EN 16 for brake arm anchor stud

[Michael GilliganParticipant @michaelgilligan61133]

Sorry if my remark was a little terse, Nick

I do have great sympathy with your line of thinking, but these are all in the ‘unknown unknowns’ category and at least we have one relatively simple question that we can consider.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Reading between the lines [always risky] … it appears, from a couple of Andrew’s posts that his preferred solution would be a stepped stud

3/8” cycle thread stepped down to 5/16” cycle thread

AJS used a 3/8 bolt in the original brake, screwed into a steel bush cast into the alloy,

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A stud would be more convenient than a bolt, and the protruding length threaded 5/16 BSC to match the rest of the nuts/bolts on the bike

 

… As always, I am happy to be corrected !

MichaelG.

[old martParticipant @oldmart]

If there is enough material in that area of the brakeplate, I would feel safer with a larger size bolt, and I would use either en19t or en24t which are both a cut above mild steel.

[Gary YeadonParticipant @garyyeadon51936]

That is more like it you can now work through each interface calculating estimates of how each  part is loaded i.e. tensile, shear, bearing and torque values. The linkage rod assembly looks suspect to me.

[Andrew Phillips 4Participant @andrewphillips4]

Hi All, thanks for your comments.  Michael, your picture shows a Honda brake very similar to that which I am using, but I am only using the backplate, modified to fit the AJS drum (see pic). I have a genuine New Old Stock (NOS) bolt in its original packing and it has no markings.  The general body of the kirk say to stick to the original part, and Neil, you are right about the rolled threads.  Mr Honda in his wisdom nas reamed out the first 5mm of the thread in the hole and left the top part of the bot unthreaded, so bolt when tightened bears the shear strain on the whole diameter of the bolt, not on the threaded part as it emerges from the alloy – he must have thought long and hard about this so I will stick to his part, and put up with the mild inconvenience of its location.  The only thing about the bolt that is not as good as the AJS equivalent is that it is screwed direct in the alloy – AMC nearly always used studs for fixing in alloy, or a steel bush – they planned on the parts being taken apart and reassembled for many years so they made it much less likely that the threads would get damaged.  The Honda torque arm looks rather thin – AMC used 3/16 metal in this role; BSA went to even thicker.JJust for interest, I have fitted a BSA 8 inch brake in my Matchless using a new axle made from EN16 to a drawing originally made in Meriden, presumably by someone in his lunchtime for a mate as I don’t hink Triumph ever planned to do this commercially – the AMC brake is a rather puny 7 ins x 7/8 wide, wheas the BSA one is 8 ins x 1 3/8 ins, hence the swap.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the update, Andrew … I’m sure you are on the right track.

For evidence of corrosion problems with bolts into alloy … have a look at my woeful tale about the clutch/flywheel job.

https://www.model-engineer.co.uk/forums/topic/dual-mass-flywheel/page/2/#post-712754

 

MichaelG.

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I would recommend using some Duralac if you can

… BMW obviously didn’t [to my cost, not theirs of course]

MichaelG.

[duncan webster 1Participant @duncanwebster1]

I’m really confused. How do you screw Mr Honda’s M8 bolt into Mr AJS’s 3/8 thread?

 

[Andrew Phillips 4]

On Andrew Phillips 4 Said:

Hi All, thanks for your comments.  […]

The Honda torque arm looks rather thin – AMC used 3/16 metal in this role; BSA went to even thicker.

It does indeed look that way, Andrew … but I think it’s probably fine

Unless there is something very weird happening, it should only ever be acting in tension. [so its twisting and buckling modes are irrelevant]

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

My personal interest now turns to this little detail:

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Crop from my previously posted image:

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I don’t have the wherewithal to demonstrate it at present … but I suspect that the stress-lines in that area were quite cleverly engineered.

MichaelG.

[Andrew Phillips 4Participant @andrewphillips4]

1. Hi Duncan, I am replacing the AJS backplate, with its 3/8 BSC bolt, in its entirety with the Honda item with its 8mm bolt, so there is no overlap.
2. Hi Michael, I do not have the Honda torque arm, but the pictures I have seen for this brake show a simple parallel strap with a single hole at each end. The fastening to the AMC fork is by 2 x 5/16 studs, BSF at one end to screw into the alloy fork slider, BSC at the other to take the fastening nut. I will be making a new torque arm. Interestingly AMC had a simple hole at the brake end of their torque arm, which they swelled out to a teardrop shape in later years after a couple of incidents of the bolt tearing through under heavy braking – this same brake was used for high performance 650s as well as the ‘cooking’ singles that I have got.

[Andrew Phillips 4]

On Andrew Phillips 4 Said:

… The fastening to the AMC fork is by 2 x 5/16 studs, BSF at one end to screw into the alloy fork slider, BSC at the other to take the fastening nut. …

Sorry, Andrew … I think it’s my turn to admit confusion !

I had seen no previous mention of there being two studs in the fork leg.

… We will get there eventually.

MichaelG.

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P.S. __ thanks for the info about the ‘teardrop’ shape … it both supports my hypothesis, and suggests that Mr Honda was a good observer !

[Michael GilliganParticipant @michaelgilligan61133]

Resurrecting this for a brief hi-jack 

I have made my first lumbering steps with the Finite Elephants today !

NASTRAN it is not … but QuickFEM runs on iOS [and I believe there is also an Android version]

The interface is a bit clunky, presumably because the developer put his effort into making the thing work. … and work it does.

It’s essentially 2D, but you can adjust the thickness of the whole model.

MichaelG.

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[duncan webster 1Participant @duncanwebster1]

Im assuming that is a deflection plot, does it do stresses?

 

[Michael GilliganParticipant @michaelgilligan61133]

Yes … it does much more than I currently comprehend.

MichaelG.

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If you’re struggling to find it  …

https://quickfem.com/

 

[Nigel McBurney 1Participant @nigelmcburney1]

I would avoid electro plated bolts,due to hydrogen embrittlement,the correct heat treatment should be carried out soon after the plating embrittlement, some time ago  I fitted some extra load  securing rings to my trailer floor ,the rings   with  4 bolts per ring securing plated nuts and bolts,were supplied in the packing by a respected trailer manufacturer, the bolts were not excessively tightened,two days later one of the bolts had shed its head,it was domed not hex,the trailer was not used in this time,the bolt ead had just popped off. Now doubt the bolt was made in large volumes in some far off land,and if one batch of bolts had been not been heat treated,they were probably mixed up with with other batches and tracing would be impossible. the rings have been well used since and no further bolts have failed.With your safety relying on one bolt it does pay to be careful.Now its obvious there is possibly nowadays a need to improve the braking of a classic bike,but this bike was made in 1954 and consider the extra load on the other parts of bike, ie spokes,forks,fork yokes, steering head bearings and the bike frame.Stick with the original brake and just ride more carefully, In those far off days most vehicle and bike manufacturers were more interested in performance than braking power, My Morris pick up and a mk1 cortina had dismal brakes.

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