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I am laying out my chassis, trying determine the overall wheelbase. After looking at my chassis compared to other cars, I feel like the cockpit is too long. I also realize that most cars angle the bottom chassis tubes inward near the pedals. That would give me more room around the front wheel, and make the cockpit area more compact. However, I want to make sure I leave enough room for the pedals. I am looking for the dimension from the back of the seat to the brake pedal. I am about 5'8", so if you could tell me about how tall you are as well, that would help. I have the seat, but it's at home while I am on a several week long trip. I appreciate the help. Here are some pics of what I have so far.

Ken

i see you're using nx!!! what's the dimensions from your floor to the top of your roll hoop?

here's a length of my cockpit that i've got worked out... it's about 58" bar to bar, to the pedals it's only 50", from the butt of the driver to the pedals is 37.5"

More correctly, I am trying to use NX. I took a 3 month community college class, but we didn't cover many of the things I am trying to do, so the going is slow. Since those pics were taken, I have made the whole cockpit area smaller. See the pic below. The height of the roll bar is 43". The seat space savers are based on the actual Kirkey seat I bought. I also took a picture of me seating in the seat to get an idea of how high my head is in relation to the top of the seat. I think this should be enough room.

Thanks for the reply by the way. Can you tell me more about your driver? Is that something you designed, or did you find it somewhere? How tall is your driver?

Thanks
Ken

PS. It looks like you are a better UG user.

I was lookng for something like this for you but google images hasnt been kind to me today.

_________________
I'll keep an eye out for you!

To err is human...
I am more human than most.

Thanks for looking. I used an ergonomic program in college that generated 3D bodies, but I haven't found anything like it since. I think I am going to have a more upright seating position. Here is a pic of my Kirkey seat:



Thanks again.
Ken

Ken, I've been using NX for about 3 years in college... We use it to design a lot of stuff for the SAE Baja team that I'm on.

Anyway, my driver is a copy of the solidworks model from dennis of DP cars, I've altered it to fit my dimensions and changed the seat back angle. I'm going for a seatback angle of about 40 deg. cause it lets me have a super low rollbar height considering I'm 6' tall..

Here's a pic of the nx model with the driver standing upright...

I too am using kirkey's with a similar layback. You can mount them like you have it pictured (bottom parallel with the ground) but they won't be too comfortable. To see what I mean, just sit down in that seat with it flat on the floor like that and move your legs as if you were working the pedals. Not easy eh? Those seats have to be mounted up a few inches off the floor and or leaned further back to be comfortable IMO. You might not end up in as upright of a position as you think.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

After reading the replies, I decided to follow the suggestions and angle the seat. I will have to try it when I get home. I will also have to buy the cover, so I know exactly how it will feel. I will also probably buy the brake pedal and master cylinder, so I know where to put the pedal and how much room the cylinder will take up. Maybe, I can just find some drawings for the master cylinder so I don't have to do all the brake calculations yet (don't want to buy more master cylinders than I need).

When I started changing the model, all of the old mistakes I made in UG came back to get me. I decided to make a completely new assembly. Here is a shot of the new assy with the seat positioned with the bottom 8 degrees to the floor. What do you think? Does anyone have a measurement for how much their seat is angled? It lowers the rollbar height, but make the chassis longer, which is exactly where I don't need the extra length. Oh well, I would rather be comfortable.

sodamninsane,
Those models look pretty nice. How did you decide on the final seating position? It looks like your legs will be pretty close to the steering wheel. Any worries about that?

you're right about the angled seat making the chassis longer... added like 10" to my wheel base

I'm a little worried about the actual seating position as it is, I'm not exactly sure how accurate the model of the person is, I mean all the dimensions are right, but it seems a little big... so I'm just going to make a chassis mockup and sit in it and see how it feels... lot of stuff in that model is going to change once I start building... which won't be for quite some time...

As for the steering wheel, I'm not so concerned... the major concern for me right now is the packaging of the gas tank up front and how well it's actually going to fit... but like I said, chassis mockup...

i higly recomend building a mockup. it will tell you many things that CAD cannot, or i cannot make it do, i think more the later. i built mine from MDF, its since been dissasembled but it told me mostly what i wanted to know. the main issue for my build was the steering, i needed to know that i could place the wheel where i wanted it and ther would be no binding in the ujoints. i originally thought the placement of the brake pedal was going to be correct, i ended up moving it about 4 inches or so back and a few towards the centerline. this also told me that my clutch master cyl. would need to be operated via a torque tube that would be placed under the steering column. as for the ergonomics, i found that i needed a fairly reclined seating position with lots of support under my knees, but i intended on making my own seat anyway, it just tod me the direction i needed to go. the mockup is not exact, the cross bracing was moved upward to accomodate my knees and feet. i also found out that my "tub" was too short by about 3 inches, no big deal. in the end the lenght from the pedal to the firewall is about 45", about 37 from the pedal to my butt, and the total lenght of the tub is 57... mmmm sounds familliar, coincidence. i found my set up to be comfortable for myself, im 5'10 and 190lbs BTW. and yes i DID make car noises when i was sitting in it.

Andrew

I fully intend to make a mockup, but right now I am on an extended stay in Europe. That makes getting to the garage a little tough. I am keeping myseld busy on the weekend playing with the model. Once I decided to go with the C5 trans/diff combo, I really wanted to see what the wheelbase was going to be. From what I have done so far, it looks like the wheelbase will not be too bad. Once I get home, my plan is to make a build table and start putting the pieces in place. As I move forward, it will be a combination of the CAD model and the mockup.

When you were doing your mockup, what did you think of the floor mount pedal? I was originally going to go that way, but that's another 4-5 inches of wheelbase. Looks like firewall mount for me now.

Ken

Iniitially i was thinking it wasnt going to be comfortable. but after adjusting the pushrods so the pedal stood almost vertical it was feeling pretty good, my heel is pretty much resting on the base of the pedal. i had a good look on gurneyflap.com at sports proto and they all had pedals that were mainly upright as opposed to being further back on there arc. when the pedal is fully depressed, my feet are still behind the front wheel centerline by an inch or so. if i did not build a raised footbox, i would be able to get my feet further fwd and further under the sterring components, that would necessitaed overhung pedals. in the end i decided on the configuration you see for packaging reasons with other components. if my feet were going to below my ass then i see how overhead pedals are going to more comfortable. but for my config im happy.