Alternative Dash Instrument Retention

Seymour Snerd

Lifetime Supporter
I needed to remove and replace the oil pressure gauge and tachometer from my SPF dashboard. They were retained by the usual u-shaped bracket and thumb-nut(s), but since the dash was assembled and then mounted to the car, removal was difficult and replacement nearly impossible. Therefore, I needed a new way to retain the instruments that is more "service friendly".
I solved the problem by attaching a relatively stiff coil spring to the rear of each instrument and a steel cable to that, which when fed through a 1/8" hole in the frame behind the instrument can be terminated to the frame under tension.
See pictures below for how each instrument was attached to the cable, and how the cable was attached to the frame. The cable anchor point will be covered by carpet. The materials I used were:

  • 1/32" Type 304 Stainless Steel Wire Rope, McMaster 3461T188 $6.50 for 50 feet.
  • Zinc-Plated Copper Oval Compression Sleeve for making loops in the cable: Mcmaster 3898T29 $2.12 for 50.
  • Single Diameter Compression Tool for crimping above sleeves: Mcmaster 3377T23 $40.73
  • Music Wire Ultra-Precision Extension Spring McMaster 9044K53 $8.18 for three.
  • M4-0.7 locknuts and washers to fasten wire loops to instrument studs.
tach retention.jpg oil pressure gauge retention.jpg instrument retention cables.jpg instrument retention.jpg
Each instrument can now easily be removed by the detaching the forward end of the cable from the anchoring screw and pulling the instrument out. The cable should be relatively long (eg 12") to provide adequate service loop so the rear of the instrument can be accessed without completely removing the cable. This also makes locating the anchoring screw easy. If the instrument is to be removed completely it is best to detach the cable from the instrument since that is easier to do than re-routing the cable.

I located the anchoring screw first and then formed the forward loop in the cables such that the cables would be mildly tensioned when looped over the screw. The anchoring screw is deliberately shown partially tightened, and the cables are shown prior to removing excess cable beyond the sleeves. The 1/32" cable breaking strength is over 100 lbs.

The 1/8" holes in the frame behind the instrument need to be located close to the instrument's and dash hole's centerline to assure the instrument sits flat in its hole. This means the drill will not be perpendicular to the sheet metal, so center punching is called for.
 
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Seymour Snerd

Lifetime Supporter
One minor improvement: installed a 4mm rivnut at the anchor location, and used a ~25 mm long socket head screw to anchor the cables. This type of screw allows you to use an allen key to lever the cable loops into position before threading and tighetening the screw.
 

Terry Oxandale

Skinny Man
Great post Alan,

These U-brackets have been one of my primary reasons for turning away from a particular set of instruments (I've not yet made this purchase). I've never considered them a very good means of installing the gauge, and have focused on the types that use a ring-clamp that screws onto the front, outside lip of the gauge, as a must-have criterion. Anyway, your solution is so appealing, I may instead weld a crossbar behind the panel, and then spring-load these types of gauges.
 

Seymour Snerd

Lifetime Supporter
I've never considered them a very good means of installing the gauge, and have focused on the types that use a ring-clamp that screws onto the front, outside lip of the gauge, as a must-have criterion. Anyway, your solution is so appealing, I may instead weld a crossbar behind the panel, and then spring-load these types of gauges.

I've ever seen gauges that use ring nuts from the front; that sounds ideal. Are they common?

The crossbar idea sounds great and much cleaner than drilling holes and running cable all over the place, although in the Superformance there's no room. You could make a vertical hole in the cross bar and attach the cable with a hook.

A cleaner and more elegant way to do this with an existing gauge would be to add two or three ~1/16" sheet metal bayonet ears to the instrument case (epoxied or riveted, I guess) and then notch the dash to take them. If I had nothing better to do I would try that but chickened out of cutting into my precious dash.
 
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