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Giacomo
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667 Posts
Discussion Starter · #1 ·
Last week I had a competition at my place with a friend and as usual we eventually compete with the NSR Moslers.
Usually I can beat his timing but when we raced with the Moslers he beated me and destroyed my previous record.
When he offer me to test his Moslers I took down the record half second!
We both thought we were just in our best mood.
The day after I tested it again and went down even more but I felt the motor was spinning at full revs as soon as I exit the curves without any spinning of the wheels.
Yes, the gear was loose! So I tighten it and tested the car. No way I could get near the new record! So the answer was plain, with the right friction in the gear the car could exit the curves with earlier full throttle and benefitting full torque as soon the grip between the shaft and gear was restored and that happens without wheel spinning.
I tested 1000 laps with different cars and when setting the right torque to the hex screws it works a wonder and it last for a long time!
The setting works perfectly with the Moslers with Ultragrip tyres. The cars are literally glued to the track.
I have a PWM controller but I cannot get anywhere near the benefit of this mechanical friction.

Is the above something anyone has already tested?
Is it allowed to run like this in the clubs?

Settings
Three lane track 60ft
Voltage 11V
Truspeed PWM controller
NSR Mosler AW with medium suspension springs
King 21 Evo
Ultragrip tyres
Air wheels NSR

Lap timing
Old record: 5,447s
New record: 4,986s

In conclusion, this is off course an empirical and rough system but you get fantastic results. Has anyone produced a real friction system with decent results?

Cheers,
JamieG
 

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Premium Member
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2,116 Posts
This is quite astonishing! I can see the likes of NSR and Slot.it Rushing to their drawing boards to design an adjustable friction system for gears. Maybe the guys that beat me already know this trick and keep it a secret from me. It's perfectly legal of course...at the moment. Can't wait to test it out at my club next week.
 

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Nobby Berkshire
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2,015 Posts
Maybe I'm reading this wrong.

Are you saying that with a loose axle gear - in other words the gear does not turn the rear axle efficiently - then your friend's car goes faster?

Is this what you are saying?
 

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Registered
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985 Posts
Presuably this is a similar effect to the slot.it controllers traction control. Your mechanical "fix" limits the torque to the wheels to at or below the point at which the wheels spin , the pinion spins instead. This is in effect ABS for 1:1 cars in reverse. In ABS this that is done actively by sensors, by reducing the torque to the max before wheel spins. The slot.it controller does a similar thing by limiting the rate at which power is increased to the wheels, again keeping the torque within wheel tolerance. So the fundamental logic for youe achievement is sound. What is supprosing is that it is repeatable race to race. The setting may vary on temperature amd track grip but is a very interesting way of achieving the effects.

In theory it can be done by the driver by not squeesing the trigger so fast but that easier said than done ;-).
 

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Administrator
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10,110 Posts
I don't know about the rest of you guys but when a gear starts to slip on our track at Larkfield then you probably only have a lap left at most before the car sits there with the gear spinning and no drive.
 

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Giacomo
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667 Posts
As explained I have a PWM controller from TruSpeed which is similar to the slot.it one in terms of controls.
I do not consider myself an expert with my PWM but the effect you can reach is not comparable.
With a PWM you limit/smooth the acceleration while with a mechanical friction system you increase the revs of the motor much faster and when the gear get the grip, the motor is in the point of the curve of max torque.
The result is to have a bullet car exiting the curves with the motor screaming.

One thing you have to make sure is to have the drive train locked sideways if You do not want teeth grinding!

About posting it. Yeah I'm not a good business guy, but WTH someone will remember me in case this will be used

After all isn't this the place to post ideas and see our favorite producers will take good care of them and make it available to anyone?

Graham, good to see you in full swing. Last time I was in the forum you gave a "arrivederci" to the slot hobby. Yes it is sometime I'm not active here since I've been busy with other stuff (job and model engineering stuff).

Cheers,
JamieG
 

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Giacomo
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667 Posts
Discussion Starter · #9 ·
Ricko, that is also my experience but if tighten the screw with enough torque but still permitting the excessive torque to be taken in the gear you will see the result.
I recommend first oiling the bushes so in the AW the gear seat will also be lubricated.
Then I measure the correct torque keeping the the Allen key (std NSR version= long arm around 12cm) in the screw head and I rotate by hand the tyres making sure the drive is tight enough but still allow the slippery.
I find NSR ultra grip give beat result because the torque necessary to have friction is quite high. With less grippy tyres I'm not sure it will work.

Cheers,
JamieG
 

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3,570 Posts
There is problem is getting repeatable consistent slip.
In my experience, gear slip gets worse with use. Sometimes it'll loose drive all together within a lap or two, sometimes it'll go on in "controlled slip" for quite a lot longer. Sometimes the "controlled slip" phase can be made to last longer by accelerating gently and backing off the brakes - a tactic I've seen used occasional near the end of a race when the driver decides that'll waste less time than taking the car off and tightening the grub screw.

Electronic adjustments in the controller are repeatable / consistent and adjustable at the turn of a knob. The commonly used choke adjustment (or what some makers call "traction control") has a somewhat similar effect.

QUOTE (JamieG @ 5 Jan 2012, 09:18) <{POST_SNAPBACK}>... while with a mechanical friction system you increase the revs of the motor much faster and when the gear get the grip, the motor is in the point of the curve of max torque.
The result is to have a bullet car exiting the curves with the motor screaming.
Generally motors have maximum torque at stall (zero rpm) and the torque decreases as the rpm increase, so there must be an alternative explanation of the effect.
 

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Giacomo
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667 Posts
Discussion Starter · #11 ·
I agree with you that torque is from zero rpm up at a given Voltage. The decrease of torque happen when Voltage is stabilised and rpm are at the max.
The effect of controlled slip is that only when the torque starts to decrease then the gear regain full traction. At that moment you have high Voltage and high torque with the result of a bullet car.

The idea is there, now it is to find a solution to this. I've tested for few thousand laps with the Moslers and it has not deteriorate much but off course it is maybe not a 100% reliable solution. A proper friction system would do it. It is just to find it.
Cheers,
JamieG
 

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300 Posts
Quick question what is the current rating of the track PSU?,

Is that the PSU is bogging down (and loosing volts) due to insufficent amps to drive the high grip locked gear setup, where as the reduced torque allows the volts to stay higher?

Cheers
JCS100
 

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Giacomo
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667 Posts
Discussion Starter · #14 ·
One detail I must point out is that controlled slip works good for twisty sections. In a club track without a twisted section maybe there will not be any benefit.
Please let me know if some of you get the same results as me.
P.S. I just file down the record with a Mosler SW to 4,971s running consistently between 5,050s to 5,200s for many hundreds of laps since the last three days without touching anything. I believe this is thanks to the quality of the hard steel employed by NSR axels.

Cheers,
JamieG
 

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Giacomo
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667 Posts
Discussion Starter · #18 ·
QUOTE (Julian_Boolean @ 5 Jan 2012, 15:49) <{POST_SNAPBACK}>It all sounds a bit Daf 33 to me, and I bet the axles look nice afterwards.

I'm not sure I understand your French but the axles are not that bad

As I said, this is rough / improper / vulgar (put it as you like) but it works at least with the torque I apply to the Allen screw. The slip is limited to few revs just at the exit of the tight bends.
A better engineered solution will avoid any damage compared to long term use of the actual set-up.
I just find it and thought to share it to see if anyone has found it before but it doesn't look like.
So I'll keep experimenting and maybe throw away a couple of axles. I think it is worth trying even if it is a "Daf 33", you never know without trying

Cheers,
JamieG
 

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3,646 Posts
it seems like a disc made of brass copper iron steel plastic, both it and the gear running freely on the axle with a small adjustabe for pressure cone spring would do the job.john. the pressure plate might have to be captive, wont know till i try it but my first rule is KISS.john
 
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