Gearbox Noise

Singles, twins and fours.
Mick D
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Re: Gearbox Noise

Post by Mick D »

Hi Simon

I think I would concentrate on the free movement and correct centring of the selector shaft, something causing the shaft to not centre and thus biasing the mechanism resulting in interference, (weak spring, gummy pivot etc.).

Regards Mick
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simon.holyfield
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Re: Gearbox Noise

Post by simon.holyfield »

There's probably 0.5 mm of longitudinal movement in each of the selectors. Some of it comes from here:

IMG_20240124_120850.jpg

There's no perceptible movement in either of the ball bearings. They've only done 5000 miles.

Fifteen minutes work with various micrometers revealed this:
  • Layshaft 2nd bush 1.061” gear 1.065” 4 thou
  • Layshaft 1st bush 1.062” gear 1.0653” 3.3 thou
  • Mainshaft 3rd shaft 0.786” gear 0.788” 2 thou
  • Mainshaft sleeve shaft outer 0.931” 0.940” 9 thou
  • Mainshaft sleeve shaft inner 0.928” bush 0.941” 13 thou
I'd say the clearances are all OK apart from the sleeve gear?
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
Mick D
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Re: Gearbox Noise

Post by Mick D »

Hi Simon

I'd replace the sleeve gear bushes as a matter of course if only to reduce oil passage. Not sure how to rationalise near zero axial on the mainshaft small bearing and 0.040" end float on the shaft, was the clamping to the bearing inner removed when measured?

Replacing the dowels would be a 'no brainer' followed by careful inspection of the selector assembly during re-build.

Regards Mick
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simon.holyfield
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Re: Gearbox Noise

Post by simon.holyfield »

Mick D wrote: Wed Jan 24, 2024 1:28 pmNot sure how to rationalise near zero axial on the mainshaft small bearing and 0.040" end float on the shaft, was the clamping to the bearing inner removed when measured?
No - I hadn't dismantled anything bar the clutch at that point. I'll put the mainshaft back in without the rest of the cluster and have a look - it should be a bit more obvious without grease everywhere.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
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simon.holyfield
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Re: Gearbox Noise

Post by simon.holyfield »

Here's the mainshaft end float Mick, you can see the gap under the nut.

IMG_20240125_135637.jpg

Light bulb moment - the mainshaft doesn't pull up against the bearing, because the end float is needed to allow mainshaft third to spin.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
Mick D
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Re: Gearbox Noise

Post by Mick D »

Hi Simon

Are you sure? that would mean the shaft was free to rotate in the bearing inner. I've not refurbished a BAP gearbox before but what is the function of PN 3118-48 pg 53 of the Draganfly catalogue?

Regards Mick
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paul.jameson
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Re: Gearbox Noise

Post by paul.jameson »

2 questions:
Has the nut on the kickstart end of the mainshaft got a large internal chamfer on the side which should abut the kickstart ratchet?
Is the mainshaft bent?
Paul Jameson
35 LG (project), 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
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simon.holyfield
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Re: Gearbox Noise

Post by simon.holyfield »

paul.jameson wrote: Thu Jan 25, 2024 8:29 pm 2 questions:
Has the nut on the kickstart end of the mainshaft got a large internal chamfer on the side which should abut the kickstart ratchet?
No. There's a small chamfer, sufficient to clear the bottom of the thread on the shaft. I'll turn a shallow depression there, 0.5 mm deep, to reduce the end float a touch.
paul.jameson wrote: Thu Jan 25, 2024 8:29 pmIs the mainshaft bent?
Don't know yet - there's a dead generator preventing me getting to the lathe! Anyone want a 25cc engine with a dead alternator attached? Auxiliary Power Unit for the SQ4 perhaps, or has Bennet cornered that market?
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
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simon.holyfield
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Re: Gearbox Noise

Post by simon.holyfield »

I'm on the home straight with my SQ4 gearbox now. In what may be the second to last trial assembly, I have 1.11 movement on the sleeve gear, gearbox in top, sprocket not tightened up. I'm now ready to make the spacer to move the sleeve gear inboard. I've currently got 2/3 of the sleeve gear spline length engaged with the mainshaft sliding gear splines, and can improve that a bit

What's a good number to aim at?

IMG_20240210_124136.jpg
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
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Re: Gearbox Noise

Post by nevhunter »

That sprocket seems to have been running too far out from the gearbox case. Is the big race in the correct position in the case? Nev
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