Can a mag mount come loose while driving?

Discussion in 'Mobile Radio' started by KK6DCT, Mar 15, 2015.

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  1. KK6DCT

    KK6DCT Ham Member QRZ Page

    What's the worst that can happen with a mag mount while driving? Is there any chance the mount could come completely loose at freeway speed and start banging around against the roof of your car? I've just put a Tram 1185 on my car and it's my first mag mount... it's shifted backwards a bit, but just wondering how secure these things are?
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Can one come loose? You bet your bippy!

    What could happen?
    Imagine a 2lb base on a car going 65mph. The force available (F=Mass * Acceleration) = about 195 Foot lbs. One reference on forensic medicine says the minimum level of force needed to penetrate a human skull is about 53 Ft/lbs. Lots of excess force available to decapitate or totally crush a skull of following driver, bicyclist or standing pedestrian. Don't forget if the base drifts into the opposite lane the force may be double (almost 400Ft/lbs) due to the higher closure rate.

    We haven't even considered flying stainless steel whips. bill
    Last edited: Mar 15, 2015
  3. KK6DCT

    KK6DCT Ham Member QRZ Page

    ... but has it ever happened to anyone in practice? (not the skull crushing part, just the coming loose part)
  4. VE3KUT

    VE3KUT Ham Member QRZ Page

    Had one on the roof for a few years now, one accident included. Stayed in place. This is just a 2M/70cm one though... HF might be an issue..<g>
  5. AL4Y

    AL4Y Ham Member QRZ Page

    I once had one fly off the center of the roof, pull out about 3' of cable, and land on the rear fender.
    KC9UDX likes this.
  6. N0NSR

    N0NSR XML Subscriber QRZ Page

    I had the magnet actually come loose from the base of a 2M/440 antenna; it acted like the glue that held the magnet in the base actually stopped holding. Scared the you-know-what outta me; the coax kept it from completely separating from the car, but it put several scratches in the paint before I could pull over and get stopped.

    That said, in 40 years of driving, many of them with mag mount scanner, Ham, and CB antennas, that is the only time I've ever had anything come loose on me.

    That said, most of my driving is rural, on two-lane highways and blacktops. If I was spending a lot of time on the interstate, I'd be more worried about mounting.
    Bruce - N0NSR
  7. K8MHZ

    K8MHZ Ham Member QRZ Page

    I had a 5/8" 2 meter mag mount come loose from my Z28 one night. On the freeway at 70+ mph. The antenna drug on the pavement behind me, making a bunch of sparks.

    Note to self: Make sure the magnet is strong enough to hold the antenna.
  8. AA9SD

    AA9SD Ham Member QRZ Page

    I have the same antenna (Tram 1185) and it has not moved at all at highway speeds. I don't think I've exceeded 75mph with it on though.
  9. K4ISR

    K4ISR Ham Member QRZ Page

    I've had my Tram 1185 for several months now on top of my Durango, and it has stayed put up to 85mph plus strong headwinds with no issues. Some weaker steel or aluminum vehicles it may not hold as well but that is the exception.
  10. KB1CKT

    KB1CKT Ham Member QRZ Page

    I've only had two problems with mag-mounts:
    -a RS CB one got tapped by branches once or twice at low speeds. Had to stop and put back on.
    -I had an RS 5/8 2m that I swear somehow bent the whip in half, and scratched the paint. I mean seriously? there were sudden new scratch marks that could only be explained by bending the tip down. I slid the antenna back a foot and made sure not to tell mom (I was borrowing her car at the time).

    Otherwise, I have not had issues. Large magnets for the antenna, and avoided branches. I do prefer antennas that bolt on somehow though. But at the moment I have a Hustler 2m 5/8 antenna, complete with one of their mag bases, and it's held just fine at 80-85mph on my car.

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