When you've been driving 50 years and more, you develop a certain set of reflexes, covering all aspects of vehicle operations. For me, one of those reflexes is that one sounds the horn by pressing the center of the steering wheel. If you're driving a 1952 MG TD, that's a problem! MG thought it was just fine to put the button (which is apparently called the "Horn Push" in all cars, not just MGs) on the center dash. Here's a web photo showing that horn push:
Admittedly, that's a pretty big target, and since it sticks out farther than anything else on the dash, it's pretty easy to hit. Early on, I added some LOUD Hella horns, because one of the stock TD horns was missing, and the other made a bleat like a wounded animal. Later, in Part 46, I redesigned the dash so that I could have more gauges, and added a horn push that was smaller but still easy to find. But... in the few times when I genuinely needed to sound the horn as a warning, that reflex kicked in and I pounded the center of the steering wheel, resulting in nothing at all!
Much later, in Part 73, I installed a beautiful new wood rim steering wheel, and to my surprise, the wheel came with a horn push - just a button with spade connectors on the back side to attach wiring. The steering wheel is a clone of the Motolita wheel, and that 9-hole mounting pattern is a standard of sorts. It's easy to buy a horn push if you have the Motolita wheel but no center.
The TD was missing the all-important wiring for the horn, however. That involves something called a "slip ring" that makes the electrical connection no matter how the wheel is turned, and that bit is hard to add if it's not there. But I did notice that underneath the horn push, there was a pretty good recess. Was that a possibility?
I went looking for some sort of RF module that was designed to make a momentary connection from a distance, and I found an eBay vendor called msd-inc that had a bunch of them. This one, model RM11, seemed the sweet spot to me, a momentary switch that had two small transmitters. A bargain at less than $20 shipped.
It turned out to be really fortunate that there were two remotes, because on the first one I tried to remove the switch. The traces on that circuit board are as thin as spider webs, and lifting the switch ruined them. On the second try, I tacked my wires directly on the lugs on the switch and that worked fine. The other end of each wire was soldered to the lugs on the back of the steering wheel's horn push. Thus, pressing the horn push activates the remote, just as pressing the button on the remote did.
I had hoped to leave the module in the switch case, but there wasn't quite enough room, so I wrapped the circuit board in bubble wrap (small bubbles) and it then fit below the horn push. Time for a test. Here's the receiver module on the bench, powered by a 12V bench power supply, illuminating an LED when I push the horn push in the car. This is going to work!
Right away, I started looking for the right MG emblem to finish off that horn push, and another eBay vendor, CruisingDaytona, had the right 1" domed emblem with PSA adhesive, $16 for three. That felt pricey, but I wasn't going to stop now!
One more side trip. What was I going to do with the horn push in the dash, now that the loud horns were sounded from the steering wheel? I bought a very cheap motorcycle horn on Amazon ($8) and mounted it under the front apron. That allows me to give a jaunty, and not too loud, beep-beep salute to folks yelling and waving as I drive by in Beck TD. It happens nearly every time I'm out in the car. You can see the red Hella horns hiding under there as well.
The last step was attaching the receiver module under the dash. Fortunately, it is small, lightweight, and easy to wire.
One reason the wiring was easy was the relay module I added during the Grand Rewiring in Part 46. There was a spare relay that I used to hook up the new beep-beep horn. Moving the "big" horns to the receiver module was as simple as moving the trigger wire over by one, and adding the new trigger from the receiver.
It all worked great! Here's a little video that demonstrates the two horns. I've already been able to give the "beep-beep" salute to a group of road workers that were yelling and waving. And while I hope the urgent use of the loud Hella horns is very rare, at least now I'll find the horn in the steering wheel when I'm responding by reflex!
Love that solution. I think those small RF modules could be useful for quite a few projects where running wires just isn't feasible or easily done.
ReplyDeleteLooks good!
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