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Engineering a horn bracket

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  • Engineering a horn bracket

    I need to make a horn bracket for a motorcycle. Seems like a simple job but, as with most things, there are complications. This bracket will be placed in a high vibration environment (no other place to put it). The bracket must be "L" shaped & the long leg about 3" long, 1" wide. The bottom leg of the "L" is about 1" long by 1" wide. The horn is a typical auto horn weighing about a pound and attaches to the long leg of the bracket. The issue is that the long leg of the bracket must be somewhat flexible to allow the horn to work properly. Horns mounted on thick, rigid brackets don't resonate therefore the sound is diminished greatly. My original bracket worked well for sound but didn't have much longevity having eventually broken at the bend due to metal fatigue. I had hoped to prevent this by installing a spring from the top of the bracket to a fixed point to reduce vibration movement that would cause this fatigue. It didn't work, although it may have lengthened the time it took for the fatigue to take place to the point of failure.
    I am now considering a new bracket made of two pieces, a thick angle (1/8") as the base of the "L" and a thin (1/16") "extension" piece as the longer leg of the "L", joined by either weld or rivets to the angle to form the long leg. My hope is that the thicker angle will resist the metal fatigue at it's bend. My concern is that the new bracket may break at the joint. I am inclined to use rivets to make the joint as I believe they may be more resistant to vibration than a weld. Any personal experiences or thoughts of engineers would be helpful.
    Thanks, Steve

  • #2
    Make the bracket rigid and rubber mount the horn. Or bend up a thin bracket looped over a tube and isolated from the tube with some inner tube.

    Mine hangs down from the top tube below the front of the tank and is mounted using the second method. It's not intrusive, it's tucked away, it's thin enough not to impede air flow over the head and it's out of the rain and it can be heard.

    Never use it though. If I've got time to use it, I don't need to use it. You should certainly not be using it enough to fatigue the bracket.
    Richard - SW London, UK, EU.


    • #3
      That's what make this site great! Your thoughts have given me an idea. Muffler hangers have a rigid rubber piece that I can attach to an angle. I mount the horn to the rubber and it should work. Maybe a piece of truck mud flap would work as well. In my case the horn must stick up not hang down but if the rubber is rigid enough it could work. Gotta look into that

      Not sure how it is where you live, here in South Florida roads are crowded and drivers are on their cell phones or have their heads where the sun don't shine most of the time. We are rated worst drivers in the U.S., I think. Options for evasive action are limited at times due to crowded roads but I try to always leave myself a way out when I ride. Although I seldom use the horn, sometimes a horn and evasive action together make the difference.

      Thank you for your response, it'll be interesting to see what other say as well.
      Last edited by firbikrhd1; 04-20-2011, 02:49 PM.


      • #4
        I wouldn't mount the horn facing up. You'll just blast yourself off the seat! If you want folks in front of you to hear it, mount it facing forward. It's been a while since I owned it but I think the horn on my GW-Interstate was mounted between the forks under the tree. It was loud even then.

        If nothing else, have this ride in front of the pack. NOBODY will miss you!


        • #5
          Don't forget to add a grounding wire if you rubber mount the horn. Some horns have only one push on electrical wire tab with the body of the horn being grounded, others have two wire tabs so grounding for them is not needed.

          Maybe adding an external brace will reduce the chance of breaking the horn mount is about all that's needed here.


          • #6
            It used to be fairly common to mount horns of this sort on a laminated bracket made of two or three thinner leaves bolted together at the ends. For an L bracket you might have to make it of two pieces, one thick for the L and then a multi-leaf extension.


            • #7
              Yep, that will work, they will watch her and run over every body else.
              It's only ink and paper


              • #8
                Something like this,



                • #9
                  My bike also uses a laminated bracket--be sure to aim the horn forward and mount it so it is unobstructed, soundwise.
                  I made the mistake of mounting mine up in the fairing and they can't be heard very well.
                  There are a few good horns that don't weigh as much as auto horns, like the one here, not necessarily from that company, but it shows what is out there.



                  • #10
                    There have been some good options already given.
                    This may be another idea that I have seen often used in high vibration locations....a steel spring of suitable size, flexible yet strong.

                    I'm afraid that if you were to use CCWKen's idea you probably won't make it out of the least I wouldn't.
                    Home, down in the valley behind the Red Angus
                    Bad Decisions Make Good Stories​

                    Location: British Columbia


                    • #11
                      I don't know if it's been mentioned yet, but about bending up a bracket- you can bend cold or use heat to soften the metal where the bend is to be. Off the top of my block, it would seem that a hot bend would be less apt to fatigue-

                      Also, someone has alluded to the possibility that the operation of the horn is what's causing the bracket to break. Maybe that's just a tad too much use of the horn-
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                      • #12
                        Thanks to all who have responded with ideas. Truthfully I like CCWKen's the best, but I don't think I could afford her, but I sure do like the view!
                        You all got me thinking about solutions and I finally came up with this:

                        The "bell" of the horn will face either down or to the side as the mounting place is under the bike in front of the rear wheel with the bracket in the position shown. The rubber piece is a stiff piece of a mud flap I had on hand. It is stiff enough that it will support the horn easily while allowing flex without harm. As a test I attached the horn to is first and clamped the rubber in the vise, put 12 volts to it and nearly deafened myself. No worries about blowing myself off the seat or water retention for that matter. I do believe this will solve the problem, time will tell.

                        Thanks again all, sometimes it just takes a little conversation with other intelligent people to get the creative juices flowing.
                        Last edited by firbikrhd1; 04-20-2011, 11:37 PM.


                        • #13
                          Are you going to use a relay to power the horn(s)? This will take the strain off the horn button by having the relay take the load. Automobile relays are really cheap and usually come in 30 and 40 amp ratings.

                 (prewired relay socket)


                          • #14
                            Originally posted by MFolks
                            Are you going to use a relay to power the horn(s)? This will take the strain off the horn button by having the relay take the load. Automobile relays are really cheap and usually come in 30 and 40 amp ratings.

                   (prewired relay socket)
                            This is a replacement bracket for a second horn I installed some time ago. The first bracket broke due to metal fatigue. When I did the original installation I also installed a horn relay. The original wiring would not have been up to the additional load without it. Thank you for the suggestion though.