12th scale help

[tom00182]

Hi everyone,
I have just got my first 12th scale (lmp) chassis as I am going off to uni and will be unable to race my touring car. I have wanted to run 12th since i saw them at my local track but i am a complete newbie and have no idea what i am doing so any advice would be appreciated. I have an Associated 5.2.

At the moment i was trying to balance it out but i can't get it any where near. Any suggestions.

Thanks in advance
Tom

[Xracer]

Well Tom 1/12 LMP is pretty much the pinnacle for sheer speed and adrenaline in the indoor racing world!

Now your plea for help is pretty much an open book of questions but if you need setup information then a good starting point is as the instruction book details, or you can look onto the Team Associated website for some actual setup sheets from various racers and the instruction book if you do not have one.

Tyres are an obvious starting point too but fairly straight forward really but this is only for guidance depending on the carpet type and condition, the club you will race at will give better advice I'm sure!
But for lower grip then Pink (30 Shore) or soft Pink (28 Shore) rear with full width additive, Double Pink (35 Shore) front with 1/3 to 1/2 width additive, from the inside the outside remains untreated.
For higher grip when the track is well 'rubbered in' then Magenta front and rear with similar additive.

I always put fresh tyres on for each heat but some choose not to but you will probably need to reduce the amount of additive for each repeat run.
Tyre diameter has quite an effect on handling and the top racers will have trued theirs down to something quite a bit smaller than as supplied.

Gearing depends on motor choice and track layout, something around 65mm/rev is not a bad staring point depending on your motor timing setting, 20-25 degrees is probably a safe starter, for a fast open track gear slightly higher. Blinky esc setting and 10.5T motor for standard class or the world is your oyster for motor wind and timing boost in modified (insanely fast).

Now the 5.2 does not give much option for lateral balance so just go with the standard layout of longitudinal lipo, speedo opposite side towards the rear with receiver just in front.

Ensure the diff does not slip when gripping the rear wheels and trying to turn the spur gear but do not over tighten either.

Steering travel should be set to give around a 1 metre turning circle and be equal in both directions when you hand push the car.

I'm sure the guys you get to race against will help if asked, except for the aholes of course!!!

Enjoy!

[tom00182]

Thanks for the advice.
I was only concerned as under initial acceleration the car veered to the left where one side had significantly more load than the other but i have reduced the impact of the issue now. Thank you for the tyre suggestions almost completely new to foams so thanks for the tyre suggestions i will ask around when i get up there.

[mark christopher]

When you say balance, how are you checking this? Tweak is one of the biggest things on a pan car

[tom00182]

At first I used the spikes using the small holes at the front of the chassis and the back of the pod but it was tilting and i couldn't move the electrics around in order to balance the chassis so i put them on a corner weighing system to see what the difference was and there was some 50 grams difference between the front right and left tires and the cross chassis percentages were around 60:40.

The springs on the braces where wound until they just touched so there was no compression and the pod had free movement so i couldn't see anything that would cause that much of a difference.

I ran the car after his in the front room and any kind of acceleration from a standing start made the car pull majorly. since then i rotated the battery 180 and it has reduced it but there is still about 30grams difference on the front wheels

[tom00182]

the chassis and pod are flat btw there is no tweak in the car that i can see

[Xracer]

The levels of tweak Mark has eluded to cannot be checked by eye, the car has to be fully laden and its wheels on a suitable tweak gauge, very small degrees of tweak will cause a pull on acceleration and/or braking.

A slipping diff is another culprit.

My 5.2 is not fully laterally balanced either.

Do be aware that a corner weight system can have inherent errors too, especially if each of the balance pads are at different heights relative to your setup board, this will cause an apparent tweak giving false individual corner weights, I had to modify my system to allow height and tilt adjustment of each corner scale to create an effective flat plane!

Ah the joys of our hobby!

[mark christopher]

To check tweak, put tyre on car same size a cross axle,
Place a pound coin on top of each front wheel, just forward of axle so look at left wheel and about 5 to 12

Gently lift the front of the chassis in the centre with a model knife or fine Alen driver,
If the left coin falls off 1st (left of car) ad preload to the right rear spring, and to maintain ride hieght remove preload from the left rear spring.

Keep going till both coins fall together

[Xracer]

A £2 tweak gauge, quite a bit cheaper than Hudy's offering!

I must admit I have never tried that technique as it also relies on having even droop as you are unloading the front springs when lifting the chassis, this is probably fine for a 1/12 front suspension with a static lower wishbone though.

[mark christopher]

It's how all the top 12th guys do it, I have a laser tweak station, but above is how most do it

[MattW]

It's a flash way of doing it!! Most people use pennies!

[tom00182]

Thanks for the advice my dad has been racing gt12 so i am aware of the coin trick and have used it the coin trick and both coins did fall together and the diff if you hold both the rear wheels you cannot move the spur there is no slipping. Is there anything else that could cause that sort of thing

[tom00182]

I used 20 pence coins

[tom00182]

put tyre on car same size a cross axle,


It might just be me being stupid but does that mean the same size front tyres?

Just wanted clarification

[mark christopher]

It might just be me being stupid but does that mean the same size front tyres?

Just wanted clarification


sorry across axle is same left and right, so same size front, same size rear, front to back can differ :thumbsup:

[tom00182]

Okay thanks for the clarification both tyres on the front are just a shade over 44mm and the tyres on the rear are slightly larger but they are all more or less the same size

[tom00182]

Where would you say is a good place to start in terms of truing down the tyres? I know they are supposed to be at their fastest when they are smallest but that will shorten tyre life so where is a good place for a newbie to start

[tom00182]

I also need to cut out and mount the bodyshell does anybody have any tips for that?

[Xracer]

The starting size really depends on yourself, sponsored drivers do not really have to consider tyre life so can start as small as they like, us chaps that pay for our racing draw a compromise but when you consider that you can destroy a tyre in one heat as well!

I start at 46mm rear and 44.5mm front, some of my mates start 1mm smaller than that, so as I say, the choice is yours!

Happy grinding.

[tom00182]

Okay thanks for the input

[mark christopher]

id go with xracers recommendations on size

[tom00182]

Also does anyone have any tips for cutting out and mounting bodyshell (in terms of positioning )

[mark christopher]

ill post some help tomorrow, is it painted or clear?

1st best tip is mark and cut before you paint it

[tom00182]

It is clear

[Chequered Flag Racing]

Here's video one of three on LMP12 setup from top racer Robert Krens.

-ct2L3KEkE0

[Xracer]

Now this is a topic that will bring lots of different approaches so I will table this one as a beginners starting point but you will see that there is equipment that you can buy or make to make the task very easy.

You also need to be aware that some shells are not very accurately marked especially the positioning of the front wheel arches relative to each other.

So start by trimming the side sills 4mm below the cut line, you can trim the front splitter and rear valance (assuming GT12 here) to the line but leave the wheel arches intact.

The 4mm surplus allows the shell to sit on your work surface when positioned over the car without the body posts fitted, the car should be set at its ride height of 3.5 - 4mm, you can then move the shell around to align the front wheels within the marked wheel arches, it is here were you will see how good the shell is marked!

The rear arches invariably do not align depending upon the wheelbase the shell was designed for originally and you may have to compromise on the fore and aft positioning!

Take a marker pen and mark the centre of each wheel axle as accurately as you can.

The best way to cut the arches is to use a compass cutter available from some model shops, online and elsewhere, set the size to clear your chosen tyre diameter, I go for around 3mm clearance, then trim the arches to complete along with the sills, smooth the edges of the arches at least, the shell can cut a tyre on impact.

The body post mounting holes can be done numerous ways, some choose to do them before the arches which I do now as I have made some adjustable posts that I can raise to sit the shell at the right height, on top of each is a small button magnet now sold by some of the model car dealers.

So I adjust each post to set the trimmed shell level with the chassis, i.e. 4mm above the work surface, drop a button magnet on top of the shell at each post, these magnets have a hole through their centre, align the shell and mark the post positions. I would then mark the wheel arch centres at this stage too.

I hope this all makes sense, it is an onerous task until you get your methodology sorted so do more then one shell, you will soon need a second one, I do three or four at a session and paint them too! Yeah I crash a lot!!!

[tom00182]

Okay thanks for the advice.
Thanks for the video chequered flag racing. I have watched it already but it is all a bit double Dutch to me at the moment

[mark christopher]

My way is to cut body to lower cut line, rest body on car and Mark body posts, make holes with body reamer, mount body and adjust hieght of posts to correct posistion, then mark the centre of each axle/wheel nut, use a compass cutter, don't cut just score and flex and peal apart

[Xracer]

Mark's method is indeed tried and tested but only if the body posts are already set at the right heights for the body to sit parallel to the work top.

If it is your first shell on a new car or a different style shell on an existing car the posts will not yet be set to suit the body style, so ensure the shell is set level or the wheel arches will end up miss-positioned.

[beale]

Start with them as they are your not looking at winning everything! Trueing is the next step just get some laps in getting used to the speed these things carry through corners and keep rotating tyres, slowly you true them down a bit. After a couple of meetings get Trueing and be amazed what goes round a corner!!!

[tom00182]

Thanks for all your help. Raced the car for the first time this morning and stuck it 6th in the A final (7 cars per final) out of the 14 drivers. Really awesome car to drive. Unfortunately the motor moved in the final and stripped the spur. Is the motor moving a common problem because that would be the third time it has moved in the short time I have had it. I am doing the motor screws up as tight as I can.

[mark christopher]

Which car is it?

[tom00182]

X12 15 my dad wanted the associated

[Chequered Flag Racing]

Is the motor moving a common problem because that would be the third time it has moved in the short time I have had it. I am doing the motor screws up as tight as I can.

Only in a big shunt or if not tightened up correctly.

Are you using washers behind the motor mounting screws?

[tom00182]

I put some shims in yesterday which reduced the problem but they were only small

[SlowOne]

To stop a motor from moving in a shunt...

Make sure that you have steel washers under the head of the motor screws, the larger the better. On some cars you can't use one any bigger than the head on the lower screw as the lower pod plate sticks out beyond the motor mount and a large washer will foul it.

Find yourself some used 600 grit Wet 'n Dry paper. If it's new then get something like an old diff washer and rub it across the paper 30 or so times to knock the edge off the grit. Alternative is 1000 grit, but since one never uses that for anything else its a bit of an expense!

The problem is that the surface of the anodising has a low coefficient of friction. Take the wet 'n dry paper and very (VERY!) gently rub it across the motor plate where the motor fits against the plate (the inside of the motor plate) so that you take the shine off the anodising, but don't take the anodising off. It should look like a matt finish now. This greatly raises the coefficient of friction making it harder for the things to slip.

Now do the same on the motor. Again, take the shine off the anodising, not the anodising off the motor plate.

You can be a bit more aggressive than you think once you get the hang of it. The surfaces should look matt and scuffed, not scratched and damaged. If you do knock the anodising off the odd corner don't panic, it won't do any harm.

Now clean both surfaces with some brake or motor cleaner and leave to 'dry'. Re-assemble as before. Do not keep tightening the screws to avoid the problem, you will damage the threads in the motor plate to the point where they won't hold the motor in properly, or will strip.

The combination of the steel washers and the scuffed surfaces should prevent the problem happening again. As, of course, will driving better and not hitting the barriers in the first place!! :p

I hope that does help. :)

PS - take those shims out! They will not fully support the motor which makes it more likely you will bend a motor plate in a shunt. Motor to plate only please! ;)