[Nonfractal]

Jeremy, 
I've only used grub screw fitted pinions once and didn't find any advantage in them. 

I've used slot-it Ergal, NSR brass and AllSlot steel pinions and really dont see any difference in them. 
The wear on a pinion seems to be on the friction fit surface ( as it gets fitted and removed ) rather than the tooth face.

I've never been a fan of nylon pinions and avoided them for the longest time. 
The Ninco angled  ones were particularly bad. 
However, when Giovanni released the ThunderSlot Lola, it came pre fitted with a nylon pinion so I gave it a go.
The thunderslot drive train is very good. I've bot had any reason to complain apart from the selection of available gear ratios. 

For me, the materials come second place to "size and fit" when selecting gears. 
Modern manufacture and materials are really quite good.
Alan

[BAracer]

Thanks Alan.

I was curious why the manufacturers offered gears in different materials, as the market often gets reduced down to the best selling item. So I was wondering what was driving the range of available materials.

Having come from a cycling background where minimising power loss in the drivetrain is a big focus, I am very conscious that selecting the right gears and optimising the set up is a basic essential.

[Nonfractal]

A long time since I OPd this thread.
I made several references to "diligent preparation" during the discussions above.
When preparing a pair of NSR corvettes for racing g at NascotWood (tomorrow) I made some mental notes of the preparation process.

Flossing:
Dirt ingress always occurs on gears.
Some lubricants attrract and hold more that others but one way or another dirt will accumulate, especially in the tooth gap. 
When dirt sits in the inter tooth gap, It will eventually begin to get compresed by the opposing tooth.
When that compression occurs,the gears will not run smoothly and you will eventually get to a position where you have a notch in the cycle of the gears. 
I use zippo and a toothbrush initially which is normally enough to remove the debris.
An ultrasonic cleaner can also be very useful to get dirt out of gears. 
If zippo and ultrasonics do not work, tooth floss (honestly) or in the extreme, a scalpel will be needed to scrape out the dirt. 
When the gears are clean and will formed and the backlash is set correctly, there should be no perceptible "notches" felt in the gear's cycle.
Many ask me how my cars run so quietly, now you know 
Alan

PS 
Tamar re :  DiSCA gearing. 
I don't think your explanation works.
PWM controllers (like the SCP2) use the same method as the on board digital chip to  control power delivery, yet switching between a resistor controller and an SCP has no impact on gearing (that I can perceive)
However, I don't have an alternative explaination for the reason that DiSCA cars are geared the way  they are. 
Maybe the on board chip has some characteristics that neither of us know about.
Only Maurizio could explain this I suspect.

[Kevan]

Rollout...a 1/12th racers favourite tuning option is the quick way to repeatable performance as tyres wear. Although not as critical as on said 1/12th as they go off-the-pipe quickly as the rear foams wear (even between race heats) but it's still useful to know about for your slot cars.
My favourite rollout app is RC-FDR Rollout Free (android) but you may have to double the sizes as its not written for 1/32 cars but works great.

[Nonfractal]

It's been a while since I updated this thread with new Info. But a recent question (in another thread) prompted me to revisit this subject 
Slot racing and tuning is a learning curve that never flattens out 

Reviewing the GasMonkey team chat log from the 2022 24 hour Derby LeMans oxigen event, I was reminded of this gearing issue.
   

The monkey  yellow scaleauto corvette suffered multiple pinion failures during the 24 hours. 
This is a slot.it ergal 6.5mm 14 tooth that was being used to drive a nylon anglewinder and you can see that the pinion is splintered.
Surprisingly, the nylon spur was not damaged in the same way.

You can see on the tooth profile that the pinion has more teeth than the diameter of the gear would ideally allow.
For sprint racing, the compromise would be a acceptable. For 24 hour racing, it proved catastrophic.

For 14 tooth, the ideal diameter to preserve the perfect modulus  is 8mm.
A complete rethink of suitable gearing will have to be done prior to the next event. 

AlanW

[Kevan]

I don't use pinions like that period.

Do the rules not allow for movement of the motor? moving it 0.75mm forward would get rid of the problem and allow use of an 8mm pinion.

[BAracer]

I find it's a balancing act. I start with the preferred ratio I want, e.g. 3:1 and then I look at all the various diameter pinions and AW/SW gears that get closest to it following the golden rule.

[Nonfractal]

This is my crib sheet for pinion diameter versus tooth count

Ideal pinion diameters for 05 modulus
5.5mm 9 tooth
6mm 10 tooth
6.5 mm 11tooth
7mm 12 tooth
7.5mm 13 tooth
8mm 14 tooth

When putting cars together, I try to stay as close to this as possible.
I'll use a stretched pinion (fewer teeth than ideal)
rather than a squeezed pinion (more teeth than ideal) if I have to.

[BAracer]

Ditto, and whenever necessary, I tend to vary the crown/spur gear count rather than tinker with the pinion, to optimise a gear ratio.

[Kevan]

As a rule-of-thumb 3 teeth on the spur/crown is the same as 1 tooth on the pinion...ish, it's always best to fine tune with the spur/crown.