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The moment a clutch begins to engage...

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The moment a clutch begins to engage...

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Old 03-14-2015, 12:38 PM
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Present day setups allow degrees of clutch slippage so the clutch functions like a torque converter (or continuously variable transmission). Tuning this type of setup is not intuitive and I think there is a narrow range of setup parameters in which it works well.

Perhaps one could re-visit the tiny, purpose-built torque converter (hydraulic or belt), separate from the clutch. The purpose, of which would be to make setup easier at the expense of weight and complexity. The clutch would be for starts and fuel stops. The torque converter could be tuned for optimum performance over a wider range of usefull settings in conjunction with the automatic 2 speed gear box, or even in place of the 2-speed.



Last edited by ic-racer; 03-14-2015 at 01:26 PM.
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Old 03-14-2015, 01:36 PM
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Default A few points, my perspective.

As per the last point I have been thinking along the same lines because there is talk about aggressive clutchs and soft clutches etc. when the art would be smooth changes with out to much slip at the the right power band for a given engine, track, driving style.
All the maths in the world will not replace actual testing.

In my game that is so true, sure do the pre maths but field trials tell you how it really is..

I wonder has anyone every built a test rig, like dyno set up, To test clutch set ups.
You would want an rpm sensor on the actual engine rpm. Then one on clutch bell with a good high speed data logger.
Then a variable simulated load.

All this could be done with a good driver a constant track a box of tires a good engine and few litres of fuel.
A list of all the variables
Springs
Shoes
Spring settings
Weights ranging from light to heavy.
Then a range of gaps.
Create a testing matrix record results analyse data, create set up matrix.

Simple really.

I expect the reality is, that is what the top drivers have done over the years and have by trial and error established what works for them in any given situation.
I do wonder if anyone has applied any real engineering to clutch design beyond let's build this and see how it works?

My perspective


Hi Harry..
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Old 03-14-2015, 05:11 PM
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Originally Posted by shanwright View Post
As per the last point I have been thinking along the same lines because there is talk about aggressive clutchs and soft clutches etc. when the art would be smooth changes with out to much slip at the the right power band for a given engine, track, driving style.
All the maths in the world will not replace actual testing.

In my game that is so true, sure do the pre maths but field trials tell you how it really is..

I wonder has anyone every built a test rig, like dyno set up, To test clutch set ups.
You would want an rpm sensor on the actual engine rpm. Then one on clutch bell with a good high speed data logger.
Then a variable simulated load.

All this could be done with a good driver a constant track a box of tires a good engine and few litres of fuel.
A list of all the variables
Springs
Shoes
Spring settings
Weights ranging from light to heavy.
Then a range of gaps.
Create a testing matrix record results analyse data, create set up matrix.

Simple really.

I expect the reality is, that is what the top drivers have done over the years and have by trial and error established what works for them in any given situation.
I do wonder if anyone has applied any real engineering to clutch design beyond let's build this and see how it works?

My perspective


Hi Harry..
Hey Steve,

The trial and error method is tried and tested, there's no doubting that. Wouldn't you like to know the forces applied by throws compared to the resisting force of the spring, it would confirm if a bigger gap will slip or bite. I don't intend to go into the deep science of it, but without the facts, odds are we'll be playing a game of hit and miss.

I found a spring calculator online, its pretty good I think-> Spring Calculator I plugged in my measurements and it was pretty close to the force being supplied by the throws. I posted them, but accidentally went "back" and poof gone in a throw of anguish... Realised I will need a spreadsheet and 30tooth by chance is doing up a great spreadsheet in off road too, so might throw over the data to him.
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Old 03-14-2015, 05:40 PM
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Originally Posted by shanwright View Post
I do wonder if anyone has applied any real engineering to clutch design beyond let's build this and see how it works?
What i always understood was the idea that simulating on the computer is used to skip 90% of the testing on the track. On the track the testing is to expensive and time consuming. I know they do a lot of math and simuating in the F1, just to save time and money. The base of this kind of simulating is math and the mechanical/dynamic principles. Just like Blis says, it gives a real insight in what`s happening.

@Blis, sorry my friend, at the moment i dont have time to make you a nice spreadsheet.
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Old 03-14-2015, 06:21 PM
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Originally Posted by rbakker View Post
What i always understood was the idea that simulating on the computer is used to skip 90% of the testing on the track. On the track the testing is to expensive and time consuming. I know they do a lot of math and simuating in the F1, just to save time and money. The base of this kind of simulating is math and the mechanical/dynamic principles. Just like Blis says, it gives a real insight in what`s happening.

@Blis, sorry my friend, at the moment i dont have time to make you a nice spreadsheet.
It's all good Rbakker, we keep it enjoyable and see where it leads us. A lot seems clearer now and its something to do when I need a break, it's a hobby after all!
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Old 04-01-2018, 04:11 PM
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I need help on my Serpent 977 centax clutch. It was working fine, but in my last two outings, the clutch disengaged at the end of the straightway, and the engine revved freely? I checked the clutch and everything looks normal. What would cause the clutch to disengage under full throttle? Any help would be appreciated.
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Old 04-01-2018, 07:54 PM
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Originally Posted by JohnNgSF View Post
I need help on my Serpent 977 centax clutch. It was working fine, but in my last two outings, the clutch disengaged at the end of the straightway, and the engine revved freely? I checked the clutch and everything looks normal. What would cause the clutch to disengage under full throttle? Any help would be appreciated.
Make Sure the clutch but is not loose
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Old 04-01-2018, 10:33 PM
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This is a VERY OLD thread....

This is often caused by too soft spring and the inertia of the engaged clutch on deceleration unwinds the clutch spring nut. You can try using loctite, but I suggest you use a heavier spring. This will disengage the clutch and help apply pressure to the clutch spring tensioning nut to prevent it coming loose. It's a common problem in 1/8th scale cars, not just Serpent.
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Old 04-02-2018, 02:33 AM
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Most of the time when that happens the thrustbearing is gone, the ring with the balls is probably missing the balls....
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Old 04-02-2018, 04:40 AM
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Originally Posted by Roelof View Post
Most of the time when that happens the thrustbearing is gone, the ring with the balls is probably missing the balls....
It happened to us and happened to my friend with the MRX5 when using a clutch spring that's too soft. Thrustbearing was fine, the clutch nut would come loose and you could hear the engine load up with fuel, and you think it's become rich. When you take clutch apart you realise the clutch nut has unwound. Same happens if we try using the XRAY conical washer system, without load on the spring, the nut unwinds. Im not a fan of loctite on the clutch, otherwise the XRAY washer system is awesome. Very snappy and consistent as long as you can keep the nut fixed
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Old 04-02-2018, 05:48 AM
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What a nice thread indeed. Although some of us may argue the theory is not important as the skill is developed due to experience and a lot of testing. Both of them at level 0 for me at this stage. However: an understanding of the theory can and is important to point you in the right direction or analyse whats going on. Looking forward to play with the clutch....
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Old 04-02-2018, 02:15 PM
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Originally Posted by JohnNgSF View Post
I need help on my Serpent 977 centax clutch. It was working fine, but in my last two outings, the clutch disengaged at the end of the straightway, and the engine revved freely? I checked the clutch and everything looks normal. What would cause the clutch to disengage under full throttle? Any help would be appreciated.
This is very likely not the clutch but the one way bearing. Replace that or clean with brake cleaner and put a drop of one way lube in the bearing.
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Old 04-03-2018, 02:16 AM
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Originally Posted by Julius View Post
This is very likely not the clutch but the one way bearing. Replace that or clean with brake cleaner and put a drop of one way lube in the bearing.
Sorry guys... Not sure what I was thinking or read to be honest..

Oneway issues cause a lot of problems and pull the revs down when shifting to 2nd gear causing an on and off condition... And as Roelof said, it the thrustbearing is shot, then the gap is too large.. So I'm not sure what it is...

Again, sorry for misreading.

Originally Posted by JohnNgSF View Post
I need help on my Serpent 977 centax clutch. It was working fine, but in my last two outings, the clutch disengaged at the end of the straightway, and the engine revved freely? I checked the clutch and everything looks normal. What would cause the clutch to disengage under full throttle? Any help would be appreciated.
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Old 04-03-2018, 05:43 AM
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If it is the 1st gear oneway then when the engine drops back to idle you hear a click and you can drive on.

My advice is when the oneway needs to be replaced you have to replace the shaft also
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Old 04-03-2018, 01:55 PM
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Thanks for the responses. Upon examination, I saw that my clutch nut was a bit loose. I'll put a drop of threadlock and go to a harder spring. The rest of the clutch was normal, so I'll clean it up and lube the bearings again.
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