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 Post subject: Brake pedal Over-travel switch
 Post Posted: Tue Mar 09, 2010 4:41 pm 
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Joined: Tue Oct 06, 2009 4:00 pm
Posts: 38
Location: Florida State University
Hi, There,

In section 3.2.5.2 it mentions: " A brake pedal over-travel switch must be installed, ... in the event of brake system failure..., the switch will be activated and must shut down all drive systems and trip accumulator relays..."

Can anyone provide the P/N and vendor information for this switch ? I suppose all 2009 teams must have one.

Thanks,


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 Post Posted: Tue Mar 09, 2010 7:33 pm 
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Joined: Wed Jun 03, 2009 1:29 am
Posts: 117
Location: Texas A&M
On the Tamu 2009 car we just used a toggle switch mounted to a bracket that would get hit if the brake pedal went all the way down. AFAIK, there isn't a specific switch for this.

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 Post subject:
 Post Posted: Wed Mar 10, 2010 11:01 am 
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Joined: Tue Oct 06, 2009 4:00 pm
Posts: 38
Location: Florida State University
Thank you, Mojave. I suppose that toggle switch should have a big contact area when hit by brake pedal,
do you have a specific P/N for which you used or you just pick an ordinary one?


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 Post Posted: Wed Mar 10, 2010 11:46 pm 
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Joined: Wed Jun 03, 2009 1:29 am
Posts: 117
Location: Texas A&M
julius wrote:
Thank you, Mojave. I suppose that toggle switch should have a big contact area when hit by brake pedal,
do you have a specific P/N for which you used or you just pick an ordinary one?


The one we've always used it just a regular, ordinary toggle switch, available at any parts store or Radio Shack (obviously pick one suitable for the voltage and current load). I think we got ours from Painless Wiring, but I don't have a specific part number.

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 Post subject:
 Post Posted: Sun Mar 14, 2010 8:34 pm 
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Joined: Mon Jun 05, 2006 4:05 pm
Posts: 112
Location: Rules Committee
An ordinary toggle switch isn't ideal. If you use one, you need to make sure the pedal has a positive stop other than the toggle switch. Otherwise, in a real brake failure, you'd smash the switch and it's not clear whether it would do the right thing electrically after being smashed. One of the same big red buttons used elsewhere is a better choice.


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 Post subject:
 Post Posted: Sun Mar 14, 2010 9:32 pm 
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Joined: Wed Jun 03, 2009 1:29 am
Posts: 117
Location: Texas A&M
Charlie wrote:
An ordinary toggle switch isn't ideal. If you use one, you need to make sure the pedal has a positive stop other than the toggle switch. Otherwise, in a real brake failure, you'd smash the switch and it's not clear whether it would do the right thing electrically after being smashed. One of the same big red buttons used elsewhere is a better choice.


Our switch was not a pedal stop. The master cylinders would still bottom out and stop the pedal, but along the way the switch would still get flipped.

Other than a toggle switch, what do you recommend? I don't know of any LV switches load rated for 200+ lbs (the force a driver could exert on the brake pedal).

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- Texas A&M 2009 FH Crew Chief
- 1st place FH '09: 981 pts


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 Post Posted: Sun Mar 14, 2010 10:45 pm 
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Joined: Mon Jun 05, 2006 4:05 pm
Posts: 112
Location: Rules Committee
Sorry, I didn't state that accurately--the use of a more robust switch does not substitute for having a pedal stop (unless you obtain some absurdly sturdy switch, as you pointed out). And I didn't mean to imply that your car or any particular car used a toggle switch as a pedal stop.

The issue is really that if the pedal stop has some give to it--say 10 mm--and the switch travel is 5 mm, then the switch could get trashed. So it's really more about making sure that the switch has enough travel that it won't accidentally become a pedal stop than it is about using a mechanically sturdy switch.

Thanks for pointing out that what I first said didn't really make sense.


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