Chevy Tech: Driver's Seat Ergonomics - Fabrication Sequence

Sucp 1108 Drivers Seat Ergonomics Unfair Takes A Seat 003

The steering column is from ididit, with a tilt column. The most important part of the steering is the hands part: a 13-inch suede MOMO steering wheel tied to the ididit column with an NRG quick-release setup. On the other end of the column are Borgeson stainless steel U-joints and steering shaft that connect to the Tony Woodward rack.

Fabrication Sequence

The DSE dash insert defines the side-to-side location of the steering column, and the first thing to do was see if the Cobra seat would line up well with the column. On the other end, we had to make sure the column would connect to the rack. When the car was at Coast getting its cage, Tim Christ told me that I should roll the rack servo up so that it pointed over the motor mount, rather than under. Doing that meant that I only needed two U-joints instead of four as I had originally planned.

With the column roughly placed and the seat position generally worked out, it was time to tackle the pedals. I used Wilwood's forward-mount pedal kit and took the pedals out of the frame. From there, I added one of their balance-bar setups where the brake pedal used to be. I mounted the pedal frame to the firewall and hung the masters and connected the balance bar. With everything roughly in place, it's time to make all the parts, brackets, and hardware to keep it there but still allow adjustment. Check out how we did all that in the photos that follow.

Most of the time our stories read as if we progress from point to point and never make a mistake. That's not the case. The truth is we make mistakes as often as the next guy; it's just that we don't have to write about them.

These errors can be about not knowing enough to know better, like the floor area you can see in this month's article. Once the headers and exhaust was complete through there, it was obvious we could move the floor, and a few quick minutes sizing up the pedal situation from a prototype seat fit was all it took to get the cutting tools out.

However, there's another almost major error lurking in this story. Compare the seat bracket in the photo above with the final seat bracket photos in the main story. See the difference? The rear bracket was moved back, and it now bolts to the seat tube and not to the rollcage sill tube.

The reason for that change is that I consulted with Joe Marko of HMS Motorsports before making my final welds. Joe is a NASCAR safety consultant who works with the various teams to help them build safe seat mounts and even more importantly, safe harness mounts. Joe took one look at my "hey, look at what I did" photo and immediately took issue with it. He pointed out that the lap belt would have to ride over the top of the rear seat bracket. Belts should never cross over a non-smooth surface because that can lead to small tears that lead to major catastrophes at high speed.

Joe had another problem with my original seat brackets: He pointed out that my original design seemed oriented to supporting the driver's weight. He went on to say that supporting the driver's weight is the easy part--the hard part is keeping the seat in place during a severe accident when the vehicle, seat, and driver experience 12g forces. That usually occurs in a horizontal plane to the driver's weight at rest and is why the rear seat bracket is now oriented to have its most strength in the case of frontal collision, and why all the other seat brackets have a gusset for improved strength. --John Parsons

4 With the steering column mocked up in its centered position, the next thing is to put the brake pedal directly under the column.
4 With the steering column mocked up in its centered position, the next thing is to put t
5 The column/firewall interface is next. Again, keeping the column position at the center of the seat and at 90 degrees to the dash insert, we then find the position where it goes through the firewall.
5 The column/firewall interface is next. Again, keeping the column position at the center
6 A look from the engine side of the firewall. This is the center point of the column where it comes through the firewall.
6 A look from the engine side of the firewall. This is the center point of the column whe

7 After drilling the hole for the column, and passing it through the firewall ...
7 After drilling the hole for the column, and passing it through the firewall ...
8 ... position the steering wheel end with a custom steering wheel positioning tool. It only looks like a jackstand.
8 ... position the steering wheel end with a custom steering wheel positioning tool. It o
9 Bending 1-inch square tube is a snap with JMR Manufacturing’s mechanical bender.
9 Bending 1-inch square tube is a snap with JMR Manufacturing’s mechanical bender.

10 We replace the jackstand with these welded-in brackets that attach to the cowl (like the factory) and the rollcage. This method of hanging the column fixes it in place in all three planes.
10 We replace the jackstand with these welded-in brackets that attach to the cowl (like t
11. With the column fully positioned, it’s time to make seat brackets to put the seat where it was mocked up.
11 . With the column fully positioned, it’s time to make seat brackets to put the seat whe
12 The seat bracket is attached to the rollcage with nominal spacers to hold it at the right height. The reason we attach it to the rollcage is to keep the seat from tearing apart in the event of an accident. It’s better if the seat moves where the rollcage goes in that unfortunate scenario.
12 The seat bracket is attached to the rollcage with nominal spacers to hold it at the ri

13 With the basic frame for the seat worked out, next up is to make some brackets for it. A Sharpie is used to sketch the shape of the front seat bracket.
13 With the basic frame for the seat worked out, next up is to make some brackets for it.
14 The bracket is rough-cut to shape with a bandsaw.
15 A belt sander is used to remove the saw marks and make a smooth radius.
15 A belt sander is used to remove the saw marks and make a smooth radius.

16 It’s a lot easier to work on seat brackets on a bench instead of in the car! So, after carefully marking the seat angle and position (both sideways and forward and backward), the seat is mocked up and the brackets fitted and welded into place.
16 It’s a lot easier to work on seat brackets on a bench instead of in the car! So, after
17 Here’s the seat in its final position. It’s level from side-to-side with a back angle of 20 degrees for the most comfort. The seat is very close to the floor, which was caused by moving the floor up inside the car, plus reserving enough headroom to wear a helmet comfortably.
17 Here’s the seat in its final position. It’s level from side-to-side with a back angle
18 All the brackets and mounts are reinforced. This car is supposed to go 200 mph, and keeping the seat secure is a very important part of driver safety.
18 All the brackets and mounts are reinforced. This car is supposed to go 200 mph, and ke

19 The rear seat bracket goes downward to give as much seat back angle as possible. This is a change from the original design (see sidebar).
19 The rear seat bracket goes downward to give as much seat back angle as possible. This
20 Now it’s time for pedals with the column and seat brackets completed. This is a bit of an awkward angle (it’s taken at about where the rearview mirror will be), but it shows how the brake pedal mount is bolted between the column bracket and the Wilwood master cylinder frame. The rod end hanging down is what attaches to the pedal. The distance between the rod end centers is easy to change and allows for pedal-height adjustment, as do the three small holes in the pedal mount tube. With a fixed seat, pedal-height adjustment is a must.
20 Now it’s time for pedals with the column and seat brackets completed. This is a bit of
21 Another view of the brake pedal mount. The cage passes right through the pedal area, causing a lot of fabrication to work around it.
21 Another view of the brake pedal mount. The cage passes right through the pedal area, c

22 We’re looking at the brake pedal linkage up close. The quick and dirty aluminum adapter block and washers will be replaced with a custom Bryce Baumgart billet piece for the final setup. Also notice how the attachment of the linkage rod was moved slightly (about 5/16 inch). This was necessary to restore Wilwood’s recommended 6.25:1 pedal ratio.
22 We’re looking at the brake pedal linkage up close. The quick and dirty aluminum adapte
23 The clutch pedal hanger attaches to the rollcage tube, to the brake pedal mount, and (behind the cage tube) to the master cylinder frame. You never know when a tube bender will come in handy.
23 The clutch pedal hanger attaches to the rollcage tube, to the brake pedal mount, and (
24 Along with the Lokar throttle pedal and the ididit column, the Wilwood pedals are positioned well for good clutch control and heel-toe downshifting. When the car is more complete, it will be time to do the final pedal fitting for each of the drivers.
24 Along with the Lokar throttle pedal and the ididit column, the Wilwood pedals are posi

25 Here’s how it all turned out on the firewall side. Borgeson steering U-joints and splined intermediate shaft make for an attractive and strong package. The Wilwood remote masters will be easy to reach for the frequent brake bleeding all the track time will require.
25 Here’s how it all turned out on the firewall side. Borgeson steering U-joints and spli

SOURCES
HMS Motorsport www.hmsmotorsport.com	Ididit 610 S. Maumee Street Tecumseh MI 49286 517-424-0577 www.ididit.com
Wilwood Engineering 4700 Calle Bolero Camarillo CA 93012 805-388-1188 www.wilwood.com	Coast Chassis Design: 947 Beville Rd. Daytona Beach FL 32119 386-756-8001 http://www.coastchassis.com
II Much Fabrication Germantown MD www.iimuchfabrication.com	Prodigy Customs Apopka FL 407-832-1752 www.prodigycustoms.com