HDR300

[Bud]

Bob Eslaire wrote:
> 
> Bud wrote:
> >
> > Have been using HDR-300 types for years - presently using 6.  I thought
> > I had seen everything break that could but here is a new one...
> >
> > The upper cast aluminum housing became a hunk of junk!  Antenna it was
> > turning is a 3 ele homebrew full sized 40m-- elements start at 3" and
> > boom is 5 inch  --- so it was turning a bunch.  What happened is the
> > antenna torque was so great that the four bolts holding the rotor to
> > the  rotor plate broke from the housing.  The upper housing is cast
> > aluminum  and the first one I have ever seen broken.   Anyone else with
> > this
> > experience?
> >
> > I have had all the normal failures electrical and mechanical but this
> > was a first.  Removed and repaired it today.... hope to get it going
> > tomorrow wx permitting.
> >
> > This whole thing was caused by pinning the mast to the mast clamp!!!
> > My opinion is it is better to allow a bit of slippage in high winds than
> > to have something break!
> >
> > Antenna is about 25 ft/sq es weight is abt 400 lbs.  Just passing this
> > along to keep anyone from having the same trouble.
> > 73-bud
> >
> 
> Hi Bud.
> 
> I am curious if you have the boom of your antenna mounted symmetrically,
> i.e., mounted in the exact center of the boom?  This should reduce the
> stresses on the rotor.
> 
> I too have had a lot of trouble with my HDR-300 (but not with the case
> cracking-yet!).  I attribute my problems (cast output gear broken into
> pieces [replaced with solid steel gear] and shearing of the key between
> the output shaft and the output gear [repaired numerous times]) to using
> an antenna which had an asymmetrically mounted boom (KLM 6el 20m).  The
> boom was mounted such that the fore/aft split was 31'/26.7'.  A back of
> the envelope calculation tells me that this introduces about 3000 in-lbs
> of torque.  My manual says the braking torque is 5000 in-lbs (I bought
> mine in 1981-newer specs show 7500 in-lbs).  However, according to an
> article that Dave Leeson (W6QHS) wrote in QEX (June 1995), the 1" output
> shaft is only capable of 471 in-lbs (assumes common steel)!  One has to
> use a shaft with a diameter of 2.18" (common steel, again) to achieve
> 5000 in-lbs.  I understand Hy-Gain has a new output shaft.  I am not sure
> what it is made of but I think it is still 1".  A harder material will up
> the capability of a 1" shaft.
> 
> Bob, W9UI.
No, the 40m beam is not exactly ballanced.  All the HDR300's here have
been modified using the new steel main gear.  A ham friend, KQ4DO, is
in charge of a factory locally ( we are a small town!!!).  In their 
factory they have a very complete machine shop.  They have made me new
shafts with improved key-ways for my rotors.  They did this several 
years ago before hy-gain did it!!!
I have never damaged one of their shafts or keyways!!  Sure pays to
have  friends--- KQ4DO did all of this free--
73, bud

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