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"The weight is probably the really important feature, plastic pinions weigh about 1/5 of metal pinions, improving the inertia while speeding up and braking."

Really?? People can measure/feel this difference????

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rick1776
 

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QUOTE (Coopdevil @ 3 Sep 2012, 08:26) <{POST_SNAPBACK}>The next logical step in this kind of component lightening must be to introduce plastic wheels and save weight by not using a metal grub-screw but instead knurling the ends of the axle...

Now youre just being silly.....


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rick1776
 

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MB slot,

In theory I have no problem with the fact that you have reduced the inertia of the pinion by going to plastic. In practice you will need a timing system better than that used to time a luge run at the winter olympics, to "measure" any difference if it exits. Do some back to back tests and get back to the forum with your results. Happy to be proven wrong.

The reduction in inertia by going to a hollow rear axle which is 1g lighter that a standard axle is the same as removing 0.003g from the weight of a tyre fitted to that same axle system. You would probably lose that much rubber form the tyre after a couple of laps.

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rick1776
 

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Hi Marco,

You may very well have reduced the lap times in your testing. Would be great to see the test results.
The reduction in lap times would not however be due to the reduced inertia of the pinion. Perhaps the all up weight of the plastic pinion and spur is 0.5g lighter compared to metal gears? On a magnetic track a 0.5g overall reduction in car weight may be noticable.

If you wanted to test that the reduced lap times were due to a reduction in inertia then to make the test fair you should place an extra 0.5g of weight very close to where the pinion and spur are located. That way any change in lap times would be due to the reduced inertia and not just a reduction in the overall weght of the car.

By the way I have no problem with the concept of plastic gears. Done well they wear a lot better then metal gears.

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rick1776
 

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QUOTE (Mr Croker @ 4 Sep 2012, 21:18) <{POST_SNAPBACK}>Rick - I do not get the maybe points you raise. Whilst 1g maybe not seem a vast amount as a percentage of a slot car let's say is 1.5% roughly. Weight in the drive train has effect of adding to the flywheel effect and therefore directly influences the acceleration and braking performance. Digging through Marco's performance parts from the excellent magnesium wheels, gears, interiors etc saves a huge %.

Rubbishing it from a position of ignorance is foolish.

You could
be right about the tyres. I remember watching a well known international racer run through setting a car up for a race in the UK. A tyre box was brought out all of the same compound and wheel, each pair 0.1mm different in diameter. Everything was considered.

Sorry Croker just saw your post. Im not rubishing the product, it may very well be the best thing since sliced bread. I weight saving of say 0.5g in a magnetic set up car would produce a measurable gain, Im sure. Im querying the claim that the reduced inertia of the pinion is the reason for the measurable gain. Simple physics will tell you that it will have reduced inertia. I cant argue that. What Im arguing is that it would almost be impossible to measure in a practical sense. Its like the claims you see that say by using this super duper oil your motor will gain an extra 8.2356 rpm. The diffrence between a cold motor and a fully operational motor is easily 500+ rpm and youre claiming to be able to tell that its 8 rpm faster because of the oil??? Give me a break.

Set up a drag run. Measure the elasped time with a brass pinion. Replace the brass with a plastic pinion. But make sure to add the weight difference so that the car's overall weight does not change. Repeat the drag race run. Now you will be testing the effect of any reduction in inertia. Do the run 10 times and take the average. Repeat with the plastic pinion. I suspect that the variation between any two runs will probably be greater than any "measurable" gain. Once again happy to be proven wrong, but pleased show me the data.

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rick1776
 

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Spot on Mr Croker, thats what Im saying. A 0.5g weight loss in a car weighing about 85g, thats about a 0.6% weight loss. In a mag car thats probably noticable. In a non mag car it would be marginal to pick the difference.

Im using a hollow axle as an example and saying that if it is 1g lighter than a standard axle you would achieve the same inertia improvement by removing 0.003g of mass from the tyres. Thats 3 milligrams. So lets keep the solid axle in place and remove 0.003g from the weight of the tyres and I would get the same benefit. I defy anyone to say they could notice that the car felt "faster" and spooled up quicker because it was now 0.003g lighter.

The gain in reduced inertia between a brass pinion and a plastic pinion would be very small. Brass pinion is 0.05g?? So 1/5 of that is 0.01g We have a weight saving of 0.04g. Like I said im happy to be proven wrong but show me the data. Send a packet of pinions into this forum so that one of the moderators can do a back to back test. Happy to eat humble pie.

If anything Id say there was more gains to be had by reducing the friction between pinion and spur if the gear profiles were done well.

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rick1776
 

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QUOTE (Mr Croker @ 7 Sep 2012, 08:24) <{POST_SNAPBACK}>So you do not get the irony in the fact lighter makes it quicker but apparently not when it's a pinion. Hmm....

In all my years of club racing i have yet to hear anyone say, "....and when my wing mirror snapped of in that last crash, I couldnt believe how the lap times just tumbled". We are after all talking of a weigth saving of 0.04g at best.

Like I said Im happy to eat humble pie with blind back to back tests and defy anyone to pick which car has the plastic pinion fitted.

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rick1776
 

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QUOTE (Bigtone @ 7 Sep 2012, 15:43) <{POST_SNAPBACK}>A couple of important things to consider when picking a metal or plastic pinion are the motor torque and how hot it gets. I don't think a plastic pinion would last long on a Wasp,Super 16D, Falcon 7 or Group 12. I have suffered the Proslot split pinion but that's just down to poor quality and not being plastic

I did use a plastic pinion in my 1/24 racing with a motor having about 220g.cm torque (came with the motor). It did last the season (10 races) and then spun after the race when I was practicing/tuning after the last round. Got lucky. A friend of mine who I was neck and neck with in the championship spun his pinion in round 7, cost him the championship. I usually use a metal pinion and plastic spur with metal boss and grub screw. It works well. Plastic pinion and plastic spur with no grub screw.....Hmmm.

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rick1776
 
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