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Tr4A Handbrake Upgrade, Temp guage test.


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2 hours ago, stuart said:

But he did like a good screw! ;):lol:

Stuart.

oh Stuart ....................:rolleyes:

 

just couldn't resist could you

 

and you a statesman of this forum too.

 

 

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Hi,

holiday and bad weather outside......

This is the rear brake drum lever, you see the brake shoe to the driving direction is pressed directly on the brake drum,

and the brake shoe to the reverse direchion is pressed my the brake cylinder on the brake drum - if the pivot pin hopefully slides (with friction) on the brake backplate.

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You may indicate this for the best direction to pull on the lever 90° to the lever?

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But indeed the effective lever is the one between the pivot pin and the point the clivis is attached.

So pulling the direction above is about 26° to the wrong direction.

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Your 100% force is only effective cos26° = 90%, while you waste 10% torque by pulling the pivot pin strongly sidewards

AND to the wrong direction, off from the brake cylinder and brake shoe.

F90° is the best direction to pull the lever.

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This is what Archimedes said.

So knowing this you can make your own a sketch and see what you really get with lever extensions

if you cannot change the point where from you are pulling the lever. This will be less than you hope.

Ciao, Marco

Edited by Z320
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The mark one version of the extended brake levers were modified. The main issue was that in order to fit them, you had to extend the handbrake cable to get them to fit. The mark 2 version was altered so there was no need to alter the length of the cable.  I have both the mark 1 and mark 2 versions but never fitted either of them because the handbrake lever modification seemed to work fine. A friend fitted the mark 1 version and it seemed to improve the handbrake but by how much I don't know. The only concern I had was that the handbrake was at its maximum adjustment of the locknut. The mark 2 version is better from that point of view needing no adjustment.

Keith

 

 

 

 

Edited by keith1948
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Hi Keith,

thank you for your sketch, if the dimensions are realistic the benefit would be about 26% - that is already very good - I guess it is less.

You see the "effective " lever 90 deg angled to the force?

To find out exactly a scaled sketch is needed.

_QYqj_lK6jMQ9mFlATVXmVTFHFRXHUFTA8iF6nGL

Your sketch brings me to a different idea:

the torque could be more than double with a completely different lever, a completely different bowden cable

and a special and solid enough bracket on the trailing arm, the bowden cable pointing straight befind and going in a wide loop to the handbrake lever.

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But another problem of the  TR construction becomes serious:

the threaded trust stud on the trailing arm is sadly about 23 mm lower than the lever.

The longer lever is more bended / twisted down.....

And I think with this I'm better out.

Ciao, Marco

Edited by Z320
My bad writing
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This drew a smile on my face as I was browsing through the WSM of a 911 Carrera. Germans are thorough - no matter the task - Der Prozess ! 

 

 

Screenshot 2021-05-02 at 01.34.07.png

Screenshot 2021-05-02 at 01.33.23.png

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One last for those out there who wonder,

according to my phrase "the "effective " lever 90 deg angled to the force".

You can have two looks on the law of levers: with the focus on the lever OR with the focus on the force.

The result "lever 90° to the force" or "force 90° to the lever" is the same.

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Edited by Z320
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Hi Marco

I am happy with your earlier estimate of 26% improvement for the lever extension. Un-modified, the handbrake is not good. The handbrake lever modification was an impressive improvement during the annual MOT test. Well the examiner said it was better then a number of modern cars which begs the question as to why designers cannot get this right. Maybe the newer 'press a button' systems are not so good after all and just a gimmick.

Of course with additional force with the possible modifications it is important to ensure the pivot point and mechanism around the brake cylinder and shoes are kept well lubricated or any advantage could be lost. Also brake fluid on the brake shoes is to be avoided at all costs.

Have you estimated what the improvement is by moving the pivot point on the handbrake lever 11mm? That worked well for me.

Keith

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54 minutes ago, keith1948 said:

Hi Marco

Have you estimated what the improvement is by moving the pivot point on the handbrake lever 11mm? That worked well for me.

Keith

Hi Keith,

I did that modification and with this the handbrake may be more powerful - but with the result of a significat reduction of the way of travel.

And the clevis is like a fork running on block with the handbrake lever much "faster" - in my opinion this can be dangerous.

P1160338-b.JPG.01ca5841dc6c05bc9805383c2bce1fa5.JPG

This needs a exaclty adjustment of the bowden cable and does not work with my VW / BMW modified handbrake

with its VERY long lever inside the brake drum (and all forces mostly 90° to the levers).

P1150551-b.JPG.7bd95f81f962868605b7da8ae647e9dc.JPG

This is why I switched back to the original TR4A design the next momnet without driving the car.

In my opinion the TR engineers missed the moment with the IRS models to use a more modern and effective construction but realised the problems.

So they tricked the customers by only drilling a hole in another position with the TR6.

But no doubt: I love my TR4A.

Ciao, Marco

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20 hours ago, keith1948 said:

The mark one version of the extended brake levers were simply longer but still with same angle. The main issue was that in order to fit them, you had to extend the handbrake cable to get them to fit. The mark 2 version shown in the 2nd diagram below was angled towards the cable so there was no need to alter the length of the cable. The arc of movement is now the same as the original lever but further away from the pivot point X but retaining the arc of movement of the handbrake cable. In theory this should increase the leverage. I have both the mark 1 and mark 2 versions but never fitted either of them because the handbrake lever modification seemed to work fine. A friend fitted the mark 1 version and it seemed to improve the handbrake but by how much I don't know. The only concern I had was that the handbrake was at its maximum adjustment of the locknut. The mark 2 version is better from that point of view needing no adjustment.

Keith

image.png.d234177f22a0ddc1ee4cb9738f9808b4.png

 

image.png.5696868cbfc8aa7b93d6e97b1ada3dae.png

 

18 hours ago, Z320 said:

Hi Keith,

thank you for your sketch, if the dimensions are realistic the benefit would be about 26% - that is already very good - I guess it is less.

You see the "effective " lever 90 deg angled to the force?

To find out exactly a scaled sketch is needed.

_QYqj_lK6jMQ9mFlATVXmVTFHFRXHUFTA8iF6nGL

Your sketch brings me to a different idea:

the torque could be more than double with a completely different lever, a completely different bowden cable

and a special and solid enough bracket on the trailing arm, the bowden cable pointing straight befind and going in a wide loop to the handbrake lever.

 

But another problem of the  TR construction becomes serious:

the threaded trust stud on the trailing arm is sadly about 23 mm lower than the lever.

The longer lever is more bended / twisted down.....

And I think with this I'm better out.

Ciao, Marco

Picking up on Keith's suggestion and Marco's geometry and suggestion "To find out exactly a scaled sketch is needed" .. I was interested to see how effective a "very simple extension bracket" would be ..if it were bolted-on at 90-deg rather than extended straight out.  Like Marco I am considering its mechanical advantage at a cable pull 90-deg. 

Borrowing Marco's photo, with the measure shown for scale, I approximate ; the original lever (red with blue dots every 10mm) its effective length @ 90-degs is 82mm. 

P1220802-c.jpg.7b1c230fa07b34c1136c83fa20aee77d.jpg

After turning the bolt-on extension (measure) through 90-degrees, I then added the blue geometry (with red dots every 10mm).  

Allowing for clearance of the brake cable around the spring, the blue geometry is to the 152cm mark on the rotated scale.  The offset distance between this and the pivot hole in the original brake lever is 28mm.   ie., Instead of Keith's 15mm I looked at 28mm offset.

The blue geometry then shows it mechanical advantage, with the cable pulling 90-deg., to be 99mm.  This is  21% more than original.

P1220802-d.jpg.0e2ff1ba3b48b9c9649798e9937cd981.jpg

It might be made as a very simple bolt-on bracket mod ..without needing dismantling nor welding, and it would make hardly any difference to the amount the handbrake lever (in the car) will pull up.  The same cable pull point on the swinging arm is retained, but I agree with Marco's previous proposition of raising that 23mm higher to avoid twisting the lever down as it pulls.

Pete.  

 

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Hi Pete and Keith,

my intention was never to pull stronger on the levers, because this is (in my opinion) "I can't fix it - give me a bigger hammer".

As Pete points out (from one of my other posts) I found the trust point of the bowden cable is about 22-23 mm too low.

THAT is in my opinion more the problem than the levers.

The cable is angled "up", and a lot of power is lost by friction and the lever is twisted down.

The new IRS axle was the moment the TR engineers should have realised this construction does not work anymore.

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Finally I made a pair of spacer, on the downside shaped to fit the trailing arm perfectly.

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Also the bowden cable is too stiff, so I added a solid spring from an old clutch friction plate to get it some more elastic.

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Without touching anything else (still the old cables and levers from 1967) I was VERY pleased with the result.

The only thing I had to do later was to cover the cables with 9 mm heating insulation tube because they touch the car's body.

I make you both an offer:

I make you Pete, and you Keith (if you own a IRS) a set of spacers for testing.

You only have to look for pair of springs (wire dia. 3 mm, coil dia. 12 mm, coil length 22 mm),

my own ones are not in use anymore but I want to keep them as a reference.

Ciao, Marco

Edited by Z320
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Marco., Thank you for your very kind offer.  Yes please, I would greatly appreciate a pair of your spacers to try on my IRS car.   From seeing your second photograph, with the spacer in place and the line of the free cable, it seems inconceivable that Triumph engineers accepted the cable pull at such an angle.  I have now lifted the back of my car onto ramps, so later today (if it does not rain) I will see this for myself.   I wonder if this angle of pull is the same on the Triumph 2000, from which the TR's IRS was derived.

Can you explain why you felt the cables were too stiff ?  I am guessing it was because the (inside the car) handbrake lever's ratchet is too coarse (pull distance between clicks is quite a lot) so the last click to engage the handbrake fully-on was still a little loose on the brake drum, and the next click couldn't be pulled without having a little spring in the cable.  Perhaps those springs also make releasing the ratchet a little easier because the stretch / movement releases pressure on the pawl.

cheers, Pete.     

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13 hours ago, Bfg said:

Can you explain why you felt the cables were too stiff? I am guessing it was because the (inside the car) handbrake lever's ratchet is too coarse (pull distance between clicks is quite a lot) so the last click to engage the handbrake fully-on was still a little loose on the brake drum, and the next click couldn't be pulled without having a little spring in the cable.

cheers, Pete.     

Hi Pete,

you describe exactly what happens - but the ratchet is not much to coarse.

I have it original in use with very long BMW levers (see later) and have about 6-7 clicks from min to max.

On max I can not even turn the wheel by using 300 Nm, even while the car is jacked.

1st

Wire cables are eleastic like a spring, but they loose their elasticity the longer you have them in use and the more load you give on them.

The senior owner of our local car repair shop told me this becomes also a "problem" on older (20 years and more) modern cars.

2nd

the TR bowden cabel "hose" is pure spring steel spiral, modern bowden cable nowadays all have additional a POM hose inside.

POM is a plastic and elastic under pressure.

Hence (I've been told) it can make sence to put new cables on your TR - but I did not for experiments.

3rd

The lever on the Girling brake drum is very short, and to pull a short lever only little movement is needed.

With a m-u-c-h longer lever you need m-u-c-h more way to pull it - this is also elasticity.

Hence the benefit of a longer lever is more torque AND more elasticity.

Guess this is why so many TR mates are more pleased about the extensions as you can expect from only be focused on the more torque.

I have already pointed on that on another post - but not that detailed - perhaps my fault.

I send you a pair of spacers with all bit and pieces, test them, also in a combination.

That's it, Marco

Edited by Z320
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Hi Marco, many thanks for your kind offer. Can I also have a pair of spacers for my IRS 4A. I might already have some old clutch plate springs. I have just been reading your post on this in Handbraaake from last year and remember thinking at the time that raising the cable would make a lot of sense. I also remember thinking that the Triumph designers probably never had to get at the nut holding the part onto the trailing arm. I have to remove the nut and lift the cable to remove the drive shafts. 

Cheers

Keith

 

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BTW:

the idea of springs in the brake mechanims I have from a look on farming trailers.

This old blacksmiths knew what they have to do without a forum and the www

Edited by Z320
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Hi John, I had a very useless handbrake on my TR4A until I made the following alterations and now the handbrake holds on the steepest of hills no problem.

I decided to make the adjustments that were detailed in issue 314 of the TR Action magazine , page 35 "how to improve operation of the TR4A-6 handbrake", whilst doing this I was having difficulties getting the cable adjustment correct so came up with the following solution, I removed the end cable brackets and nuts on the end of the handbrake cables that fit to the operating arm on the rear wheels and welded the nut to the bracket to prevent it turning, after refitting, it was so easy getting the correct adjustment on the handbrake cables by simply removing the split pin and connecting pin and turning the complete nut/bracket till all the cable slack was taken up, the difference after putting it back together was like night and day. Not the clearest of photo's but gives you a look (the welded nut to bracket is the one on the right).

b.JPG

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1 hour ago, bazyli56i said:

I removed the end cable brackets and nuts on the end of the handbrake cables that fit to the operating arm on the rear wheels and welded the nut to the bracket to prevent it turning,

The use of a square (rather than hexagonal) nut would do the same as your welded nut. 

I noted in Marco's photo (copied below) that a square / 4-point nut is being used as a lock nut.  Whereas if it were place inside the cheeks of the bracket (so that it cannot turn relative to that bracket but was still a sliding fit) then it would offer the ease of cable-length adjustment you propose ..but also allow the use of the spring as suggested by Marco.    

Pete.

On 5/2/2021 at 6:29 PM, Z320 said:

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Without touching anything else (still the old cables and levers from 1967) I was VERY pleased with the result.

 

 

 

 

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Pete, wasn’t a square nut fitted inside the fork bracket as stock on a TR4A? My live axle TR4A has them and I have to rotate the fork bracket to adjust it in/out.

Jim

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12 minutes ago, Tr4aJim said:

Pete, wasn’t a square nut fitted inside the fork bracket as stock on a TR4A? My live axle TR4A has them and I have to rotate the fork bracket to adjust it in/out.

Jim

Yes ..but I wasn't about to tell a German Engineer and otherwise fine n' learned gentleman that he got it wrong ! :D:D

 

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On 4/30/2021 at 12:01 PM, Hamish said:

oh Stuart ....................:rolleyes:

 

just couldn't resist could you

 

and you a statesman of this forum too.

 

 

There used to be a fastener supplier in Coventry owned by a Mr Goode. The company was of course called the Goode Screw Company.

Pete

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16 hours ago, Bfg said:

Yes ..but I wasn't about to tell a German Engineer and otherwise fine n' learned gentleman that he got it wrong ! :D:D

 

I fitted the nuts with my modification they way it is needed to allow the spring to work

Edited by Z320
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^ yes indeed Marco, I only jest.  I did also note the washers and shims used between the lever plate, the cable and the pin - excellent.  

Pete.

 

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^ as a coil spring is compressed one end has to rotate relative to its other. And a square nut fitted inside the cheeks would work against that happening.

Edited by Bfg
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