Triumphrat

jimmyj900 · 03-17-2005, 12:17 PM

I started up my bike a couple of weeks ago and had a fairly loud rattle at idle that I traced to the alternator, so I took the alternator out last night (had to drill one stripped torx bolt) and can't find anything wrong! :???:

OK... Anybody experienced this problem -- a rattle with no obvious cause?

*** This is the new design alternator drive with the through bolt on a 2K Adventurer with 16K miles.

*** The alternator drive shaft, bolt and cush drive cup are tight with virtually no play.

*** The alternator is clean, brushes/slip rings good, bearings tight and smooth, cush drive impeller is tight with no lateral play and there's no end play in the shaft.

*** The temperature was 30-40 F at the time and the idle a bit rough.

*** Couldn't hear the rattle at higher RPM due to the offroad pipes. :wink:

The only possibility I came up with is shrunken cush rubbers combined with a low temperature and a somewhat rough idle.

If anyone has an idea I'd appreciate hearing it while I'm waiting for replacement hardware.

Jim

jimmyj900 · 03-17-2005, 12:17 PM

I started up my bike a couple of weeks ago and had a fairly loud rattle at idle that I traced to the alternator, so I took the alternator out last night (had to drill one stripped torx bolt) and can't find anything wrong! :???:

OK... Anybody experienced this problem -- a rattle with no obvious cause?

*** This is the new design alternator drive with the through bolt on a 2K Adventurer with 16K miles.

*** The alternator drive shaft, bolt and cush drive cup are tight with virtually no play.

*** The alternator is clean, brushes/slip rings good, bearings tight and smooth, cush drive impeller is tight with no lateral play and there's no end play in the shaft.

*** The temperature was 30-40 F at the time and the idle a bit rough.

*** Couldn't hear the rattle at higher RPM due to the offroad pipes. :wink:

The only possibility I came up with is shrunken cush rubbers combined with a low temperature and a somewhat rough idle.

If anyone has an idea I'd appreciate hearing it while I'm waiting for replacement hardware.

Jim

SWare · 03-17-2005, 02:05 PM

The rough idle and cold conditions could be making other parts rattle a bit.

Has the bike been starting OK?
No noises, grinding, popping, false starts, etc?

I hate to mention it but the starter sprag can rattle some. Kind of like the alternator.
The drive shaft runs through the sprag so they are semi related. Your later model bike has the improved parts though so I really doubt it. If starting is quiet and smooth then I would say no worries.

stan

SWare · 03-17-2005, 02:05 PM

The rough idle and cold conditions could be making other parts rattle a bit.

Has the bike been starting OK?
No noises, grinding, popping, false starts, etc?

I hate to mention it but the starter sprag can rattle some. Kind of like the alternator.
The drive shaft runs through the sprag so they are semi related. Your later model bike has the improved parts though so I really doubt it. If starting is quiet and smooth then I would say no worries.

stan

MickMaguire · 03-17-2005, 04:32 PM

I hope it's not starting to get a bit of piston slap jimmy - sounds way too low on the milage stakes.... but rattling when cold ....

MickMaguire · 03-17-2005, 04:32 PM

I hope it's not starting to get a bit of piston slap jimmy - sounds way too low on the milage stakes.... but rattling when cold ....

jimmyj900 · 03-18-2005, 07:31 AM

Quote:

Has the bike been starting OK? No noises, grinding, popping, false starts, etc? I hate to mention it but the starter sprag can rattle some.

Good thought! A rattle there would be a possibility, but I've had no cranking/starter problems as would be expected with a failing sprag.

Quote:

I hope it's not starting to get a bit of piston slap jimmy - sounds way too low on the milage stakes.... but rattling when cold ....

A piston slap is another good thought, but that's a different noise altogether and I wouldn't be able track the sound (by touch) to the alternator.

Since everything seems mechanically sound, my working hypothesisis for the clatter is the combination of a rough idle and mechanical slack in the system. With an uneven idle, the instantaneous engine rpm is changing constantly but the inertia of the alternator tries to maintain a constant speed. The low temperature is an additional factor since that makes the alternator bearing seals and lubrication a bit stiffer with higher drag.

The mechanical slack in the system would cause the blades of the cush drive to 'slap' back and forth against the cush rubbers erratically with the 'slap' transferring mechanically through the cush drive and causing the alternator drive gears to clack. The elasticity of the cush rubbers would add a bit of spring to the system and possibly accentuate the clacking.

The blades on the alternator side of the cush joint measure 4mm but I'm measuring a 5mm gap between the installed cush rubbers, so I come back to the cush rubbers being shrunken or compressed since there's no evidence of mechanical wear.

The short-term solution would be to replace them, but a long-term solution would be to build up the blades on the cush drive a bit. That would reduce the amount of whip in the system and decrease the acceleration stresses in the system. I haven't decided which way to go as yet.

Aside from that, I wonder if this might be the source of the broken bolt problem? Excessive stresses induced by mechanical whip and undersized cush rubbers.

Jim

Tumbleweed · 03-18-2005, 08:31 AM

...check the chrome "shield" where the pipes connect to the muffler. These things can rattle quite noticeable if bent when idling. (own experience)

T'Weed

jimmyj900 · 03-19-2005, 09:49 AM

Quote:

...check the chrome "shield" where the pipes connect to the muffler. These things can rattle quite noticeable if bent when idling. (own experience)

Thanks, but this is a different kind of rattle -- a sharper "clank" than the tinny rattle from one of those little shields. (Shared experience...)

Jim

jimmyj900 · 03-28-2005, 12:53 PM

Update...FYI:

Triumph uses the cheapest ***** voltage regulator that I've seen on an alternator. It appears to be a simple three-terminal voltage regulator that tries to maintain a constant voltage on the rotor.

What makes this particularly craptacular is that there's no sensing of the output voltage. No wonder these bikes boil batteries! :evil:

Anyhow, I built up the rotor blades with a couple of layers of tape to see if that cures the rattle. This is a temporary expedient with a high-performance industrial/military tape, so don't try this at home, folks...

Jim