1/8th scale Oval Racing Track
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Welcome to our Hints and Tips section
We have searched the length and breath of the country to bring to you the knowledge of the wise and the experience of the old
Unable to find anyone to fit this criteria we decided to speak to Philip Swales instead,
Those of you that now Phil will agree that someone of his years should have the experience, With Phil's help as mechanic his two young lads, Steven and Richard have reached the top rungs of the sport and can be found at most major meeting doing quite well
So who better to ask advise from on how to setup , look after and race your car. So sit back , read and enjoy the wisdom of the old
I was chatting to John Elliott the other evening and he was telling me about the large-scale stocks and saying how much more realistic they were than the 1/8th scale. Maybe he has a few good points especially with regard to the front beam, but what he said started me thinking. There are a few areas where the 1/8th model BRISCA F1’s very closely mirror their full size brothers. Firstly there is the problem of actually putting one together and making it race durable. The car doesn't come in a glossy box with all the components and a nice set of instructions. Every car you look at in the pits is unique with input from the driver/mechanic/dad to get it together. I well remember the first meeting we did at Bournemouth all these people kept coming over and telling me what was going to fall off the car. The funny part was finding out after a couple of heats that they were right. By the end of the meeting the car was still running, but with a selection of donated parts from people like John Cleeves and Paul Ingram. Now presuming you persevere and get to the point where the car goes round and round all afternoon and the engine doesn't cut out you have just managed to get a foothold on the bottom of the learning curve. The biggest problem is probably yet to be conquered that is how to get the thing to handle. You see preparing full size cars to race on short ovals is much more difficult than Joe public in the grandstand thinks it is and exactly the same is true of our models. That’s what makes it so satisfying when they go well. One thing that the more experienced members in any club need to do (and I think Chessington members are quite good at this) is to help the new drivers through their first few meetings until they achieve a raceable car. So here's hoping the next few hundred words can help you newcomers out there to get your cars to handle.
In the beginning car 352 endured meeting after meeting of totally awful handling, stretching to full seasons the watershed came with two things, first I started to write down what we did each meeting and second I took note of a large part of an article written by Trevor Tennent bless his cotton socks! The base line that you have to start from is of course the chassis and the first thing is to see if it is straight and most importantly not twisted horizontally. To do this make sure the axle beam is bolted on tight then place it on a flat surface. Using spacers between the flat surface the rear suspension pivot pins and the outer ends of the beam, see if the chassis will rock diagonally. I am certain it will I haven't had one that’s absolutely true yet. If the run out is less than a millimetre forget about it, if it is more you can space the beam off the chassis on one side or the other to cancel out the twist. Next thing on the list for a quick check over is the area on the side of the chassis where the trailing links slide/run, I always run with the links sliding in direct contact with the chassis with a liberal helping of molybdenum grease (CV Grease for cars) between the two, which acts as an extra form of damping. Any burs on the axle clearance holes or run outs between different parts of the chassis need to be carefully filed out to get a smooth flat surface check it with a steel rule or engineers square. Once you are satisfied with the straightness of the chassis/beam and the smoothness of the sides of the chassis at the back you can build the whole car up excluding the suspension.
Starting with the front suspension bolt the axle beam to the chassis with any spacers that are necessary. Check you have to two straight king pins to fit and that they slide nicely in the axle block bushes which of course need to be tight in the blocks. (Brand new king pins don't let the axle blocks move easily a set really gets to their best after a few meetings. Likewise new bushes in the axle blocks take a little time to bed in.) Assemble the blocks and king pins onto the beam and attach the steering track rods. With all the steering connected up move the steering and axle blocks to the full extent of their travel and make sure there is no fouling or binding of any of the components. Sometimes you need to move the servo saver up, or put a small spacer washer on the king pin above or below the axle block. Now take the king pins out again and then reassemble the whole thing fitting a hard spring on the outside (Right hand) and a soft spring on the inside (Left-hand) kin pin applying a liberal amount of molybdenum grease to the king pin. (Wash your hands thoroughly after using molybdenum grease and don't get any in your mouth). Check everything moves nice and smoothly. Before we move on to the basic assembly of the rear suspension just a word about toe in or toe out on the front wheels, I try to run with the front wheels as near to parallel as possible when the steering is straight, but applying toe in or toe out can have quite an effect on car stability and turn in. If you toe the wheels in slightly the car will be stable on the straights and have less turn in when it comes to the corner. If you run toe out you will have a car more prone to darting off to one side or the other when it hits a bump on the straight but with more aggressive turn in. Any deliberately set toe in or toe out should be slight, personally I don't use it as it is just one more factor to take account of and if you bend something its easy to set something up straight but difficult to measure toe in or toe out to get it back as it was before.
Before we set up the rear suspension and axle its just worth mentioning the effect positioning of the engine can have on how well the rear suspension works. The ideal situation is to have the centre line of the engine crank and hence the clutch dead in line with the trailing arm pivot pins so there is no alteration to the belt tension as the suspension moves up and down. However this doesn't ever seem possible. In most cases the engine crank centreline is slightly above and forward of the suspension pivot pin which means that the tension will come off the belt as the suspension rises. In this situation engine power delivery and weight transfer will both tend to compress the suspension, a trait which is good for traction providing its not bottoming everything out as soon as you apply moderate throttle. What you must avoid is the engine crank being an appreciable distance below the pivot pin as the belt will tighten as the axle rises spoiling any smooth movement of the trailing links. It's my bet that most people who suffer stripped belts have a large misalignment between the engine crankshaft and suspension pivots. Note: To adjust the engine position whilst still having the correct belt tension, requires a change to the axle gear or belt length. Anyway back to the rear suspension. Fit each trailing link in turn and pushing it lightly against the chassis move it up and down just as a final check that nothing is snagging up, slip one link off again and fit the axle, (if your chassis is open below the axle, fit two springs to stop the axle dropping). Now fit the drive hubs and any axle spacer washers you intend to use, move one end of the axle fully up, and the other hard down. You must still have a small amount of side to side play in the axle when its like this or the suspension will bind up solid when the car is on its maximum roll. If there isn't any play then you will have to reduce the thickness of washers or in the worst case shave a bit off the trailing link axle bush. If everything checks out okay you are ready to assemble the rear axle and links grease the inside of the links liberally especially at the axle end where there is most movement and don't forget to put a new belt on the axle. Now fit the springs and spring spacer washers. Use a nice thin large diameter bur free washer on the pivot pin against the link each side. The springs should have a difference in open end dimension of 3-4mm left to right side I generally set the inside (left hand) spring at 22 or 23mm and the outer (Right hand) at 25-27mm pop another washer on the pivot pin on top of the spring followed by a fresh nylock nut. Then carefully tighten up the nut till it just nips the arm and spring, now back the nut off very carefully till the spring can just pull the arm back to the bottom of its travel. This will give you very close to the right setting, but it will probably be just a fraction tight if the track is bumpy. Fit the hub locks and axle spacer washers and don't forget to locktite the grub screws, same applies to the gear boss grub screws, your suspension is now ready to race. You may find with experience that the rear spring gaps want to be overall up or down a couple of millimetres depending on the weight of your car and the positioning of the hole in your chassis that anchors the top arm of the spring, but the above dimensions should be pretty close. We have had cars close on the max weight limit and well below it and they have still worked out fine. Once you have arrived at a suspension set up you are happy with stick with it and make sure it is the same every time you prepare your car for a meeting. This will give you a baseline to work from. If you alter the springs it can and will have a similar effect to altering the tyre sizes which is something we are just going to talk about. Incidentally when you are altering anything on your cars suspension or wheels and tyres try and do one thing at a time or you won't be able to gauge the effect of each change.
Well that’s the easy bit done, the car is running as reliably as the proverbial Swiss cuckoo clock, the suspension moves as smooth as silk and the engine is a real ripper. If your very lucky you will slap four wheels and tyres on put the car out on the track for heat one and set FTD and never look back. A more likely scenario is that the car will understeer or oversteer too much and you will have to make a decision about changing wheels and tyres.
This is where to the beginner it can become a bit of a nightmare, with people saying you have got to run x amount of stagger or only a certain tyre works (which you have never got in the box). What you need in your mind is a clear methodical order of things to do to try and sort out any handling problem you are encountering. In the main you need to ignore most of what other people are telling you, their car is not your car and the optimum set up for your car may be a lot different to theirs. Just before we talk about changing wheels and tyres let me state what I am wanting the car to do.
I want the car to turn into the corner progressively with plenty of front end grip, however if the car arrives at the corner to fast and you slam on full lock it must understeer a bit (try to push straight on) what it mustn’t do is spin out. Once the car is in the corner I want to be able to apply the power as soon as possible and feed more power on as I exit the corner without the rear wheels losing grip. In dry high grip conditions this should be full throttle once you are nicely past the apex of the corner if everything is perfect. Racing 1/8th model stocks is relatively cheap but there is one area where you must not be mean and that’s your tyres.
Having said that there are a couple of things you can do to get the most out of those black spongy things. Firstly as far as possible I try and run the same compound on all wheels except the outside front. In this way if a try doesn't get chunked it can often be used three times.
So what do you need in the tyre box to cover most track conditions? (Apart from wet weather).
1. A selection of four or five compounds for the outside front wheel.
2. Two or three compounds for rear wheels and front inside wheel. Ideally about three or four brand new in each compound for the outside rear plus a selection of other diameters for use on the inside.
As a general rule the softer the tyre the more grip, the exception to this being when the track is very hot and abrasive in these circumstances the softer compounds can just get torn off and actually provide less grip. When a tyre has finished its useful life on the outside rear and you want to use it again on the inside you will have to true it up again. If you don't have a tyre truer you can use a mains electric drill in a stand and put the chopped off end of an old back axle (a straight one naturally) in the chuck. A tyre for use on the inside rear should be dead straight and have the inside corner (back of the wheel) lightly rounded off. A tyre for the front inside will need a slight taper on it being smaller on the inside edge with once again the inside corner just slightly rounded. The front inside tyre generally wears tapered due to play in the axle block bush on the king pin and clearance between the stub axle and the axle bore in the wheel. Right we are just about ready to bolt the wheels on the car and try it but before we do let me try and explain stagger and corner weight and the effects they have on your cars handling. Everybody seems to run a fair amount of stagger (difference in diameter between tyres on the same axle) on both front and rear of their cars but why?
What’s it for and is it really necessary, Michael Schumacher doesn't seem to use much and he goes round corners OK. Well we turn left all the time with the stock car and we don't have a differential on the back axle so if the tyres were the same diameter one would have to skid slightly (the inside one) because of the difference in radius (and hence circumference) of the corner each one is travelling round. How much does that equate to in diameter? Well if you get out your calculator and work it out you will find it is probably in the region of 5-7mm for a new outside rear tyre of 70mm diameter. Better to express it as a percentage maybe about 8 to 12%, because the actual measurement will change depending on how tight the corners are.
The only draw back to large amounts of stagger on the rear axle is it makes the car want to turn left on the straights as well and as we want stability we have to take this into account. Stagger on the front wheels is only to do with corner weight, as the wheels are free to turn in relation to each other. Corner weight is exactly what it says, the weight pressing down on each one of the four wheels/tyres. By altering the tyre diameters we can change the corner weight and hence fine tune the amount of grip between the front and rear axles without changing tyre compound. In practice you will find that although the optimum rear axle stagger might be say 6mm on a particular track with the tyre diameter you are using, you can get good grip from that amount down to virtually nil. Why is that? Well because as any dragster driver or tyre technician will tell you max force is delivered to the axle/wheel not at the point just before tyre slip occurs but a percentage after it occurs.
In our case it is always going to be the inside wheel which slips first as it is smaller diameter (less leverage on the axle) and has less weight on it when the car is cornering. A very small amount of wheel spin on the inside wheel won't hurt the handling too much. Anyway that’s enough theory for the moment lets get back to the nitty gritty how do we decide what tyres to put on the car. Well start out by going with the rear tyre compound you think will give maximum grip for the track and conditions and put a pair on with approx. 5mm stagger. Always aim for max rear end grip as a car which understeers (try’s to go straight on) is slow but very easy to drive, where as a car which oversteers (try’s to spin out) is almost as slow but near impossible to drive.
Now select an outside front tyre one that you think is probably a bit to hard (less grip) and then an inside front the same compound as the rear axle tyres (remember slightly conical in shape), which will give a bit more stagger than on the rear say about approx. 7mm. Go out and try the car and don't forget it takes a good few laps for the tyres to start to grip properly especially when new or freshly re-trued (incidentally you only true an outside front tyre once that’s when it's brand new) Well what’s it doing? Oversteering or understeering a little or a lot? It might be perfect but it probably isn't.
What ever it's doing (unless its bouncing off into the grandstand on every lap and it shouldn't be if you followed the first part of these notes) there are only two options comforting that – either alter the tyre diameter or change the tyre compound. Obviously on any given day at a particular track there would be a perfect tyre choice for your car but with so many compounds available you could take a hundred and one tries to find it. Therefore what you need to aim for is a baseline set up from which we can adjust things to get a car which is easy to drive and with a good balance of grip front to rear. If you have those two features you will invariably find its quick because you can drive it hard. If you have drastic oversteer or understeer it will probably require a change of tyre compound if it is just slight you may be able to dial it out with changes to the stagger.
So lets take the worst result the car has terrible oversteer and hardly any rear grip. The first thing to try is a different tyre compound on the rear axle and front inside (remember we are only going to change one thing at a time) with the same stagger front and rear as before. Go and try it again if the rear grip is much better you know you are going in the right direction and you might try one more change of compound. We will assume that you have now found your base rear grip compound but the car is still a bit tail happy so obviously we have a bit to much grip on the front axle.
There are as before two ways to solve this, if its quite a lot change the outside front tyre for the next harder one in your range but make sure the stagger on the front end remains the same, by if necessary changing the front inside tyre to suit. Go out and try the car again hopefully the tendency to oversteer will be reduced further. You might have to make one more change on the outside front but lets assume its now somewhere near to balanced. The last little bit of oversteer we can hopefully dial out by altering the stagger front or rear. Reducing the stagger on the rear or increasing it on the front will reduce oversteer or increase understeer. Increasing the stagger on the rear or reducing the stagger on the front will increase oversteer or reduce understeer.
What are we doing? Well altering the corner weights principally of the inside wheels. More weight on a tyre pressing it onto the track equals more grip simple. So in this case as we still have a gnats whisker of oversteer. You can either decrease the inside front tyre diameter a millimetre or so (increase front axle stagger), or increase the diameter of the inside rear tyre slightly (a reduction of the diameter of the outside rear tyre would have the same effect). The closer you get to a balanced handling car the more it will hook up (grip) because you will have noticed a tyre that is working well gets a distinctive profile with a lipped up edge on the side that’s on the inside of the corner. This lip effectively increases the tread width when the car is cornering; you will get this on all four of the tyres when the car is handling really well. Right practice is finished and you are happy with the handling but take it from me it won't stay that way you have got to work at it all the time.
Imagine it's a glorious hot summer’s day and you're racing on a nice relatively clean and therefore abrasive track. What are you going to have apart from lots of fun? Well I'll tell you lots of tyre wear and heat. This will cause two more effects. First if your car is understeering or oversteering a bit 99 out of 100 times it will get worse as the race goes on. Secondly even if you're very close to the perfect balance the car will alter throughout the race. This is because the grip levels will alter as the tyres heat up and if you have heavy wear on the outside rear tyre your stagger and hence your corner weight will go towards understeer. You can counter this by increasing the diameter of the inside front tyre until you feel the outside rear has worn out or you have run out of stagger at the back (watch out for the chassis grounding out). At this point a new outside rear is put on and hopefully you are back to near the original stagger on the rear axle. You need to alter the inside front tyre diameter to reinstate the stagger ratio front to back. Put simply if the car was perfect with 5mm stagger on the rear and 7mm on the front you need to get back to that 2mm difference front to rear. So if your new outside rear gives you 6mm approx. stagger on the back axle you will want 8mm approx. on the front not rocket science really.
Just to make sure we've got the hang of it let’s go through the steps to rectify terminal understeer. Actually I don't mind this so much as if the rear end is sticking like the proverbial brown stuff to a quilt (Don't have blankets now) you have a potentially very fast car. Remember only one thing at a time. Change the outside front tyre for a softer one (assuming its not 90 degrees F in the shade and your currently running a marshmallow) keep about the same front-end stagger and try again. Hopefully understeer is reduced. If you have still got a lot change tyre compound again. When you are getting near to a balance then play with the stagger 1 or 2mm at a time. To cancel of the last bit of understeer (in this case rear stagger is probably pretty close to optimum as the rear is gripping so well) increase the diameter of the inside front tyre (reduce stagger) by a couple of millimetres. Try the car again hopefully it will be pretty good now.
Don't get to the stage where you have no front inside tyre on, or where the car is lifting the inside front wheel coming out of the corner you have then got a very unstable car. Long before you get to this situation you should have adopted another alternative which is to change the outside front tyre for one that has less grip.
If your cars handling suddenly alters don't put your hand straight in the tyre box check the suspension. In our contact formula anything could have got bent or burred up.
Always think ahead to the semi’s and finals and work out what tyres you have left. Its always better to have one good set sitting in the box ready for the final if its absolutely dialled in heat 3 run in a new set of rears in the last heat especially if you've got three good runs in the bag.
Check after each race that the tyres are still stuck firmly to the wheels. A tyre that’s coming adrift can seriously effect the handling and could explode a just the wrong moment. Glue it back with flexible super glue.
Same goes for cuts but be very sparing with the glue.
There is one time when picking other drivers brains is worthwhile and that’s when you go to an away track and you need a quick route to the grippiest rear tyre. Local knowledge can count. If a wheel gets bent throw it away. It may be sad if its got a new UFRA on but it will never work properly.
If the car went well in the final two weeks ago start with the exact same tyres on for today’s meeting.
Sometimes you can almost eliminate the need for practice – very economical that!
Last and biggest hint for the newcomer buy a little note book and write down what you do at each meeting. That way when you come to that cold windy meeting in October, you can look back and see what you did that made it fly at that cold windy meeting in March. The book needs to give you weather, track conditions, tyres, approximate stagger and note the main changes you made.
If you get a really good set up note it in detail you will be amazed at the tricks your memory plays.
I hope this article helps a few new comers and stimulates the more experienced members to bend my ear throw me in the stingers or pass their wisdom to others.
Finally you will notice I haven't said anything about wet weather set-ups. I'm leaving that till later actually just after Alan Green has told me what to do.
The relative distance between the front edge and back edge of the wheels on an axle. Closer together at the front is toe in; closer together at the back is toe out.
The weight pressing down on any one of the four wheels /tyres of the car when it's standing on a flat surface.
The difference in diameter between two tyres on the same axle.
The car try's to go straight on and turns less than the amount of steering you apply to the front wheels.
The car slides at the rear end and turns more than the amount of steering you apply to the front wheels.
We've ask Alan about his wet weather setup so here it is
Turn up at track
Take out car from bag that we throw it in at the end of the last meeting
Charge batteries, bang transmitter to get it to work
Do badly in the heats
End up in the final (for Alan doing good in the heats doesn't make any difference, as he always ends up in the final anyway!, just ask anyone)
End up winning the final
Job done
It's easy when you know how