Rear Brake Collapse

[djbgreeves]

Help needed. My East Coaster has been enjoying the sunshine and out on several most pleasant rides. Alas, this morning’s play was cut short by a momentary rear wheel lock up followed by a loud bang as I applied the rear brake. I was able to stop safely using the front but on looking down at the rear brake realised it had suffered a major failure. The base plate has shattered exposing the inner parts. Clearly substantial repairs with replacement parts are required. Before setting out on the task I would appreciate any help members can give regarding rebuilding the brake, where to obtain the necessary parts and any ideas on what may have caused the failure. All suggestions gratefully received.

[John Wakefield]

I have never come across this problem before, looks like metal fatigue after all these parts are now over 45 years old, looks like the brake anchor or its bolts are still in place so that did not break. As no new parts are available you will need to source (via GRA/eBay etc) a replacement brake plate for the alloy full width British Hub. These are fairly plentiful as they were used in the trials & scrambles bikes. Make sure you get one with speedo drive locating hole (some of the comp ones were blank), fit a new set of brake shoes (Villiers Services) & re assemble. Looks like you will also need a new brake leaver, I think member Dick Dunkley (01223 844189) may have some of these.

Best of luck

PS I spoke to Dick Dunkley at the Cambridge Show today, he has a rear brake lever but no brake plates. He suggest you try Paul Powell paultrials@yahoo.com

[djbgreeves]

Thank you

Thanks for the advice John, I will get the wheel out and strip it down to see the full extent of the damage and then start ringing up for parts. Hopefully the hub will be OK and I can replace the back plate etc without having to have a rebuild on the wheel.

[Brian Catt]

Do a quick check to see if any spokes are loose, indicating the drum might be ovalled where the collapsing bits locked the wheel.

[John Wakefield]

In order to widen the response to this I posted details and a photo of dbjgreeves problem on the IKBA forum http://www.realclassic.co.uk/messageswide.html which as you will read below had lot more replies than on here.

A Greeves owner has recently had a catistrophic failure of a brake plate on his Greeves 25DC East Coaster (the pic was posted but ommitted from this thread)

Apparently he applied the rear brake normally, it locked up with a bang, resulting on a broken brake plate & bent brake lever. From what can be seen in the pic the brake anchor is still bolted to the swinging arm & a broken segment of the brake plate. The owner is wondering what caused it. The hub is a British Hub alloy one as used on many light weights Greeves, Cotton etc on road & comp bikes. The only reason I can think that would have caused it would be metal fatigue in a 45 year old component.


Re: Rear brake plate failure

Posted by Bob on June 30, 2013, 11:25 pm, in reply to "Rear brake plate failure"
86.21.168.172

Crystal boundary change.
Metal moves all the time trying to get back to its original state.The alloy contains hundreds of millions of crystals all moving about. Thats why turbine blades are grown from one crystal of the metal they are made from.


Re: Rear brake plate failure

Posted by Rich on July 1, 2013, 12:39 am, in reply to "Re: Rear brake plate failure"
84.194.97.29

I'd have thought that a cracking brake plate would start slowly and that there would be a loss of efficiency felt at the pedal before it failed catastrophically.

Did the hub lock first ? Modern bonded linings come loose and ramped up ? A cracked brake shoe ? Even a broken spring jamming unluckily. I think that it will require full dismantling to ascertain cause and effect.


Re: Rear brake plate failure

Posted by Leon Novello on July 1, 2013, 3:37 am, in reply to "Rear brake plate failure"
124.186.242.63

It happens to new aluminium also. Get a brake plate made from steel.

Re: Rear brake plate failure

Posted by Triton Thrasher on July 1, 2013, 6:40 am, in reply to "Rear brake plate failure"
81.153.217.225

Whatever it uses for a torque stay might have come off.

Or maybe that happened afterwards, who knows?

Re: Rear brake plate failure

Posted by Greeves Rider on July 1, 2013, 7:04 am, in reply to "Re: Rear brake plate failure"
90.155.101.14

The torque stay appears to still be attached to swinging arm & a segment of brake plate. You can just see it behind silincer. If I here more from owner after he has stripped it down I will post results. Its not my bike.

Re: Rear brake plate failure

Posted by dic on July 1, 2013, 8:39 am, in reply to "Re: Rear brake plate failure"
86.135.58.47

Metal fatigue due to many repeated cycles of loading is usual reason for metal failure after long period in service (without corrosion).
Fatigue can be seen if there is a distinct start point - maybe at a sharp inside corner - followed by a series of expanding 'dirty thumbnail' surfaces on the crack showing where it has been growing for many cycles of loading. Eventually there isn't enough metal left to carry the load and it breaks. Just like the Comets (aircraft) in the 1950s where the cracks started at the corner of a navigation window and the cycles of load were from pressurising the cabin lots of times.
Backplates usually have big loads added through levers offset to one side so the plates tend to flex sideways, which is not a good thing.
The surface we can see looks shiny and looks like the final break - is there a series of dirty marks in semicircles centred on a start point?
Most metals don't change much with age unless they get very hot.
It it is not fatigue then maybe as Rich suggests above something jammed it up. I hope it isn't fatigue!
How is the owner?

Re: Rear brake plate failure

Posted by Martin G on July 1, 2013, 9:06 am, in reply to "Re: Rear brake plate failure"
81.86.119.31

Looking at the damage to the brake operating arm, I'd suspect that the arm - and thus the plate - has rotated round past the swinging arm after the torque arm or mounting failed, causing the damage as it clouted the swinging arm.

If the plate itself had just failed, I don't think there'd be as much damage to the arm.

I'd start by invsetigating the torque arm / mounting.


Re: Rear brake plate failure

Posted by Matt on July 1, 2013, 9:40 am, in reply to "Re: Rear brake plate failure"
86.27.237.201

I agree with Martin here - the arm has lots of damage - I suspect that something inside the brake let go, pulling the shoes and mechanism round with the drum, and twisting the brake arm. Now that could be a failure of the plate itself, or as others have posted, could be shoe, spring or any other bit of gubbins locking the plate to tteh drum. As the others says you need to inspect the cracks / fractures in the back plate - if they are all new and shiny then it was probably not fatigue in the back plate. I suspect it will be very hard to determine the actual cause of the effect...


Re: Rear brake plate failure

Posted by geoff the bonnie on July 1, 2013, 10:55 am, in reply to "Rear brake plate failure"
86.146.77.146

This is what used to happen when brake linings were very worn and the brake operating cam went over the top locking the wheel.I would go with a bit falling apart in the hub and getting in between the side of the shoe and the hub.Metal fatigue,as Bob describes,is a possibility.Like my snapped crank that was perfect for 42 years before exploding


Re: Rear brake plate failure

Posted by Bob on July 1, 2013, 11:41 am, in reply to "Re: Rear brake plate failure"
86.21.168.172

Yes Heat, Time and Vibration plus a cocktail of Chemicals from the road surface plus a little water.
The Perfect formula for metal fatigue.
As Geoff says down in a thread below any so called Vintage airplane you see in flight now has more likely had every component replaced several times.
It may be the only hammer you have ever had but its had three heads and four new handles.
Check over those bits you trust with your life.
60 year old brake components will kill.

[PeteNev]

Rear Brake Collapse

This could have been caused by the drum having been skimmed in the past to remove excessive wear/scoring allowing the cam to stick on the top or go over centre as the brake linings wear thin as others have said.A couple of times in the past to stop this happening on worn brake drums I have wrapped the cam with thin strip steel the join on the centre of the flat face of cam.If a good job must be done there is no need to weld.This makes the cam makes larger to make up for the wear /skimming of drum
PeteNev

[John Wakefield]

Another way of doing this is to make up sheet steel shims to fit on the cam end of the brake shoes like in pic

[djbgreeves]

I am grateful for all the suggestions and advice coming in on this. I have now got the wheel out and inspected the parts. The back plate has broken into several parts although I still can't see why. The brake arm is in place albeit with a just a piece of back plate hanging on it. The brake linings and mechanism all seem to operate ok. There are no marks inside the hub to suggest something got caught, so it remains a puzzle. There is a small section of the lip around the hub that has broken away but that could be damage from the event rather than the cause. I don't know if a small section missing is a major issue in terms of a rebuild. Looking at the what's involved I can probably fit a new back plate etc. but I think a fitting a full hub and wheel rebuild is beyond me. I would have to find someone for the job but maybe that's the best option anyway - any recommendations on where to go for that are most welcome.

Whilst it is all in bits the sprocket is begining to show signs of hooking so it may be an idea to do that at the same time.

[John Wakefield]

I would not think the small chip out of the hub would be a problem, just remove the broken bit & clean it up with a file. You just need to source a new brake plate, & brake lever. I would start with contacting Paul Powell paultrials@yahoo.com & see if he can help with one otherwise its the usual route ie Wanted ad on here and maybe in OBM or trawl the auto jumbles. I am surprised that one of the comp lads on here has not come forward as the hubs were used on the trials & scramblers.
There is a BH FRONT brake plate on eBay http://www.ebay.co.uk/itm/British-hu...item19dea33357
This wont fit the rear but might be worth contacting seller to see if he has a rear one.

[Phil Hyde]

Cracking up

I agree with the others. The best way forward is to source a replacement back plate of the correct type.

I do know of at least one case of over enthusiastic polishing, I dont mean a quick buff up with Solvol Autosol. But a professional company where the guy was endeavouring to remove deep scratches. This resulted in parts of the brake plate being almost foil thin, weakening the job to scrap.

As a final suggestion, have you tried looking at the broken edges of the casting? Clearly, the recent damage will still be clean with the broken areas almost sparkling. You need to look for any areas that are dirty. This could indicate a previous crack.

Hope you find a backplate. Get the bike back on the road and happy riding.

Phil

[djbgreeves]

Replacement hub sourced

Thanks to John Wakefield's help I have been able to source a replacement hub from Paul Powell which arrived today. Hopefully the rebuild will go well & I can get back on the road before the good weather runs out. The cause of the failure remains a bit of a mystery as I still can't see any obvious issues. One thing's for sure - it is great being in an owners club. Thanks again for the help.

[John Wakefield]

In view of the above incident, I would advise the owner of the 20DC cafe racer special seen at Battlesbridge on Sunday to seriously look to replace the rear brake torque arm with a standard steel one that has not been drilled for lightness. Looking at the pic it may be an alloy one & the large holes dont leave much meat in the metal. A locked up rear brake as djbgreeves has found out is not fun

[riflegreen]

I'm sure the owner/builder of the bike will be along later to address your remarks John , he is a GRA member and forum user .

Chris

[Sprocket]

Greeves Special

Mr Wakefield, we have not met, however your reputation goes before you !

Regarding your comments about the Greeves M/C I took to Battlesbridge on
Sunday. My take on your article would be that you did not attend the show,
however decided to make comment based on a photograph.

The Torque arm you speak of is not made of Aluminium, as you surmise, it
is in fact made of M/S , it is approximately twice the thickness of the
original ,it was machined by me on my mill, all holes are of equal spacing,
it was Chromed, and De-embrittled at 200c . In my opinion it is more that
capable of doing the job.

May I suggest when choosing to comment on other club members machinery,
first base your comments on fact as opposed to sumise, also as a courtesy
contact the member in private with your concerns, rather than on a web site.

Rob Clarke.

[John Wakefield]

Dear Mr Clarke
As I did not know it was your bike I had no way of contacting you to determine the material that the brake torque arm on you bike was made from, in the photo it looked like alloy. I had no intention to ridicule you or your bike but in the light of the recent brake plate failure on the East Coaster, I thought it appropriate to comment on the modified torque arm on as it appeared in the photo.
Ok you say you have made it from suitable material that will withstand the forces involved, but in my experiance (over 50 years) of bikes I have come accross numerous modifications to bikes which have compromised the safety of the machine where such parts have not been made from suitable materials. I trained as a toolmaker in my early working life so am familiar with machining & metal working practice. I remember well a 'proffessional' Hertfordshire builder of Tritons in the late 60's who used soft alluminium to make up engine plates, needless to say several broke.
So I am sorry you have been offended but if it saves someones life, serious injury, or damage to a bike then I think it was well worth the mention.