Mystery Gearbox

[Colin Morgan]

So, is the description below the usual 4-speed crash box, or this one, I wonder?

"A Gearbox with a Silent third Speed
A Résumé of Recently Published Patent Specifications

MEER name of Sir Herbert Austin, K.I3.E., appears , in patent No. 343,183, which describes a neat and compact gearbox of the kind in which a,.1. eccentrically mounted sleeve with Internal and external teeth is employed.

A is the driving shaft, which is bored out to form a bearing for the sliding shaft (D), and is provided with extetnal teeth (aI) and internal teeth (a). B is th•I driven shaft and is in the form of a sleeve with internal splines (b), which engage with the splines of the sliding shaft (D). Shaft D always revolves with the driven shaft, and has keyed to it the wheels f 'and f1 It is also provided with teeth (d), which enable it to engage with the teeth (a) of the driving shaft to give top gear.

The wheel (0.) has• internal teeth '(fl), which can, when shaft D is moved to the right, engage with the external teeth (Cl) of the eccentrically mounted sleeve ©. Both the sleeve © and the gearwheel (e) of the layshaft are In permanent engagement with the teeth (al) of the driving shaft (A).

The layshaft carries a wheel (e), which is keyed to it, and is splined for the sliding sleeve, which carries two gedrs (e2 and e3). The gears H and G are focmed integral with one another and are slidably mounted on a shaft; they are employed only for the reverse.

The operation of the gear is as follows

First Gear.—e and at in constant engagement, and e5 into fl.

Second Gear.—e and al in constant engagement, and e2 into f.

' Third Gear.—c in constant engagement with al, and f2 into O.

Fourth, or Top, Gear.—d engages with internal teeth (a).

Reverse.—e and alin constant engagement, G into e2 and H into f."


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It is from here:

http://archive.commercialmotor.com/artic...hird-speed

[Archivist]

The drawing that Colin has very helpfully tracked down:


  4speedbox commercial motor.jpg (Size: 83.22 KB / Downloads: 374)

Thanks Colin!!

[Bob Culver]

Thanks Colin and Archivist
I could have gone to bed half an hour earlier!
Relative silence came from helical gears. It was considered impractical to slide these in and out of mesh although the likes of Ford Zephyr later did.
In the b and w drawing the constantly meshed layshaft and sleeve gears are proportioned more as typical helical gears.

[Tony Press]

'So, is the description below the usual 4-speed crash box, or this one, I wonder?'

No- from the drawing above this is another variation on the original blueprint of a 'new' four speed gearbox, note the two ball bearings on the third motion shaft and the single ball bearing on the first motion shaft among a number of other differences. 

Presumably both boxes were design exercises  and I would assume that neither box was ever made. 

(Possibly this is the other gearbox drawing added to the Archive).

I expect that around the same time the new four speed crash gearbox was also designed, which was accepted and put in production, to be followed soon after by the all new 'synchromesh' four speed gearbox.     

[Archivist]

For completeness, I'm attaching the equivalent 'Silent 2nd' 3 speed gearbox for comparison.. Sadly, the original print is not as 'sharp' as the 4 speed gearbox, but hopefully the salient points can be made out.. If you double click on the image, it should open in a new window that will allow you to blow up the image size.

   

[Renaud]

Some "enhancement" for lisibility maybe:

[Ivor Hawkins]

Ah, that’s better Renaud!

[Renaud]

Ah, that’s better Renaud!

For you Ivor:  

[Bob Culver]

All we need now is ideas on how to dismantle it. The taper would appear a challenge.

[David Stepney]

It looks as if, once the 1st motion shaft and bearing are removed, and the rear bearing and housing also removed, the 3rd motion shaft should slip back sufficiently for the whole assembly to be removed from the top of the box. The taper could then be dealt with on the bench with either a suitable puller or press.