[TenTec] Encoder shaft stability

[Dr. Gerald N. Johnson]

On 4/13/2010 6:23 PM, Phil Chambley Sr. wrote:
> I've been toying with an idea and would appreciate input from the group.
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> Haven't had any experience with the Orions yet, but every on other T/T rig with an encoder, I've seen varying amounts of encoder shaft wobble.  If you lift up on the front of the knob, it'll move noticeably and irritatingly (at least to me).
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> The reason for this is T/T relies on the encoder bushing alone to serve as the only bearing surface, and that single-point bearing allows lateral "wiggle".   I think we can give the encoder a two-point support with just a minimum amount of effort.
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> What I have in mind is a circular piece of say, 1/16" Teflon sheet, about 1 ½" diameter, with a ¼" hole in the center.  Using a nibbler, cut out a bite every ¼" or so from inside of the hole so small "fingers" would be left to contact the shaft.  This would encircle and hold the shaft and still have only a minimum of surface contact area.
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> Then attach the Teflon disc under the knob to the plastic bezel using pins or #2 machine screws.  The latter would be placed outside the track of the tension arrangement.
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I think that the "support" from the teflon disk will be smaller than the 
leverage you have
at the edge of the knob and so the teflon fingers will be practically 
immediately deflected,
negating their benefit.
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> Comments please??  Better idea anyone?

I envision a bar of aluminum with thin ends and a fat spot in the middle 
supporting a bearing bushing. That bearing might be oillite, steel 
backed teflon, Vespar, or a needle roller bearing assembly. Such as 
McMaster-Carr catalog numbers 6391K126, 60695K61, 58315K42, or 5905K21. 
These will add some friction along with the shaft support and may 
require machining on the knob to give clearance. Any assembly will 
interfere with the knob drag mechanism if present. A little added 
friction may not hurt, giving the feel of there being some more drive 
mechanism behind the knob than just a optically sensed slotted disk, 
typical of the encoder is part of the wish to add a weighted knob. More 
like the National Dial or gear driven variable capacitor tuners of yore 
with a 25 or 50 to 1 gear reduction between the substantial knob and the 
variable capacitor. Where the top end radio tuning knobs turned like 
parts of precision mechanisms doing real work driving dial and capacitor 
(or PTO screw) often at much different rates than the knobs turned.
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> Phil C. Sr.
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> k4dpk
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73, Jerry, K0CQ