Ball Bearing Speed Reducer

David's links to Jackson jogged my memory. I think there may be three different types of reduction drive being described on the thread:

• A single knob with a two speed function. These reduce for a single turn and then go into fast mode until the knob's direction is reversed, when they reduce again for a single turn. So you can rough tune quickly to a station and then fine tune when you get close. Common on cheaper Short Wave sets and domestic radios. Presumably the mechanism provides two speeds by hitting end-stops.
• A single knob with a single speed reduction. For BFOs, reaction controls, bandspread tuning etc. Same mechanism as above I suspect, but no end-stops.
• A dual knob; inner ring high gear for rapid tuning, outer ring low geared for fine tuning. Used on mid-range SW sets I think and not common in my experience - the radios I've known in this category all had gears.

The downside of ball-bearing reduction drives is that they get lumpy as they wear out. Modern sets all seem to use rotary encoders and digital tuning. Mechanical reduction drives for radios are getting hard to find.

Dave

Edited By SillyOldDuffer on 26/12/2017 13:17:56

I won't say my printed version works - it doesn't as the 14mm balls turn out to be 9/16" - I should have measured them first I printed the holes slightly oversize, but even so they are too tight to turn easily.

But it proves the method of construction nicely and lets me see where the critical fits are.

I've ordered some 9mm balls. Using a 3/32" shaft the outer tapered race will be around 21mm at its wide end so the whole thing will suit a 1" housing.

The effective diameters are the outside of the small shaft and the ball diameter minus a small amount to allow for the seating groove and the taper on the outer race - say 0.2mm.

Ratio will be (9-0.2)2.4/2) or about 7.3:1. with 3/32" shaft and a bit less than 9:1 with a 2mm shaft.

Hello Neil

Here is a blue print copy of a 1981 exam for driving a potentiometer.

Now a mulltipliying spindle using the same mechanism.

Thanks Jacques,

Confirms my thought that the performance can be improved with a second bearing, but doeas appear a touch over-engineered.

It would justify the price of top end telescope focusers if they had that complexity!

Neil

Hi there, all,

The start of this thread reminded me of a gizmo described in the trade press back in the 1970s, the 'Cyclo' speed reducer. I've been a bit busy being festive for the last few days but I found time this morning to root out the demonstrator I received back then in response to my ringing the appropriate number on the magazine response card.

Here are a couple of photos of the demonstrator:

and here are scans of the accompanying leaflet (I'm sorry but I can't offer a translation):

Here's a YouTube video with an animation showing the operation of the device:

**LINK**

Best regards,

Swarf, Mostly!

Is that blue and grey thing a harmonic drive? I had to buy one of them just so I could take it apart and see how it works. A bit like Sylar if you remember him. Darned things are about the same age as me but I'd never heard of them.

Fascinating gizmo, looks like an epicyclic box but does 50:1 in one stage and the output goes in the opposite direction to the input

If you want to do a Sylar you are welcome to borrow it.