Sunday, August 10, 2014

Seeking Legroom

To what lengths will early bird owners go in order to get reasonable legroom?

As I mentioned in a previous post, these cars are rather infamous for their 'foreshortened' cockpit.  Most people 6ft or taller complain about the lack of adequate legroom, especially on the driver side.  The overly large steering wheel and the pedal placement combine to seriously degrade comfort for drivers of greater than average height and girth!  My XL son can get in the car and drive it, but the awkward right leg position causes his foot to go numb in about 20 minutes!

Why did Ford design a car with such short legroom?  Were people shorter in the '50's?  Was the t-bird intended, as often stated by Corvette owners, as a "woman's car"?  I suspect that the real answer has to do with the combined complexity of the power seat and the convertible top.

The power seat was clearly a marketing imperative, cementing the image of the Thunderbird as a 'personal luxury car', but  designing the power mechanism for such a low seat was quite an engineering challenge!  So much so that the designers may not have had time to finish the design of the lower-cost manual seat adjuster... manual seats weren't available until the 1956 model year!   The raise/lower seat mechanism requires a crossbar and motor mechanism immediately behind the seat, limiting how far back the seat rails can be placed.  Here's a pic of the bottom of the seat removd from the car.  The front of the seat is on the bottom, and the motors have been disconnected.


The hideaway soft top was also quite an engineering challenge.  I've helped a fellow club member put  his top up in the rain, and later stow it.  First we had to undo all the latches, release the toggles, unzip the rear window, carefully fold the top flat on the rear deck, then rotate it up vertical on the spring-loaded 'swing-arm' and carefully drop it down into its stowage location behind the seat.  It definitely takes two people to do this safely, and in the right order... on pain of damaging something.  The seat must be adjusted fully forward on the rails before the top can be swung down behind the seat.  And, of course, the rearward motion of the seat must be limited or it might also damage the convertible top when stowed.

Since Nell doesn't have a soft top, I am really not concerned about maintaining room for one behind the seat.  I have been eager to improve the legroom situation on this car for years, and have been looking for a complete manual seat adjustment mechanism from a '56 or '57 that might allow greater rearward motion than the power mechanism.   Since these have turned out to be very scarce and pricy, I finally came to realize that the only reasonable approach is to fabricate new, non-adjustable seat brackets that would completely replace the power seat mechanism.  Since these brackets would be designed as "drop-in" replacements for the original mechanism, the car could easily be returned to stock.

Well, at the last Harbor Freight sale, I picked up an inexpensive flux-wire welder.  I've been wanting to refresh my high school welding skills anyway.  Another trip to the local industrial metal supply house for two 2" x 1/8" bars and some 1" square tubing, a free weekend, and I'm ready to start this project!

First I remove the seat (with some help), flip it over and measure the relationship between the floor mounting studs and the seat.

With the seat all the way back, the floor mounting stud is 4" from the front edge of the seat.
Removing the the mechanism from the seat, we placed the seat back in the car to determine just how far back we can reasonably expect to move the seat.  The determining factor in how far back the seat can move is the garnish rail at the rear of the cockpit. It is covered in vinyl, but it is not padded and definitely uncomfortable to lean against!

Original position... front of the seat was 27 1/2" from the rear fender.
We slide the seat as far back as we can, positioning the seatback just under the rear garnish rail  & making sure this is still comfortable.  This is really as far back as the seat can go!
The seat has been moved 2" back from its original position.
Move the seat rearward by exactly 2"... that is a very concrete and achievable goal!  By measuring the  seat mechanism, I determine that this requires the front seat mounting hole to be even with the front floor mounting stud, and keeping it 2" to the outside and 1 1/4" above the floor rail.

I start by fabricating replacement floor rails (2" wide, just like the originals) out of the 1/8" steel stock.
All bending is done with a heavy bench vise and a sledge hammer.
Final shape.
Drilled for bolts and checked for fit.
also the driver's side
Front bolt tack welded
Welding a 1" section of square tubing, enclosing the bolt.  My welding skills improved significantly throughout this project!
Tack welding the rear seat bracket, based on measurements from the power seat mechanism and test fitting on the seat.  
The floor studs need to be 41" apart (outside dimension), same for front and back.  The diagonal measurements between the studs need to be as close to identical as possible... mine were just under 46".  Once everything was aligned and square, we put the seat in the car for a test fit.  It neatly dropped in place the first time, and fit beautifully!  We then removed the seat, removed the brackets, and painted them.

Painted with hammer tone silver Rustoleum.  Note the elongated holes on the driver's side... this was necessary in order to get the diagonal measurements to match, and the brackets to fit.
Finished brackets in position!  Note how the front studs are now about 2" from the front of the seat.  We have achieved the goal of moving the seat 2" rearward!
Side view, showing how low the seat will be.   
I ended up putting a stack of fender washers above the front of the bracket when bolting it up,  which raised the front of the seat a little.  I would have been better off using a 1 1/2" section of square tubing in the front, instead of 1".

I did some electrical work under the dash while the seat was out: installed a dual zone preamp/equalizer for the stereo, and 4-way flashers... but I'll talk about that in another post.  We re-installed the seat yesterday and took a little drive.  I find the increased legroom to be more comfortable, but my 6 foot son finds it essential for safe driving.  I'm hoping that his right foot won't be going to sleep during our next long drive!

4 comments:

  1. Any thought about selling these. I could really use the room in my 55.

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  2. Not planning on it, Weary. It was a fun weekend project that matched my modest welding skills, but I really don't want to invest in the jigs & tooling to build these repeatedly. Also, these were custom fit to the seat and to the car. I wouldn't be comfortable selling something that the customer that might not fit.

    That said, I'd be willing to walk someone through this project if they brought their car over to my house!

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  3. I hope this technique plus a small diameter steering wheel will give both of talk some enough leg room.

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  4. My 56 came with manual seats but it is still a problem. I redrilled the floor pan and moved the seat runners back about 2" then shimmed up the front of the runners about 1". This has helped a lot but I am concerned about a back injury if we ever get rear ended because the seat is against the rear of the cockpit. The steering wheel makes it hard to get into but that inconvenience is worth the comfort advantage.

    ReplyDelete

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