [mailto:detomaso-bounces at server.detomasolist.com] On Behalf Of Mike Drew via DeTomaso
Sent: Sunday, July 01, 2018 17:56 PM
To: Don Franck
Cc: detomaso at server.detomasolist.com; Admin at detomasoregistry.org; SCPOCA at yahoogroups.com
Subject: Re: [DeTomaso] Clutch master cyl

Don,
....
The piece is nit symmetrical and has a right and wrong orientation. Hopefully you paid attention when you took it out and will install the new one properly. 

I have a diagram at home that shows the proper orientation.....

Mike

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