The BSA A7-A10 Forum

Technical => Frame => Topic started by: Rich on 04.05. 2019 20:32

Title: Help fork disaster
Post by: Rich on 04.05. 2019 20:32
HELP I had a really bad day yesterday, having the incorrrect fork sliders on my bike and it being fitted with the deep valance mudguard, as I had received my new stanchions, bushes seals and seal holders.

I decided to remove the the two Y bracket fixing studs from some scrap fork sliders then I removed the flat bracket from my forks using a thin disc cuttter and then some heat to soften the braze, then I welded the stud units in the correct place on my excisting fork sliders.

All good thus far, but the bushes would not slide down pas where I welded, it looks like the weld expanded the tubes inwards and possibly distorted the tubes as well, try as I could I could not cure the problem.

So has anyone any spare fork sliders they can sell me, the type that take the Y bracket for the mudguard and the half clamps for the wheel spindle, there are some on ebay I know, I have tried contacting the seller but have had no reply, looking at his feedback his communication skills is not one of his better traits.
Title: Re: Help fork disaster
Post by: Swarfcut on 04.05. 2019 21:47
 Rich
       I can beat that. Life ain't easy.

  Bid on an eBay fork leg , which arrived with a brazed mudguard mounting stud actually protruding into the bore of the slider, plus an accident dent half way down. "The pictures form part of the description," the usual disclaimer, said the listing.  If its a slider, it must slide and be fit for purpose. No mention of these faults in the listing, so went through the money back guarantee procedure, got the cash back and agreed with the seller to keep the scrap.

 So be prepared for disappointment buying unseen. Rusted bores and banana sliders, to name a couple of things unmentioned. Mis-matched sliders are another trick. Mudguard mounts, spindle mount, front brake hub locating peg all need care to get the right bits.

 Looks like you have now got two sets of scrap sliders. So, keep your new bushes and legs well away from these scraps. They are ruined anyway, so there is nothing to loose by attempting to grind away the high spots and assembling with the old bushes, good enough to rebuild to be able to have short term use until the right parts come along.

 Good luck searching, some look to be made of precious metal these days.

 Swarfy.
Title: Re: Help fork disaster
Post by: TomL on 05.05. 2019 07:17
Hi Rich, it may be worth talking to srm. I saw them at the Stfford show last week and it looks like they are going to be making new sliders. Probably expensive though.
Title: Re: Help fork disaster
Post by: Rich on 05.05. 2019 11:19
Swarfcut, the new parts are sprayed with ACF and repacked in the wrappings and boxed, I have put the old forks together, the lower bush has a few score marks but I am hoping it may slide with the sidecar springs back in, enough for me to finish building the bike,
TomL SRM will be expensive and also may not happen for a year or so, I have put a bid on one set and am watching the other set as it finishes after the one I have bid on, however the refurbished set at a buy it now price of £350 is someone having a laugh, I would rather fit japanese forks and front wheel!!
I will win in the end, any one have a large adjustable reamer?
Title: Re: Help fork disaster
Post by: bsa-bill on 05.05. 2019 11:29
Just out of interest if anyone can advise - might be of help here or elsewhere

I bought a fork slider (Y bracket type) at an Auto Jumble years ago, it was labelled A10 had good threads, looked good and reasonable price, as often happens I missed the stamping on the axle forged bit at the bottom and found when I got home it stamped B31, It's still in my spares box but never got around to measuring it up, so does anyone know how it differs from A10 (if indeed it does)
Title: Re: Help fork disaster
Post by: Swarfcut on 05.05. 2019 12:12
Rich, On your old sliders try a homespun flap wheel, abrasive paper in a split dowel, to clear out rust and crap, polish with a finer grade and then a good wash out. If you have any way of heating up the damaged slider enough to soften the tube, a series of increasing diameter "carrots" forced down may work to push the tube back out. Obviously requires access to a lathe and experimentation. Plus a foolproof way of extracting the carrot.

 Bill.. The ever useful Draganfly parts diagrams show the A10 fork bushes are common to many variants, so you can see that the same slider can have multiple applications, within model types and even different ranges. Fitment depends on mudguard style and mounting type, fore and act lugs for the stays,  type of backplate stop, then the type and size of wheel spindle used.  Basically you can take your choice to mix and match as required, as long as everything below the bottom yoke is chosen by correct fitment.

 Swarfy.
Title: Re: Help fork disaster
Post by: berger on 05.05. 2019 12:36
swarfy my dad got a fairly bad dent out of my tiger cub fork after I came off *eek* by using the method you have mentioned with carrots , the dent was very near the bottom of the slider and he did it in the big lathe without using heat. it wasn't 100% but at least the forks worked without jamming anymore. the dent looked like it had been bashed *bash* with a ball pein hammer but after his effort it looked ok and more to the point I didn't have to ride with a ridged front end *smile*
Title: Re: Help fork disaster
Post by: Swarfcut on 05.05. 2019 12:50
bergs, it is a great pleasure when a bit of lateral thinking comes up with the goods and you beat the system. Well done by your old fella, got you mobile again. Off to a winter barby today, welly boots, sou' wester, blankets. I shall raise a few glassies to all forum members. (Any excuse for the amber nectar)

 swarfy.
Title: Re: Help fork disaster
Post by: Rich on 05.05. 2019 13:14
are the 350 fork sliders the same as the A10 sliders? they look the same except for the seal holders, which look like they take a gaiter, can you look at eBay item No 113711251004 an advice me, thanks
Title: Re: Help fork disaster
Post by: JulianS on 05.05. 2019 13:22
Leave them they are from a C15.

Have you seen these?

www.ebay.co.uk/itm/42-5141-2-BSA-A7-A10-A50-A65-FORK-SLIDERS-A-PAIR-FLASH-STAR-ROCKET-SPITFIRE/352654452993?hash=item521bd7e901:g:0ugAAOSwXcVcyq4v
Title: Re: Help fork disaster
Post by: Rich on 05.05. 2019 13:24
I thought the later C15 used a heavy weight fork assy, that was the same as the B44 and A7/A10?
Title: Re: Help fork disaster
Post by: JulianS on 05.05. 2019 13:30
The earlier C15 competition model forks with full width hub used a smaller diameter spindle and same fork seal holder as the A10. later C15 competition forks used a screw in spindle.

The ones in the ebay item you posted are lightweight forks.

Title: Re: Help fork disaster
Post by: Rich on 05.05. 2019 13:38
Thanks, I put an offer in but he came back with a counter offer so I will leave them, getting a bit desperate, I hate eBay bidding, someone always outbids me then I end up with nowt
Title: Re: Help fork disaster
Post by: RDfella on 05.05. 2019 15:10
Rich – all is not lost. Just think of the things you have to do to repair worn / damaged parts on classic cars.
Your first post tells us you have heat / welding equipment. Here’s what I would do (as per Swarfy’s advice).
Turn up (or get someone to turn up) a mandrel that’ll just fit in the slider (a few thou over bush size). The mandrel needs to be at least an inch long x said diameter. Chamfer both ends. Either weld a good shaft to it or make a thread to take a substantial threaded drawbar – eg 16mm threaded rod.
Now apply red heat to offending area and drive in mandrel. Lightly tap around damaged area with a hammer whilst mandrel is below. Job done.

Title: Re: Help fork disaster
Post by: bsa-bill on 05.05. 2019 15:27
Quote
Turn up (or get someone to turn up) a mandrel that’ll just fit in the slider

yes that's much like the method I used on one fork leg except not having a lathe I used an old stantion and bush
Title: Re: Help fork disaster
Post by: Joolstacho on 06.05. 2019 05:45
Yuck... old shagged fork sliders eh!
Trouble is they get 'belled-out' in the middle by the lower bush so new bushes will never fit correctly.
On BSA sliders I wonder if it's possible to renew the tubing. I recently restored my Velocette sliders, using new seamless steel tubing (I believe it's used for hydraulic rams etc). With the Velo though, the top and bottom lug sections are soft-soldered to the tubing.
Title: Re: Help fork disaster
Post by: Rich on 10.05. 2019 19:47
tried the swaging method, did not work, so I managed to win a pair from eBay, managed to get a mortgage for them, lets hope they are ok, described as superb condition, if they are no good then I will seek Ebays money back guarantee, will find out the week after next, as away next week to get over the stress of parting with so much money
Title: Re: Help fork disaster
Post by: RDfella on 11.05. 2019 09:18
Rich - sorry to hear swaging didn't work, which surprises me. Had that been my workshop I'd have guaranteed good or better than before. But the mortgage *eek* How much did you pay *????*. Ones I saw recently on ebay went yesterday for just over a hunderd £. Can't remember postage.
Title: Re: Help fork disaster
Post by: Joolstacho on 11.05. 2019 09:37
I'm a bit confused in this thread. (Nothing unusual then!...)
Are we talking about swaging the tubing out because it has shrunk/distorted because of welding or brazing of the mudguard lug?
The vast majority of slider problems are caused by wearing and/or 'belling out' of the slider tube so the lower bush is a sloppy fit.
(Or have I got on the 38D to Oblivion when I should have got on the 21A to Farningham!)  :-\

Title: Re: Help fork disaster
Post by: RDfella on 11.05. 2019 10:06
Jools - as I understand the original post, the problem is having welded mudguard lugs onto the sliders, the bushes are a tight fit to get past the area. Swaging in to take up wear from the bushes would be a job not worth the trouble (easier to make new).
Title: Re: Help fork disaster
Post by: Joolstacho on 11.05. 2019 11:14
Yes mate, that's what it sounds like. But IMHO once that sort of distortion damage is done ya'd never get the internal bore accurate enough eh?.
That's why I mentioned the possibility of re-tubing the sliders with nice new tubing.
Has anyone looked into this? As I said, you can do it with Velocette sliders.
Title: Re: Help fork disaster
Post by: Swarfcut on 11.05. 2019 11:33
Rich.. At least you won them, if they were the ones mentioned they looked the part, ready to fit and from a seller who is a long standing eBay member, with an established reputation. Like I said, some are made of precious metal. I think you will be OK, but its always a bit of a worry when you open the box.

   If you have not done already, get yourself a Nectar card and link it to your eBay and PayPal Accounts. The way you are going the points will soon add up, and you can spend the points on eBay and get a few quid off your future purchases.

 Jools... As to the wear pattern, it all take place on the loaded side of the slider and bush, as in use the slider and bush are under  constant sideways load.  So as long as the slider doesn't rattle or knock I would be happy, and accept a little slop, taking into account  the age of these parts and my pussyfoot "cloak of invisibility" riding style.*
   That extra bit to get perfection is the bit that costs the most.
   You could say a few minor rust pits will hold oil and improve the lubrication and have a marginal effect on damping compared to other factors.
   As to re-tubing, if the spindle lugs and oilseal holder thread parts could be salvaged without damage, anything is possible. You need your own toolroom, skill and time. Paying the going rate would make Rich's  look positively cheap, but when serviceable originals have all gone, the Indian or Chinese entrepreneurs will step in. They may have already done so, but I would be a bit wary of these safety critical parts made from re-cycled Oil Tankers.

 In manufacture I would assume the last step would be to bore, hone or broach the final ID, to remove any distortion from welding on the mudguard mounts. The early types look to be brazed on, but even so there is always the risk of heat distortion, so I doubt if this was done to the pre- finished tube.

 Any production engineers in the house?

 Swarfy.

  * Ride with the mind set that no other road user has seen you, and that guy up ahead is gonna pull out, turn across you, run a red light....put your own scenario.   You folks, the survivors, know exactly what I mean.
Title: Re: Help fork disaster
Post by: BSA_54A10 on 11.05. 2019 12:35
Yes mate, that's what it sounds like. But IMHO once that sort of distortion damage is done ya'd never get the internal bore accurate enough eh?.
That's why I mentioned the possibility of re-tubing the sliders with nice new tubing.
Has anyone looked into this? As I said, you can do it with Velocette sliders.

Eeer why not get the tubes line bored then fit oversized bushes .
Done it dozens of times
Title: Re: Help fork disaster
Post by: Joolstacho on 11.05. 2019 14:00
Well it's good to know there's enough meat on the tube walls to line bore them.
(Though I've got at least one pair that would be perilously thin if bored enough to get the 'belling' out).
Title: Re: Help fork disaster
Post by: BSA_54A10 on 11.05. 2019 14:16
A surprisingly small amount of wear makes a massive difference.
Anything much more than ,020" would allow the wheel to move near 6" for & aft when you brake & make the bike unridable.
From memory the last set I got done needed .005" machined ( ,010" diameter ) and that was a wrench out of your hands front end.
Title: Re: Help fork disaster
Post by: chaterlea25 on 11.05. 2019 22:42
Hi All,
How do you bore down past the tapered damper plug that's welded to the bottom of the fork slider?
John
Title: Re: Help fork disaster
Post by: muskrat on 11.05. 2019 23:55
G'day John.
I've never done it but if I had to, the boring bar would need to be shaped the last 2" to clear it. To overcome flex and chatter the bar it would need to be almost as thick as the stanchion.
The next question is how would you measure it with that lump in the road?
Cheers
Title: Re: Help fork disaster
Post by: RDfella on 12.05. 2019 16:00
Musky – exactly my thoughts. With fifty five years mechanical engineering under my belt, I’d really scratch to do that one. How do you centre it or hold it true? The best way would be to take all the lugs off (bar top & bottom fixings) and put in a chuck. But then you’re back where you started. And as you say – with that length of boring bar, what about chatter? Suppose you could bore it in a lathe with a 3” or bigger headstock, but we’re getting a tad agricultural now. Honing is really the only option, but then there’s a danger of taper and, unless it’s a Delapena (which probably wouldn’t be long enough) the hone would likely follow the ovality. Using a pilot is not feasible, as it’d rattle in the worn part.
Title: Re: Help fork disaster
Post by: terryg on 13.05. 2019 08:43
Given BSA's background I imagine the sliders were gun drilled as part of the original manufacture. If that's correct it's presumably not an option for reworking owing to the 'missing' supporting material.
Can someone familiar with the method comment?
Title: Re: Help fork disaster
Post by: duTch on 13.05. 2019 08:50

 
Quote
Musky – exactly my thoughts. With fifty five years mechanical engineering under my belt, ...........

 And with 10 minutes of experience after reading the original post I decided it was gunna be a shitfight so opted out while I was ahead
Title: Re: Help fork disaster
Post by: KiwiGF on 13.05. 2019 13:08
HELP I had a really bad day yesterday, having the incorrrect fork sliders on my bike and it being fitted with the deep valance mudguard, as I had received my new stanchions, bushes seals and seal holders.

I decided to remove the the two Y bracket fixing studs from some scrap fork sliders then I removed the flat bracket from my forks using a thin disc cuttter and then some heat to soften the braze, then I welded the stud units in the correct place on my excisting fork sliders.

All good thus far, but the bushes would not slide down pas where I welded, it looks like the weld expanded the tubes inwards and possibly distorted the tubes as well, try as I could I could not cure the problem.

So has anyone any spare fork sliders they can sell me, the type that take the Y bracket for the mudguard and the half clamps for the wheel spindle, there are some on ebay I know, I have tried contacting the seller but have had no reply, looking at his feedback his communication skills is not one of his better traits.

Does this help? Sliders with local damage has been encountered (and fixed) before  *smile*
https://www.a7a10.net/forum/index.php?topic=7014.msg48835#msg48835

I’m actually trying to sell some fork sliders on fleabay but they are the very early (a7) type with only one mudguard lug so no good to you.
Title: Re: Help fork disaster
Post by: RDfella on 13.05. 2019 16:44
Seems to me we've wandered a bit here. Originally it was about removing a dent, which is not exactly difficult to do. Sorting out a worn slider where the tube bore is oversize is an entirely different matter, which is what we had drifted on to and I was addressing in my last post. That'd be a nightmare of a job and, frankly, easier to make a new one.