[TowerTalk] Building a Tower Trailer

JC Smith jc-smith at comcast.net
Tue Jun 27 13:37:55 EDT 2006


Your CG problem was more likely the CG too far back as opposed to too high
(although that's not good either).  More weight on the hitch usually
prevents the oscillation.  I don't know if you have trailer breaks, but if
you do you could have used them only, without the tow vehicle breaks, and
that would have helped you slow down and dampen the oscillations at the same
time.  Hindsight, I know, but might help in the future.

73 - JC, K0HPS

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]On Behalf Of Michael Tope
Sent: Tuesday, June 27, 2006 10:24 AM
To: Mark Beckwith; towertalk at contesting.com
Subject: Re: [TowerTalk] Building a Tower Trailer

----- Original Message -----
From: "Mark Beckwith" <n5ot at n5ot.com>

> Jim was critical of the CG issues, but in my opinion, they come with the
> territory.  You're holding over a thousand pounds of steel at about 7 feet
> above the ground, you're going to have CG issues.  I don't know the
> details
> of the "scary moments" alluded to, and I don't mean to imply that those
> guys
> are bad drivers, but I logged probably 2000 miles on those trailers in 14
> years, and I never felt uncomfortable towing them, not once.  I also never
> had to swerve to miss a deer, or had to drive with a hellacious
> cross-wind,
> which could well cause problems with such a payload.

I am probably the source of this concern, Mark. Two years ago
we had some Rohn 25 sections lashed to the Caltech trailer (N6VI's
old trailer) pretty high on the racks next to the Tri-ex tower which
made an already high CG even higher. On the way back from Mt.
Gleason, California I had a "need a change of underwear" near
mishap on the I-210. When I got on the freeway, I speeded up to
get ahead of a van who wasn't interested in letting me in. This was
a big mistake. Before I knew it, I had hit ~75 MPH and the tower
trailer started to oscillate violently. I was almost sure I was going to
dump it and so was everyone else on the eastbound side of the
freeway. When I glanced up in my mirror, the I had a good quarter
mile of the freeway to myself whereas moments before it was
jammed with cars. Somehow I kept my cool and was able to bleed
off some of the energy and get the thing tamed (I was afraid to hit
the brakes too hard). I don't think I have ever been so relieved in all
of my life. When I got back to Caltech with the trailer, I immediately
noticed that the axle was bent. I don't know for sure that it wasn't
like this before the "incident", but my suspicion is that the violent
side to side motion of the trailer bent the axle.

Since that time, whenever I get on the freeway with the trailer, the
first thing I do is to set the cruise control to 50 MPH (tailgaters be
damned).  At 50 MPH the trailer feels rock solid. It would probably
do just fine at 55 MPH as well, but I have no interest in pushing my

So, yes, the high CG is an issue, but it appears to be a manageable
problem if you keep the highway speeds reasonable.

> Can we get the Caltech/JPL guys to post a set of photos showing the
> trailers
> in use?  I think there are a number of TT readers who would enjoy seeing
> them.

I have some good shots that I can put on my website. I post a link
when I get around to it.

73, Mike W4EF.................................


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