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Go Back   Madabout Kitcars Forum > Mad Build Area > Marlin 5exi builds

Marlin 5exi builds Calling all you sexi builders....sorry 5exi builders, show us your progress.

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  #21  
Old 18th May 2007, 20:29
holgate86 holgate86 is offline
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Hi Craig,
haven't been checking forum for a while, mega busy at work. Sorry to hear your problems with clutch. Is it possible your bulkhead structure is flexing too much and thus losing travel at the slave cylinder. I presume the clutch doesn't clear when fully depressed, does the pedal feel really sloppy which would be hydraulic problem or does it feel normal and just can't get gears.
If the latter the clutch plate may have stuck to the flywheel due to not being used for a long time. Ring me if you want to discuss.
good luck with it anyway.
Brian
ps apart from clutch hows it going
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  #22  
Old 18th May 2007, 21:13
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Hi Brian, thought I would have seen you at stoneleigh with your updated car?
I will have to come down and have a look soon.

Bulkhead does not flex as it's reinforced with 3mm stainless top to bottom.
pedal has feel and master piston travels 100% with pedal pressed which in turn moves the clutch fork about 1cm maybe a bit more but after speaking to John and Jerry my pedal is not stiff enough

Although I have spent about 35-40 hrs on it now and put through about 5 litres of fluid I still think it's hydraulic and not the clutch

Just not sure how to combat it now may take you up on the call.

Other than that the car is ready to drive
Craig
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  #23  
Old 19th May 2007, 00:35
grant620 grant620 is offline
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Hi
What size hose are you using to go front-rear?
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  #24  
Old 19th May 2007, 05:56
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Hi Craig.

The bubble direction says to me the master is doing it's job.

Grant has a good point. I'm using copper pipe complete from end to end. Pirtek suppplied the pipe and put the ends of the master and slave on for me.

I found that brake pipe is larger than the clutch pipe in diameter.
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  #25  
Old 19th May 2007, 16:48
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I have questioned this in my own head as the clutch hose is goodridge front to back about 8mm internal which was made up by pirtek but after speaking to John (alackofspeed) last night the internal dia does not make any differance (lost me abit then but something about equazi pressure) so that is something else struck of my list of things it could be!!

Infact just realised that I no longer have a list........
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  #26  
Old 19th May 2007, 17:56
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Hi Craig.

When Ian (Merlinman) did his hydrualic clutch (building a 5EXI with old DOHC honda lump), changing the copper pipe diameter made all the difference.
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  #27  
Old 19th May 2007, 21:17
holgate86 holgate86 is offline
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Hi Craig,
I think Limpabit might have hit the nail on the head. If you are using large bore pipe the pressure will be the same but the distance travelled by the slave cylinder will be less, not sure about this as I'm no hydraulic engineer but you might have to try it as you have nothing else left on your list mate.
I couldn't make Stoneleigh due to heavy work schedule, the cars doing well though, gearchange is superb to what it was. I have loads of jobs to do still when I get some spare time. I use the car every day for work and so far have had few problems but it is only 4 miles away, I haven't done any long runs in it for a while.
Hope you get sorted with your clutch soon, if you want to try solid brake pipe I can make one up for you, I am using solid brake cunifer pipe on my clutch by the way.
Brian
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  #28  
Old 19th May 2007, 23:28
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alackofspeed alackofspeed is offline
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The hydraulic pipe diameter should make no difference, if it is assumed that the fluid is incompressible, and the pipe's volume is unaffected by internal pressure.

Looking at it very modularly, the fluid leaves the master cylinder, is displaced into the tube, which in turn displaces the slave cylinder's piston.

The only way I can see the larger bore pipe making a difference, is if the pipe, because of its greater diameter, expands sufficiently under pressure, that it "consumes" some of the fluid displaced by the master cylinder, thus reducing the movement of slave piston.

Craig, my point about the system, is that it is qausi static, and that flow speed can be ignored. It's not like fuel hose, for example, were there is a pressure drop resulting from the flow, hence it being advisable to measure, and regulate fuel line pressure as close to the point of use as possible.
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  #29  
Old 20th May 2007, 19:05
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Gent's if you are talking about pressure in lines or pipes etc, then pipe internal diameter has a massive effect. It is down to internal friction of the material on the internal walls of the pipe or tube. Bigger diameter less friction for the increase of fluid moved.
I work in an industry where amongst other things our equipment is used to supply paint around the car factories. Too small a pipe diameter and the pressure drops are horrendous. Resulting in too little paint pressure at the robot sprayer electrostatic atomisers.

If you want to compute the pressure diiference in pipes then take a look at the following:
http://www.flowmaster.com/solutionov...FQNQEgodHw--6g

Or failing that do a google on Pressure Drop Calculations.

Now one thing that does not change (if you alter the diameter of pipe work) is the amount of travel. So the travel will be the same it's just that you will be exerting less pressure if the pipework is too small.

Cheers Mike
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  #30  
Old 20th May 2007, 19:37
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Mike, your comment about pressure was what I was getting at in my post above. I was taking the flow out of the equation, stating that a clutch hydraulic system is quasi static, and thus the flow speed can be ignored - the only issue is static pressure of the fluid, and thus pressure drop associated with pipe bore, and fluid velocity and viscosity does not need to be considered.

Anyhow, the jist of the matter as far as Craig is concerned, is that my clutch works using a narrower bore similarly constructed flexible tube, and the same specification master and slave cylinders. We can therefore rule out the diameter of Craig's clutch hose being the cause of his difficulties.

Next suggestion what might be wrong..........? (I'm clean out of ideas, having discussed this to death on msn with Craig.)
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  #31  
Old 20th May 2007, 19:43
Ric H Ric H is offline
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The line pressure drop due to flow is only an issue during pedal movement - I agree with John that if you just consider the static cases at each end of the pedal motion then you can ignore the bore size. The only potential issue I can see from small bore would be that the clutch movement may be too "damped" - i.e when you release the clutch pedal it might return more slowly than you want due to losses in the pipe. I've gone with 6mm copper which is as per honda use on the type R I think? (except the small bore section over the transmission). I'm not talking from experience yet though because I haven't filled my clutch system yet!

On the subject of which - what's the total travel required at the master or slave cylinder to disengage? John - I saw you said you'd got 95% of the master cylinder travel available: does it need all that? I fear my setup currently has less.

Richard
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  #32  
Old 20th May 2007, 19:55
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Rich, I can't recall what bore my goodridge tubing is, but I think it's 3/16 - my friend is in the bespoke tubing business, and what I have is standard issue brake / clutch hose. Whatever size the hose might be, one thing is for sure, there are no problems with the bore damping the flow. When you bleed the system you'll see how small a quantity of fluid is displaced with each pedal stroke, hence the inconsequential effect of any dynamic losses in the system.

When I said 95% that wasn't totally accurate, and is just my best guess from what I recall when I built my rather odd clutch system. I know that 100% pedal stroke is very close to being 100% of the master cylinder's stroke.

I would say my clutch starts to bite around 35-40% of the stroke above the fully depressed position, and is fully engaged around 65% of the travel. I've not measured it though, and the figures are just my best interpretation of what I feel through my foot!

What is the case with my setup, is that with the lever ratios compromised to suit the pedal length needed in the Marlin, the clutch is quite sharp when compared to typical modern cars.

Rich, have you gone for straight copper, of cunifer? I don't know what the SVA requirements are, but I was lead to believe a few years back, that cunifer should be used instead of copper as it's less likely to degrade in the presence of brake fluid.
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  #33  
Old 26th May 2007, 08:19
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I remeber now. Your right. Make the pipe larger helped with the foot effort not the actual movement.

Did you try moving the clutch lever on the box to see if you can engage the clutch by hand?

I had it as said above. Due to the clutch not being used, it got stuck. I manged to free it up by raising the rear wheels off the ground. Run the engine in a high gear and hit the brakes.

The only other way is remove the box.

Might be worth asking one of the other guys to measure the clutch arm movement on the box when the pedal is pressed. That way you can see if you have this amount of movement by hand.
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  #34  
Old 31st May 2007, 12:13
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Hi John, yeah the fork seems to move freely but very difficult to push fully with engine in car
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  #35  
Old 31st May 2007, 13:02
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Hi
We switched the pipe on John (Marlinturbo)'s 5EXi from 0.19 to 0.13" ID and it got us the travel and pedal feel required.
I don't know (or care much) about all the theory... But it worked!
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  #36  
Old 31st May 2007, 22:40
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Grant, chhers for that!

I will defo try this then as it sort of goes against everything that has been said but the clutch line is the only part I have not tried changing and I know there is no air in my line for defo......

Spent about 70hrs on the bitch now!!

Craig

I will let everyone know the outcome
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  #37  
Old 7th June 2007, 22:13
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I agree it's odd... But there was deffo no air in John's line.
In desperation we changed the pipe and hey presto... Clutch!
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  #38  
Old 17th June 2007, 23:33
Ric H Ric H is offline
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Any joy yet Craig?

Not intending to gloat if not, but I thought I'd explain my clutch experience following today's efforts, just in case it helps.

My setup:

- Civic R master cylinder linked to Rover clutch pedal. Before trying to fill with fluid I modified the cyclinder mounting with a spacer to shift it 5mm forwards -this followed various bits of advice (thanks chaps) suggesting I should make sure I had the whole master cylinder travel available. Now gives full cylinder travel for full pedal travel. Master directly connected to 6mm copper hard line through tunnel to a bulkhead fitting at the firewall. 5mm braided flexi from there to slave cylinder.

Got to be honest - bleeding was a piece of cake. I filled the reservoir and pumped the master a few times with no real effect. Then I opened the slave bleed a couple of turns and stuck a long length of clear hose onto the nipple. This was long enough for me to stick the end in my mouth while still topping up the reservoir. I sucked (hard!) until fluid without bubbles was coming up the tube (then stopped before getting a mouth full!). I then tightened the bleed nipple again and hey presto, clutch works, fully disengages (heavy but I I haven't any more pedal travel to play with so tough). Took about 5 minutes. I really can't think what the problem is at your end. Must be hugely frustrating
Richard

PS - yes, I used straight copper, not cunifer. As far as I'm aware there's no issue with corrosion from brake fluid. After all, pure copper brake line is readily available. Hope this isn't an SVA issue... I guess for SVA purposes it's cunifer anyway just to be on the safe side
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  #39  
Old 18th June 2007, 18:58
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Hi all, Update on my piece of shit clutch!!

After changing all my components and spending 's my clutch still did not work and I was basically wanting to smash my car into little bits.....

I have spent over 70hrs on it in total maybe slightly more.

I decided a couple of weeks ago to take everything off and down to a local garage who pressure bled the system for me.....garaunteed no air my hopes were high!

Connected everything back up and hey presto.....it was no better still not working.....ffs

After it playing on my mind for a while and a few people posted on here about the id of the clutch line I visited pirtek and asked there advice.
They told me the inner dia should not make a differance but sometimes it can but they could not make me up a line smaller then the goodridge I already had.

Anyway visited Brians garage on fri (holgate 86) who very very kindly made me up a line thanks much........

Just had the time to fit it tonight due to work commitments and if being honest not expecting much.

connected it up did the usual with bleeding it took the normal 5 mins and clutch works like a dream...........I can select all gears and little drive followed works perfect.

So after all the wasted time it was definately the innternal dia of clutch line, just wish I had followed my instincts and tried it earlier but you live and learn.

My car would bhave been more or less done now but at least I can get motivated again.

Many thanks to everyone for posting and offering advice it is much appreciated

Craig
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  #40  
Old 18th June 2007, 22:10
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Great news! I'll be b*ggered if I know why it has made a difference.... the *only* logical explanation can be the length of pipe, and the wall elasticity.
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