Problems with the FFS Hi Spec Rear Calipers ?

[Alan_C]

While I’m writing everything in a pleasant fashion I imagine there’s a way of reading it that can make it sound entirely different … one of the problems of the Internet.
Ray

Sorry Ray, I didn't mean to be harsh - but you're right, reading written stuff on the interweb there's no vocal inflection which in normal conversation can change a meaning so easily.

I was huffed off and writing that while waiting for the AA truck to recover me, a brake pipe split spewing my brake fluid everywhere while on the MOT test just after they tested the handbrake which with brand new standard calipers still only achieved 16%, and was unbalanced. New standard Lotus calipers, new handrake cables, new discs and pads with a few hundred miles to bed in too Humph.

This has been a persistent problem which needs a solution, just making the levers longer by some unknown amount, isn't it. It needs to be the correct amount.

Tony - Yes I agree - I presume Bob has some thoughts on this and has applied some logic.

[bobbrown]

I give up!
What bit of "prototype" do people not understand; I’ve already spent about 6 hours trying to get the levers design sorted never mind make the hole accurately.

Some one else can do it because I'm not, I'm out.

[RayD]

I know you’re only kidding Bob,

Or … on this occasion you really have misunderstood me.

The question I asked had got nothing to do with a “prototype”

It was a fundamental question that comes before the “prototype” stage.

I asked the question a month ago ... before a "prototype" was mentioned.

Depending on the answer a “prototype” may not be needed.

Depending on the answer a longer lever may not be appropriate.

Or it might be the perfect solution.

I was asking if anyone had checked what limitations, if any, there were on the existing lever turning further. Anyone can do it with an adjustable spanner.

Someone might have said … “Yes, they had checked - and it will go further than the handbrake lever could ever take it - and without doing any damage - and while doing so it applies more pressure to the pads, it is ideal for a longer lever “

Or they might have said … “with a reasonable amount of pressure applied by hand the lever comes to a “stop” seemingly before the point the handbrake lever would have stopped moving. Exerting any more pressure it feels as if it might break the lever off”

Or they might have said … “it goes so far applying pressure to the brakes then seems to tail off as though an unloading valve had been fitted to guard against the lever being turned too far”

I have no way of telling what the answer is but I’m sure you do by now ... so, just out of interest … what is it?

Ray

[bobbrown]

If you think I was kidding I have news for you I'm not.
Did you think I did not take the implications in to account? but that's all a bit academic now.
If you think there is a problem you can get on and sort it as I'm not, period end of story.

Bob

[Dico]

1. Monty
2. Steve A
3. Alan C
4. A B Munro - Tony Munro
5. Dico
6.
7.
8.
9.
10.

[MPx]

1. Monty
2. Steve A
3. Alan C
4. A B Munro - Tony Munro
5. Dico
6. MPx
7.
8.
9.
10.

[Gazza]

Bob,

Since you fitted the updated hi-spec calipers, you know i have been saving 10p a day in my piggy bank to pay for these levers.

If you think it will improve them, then do it for the boys.

Gazza

[Steve A]

then do it for the boys

Or Beer

[saska]

Have had a think about this. Seems that things should be done in reverse. There are various handbrakes in operation: std SE, later, longer SE, S2 (much longer & angled) -- think these will move the handbrake cables different amounts.
So the handbrake mechanism of the Hispec rears has some angular travel which can be measured in angular degrees. So Off (0) to some maximum (which probably shouldn't be exceeded) -- 100% == some angle.
Now think about the handbrake cables themselves -- they operate in a linear way, not in an arc, which is how the caliper handbrake mechanism works. So what we are looking for is the chord of the arc (the straight line between the beginning of the arc (0) and the end of the arc (100%) that achieves 100% of the caliper handbrake mechanism. So if your car is an original SE then disconnecting both handbrake cables and engaging the handbrake to some full-on position will move the handbrake cable by X amount. If this amount equals the chord between 0 & 100% then the Hispecs should be fully engaged.
length of the arc is: = Radius x angle (in radians)
chord of the same arc is: = 2 X radius X sin(1/2 x angle)
So if we know what the angle is (the hispec handbrake mechanism), and what chord we are trying to achieve (how much the hand brake cable moves) then the Radius tells you how long the handbrake lever should be.
Think this will be different between the original SE and the S2. The std SE will move the cables less so the the lever needs to be longer, whereas the S2 handbrake moves the cables more, so the hanbbrake levers should be shorter.
I'm very sad that BobB has withdrawn his expertise from this project. He persuaded Hispec to fix the leaky rear calipers (FOC) and those that have them are now benefitting from that.
Sorting the handbrake is hard (I thought about it for a long time) and Bob has already said he spent a long time on it -- which I can believe.
All I can do at this stage is provide information on the optimum length of std SE & S2 lever arm lengths. Might be possible to make a lever that provides both SE and S2 functionality -- unless they are too close meaning the lever will bend.
Going to jack up both the SE & S2 tomorrow and find out what the chord length (and therefore the length of lever arm) should be for a std SE and an S2.
Don't thimk I can do anything more.

[bobbrown]

You are still missing the point and putting far too much thought in to the length of the lever so I'll give you a clue.

I did not want to go into the detail as most people are only interested in does it work, not the hows and whys.
It is possible to sit down and work the figures through working from the required clamp load on the disc to the load needed on the lever to get that clamp load BUT if that is in between clicks on the ratchet or just past the one you can get to easily the next one takes more effort than it should.

If you are wondering how it is possible to get from one click to the next when every thing can be considered locked and will not move very much other than may be a few thou, consider the cables as a spring, yes cables have elastic stretch and in our case around 1.7mm/50kg do not forget the lever has a ration of around 5:1 so that equates to 10kg on the lever.

The constraints on the length of the caliper lever is more to do with physical limitations than any thing else, like will it fit into the space and is it strong enough. The angle of the dangle does not enter the equation as long as there is more movement available on either end than is actually required.

Got it? may be not.

Bob

[Elanlover]

You are still missing the point and putting far too much thought in to the length of the lever so I'll give you a clue.

I did not want to go into the detail as most people are only interested in does it work, not the hows and whys.
It is possible to sit down and work the figures through working from the required clamp load on the disc to the load needed on the lever to get that clamp load BUT if that is in between clicks on the ratchet or just past the one you can get to easily the next one takes more effort than it should.

If you are wondering how it is possible to get from one click to the next when every thing can be considered locked and will not move very much other than may be a few thou, consider the cables as a spring, yes cables have elastic stretch and in our case around 1.7mm/50kg do not forget the lever has a ration of around 5:1 so that equates to 10kg on the lever.

The constraints on the length of the caliper lever is more to do with physical limitations than any thing else, like will it fit into the space and is it strong enough. The angle of the dangle does not enter the equation as long as there is more movement available on either end than is actually required.

Got it? may be not.

Bob

I got it.



What I got is that if Bob says it'll work I believe him. That's not to say that everyone else's questions aren't valid or relevant. They are and there should be no problems with seeking more information. For me, its just that what Bob said about most people not caring about the details is true.

[ailwyn]

1. Monty
2. Steve A
3. Alan C
4. A B Munro - Tony Munro
5. Dico
6. MPx
7. Ailwyn
8. Ailwyn
9.
10.

I don't care about the details, just want to get the bloody things working... Not Bob's fault I know, but 2 years and counting since the car was last "driveable"

[RichardK]

1. Monty
2. Steve A
3. Alan C
4. A B Munro - Tony Munro
5. Dico
6. MPx
7. Ailwyn
8. Ailwyn
9. Richard K
10.

[whippit]

Monty
2. Steve A
3. Alan C
4. A B Munro - Tony Munro
5. Dico
6. MPx
7. Ailwyn
8. Ailwyn
9. Richard K
10. whippit

i agree with Ailwyn , i dont care about how and why, my car has been an axle stands for over a year because of these brakes,
it only past the mot last year because i was sat in the car and when i pulled the hand brake i stepped on the foot brake,
the calipers leaked all over my new s2 wheels and stripped the paint,

if bob tells me it will work, thats good enough for me, plus it was only £20 for the levers,
basically i dont give a shite about the banter, all i want is a brake set up that works ,

[naughtytortoise]

IMG_0634.JPG

Bob - loving the new front brakes you fitted recently, transformed the car - a huge thank-you!

[Gazza]

Ed

Very disappointing picture, wheels are still silver!

Gazza

[paulwatkins]

Monty
2. Steve A
3. Alan C
4. A B Munro - Tony Munro
5. Dico
6. MPx
7. Ailwyn
8. Ailwyn
9. Richard K
10. whippit
11. PaulW

[Candles]

Ed

Very disappointing picture, wheels are still silver!

Gazza

but they look pretty good!

[naughtytortoise]

Ed

Very disappointing picture, wheels are still silver!

Gazza

but they look pretty good!

Cheers Candles - and Gazza, I know where you're coming from!!!

[Avonvilla]

Had a service at Paul Matty yesterday. I asked them to give the brakes a good look over as the "new" non leaking rears have had a bit of time on now, they are familiar with the Hi-Spec rear conversion. They made a big point of saying it was the best M100 handbrake they had ever seen ! Very odd how there is so much difference in these, has to be something to do with how they are being installed.