I designed one of the drive shaft couplers into my rotator system, based
on the suggestion in Dave Leeson's Yagi book. Mine was intended for a
BMW 1600, I think, and was bought off of the auction site for about $20.
I am told that all BMWs have something like this - do a search on
"guibo" and you will see what one looks like. If anyone knows where that
term comes from, I'd love to know!
73,
geo - n4ua
> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of John E. Cleeve
> Sent: Thursday, January 25, 2007 1:30 PM
> To: towerTALK@contesting.com
> Subject: [TowerTalk] Flexible coupler assembly
>
> Gentlemen,
> In view of the response I have received, permit me to publish a copy
of
> the
> email I sent to Dennis earlier today, also, I promise to obtain some
> close
> up digital photographs (Santa was thoughful!!) of the intstalled
flexible
> coupler
> assembly, when the tower is brought down for the summer
check........73,
> John G3JVC.
>
>
> ----- Original Message -----
> From: John E. Cleeve
> To: N6KI Dennis Vernacchia
> Sent: Thursday, January 25, 2007 12:52 PM
> Subject: Re: [TowerTalk] rotors, controllers, etc.
>
>
> Hello Dennis,
> I can recommend this way of protecting the rotor. I had several
> experiences
> of teeth breaking in the spur gearing of the average "Jap" rotator,
> entirely
> due to the mechanical stress, and the backlash in their poor
engineering.
> I
> have copied out the detail of the installation, originally for another
> member of the group, however, it does give a good idea of how I
protected
> my
> then new, and very expensive rotator. The name of the manufacturer, of
the
> flexible coupler is "Metalastic", and you have to imagine a six inch
outer
> diameter doughnut, with a section of about 1.5 inches, with six bolt
> holes,
> three to each coupling flange, in the transmission path of the
vehicle.
> You
> will have to do a little engineering, to couple this device into your
> antenna drive shaft. If you have a lathe, or, have a local engineering
> company make the necessary parts for you, then there is no problem.
The
> actual stores part number for this item is "Unipart" GCD 301. 62 Ne2
> 879407
> 19726, and the item is manufactured in the UK. "Unipart" is the
spares
> distribution system for Rover, Triumph etc. British cars. I bought the
> coupler as a new replacement spare part, and the cost was about 70
pounds
> sterling, plus our 17.5% value added tax, and it cost me about another
50
> pounds sterling "in pound notes!" to have some of the " metal turning"
> done
> by a local engineering company. Normally, this flexible coupler is
part of
> the drive train, ie drive shaft to the rear axle differential, used in
the
> Triumph TR7 sports car, and as such, more than able to cope with the
> torque
> stress applied by even force 12 gusting wind conditions in our
> applications......So, here you are, the detail, as I posted it to to
the
> reflector, I hope you find the information of some use....sincerely,
John
> G3JVC.
>
> I am sorry but I do not have any digital pictures, but I can give a
verbal
> description, so here goes:-
> The Italian worm drive rotor I have, is a PST medium range model. The
> rotor
> is bolted to a horizontal plate, which is part of the head unit, of my
> 60ft
> Strumech tower. The drive output of my PST rotor is a 4 inch diameter
> horizontal disk. and the rotary drive shaft to my yagi, is 2 inch
diameter
> construction grade aluminium tube, with a 0.25 inch wall thickness.
The
> rubber doughnut I used in my flexible coupler, normally forms part of
a
> Triumph sports car drive train, coupling the prop shaft to the
> differential.
> The outer diameter of the doughnut is about 6 inches, and its cross
> section,
> about 1.5 inches. The doughnut has six metal sleeved holes through
the
> rubber, intended for three fixing bolts to each flange of the
> interconnected
> prop shaft.
> In order to make use of the doughnut, I had two aluminium discs cut,
each
> 7
> inches in diameter, and 0.5 inch in thickness ( it took about five
> minutes).
> The discs and the doughnut were very carefully centred. The discs were
> then
> clamped together and the three hole fixing pattern, for the concentric
> rotation of the doughnut, was drilled.
> One disc was then engineered to fit the 4 inch drive plate of the PST
> rotor,
> and the other disc, which forms the top, or drive disc, engineered to
> couple
> the yagi. In order to couple the 2 inch diameter drive shaft from the
yagi
> to the drive disc, a 6 inch long, 2.5 inch diameter bar of aluminium
was
> used, this bar was then bored 2 inches internal diameter, to a depth
of 5
> inches. The 2.5 inch diameter bar is then drilled and tapped with
three
> holes, at the blind end, and secured, concentrically, by stainless
steel
> screws, to the top of the drive disc. The yagi drive shaft will then
slide
> into the bored 2.5 inch bar, to a depth of 5 inches, this
sleeve/shaft
> assembly is the drilled, 0.5 inch clearance, at right angles to the
axis
> of
> the sleeve/shaft, and a 0.5 inch high tensile bolt passed through the
> complete sleeve/shaft assembly. This works well, and will not "slip".
> In order to assemble the rubber doughnut coupling, six spacers were
made
> from 1 inch diameter aluminium, bored to take the doughnut fixing
bolts,
> and
> of a length, to allow approximately 1 inch spacing between the inner
faces
> of the two 0.5 inch thick discs and the sides of the rubber doughnut.
The
> complete drive chain is now rotor/disc/doughnut/disc/driveshaft
> coupling/driveshaft/yagi. The yagi drive shaft then passes up through
the
> collar of the tower head unit, where the vertical load is taken by a
large
> roller thrust bearing, rescued from the rear axle of a huge tipper
truck
> in
> our local scrapyard. The weather covering of the doughnut coupler
assembly
> is formed by wrapping a thin soft aluminium sheet, around the outer
edges
> of
> the 7 inch discs, this soft aluminium sheet was a litho printing
plate, in
> another life. The weather shield is secured only to the edge of the
top
> disc, by means of a stainless steel, ducting strap. the weather shield
> extends down beyond the lower aluminium disc, by approximately 1 inch,
> thus
> enclosing the entire doughnut coupler assembly. All exposed metalwork
has
> been given several coats of Finnigans clear Waxoyl (prevents
corrosion,
> and
> stops ice forming in winter). As the doughnut flexes in taking up the
wind
> load, the two coupling discs are able to gently move with respect to
each
> other. So, there you have it, I have done all I can think of, to
relieve
> the PST rotor, of any unnecessary mechanical stress, and I hope,
> prolonging
> its working life. I hope this information is of some use to you, and
also,
> the group, for I am sure that many people wish to protect the
investment,
> both in time and money, which is exposed to the elements at the top of
our
> towers, and this was my way........sincerely, John. G3JVC.
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
------------------------------------------------------------------------------------------------
This message is for the designated recipient only and may
contain privileged, proprietary, or otherwise private information.
If you have received it in error, please notify the sender
immediately and delete the original. Any unauthorized use of
this email is prohibited.
------------------------------------------------------------------------------------------------
[mf2]
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|