84 Reynard FC question

[Bill Manofsky]

I recently bought an 84 Reynard FC.

Should the front brake master cylinder be closest to the accelerator?

In looking at photos of other cars, it appears that the front brake master cylinder is closest to the accelerator pedal.

However, on mine, the rear brake master cylinder is next tot he accelerator pedal. Are mine reversed?

The fact that the lines are new and the fittings are aluminum tells me something is not right.

[Gary_T]

On my '84, the front master is beside the accelerator.

I don't know that it matters, other than the bias bar moving the other 'way' respectively.

Gary

[Bill Manofsky]

hanks or the quick response. The brake pedal is actually offset towards the accelerator where it is welded to the slide tube for the bias bar. I am assuming that yours is the same.

I am wondering if Reynard did that to also force more bias to the front, or was it just to get the pedal closer to the accelerator....

when I push on the brake pedal, the cylinder closest to the clutch pedal gets all the load no matter how far towards the accelerator I adjust the bias...

[Bill Manofsky]

I am going to reverse the cylinders, bleed the brakes all around, and take the car out to a track day to test the brakes.

This is the kind of stuff that drives me bonkers....

[Bill Manofsky]

My other concern is that the bore diameter on the front cylinder should be bigger than the rear?

[Gary_T]

You may be right about the offset - I never thought of that. I'll take a look at / picture of mine in the next couple days.

The master bores are different, but I don't recall the sizes off hand - I'm sure a search of Apex would bring up the typical setup.

Gary

[Bill Manofsky]

Many thanks for the help.

[Bill Manofsky]

Gary,

Here is a photo of mine showing the brake pedal offset towards the accelerator pedal. I think they did that to allow better heel to toe, not so much as to induce more bias to the front brakes.

Bill

[Bill Manofsky]

Gary,

Here it is that I live in California and yet have two formula cars heavily influenced by Canada...the Reynard, which is mostly found in Canada and the upper midwestern US, and my 1980 Lola T540E FF that used to be a school car at MOSPORT.

The Lola was bought by a girl's school in Halifax and converted to an electric car. It ended up here in California somehow and I am now bringing it back to FF livery.

I will put a Canadian flag sticker on both.

Bill

[problemchild]

A brake bias pedal assembly is a mechanical function that has no left/right or front /rear orientation until cylinder bores and brakeline routing is applied. Most cars I see have the front brake cylinder more to the middle of the car which gives more symmetrical presentation of brake lines and allows for common brake lines either side. I would think that doing the common shop test of turning wheels with the brake pedal depressed to a point that the fronts are just stopped and the rears turn with drag, would be adequate to confirm the bias mechanism was within working range.

[Bill Manofsky]

Thanks. I will do that test.

I most likely will take the master cylinders out to inspect the bore diameters.

This is not the only thing I have found bass-ackwards with this car. I think one of the previous owners was mechanically challenged, so i am just going to redo everything.

This is something I just noticed yesterday as I am building the car back up.

It is just that from most the the pics I have seen from 84 Reynards, the rear master cyl is in the middle.

[Steve Demeter]

Just My Humble Opinion, but the blue tee looks like aluminum. I would suggest that you rteplace it with a steel one for safety's sake.

[Bill Manofsky]

Just My Humble Opinion, but the blue tee looks like aluminum. I would suggest that you replace it with a steel one for safety's sake.

yes that mistake from the previous owner is already noted in my initial posts. It will be removed....that was the first red flag, then I noticed yesterday that the brake lines had been reversed too.

This car will not hit the track till next year. So I have more to do on it.

[problemchild]

I have heard of people insisting on steel fittings for brake calipers and external areas that may catch rocks and debris but why inboard. Are aluminum fittings not stronger than the plastic brake lines we are running to them? I don't know the answer. Just wondering as I never understood this theory that we need steel fittings on brake lines ..... I can cut a braided brakeline with side-cutters but not an aluminum tee, so how is that different?

[Bill Manofsky]

I have heard of people insisting on steel fittings for brake calipers and external areas that may catch rocks and debris but why inboard. Are aluminum fittings not stronger than the plastic brake lines we are running to them? I don't know the answer. Just wondering as I never understood this theory that we need steel fittings on brake lines ..... I can cut a brakeline with side-cutters but not an aluminum tee so how is that different?

I think I am best to answer your question. I am an aerospace engineer with a minor in metallurgy. I designed flight structures and pressure vessels that flew on the space shuttle.

First of all , you can cut the steel brake line with the side cutters because the wall thickness is thinner. But what you did was compare the shear strength of the two pieces and not the burst strength.

I can assume that event though the wall thickness of the aluminum T is greater than the wall thickness of the steel tube, the yield strength and ultimate tensile strength of the aluminum may be to where the cross section of the T does not have the same burst strength of the steel tubing let alone an equivalent fitting.....

In fact the aluminum T looks like it has been machined the same dimensions as a steel T... The Ultimate Tensile strength of 6061-T6 aluminum is 45,000psi where the Ultimate Tensile strength of A286 stainless is 1,500,000psi. So an aluminum T made to the same dimensions as a steel T is much weaker. So the T is the weak link that will burst first.

In fact you can possibly make a T out of a high hard aluminum alloy that has the exact same burst capability of a steel fitting. But it would most likely be 1.5 times thicker and thus not allow for the same size thread. Same goes for scuba tanks..you can use either a steel 72 or an aluminum 80. Both can carry 3000psi. But the wall thickness of the aluminum 80 is much greater.

The other factor that is most dangerous that everyone overlooks...fatigue. Aluminum has much less fatigue carrying capability than steel. Much like if you bend a coat hanger enough times it will eventually work harden and break.

So I would tend to assume the reason why Aeroquip, Earls etc don't recommend aluminum fittings in brake lines is that they do not have the burst strength to carry the load and also the fatigue life to handle multiple repetitions. I can also assume they burst tested their fittings to prove all this.

[problemchild]

But is brake pressure not in 3 digit values?
You compared aluminum tees to steel tees and offered expected values, but what about aluminum tees to braided brakeline or ferruled connections or chinese crimped connections?
Not quite sure what the checkered flag means. Is this a contest?

[Bill Manofsky]

But is brake pressure not in 3 digit values?
You compared aluminum tees to steel tees and offered expected values, but what about aluminum tees to braided brakeline or ferruled connections or chinese crimped connections?
Not quite sure what the checkered flag means. Is this a contest?

I have not ever measured brake pressure to know if it is in the three digits or more. Triple digit braking pressure that you are talking about is most likely static pressure when someone lightly puts the brake on. When they slam on the brakes it could go much higher and burst the line.

Somewhere in that aluminum T the wall thickness is very thin due to tolerances and machining variances.

The Ultimate tensile strength for material is in PSI...pounds per square inch. So one square inch of the material can handle 45,000 pounds. But the cross sectional area of the thin wall in the fitting and the tubing is much less. so it takes less load to make it fail. You can calculate it yourself. It is a simple ratio. Take one square inch and divide it by the cross section of the the thinnest part of the fitting...you can do that yourself.

Trying to give an explanation of stress analysis over Apex speed PM is not very efficient.

I suggest that instead of trying to calculate the answer that you set up your own fatigue analysis test bench and watch all the stuff you describe burst after 50,000 or so cycles. This is what is done in industry by the people who design this stuff...except the chinese who are counterfeiting everything.

I always put a thumbs up and a checkered flag at the end of my posts. Just trying to always be a cheerful person.

[BeerBudgetRacing]

But is brake pressure not in 3 digit values?
You compared aluminum tees to steel tees and offered expected values, but what about aluminum tees to braided brakeline or ferruled connections or chinese crimped connections?
Not quite sure what the checkered flag means. Is this a contest?

When I was diagnosing a problem on a 240z the pressure was in the 1500 psi range. The problem was we were getting around 800 and not stopping

New Wildwood master was defective...

[gcoffin]

i think your problem is in your bias bar. Changing the location of the front and rear masters will not fix this. Nor will changing the bore diameters.

I cannot tell you how many times I have seen mis aligned/mis adjusted bias bars.

Before doing anything I would confirm both brakes front and rear work.

Next I would put the car on stands and actually test the brake bias...with the fronts just locked you should be able to turn the rears with resistance.

You need to think of the bias system as a square the shafts must be the same length and parallel. The distance between the shafts at the bar must be long enough to allow the lever arm that is the bias bar to actually work as a lever and not bind....yours looks tight.

If this does not solve the problem disassemble, clean and check everything is moving as it should

My cars all have the front master in the center just like yours.

As for bore size I have seen every combination. It is a volume issue relative to each system meaning check what your calipers are front and rear are they the same as on my Mygale or different like on my Swift. It will effect pedal effort not how well the brakes work.

[problemchild]

i think your problem is in your bias bar.

There has not been a problem identified, other than Bill does not have confidence in the previous owner's work, based on parts used when cleaning up the car. That lead to a discussion based on whether certain part standards were "overkill" or acceptable.

FWIW, Our F2000 car, in high downforce configuration is generating about 600 psi of front brake pressure, and about 500 in low downforce configuration. Our F1600 car is much less. I don't know that these numbers are real or accurate, as we are only comparing our own apples to our own apples, but they are not in the millions, or even 10s of thousands. I checked and I don't have any aluminum brake fittings on my Reynard, although I do have aluminum brake calipers. I personally have a lot more concern about the integrity of my 33 year old, thin-wall mild-steel chassis and suspension components. If anyone has any anecdotal stories about inboard aluminum brake fittings bursting, please share. Cheers!

[dogrings]

The theory of banning alum brake fittings csme from some professionaly maintained F/Atlantic and Formula 3 cars. As Chief tech inspector for VARA and HSR West, we found that someone does a bolt check on th car looking for loose anythings, they put a wrench or 2 on the fittings and give the nut a slight turn to see if it is tight. and on to the next one.
Next event same again, and again. After a while the fitting fails between the alum threads and the necked down area closer the hex or "T" part.
There is no inspection of this failure other than the feel of a stripping thread when torquing it up. It has absolutely nothing to do with tube, nut design or nut material or internal pressure.
I have personally found this on Fv, FF1600, my Formula 3 and Formula B, and many production cars. The March FF's we built in 1972 all had Steel or SST fittings from the caliper to the master cyl.
Race VARA bring SST or Steel brake fittngs!!!! Any questions?
wtmitchell28@yahoo.com

[gcoffin]

Actually the problem is the perceived lack of rear brakes no matter how much adjustment is made to the bias bar. The solution is to confirm the brakes work and then test the bias adjustment. If there is a problem then you trouble shoot the bias bar, not move or change the relative bores of the master cylinders. The Aluminium vs steel discussion is irrelevant as he is going to change to steel regardless.

If however it is decided to change the location of the master cylinders and there is a problem with the bias bar, all the braking will go to the rear ( as the rear is now the front) which will again make the steel vs Aluminium discussion instantly irrelevant.

[Bill Manofsky]

The theory of banning alum brake fittings csme from some professionaly maintained F/Atlantic and Formula 3 cars. As Chief tech inspector for VARA and HSR West, we found that someone does a bolt check on th car looking for loose anythings, they put a wrench or 2 on the fittings and give the nut a slight turn to see if it is tight. and on to the next one.
Next event same again, and again. After a while the fitting fails between the alum threads and the necked down area closer the hex or "T" part.
There is no inspection of this failure other than the feel of a stripping thread when torquing it up. It has absolutely nothing to do with tube, nut design or nut material or internal pressure.
I have personally found this on Fv, FF1600, my Formula 3 and Formula B, and many production cars. The March FF's we built in 1972 all had Steel or SST fittings from the caliper to the master cyl.
Race VARA bring SST or Steel brake fittngs!!!! Any questions?
wtmitchell28@yahoo.com

Wayne,

Thanks for the input. You just brought of a very valid point about another overlooked kind of fatigue that appears, from your experience, to cause more failure than the cyclical fatigue of drivers stomping on the brake pedals. This is the repeated tightening of bolts and fittings.

Fatigue is a bigger cause of failure than tensile or shear. It is also very insidious in that people ignore it....or worse yet, don't understand it.

So the reason why perfectly new looking parts such as motor mounts are removed and scrapped from helo copters after a specific service life. Helo's are essentially vibration machine. For this very reason they are very expensive to maintain.

Thanks,

Bill Manofsky

[Bill Manofsky]

Actually the problem is the perceived lack of rear brakes no matter how much adjustment is made to the bias bar. The solution is to confirm the brakes work and then test the bias adjustment. If there is a problem then you trouble shoot the bias bar, not move or change the relative bores of the master cylinders. The Aluminium vs steel discussion is irrelevant as he is going to change to steel regardless.

If however it is decided to change the location of the master cylinders and there is a problem with the bias bar, all the braking will go to the rear ( as the rear is now the front) which will again make the steel vs Aluminium discussion instantly irrelevant.

All points well taken.

I just want to take the car back to the original setup and work from there. It might all come together better than truing to make it work backwards.

Thanks,

Bill

[Bill Manofsky]

The theory of banning alum brake fittings csme from some professionaly maintained F/Atlantic and Formula 3 cars. As Chief tech inspector for VARA and HSR West, we found that someone does a bolt check on th car looking for loose anythings, they put a wrench or 2 on the fittings and give the nut a slight turn to see if it is tight. and on to the next one.
Next event same again, and again. After a while the fitting fails between the alum threads and the necked down area closer the hex or "T" part.
There is no inspection of this failure other than the feel of a stripping thread when torquing it up. It has absolutely nothing to do with tube, nut design or nut material or internal pressure.
I have personally found this on Fv, FF1600, my Formula 3 and Formula B, and many production cars. The March FF's we built in 1972 all had Steel or SST fittings from the caliper to the master cyl.
Race VARA bring SST or Steel brake fittngs!!!! Any questions?
wtmitchell28@yahoo.com

Also another very valuable point...there are two ways to field test components..the first way is to set up a test lab and perform burst, shear, tensile and fatigue testing to failure on all parts. A proper lab would also simulate the repetitive torquing of the fittings as Wayne mentions.

The other way is to put the parts out in field testing on an actual prototype. Much like the car companies performing track testing on next years model. It is my experience from the aerospace industry and from racing that field testing brings up many more failure scenarios that could not be imagined for lab simulation. This is the equivalent of what Wayne is talking about and why his years of experience and observations in the "real world test laboratory" is so valuable here. It is safe to assume that it is very rare to have burst failure of fittings in race cars from the application of braking pressure, whereas the real failure mode is Wayne's direct experience of fitting failure from multiple applications of torque. So this is what his "field testing" experience shows and the primary reason to use steel fittings.

I defer to his experience....thanks Wayne...

All the brake fittings on my cars will be steel.....

[problemchild]

The theory of banning alum brake fittings csme from some professionaly maintained F/Atlantic and Formula 3 cars. As Chief tech inspector for VARA and HSR West, we found that someone does a bolt check on th car looking for loose anythings, they put a wrench or 2 on the fittings and give the nut a slight turn to see if it is tight. and on to the next one.
Next event same again, and again. After a while the fitting fails between the alum threads and the necked down area closer the hex or "T" part.
There is no inspection of this failure other than the feel of a stripping thread when torquing it up. It has absolutely nothing to do with tube, nut design or nut material or internal pressure.
I have personally found this on Fv, FF1600, my Formula 3 and Formula B, and many production cars. The March FF's we built in 1972 all had Steel or SST fittings from the caliper to the master cyl.
Race VARA bring SST or Steel brake fittngs!!!! Any questions?
wtmitchell28@yahoo.com

Threading steel fittings into aluminum brake calipers and aluminum master cylinders are just as likely to get stripped as threading steel brake lines onto an aluminum tee. That logic can be applied to much of the car. Poor preparation/human error seems to be a constant in any mechanical equation. Do you allow aluminum fittings in the oil system? If my oil line or oil pressure gauge line gets checked too often, it may fail and spew oil all over the track. It just seems like a strange restriction on cars that are likely running magnesium and alloy wheels that may be 50 years past their designed life cycle on tube frame chassis, often "birdcage" or even aluminum.

Does anyone have any real logic to support this traditional standard? Braided hand-made lines or chinese crimped braided lines seem so much more of a potential failure point, as do anodized aluminum suspension components, hubs, and wheels.

[Bob Wright]

Very interesting info on alu vs. steel fittings. The point about bolt checks and putting ever more torque on fittings applies to bolts all over the car...if one is not careful, or a crew person is not trained, you can eventually find 1/4" bolts with huge torque on them...

Master cylinder placement and bore- all my cars have had the front cylinder in the middle position. Also- the smaller diameter bore is generally the front (I think because it generates more pressure). I run .70 front and .75 rear on a F2000. My goal for max brake pressure is 1000 psi under threshold braking. I rarely achieve it, normally seeing 800 to 900 psi (like turn 10 at Road Atlanta) under heavy braking.

[Bill Manofsky]

Threading steel fittings into aluminum brake calipers and aluminum master cylinders are just as likely to get stripped as threading steel brake lines onto an aluminum tee. That logic can be applied to much of the car. Poor preparation/human error seems to be a constant in any mechanical equation. Do you allow aluminum fittings in the oil system? If my oil line or oil pressure gauge line gets checked too often, it may fail and spew oil all over the track. It just seems like a strange restriction on cars that are likely running magnesium and alloy wheels that may be 50 years past their designed life cycle on tube frame chassis, often "birdcage" or even aluminum.

Does anyone have any real logic to support this traditional standard? Braided hand-made lines or chinese crimped braided lines seem so much more of a potential failure point.

Yes, if you repetitively tighten any fitting over and over again, it will fail...from experience in the field, the failure mode is stripping of the threads.

Second, failure of chinese steel braided lines is mostly a quality control issue. I have direct experience with their steel being full of inclusions. So the reason why I do not put chinese junk on my cars.

The best fittings and brake lines are made by suppliers who perform quality control by taking select units out of the production runs, say every 100 or so, and test them to failure with the hope of generating repetitive data. If there is an "excursion" in the data, they stop production and perform a full analysis as to the cause. These are the people to buy components from. Aeroquip is the best. Everything is aircraft grade and worth the price.

Galling of steel against aluminum has been a known issue for decades. Also, there is a phenomenon called galvanic corrosion between the two dissimilar metals forming a slight voltage across the interface. Bare aluminum against steel will corrode over time. so the reason for anodizing.

In fact if you put bare metal against graphite, you can measure the voltage. Bare aluminum against graphite is essentially a battery. I used to design composite structural components for stealth aircraft. We had to design in a thin fiberglass shim between aluminum and graphite mating components as a voltage barrier to keep the metal from corroding.

Steel to steel, aluminum to aluminum and you should be fine. Just be careful when torquing aluminum fittings over and over again.

[dogrings]

Steel to steel, SST to SST good, Alum, not in VARA!

[Bill Manofsky]

Steel to steel, SST to SST good, Alum, not in VARA!

Wayne,

To avoid confusion, when I said aluminum fittings to aluminum fittings is ok, I did not mean brake lines. I was referring to oil lines.

Thanks,

Bill

[Steve Demeter]

Grrz I was just talking about what I thought was simply good practice. Yes we have aluminum MC's and calipers but they are designed for the loads imposed on them.

My general thinking is that an aluminum FITTING is not designed to work under the higher pressures in a brake system than say in an oil system.

And who ever used plastic brake lines anywhere but on a Kart?

Certainly not me.

[Bill Manofsky]

Grrz I was just talking about what I thought was simply good practice. Yes we have aluminum MC's and calipers but they are designed for the loads imposed on them.

My general thinking is that an aluminum FITTING is not designed to work under the higher pressures in a brake system than say in an oil system.

And who ever used plastic brake lines anywhere but on a Kart?

Certainly not me.

Steve,

You are correct. I am not saying to eliminate all aluminum in the brake system.

We are only talking about the fittings that have much thinner wall thickness than the master cylinders and the calipers. Thus the fittings are the weak links.

The equation is very simple. Pressure = Force/crossectional area

Since the area is at the bottom, the larger the area means the smaller the pressure load. The cross sectional area of a caliper or a master cylinder is much greater than a brake line or fitting and cane easily handle the load even if it is made from aluminum. It is a simple matter of the material properties.

For that matter, it is possible to make a master cylinder out of a block of plexiglass if it has the proper wall thickness based on it's ultimate tensile strength.

Bill