A Handbrake Under The Dashboard
by: John Hardy
from: Fortification - January 1997

Fortification is the Club Magazine of the GT40 Enthusiasts Club
Copyright: GT40 Enthusiasts Club 1997

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A Handbrake Under The Dashboard

The original Mk 1 GT40s kept their handbrakes in about the same location as the glovebox on most cars: under the left hand side of the dashboard. The "tunnel" between the seats had a curved top, much like the transmission tunnel in older rear drive cars, but narrower. By contrast, most replicas have a flat-topped tunnel with the handbrake sitting on top of it in the conventional position between the seats.
Although I am not fanatical about originality, I wanted my car to be a reasonable replica in the cockpit. I also just liked the arrangement in the original cars. So the handbrake had to go under the dash. This was not a trivial job for two reasons. Firstly, the handbrake mounting has to take high loads. The driver may heave on the lever, and the mechanism gives a lot of mechanical advantage, so loads in the structure around the handbrake could easily reach 500 or 1000 lbs. Secondly, the linkage would have to go around three corners before it had a straight pull on the handbrake cables coming through the firewall.


I decided to use an open cable running over pulleys. The first job was to fabricate a subfrarne which would hold the handbrake in the correct location and provide mounting points for the pulleys. I had bought a cheap(ish) MIG welder and taught myself to use it. I was confident enough to weld up a subframe, but I did not want to start welding things to my precious chassis: so the subframe would have to bolt in without having to drill big holes in the chassis (and thus weakening it).
The basic shape of the subframe is shown in the photographs. The location is quite critical (low enough to clear the dash without scraping your knuckles, but high enough to clear the passenger's knees and keep the subframe hidden from view), so make a mock-up from scrap wood and masking tape, and check it with the dash moulding in place.


When you get to the metal, measure twice and cut once. I used 1" square steel box section. The plan was to run the handbrake cable down the centre of the box sections, so that all the serious loads would be taken by the subframe members in compression, so I made cut-outs for pulleys etc. before finally welding up.
The handbrake itself was from a Triumph Herald. There was nothing special about this choice, but it was about the right size and looked the part (1960s not 1950s chrome or 1980s Cortina). No doubt someone in the Club knows where the handbrake on the original cars came from. The mounting brackets were made up from angle iron welded and bolted to the subframe. The all-important pulleys were a problem. They had to be large diameter (to avoid damaging the cable by continually forcing it around a tight radius), and they had to be strong enough to cope with the loads, and durable enough to go on coping year in and year out.
I eventually used pulleys from the flap system of a light aircraft. Smaller Cessnas and Pipers use cables for both the main flight controls and the flaps, but the flap cables are larger at 1/8" diameter. In some light aircraft (e.g. Cessna 180 or 185), the flap system is operated in much the same way as a handbrake, by heaving on a socking great lever. Good second hand flap pulleys are sometimes available from aircraft that have been written off. a friend in the industry managed to find me three without robbing his employees stock.
No doubt they would be available new, but I have no idea of price. The pulleys were mounted on brackets running across the corners of the subframe (see drawing):


The only other critical item was the subframe mounting next to the last pulley at the bottom of the front bulkhead where the handbrake cable emerged to run back to the rear bulkhead. At this point, the tension on the handbrake cable would be doing it's best to tear the subframe out. The Tornado chassis has a substantial steel plate welded in here (supporting the driver and front passenger's heels). A lug was welded to the foot of the subframe, and this lug was bolted to the steel plate.
The subframe was later modified so that it doubled as a servo mount and tripled as a heater mount, painted and installed. The finished job (cable by Speedy cables) seems to work well, but the jury is still out on it as the car has not been MOT'd, and only time will tell whether the whole set-up will hold up under the years of use.
If I were doing it again, I might experiment with bell-cranks, rods and rod-end bearings (Rose joints) instead of the pulleys. I might also re-examine the idea of putting the servos under the dash. It's a neat installation, but access is difficult and it may become a maintenance problem.

John Hardy

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