Reverse floor mounted pedal assembly

[LafayetteFSAE]

Hi,
We were thinking of using a reverse floor mounted brake pedal in our car. That means the master cylinder will be infront of the pedal, below the driver's leg. However, only reverse "swing" mounted pedal assembly is sold in the market. do you think it will be feasible to buy a swing mounted one, flip it over and engineer it to work as a reverse floor mounted pedal.

[Luniz]

Why don't you just build the complete pedal assembly by yourself? To me that seems to be a lot easier than converting something from the shelf.

[Daleezer]

We actually did this on our previous car and it worked well. We built the assembly our selves from square aluminum tubing on the pedals and aluminum plate that was waterjet and welded to make our platform and MC mounts. Just make sure you get the platform rigid enough that it doesnt bow like ours did from the break pedal forces applied by the driver. It's really not difficult and would be a lot cheaper to build on your own than buying a set and modifying it. Probably lighter too.

[kapps]

We have been using this style setup for the past 2 years and plan on using it again. Making your own pedal assembly is not hard (my first introduction to FSAE design and Solidworks was designing the braking system for our car). One major advantage is you can shorten the nose of the car by 6".

[TimR]

unted pedal assembly is sold in the market. do you think it will be feasible to buy a swing mounted one, flip it over and engineer it to work as a reverse

It will take more work to reverse engineer something than just to design it yourself. We (Sydney Uni) have something similar in terms of pedal redesigning, the master cylinders used to sit under the drivers feet, but with the template rule there is no space this year. So we have the master cylinders located under the drivers seat (fixed) with an adjustible cable to connect the brake pedal (via a small crank) to the master Cylinders. Much more compact in the drivers area this way, and it allows us to run the pedals pretty much up to the front bulkhead.

[STRETCH]

It also fails to satisfy Formula Student Germany rules, so hope your not planning on entering. How do you control the brake bias using a single cable?

[Luniz]

@stretch: if you aplly the force of the cable to the bias bar and from there to the master cylinders. There you go, brake bias via single cable ;-)

[Bazanaius]

What sort of cable do you use - just a chunky Bowden? How long is it? Just wondering about stretch in the cable when you're applying what is quite a large force. Wouldn't want to be in the way if one of those went twang!
I like the layout idea tho - worth having a look at.

[TimR]

As luniz said we are attaching the cable to a bias bar between the master cylinders to get our bias.
I work part time in a place that makes wire products, so I built it there and tested it. It is about 1.4 m long and I have tested the assembly to destruction (at 1 ton). We are using 1x19 3.2mm stainless wire which was chosen for the lack of stretching. We are expecting the driver to be normally putting about 50-80 kgs on the brake but everything is designed around 150kgs (panic braking)

[MalcolmG]

150kgs? We did some testing by putting one of our corner weight scales against a wall and having people push against it with their left leg, highest recorded was around 240kg without any adrenaline and no impact loading. That was a big guy though, smaller dudes were closer to 140-180kg

[TimR]

adrenaline and no impact loading. That was a big guy though, smaller dudes were closer to 140-180kg

We also did testing but using weights and came up with our 150kgs. We are also basing this on the 08 car's brake working as designed. 240kgs is huge.

[Bazanaius]

240kg is indeed pretty huge. Mark Webber is (I think) well known for having a strong foot, and he sometimes hits 250kg. Admittedly that is under a 'normal' braking incident - dread to think what he gets when he's heading for a wall...

I'd say somewhere around the 2kN mark is a reasonable guess of a scared FSAE driver, for stiffness design purposes at least.

[MalcolmG]

Like I said, this was a reasonably big guy (rugby player) but I don't doubt a panicked driver of reasonable size could manage that too. At the end of the day I'd rather know our brake system wasn't going to fail and take a 150-300g hit on mass of the associated components.

[dazz]

Reading this reminds me of a time years ago when I ran out of brakes appoaching a set of lights of a four lane road after a particularly spirited drive along a twisty road. I was practically standing on the pedal, pulling up on the steering wheel and doing my best to push the pedal through the firewall and into the engine bay. I stopped well over the lines but before the intersecting lanes... just.
A lot of smoke and brake dust then floated out from under the front of the car!

With the added leverage from pulling on the steering wheel, not to mention impending doom, I don't think 250kg would be out of the question, even for your average Joe...

One of those life lessons you're glad you got away with, without anyone getting hurt.

[Adambomb]

Yeah, that is very true. When designing the brake pedal, my first thought is generally "why would anyone stomp the pedal that hard, even in a panic?" Then I imagine how much it would suck if the brake pedal collapsed under your foot...talk about a bad situation getting much much worse!