CP's Trackday 1.6 on TB's re-build

Cheers those comments - good thinking.
One of the other serious issues that has emerged from the brake change has been the heat generation. We've measured the temperature of the brake and general hub area as being well into the mid 600 degrees C :eek: . The readings may not be that accurate (although we have tested on other things and it seems ball park)but nevertheless whatever, it's still hot enough to allow the wheel bolts to stretch loose. After 2 or 3 fast laps we need to get in to tighten them and then if you dont loosen them before they get cold they wont come undone again.
I should imagine that these temperatures are having fairly significant effects on the bearings etc etc seeing as its all std stuff and not designed to be cooked up at this heat.
Looking through brake fluid specs there is only one fluid that seems like it can live with this temperature - the DOT 5.1 Castrol DTF (? IIRC) so we will have to change to that which could well help cut brake fluid boiling and thus overall brake feel.
The big change that I need to make on this whole subject is to sort out some kind of forced ventilation to the brakes but it wont be easy - there's not much room around front wheel drive hub assembilies:confused:

Progress has slowed a bit whilst trying to sort what I want to do and also waiting for parts.
However I have now got the gearbox selector turret
http://i205.photobucket.com/albums/b...ostdone024.jpg
http://i205.photobucket.com/albums/b...ostdone025.jpg

God knows how much horspower the dog box is going to soak up. The drag on it is massive:( I guess it the price you have to pay to not have a box that breaks in exteme conditions

Your fluid temps should be nowhere near the 600deg C you're measuring (I'm assuming with a laser pyrometer) I'd be concerned if the fluid temps were much over 200 tbh. Heat transfer to the fluid can be reduced by using inserts between pad and piston, but again you shouldn't be running those temps to begin with IMHO, and ventilation is definately the way to go! You could try some ram pipes from the front bumper with ducting secured along the tie-bars and under the TCA's to point at the inner face of the disc.

i thought dog boxes sapped less power than normal boxes due to the more direct meshing of the gears??

is that the correct term?

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Originally Posted by dhdev (Oli)

Your fluid temps should be nowhere near the 600deg C you're measuring (I'm assuming with a laser pyrometer) I'd be concerned if the fluid temps were much over 200 tbh.

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Yeh you're right - looking at the fluid performance specs for the various fluids that you can buy the temperatures are less than half the figures we are getting off the pyrometer ( as you say). We guessed from this info that the fluid temps are a lot lower than the actual hub and brake temps.

Quote:

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Originally Posted by burgo

i thought dog boxes sapped less power than normal boxes due to the more direct meshing of the gears??

is that the correct term?

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Umm I don't really know. Obv at the mo its not properly lube'd up but I would imagine that the larger mass of the gears and the increased surface area of the meshing parts(they are wider and heavier duty) would absorb more power, and maybe more so than the advantage of straight cut over helical:confused:

the main advantage of straight cut is the reduced side loading on the box main shafts, i would imagine when the gears have run for a bit they will loosen up somewhat, the rolling losses on mine are tiny, it takes ages to run down on the dyno!
loving th turret cp, think i may have to go for a dog box after my german escapades, the synchro sccr is looking decidedly worse for wear!

I promise I'll shut up on about my gearbox after this postlol
I went to fit the selector turret assembly tonight and found it wouldn't fit unless I ground away some of the casing like so
http://i205.photobucket.com/albums/b...ostdone027.jpg

Next job is to get it all back into the car

Talk to me about the tie bar solution you've made please CP.

I cannot understand how this is not wearing metal on metal and could only serve a hand full of hard miles before dangerous play results. Surely it's a heavier design compared with Lee303's elegant solution?

The loading on a rose joint is acceptable front on as much as side on due to the bearing being perfectly round; makes no odds. What does matter is how the bearing itself is held into the bracket that's mounted solidly to the chassis.

Does the front not skip about with your arrangement?

I like the theory; the way you've identified the need to perfect the lower arm / tie bar situation, but find the execution alarming.

Using a socket set UJ for the gear linkage will grant you deflection just where you don't want it. the reason proper UJ's cost what they do is because they will eliminate that slop and last. Can you get all 5 forward gears and reverse with setup you made?

I was a little surprised to see a built up engine sitting on it's exhaust manifold too.

Sorry for all the challenging comments

I'll speak on CP's behalf as you'll get no joy for the next month. I drive the car also and have had some input in the build.

I too had/have reservations on the wishbone arrangement but I do respect CP's years of experience in the field of wear on metal components. The first point in making a proper wishbone was to get a true arc with both front and rear mounting points in perfect alignment. The standard mounting points and any solution based on them will not give this. The wishbone is fairly heavy, but is also very strong and we both accept that there will be some wear on the bolt and hole that it passes through, but you must take into account three things. Firstly and most importantly, this car does a maximum of two or three track days a year with NO road use. (limited miles on a smooth surface). Secondly they are Catapillar bolts wich are something special in the bolt world and thirdly the wearing surface are large due to the thickness of steel and the diameter of the bolt. It will wear, but not at a rate that will go unnoticed and not be repaired. CP's concern with using a rosejoint at the front was having two of them hold the wishbone perpendicular to the direction of travel. It may work, but is does run a risk of being damaged.

The gear linkage was a personal challenge for CP. This isn't born out of a desire to save money, more to see if he can improve the design of the quaife item. He had seen people using the quaife selector that could get all five gear whilst parked, but struggled and missed gear when driving in anger. I have used the linkage and it works. It is very tight and precise and yes all gears are obtained easily. The Socket set UJ works very well, the main benefit being that it is not at such an accute angle as the quaife design. The only negative point is that the throw is greater than it should be.

Yes the engine sat on the manifold wasn't ideal, was bought standing like that and sat like that till it went in with no apparent ill effects luckily.

The good thing about our fabricating abilities and the facilities we have is that its easy to try something and change it if it doesn't work. It's all fun!

MC