TTI gearbox shaft nut

TTI gearbox: does the 40 ft/lb torque figure apply as it would for the stock box? I ask because I found mine loose today.
Second question due to old age: how does one hold the shaft from turning whilst said nut is torqued? Just to add to the fun
my bike has a BNR belt and clutch.

Onder said:

TTI gearbox: does the 40 ft/lb torque figure apply as it would for the stock box? I ask because I found mine loose today.
Second question due to old age: how does one hold the shaft from turning whilst said nut is torqued? Just to add to the fun
my bike has a BNR belt and clutch.

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If you are using the correct retaining screw in the tightest position against the nut face, I fail to see how it can loosen off, so most likely it was never adequately tight, or you fitted the screw in the wrong hole!

I have only ever done mine by holding it with the rear brake and tightening as much as I can with a correctly sized 2" box spanner welded to a square tube about 18" long, until the brake slips. Is that 40lb? who knows?

Will be working on mine in the heatwave in France this week to change the gearing from 'tiny little French circuit' low gearing to 5km Belgian road circuit high gearing! And then at the end of August I will need to change it back. I think it was Charlie Williams who wrote that in the end he gave up racing because he had had enough of repetitive jobs!

Can't see how the belt drive and clutch type make any difference, they are all a pain to remove/replace, including my Norman White one, and yes I have to do that again too, not happy with the spacer I put behind it last year.

The 40 ft. lbs. TTI specifies for the clutch nut ain't enough. First ride on the Manx it came loose. Makes it hard to shift. Without a proper torque wrench at the track tightened it until mouth tasted shit. Hasn't come loose since then. The 80 ft. lbs. specified for the sprocket nut seems adequate.
Can't remember how I locked the rear wheel when tightening the clutch nut. Top gear of course. On modern cast wheels a crowbar locking against the swing arm. Not good on spoke wheels. If locking the rear wheel with the brake is not enough, maybe used a wooden wedge between chain and rear sprocket. Or any other piece of wood.
Maybe torque rods for impact wrenches could be used, never tried.

Looks like I failed Communications 101 here. The nut I was referring to is part-no: 04.0373 clutch centre nut, NOT the
part-no: 04.0070 gearbox sprocket nut.
I agree that 40 ft/lbs isn't enough as it did get loose. Went with blue loktite and 70 ft/lbs. With the blue poop on
figure you gain 10 pounds at least.

Oh THAT nut.

Seeing as there’s no fragile circlip and you’ve got solid flat surfaces fitting together nicely, I see no reason why 70ft lbs + is not perfectly OK.

I did mine to 70, then thought ‘that can take some more’ and it did. Forgot exactly what I did it to though

Actually the back of the clutch basket, being ally, tends to get eaten by the shaft. Kenny at NYC Norton made me a small hardened washer to fit between the shaft and the basket to take the hit. It has worked well. 70 pounds was worrisome as it felt like a lot less. You always have Visions of Disaster when you get up to those torque values on small pieces. I know Real Men snort in disgust at those who rely on the effete Torque Wrench but we used to use them even for spark plugs on airplanes so I have used them ever since.

Didn’t know you had that set up. Washer sounds like a sensible idea.

Washer as well

The torque wrench is a bit overrated. Friend working with design of MotoGP suspensions prefer a certain amount of degrees to get correct tension in the bolts.

Onder said:

Looks like I failed Communications 101 here. The nut I was referring to is part-no: 04.0373 clutch centre nut, NOT the
part-no: 04.0070 gearbox sprocket nut.
I agree that 40 ft/lbs isn't enough as it did get loose. Went with blue loktite and 70 ft/lbs. With the blue poop on
figure you gain 10 pounds at least.

Click to expand...

Ah! That nut! Now the mention of the belt drive makes more sense. And I should perhaps add that I'm pretty sure the TTi gearbox sprocket nut isn't the same as 04.0070, mine is 2" AF spanner size and the TTi sleeve gear may have larger thread and splines, though I appreciate you are only using the PN as location reference.

The standard TTi sprockets are flat and 520 size, mine is non-standard and has a 6mm offset, which is all about getting chain line clearance on a 130 race tyre.

Norman scored well on that one, because when I collected the bike with the belt drive fitted he supplied a clutch sprag with a long lever, saying, 'Oh! You will need this'. I did.

Norman does not rely on the circlip on the Commando mainshaft, so his clutch centre is a modified Commando one that has had a washer welded to the centre, outboard of the splines, and that fits under the nut! To be honest, I don't think this is necessary on a TTi mainshaft as the clutch centre would rest on the step in the shaft!

Have I had that nut come loose?, well actually yes I have, but I think it was because I forgot the Loctite. Tight as I can with handle of sprag in one hand and 18" breaker in the other and blue Loctite seems to be the order of the day.

I could rest the sprag against the footrest and use a 2 foot breaker, but they are lightweight aluminium race pegs, so I don't. With a steel Commando peg, you should use that.

The sprag itself is a simple construction, one steel and one friction plate riveted together, and a fabricated offset handle riveted on.

Does Bob Newby supply one? Or, use a couple of old BN plates (though you probably don't have any unless you have had to replace them). Riveted and inserted into drum and foot on the brake with weight on the tyre should be enough to get a decent torque.

Sometime in the past, TTI changed size on the sprocket nut. Might have been 1 1/2"W to 2" AF. Not certain of sizes.

Mike40M said:

The torque wrench is a bit overrated. Friend working with design of MotoGP suspensions prefer a certain amount of degrees to get correct tension in the bolts.

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The torque wrench is not the holy grail, but when a proper specification is known it insures that the fastener tension is neither too loose nor too tight. Torque to Yield is nothing else but a narrowing of the acceptable fastener tension, and generally brings the fasteners much closer to their point of failure than a torque wrench, allowing either higher clamp loads, smaller fasteners, or cheaper materials. Here's a great explanation;

The torque wrench is not the holy grail, but when a proper specification is known it insures that the fastener tension is neither too loose nor too tight.

Well that is good enough and good enough usually is.