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Old 06-08-2012, 07:16 AM   #2866
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I didn't say that belts have something to do with torque steer - they don't, that's why they're used altough they've worse efficiency than shaft drive.

Thats debatable!!

I think smaller module is possible - You can use gears, for example, from Tamiya TA06 - 52T diff gear, 25T (i think) pinion. FGX have differential mounted in excentric mounts, why don't use them? Or it's not possible? I don't have FGX yet, but i want to try it.
When you get your FGX you will see that it is not that simple, the shaft gears are pin driven on the inside and outside gears. The eccentric adjusters are just for gear mesh, not enough movement to be able to adjust belt tension. So you dont own an FGX yet Since i have literally thousands of laps with this car my experience probably goes a bit more than yours and i only say that because you are speculating on what the problem is yet you dont even have nor driven the car. You are right that if 3R had released the car with all 64p gears the issue may not be as noticeable but even with 64p gears you still have 3 power transfers and 4 bearings more than a DD car, no way that will equal out. As i stated earlier i have eliminated 1 transfer and two bearings. The "inefficiency" of the belts is not equal to what i have eliminated, simple fact. And judging by how it feels on the street right now it is not a step backwards! my next event is thursday so we will see.
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Old 06-08-2012, 09:39 AM   #2867
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When you get your FGX you will see that it is not that simple, the shaft gears are pin driven on the inside and outside gears.
Gears, which I'm talking about, are pin driven too.. And if they didn't - it's rekative easy make gear for pin... Or new shaft.

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The eccentric adjusters are just for gear mesh, not enough movement to be able to adjust belt tension.
I was talking about gear mesh with other than original gears.

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As i stated earlier i have eliminated 1 transfer and two bearings. The "inefficiency" of the belts is not equal to what i have eliminated, simple fact. And judging by how it feels on the street right now it is not a step backwards! my next event is thursday so we will see.
Yes, you did, but you added 3 more bearings for tensioning and one bend.

Well for other thinks I don't have enough arguments.. Fact is that experiences from other types of cars are not enough if I don't have car yet. But it does't mean that I can't be right.
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Old 06-08-2012, 09:55 AM   #2868
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I've designed belt and chain drive systems for uses up to 2200 hp as well as gear sets. I can tell you that mechanically a gear is very hard to beat. Belt tension adds a side load to the bearings that a gear doesn't and that tension means a loss of efficiency. A chain drive when done properly has less friction losses than a belt believe it or not but the shear weight of a chain means it too incurs losses that ultimately are greater than the losses of a belt. Different belt systems such as cogged or v belts has different levels of efficiency with cogged as in rc being the least parasitic. A belt is very smooth and quiet though which is nice. Keep in mind the difference here from a mechanical aspect may be 96%-97% vs 97%-98%.

In an application such as these cars, the entire drive train from pinion to diff gear if probably 95% or more so mechanically efficient with the biggest loss in the system being the 32 pitch diff and idler gears. From a pure mechanical efficiency standpoint I don't see how a belt in this location is any more efficient than a simple gear which is very low loss. It doesn't mean it doesn't feel different though. A belt is going to contribute to more inertial forces on the chassis since it is rotating in the same direction as each pulley unlike the counter rotation of the gear it replaced. The nice thing about a belt is that it always has constant contact with the pulleys rather than individual teeth sliding up against and then off another tooth on another gear so they are very smooth.

I actually do like belt drives in certain situations and there are valid reasons to use them but from a mechanical efficiency standpoint you just aren't going to beat the simple straight cut gear.
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Old 06-08-2012, 11:35 AM   #2869
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Gears, which I'm talking about, are pin driven too.. And if they didn't - it's rekative easy make gear for pin... Or new shaft.



I was talking about gear mesh with other than original gears.



Yes, you did, but you added 3 more bearings for tensioning and one bend.

only one of those bearings actually touches the belt and its very loose, only used to get more "wrap" around the pulleys, what you see has not been on the track yet and will more than likely change

Well for other thinks I don't have enough arguments.. Fact is that experiences from other types of cars are not enough if I don't have car yet. But it does't mean that I can't be right.
That is true but while you are speculating i am actually already applying to the car and have feedback!! hard to argue with experience
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Old 06-08-2012, 11:43 AM   #2870
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I've designed belt and chain drive systems for uses up to 2200 hp as well as gear sets. I can tell you that mechanically a gear is very hard to beat. Belt tension adds a side load to the bearings that a gear doesn't and that tension means a loss of efficiency. A chain drive when done properly has less friction losses than a belt believe it or not but the shear weight of a chain means it too incurs losses that ultimately are greater than the losses of a belt. Different belt systems such as cogged or v belts has different levels of efficiency with cogged as in rc being the least parasitic. A belt is very smooth and quiet though which is nice. Keep in mind the difference here from a mechanical aspect may be 96%-97% vs 97%-98%.

In an application such as these cars, the entire drive train from pinion to diff gear if probably 95% or more so mechanically efficient with the biggest loss in the system being the 32 pitch diff and idler gears. From a pure mechanical efficiency standpoint I don't see how a belt in this location is any more efficient than a simple gear which is very low loss. It doesn't mean it doesn't feel different though. A belt is going to contribute to more inertial forces on the chassis since it is rotating in the same direction as each pulley unlike the counter rotation of the gear it replaced. The nice thing about a belt is that it always has constant contact with the pulleys rather than individual teeth sliding up against and then off another tooth on another gear so they are very smooth.

I actually do like belt drives in certain situations and there are valid reasons to use them but from a mechanical efficiency standpoint you just aren't going to beat the simple straight cut gear.

That is true but every idler gear you add has two points of contact, 1:1 you probably cant beat it but when you start adding gears especially with different pitches your efficency goes out the door. When i get done with the final version there will be little if any at all side load on the bearings because the belt will be loose like on a TC. I will say this that as it sits it spins more free with the belts than it did with the gears and what i mean by that is simply spinning the rear wheels takes less effort and it spins longer so that has to mean something. I do agree that a light weight chain would be great.

Fred do you remember when the belt driven oval cars dominated the direct drive classes years ago (may even still be that way) In oval its an efficiency game especially in the stock classes, I am sure there is a reason for that dominance!
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Old 06-08-2012, 11:57 AM   #2871
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Are you sure? Then why every DD car have gears not belt? In TC belts are used because of no torque steer... Maybe gears are little less efficient under big torque, but for higher speeds with less torque are more efficient... I think biggest problem of FGX is big module, with m0.4 or 48dp on all gears it would be much better... But it's only my opinion, let's see how will be your belt drive on track
Hyperdrive used to make pan cars with belts and conversion kits for existing pan cars to use belt drive. They were really popular with the oval crowd because the motor could be moved to the left hand side of the pod.
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Old 06-08-2012, 11:20 PM   #2872
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Hey what can I try to stop the car from spinning out off power into sweepers, running the kit chassis with alu bulkheads, pit shimizu tires med front soft rears.
I had to adjust the steering exp and take some dual rate out until the car made it through the sweeper without lifting.
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Old 06-09-2012, 12:36 AM   #2873
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There is also a way to trim the existing gearsets to make them more efficient: you can trim the two sides of the teeth at an angle, and reduce their widths on all the gear's contact points. It should eliminate much of the grinding gear noise, and increase efficiency with reduced rotational mass. Hirosaka pinion gears feature these angled cuts for improved efficiency, but you must first identifie the contact points between the gears before you trim and polish... Even the pinion gear can be trimmed or you can get the Hirosaka ones, but they are pretty expensive...... You probably will not be able to match 64p gear efficiency but it'll be better than stock for sure, specially if you add ceramic Bearings to the mix..... Checkout the hirosaka gear's angle cut to have an idea how to cut them with a dremel, at teampowers.com . I takes a long time to do, but it's well worth it: I've done it in my mini M03,and it quieted my Car's drivetrain to a whistle, no more crackle and pop..... In addition you can spray some teflon onto the gears after polishing them, so they can really be slippery.... Good luck, I know I'll be doing all of this when the time comes.....
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Old 06-10-2012, 02:48 PM   #2874
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17 F1 RC Cars Racing Simultaneously

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


Here was my maiden run with the FGX, kit setup. It felt ok out of the box, but with an FDR of 5.4 (against 3.72 of the direct drive), it was off the pace. Not sure if I want to increase the FDR as we run 15 minutes with 540 johnson motors. It might burn up.

But will take some time to tune it and see how it does in the next race.

And with 17 cars on track, I was afraid of breaking the car and let everyone pass me left and right
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Old 06-10-2012, 03:15 PM   #2875
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that nitro needs a tune BAD. looks like a fun race still
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Old 06-10-2012, 08:16 PM   #2876
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Originally Posted by fredswain View Post
I've designed belt and chain drive systems for uses up to 2200 hp as well as gear sets. I can tell you that mechanically a gear is very hard to beat. Belt tension adds a side load to the bearings that a gear doesn't and that tension means a loss of efficiency. A chain drive when done properly has less friction losses than a belt believe it or not but the shear weight of a chain means it too incurs losses that ultimately are greater than the losses of a belt. Different belt systems such as cogged or v belts has different levels of efficiency with cogged as in rc being the least parasitic. A belt is very smooth and quiet though which is nice. Keep in mind the difference here from a mechanical aspect may be 96%-97% vs 97%-98%.

In an application such as these cars, the entire drive train from pinion to diff gear if probably 95% or more so mechanically efficient with the biggest loss in the system being the 32 pitch diff and idler gears. From a pure mechanical efficiency standpoint I don't see how a belt in this location is any more efficient than a simple gear which is very low loss. It doesn't mean it doesn't feel different though. A belt is going to contribute to more inertial forces on the chassis since it is rotating in the same direction as each pulley unlike the counter rotation of the gear it replaced. The nice thing about a belt is that it always has constant contact with the pulleys rather than individual teeth sliding up against and then off another tooth on another gear so they are very smooth.

I actually do like belt drives in certain situations and there are valid reasons to use them but from a mechanical efficiency standpoint you just aren't going to beat the simple straight cut gear.
If you had the chance to re do this drive train with a TC3 style gearbox (bevel diff gear and pinion), would that be more effective than the multiple reductions in the FGX?
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Old 06-10-2012, 08:20 PM   #2877
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If you had the chance to re do this drive train with a TC3 style gearbox (bevel diff gear and pinion), would that be more effective than the multiple reductions in the FGX?
Hell yea!! it would be the same as DD except the motor would lay longitudinally, and you would be limited on pinion sizes.
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Old 06-10-2012, 08:24 PM   #2878
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Hell yea!! it would be the same as DD except the motor would lay longitudinally, and you would be limited on pinion sizes.
Shouldn't be limited on pinions with the right motor mount, they are getting huge pinions on VTA TC3s....
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Old 06-10-2012, 08:30 PM   #2879
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Shouldn't be limited on pinions with the right motor mount, they are getting huge pinions on VTA TC3s....

not enough room to setup just like a TC3, it would basically have to be direct from the motor to the dif via beveled pinon and dif gear. Is that how the TC3 is setup?? i though it had the motor driving a spur mounted to the shaft. You would need beveled pinions.
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Old 06-10-2012, 09:47 PM   #2880
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not enough room to setup just like a TC3, it would basically have to be direct from the motor to the dif via beveled pinon and dif gear. Is that how the TC3 is setup?? i though it had the motor driving a spur mounted to the shaft. You would need beveled pinions.
If you have to do it like that, it's not worth it. Yes, the spur is on the shaft.
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