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Old 11-04-2009, 02:51 PM   #901
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Default Sounds good to me Prime:))

Quote:
Originally Posted by PrimeAKF11 View Post
Think of it this way:

Clutch gap is the distance the clutch shoe travels before engaging.
Endplay is the distance the clutch bell travels before engaging.

Let's forget about endplay and talk clutch gap for now. When you set the clutch gap, you take the inner bearing and the shims off and measure the up and down play the bell has. Since the shoe will be travelling outside as the engine revs, you are effectively measuring the distance the shoe will be moving before engagement.

Let's say you just set the value to 0.7mm. So, now you got both the clutch gap and the endplay at 0.7mm (Endplay is currently at 0.7mm since the bell has to move that amount).

Why not run the car like this? Well, if the bell has to travel 0.7mm outside for engagement, it will be slamming itself against the thrust bearing every time the clutch engages. As you know this isn't exactly healthy for the bearing. Ok, then why not set the value to something like 0.1mm in the first place? Sure, had we set the gap to something like 0.1mm, the bell only has to travel 0.1mm and won't prematurely wear out the bearing. But now you have a car that bogs severely since now the shoe also can't travel more than 0.1mm. Since the shoe can't gain enough angular momentum to transfer to the bell during the time it travels 0.1mm, the car bogs.

So what we want to do here is keep the clutch gap at 0.4-0.8mm so the car doesn't bog, while keeping the endplay value at <0.1mm so the bearing doesn't wear out.

Now you take the bell off and add the inner bearing & shims under the bell. Since you are moving only the bell outside, the clutch gap stays the same, while the distance the bell has to travel decreases. Ideally that distance should be <0.1mm.

Now you have a car that neither bogs nor eats bearings . If the car doesn't launch the way you want it to, try experimenting with the clutch gap but leave the endplay at <0.1mm. And yes every time you adjust the clutch gap, you have to re-adjust the endplay as well.

Did that make any sense at all? I don't even know what I just wrote..
I will put a little more energy into the measurement.. to date Ive had little problem but might not have the best performance.. looking forward to using your parameters.

cheers

h

PS: I use Red Spring + Red Shoes on UFO2 and been doing very well with thrust bearings, I do lube them with Inox grease regularly and give them a once over. I also use a thrust bearing inverted on the clutch nut rather than shims. Ive felt that shims seem to get hot with friction and warp hence changing the gap. A friend sources washers of the exact thickness to his needs and swears by this.
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Old 11-05-2009, 01:01 AM   #902
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Default Clutch 101 - by team serpent

Clutch overview.

The force exerted by the weights increases with their distance from the centerline of the crank and with rpm.

Sliding weights behave heavier than when they are pivoting.

Leading weights are slightly more aggressive than trailing weights.

Leading is when the pin is in the right hand side of the weight when looking at it in the flywheel and trailing is when the pin is in the left hand side of the weight.

The spring resists the outward movement of the weights in a linear manner e.g. KG per mm.

The total resisting force is determined by the strength of the spring, the preload you have applied by tightening the nut and the gap.

Too strong a spring for the weights makes the clutch very sensitive to adjustment and wear.

Too large a gap and a weak spring can result in the coils stacking together to form a solid spacer and prevent the shoe from pressing hard enough (or at all) on the bell. This will burn the shoe out very quickly.

The distance that the weights can travel from the centerline is determined by the clutch gap.
The amount the spring must compress is determined by the clutch gap.
Too small a gap can result in insufficient force applied to the shoe and constant slippage- sometimes very slight.
When running small gaps 0.5 and less the clutch may slip and the tendency is to decrease the preload when in fact it should be increased. The problem is caused by insufficient rpm to generate the force required at the diameter of the weights at engagement.

A larger gap has the effect of increasing the distance the shoe has to travel and hence the effective preload.

The force exerted by the weights increases exponentially with radial distance and rpm.

That is why a large gap results in an aggressive clutch. The weights slide out gradually at first but accelerate as they get further away. They effectively get heavier faster than the springs resistance increases.
Enough gap and they can hit the shoe into the bell like a hammer. Usually causing traction loss, extreme drive-train loads or squirting you into the nearest barrier.
Nearly impossible to modulate the throttle like this.
If engaging too early but aggressively it just pulls the rpm down and the motor seems to bog.
If engaging smoothly but too early (or outside of the power-band) then the car seems to be contemplating whether or not to accelerate for the first few meters then eventually does and the clutch may slip. Motor tends to run hot and be difficult to tune. You also seem to need shorter gearing than everyone else.

A suitable gap (for the mass of the weights and the rate of the spring) will let them make contact smoothly and gradually slip less, resulting in a smoother clutch action.
This is the action you want your combination of weights, spring and gap to operate with.
It is possible to get a really good clutch with a smooth action and to suit the conditions by juggling the variables.

This can seem complicated but it just needs some thought as to exactly what you are trying to improve and what variable/s will give you that effect and how the change may affect the other variables.

If any variable needs extreme changes then one of the others are usually out of range. For example, if you need to tighten the spring excessively then you may need a stronger spring or lighter weights and a bigger gap.

Clutch shoe wear increases the gap and has the effect of increasing the preload.
That is why your clutch may change a lot when you rebuild it with your original settings after a lot of use.

It is best explained with an example.
Similar clutch action can be achieved with different setups.

Example 1.

Heavy shoes
Strong spring or more preload
Small gap

Will be similar to-

Light shoes (exert less force for the same distance as those above)
Weaker spring or less preload (Lighter shoes need less resistance)
Bigger gap. (To achieve equal force as those above and avoid slippage when fully engaged)

Then you can try a grippier or slippier clutch shoe in combination with all the above. They do what the name implies.

Free-play on the bell is almost always as little as possible- NEVER PRELOAD.


Tips

Keep notes.

Reset the gap and preload to compensate for wear or replace the shoe/spring often and just reset to your original settings.

If you find your clutch suddenly starts to feel good after much running (wear). Record the settings and use the same ones when you rebuild it.

If tightening the flywheel nut with the Serpent holder, ensure that it is on the right way round, does not slip and do not tighten the nut excessively- it can bend the pins and really have you chasing your tail with uneven engagement etc. I prefer to hold the flywheel with a bottle opener type strap.
The Serpent tool is a must have for setting the gap consistently however.

Make sure the clutch spring nut has not got any burrs or it can adjust itself.

Use a good quality high temp thrust grease (800 degrees C grease is available in limited quantities) and clean and grease the thrust bearing often. (After each run is not too often) A match head sized blob of grease is enough.

Replace or wash and re-oil clutch-bell bearings regularly with high quality synthetic oil such as Mobil-1. Good for new bearings too. (Or use above grease)

Keep everything including the flywheel as clean as possible. (Brake cleaner works well)

Face the thrust bearing hollow side inwards -it seems to keep the grease in longer.

Polish the clutch shoe support plate on the face that contacts the weights and give it a hint of grease.
Polish the holes in the support plate and give the pins a hint of grease.

Measure the spring often as it tends to get shorter over time. Releasing the preload between track days makes it last longer.

A good clutch setup may slip a bit for the first few corners until it warms up.
Do not run-in or tootle around with a race clutch setup- it will always be slipping, causing it to overheat and destroy itself.
This is the same reason inexperienced drivers need a softer clutch.

If the clutch suddenly changes drastically something has gone wrong- do not try and just adjust it. Strip and check everything.

Suddenly starting to cut out off-throttle or not idling is often a tell-tale of clutch trouble.

Just start with a baseline setup and adjust from there. Ask someone you trust for a baseline or use the ones below.
Do not be afraid to experiment with combinations.

There is no ‘one size fits all’ solution but the design of the Centax ensures that you can tailor your clutch to your motors characteristics, your driving style etc.



Effects- assuming all other variables remain unchanged and are within reason.

Weights

Heavier- Earlier engagement More bite Suited to smaller gaps
Lighter - later engagement Less bite Suited to larger gaps
Sliding- As for heavier
Leading - More aggressive bite-point
Trailing - Smoother bite-point

Gap

Bigger- Later engagement More aggressive More bite
Smaller- Earlier engagement Smoother Less bite

Spring

Stiffer- Higher rpm adjustment range and suited to heavier weights
Softer- Lower rpm adjustment range and suited to lighter weights
Less coils- More adjustment before coil-bind and suited to larger gaps

Preload

More- Higher rpm engagement Less overall bite
Less- Lower rpm engagement More overall bite

Shoe material

Softer- Stops slipping a lower rpm/force More bite
Harder- Stops slipping at a higher rpm/force Less bite
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Old 11-05-2009, 02:30 PM   #903
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Default g4rs 09 option parts

Hi Guys,
I recently bought the g4rs 09 and want to know how do you get the motor to lean forward?Also how do you adjust the height of the front lower suspension arms?
thank you
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Old 11-05-2009, 03:05 PM   #904
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Default Slanted Engine Mount

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Originally Posted by grouchy View Post
Hi Guys,
I recently bought the g4rs 09 and want to know how do you get the motor to lean forward?Also how do you adjust the height of the front lower suspension arms?
thank you
Im certain it's a KFactory option part
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Old 11-05-2009, 03:17 PM   #905
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Default

Hi Grouchy

the engine leaning foward was prototype only..

The raise the height of the front lower arm you will need the kfactory option thats soon to be released.
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Old 11-05-2009, 04:27 PM   #906
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Default 17t

Hey,Bobby here anyone tryout the 17t pinion on their 09s yet, if so would like some feedback thanks.
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Old 11-05-2009, 05:04 PM   #907
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Default

hey Bobby
i havent tryed a taller gear ratio but i have gone shorter, 2 tooth up on each spur when we had lots of grip at the nationals.

i race at moorebank raceway home to the 2001 1:8 worlds so its a large eurporean style track with a long straight and medium infield. stock gea ring works fine
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Old 11-05-2009, 08:22 PM   #908
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Default Wow !!!

Quote:
Originally Posted by mrgsr View Post
hey Bobby
i havent tryed a taller gear ratio but i have gone shorter, 2 tooth up on each spur when we had lots of grip at the nationals.

i race at moorebank raceway home to the 2001 1:8 worlds so its a large eurporean style track with a long straight and medium infield. stock gea ring works fine
Well i want to try 16/63 22/57 my motor is Murnan RbM3, our straight is 212 feet with medium infield.Feedback welcomed
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Old 11-05-2009, 10:16 PM   #909
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Default Unsure of internal gearing..

Quote:
Originally Posted by impalabob64 View Post
Well i want to try 16/63 22/57 my motor is Murnan RbM3, our straight is 212 feet with medium infield.Feedback welcomed
this might be helpful though..

http://www.beachmumsracing.org.au/rc-rules/speed-calc/
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Old 11-06-2009, 03:29 PM   #910
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Default Race #3

Well car is packed ready for race #3 .Heard our Kraceway has a new layout,so it will be very interesting thanks Blis,yes it helped.Hey if anybody wants to checkout this race they will have live feed for Sat and Sunday.(www.forgass.com) is where you will find it.Wish me luck.
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Old 11-06-2009, 03:36 PM   #911
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Default Nice.. nice...

Quote:
Originally Posted by impalabob64 View Post
Well car is packed ready for race #3 .Heard our Kraceway has a new layout,so it will be very interesting thanks Blis,yes it helped.Hey if anybody wants to checkout this race they will have live feed for Sat and Sunday.(www.forgass.com) is where you will find it.Wish me luck.
Nice site, loaded fast in Aus.. will be here barracking for ya BOB.

Heads Down, Magics Up, RACE FACE : ON!

good luck mate!

h

PS: I used the speed calc to simply measure the theoretical difference in speed leading into long straights when changing gear ratios. There are too many factors to get a REALISTIC speed measurement.

PPS: HP == Metric HP == 75Kg per metre per second!
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Old 11-06-2009, 03:56 PM   #912
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Default Thank you

Quote:
Originally Posted by blis View Post
Nice site, loaded fast in Aus.. will be here barracking for ya BOB.

Heads Down, Magics Up, RACE FACE : ON!

good luck mate!

h

PS: I used the speed calc to simply measure the theoretical difference in speed leading into long straights when changing gear ratios. There are too many factors to get a REALISTIC speed measurement.

PPS: HP == Metric HP == 75Kg per metre per second!
Race face is on
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Old 11-08-2009, 04:49 AM   #913
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Default

Hey guys
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Old 11-10-2009, 11:39 PM   #914
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Default servo selections

well i am in the middle of my build of a g4rs 2009 and i need some input for servo for the steering and throttle
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Old 11-11-2009, 04:26 AM   #915
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Default

Does anyone know when the optional front lower suspension parts to raise the lower hinge pins be available?or is this another prototype like the forward engine mounts that were supposed to be available?
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