BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: Milemuncher on 16 May, 2022, 17:23:15

Title: A65 front axle
Post by: Milemuncher on 16 May, 2022, 17:23:15
Hi all,
I know that this has been discussed before but the final resolutions do not appear to detail / advise of the solution(s) or part numbers to fix.
1963/64 A65. Has 1968 TLS brake plate on non-flanged hub (I’ve sorted the brake lining rubbing on spoke ends issue). No idea if forks are correct for year/bike, but look correct according to part lists.
Fork bottom bolts mashed so I’ve re-helicoiled and new bolts ready to go.
Issue is with axle/spindle. Ordered new 42-5824 which should be correct. But this is the same as the one currently on the bike.
Fork sliders are 6 3/4” (centre to centre) apart, and spindle 7 1/4” is correct length.
However, the bolt groves in the spindle don’t line up, hence PO mashed bolt threads. They need to be exactly 6” apart (centre to centre), they are 6 3/16” on 42-5824.
Suggestions/advice appreciated (before consider getting file out).
Title: Re: A65 front axle
Post by: Ellington on 17 May, 2022, 07:42:15
I am no expert, still on my first project. However I have found the Draganfly web site to be very helpful.
They have parts lists for every model year of A65. I looked at the 1968 front wheel and the part number for the spindle is not the one you quoted. You might try phoning them to see what spindle would fit your forks and brake hub?
Title: Re: A65 front axle
Post by: Spaceman on 17 May, 2022, 09:55:58
I've got various A65 fork sliders lying about and can will have look to see whether there is any obvious difference to the axle clamping dimensions.

At face value, because the fork spacing must be the same across the range, the problem must lie with the fork clamps but I would be surprised if the clamp bolts were not on the centreline of the fork tubes?? Out of interest, what do you mean by a non-flanged hub - is this not just the one that came with the TLS brake?
Title: Re: A65 front axle
Post by: Bess on 17 May, 2022, 11:15:01
Hi,
    I have had a similar issue. Cannot remember for sure, I feel the Triumph forks are interchangeable but different so you might need a Triumph spindle. Firstly have you checked the forks are inline and move freely with the spindles you have?

I have 3 different size spindles, 5 15/16", 6 2/16" and 6 3/16" between centres and cant remember which I used in the past.

Best wishes...
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 16:28:33
Thanks all,

The forks are straight (pleasant surprise) with no stiction on movement, although the LH fork seal has blown, likely due to a PO bending it out to fit the old 42-5824 spindle.

Spaceman: The fork bottom clamps are not in the centre line of the forks, they're inset to the inside. The non-flanged hub is the normal 8" full width hub with internal spoke ends - not really designed for the TLS brake plate which has an external flange for the spokes.

I've dragged through loads of sites and have really struggled to find accurate dimensions of these spindle grooves but have now come to the conclusion that I must have the 1968 forks on my 1964 bike so the new stainless steel spindle 42-5824 that I've purchased is now surplus to requirements.

I'm assuming that I'll now need the 37-1641 spindle for 1968 forks (as used on pre-1967 Triumphs?) as it looks like this is 5 7/8" or maybe 5 15/16" between grooves (but can't find these details on any sites selling them). I said 6" above 'cos I tried to measure across the bolts in the bottom of the forks - so very likely 1/8-1/16" out with my eyesight.

All good fun....
Title: Re: A65 front axle
Post by: Spaceman on 17 May, 2022, 16:57:36
I've just had a look at a couple of advertised 37-1641 axles online and scaling from the pictures indicates the groove spacing is ~6.25". It looks as though the issue may be with your fork sliders. I'll have a look at the ones I have lying around and see what can be deduced.
Title: Re: A65 front axle
Post by: JulianS on 17 May, 2022, 17:26:47
Could you post a photo of your forks?

The 1968 forks are significantly different to the 1963/64 ones.
Title: Re: A65 front axle
Post by: Spaceman on 17 May, 2022, 17:40:35
Just measured up a few fork sliders lying in the shed together with an A65! This gave:

Fork centre separation :  6.75"

Fork clamp bolt separation:   6.25"

Clamp outside separation:      7.25"

Spindle length:    7.25"

All the spindles I've looked at including 37-1641 appear to have the 6.25" groove separation. It therefore looks as though the problem lies with the clamps on the fork sliders.
Title: Re: A65 front axle
Post by: Bess on 17 May, 2022, 18:56:07
Hi,
    I have a set of 1970 A65 forks and sliders fitted to a B31, the comparison below:
Title: Re: A65 front axle
Post by: Bess on 17 May, 2022, 18:56:31
last one:

Also, even if you get the grooves correct the brake plate might not locate fully into the slider stop.

Best wishes...
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 19:03:10
Hopefully photos of the forks will be below
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 19:07:57
Bess, as you can see from the pics above, I’ve extended the fork tab to fit the TLS slot

Any idea of the part number for the spindle in your last picture posted?
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 19:32:15
Photo of bolt separation
Title: Re: A65 front axle
Post by: Spaceman on 17 May, 2022, 19:39:00
When I did my measurements, I measured how far the clamp bolts were from the centreline of the forks. It was 1/4" and since the forks are 6.75" apart, the clamp bolts will be 6.75 - 2 x 0.25 = 6.25" apart.

It would be useful to know what your clamp bolt offset is and what your fork centreline separation is to compare with my measurements? From the pics, it's not entirely clear where the main difference is that produces your clamp bolt separation of 6".
Title: Re: A65 front axle
Post by: JulianS on 17 May, 2022, 19:44:43
The forks in question are not 1968 type - photo shows the 1968 type with stronger almost squared shape outside edge of cap and base of fork bottom.
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 20:04:03
Julian, if that is the 1968 fork, you have the 1969 brake plate with the cable down the forks
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 20:44:01
Guys, if the forks are slightly twisted in the yokes, would that increase or decrease the gap between the forks at the bottom, or would this stay the same?
Title: Re: A65 front axle
Post by: JulianS on 17 May, 2022, 21:19:59
Yes that is correct, 1968 damper rod forks with 1969/70 brake, fitted to my A10.
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 21:47:02
Thanks Julian, so I can rule out the 1968 forks….
Title: Re: A65 front axle
Post by: Milemuncher on 17 May, 2022, 22:03:05
Spaceman, I have attempted to measure the offset, but the welds at the bottom of the forks are a pain and the fork bottom protrudes inwards slightly. I’ll have another go in daylight
Title: Re: A65 front axle
Post by: Spaceman on 18 May, 2022, 06:09:11
It looks as though the only possibilities to explain why your clamp bolt separation is ~6" rather than the 'normal' 6.25" is if the fork separation is less than 6.75" or the bolts are more than 1/4" from the fork centrelines.

If you measure your fork separation to be 6.75" then this would imply you clamp bolts are 3/8" off centre rather than the 'normal' 1/4". This would then seem to imply the sliders are not standard.

If, on the other hand, your fork separation turns out to be 6.5" then that would seem to imply they are either twisted in the yokes or the yokes are non standard.
Title: Re: A65 front axle
Post by: Bess on 18 May, 2022, 11:53:17
Hi,
    I have put together some forks with the different sliders, images might help:

Unfortunately there are 4 different spindles listed for the full hub so without knowing the history of yours I guess it is a bit of trial and error. The spindles I have I don't know the part numbers. I am happy to post my selection for you to try and you can return them when you've finished.

Best wishes...
Title: Re: A65 front axle
Post by: Milemuncher on 18 May, 2022, 21:14:15
I’ve managed to grab the assistance of one of my daughters this evening so I’ve offered up the wheel to the forks and taken some pics using the 42-5824 spindle.

I’ve fitted the right hand side perfectly (brake plate), and the left hand side illustrates the difference in groove spacing. As far as I can tell, the forks are not twisted in the yokes and they are the correct 6 3/4” apart.
Title: Re: A65 front axle
Post by: Spaceman on 19 May, 2022, 06:16:47
If the fork spacing is standard BSA 6 3/4" then the problem is that your fork sliders are non standard and the clamp bolt offsets are 3/8" rather than the standard 1/4".

In terms of a possible background to this problem: When the Triumph TLS hub was introduced in 1968, because it was designed for the standard Triumph 6 1/2" fork spacing, BSA had to modify their fork slider end caps to allow them to fit the hub and axle. This mod was done just for 1968 as Triumph then changed their fork separation to match that of BSA so the subsequent TLS hubs fitted both standard arrangements.

It's possible the bike in question has the modified 1968 fork sliders but, as far as I can see, the mod made might have actually reduced the clamp bolt offsets rather than increasing them - both the BSA and Triumph TLS hub axles from 1968 seem to have a clamp bolt separation greater than 6.25" and so would not fit the bike in question.

So the solution to this particular problem would seem to be to either fit standard BSA fork sliders or to machine the current axle to fit or to source an axle of the correct dimensions. Bess looks as though he might have an axle that fits but it is not clear to me what this came off?

Title: Re: A65 front axle
Post by: JulianS on 19 May, 2022, 10:32:40
This may help;

I have compared the clamp bolt off set between the 1968 and the 1962-65 forks, both are the same.

The 1968 bottom clamps are wider than the 1962-65 type making the outside length between clamps 7 7/8 inches.

The inside measurement between the clamps is 5 inches.

The clamp bolt centre to clamp bolt centre measures 6 1/8 inches.

Measurements from 1968 fork with A10 yokes.

The spindle should not stick out past the end of the clamp as in your last photo.

Your forks look like those originally fitted to 1958/59 A7 A10 B31 and B33 plus the Spitfire scramblers up to 1962.

The other visiual difference between 1962/65 and 1968 forks is the socket cap screw which passes through the base of the fork bottom to fix the damper tube.

I suspect your yokes may not be 6 3/4 between centres - could you post a photo of them?
Title: Re: A65 front axle
Post by: Milemuncher on 19 May, 2022, 18:31:22
Thanks all for your posts  :)

Julian - My forks do not have the socket cap screws in the bottom of the forks, so we can now completely rule out the 1968 forks. I’ll see if I can get a clear photo of the fork spacing near the yokes, but when measured (twice now) they’re 6 3/4”. The A7/A10 forks look to have different mudguard fixings from what I have seen on Draganfly (likely generic pics though).

Bess - thanks for your pics. It would be helpful if it was known which bikes your spindles were off as a couple of them are likely to fit. I’m no closer to identifying what I have though.

Spaceman - very likely my solution is to turn a new groove on the new spindle. It doesn’t sound like I’m going to have much luck in identifying which forks I have.

Anyone know a machinist in Brighton?



Title: Re: A65 front axle
Post by: Spaceman on 19 May, 2022, 18:52:52
Machining the axle would seem to be the simplest solution. Since this is only needed to provide clearance for the two clamp bolts, you could probably just file the two flats needed either side of the axle - just need to make them the same depth as the existing groove. It won't really matter if the axle sticks out 1/4" on the LHS?
Title: Re: A65 front axle
Post by: JulianS on 19 May, 2022, 19:28:16
These are 1958/59 A10 forks.
Title: Re: A65 front axle
Post by: Milemuncher on 19 May, 2022, 21:40:12
Julian, they certainly look the most like my forks so far and they have both front and rear mudguard stay mounts on the bottom clamps.

I’d recently looked at A10 fork parts, but they also appear to have the same 42-5824 spindle for the later models?

I’ve re-measured the forks using metric (easier for me) half way down the fork bottoms:
Distance from outside fork edge to outside fork edge = 215mm (8.46”)
Fork diameter = 40mm (1.57”)
Therefore, fork centre to fork centre 215 - 40 = 175mm (6.88”) which is <3mm over 6 3/4” which we could allow for my eyesight.

Title: Re: A65 front axle
Post by: Spaceman on 20 May, 2022, 09:29:01
Unless they are non BSA or Triumph yokes, I think the only two possibilities are fork separations of 6 3/4" or 6 1/2" with these looking to be standard BSA. I measured my fork separations just by measuring from the outside of one fork leg to the inside of the other. Just done this for my A10 and A65 and got 6 3/4" as expected (within a few mm measurement error)!
Title: Re: A65 front axle
Post by: DAVE BRADY on 20 May, 2022, 10:12:30
Hi,

I fitted a complete 1969 TLS brake and hub directly in to late A10 forks.  The spindle fitted perfectly. 

Dave.
Title: Re: A65 front axle
Post by: Milemuncher on 26 May, 2022, 17:56:58
As a final item to this post, I’ve gone with grinding two grooves for the bolts in the new stainless spindle, and voila (with a bit of cursing getting the brake plate position and two grooves lined up) = one front wheel back on correctly.
All I need now is for my Speedo to come back from Ashley at Speedorepairs……I’m assuming it’s going to be a top notch job judging by the time he’s had it (end March)….
Title: Re: A65 front axle
Post by: Milemuncher on 26 May, 2022, 17:59:34
Thank you all for your assistance and guidance - really appreciated :)