Fitting gears onto layshaft

pommie john · Aug 31, 2013

I'm replacing the bearings and a couple of gears in my 4 speed Norton gearbox.

On fitting the roller bearing inner race to the drive side of the layshaft, if I tap it fully home it jams the third gear cog up against the fourth gear. ( Third gear needs to spin freely on the layshaft) . I assumed that it would sit against a shoulder so I could knock the bearing race on nice and hard,but it appears not.
I have tapped the bearing race on far enough that it has a touch of clearance and the third gear can now spin OK on the layshaft. Is that right? I would normally want to knock a bearing on as far as it will go, but it only seems to work if I don't tap it on that far.
Have I done it right?

ashman · Aug 31, 2013

Hi John

It has been a long time since I done my Layshaft bearing (1979), if its spinning it should be OK, when my Layshaft bearing blew, a week later I was down Sydney for a week, I went to this shop that was called Racetune I think been so long ago, the owner gave me a tapped roller bearing for the Layshaft, he called it a quick change bearing where the layshaft can be pulled out with the gears still on the shaft, he used it on his racing Nortons to change gears quickly, this bearing has been in my gear box since 1979 and have had no reason to pull it out as my gear box is still going good after all these years of running.

We sill got to arrange that bike ride one day, haven't forgot.

Ashley

pommie john · Aug 31, 2013

The ride will have to wait until the Norton is on the road. ( I've sold my Ducati road bike to fund the conversion of the Norton to road bike). There's a fair way to go. The gearbox is the easy bit. I am going through hassles getting a racer bike registered. Qld say ask Canberra and Canberra don't reply to e mails.

AntrimMan · Aug 31, 2013

pommie john said:
I'm replacing the bearings and a couple of gears in my 4 speed Norton gearbox.

On fitting the roller bearing inner race to the drive side of the layshaft, if I tap it fully home it jams the third gear cog up against the fourth gear. ( Third gear needs to spin freely on the layshaft) . I assumed that it would sit against a shoulder so I could knock the bearing race on nice and hard,but it appears not.
I have tapped the bearing race on far enough that it has a touch of clearance and the third gear can now spin OK on the layshaft. Is that right? I would normally want to knock a bearing on as far as it will go, but it only seems to work if I don't tap it on that far.
Have I done it right?

The third lay gear cogs do not face toward the fourth lay gear. The third lay gear cogs face toward and engage with the second lay gear cogs. I can post some pictures if you want but the OB site has good details already.
I believe if you fit the roller inner race with the top hat against the shoulder on the lay shaft the two gears should not be pinched together. Fourth lay is splined and third lay is bushed. Neither one is supposed to slide along the layshaft by very much but there should at least be clearance so that third lay can freely rotate on it's bushing, just like you stated above. If the gears are pinched together I would believe there is something not correct. If either of these gears are the ones you say you are replacing then they are suspect.
All the best.

pommie john · Aug 31, 2013

When I said third gear cog, I meant the gear itself, not the dogs. It's definitely on the right way round. It's just that if I push the bearing race on as far as it will go it forces fourth gear into third gear which means third has no clearance and can't spin.

I am replacing the fourth gear pair, but when I put the old one back on to check, the same thing happened.

Dkt26 · Aug 31, 2013

pommie john said:
When I said third gear cog, I meant the gear itself, not the dogs. It's definitely on the right way round. It's just that if I push the bearing race on as far as it will go it forces fourth gear into third gear which means third has no clearance and can't spin.

I am replacing the fourth gear pair, but when I put the old one back on to check, the same thing happened.

John I'm in Brisbane mate. If you need a hand. I have done a fair bit recently on my box. Not sure if I can help or not but happy to have a look.
Dave

pommie john · Aug 31, 2013

I'll have to clear up my Man-Cave before I let anyone else look in there.. it's a mess!

I'll see what answers I get overnight and take it from there. I'm Northside.

pete.v · Aug 31, 2013

John, you better get the camera going. Pictures are worth.........well, you know.
I, and many others, have been into the gearbox many timew over, but word alone will offer only assumptions.

pommie john · Aug 31, 2013

pete.v said:
John, you better get the camera going. Pictures are worth.........well, you know.
I, and many others, have been into the gearbox many timew over, but word alone will offer only assumptions.

OK, I'l get that done this afternoon.

concours · Aug 31, 2013

pommie john said:
I'm replacing the bearings and a couple of gears in my 4 speed Norton gearbox.

On fitting the roller bearing inner race to the drive side of the layshaft, if I tap it fully home it jams the third gear cog up against the fourth gear. ( Third gear needs to spin freely on the layshaft) . I assumed that it would sit against a shoulder so I could knock the bearing race on nice and hard,but it appears not.
I have tapped the bearing race on far enough that it has a touch of clearance and the third gear can now spin OK on the layshaft. Is that right? I would normally want to knock a bearing on as far as it will go, but it only seems to work if I don't tap it on that far.
Have I done it right?

You are right to think the race should shoulder up hard.

Dkt26 · Aug 31, 2013

pommie john said:
I'll have to clear up my Man-Cave before I let anyone else look in there.. it's a mess!

I'll see what answers I get overnight and take it from there. I'm Northside.

Me too mate. Red Hill.
Lucky you have a cave. I ride my bike inside every night into my converted sleep out!!!
You ain't seen mess till you've seen my den!!
Dave

Hobot · Aug 31, 2013

Newest human origin theory says we are hybrid between a wild boar and female ape, so pig pens just come natural to many of us. My wife and I decided to screw arranging for strangers and we have struck a peace treaty, she can turn the living room into plant jungle and I can work on my mistress there too.

Seems I ran into this layshaft race jamming cog issue a long time ago. After I scratched like a stumped hog, I noticed that the lay shaft had shift slack on assembly so with outer race fully seated in shell the lay race didn't go that deep in, so I just left race a bit shy of rammed tight on shaft and never looked back. To take up some the excess slack just left a gasket or two out. OK i ran out of gaskets and checked with the real old timers first.

pommie john · Sep 1, 2013

OK, here's the photo. and I think I've found the problem, if not a solution.

The fourth gear measures 0.704" wide, the third gear is 1.148" wide. That adds up to 1.852".

The section of the layshaft that they need to fit on is 1.841" between the shoulder of the splines in the middle of the shaft and the shoulder that the bearing sits on.

So if I knock the bearing inner race all the way on it is hard up against the fourth gear, not hard up against the shoulder of the shaft. This stops the third gear from spinning freely on the shaft.

The new fourth gear is the same size as the old one.

AntrimMan · Sep 1, 2013

Hi pommie John,
I think I remember there is a recess on the dogs side of the third lay. You need to subtract the depth of that to arrive at the assembled stack height before subtracting from the shaft shoulder length. I have one modeled on a different computer and I can take a closer a look in a minute. Maybe I'm wrong.
All the best, fenian AntrimMan.

pommie john · Sep 1, 2013

AntrimMan said:
Hi pommie John,
I think I remember there is a recess on the dogs side of the third lay. You need to subtract the depth of that to arrive at the assembled stack height before subtracting from the shaft shoulder length. I have one modeled on a different computer and I can take a closer a look in a minute. Maybe I'm wrong.
All the best, fenian AntrimMan.

On mine the bush extends out on the recess side and negates the recess.

AntrimMan · Sep 1, 2013

Hi John,
from the model I have:
4th lay 06-1058 measures .697 wide overall.
3rd lay 04-0634 measures 1.134 from outside shoulder to the inside counterbore along the bearing diameter.
I have no model of the bushing 04-0047.
The 04-0025 layshaft measures 1.852 in length shoulder to shoulder on the drive side end.
That leaves .021" axial clearance to float.
I have no access to any original dimensioned drawings.
These are all measured from used MKIII parts I had in my hand while using a Mitutoyo vernier so give or take a couple of thousanths.
This gearbox was working properly, it was opened to swap out the Portuguese ball layshaft bearing.
The roller inner race should bottom against the shaft shoulder.
I would not be comfortable leaving the race only mostly home, although as a decent press fit it should stay where you leave it and there is negligible thrust involved and apparently it was that way before being disturbed.
The 3rd lay must rotate freely.
You may need to make an adjustment ensuring it does so.
Remember to also check and set the end float at the other end since the final position of the roller inner race does influence this.
Al the best.

pommie john · Sep 1, 2013

Thanks for those measurements. I'll have another good look tomorrow and see what I can find.

PeterJoe · Sep 1, 2013

I just so happened to have my gearbox apart, so I took some measurements. I had difficulty accurately measuring the third gear width and depth of the shaft. So, what I did was assemble the layshaft with just the third gear bushing, the layshaft fourth gear and with the bearing race pressed fully on. Also, the bushing that I used for measuring is brand new.

I was able to put a .007 inch feeler gauge between the bearing race and the layshaft fourth gear. This insures that the bushing is free to revolve around the layshaft without binding. Then I assembled the layshaft with the bushing and the third gear along with the layshaft fourth gear. Holding the layshaft fourth gear up tightly against the bushing, I was able to put a .014 inch feeler gauge between the layshaft fourth gear and the layshaft third gear. This would of course insure that the gear is free to revolve around the bushing.

The edge of the bore of the layshaft third gear may need to be dressed so that the bushing may freely pass all of the way through the gear. Otherwise this may cause some gear binding. I hope this information is somewhat useful.

This is a layshaftt with bearing pressed fully on and .007 inch end play

Fingers pushing layshaft fourth gear tightly against the bushing I was able to measure .014 inch end play with the layshaft third gear

pommie john · Sep 1, 2013

Great information thanks.

I'm off to the Norton shop this morning and I'll ask if I can measure a new layshaft and look at the bush length etc.

John

pommie john · Sep 1, 2013

Thanks for all the help everyone.
I went and bought a couple of bushes today including the layshaft 3rd gear bush. This bush is 25 thou narrower than the one I took out. That made all the difference and now it all fits perfectly. With the bearing race fully home I have 12 thou clearance between third and fourth gears and obviously third spins freely now.

I am guessing that many of the parts in this box were cheap pattern and not very well made. The fourth gear was marked RS which Andover Norton say was a cheap pattern part and maybe some of the bushes were too.

Anyway, all good now.

Thanks again.

Fitting gears onto layshaft

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