The BSA A7-A10 Forum

Technical => Frame => Topic started by: Rudgeman on 01.08. 2019 12:55

Title: Mainstand pivot wear
Post by: Rudgeman on 01.08. 2019 12:55
Hi - thought some of you might be interested in my approach to fixing this common problem. I've seen a few posts on this from other contributors so I know there are a range of options.


If I'd had my bike completely dismantled my favoured approach would have been to weld up the worn parts of the stand and frame lugs and then drill the hole back to the original centres to 1/2". That wasn't really an option given the time I have available.


The holes, of course, wear egg shaped. All the wear is on one side - so If I simply tried to drill them out and make an oversized spindle, they would not centre on the original centres. So I first of measured the bejasus out of all the holes and concocted a cunning plan. I discovered that a 15mm hole would still leave plenty of meat around the frame and stand lugs and would completely clean up the worn sections. Actually 14.7mm would have done it - but I have a 15mm drill and not a 14.7.

I fitted a burr to my high speed drill and created a 'worn' patch opposite the real wear patches and the same radius from what was the original centre. That took me to 14.5mm across the two wear patches. I then did the same at 90 degrees to both so I had a hole on the correct original centre, roughly round and roughly 14.5mm. I then drilled through with my 15mm drill which left me with a hole still on the correct centre, approx 14.9mm and not as round as I'd hoped. Small wonder - the drill was hand held. So next I got out my expanding reamers and started reaming the hole to be round and 15mm. This is the hardest part - your reamer has to be very sharp and still it's tough. But I persevered and was happy in the end that I had a round 15mm hole on the right centre. I repeated with the other 3 lugs. Of course I was aware of the danger of creating lugs that were on a slightly different angle to eaach other - because all this was hand held and aligned by eye. Nonetheless - I was pleased with the appearance of the results.


Next I turned up a new stainless spindle, a few thou under 15mm. I made it slightly longer than the original and put a slight taper at one end to help it engage the lug bores. I drilled split pin holes in each end - but these are for appearances since I wanted to fix the spindle in the frame lugs. I wanted to do this so the spindle would not turn in the frame lugs and wear them. Instead I wanted the stand to rotate on a fixed spindle and then provide grease nipples in the stand lugs to enable me to lube them now and again.


The frame lugs already had small holes which may have been there for the purpose of grease nipples in the first place - but I haven't seen mention of grease nipples on stands before. Perhaps people who know more about these can correct me. Anyway, I tapped these small holes to 1/4 whitworth and fitted grease nipples.


My fix to prevent rotation of the spindle was to drill a 4.2mm hole through the left hand lug toward the centre. With the spindle correctly located, I then drilled a witness mark in the spindle, removed the spindle and then drilled and tapped the spindle hole to M5. I drilled out the lug hole to 5mm and made a small M5 bolt with a tapered end to help find the threaded hole.


It has all assembled really well. It's a slightly stiff fit in the frame lugs (small misalignment probably), but an easy sliding fit in the stand lugs. The grease nipples are accessible and at first glance the assembly looks original - until you notice the M5 bolt.


The acid test is when I get the front end finished (another saga) and pull the bike up onto its stand - will the rear wheel clear the floor like it should ? I'll let you know.


R
Title: Re: Mainstand pivot wear
Post by: morris on 01.08. 2019 14:09
Reminds me that I have to do mine also...
I was thinking along the same lines as you ;)
Title: Re: Mainstand pivot wear
Post by: RogerSB on 01.08. 2019 16:46
The frame lugs already had small holes which may have been there for the purpose of grease nipples in the first place - but I haven't seen mention of grease nipples on stands before.

My 1960 G/Flash has.
Title: Re: Mainstand pivot wear
Post by: RDfella on 01.08. 2019 20:40
The lugs on my GF were so bad the hole was almost through to the outside. Only answer was to cut the lugs off and weld on some new ones.
Title: Re: Mainstand pivot wear
Post by: Rudgeman on 01.08. 2019 21:06
Thanks for the photos, most informative.

I've just checked again, and indeed there should be two grease nipples. They shouldn't be angled like mine. Further, there should be a tube to shield the spindle in the middle. I'll have to make one. Strangely though, BSA seemed to make no provision to prevent the spindle rotating in the frame lugs.

We live and learn.

R
Title: Re: Mainstand pivot wear
Post by: chaterlea25 on 02.08. 2019 00:46
Hi R
A workmanlike solution *smile*
You will see that the stops on the frame lugs are also worn, the "wings" on the lugs should be symmetrical

When I repaired my completely knackered stand and lugs, I made up a thick walled tube, 1/2in bore to fit between the frame lugs, drilled in the centre for a grease nipple
I welded this in place making a solid  long bush for the spindle
I had much welding and shaping to get the stand pivots built up and solid  *work*
I machined up a new spindle "bolt" with a nut at one end, so I could lock the spindle in the stand relying on the long bush as a pivot  *smile*

My RGS project frame will need new stand mountings to repair it
The RGS lugs are thicker than the 61 Super Rocket but are still worn away to nothing  *sad2*

John
Title: Re: Mainstand pivot wear
Post by: Rudgeman on 03.08. 2019 11:15
Hi John. Thanks for that observation on frame lug ear wear. Looks like I'm going to have break open the welding kit yet. Easier to weld the ears in situ than the bores though.
R
Title: Re: Mainstand pivot wear
Post by: BVSR on 04.08. 2019 12:16
Hi,
I made and welded extra spacers to lugs.

Markku
Title: Re: Mainstand pivot wear
Post by: KiwiGF on 04.08. 2019 22:36
Hi,
I made and welded extra spacers to lugs.

Markku

Nice job  *smiley4*
Title: Re: Mainstand pivot wear
Post by: Peter in Aus on 05.08. 2019 01:54
Hi,
I made and welded extra spacers to lugs.

Markku

Nice job  *smiley4*

Good idea. *good3* I would go one step further (having seen that) and step the new bush/spacer to fit into the old hole.