1934-57 Norton Upright and Laydown Gearbox - Cam Plate And Quadrant Spindle Bush's (Pair)

Product no.: 1051 A2/344

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£26.30
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This listing is for a pair of the plain Phosphor Bronze bushes of the type that was fitted to the gearbox shell of both the Norton ‘Upright’ type and later ‘Laydown’ type Norton gearbox's, and allowed smooth rotation of both the gear selector camplate and the quadrant spindle operating the camplate.  Originals tend to wear badly and adversely affect gear changing.  These bushes are CNC manufactured and have been made to a specific tolerance so they should not require further honing once pressed in.  

Price is per pair (i.e two bushes – required for one gearbox shell)

A number of customers have asked me in the last two years if we can supply these, as they have gearbox’s with worn bushes, leading to a sloppy gearchange selection - so we have now made a batch, and the accompanying photographs and information below gives information on the removal of the old worn bushes and fitting of the new ones.

 

Background and Fitting Notes:

These are CNC manufactured phosphor bronze bushes, and as part of the setup for these, we took a good condition original (upright type) Norton gearbox shell and removed one of the original bushes, and then fitted these newly manufactured bearing (both tasks being done with the gearbox shell heated up in an oven – normal practice when undertaking this task) - so we could confirm the internal bore tolerance with a STOP/GO gauge once fitted, to ensure best fit possible, and hopefully this should in most cases remove the need of any further honing or reamering once the new bushes are fitted.

Obviously – we cannot guarantee that this will be the same for every gearbox - as the condition, wear and machining tolerances of the original gearbox and selector plate/selector quadrant shaft all play a part - but we hope this attention to detail will give the best chance of an ideal fit, without further honing or reamering of the bushes being necessary. However, it is very important, having fitted the new bearings to ensure both the large circular selector plate, and the lower quadrant spindle, both move freely in the new bushes.  If either are tight – then it will be necessary to carefully work the bush until there is smooth and free movement – this can either be by using a hand scraper, reamer or by honing.

As a final point - in making these bushes, we have made the outer diameter a standard interference fit, as per the original bearing - and an internal diameter, that should close to the standard tolerance once fitted.  However, we also made a small quantity of bushes with a 1.5 thou (inch) undersize internal bore - in case a customer knows their spindles are worn and require linishing, or wish to ream themselves after fitting.  Email us on sales@racingvincent.co.uk if you require these, but quantities are limited.

Removal of Old, and Fitting of New Bushes:

In the accompanying photographs we show the removal of old bushes from an original Upright Norton gearbox (from a WD 16H Norton I believe) and then fitting of new bushes - using an alloy drift specially machined to fit the bronze bush. One end of the drift is machined so it fits into the old bush and has a lip that will push up against the old bush, but will not touch the gearbox shell – and allow the old bearing to be tapped out with a mallet.  The other end has a similar lip to allow a new bearing to be pressed in – but this end also has a large flat steel washer up against the shoulder – this is important, because the lower bush housing on Norton gearbox’s have a recess around the bush housing – allowing for a Felt Seal to be fitted – this large washer ensures that the new bush is only pressed in as far as the outer ring of the felt seal housing – and is exactly flush -  See the accompanying photographs to see how this looks – when correct fitted, both bearings should be level with the housings with a flat ruler across them.  On the inside, both bearings will protrude slightly into the gearbox shell – again, see photographs attached.

It is important when pressing out old bearings, and then pressing in new bearings, that the gearbox shell is hot – so as to ensure as little stress as possible to the gearbox shell, and make the task easier.  I always place the gearbox shell in the oven for approximately 20 minutes, and I normally test by spitting on the gearbox shell – when the spit bounces back at you, the shell is hot enough. You will find the new bushes have a slight chamfer on one end – this is the end that should be pressed into the gearbox shell first, and will aid fitting. 

Always try and ensure you keep the new bearing and drift as vertical as possible to the gearbox bush housing when pressing in new bearings – and it goes without saying that the gearbox shell should be cleaned of all dirt and oil before fitting.  Similarly – having removed the old bushes, before fitting the new bushes, ensure the housing holes are clear of any debris and any score marks or high spots – which sometimes occur when removing old bushes.

Once the new bushes are fitted, ensure the camplate and quadrant spindle both turn freely in the new bush, then they can be greased and assembled.  Note that the lower bush housing is intended to take a felt seal – we are currently trying to get these felt seals manufactured, but we do sell proper wool felt sheets in various thicknesses in our Gasket section if we have not updated this listing yet to say they are available.

This process of fitting bushes is normally the same for both Upright and Laydown type gearbox shells.

Early (pre-34) Sturmey Archer Gearbox’s:

It should be noted on all Norton gearbox’s (after approximately 1934), the lower (quadrant spindle) bush has a recess around its outside circumference for the fitting of a Felt Seal - this can just be seen in the photograph behind the external selector arm.

However, prior to this type of in-house manufactured ‘Norton’ gearbox being fitted (which seems to have been sometime in 1934), Sturmey Archer gearboxs were used – in both 3 speed and 4 speed variants. Although looking very similar to the standard Norton gearbox referred to in this section, the earlier Sturmey Archer type shell had many smaller differences – one of these being that the selector fork/quadrant bushes were narrower, to allow for an internally fitted felt seal on both bush spindles. 

In the last picture on this listing, we show a comparison of the typical Norton Upright type gearbox shell (on the right), while an earlier Sturmey Archer type 4 speed gearbox shell is shown on the left.

If you believe you have a bike with this earlier type gearbox shell fitted – then the process of changing bushes is different, as are the bushes – for these, please see Item 1053.

 

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