Author Topic: Broken gear  (Read 954 times)

Offline BSA500

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Broken gear
« on: 20.02. 2024 13:27 »
Rooting around in the box and found a lump of metal and then found where it belonged. God knows when this happened but lucky for me missed all the other gears on his bid to escape

1960 A7 (57 motor to SS spec)

Offline RichardL

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Re: Broken gear
« Reply #1 on: 20.02. 2024 17:53 »
I bet you've already seen this: https://draganfly.co.uk/shop/88093/layshaft-17t-gear/#42-3020U


Richard L.

Offline BSA500

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Re: Broken gear
« Reply #2 on: 20.02. 2024 18:12 »
Yep *smile*. Just need someone to press it on

1960 A7 (57 motor to SS spec)

Online berger

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Re: Broken gear
« Reply #3 on: 20.02. 2024 19:06 »
goodness me at that price my gearbox spares box could make me very rich, just need the buyers at 45 pounds a gear, also at that rate 100 pounds a shaft *eek*

Online JulianS

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Re: Broken gear
« Reply #4 on: 20.02. 2024 20:03 »
I think the broken gear is actually a plunger box pinion, part 67 3196 fitted on a swinging arm layshaft. The swinging arm part 42 3020 has different dogs and the locating circlip is in a slightly different position between the plunger and swinging arm layshafts. 

You can see what I mean in the photo below. Plunger pinion on the left. Swinging arm one on the right.

Offline BSA500

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Re: Broken gear
« Reply #5 on: 20.02. 2024 21:29 »
The gears were actually out of a C12 box which I got years ago and it's gears were hardly worn

1960 A7 (57 motor to SS spec)

Offline Swarfcut

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Re: Broken gear
« Reply #6 on: 21.02. 2024 09:14 »
 I'd agree with Julian. It's a plunger gear. The next layshaft gear (23 teeth) is also different on Plunger and S/A boxes. I assume the drive dog sockets differ to accommodate the different profile of the drive dogs, but in practice there seems little to tell these 23 teeth gears apart.

 Plunger and S/A boxes share layshafts with the same dimensions, but as Julian notes, circlip groove position is different to match the internal profile of the appropriate gear. S/A layshaft has a scroll at the closed bush end. Plunger shaft is plain.

 The circlip is there to locate the gear in production. In the shed with time to play you can press on the gear with care and adjust the shaft end float by its position. So any pair of of these two gears will work on any shaft without the circlip.

  Layshaft and gear have an oil way drilling, so line up the hole on the spline and press the gear on. Worth checking the holes still line up, They may require attention. Layshaft is hollow, so give it a good clean out along with the other oil holes while you're there.

 Previous posts would indicate a lot of gearbox noise in third gear is down to this gearbox pinion, and this is also when the blind bush is under greatest load. Drag's gear is certainly a choice for the well heeled, but their online parts listing conveniently shows what parts are common.

 For those folks with a pile of bits, building a box up from various mix'n match parts is straightforward...bearings  and the seal are the same across the range. Early Longstroke box has slightly different gear profiles so will not mix, but apart from that fixed layshaft pinion and its 3rd gear partner, all other gears are the same on a standard box. So  late S/A gear clusters and layshaft will fit an early Rigid/Plunger casing. Kickstart quadrants interchange, but must be used with the matching ratchet pinion, plenty on the Forum about flat v/s pointy teeth.

 Swarfy.

Offline limeyrob

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Re: Broken gear
« Reply #7 on: 21.02. 2024 09:16 »
A lot of the C11G-C12 gear parts are the same and as they only put out 12hp there is almost no wear.  i have a feeling the clutches are different so the shafts may not interchange.  Need to check part by part.
Slough 59 GF/SR

Offline Swarfcut

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Re: Broken gear
« Reply #8 on: 21.02. 2024 09:24 »
 Correct Rob. The mainshafts are the same along their length, but the clutch is not the same type as a normal Plunger bike. Shaft has a small left hand thread at the clutch end for a lock nut, so may not be the eBay bargain you expect.....and won't fit. Inner and outer covers are Plunger type, main case unique to C range.

 Swarfy.

Offline BSA500

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Re: Broken gear
« Reply #9 on: 21.02. 2024 13:50 »
I had the gears swopped over to the swing arm shafts at the time. That's when there was plenty of engineers in the area

1960 A7 (57 motor to SS spec)

Offline BSA500

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Re: Broken gear
« Reply #10 on: 24.02. 2024 16:12 »
Found a spare layshart high gear yay and managed to draw the damaged one off with a puller so saved some dosh

1960 A7 (57 motor to SS spec)

Offline lauriem

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Re: Broken gear
« Reply #11 on: 12.03. 2024 03:50 »
Tooth decay must be catching.
This is the 19T 2nd gear from my '62 Super Rocket in Western Australia. Total fatigue fracture.
It broke off just before Christmas 2023 and the loose piece stopped me from selecting any gear except 1st or Neutral. That bit only fell out when I dismantled the box to see what was up.
Web searches for  part 67-3302 showed a couple of options but luckily Mikes Classic Cycle Spares  in Queensland had 38 of them in stock (!) at a reasonable price and of course reasonable postage. The rest of the box shows some wear on the gear teeth, some lightly worn bushes and the smaller mainshaft bearing a bit rough, but not bad for nearly 60 years of abuse.
63 SR

Offline muskrat

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Re: Broken gear
« Reply #12 on: 12.03. 2024 11:48 »
G'day Laurie  *welcome*
Lucky I have dentures top and bottom. You must floss more often  *lol*
My plunger box is as built in 1951 bar the bearing and bushes. The Cafe (1957) has done 9 years of racing (only used clutch on down shifts) and about 15 years on the road with no problems at all.
Some are lucky some are not *ex* but in general the BSA g/box is very robust.
Now get over to intros and give us your story.
Cheers
'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
Australia
Muskys Plunger A7

Offline BSA500

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Re: Broken gear
« Reply #13 on: 12.03. 2024 12:54 »
Well mine is now all sorted found a guy to press the replacement gear on for nothing.

1960 A7 (57 motor to SS spec)