Transmitter Settings in 1/12

[Dal]

Hi all,

I drove a 1/12 RC125.1 (10.5T) at Ardent for the first time today and all I can say is wow! - Totally loved it.

Previously I have only used 1/10 TC and I was getting tired of having to mess around with the complex chassis, I've only started getting into RC since April and have been spending more time off track with setup of 1/10 rather than on track.

With 1/12 the car just handled so well and I could concentrate on 'driving'. I bought it off oople and the car was already setup for carpet.

I noticed that the car would often oversteer, I think this might be down to the fact that the EPA/dual rate on my transmitter is too much for 1/12 (100% - DEFAULT).

Could you please share any suggestions about how you have adjusted your transmitter settings for 1/12... (Steering/Throttle/etc)??

I know its down to personal preference but it would be good to get some common ground.

Ps. My Radio is a Sanwa Exzes-X (I can adjust a lot of things).

Thanks.

[kayce]

Originally Posted by Dal

I noticed that the car would often oversteer, I think this might be down to the fact that the EPA/dual rate on my transmitter is too much for 1/12 (100% - DEFAULT).

The way I learned to set my steering on a 1/12th car, was to set the max steering so I could do a complete circle/donut in one lane of the track - and that way steering is set dependent on lane width - so, if you used less than 1-full lane then you need to lower the percentage on the dual rate on your transmitter (I've NEVER needed 100%, usually 70% was a good starting point).
Otherwise, if you're still suffering from oversteer it tells me you might have too soft a tire on the front (or too hard a compound on the rear, or even matching compounds), as it's been my experience that most cars perform better with with harder compound tires on the front compared to the rear.
I don't know if you're using traction comound/tyre goop, but I've found that most guys suffering from oversteer used too much on their front tyres (I hardly ever use any on the front, usually rears only).
Also, if your diff is set too tight it can show as oversteer (even on carpet you need a little slippage)

[TrevCoult]

This might help you to a degree.

http://www.carsrcracing.co.uk/?p=180

Trev

[Dal]

Originally Posted by kayce

The way I learned to set my steering on a 1/12th car, was to set the max steering so I could do a complete circle/donut in one lane of the track - and that way steering is set dependent on lane width - so, if you used less than 1-full lane then you need to lower the percentage on the dual rate on your transmitter (I've NEVER needed 100%, usually 70% was a good starting point).
Otherwise, if you're still suffering from oversteer it tells me you might have too soft a tire on the front (or too hard a compound on the rear, or even matching compounds), as it's been my experience that most cars perform better with with harder compound tires on the front compared to the rear.
I don't know if you're using traction comound/tyre goop, but I've found that most guys suffering from oversteer used too much on their front tyres (I hardly ever use any on the front, usually rears only).
Also, if your diff is set too tight it can show as oversteer (even on carpet you need a little slippage)

You may well have it figured out my friend

I was using a fresh pair of MOBGUMS double pinks on the front, and yellows on the rear.... I was advised this would be a good starting point for 1/12th on carpet as 10.5 stock spec?

I did apply CS High Grip compound, the usual process of coating the rears first following by the front later, however I applied the compound to 100% on the rears, and 75% on the fronts.... I was looking at Olly Jefferies spec sheet for Ardent... was 75% perhaps too much?

The car feels very well balanced, its just that when Im turning on the the Radio (Stick) I feel like the steering servo has too much range, producing an oversteer effect?

Ps. Thanks for the link trev.

[SlowOne]

Set your turning circle to be somewhere between 3 and 5 feet. With 2x pink apply 50% width additive on the front and set the turning circle to five feet. If you need a bit more steering reduce the circle a bit. Too much additive will make the car oversteer whatever you do to the rate, as will too soft a front tyre. Your current combination is fine for Ardent. Ignore the amount of dual rate people use, as that number depends on all sorts of things to do the Txs and steering geometry differences. Use the diameter of the turning circle as your guide, not a rate number.

Make sure your car turns even diameter circles left and right on full lock - there's a description of that on your RCTech thread.

With respects to Kayce, the 12th differential is the key to good handling. 12th diffs need to be glass smooth and have no slip whatsoever. If the diff is in the least bit tight, the car will tend to understeer in and oversteer out of the turn. 12th cars have to rotate in the turn, and the diff is the key to that. Ignore all you've learnt from TC on setting diffs to give you a bit of drag or limited slip - the 12th diff must be completely free in rotation yet have no slip at all. HTH

[kayce]

Originally Posted by Dal

You may well have it figured out my friend

I was using a fresh pair of MOBGUMS double pinks on the front, and yellows on the rear.... I was advised this would be a good starting point for 1/12th on carpet as 10.5 stock spec?

I did apply CS High Grip compound, the usual process of coating the rears first following by the front later, however I applied the compound to 100% on the rears, and 75% on the fronts.... I was looking at Olly Jefferies spec sheet for Ardent... was 75% perhaps too much?

The car feels very well balanced, its just that when Im turning on the the Radio (Stick) I feel like the steering servo has too much range, producing an oversteer effect?

Happy to help

With yellow rears, if you're getting oversteer you might want to try either Lilac or Purple fronts. Otherwise, with Double-Pink fronts you might want to try White rears.

The method I learned for applying traction/grip compound was:
1) Only use it to address a problem - and being as you usually need more rear traction, that you start there first (and not just randomly apply it to both front and rear tyres). Only if you need drastically more steering, and then only if you don't have softer tyres available, do you apply it to your front tyres (should be more rare than an actual practice).
2) Always start by applying it to the inside 25% of the tyres, on either end of the car, and if additional traction is needed increase the amount (50%, 75%) until you have full coverage.

But to address oversteer remove steering range (turning down dual rate), as these cars have more steering built into them then we'll usually ever need.
A smooth, and regularly rebuilt, diff is one of the final keys to a happy-performing 12th car. No-slippage, and it'll be an understeering beast that won't turn going into a corner and an oversteering and hooking beast coming out of a corner; too-much slippage and you won't be able to accelerate out off the line or out of a slow speed corner. While learning to adjust your diff is a "feel thing," something only learned by trial and error, (no disrespect to slowone) you need some slippage if even just a little or you just end up prematurely wearing out diff parts.

[Jason A]

As someone new to 1/12 myself the biggest thing i found that helped is turning the physical amount of steering down to whats needed for the track.

when i first started it was set to 100% and the car was super twitchy.

It is now set to around 50% which has made a massive improvment.

Also set you exp on your steering if possible to -15.

[SlowOne]

Adding to Kayce's advice on tyres, if you can't get yellows to give grip for eight minutes then try pink rears. Rears should be pink or yellow for mere mortal drivers, the Olly's of this world can drive magenta rears but most of us can't!

I'm not sure what Kayce means by slip in the diff. If it means lossening the diff until it slips when you punch the throttle, then that is not good advice. A 12th diff must never slip at all under any conditions. It must, as Kayce says, be smooth as silk in action.

You can turn a 12th car into an understeer in, oversteer out machine by having a diff that is stiff or notchy in action. Stiff, as in overtightening a TC front diff to get more traction out of a corner, or notchy as in when you turn it it feels like a ratchet. A 12th diff must be glass smooth in action. If you contra-rotate both rear wheels, it should have no resistance at all; with strong motor magnets you should be able to get the diff to work without turning the motor.

At the same time, there must be no slip at all. Grasp the right rear wheel in one hand, with you thumb and index finger holding the spur gear. Now try and turn the left wheel with your left hand. If you can get the diff to slip (the left wheel turns) it is too loose. If the left wheel won't turn (give it a good try, but don't wrench it) it is set right. Now try contra-rotating the wheels. If you can feel any resistance, then rebuild it again.

Try the diff of any 12th National A finalist and this is what you will find. Smooth is in, slip is out! If anyone would like a demo of how to build a diff like that, then please ask. I can get down to Ardent most weekends and would be happy to bring my kit down and help anyone learn how it is done - once seen, never forgotten! PM me if that helps - I'll be down there this Saturday - and I'll give you contact details.

Good to see such an interest in 12th, so please don't hesitate to come on here and ask questions. Our next National is at Hereford (see www.brca.org, 12th Section, for details) and after that there is one at Tamworth in December. Come into the pits are ask any of us for help, we're pleased to sort your cars out, give you all our set-ups and loan you bits to try if you need them. HTH

[kayce]

Originally Posted by SlowOne

I'm not sure what Kayce means by slip in the diff. If it means lossening the diff until it slips when you punch the throttle, then that is not good advice. A 12th diff must never slip at all under any conditions. It must, as Kayce says, be smooth as silk in action.

NO, what I "mean" is that when holding both rear tires you should be able to get the diff gear to move (even a little) for your initial setting - and then adjust it on the track depending on available traction (tighter on high traction surfaces, looser on more slippery surfaces). In my experince, diffs that don't slip at all just end up making the car harder to drive, and wear out diffs (diff balls, diff rings, bearings, etc) prematurely. If balldiffs weren't intended to slip, then we'd all still be using geardiffs like they were back in the good/bad old days.

Again - we're just going on personal preference here, not sure there's a right or wrong answer, as in driving other top racers' cars nobody's going to be set exactly the same and nobody's going to have the exact same tires, set-up, or diff settings.

[SlowOne]

OK, then we'll agree to differ. I'll just say that no driver I know who qualifies in the top 30 at a National would ever run a 12th diff with any slip in it. If you need to control wheelspin, use the throttle. A slipping diff will never get you off the line in a final, and at 0-30 in 1 second, any slip loses you places at a huge rate!!

We don't use gear diffs because they are not smooth enough for a 12th car. When Cecil Schumacher first had the idea to make a diff for a 12th car, he made a geared diff. When he took it to Wes Raynor at Mardave for his opinion, Wes said it was a great idea, but could Cecil sell it for a fiver? Realising he couldn't, and that a geared diff was not smooth enough for a 12th car (too much backlash between the gears as you go on and off power), he set about finding an alternative.

The answer he found was the mechanism we all use today that he originally saw in a machine for measuring gear forms and pitch. Since the measuring machine had to rotate, but any backlash would mean large inaccuracies in the measurement, they used this system of two ball sets between thrust races - effectively a geared diff with an infinite number of teeth, but no need for any clearance (backlash) between the 'gears'. Cecil adapted it to a model, and the rest, as they say, is history.

The original test diffs were made by turning the gear off a Mardave wheel, drilling holes in it, and making parts to hold the thrust washers. Another Mardave wheel was then turned up to mate with the thrust washer holders and viola - the ball diff was born.

The original ones sold for about £6 if I recall correctly...