Gear Boxes

Previously john_brookes wrote:

Was the AMC box a straight replacement for the Laydown box?

i.e. would it be possible to fit a laydown box to a 1957 88 without any engineering?

hello the answer to your question is YES castiings are near the same ! yours anna j

Hello John - Make sure you get the correct type of Laydown box i.e. long mainshaft type. You will obviously have to play about with clutch cabling and pushrod length to suit your new set-up. The gear lever and kickstart lever are also different. Cheers, Howard

If you fit a laydown box to a machine originally ffitted with an AMC, the clutch cable will be an issue. On an AMC, the cable exits at an angle, to avoid clashing with the oil tank etc. My Model 88 has a horizontal box, and has a passage tube through the oil tank for the clutch cable. If I were adapting a later bike, I would look into a pulley to allow the clutch cable to approach the box horizontally.. The pulley used for ladies' bicycles with cantilever brakes is worth a good look and might work.

The AMC has a very high clutch lift ratio, and has 7/8" pivot levers to moderate this. Standard with horizontal boxes are levers with 1 1/8" pivots. Your clutch needs to be in very good condition and well set up to lift sufficiently with a horizontal box if you keep those 7/8" levers. Beware getting stuck in traffic, the clutch will start to drag and lose lift.

I think the kick start lever spline is the same for all Norton boxes and the AMC, but not the shift lever - the AMC ones have a smaller spline and are shorter.

As an aside, I significantly improved my horizontal box by getting metal welded onto the positive stop ratchet pawls, so that there is less lost movement before action starts in the positive stop mechanism. This can be done on any Norton box, ie doll's head, vertical and horizontal - but you are advised to make sure the external link on doll's head and vertical boxes is in good condition before you try this. The AMC has a much better re-designed positive stop mechanism, and also a long travel cam plate index plunger travel, which gives a major improvement in shift quality. There is not space in a horizontal box to replicate this.

Paul

The clutch lift ratio on an AMC box is wrong. It lifts the clutch too fast. You must use the 7/8" clutch lever with it, otherwise it is even worse than standard. People remove the clutch lifter arm from the box and grind it to lift the clutch less fast.

But why are you looking into swapping the AMC box for a horizontal?

Paul

As an aside, I significantly improved my horizontal box by getting metal welded onto the positive stop ratchet pawls, so that there is less lost movement before action starts in the positive stop mechanism. This can be done on any Norton box, ie doll's head, vertical and horizontal - but you are advised to make sure the external link on doll's head and vertical boxes is in good condition before you try this. The AMC has a much better re-designed positive stop mechanism, and also a long travel cam plate index plunger travel, which gives a major improvement in shift quality. There is not space in a horizontal box to replicate this.

Paul

The PO made a change to mine similar to this.

Of course if it does not work, it'll need to be replaced.

I don't know if it is case hardened or even if he hardened and tempered it. Both are possible.

As I look at this I see (I think) that the maximum lift is from the tip of the nose - so if that is shorter then it won't lift enough. He must have altered the curve by opening the slope out but leaving the nose in place. I can't 'edit' to delete the picture - but I suggest a cardboard model first! Somebody must have a similar sketch - I know what I'm looking for but cannot find it.

This is not my drawing and suspect it may have came from Dave Fenner. Apparently it is the best way to do the modification.

That's the idea... Thanks Phil. My previous owner left me with a clutch that's not too bad compared with a few I've encountered. Phil's sketch makes much more sense.

There is a pair of ratchet pawls in the positive stop mechanism. What I did was get a local welder to build the points of these pawls up with 'wear braze', and then filed them back to the same profile as standard, but with about 1/16" more metal. I would have to dismantle my box to find out exactly how much longer the pawls are than standard.

The wear braze work hardens so that it doesn't wear fast. I wondered if there would be a problem of insufficient clearance, or the large coil spring in the positive stop mechanism not being strong enough to return the gear shift lever forcefully enough, but I just fitted them and it works well first try. Time will tell if they do actually wear in service.

So far, I'm very pleased with the mod.

In case anyone asks me who did the wear brazing for me, It was an elderly welder known as 'Goldie' in Lower Hutt, New Zealand, in the late '80s. He's not around to do follow-up jobs.

Paul

Previously ian_soady wrote:

Previously paul_standeven wrote:

As an aside, I significantly improved my horizontal box by getting metal welded onto the positive stop ratchet pawls, so that there is less lost movement before action starts in the positive stop mechanism. This can be done on any Norton box, ie doll's head, vertical and horizontal - but you are advised to make sure the external link on doll's head and vertical boxes is in good condition before you try this. The AMC has a much better re-designed positive stop mechanism, and also a long travel cam plate index plunger travel, which gives a major improvement in shift quality. There is not space in a horizontal box to replicate this.

Paul

Hi Paul. I've just ridden my ES2 with laydown box for the first time and did find the lever travel a bit long - although the change was excellent. Do you have a photo or sketch of the mod you did? Cheers Ian

I think you are grinding the wrong part of the clutch lifter arm. It should be the lower part of the outer end, at the roller, not at the ball adjacent to the clutch pushrod. To make absolutely sure, set up the lever and watch it in action.

Paul

Previously David Cooper wrote:

The PO made a change to mine similar to this.

Of course if it does not work, it'll need to be replaced.

I don't know if it is case hardened or even if he hardened and tempered it. Both are possible.

As I look at this I see (I think) that the maximum lift is from the tip of the nose - so if that is shorter then it won't lift enough. He must have altered the curve by opening the slope out but leaving the nose in place. I can't 'edit' to delete the picture - but I suggest a cardboard model first! Somebody must have a similar sketch - I know what I'm looking for but cannot find it.

This is the right one. How much to grind is a matter of experiment. Don't cut too much....

I know someone who so hates the AMC clutch lifter that he fits the old-style quick-thread mechanism as on all the Norton boxes. It is a LOT of work.

Paul

Previously philip_hannam wrote:

This is not my drawing and suspect it may have came from Dave Fenner. Apparently it is the best way to do the modification.

gearbox-mod-jpg (172.8 KB)

Hello Can I but in here this guy was replacing his gear boxfrom AMC for A Norton Laydown Gearbox So all this Above is completely irrelevant As the Laydown gearbox clutch arm work in a brass screw type fitting to activate the push rod witch is a short rod as it meets up with the clutch mushroom lifter the same design as on the ES2 and Model 50 ,and the first model 99s not to forget the over head cam International wears the same clutch set up the 1955 oil tank were bernet cap type with the clutch cable tunnel in it, and Norvil will only send you the Dorothy type leaver witch are the wrong ones for a 1955 machine they should be as the 1954 model the solid type leavers with a off set and made by AMAL I have all these part number In my amal parts manual for these years to 1960, and Norton and AMC gearboxes were based on the Sturmey archer design they were bought out by Burman gearboxes just after ww2 but they keeped the simler design for Norton motorcycle of that time period, I have rebuilt both gearboxes Laydown and AMC, And the problem with the AMC clutch arm is some of them are not machined correctly at the back of the arm where the cable fits the original cable had a small ball end that the gearbox end now this ball should fit snug in the reeses machined out for to fit but some are not witch then causes the cable to be bent every time you operate the clutch, So to sort this out all that is need is to take out the arm and place in a Bench Press Drill and fit the right size Brooch drill and and drill out the back of the arm so you have a reeses for the cable nippel end to have room to pivite without the clutch cable bending a lot of after market cables have the wrong nipple ends most have a barrel end and it should a small ball end as the originals were,

yours anna

Points taken, Anna, but it's not all irrelevant. John's problem seems to start with poor clutch action, and so it must be a lot quicker, easier and hugely cheaper to suggest remedies as well as direct advice on the swap. After reading the above, I'd try to improve the original first before devaluing the bike.

Interesting what you say about the lever though. It's always looked to me like a bodged design, with no articulation provided to the end of the cable.

Dynodave was talking about the clutch and their's actuator: http://atlanticgreen.com/ndnsclutch.htm, interesting for all AMC-gearboxes

Fritz

Previously David Cooper wrote:

Points taken, Anna, but it's not all irrelevant. John's problem seems to start with poor clutch action, and so it must be a lot quicker, easier and hugely cheaper to suggest remedies as well as direct advice on the swap. After reading the above, I'd try to improve the original first before devaluing the bike.

Interesting what you say about the lever though. It's always looked to me like a bodged design, with no articulation provided to the end of the cable.

hello wellsome time ago I picked up a original clutch cable made by Amal with a grey outer for my Norton dominator model 88 1954 vintage from old Don Law shop his shop was an Aladdin's cave of old bike parts well this clutch cable still in its box with AMAL advertised all over it Had a small ball end at the gearbox end and a barrel end for the leaver end and the after market ones you get a small barrel that fallows the cable at the box end and a barrel across for the leaver end and most leavers in side the box are not machined out right and the cable ends get stuck and bend at the end, So its a good idea to have the gearbox end cable made up and get someone experienced in silver soldering and get them to fit you up a small bass ball on the gearbox end of the cable and get the inside gearbox lever machined to fit the brass ball for the cable to fit right no more bending on the cable as it will be a brass ball that fit nice into a rounded out socket leaver end and you should have no more problems only the fine adjustment to do now have fun yours anna j

Previously Fritz Wettstein wrote:

Dynodave was talking about the clutch and their's actuator: http://atlanticgreen.com/ndnsclutch.htm, interesting for all AMC-gearboxes

Fritz

yes this is what this clutch is supposed to do but its a pain in the neck most times And I just hate Commando diaphragm clutches even Bob Newby made a six spring belt drive clutch its turned out to be the most best clutch of all time for a norton twins yours anna j