NSR Mosler friction system

3374 Views 31 Replies 18 Participants Last post by tamar.nelwan, Jan 24, 2012

JamieG

Discussion Starter · Jan 4, 2012

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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Mr Croker

· #21 · Jan 5, 2012

There was me thinking that an electric motor produced maximum torque at standstill.

Since you have a TruSpeed PWM which has a limiting curve on the pulse width and keeping the grub screws tight will have a similar effect.

The only benefit to a slipper clutch would be shocks through the system to smooth the power delivery and prevent the front from lifting after a bump in the track.

I have yet to find a pinion/crown when slightly loose that has lasted a heat on a club night.

But I do have to like the lateral thought process!!

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rick1776

· #22 · Jan 6, 2012

Hi Jamie,

You are running the wrong gear ratio but have found a rather unusual way of finding that out. I would drop 1 or 2 teeth on the spur gear. For example if its currently 26T I would try a 25T or 24T spur.

The torque the motor and gear combo is producing is way in excess of the grip the tyres are able to develop. Hence you have excessive wheel spin as you punch out of corners. You need to reduce the available torque by going to less teeth on the spur.

My rule of thumb in choosing the correct gear ratio is simple. If you need to dial back the brakes using your controller because it pulls up too hard then you are running the wrong gear ratio. Amaze your friend next time by having more punch AND more top end by changing the current ratio you are using.

cheers
rick1776

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slotcarscrapyard

· #23 · Jan 6, 2012

I think the slipper-clutch has a chance here and would'nt be too difficult to try.
Basically you have a loose crown with a friction material one side and a disc fixed to the axle (like a 4wd pulley for example)
You then have a small spring between the chassis and loose crown to keep moderate pressure but allowing to slip under full throttle.

Thinking aloud, maybe a rubber washer between the loose crown and pulley or even directly acting on the inside edge of the wheel?

Got to be worth a try!

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JamieG

Discussion Starter · #24 · Jan 6, 2012 (Edited by Moderator)

I feel it must be disc cups on both sides to withstand for long time. Friction discs and gears should be located on a hollow shaft with one side threaded to have a nut to register the clamping force.
Materials to be used are a question mark. I do not believe it can be anything easily subject to wear, i.e. no Aluminium or plastic, maybe Teflon.
I'm thinking spring steel for the disc cups, steel for gear and bronze for the hollow shaft and nut register.
Another issue regards he space but I am confident it can be engineered correctly.

Just for information, I found some Italian guys made friction systems some 10 years ago but when they tried to industrialize it they realize the component would have been too expensive (100,000Lire... Not £

approx 50€).

Rickxxx
Maybe you are right, I haven't found the right gear ratio even if I tried different ones. Even though I experience that having a friction give real benefits. I'm eager to know if anyone had the possibility to experience it or if it is just a Daf33 as someone mention before.
Cheers,
JamieG

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injectorman

· #25 · Jan 6, 2012 (Edited by Moderator)

Interesting.

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rick1776

· #26 · Jan 6, 2012 (Edited by Moderator)

Always look for the simplest solution to a problem. KISS. Ask yourself what the slipping "clutch" is doing in your set up. It is reducing the effective torque available at the rear wheels!! This reduces the wheel spin when punching out of slow corners. You will achieve the exact same response by reducing the torque in a much simpler manner. Just reduce the number of teeth on the spur gear.

Just try, it should take all of 10 minutes to try. If it doesnt work than continue with your "clutch project". Why look for a complicated solution when a simple one could be more effective.

In fact here is a very simple experiment that will help you decide which gear ratio to use. Place both Moslers on the track at the beginning of the straight. One with the "slipper clutch" and the "standard" one. Just have both controllers set to full on with the track power off. Turn the power on. Supposedly the slipper clutch car will win the drag race. Right? Now go down one tooth on the standard car and repeat. Repeat this by dropping one tooth at a time until your standard set up matches the "slipper clutch" car.

cheers
rick1776

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stoner

· #27 · Jan 9, 2012

jamie g, no teflon! its the slipperiest material known to man, you,d need a moto gp valve spring to even get it to grip. ricks practie is sound as long as you dont overgear it cause this will burn out a motor quite quickly ,if you dont allow the motor to achieve full rpm on your longest straight. in fact some of my hawk motors state on the info not to run them below 3.5 to 1 ratio. john.

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Slotracing Al

· #28 · Jan 9, 2012 (Edited by Moderator)

Changing gear ratios is a very widely used way of tuning slot cars.
It's an unusual circuit where there is one perfect ratio for every part of the lap.
That means gear ratios are usually a compromise and different ratios may be needed for different circuits.

The way to find the best compromise for a circuit is timing laps of that circuit.
Experiments that find the best compromise on only one part of the lap will not necessarily predict the best compromise for the complete lap.

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Steve Hills

· #29 · Jan 9, 2012

Hi Jamie.
I read through your thread, and my advice is to make use of the ACCELERATION control on the TruSpeed PWM controller.
This is there for the exact effect you have been talking about. The idea is that the full power, and therefore torque, are held back by the setting you have chosen so that you can pull your trigger all the way to maximum while the controller feeds the power in at the rate you have set.
Mr Kroker touched on that in his reply too.
Though your loose gear has obviously been effective, leaving it to chance friction will surely be less reliable than using the controls that are in place for that function.
I would be interested to know what you find if you dial back the acceleration control and try your lap record again with the gear tight.

all the best,
Steve Hills

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brembo

· #30 · Jan 9, 2012

I love the train of thought in this thread but ...........

Thank you Steve the voice of reason along with Rik1776

Jamie G what gear ratio are you running?

brembo

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JamieG

Discussion Starter · #31 · Jan 16, 2012

Hi guys, I've been out of reach last week so I missed few posts.
I reduced the acceleration all the way down and increasing it step by step and still it cannot replicate the same effect as the "friction". I played with the different settings of the acceleration curve of the fantastic Steeve's PWM controller but still I cannot beat the 4,9... s result.

The gear ratio I have in the Mosler 1009 AW with "friction system" is the following:
- pinion 7114 AW 14 tooth
- crown 6531 AW 31 tooth
I haven't yet tried a different ratio. I'll try changing the crown (I'll see what I have available in my toolbox).

You can see here my 60 feet track. There are a couple of tight curves and there the friction enters into function. Limited effect is off course reached in all curves or when accelerating from zero speed. The torque to the grub screw is quite consistent, there is no easy slip on it.

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tamar.nelwan

· #32 · Jan 24, 2012

Guys....just My 2 ct's but

1. With PWM or Pulse-width modulation you always have maximum torque available as the full voltage is applied with each "pulse"

2. This slipper clutch idea, if it really works, it should also do so while accellerating on a straight line ( the drag test as mentioned before). But what you guys are looking for ( speially when I look at the numurous 180 corners on this track) is a diff.

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