Author Topic: Gearbox commonality  (Read 10047 times)

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Offline Ian

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Gearbox commonality
« on: 28 Jul 2011 at 03:47 »
I now have the E28 running reasonably and have to venture on to the gearbox. As with most Douglas boxes of the era it jumps out of second - but this one is pretty bad. Also jumps out of first occasionally. In addition the linkages are probably worn as if I set it up to the gate properly so it sits nicely in second, first is very hard to engage. Lots to do - I want to have it on the road properly in time for the Cooma Girder Fork Rally mid October.

One question I have before pulling it apart - is there any commonality between the actual internals (gears, etc) between the OC 1926 gearbox (TG) and the E28 (WG). I have quite a few spare gears for the OC box but none for the E28!

Offline Alan Cun

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Re: Gearbox commonality
« Reply #1 on: 28 Jul 2011 at 10:03 »
Firstly Ian nothing from your OC box is suitable for the WG box. As previously stated nothing from the early EW boxes is suitable but later EW boxes with the semi circle rail fitting parts can interchange.  I have been told that there are  2 ways of helping it stay in second within the box.

1. Increase the indent on the mainshaft and increase the spring tension on the ball inside the sliding gear.

2. Carefully with an angle grinder back cut the locking dogs on the locking faces of second gear.

To be honest I am slack with my 29 always jumping out of gear and have put up with it for over 30 years. My excuse I guess is the way I previously mentioned moving off with the clutch and doing all other changes up and down with the left arm across the tank and holding it in second by the lever. Got some spare internals if your stuck or want to experiment.

regards Alan

Offline Ian

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Re: Gearbox commonality
« Reply #2 on: 28 Jul 2011 at 10:56 »
Thanks Alan - will let you know how it looks when I pull it apart !

Offline Doug

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Re: Gearbox commonality
« Reply #3 on: 29 Jul 2011 at 01:13 »
Ian,

It will look like this inside...



Second gear is engaged by four isolated splines in the middle of the layshaft. These are prone to getting well hammered along with the key way through the gear. Load through the gear set (at least constant mesh) tends to squirt the gear off the detent and out one side or the other into neutral or top gear.

-Doug

Offline Alan Cun

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Re: Gearbox commonality
« Reply #4 on: 30 Jul 2011 at 10:00 »
Went to the Nambour Car swap meet today where I share a site with my mate Des who I passed on an E29 a few years back. I asked him if his jumps out of gear and he said no but a previous restoration on a 28 EW did jump out of gear. His advice like Doug mentioned was to have a good look at the 4 short layshaft splines and if they are tapered towards the ends look for a better layshaft.

Alan

Offline Doug

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Re: Gearbox commonality
« Reply #5 on: 30 Jul 2011 at 11:37 »
Ian,

Further, the lay shaft and the 22t sliding lay shaft gear are shared in common by the 600 and 350EW models. The same part numbers are used on 350 models through 1929 (and probably later) and the 3-speed gearboxes as used on S6 and derivatives.

-Doug

Offline Chris

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Re: Gearbox commonality
« Reply #6 on: 30 Jul 2011 at 15:45 »
Hi all
    A permanent cure for jumping out of second gear has been the supply of modified new six spline layshaft and sliding second gear manufactured for the LDMCC by one of the foremost gear manufacturers for the three speed gearboxes. As mentioned by Doug this modified shaft and gear fits all three speed gearboxes from EW to Aero. I believe they are currently in stock for LDMCC members. Chris.

Offline Ian

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Re: Gearbox commonality
« Reply #7 on: 01 Aug 2011 at 22:40 »
Thanks for the updates - I have been away for a few days and just catching up !

Offline Ian

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Re: Gearbox commonality
« Reply #8 on: 13 Jan 2014 at 01:28 »
I rebuilt my E28 gearbox a while ago with the club 6 spline layshaft, etc. After a short while it was binding and proving very difficult to moved from second to neutral and first. I pulled it apart and polished it - and reinstalled. Worked fine for a short while and has started binding again. I am thinking maybe the tolerances in the machining are too tight so that any minor imperfections cause an issue. Has anyone else had a similar problem ? I will be dismantling again this week. Any suggestions for a more permanent fix ?

Offline Doug

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Re: Gearbox commonality
« Reply #9 on: 13 Jan 2014 at 03:40 »
Ian,

I had a look at my replacement 6-spline layshaft (not yet installed) from Quafie. Generally with splined joints, the shafts are centered by the flanks of the spline, not the major or minor diameters. In fact the major and minor diameters should have a clearance so they do not perturb the alignment. The problem is when that spline is used as a dog clutch, some clearance is needed on the flanks to get the elements to engage and disengage. What to do about keeping the gear centered and square to the shaft? Douglas fixed this by making the minor diameter of the gear a close sliding fit on the shaft (and minor diameter of the spline being a continuation of that surface). This helped center the gear all along the shaft from 1st, neutral, 2nd, and top. Quafie used the major diameter of the spline while the gear is engaged on the spline and the minor diameter when it is on the shaft. The minor diameter between the keys of the spline are undercut to provide clearance so that they did not need to be a precise continuation of the shaft surface. As the gear slides along it can tip a little, because it has to have some clearance. The leading edge of the gear can catch where it makes the transition between being guided by the minor and guided by the major diameter. The major diameter seems to be what is catching. In trying the fit and feel of mine, if I apply pressure and tip the gear as I slide it, it definitely feels more 'gritty' sliding along the spine than it does sliding along the shaft. However I can not see any difference in the surface finish of the surfaces that would account for this.

I would not recommend reducing the major diameter of the layshaft splines to prevent fouling or stop the surfaces from touching and producing the gritty feel. If you do, you will loose some of the alignment of the gear while on the splines. Rather I would oil stone a small radius in the keyways of the gear where the major diameter punches through. I think it is the sharp, leading edge of the spline that is digging in when the gear is being slid back and forth that is causing the most trouble.

-Doug

Offline Ian

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Re: Gearbox commonality
« Reply #10 on: 13 Jan 2014 at 03:43 »
Thanks Doug !

Offline roy

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Re: Gearbox commonality
« Reply #11 on: 13 Jan 2014 at 14:14 »
Hi Ian, I am having the same problem, thought it was just me.
Worked great for about a year. Wonder if there is a defect in production?

Roy.

Offline Ian

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Re: Gearbox commonality
« Reply #12 on: 13 Jan 2014 at 19:49 »
Roy, don't know about an actual defect - I think maybe a slight design flaw per Doug's post. I will do whats suggested and report back on progress.

Offline Doug

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Re: Gearbox commonality
« Reply #13 on: 14 Jan 2014 at 00:30 »
Ian, Roy,

If what I mean by "...oil stone a small radius in the keyways of the gear where the major diameter punches through." let me know a I will make a little sketch and upload it.

-Doug

Offline Ian

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Re: Gearbox commonality
« Reply #14 on: 14 Jan 2014 at 01:50 »
I think I understand Doug - but a sketch would be good to clarify

Offline Doug

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Re: Gearbox commonality
« Reply #15 on: 14 Jan 2014 at 03:30 »
Ian,

Surfaces indicated in red, and proportions exaggerated for clarity.




-Doug

Offline roy

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Re: Gearbox commonality
« Reply #16 on: 14 Jan 2014 at 14:30 »
Thank`s Doug, will give it a try and let you know results.

Roy.

Offline oily bloke

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Re: Gearbox commonality
« Reply #17 on: 01 Jun 2014 at 18:18 »
Hi,
What was the outcome of this discussion? I have fitted a club layshaft and the second gear is quite stiff as it slides across the splines. Did Doug's suggestion cure the problem?
Thanks
Andy

Offline roy

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Re: Gearbox commonality
« Reply #18 on: 01 Jun 2014 at 19:30 »
Hi Andy, due to moving house I have not got around to sorting gearbox yet, in fact the machine is still at my daughters.

Roy.

Offline oily bloke

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Re: Gearbox commonality
« Reply #19 on: 02 Jun 2014 at 18:19 »
Hi Roy,
Had a cog box fettling session today. The club lay shaft and 2nd gear was tight on the splines.  There were machine marks on the un-ground faces of the gears castellated face and the lead in on the dogs. This caused the gear to pause where the machine marks meet, effectively screwing the gear away from the dogs.
The tightness was cured by fine Carborundum paste in oil and the gear was slid up and down the castellation's in all positions until free and smooth and the machine marks were removed with a diamond dressing file. Thoroughly washed and degreased. Having assembled and fitted the box It now selects smoothly and positively.
Happy days.

Offline roy

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Re: Gearbox commonality
« Reply #20 on: 02 Jun 2014 at 18:34 »
Great news Andy, will have to get a move on, had the regulations come today for The Jeff Clew Memorial run at the end of the month.

Ride safe, Roy.

Offline oily bloke

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Re: Gearbox commonality
« Reply #21 on: 14 Jun 2014 at 18:23 »
Just a foot note to my comments. I completed the Banbury run without issue. Both the clutch and the gearbox worked well and did not need any adjustment. The clutch seems to have settled down and worked fine without drag or slip throughout the 70ish miles with plenty of stop and start and up and down the box. I was approached by two gents who had both recently acquired pre war douggies with flywheel clutches and I was questioned right up to the off regarding how it works. It seems to remain a source of confusion for many.
Andy

Offline Ian

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Re: Gearbox commonality
« Reply #22 on: 16 Jun 2014 at 11:55 »
I took mine for a run last weekend - first one since gearbox rebuilt for the second time. Seemed to all work OK so far - although the first time it took a few rides before second gear stiffened up

 

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