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Tech Champion
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By far the two coin method is the fastest way to insure the front is balanced.
I agree that the rear is what it is and no need to check it for balance.
I have used both the tweak station and the coins to great satisfaction.
I agree that the rear is what it is and no need to check it for balance.
I have used both the tweak station and the coins to great satisfaction.
Here's a question for you regarding setting the tweak, do you guys set the tweak using 'used' tyres? Normally the larger sized tyre goes on the outside, so do you set the tweak then, or when the tyres are trued to be the same size? The only reason I ask is that it seems to me that if the tyres are diferant sizes, and you set the tweak using them, then, as soon as you run your car, the setting will go out as the outside tyre wears more than the inside. I have a set of CRC high roller rims with a O-ring superglued to each, and use them to set the tweak. Then, I put the wheels/tyres on that I am giong to use. Does anyone else do this?
Tech Master
And that is exactly what baffles me regarding setting the tweak! If you set the tweak with tyres that are differant sizes (larger on the outside), as soon as the car starts to go around the track, that tweak setting will go out, as the outside tyre starts to wear. With using the 'setup wheels' I discribed earlier, yep, the setting will be off to start off with, but as the outside tyres wear, you'll end up with a 'sweetspot' where everything is spot on. Then, of course, as the outside tyre carries on wearing, the setting will go out. My question is, overall, do you get a better running car with a 'swetspot', or is it generally better to go with a tweak setting that will be out after a few laps?? It used to be much easier back in the day when Corally cars had a free floating rear end, no tweaking needed!! Cheers guys, Chris.
And that is exactly what baffles me regarding setting the tweak! If you set the tweak with tyres that are differant sizes (larger on the outside), as soon as the car starts to go around the track, that tweak setting will go out, as the outside tyre starts to wear. With using the 'setup wheels' I discribed earlier, yep, the setting will be off to start off with, but as the outside tyres wear, you'll end up with a 'sweetspot' where everything is spot on. Then, of course, as the outside tyre carries on wearing, the setting will go out. My question is, overall, do you get a better running car with a 'swetspot', or is it generally better to go with a tweak setting that will be out after a few laps?? It used to be much easier back in the day when Corally cars had a free floating rear end, no tweaking needed!! Cheers guys, Chris.
wingman2-
I think setting tweak for the 'sweetspot' will depend on how many laps you can put in at the 'SP'. personally I don't remember the last time I actually put my car on a tweak station. I just make sure my tires are the same size and that nothing has come loose on the chassis to make it out of balance and just go racing. Maybe I'm not good enough to notice. I'll have to check my lap times. I don't think the times change much if at all.
E
I think setting tweak for the 'sweetspot' will depend on how many laps you can put in at the 'SP'. personally I don't remember the last time I actually put my car on a tweak station. I just make sure my tires are the same size and that nothing has come loose on the chassis to make it out of balance and just go racing. Maybe I'm not good enough to notice. I'll have to check my lap times. I don't think the times change much if at all.
E
Tech Champion
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Maybe putting things into proper perspective would help.
I rotate my tires side-to-side during the race day and find that this does a very good job keeping my tires reasonably even. RARELY do I find the tires to be even .25mm off from each other after a heat where they started even, but let's pretend I did.
.25mm is roughly equal to 1 hundredth of an inch. That's damn small. NOW, divide by two because that's how much a .25 diameter change affects relative height of a corner. So now we're talking about .125mm or 5 thousandths of an inch. That's REALLY damn small. Can that difference be measured in tweak? I'd offer that it's unlikely with any but the absolutely most sensitive methods (which I'd argue my scales to be) and maybe not even then.
Our ride height gauges are wedges with the different vertical measurements spread out along a surface that isn't terribly far from horizontal. Because of this it tends to make things like a quarter millimeter (.25mm / .001") look REALLY BIG because of that misleading-appearing spread. Again, perspective.
Back to rotating the tires relative to Chris' "sweet spot". I find that if I rotate the tires after the first round of qualifying (one heat "off" even wear) and then run them two more heats there (one heat back to even, one heat "off" wear), then rotate them back again for the main that my side-to-side wear is generally very very close. Is there a "sweet spot" as Chris posits? There probably is, but I keep the difference to such a small level that it SHOULD be inconsequential.
My "routine" between heats includes tweaking, and I tweak for how the car will START the heat. I don't believe I see enough tire wear to make a substantive difference in tweak and/or handling, but even if I DID my car is starting the heat as "on" as I can make it and if the car changes it does so gradually (and similarly) each heat and would be easily compensated for. It's all going one way. If you were trying to "lead" the sweet spot you'd have the handling going one way as the wear caused things to head toward optimum, that brief moment of absolute perfection (because you WERE driving like a star and didn't hit anything) at mid-race, then the handling would go the other way as you departed that perfection. In theory.
I make any repairs or adjustments, rotate tires (if due), tweak the car on my scales, pookie the tires, go race. In that order every time.
I rotate my tires side-to-side during the race day and find that this does a very good job keeping my tires reasonably even. RARELY do I find the tires to be even .25mm off from each other after a heat where they started even, but let's pretend I did.
.25mm is roughly equal to 1 hundredth of an inch. That's damn small. NOW, divide by two because that's how much a .25 diameter change affects relative height of a corner. So now we're talking about .125mm or 5 thousandths of an inch. That's REALLY damn small. Can that difference be measured in tweak? I'd offer that it's unlikely with any but the absolutely most sensitive methods (which I'd argue my scales to be) and maybe not even then.
Our ride height gauges are wedges with the different vertical measurements spread out along a surface that isn't terribly far from horizontal. Because of this it tends to make things like a quarter millimeter (.25mm / .001") look REALLY BIG because of that misleading-appearing spread. Again, perspective.
Back to rotating the tires relative to Chris' "sweet spot". I find that if I rotate the tires after the first round of qualifying (one heat "off" even wear) and then run them two more heats there (one heat back to even, one heat "off" wear), then rotate them back again for the main that my side-to-side wear is generally very very close. Is there a "sweet spot" as Chris posits? There probably is, but I keep the difference to such a small level that it SHOULD be inconsequential.
My "routine" between heats includes tweaking, and I tweak for how the car will START the heat. I don't believe I see enough tire wear to make a substantive difference in tweak and/or handling, but even if I DID my car is starting the heat as "on" as I can make it and if the car changes it does so gradually (and similarly) each heat and would be easily compensated for. It's all going one way. If you were trying to "lead" the sweet spot you'd have the handling going one way as the wear caused things to head toward optimum, that brief moment of absolute perfection (because you WERE driving like a star and didn't hit anything) at mid-race, then the handling would go the other way as you departed that perfection. In theory.
I make any repairs or adjustments, rotate tires (if due), tweak the car on my scales, pookie the tires, go race. In that order every time.
Tech Champion
iTrader: (261)
Sorry Chris, but unless you have a cross-over a la Suzuka (or an intersection ) in your track or a hill-climb style (or rally stage) layout where your start and finish do not connect up you will ALWAYS have more turns one way than the other. I believe it always adds up to 360* (a complete circle worth) more turns to one side, to the right on a CCW running track and to the left on a CW running track.
I refer to the "outside" as whichever tire is pointing "out" on the exterior straights (most tracks are oriented ***EDIT*** CW which means the left tire). This (at least for me) tends to be the tire that wears more, all things equal.
I refer to the "outside" as whichever tire is pointing "out" on the exterior straights (most tracks are oriented ***EDIT*** CW which means the left tire). This (at least for me) tends to be the tire that wears more, all things equal.
Last edited by Scottrik; 09-08-2009 at 06:35 AM.
Tech Master
At all the tracks that I race at in the UK, they have always been clockwise orientated, so the outside tyres will be the left hand side of the chassis. I run a set of tyres per heat and final, so that's 5 sets. They get rotated from left to right depending on which tyre out of the pair are bigger or smaller diameter. We don't get much time between heats so the first thing I do after a heat is to change tyres, get additive on them, change cells (forgot to do that a couple of times in the past!) and then check for repairs/setup changes. Do like the technical side of RC racing though, hence questions like this have an intrest to me, haha! Cheers, Chris.
Tech Champion
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Sorry Chris--I musta stuttered on that "C" key. I, of course, meant that most tracks run CW, hence the LR being outboard.
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Massami can do it with his left foot while winning a heat in another class. Blindfolded no less.
I agree that it PROBABLY doesn't matter which end. I WOULD say, however, that to do it at the rear requires your rear pod to be PERFECTLY balanced side-to-side, and that balance will change depending on motor used, etc.
In fact, now I'm curious. There is FAR more wire (winds) in a motor now with brushless than there ever was in a brushed motor since those winds now fill the can and the magnet spins. How much weight difference is there between, say, a 17.5 and a 10.5?. Whatever difference would be CLOSE to being centered, but I can't believe it would be exactly, at least not to within the gram or so I tweak the front of my car to prior to heats.
When I build my cars I don't even weigh the rear pod for balance--as far as I'm concerned the tires contact patches are immoveable relative to each other, as long as things are pretty close (to keep tire wear even-ish) then it's close enough. So for me
I always do the front wheels which is how I learned.
I saw Mike Blackstock set tweak on his car--two coins on the front tires. If it's good enough for Mikey...
I HATED the Hudy tweak stand that came in the "All-in-One" set. Tried it a couple times, wasn't for me. That said, I'm sure there are folks who can make 'em sing...just nobody I've ever met.
I actually use four small scales to set balance or tweak my cars. On the 1/12 car I don't even turn the scales under the rear tires on.
I agree that it PROBABLY doesn't matter which end. I WOULD say, however, that to do it at the rear requires your rear pod to be PERFECTLY balanced side-to-side, and that balance will change depending on motor used, etc.
In fact, now I'm curious. There is FAR more wire (winds) in a motor now with brushless than there ever was in a brushed motor since those winds now fill the can and the magnet spins. How much weight difference is there between, say, a 17.5 and a 10.5?. Whatever difference would be CLOSE to being centered, but I can't believe it would be exactly, at least not to within the gram or so I tweak the front of my car to prior to heats.
When I build my cars I don't even weigh the rear pod for balance--as far as I'm concerned the tires contact patches are immoveable relative to each other, as long as things are pretty close (to keep tire wear even-ish) then it's close enough. So for me
I always do the front wheels which is how I learned.
I saw Mike Blackstock set tweak on his car--two coins on the front tires. If it's good enough for Mikey...
I HATED the Hudy tweak stand that came in the "All-in-One" set. Tried it a couple times, wasn't for me. That said, I'm sure there are folks who can make 'em sing...just nobody I've ever met.
I actually use four small scales to set balance or tweak my cars. On the 1/12 car I don't even turn the scales under the rear tires on.
That leads to the next question: would the ideal 12th scale car have the mass of the motor centered in the rear pod?
Tech Champion
iTrader: (261)
Now you are making me think. In the past I have always used and integy lazer tweak board, there is no question that it gets the cross weights equal, which is what I always assumed that is what we were after. IF the rear pod is not equal weights on the rear tires then setting the front tires to equal weights would be setting the car up with unequal cross weights, which I have assumed for 15 years meant "tweaked".
That leads to the next question: would the ideal 12th scale car have the mass of the motor centered in the rear pod?
That leads to the next question: would the ideal 12th scale car have the mass of the motor centered in the rear pod?
Would the "ideal" 1/12 have the motor mass perfectly centered? I would argue that the ENTIRE mass of the pod assembly would ideally be balanced side-to-side. I need to check into this, but I'd wager that our brushed motors are now more different in mass from different winds within the same manufacturers lineup. If that's the case, the centering and effect on balance would change with each different wind. Then you run into differences between manufacturers and different lines of motors and you're into a whole 'nuther realm of question. In the end, I honestly don't spend any time trying to balance the rear pod. I balance everything on the front chassis plate when I build the car and (effectively) tweak from the front with the rear sitting across the fixed bar.
Tech Regular
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To me, the whole key is that the rear tires are absolutely fixed relative to each other so I'm not entirely convinced the whole "cross weights" thing exactly fits in it's entirety. Pseudo cross weights certainly, but changing at the front. In a stock car (or similar) the rear axle fixes the rear camber relative to each other, but it doesn't have the substantial mass of the car (motor/axle/gearing/hubs/pod) fixed on it and moving on a single pivot.
Would the "ideal" 1/12 have the motor mass perfectly centered? I would argue that the ENTIRE mass of the pod assembly would ideally be balanced side-to-side. I need to check into this, but I'd wager that our brushed motors are now more different in mass from different winds within the same manufacturers lineup. If that's the case, the centering and effect on balance would change with each different wind. Then you run into differences between manufacturers and different lines of motors and you're into a whole 'nuther realm of question. In the end, I honestly don't spend any time trying to balance the rear pod. I balance everything on the front chassis plate when I build the car and (effectively) tweak from the front with the rear sitting across the fixed bar.
Would the "ideal" 1/12 have the motor mass perfectly centered? I would argue that the ENTIRE mass of the pod assembly would ideally be balanced side-to-side. I need to check into this, but I'd wager that our brushed motors are now more different in mass from different winds within the same manufacturers lineup. If that's the case, the centering and effect on balance would change with each different wind. Then you run into differences between manufacturers and different lines of motors and you're into a whole 'nuther realm of question. In the end, I honestly don't spend any time trying to balance the rear pod. I balance everything on the front chassis plate when I build the car and (effectively) tweak from the front with the rear sitting across the fixed bar.
However, when I think back to the old days when I was running carpet oval with a Delta Villain, we would fine tune the corner speed with cross weights and you could defiantly tell the difference. From my experience cross weights do make a difference and should be the ideal way to set “tweak”.
A bit of theory for all of you. Let's start by saying tweak and crossweight are the same thing.
Tire size and tweak. Yes, if the tires wear unevenly this can cause tweak. However, if the front and rear tires are wearing unevenly left to right at the same rate, tweak will not be affected at all. All that changes is stagger and ride height left to right. While this is rarely the case, it still greatly reduces the rate of tweak change.
Effects of tweak. For clarity, please understand that I am talking about SMALL amounts of tweak here, not large amounts. Because we run road courses, we usually want no tweak in the car. Because of this, people seem to think that the slightest amount of tweak means a terrible handling car. This is not always the case. The only thing a SMALL amount of tweak will really do is cause the car to have slightly more steering in one direction, slightly less steering in the other direction. I'm not saying this condition is desirable but it is not always a problem for a skilled driver and not always noticeable for a less skilled driver. While I have never intentionally tweaked a 1/12th I have often put tweak in the car in other classes. I can't tell you how many 1/8th onroad tracks I have run where all the right handers are fast sweepers and all the left handers are hairpins. On occasion (only sometimes) I have found that putting a little tweak in the car has helped me get a better handling car. But like I said, I haven't done it for 1/12th as I have yet to find a track where it would work. If I ever do find one where I need more steering in ALL the lefts and less in ALL the rights or vice versa, I just might do it. If you think I'm nuts, I will point out that Mario Andretti was famous for doing this (and stagger) in Formula 1. It didn't work at every track but it was a big advantage at the tracks it did work on.
Static weight (balance) effects tweak. Take a car that is perfectly balanced and all the corner heights are even, in other words the front axles are at the same height, springs are even, pod is level with the chassis, etc. This car should have no tweak at all. Now put a great big heavy ass chunk of lead on the far left side of the pod right under the axle. Despite the fact that the corner heights haven't changed because the weight is right under the axle and therefore not affecting any of the car's springs, it will still have tweak in it now if you use four scales to check it. There will be more weight on the left rear than the right rear. If you check the tweak from the front either by lifting the front or with a tweak bar at the front, it will still show level but if you check it from the rear, it will show tweak. You would see the same thing only in reverse if you could hang a big weight from the bottom of one front kingpin. This, to me is the main reason for wanting a balanced pod. It makes getting even tweak much easier. That being said, I'm like Scottrik. As long as it's close, I'm happy.
Different motors and pod balance. While I haven't weighed any of them, I imagine different winds would weigh different. This will not affect balance if the cg of the motor is right on the centerline of the rear tires. All that changes is the total weight. If the motor's cg is offset from the centerline, balance and tweak will be affected. Since there are probably slight differences in cg between different brands (and maybe different winds of the same brand) and different cars may have slightly different mounting positions I would suspect that a motor change will affect balance and tweak, but it's probably small enough not to matter too much.
Tire size and tweak. Yes, if the tires wear unevenly this can cause tweak. However, if the front and rear tires are wearing unevenly left to right at the same rate, tweak will not be affected at all. All that changes is stagger and ride height left to right. While this is rarely the case, it still greatly reduces the rate of tweak change.
Effects of tweak. For clarity, please understand that I am talking about SMALL amounts of tweak here, not large amounts. Because we run road courses, we usually want no tweak in the car. Because of this, people seem to think that the slightest amount of tweak means a terrible handling car. This is not always the case. The only thing a SMALL amount of tweak will really do is cause the car to have slightly more steering in one direction, slightly less steering in the other direction. I'm not saying this condition is desirable but it is not always a problem for a skilled driver and not always noticeable for a less skilled driver. While I have never intentionally tweaked a 1/12th I have often put tweak in the car in other classes. I can't tell you how many 1/8th onroad tracks I have run where all the right handers are fast sweepers and all the left handers are hairpins. On occasion (only sometimes) I have found that putting a little tweak in the car has helped me get a better handling car. But like I said, I haven't done it for 1/12th as I have yet to find a track where it would work. If I ever do find one where I need more steering in ALL the lefts and less in ALL the rights or vice versa, I just might do it. If you think I'm nuts, I will point out that Mario Andretti was famous for doing this (and stagger) in Formula 1. It didn't work at every track but it was a big advantage at the tracks it did work on.
Static weight (balance) effects tweak. Take a car that is perfectly balanced and all the corner heights are even, in other words the front axles are at the same height, springs are even, pod is level with the chassis, etc. This car should have no tweak at all. Now put a great big heavy ass chunk of lead on the far left side of the pod right under the axle. Despite the fact that the corner heights haven't changed because the weight is right under the axle and therefore not affecting any of the car's springs, it will still have tweak in it now if you use four scales to check it. There will be more weight on the left rear than the right rear. If you check the tweak from the front either by lifting the front or with a tweak bar at the front, it will still show level but if you check it from the rear, it will show tweak. You would see the same thing only in reverse if you could hang a big weight from the bottom of one front kingpin. This, to me is the main reason for wanting a balanced pod. It makes getting even tweak much easier. That being said, I'm like Scottrik. As long as it's close, I'm happy.
Different motors and pod balance. While I haven't weighed any of them, I imagine different winds would weigh different. This will not affect balance if the cg of the motor is right on the centerline of the rear tires. All that changes is the total weight. If the motor's cg is offset from the centerline, balance and tweak will be affected. Since there are probably slight differences in cg between different brands (and maybe different winds of the same brand) and different cars may have slightly different mounting positions I would suspect that a motor change will affect balance and tweak, but it's probably small enough not to matter too much.
i just got an associated rc12l4 factory team kit nib for $50..it's still competitive right ? what would be a good servo for it ? thanks