[HBR] Dials (was 'HBR 16')

[David Newman]

WALT,


Are these the Jackson verniers, dual reduction ball drive, that you 
mentioned?   Did you mean they work with National Dial, or Millen Dial?



http://www.surplussales.com/ShaftHardware/JacksonBro.html




73,


David
W3HYM







Walt Hutchens wrote:
> Introductory cliche: The dial you want really depends on what you're
> trying to do.
>
> When building an HBR-series receiver, both the National ACN (and
> relatives) and the Eddystone are 'authentic': Ted Cosby built with the
> National dials but many other builders used the Eddystone.
>
> Advantages of the National dials are mainly ease of layout and
> construction. They're also fairly inexpensive when you can find them.
> The standard ratio is around 5:1 or 6:1 which, if you're tuning a 500
> kcs band in that 2-1/2 turns is MIGHTY fast for tuning SSB. They're
> satisfactory, however, for a vintage radio night set that will be used
> mainly to receive AM.
>
> An upgrade is the use of a Millen dial having a two-speed drive,
> typically 36:1 for most of a knob revolution, then 6:1 thereafter.
> Quick QSY but you get a slow enough rate for tuning in SSB when you
> arrive.  These are planetary ball-type drives.
>
> Jackson Brothers makes (made?) both a single-speed version of the
> drive assembly for this dial and a two-speed one. They were available
> in the U.S. (UK company) not long ago, maybe still are. These drives
> with a home made dial scale and frame are an excellent combination of
> construction practicality and good performance.
>
> Planetary ball-type drives (and dial assemblies) are available on many
> inexpensive junker sets but they are frequently worn to the point
> where backlash will be annoying. A good bet if going this route is an
> FT-101 series junker since the (single speed) front end tuning control
> drive got a lot less mileage than the main tuning knob on other sets.
> Metric dimensions on this set, for example 6 mm shafts. The Sideband
> Engineers SB-34 sets are pretty common as junkers and they have the
> two-speed version of this drive, though it's often worn.
>
> Worn planetary ball drives can sometimes be much improved by pinching
> the fingers that hold them together VERY SLIGHTLY with a pair of slip
> joint pliers.
>
> Planetary ball drives can require significant torque.  It's best to
> mount them so that is transmitted to the panel rather than to the
> chassis or (worst of all) the capacitor frame, to avoid backlash
> issues.
>
> If your metalworking skills are new or rusty, I'd say pick one of the
> choices above. There's nothing more frustrating than being unable to
> get the parts in the right place without chewing up a lot of chassis
> and/or panel. The two speed planetary ball drives really can't be beat
> for performance AND (with proper pointer and frame) vintage appearance
> on an HBR-type set.
>
> Layout and construction is straightforward: Set the capacitor on a
> hard flat surface, measure the height of the center of the shaft, then
> mount the panel temporarily on the chassis and measure up the same
> distance. Be sure the chassis is FLAT. Use a flex coupling between the
> dial and the cap but get perfect alignment so the coupling has no
> visible work to do.
>
> The tuning cap should have the lowest torque requirement possible,
> consistent with no shaft side play. When the tuning cap is mounted
> flat to a large chassis it's generally a good idea to stiffen the
> chassis where the cap is mounted by epoxying a plate on the underside.
>
> The Eddystone 898 is the top of the line for performance with strictly
> vintage parts. 55:1 ratio, flywheel, sliderule type with logging
> scale, can be lighted, very smooth. The 898 is, however, a four-star
> B***H to lay out properly and install. There are basically three ways
> to go about it: 1. With the cap shaft far enough above the chassis so
> the flywheel doesn't hit -- easiest but a VERY high tuning knob. 2.
> With clearance cutout in the chassis for the flywheel -- better knob
> height but more work. And, 3. With the chassis spaced back from the
> panel enough to clear the dial mechanism.
>
> These are hard, harder, and a real mess, respectively.
>
> Eddystone HBRs are laid out somewhat differently than the original
> ones but that has all been worked out and the info is in the list
> archives and/or on the CD.
>
> Another possible avenue is old junker broadcast radios, particularly
> the better models that had slide rule dials. While not a match for the
> Eddystone, these can be quite good and they're both cheap and not too
> hard to find.
>
> The command set dials can't be beat for quality -- scissors-type
> gears, and so on.  They were designed for a single scale (single band)
> so they're not a great fit to an HBR project, but it can be done.
> They're much better for a set where the main tuning is a tunable 1st
> IF so only one calibration scale is required.
>
> The big problem with multiple dial scales is that the knob shaft is
> off to the lower right but close to the dial hub so you have a lot
> less room for scales than you'd have with a central knob or one set
> further off.
>
> The command dial drives are integrated with a three-gang tuning cap
> (receivers) or single gang cap (transmitters). You can, however,
> remove the 'works' of the cap and install your own in that space. With
> the dial on the front panel the capacitor shaft is PARALLEL to the
> panel so the usual HBR layout requires considerable rework.
>
> I made a dial for a miniature set from the drive for a command set
> control box. This gives you a gear reduction drive with a
> make-it-yourself pointer and an output shaft that's perpendicular to
> the panel. There's metalwork but it can be done with hand tools and a
> drill press. Quality isn't quite the equal of the command set itself
> (gears are smaller) but it was entirely satisfactory.
>
> With completely home brewed dials, the sky is the limit but the
> metalwork can be a challenge. Browsing old radio construction magazines is
> probably a good way to get ideas.
>
> Walt
> KJ4KV
>
>
>
>
>
>
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