English French German Italian Spanish

Fitting a Norton AMC gearbox into a 55 ES2

Submitted by dan_field on Mon, 13/06/2016
Forums
Singles

I've spent a day in the shed, my pre featherbed ES2 (1955) would have had a lay down box but was fitted with a matchless AMC gearbox, the box is toast, although it selects all gears and doesn't jump out of gear, it is noisy which I think is the main shaft bearing. Anyway I bought a recon Dommi gearbox and have taken out the old AMC box and dropped in the new one, but Sod's law has played a hand.

i thought that all pre commando boxes used the same case, if they do then the pre featherbed gearbox plates I have are not for a Norton AMC box, the top slot for the mounting on the plates is about 1/2 inch too high. So unless the later pre featherbed frames had a different mounting position (I know the cradle changed) ive got the wrong plates.

Which leaves me wondering if it's the plates or the gearbox that is the mis fit. if it's the plates they must be for a lay down box in which case I'll have a set for copying/sale! I'll post a pic later.

Interestingly the matchless AMC box fitted perfectly into the bottom mounting, the Norton one requires a small spacer.?

Submitted by roger_deadman on Mon, 13/06/2016

Permalink

Hi Dan many years ago i fitted an AMC g/box to my 1951 ES2 while i was repairing the lay down one it fitted straight in i also have a 1954 s/arm ES2 that is fitted with an AMC box these were both norton boxes .I seem to remember the AJS and Matchless AMC boxes the two fixing points were further forward so a different casting

Regards Roger

Submitted by anthony_williams on Mon, 13/06/2016

Permalink

Previously roger_deadman wrote:

Hi Dan many years ago i fitted an AMC g/box to my 1951 ES2 while i was repairing the lay down one it fitted straight in i also have a 1954 s/arm ES2 that is fitted with an AMC box these were both norton boxes .I seem to remember the AJS and Matchless AMC boxes the two fixing points were further forward so a different casting

Regards Roger

i have a matchless box under the bench.and the lugs in the case

are differant than my dommi.

tony

Submitted by richard_payne on Mon, 13/06/2016

Permalink

The Matchless boxes do indeed have different shells from Norton. It's the reason that on the AMC twins, the outer cover sits so nicely, close to the timing cover but on the Nortons it looks as if it wasn't made to fit and points up in the air.

Presumably it was dictated by the centres on the primary drive but as I'm a conspiracy theorist, I tend to the view that AMC deliberately set out to make the Nortons look dowdy when compared with their own models.

Submitted by neil_wyatt on Mon, 13/06/2016

Permalink

If and I say IF the pre f/bed plates from 57/58 singles will fit your frame, Dan then the club can make a set for you as they now have an accurate copy as templates. You would need to weld on the tube through the primary cases but I already sent you the drawing for that.

If your plates are the same as an early 50's ES2 then there is a member called Ian waiting for some. Again, I suggest a donation to the club so they have an accurate template and that solves another problem.

Submitted by dan_field on Mon, 13/06/2016

Permalink

Just had another good look and I think my panic is over! My frame has been rather agriculturally modded for trials, but I have a bog standard frame I bought in case I wanted to put it back onto mainly road use. My gear box and plates fit pretty well in that frame, closer Inspection of the trials frame shows that I think I can make it fit with a bit of careful filing, I think it's just down to build tolerances.

Neil given that the plates I have match your drawings if my plates were wrong, then so would yours have been!

I think I'll knock up some aluminium plates tomorrow as templates before setting to on the originals!

Submitted by neil_wyatt on Mon, 13/06/2016

Permalink

Yes Dan, mine and the set I donated to the club were made for the 57/58 singles, so they are correct for that application. Anything earlier I could not say but they were also for the Norton AMC box.

Submitted by dan_field on Tue, 14/06/2016

Permalink

Surprising what you can do in afternoon with a jig saw, drill and file. Ignore the dexion, that's a temp footrest mounting while I decide where I want them!

photo image_zpsyuz4wr2k.jpeg

Submitted by dan_field on Wed, 15/06/2016

Permalink

Ok I've got the plates sorted, that much was straight forward, but my next issue is the clutch, you can see from the pic below that the sleeve on old AMC box on the floor extends beyond the gearbox sprocket giving it a stop to bolt up to,

photo image_zpsgb8gmjih.jpeg

however the Norton box I have fitted has no such extension so if I fit the clutch it will foul the inner chain case? Is the problem with my clutch or with the gearbox? (number N 14097)

photo image_zpswsoo7ndl.jpeg

Dan

Submitted by anthony_leedal on Wed, 15/06/2016

Permalink

Dan,

Looks to me as though a "dry run" using the clutch chain wheel, engine sprocket and chaincase that you plan to use may be the best way to find out if everything will line up and if you will have enough room for the primary chain. The clutch/mainshaft on my 500t look much the same as your photo and everyhing does clear but only just. The edge of your clutch backplate does look very close to the two tapped holes for the swinging arm brace in the photo, or is this just due to temporary gearbox positioning? Are you building this as a trials bike, similar to that one on evilbay recently? (did it sell eventually and for howmuch?) I have a frame like yours and the plan is build it up using various bits I have left over from other projects, `twill be a road bike though probably a "swinging arm Inter lookalike" to give the rivetcounters somthing to chunter about

Good luck with your project

Tony

Submitted by dan_field on Wed, 15/06/2016

Permalink

Thanks Tony,

The frame has been modded for trials, back in the 70s 80s, but to be honest I think it was modded into a farm bike!

The front down tube has been shortened as have the rear shock mounts, my intention was to make a reliable green laner/ fun trial bike capable of a few miles if I want to. And yes it could look the one on eBay recently! but the agricultural frame mods would need some attention!

ive been tying to fit the chain case all afternoon but just can't get it fit without rubbing. The space between the gearbox sprocket and clutch body is about 5mm less than on the matchless box. Also on the Norton box the clutch will be tightened up against the taper on the splines, is that normal?

Submitted by anthony_leedal on Wed, 15/06/2016

Permalink

Dan,

It is correct for the clutch to tighten up to the end of the splines, the splines themselves are not tapered it is just the end of the spline where the machining "runs out" where the clutch abuts. The clutch must not tighten up against the end of the sleeve gear oterwise the gearbox will be locked solid! In effect it would be a fixed single speed drive. I`ll measure the gap brtween the back of the clutch and the gear box sprocket on a 500t box later tonight, its a dolls head not AMC but will give an idea of how little clearance you can get away with.

ATB Tony

Submitted by dan_field on Wed, 15/06/2016

Permalink

Of course you are right, I was having a senior moment! But having done a bit more research some clutches have a shoulder to stop the spider going down the shaft too far, mine doesn't. Looks like it's a common problem .......

http://www.nortonownersclub.org/noc-chat/technical1-singles-forum/189864554?b_start=0#527550686

like the poster above my clutch has no shoulder, so slides on too far what I can't find out is why it doesn't have a shoulder, what is it off?!

Submitted by anthony_leedal on Fri, 17/06/2016

Permalink

Dan,

Sorry for not getting back sooner, I have measured the mainshaft on the oily ES2 which is on the bench at the moment, the distance from the end of the sleeve gear to the end of the splines is 1 5/8" and the distance between the back of the clutch and the front face of the sprocket is 3/4". There is no shoulder in the front of the clutch centre, the splines run straight through so the clutch is located at the rear by pulling up against the end of the mainshaft splines where they start to taper. If your clutch is going on too far for whatever reason maybe you could make up a spacer of the required thickness with the internal dia. of the root of the splines, weld it to the rear of the centre, mig or stick, then file out the slots so the spacer now fits over the splines, it should only take a couple of hours and you will be ready to go. Might be as well to strip the centre first and take out the cush drive rubbers or they may catch fire.

Regards Tony.

Submitted by dan_field on Fri, 17/06/2016

Permalink

Tony, thank you for your info, my shaft is also 1 5/8" from the sleeve gear to the end of the splines, which is reassuring! however the distance between the gearbox sprocket and the back of the clutch is much much less, but if I pull the clutch centre so it's just proud of the shaft splines IE so the nut has something to bite on I,ll have a gap of about 5/8ths which I can live with so long as the engine sprocket lines up ok.

I've no worry about the rubbers melting they are already just a sticky mess!! so have ordered a set along with a RGM spider so will see how that fits before I get the Mig welder out, although I'm not sure about making a spacer at the back of a clutch, that seems like some careful filing is required ....if I've understood you correctly!

Having looked more closely at what I took off I can see that the PO had put a small spacer on the threaded part of the splines to keep the clutch body back and packed out the back of the chain case with a piece of metal and a fat leather washer.! Which needless to say had worn away so the clutch was floating and rubbing.

 


Norton Owners Club Website by 2Toucans