Author Topic: Who on earth designed the A10 forks...  (Read 1590 times)

Offline iansoady

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Who on earth designed the A10 forks...
« on: 05.04. 2012 16:49 »
... and why did they make them so weird? I fitted new seals & holders a couple few months ago and for various reasons have only just got back in the shed only to discover that oil was weeping past the threads on one of the seal holders as I hadn't sealed it properly. The fact I had to dismantle the whole lot, including getting that pesky circlip out, then reassembling it, made me wonder why on earth someone designed the stanchions with multiple diameters so you can't just slide the seal over the top end like Norton etc with a single diameter stanchion. Surely it was more expensive to make the BSA pattern with different diameters as there's lots more machining?

Plus why not just screw the seal holder into the inside of the slider rather than the outside, again like Nortons, so it would hold the top bush in place? Quite apart from avoiding aforesaid circlip, there again is less machining and it's so much easier to put together.

Perhaps it's something to do with patents but the actual working bits - bushes, damping mechanism, hydraulic stop etc - are very similar between the two marques.

Sorry if I've offended died in the wool BSA people....
Ian.
1962 Golden Flash (arrived)
1955 Velo Viper/Venom (departed)
2004 Triumph Tiger 955i (staying)

Offline bonny

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Re: Who on earth designed the A10 forks...
« Reply #1 on: 05.04. 2012 17:32 »
i heard a criticism of rolls royce years ago that made me laugh , the saying was that "rolls would never use one part when five would do" , this applies to bsa even more so in my opinion , looking at the mounting  of the oil tank for example , must be well over a dozen parts to attach the thing when a couple of bolts through lugs on the frame would be ample.
have you tried some plumbers tape on the threads ? might do the job.

Offline beezermacc

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Re: Who on earth designed the A10 forks...
« Reply #2 on: 05.04. 2012 17:46 »
Believe it, or believe it not, there should be a couple of turns of thin string around the threads on the fork slider so that when the oil seal holder is screwed down the string makes a seal to prevent oil weeping through the threads. The string is evident when you dismantle original forks.
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline ian davies

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Re: Who on earth designed the A10 forks...
« Reply #3 on: 05.04. 2012 22:06 »
Quite right Beemacc the string works very well, no leaks on my forks after fitting new seals and holders a 1000 miles ago.
ian davies

Offline BSA_54A10

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Re: Who on earth designed the A10 forks...
« Reply #4 on: 06.04. 2012 03:03 »
And it really need to be string, ie jute. Teflon tape will just not do the job.
Some pipe sealants like Stag will also do the job.
As for the design of the forks that can be answered in two words.
Patient & royalties.

Same reason for the 6 spring clutch
Bike Beesa
Trevor

Offline Flatboy 1950

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Re: Who on earth designed the A10 forks...
« Reply #5 on: 06.04. 2012 08:04 »
Out here the 6 spring clutch is referred to as the "Accountants Clutch " suggesting that it was built down to a price and not up to an engineering standard !!  All the stamped steel bits are cheaper to make.

Cheers , Flatboy.

Offline BSA_54A10

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Re: Who on earth designed the A10 forks...
« Reply #6 on: 07.04. 2012 13:10 »
Casting is the cheapest way to form metals into shape.
Pressings are not cheap.
The 6 spring clutch center is very expensive to make and wastes a lot of expensive rolled plate.
A cast center as per the latter 3 or 4 spring jobs would have been a lot cheaper.
Although I have been told that the late bought in centers were actually extruded.
BSA did attempt to make them as a powder pressing but it did not work. although the same technology is used to make a lot of automatic gearbox parts.
Bike Beesa
Trevor

Offline Flatboy 1950

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Re: Who on earth designed the A10 forks...
« Reply #7 on: 07.04. 2012 16:33 »
I understood that castings had to be machined overall , whilst stampings came out ready for use or spot welding together & then used.

Flatboy.

Offline bonny

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Re: Who on earth designed the A10 forks...
« Reply #8 on: 07.04. 2012 18:30 »
Casting is the cheapest way to form metals into shape.
Pressings are not cheap.
The 6 spring clutch center is very expensive to make and wastes a lot of expensive rolled plate.
A cast center as per the latter 3 or 4 spring jobs would have been a lot cheaper.
Although I have been told that the late bought in centers were actually extruded.
BSA did attempt to make them as a powder pressing but it did not work. although the same technology is used to make a lot of automatic gearbox parts.

Beeza also tried to make airgun parts such as sears and trigger blades from powder metallurgy to reduce costs, it didn't work and they had to be replaced. The parts weren't up to the pressures involved.

Offline BSA_54A10

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Re: Who on earth designed the A10 forks...
« Reply #9 on: 08.04. 2012 13:20 »
Check out the price of a ton of scrap ( or secondary foundry ingot ) and compare that to the price of a ton of plate.
The pressed part has to be blanked, pressed, then bent , at least 3 and more likely 5 to 7 operations.
Dies are anything up to $ 100,000 typically around 20,000 to 30,000 each and you need some where around 3 to 7 sets of them.
Dies have a finite life after which they are scrap and once made are almost impossible to modify.
Set up the presses and you are committed to do a run of the particular part and only that part.
Patterns cost around $ 500 to $ 1000 to make ( cope & drag sand moulding) and can be modified at a later date for almost zero cost . They simply get recoated so have an infinite life. The sand is recycled and the machining is done on an auto lathe so once the cams are produced the only additional cost is tool setting and resharpening. You can produce to demand.
When I was in metallurgy, a ton of scrap steel was worth about $ 20 a ton of plate was about $ 300.
There is almost no waste in casting as the sprues & runners get tossed back into the pot .
With the pressings about 1/3 of the steel ends up being scrap.
Bike Beesa
Trevor

Offline Rocket Racer

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Re: Who on earth designed the A10 forks...
« Reply #10 on: 08.04. 2012 22:53 »
I like to consider these all "features" of the marque. a clutch that wouldn't look out of place on a washing machine. full width hubs that would be more suitable for a boat mooring base and sooo many bits that can leak oil if not assembled with string, bits of felt or in some arcane order.
Just sold my only non BSA motorcycle yesterday and back to only having proper old rubbish in the shed.
At least our camshaft is in the right place (at the back of the motor) and we don't have silly external pushrod tubes front and rear like some other inferior makes ;)





A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Offline duTch

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Re: Who on earth designed the A10 forks...
« Reply #11 on: 09.04. 2012 12:14 »
I take it you're referring to the swingarm 6 spring, hey 'cos even though I'm not up on the 4 spring, except for the piccies in the book, the 4 spring seems to have a lot of similarity to the plunger  6 spring, with which I've been playing the last couple of days, two baskets, and both centres are in pretty good shape, but not so much for the outer baskets- useable but a bit rough(pressed metal).
                                   Is that base info correct ?
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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