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Handbraaake!


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Hi,

this is a closer look on the small parts for those who are interested.

P1150700-b.JPG.a5d8f500d44a2499eda87cc2a8a7872a.JPG

And this is a last look on what I did 5 years ago to make the handbrake better working:

I put in strong spring from an old clutch in the forked bracket for more elasticity and fitted a spacer to lift up the pivot point of the bowden cable.

P1150703-b.JPG.6d886a6b676422799f7d50ccea353b5d.JPG

The reason for the spacer you see on the next photo from 2015, explaining the issue at the German TR friends forum:

the pivot point of the cable is to deep on the trailing arm, so the leaver is not only pulled but also strongly twisted down!

P1150704-b.JPG.d95277f7b39e2fb21b188412b41315fb.JPG 

This is one of the reasons why I can not recommend to do anything to pull stronger on the cable.

Well, the spacer to lift up the cable was a already very good improvement and served me very well for about 5 years.

Next on the backplate you see the whole dilemma of this §$%)@@@!!* construction.

P1150705-b.JPG.d6420fec78e0d349214493e550cf26bb.JPG 

The cable is not pulled in the direction the brake shoes have to move.

So the (twisted) leaver has to seasaw AND slide on its shaft on the backplate.

Lots of power is lost there digging this grooves, the upper one deeper because of the twisted leaver, never sliding, never pushing the trailing brake shoe.

As told above: §$%)@@@!!*,

and the second reason why I cannot recommend to pull stronger on the cable.

Hope this solves the problem, easy to fit.

P1150715-b.JPG.2bfbe5e214cf00eb3133e4c26f7d60d9.JPG

Sliding the push rod in from above

P1150716-b.JPG.30be011fc69bcc2690daa7b405968e68.JPG

Fix it (with Loctite on the bolt)

P1150718-b.JPG.5144678d9ab82ffaa42b4fb9ab7b2147.JPG

First fit of the cable, outside

P1150720-b.JPG.46cda604fe0205426da0dfdc1312b463.JPG

Inside, needs some "modification" of its lenght

P1150722-b.JPG.3dc7d90a282c297e31643665f73890b4.JPG

Outside end about 30 cm shorter with a new soldered nipple to keep the threaded end on the inside end

P1150723-b.JPG.b4e27a2a9c88561c92afc6dc4d55e0a8.JPG

This was at 18:00, day was over before work finished

P1150727-b.JPG.f5e2e177a5ba919bfb5affb84e65534d.JPG

Perhaps I do some small work later this Sunday.

Ciao, Marco

 

Edited by Z320
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Hi Marco,

This is an excellent description of what looks like a sensible modification! Even more if you do live in a country with mountains!
so solved all the issues on a step-by-step basis. We are all curious about the end-result.

Waldi

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yesterday  I had to go one step back, the part above did not fit,

the drills have been about 10 mm too close to each other

P1150732-b.JPG.c5ef5e1f8428d0cc087f52878058e0c3.JPG

fits well now, works well too

P1150733-b.JPG.690870ada8997d8cc9b552a5127e0915.JPG  P1150734-b.JPG.ae75f37a9f254cd180d36bcbbf9625a3.JPG

seat is in again, drums are on the hubs, tomorrow my lovely wife wants to help me bleeding the brakes

 

Edited by Z320
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Stuart,

you have eyes like an eagle!

Both are from the same BMW model and from the same producer ATE.

But one I own already 3 (?) years from when I wanted to start this project,

the other one I bought 3 weeks ago when I realized they will work.

So they are exactly the same - but the diameter of the tube is 1 or 2 mm different. 

Ciao, Marco 

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Hi everybody,

sadly I have to tell you I my handbrake works worse now.

I guess I know the problem, something I realized when I built it but hoped it works anyway.

Will have to take a closer look the next days.

Ciao, Marco

 

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Hi Marco,

I like the way that you take on these challenges. You obviously know what you are doing but every now and then things do not go according to plan.

Research & development has a great failure rate.

I like playing with electronics but the amount of smoke that I have let loose is mind boggling.  When it all works - Wow. That is to be savoured.

 

Roger

Edited by RogerH
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13 hours ago, Z320 said:

sadly I have to tell you I my handbrake works worse now.

I guess I know the problem, something I realized when I built it but hoped it works anyway.

Will have to take a closer look the next days.

Marco,

I just wanted to let you know that we are here for you, if you would like to share what you are thinking is the problem.?

We know the general principle works, so might we guess the amount of handbrake travel is too great, and that is extenuated by the lack of adjustment in your cross link bar ?  ..which will again be an issue when the brake shoe's friction material wears away.  And taking up the free-play adjustment in the cable, as you hoped, doesn't work because when tight - it then compromises the operation of the hydraulic road brakes &/or causes the brake shoe(s) to move off-centre to the drum.?   

Looking at your photos I see your considering the forces and the lever-arms lengths, but I see no measurements of brake shoe travel  perpendicular to the drum.  I assumed you had these worked out on paper but left the dimensions off the photos for clarity.?   But if not then your geometry may need 'adjusting'.

If my thinking is along similar lines to your own, then the cross link will have to be adjustable, either automatically or else easily accessible from the outside. Do you know of any production-car examples of this system - where this cross-link bar is not adjustable ?  Perhaps you need a slip joint at either end (rather than one end being through bolted) for more free play when released ? 

Your handbrake lever double cable pin modification concerned me because I could not see how it swiveled to stay in line with the cable as the lever was rotated, but again I assumed this is just something that was not clear from the photo.

Hope you are not too frustrated, but see this as a fun part of your challenge.

Please excuse me if I speak out of turn..

;) Best regards,  Pete 

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Hi Roger and Pete,

thank you for your consolation, this no problem for me,

I've got so many projects working - there may also some fail.

Pete, you mainly got it, good man.

The long leaver inside the drum gives benefit to the forces - but needs way to be pulled.

On the Triumph construction the leaver touches the body of the hub after only 20 mm distance - I hoped this is enough, but sadly it is not.

P1150736-c.thumb.JPG.620e621f58d9e642384b57772a158988.JPG

Yes, I could grind it down - but this makes it weak and does not solve the next problem:

I have already some play in the push rod, less than 1 mm - but this is about 4 mm ! lost way on the end of the leaver.

And when I use the TR adjustor the brake shoes move away from each other and the play becomes MORE!

P1150736-d.thumb.JPG.5eda0fb72a41871bf6386c022793189b.JPG

So: this construction only works with a "space saving" hub for maximum way to pull the leaver

AND a self adjusting push rod to minimize the play down to zero (no space for that with the TR hub),

and a drill in the drum to set the adjustor back, and a fixed 2 piston brake cylinder with spring loaded piston

(pressing them out) to have no play in the hydraulic system.

I will have a last look on the BMW parts but this will be a big, not at all TÜV confirm modification.

Probably I go back to my "spacer and spring" improvement and tell some words to this (got a question by PM)

Ciao, Marco

BTW, yes, I know a handbrake with solid push rod: early VWs

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Marco, 

I believe you can easily grind some few mm off from the lever to have more space to the hub. When the push bar, is actually a 6 mm push rod, you can make it adjustable and eliminate play. 6 mm rod should still fit. In modern cars a similar adjustment is required each few 1.000 mls. Try it? You are so close. 
Jochem

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this is what I meant....the pushrods have an aluminium tube (left side) and SS threaded slider with adjustment knob. Every few 1.000 mls the adjustment needs to be checked and the knob is turned pushing the pads out. The size is 6-8 mm in diameter...this sufficient... this push rod can be attached to your lever with a bolt (as you currently have it. and has a fork shape. It just needs to be a 2-piece design with a  threaded adjustment knob....

If this does not work....then I am out of ideas...

Jochem

 

 

RearBrake.JPG.151cbabd76acf5e7fbc81e1c7af149f8.JPG

Edited by JochemsTR
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Hi,

I've been asked, so first I want to tell some details about my "spring and spacer" solution,

this is more or less easy to make for everyone, it served me well for 5 years and perhaps I have to go back to it.

It is a cylinder made of aluminium, 25 mm in diameter, with 2 washers (see later) its 23 mm high over all.

But - its lengh itself works like a leaver and with a flat base it will tip on the trailing arm when you pull the cable.

P1150735-b.JPG.9e990709188eac2dc69bad24ac136ff7.JPG

So - to base the torque and forces as good as possible on the trailing arm

I made the spacer and washer shaped to the trailing arm (d about 120 mm) and put 1 mm paper washers between.

Another 2 mm steel washer I use on top, so at all 23 mm

P1220879-b.thumb.JPG.4f60594295a8f007add3afe67f525855.JPG

For the upper spacer I have a tool to do this very easy and fast, if you have not you could use a rasp.

For the aluminium "washer" I have no tool and had to use a rasp, maybe a standard washer will also be good enough.

But how to fix the bowden cable on it and itself on the trailing arm? Easy if you know but I needed some try and error.

Finally I made the bolt of the thrust block (?) longer with an thearded connector and drilled the spacer inside 10 mm.

P1220880-b.JPG.cfb45db3efa44fd5003b1bd410683b8a.JPG

This are all parts, but a bolt from the bottom you don't get in between the drive shafts and drailing arm.

On top you see the 2 mm steel washer.

P1220878-b.thumb.JPG.fea6e19cb12c321fb2b83614dceb8d8f.JPG

On the trailing arm now the cable points in straight line direct on the brake leaver.

P1220898-b.thumb.JPG.7be75956a3e9b4d425f73fb65cfffe3c.JPG

Due to my lowerded rear axle (adjustable brackets) later I had one problem:

the now higher cables kocked on the car body some times - so I put heating insulation tubes from the DIY market over them.

The spring I use is from an old clutch, this makes the cable more elastic, new bowden cables may also work, I don't know.

P1220925-b.JPG.6e347f74d2bb89009e8291e9ec6d10ce.JPG  P1220909-b.JPG.9c6f3e39d4b4b70ffca72106fce037e8.JPG

That's it - have much success.

Marco

 

Edited by Z320
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Hi Marco,

so the basis of this system is to improve the angle between cable and brake cilinder lever, so you eliminate sideward forces, correct?

And the steel threaded bush inside the aluminium bush is basically a bolt-extension. 
 

I’m surprised it makes such a difference on hand brake efficiency, well done.

I still hope you will find a solution (space) for the BMW parts, it is a very good basis.

Gruesse,

Waldi

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More stuff for the pot....

This is the Triumph GT6 Mk 3 self adusting rear brake that was Girling make.  Stag and Saloon used  Lockheed manufacture.

As the shoes move apart the blade attached to the RH brake shoe, at an angle, not perpendicular to cylinder, stokes and turns the ratchet toothed wheel which is threaded into wheel cylinder.  The thread then screws out of the cylinder taking up wear of the shoes.

 

Cheers

Peter W

GT6 Mk3 Self Adjuster.jpg

Edited by BlueTR3A-5EKT
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Hi Waldi,

first of all I wanted the get rid of the senseless friction on the thrust block 

where the bowden cable is bended in a sharp angle.

Look on your cables after some time, they are lasting and sharp bended on that point.

Second I did nit want to loose forces by the twisted down leaver.

Third, but this is not possible, I wanted the change the piont where the thrust block is bolted on

to get the cable pulling on the leaver in a 90 deg. angle. 

This only works on IRS axle with the leaver in the brake drum.

cioa, Marco

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5 minutes ago, BlueTR3A-5EKT said:

More stuff in the pot....

This is the Triumph GT6 Mk 3 self adusting rear brake that was Girling make.  Stag and Saloon used  Lockheed manufacture.

Cheers

Peter W

GT6 Mk3 Self Adjuster.jpg

Self adjusting is not the problem or solution for the TR brake,

challenge is a long leaver pulled by the cable in a 90 deg. angle AND this without a seesaw in 100% the same direction the brake shoes have to move.

 

Edited by Z320
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Before anyone asks,

the usual leaver extensions in my opinion gives some benefit to the way of movement, this is about "similar" to the springs I use.

But It gives no benefit on the forces and torque - as long you cannot change the point where the thrust block is bolted on.

This is because the "working" force is always and ONLY the one in a 90 deg. to the leaver.

Edited by Z320
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Hi Marco

At the weekend I spent some time getting the handbrake to work on a BMW Mini. The footbrake worked but not the handbrake. There is a single piston operating a calliper on the rear disc brakes. The calliper slides on 2 guide pins which in turn slide through 2 rubber sleeves which fit inside 2 holes on the calliper. Over time, moisture creeps between the rubber sleeves and the alloy calliper and you get some corrosion. The corrosion expands, pushing on the rubber sleeve and the guide rods are then a tight fit. I dis-assembled it all. There was minimal corrosion, less than about 0.5mm, but this was enough to stop the handbrake working. After cleaning it up and silicon greasing moving parts, the handbrake worked perfectly. Couldn't believe how such a small increase in friction completely stopped the handbrake. And this on a modern BMW Mini.

Looking at your photos I can't see any grease on the moving parts. I always put copper grease or brake grease on the 3 dimples on the backplate that the shoes slide on. Also the adjuster faces and the piston faces as well the sliding mechanism for the piston. In the experience I had with the Mini brakes I would recommend ensuring all moving parts are suitably greased. As I say I couldn't believe what a difference it made on the Mini. It sailed through the brake efficiency test at the local garage MOT a couple of days ago.

I must say I am very impressed with your engineering and look forward to the next instalment.

Good luck

Keith

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