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Old 12-15-2011, 02:11 AM   #46
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YR4dude: I do hear your concern about the chassis flex and the gear mesh. Getting the gear mesh just right will be a bit of a challenge.. but I think with the right top braces I'm hoping I will be able to keep the gear mesh from changing due to chassis flex.
You should definitely use drive cups and not fix the shaft directly to the gears. You want chassis flex for a nice neutral car and a wide setup window (which is why all modern TCs have lots of flex).

The only TC with a shaft directly attached to the gears was the TTech Predator, and that got through gears at a massive rate, even though it had a fairly stiff tub chassis and we were running quite slow motors at the time.
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Old 12-15-2011, 03:53 AM   #47
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OK, shaft drive resistance increases with speed, belt resistance reduces with speed.

The noticeable difference between shaft and belt drive cars is out of corners beyond that there is no noticeable difference in accelleration hence efficiency difference at speed become quite close. So yes on most tracks overal shaft drive is probably more efficient but by how much.
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Old 12-15-2011, 07:33 AM   #48
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Cool Project!! I love my TC3 for VTA but the only challenge (not a big issue) is proper brushless gearing due to the 2.5:1 ratio between the ring gear and pinion compared to modern belt driven cars.

Have you been able to duplicate the 2.5:1 ratio with your rear drive belt pulleys so to not over or under drive the front wheels?

Keep posting your progress!
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Old 12-15-2011, 04:58 PM   #49
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After taking everyone's advice and comments into mind..I'm starting to think this could be too complicated of a design...and as YR4dude said.. a bit of a undertaking for the tools I have...

If I could make it happen and still keep the COG low and chassis flex good.. what do you guys think of a single belt, centralized battery and motor car using a shorty pack?

I'm not ditching the two belt , one shaft idea yet.. just considering my options..
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Old 12-15-2011, 06:24 PM   #50
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Originally Posted by eds24 View Post
After taking everyone's advice and comments into mind..I'm starting to think this could be too complicated of a design...and as YR4dude said.. a bit of a undertaking for the tools I have...

If I could make it happen and still keep the COG low and chassis flex good.. what do you guys think of a single belt, centralized battery and motor car using a shorty pack?

I'm not ditching the two belt , one shaft idea yet.. just considering my options..
You read my mind on the single belt shorty pack design! I was looking at an old Kawada single belt design this afternoon thinking how it could b updated. I'd like to see it...
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Old 12-15-2011, 08:55 PM   #51
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lots of helpful opinions here but i think you will be fine if you just stick to your plan. though id allow for the use of front/rear drive cups on the shaft just so things can flex freely. not too complicated a project if you have a drillpress and possibly a jigsaw/highspeed router.

Id make parts out of plastic until you get what you want then if you know someone with a cnc you can get them in nicer material.
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Old 12-16-2011, 03:16 AM   #52
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i think what you are doing is really great. i know you will need to spend a lot of money to get this custom car going, but trust me, designing something yourself is very satisfying. i cant stand the design and placement of motors and batteries of todays cars, and to me its like something is not right with placing the motor way to the left and then balancing it with the batteries on the right, with nothing heavy going through the center of the car ! Thats one of the reasons i still drive my Kawada SV-10 Alcyon II, a car that is similar to the X ray T1 and TRF414M2. I can run a ball diff in front with only 2 degrees of rear toe, and still able to brake like hell without looping out,something the 415 type cars cant seem to do. The 415 Type Car owners keep telling me i cant use a ball diff in front, cause it will cause the rear to loop out under hard braking, they tell me i must have spools or a very tight gear diff in front and at least 3 degrees of toe in in the rear to be able to brake hard from high speed. i have modified my car to place the servo more forward and the ESC too, so that i can move the saddle packs more forward. Originally it was a 100g heavier at the rear, something rather common in the old 414 type of cars, becuase of the rear motor placement. With my moodifications i managed to cut down rear weight bias to 30g. No doubt your project car will be 50-50 F/R.
Who knows within 2 years time, the top manufacturers may be copying YOUR design. I beleive this is a step in the right direction to move away from the often copied 415 layout.
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Old 12-16-2011, 05:30 AM   #53
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Originally Posted by PitNamedGordie View Post
You read my mind on the single belt shorty pack design! I was looking at an old Kawada single belt design this afternoon thinking how it could b updated. I'd like to see it...
if you are talking about single belt, the Kyosho KX-one would be better than the Kawada SV-10 Sigma.
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Old 12-16-2011, 06:58 AM   #54
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The single belt design isn't really compatible with a central motor layout. You're going to have to send the belt over the motor, which is going to mean either having the layshaft above the motor, or at the very least pulleys and rollers above the motor, raising the CoG.

The best design I've seen so far is Marcels TCX. With modern Lipo power and brushless motors the extra bit of friction from the third belt is unlikely to be a big issue in anything but the slowest of classes. Certainly in 10.5 boosted which I race, the car is still accelerating at the end of the straight, so the significant factors are car weight and motor torque, not drivetrain efficiency.

http://ets.redrc.net/gallery/?nggpage=4

I think the current twin-belt design is still a hangover from when we were running NiMh cells with concerns of dumping, so the cars were optimised towards an efficient transmission. No manufacturer has yet to make a TC properly designed for Lipo and brushless... but it'll come sooner or later, and we may well find the manufacturers copying the pioneers here on RCTech
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Old 12-16-2011, 11:11 AM   #55
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The the advent of shorty packs, I wouldn't be all too surprised if Losi took their JRX-S, designed it for a shorty pack in the middle, then moved the motor forward. That might even leave room for the ESC to sit behind the motor. The only piece on that car that wouldn't be on the center line would be the receiver, and you might be able to squeeze it next to the ESC anyway.
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Old 12-16-2011, 03:20 PM   #56
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I would like to say thank you to you all for providing input and farther input would be greatly appreciated! There is a lot of knowledge floating around rctech..and I'm enjoying discussing all this with you guys.

Quote:
Originally Posted by PitNamedGordie View Post
You read my mind on the single belt shorty pack design! I was looking at an old Kawada single belt design this afternoon thinking how it could b updated. I'd like to see it...
I'm glad that I'm not the only one with this idea... I have been digging up pictures of the Kawada and the Kyosho KX-One for reference. I have also been researching the faults of each.

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Originally Posted by valk View Post
lots of helpful opinions here but i think you will be fine if you just stick to your plan. though id allow for the use of front/rear drive cups on the shaft just so things can flex freely. not too complicated a project if you have a drillpress and possibly a jigsaw/highspeed router.

Id make parts out of plastic until you get what you want then if you know someone with a cnc you can get them in nicer material.
A abit of difficulty is added with the addition of front and rear drive cups. This means instead of having to make one shaft..which I almost have done.. I would have to make a custom shaft..that would plug into the drive cups or modify a tc3 or tc4 drive shaft...then I would have to make two drive cup shafts..and figure out a different mounting system for the drive cup shafts since they require two bearings for stability. That mounting system would have to hold the shaft at exactly the right height. The mounting system also has to be mounted in exactly the right location in order to achieve perfect mesh. Phew...sounds like a bit of work compared to bolting the gears directly on a shaft..and having one bearing at each end and supporting it by identical E4 lay shaft holders and worrying about mesh. Unfortunately, like you and others have said it is crucial to have drive cups to allow for flex. Like I said the more I look at the design and more it looks too complicated to me...with the addition of the drive cups. I'm not sure with my drill press and a few hand tools I can obtain the accuracy that would be needed for a drive shaft system.

I hadn't factored in drive cups when I came up wit the design haha From my past projects I have learned to try and keep it simple.. possible a single belt system would be simpler.

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Originally Posted by alcyon View Post
i think what you are doing is really great. i know you will need to spend a lot of money to get this custom car going, but trust me, designing something yourself is very satisfying. i cant stand the design and placement of motors and batteries of todays cars, and to me its like something is not right with placing the motor way to the left and then balancing it with the batteries on the right, with nothing heavy going through the center of the car ! Thats one of the reasons i still drive my Kawada SV-10 Alcyon II, a car that is similar to the X ray T1 and TRF414M2. I can run a ball diff in front with only 2 degrees of rear toe, and still able to brake like hell without looping out,something the 415 type cars cant seem to do. The 415 Type Car owners keep telling me i cant use a ball diff in front, cause it will cause the rear to loop out under hard braking, they tell me i must have spools or a very tight gear diff in front and at least 3 degrees of toe in in the rear to be able to brake hard from high speed. i have modified my car to place the servo more forward and the ESC too, so that i can move the saddle packs more forward. Originally it was a 100g heavier at the rear, something rather common in the old 414 type of cars, becuase of the rear motor placement. With my moodifications i managed to cut down rear weight bias to 30g. No doubt your project car will be 50-50 F/R.
Who knows within 2 years time, the top manufacturers may be copying YOUR design. I beleive this is a step in the right direction to move away from the often copied 415 layout.
I agree with you , I have built a few other cars myself and it is a very satisfying feeling once you finish and are able to take your creation to the track knowing that their isn't another car out there like yours.

It also bothers me the current design of the weight distribution of touring cars these days.. it makes sense..but at the same time it doesn't and that would be why I'm searching for a better design.

Thank you for your feedback on the Kawada SV-10 Alcyon II.. it is great to hear your success with it.

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if you are talking about single belt, the Kyosho KX-one would be better than the Kawada SV-10 Sigma.
I don't know a great deal about either of these cars.. could you please expand on why the Kyosho is better?

Quote:
Originally Posted by daleburr View Post
The single belt design isn't really compatible with a central motor layout. You're going to have to send the belt over the motor, which is going to mean either having the layshaft above the motor, or at the very least pulleys and rollers above the motor, raising the CoG.

The best design I've seen so far is Marcels TCX. With modern Lipo power and brushless motors the extra bit of friction from the third belt is unlikely to be a big issue in anything but the slowest of classes. Certainly in 10.5 boosted which I race, the car is still accelerating at the end of the straight, so the significant factors are car weight and motor torque, not drivetrain efficiency.

http://ets.redrc.net/gallery/?nggpage=4

I think the current twin-belt design is still a hangover from when we were running NiMh cells with concerns of dumping, so the cars were optimised towards an efficient transmission. No manufacturer has yet to make a TC properly designed for Lipo and brushless... but it'll come sooner or later, and we may well find the manufacturers copying the pioneers here on RCTech

I agree that a centralized motor and battery aren't easily compatible with a single belt drive-train. But I do disagree that the entire belt would have to be sent over the motor.. If you look at the Kyosho KX-One and the Kawada the motor and battery are in between the belt. This of course causes concern in the flex of the chassis.. but if I can figure out a way to gain enough flex..but not too much from the layout..I believe it would be a winner.

I have seen pictures of that car and I do give props to the builder its an excellent car. When talking about efficiency I believe its more important to concentrate on acceleration compared to top speed. Of course top speed is important too..but how fast the car can accelerate out of the corners and down the straight determine how fast the car can go...not the motor and battery these days as you stated I believe we can be more efficient than a 3-belt system. As Brian Mcgreevy helped me determine.. a 3-belt system is roughly 61% efficient.

Quote:
Originally Posted by Jato Fox View Post
The the advent of shorty packs, I wouldn't be all too surprised if Losi took their JRX-S, designed it for a shorty pack in the middle, then moved the motor forward. That might even leave room for the ESC to sit behind the motor. The only piece on that car that wouldn't be on the center line would be the receiver, and you might be able to squeeze it next to the ESC anyway.
I agree.. with these new shorty packs.. new possibilities have presented themselves.. so many in fact that ROAR is trying to limit them. It would be interesting to see a JRX-S designed around the Shorty lipo.. and I have no doubt that losi would consider it if and once Roar adjusts their new rule.
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Old 12-16-2011, 03:45 PM   #57
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Originally Posted by daleburr View Post
The best design I've seen so far is Marcels TCX.
agreed. Marcel TCX

apply the schumacher mission belt system to this (using large diameter 40T pulleys that will allow the long belt to wrap everything). now, all those fixtures hanging off the chassis for the side belt go away ...

and honestly, everyone seems obsessed with cramming the weight in widthwise. to do that, it ends up stretching out longitudinally .. and grows the yaw moment accordingly. i think, ideally, the electronics would form a square [ ] with no empty channel in the center for the belt. (reference above thought/design).

at this point, moving things around isn't going to generate a much better car on the track. the current designs are solid from most any dynamic aspect and have proven themselves so. similarly, if we went back to a 414 and it had modern features (nice bulkheads with multiple vertical ball stud locations, diff height adjustments, removable upper halves for diff access/ect) the car would be as good as any today. the high layshaft is insignificant in practicality. people just get caught up in theory and then rest quits making sense.

incidentally, i bought a kx-one some months ago simply because tc is THAT boring right now.
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Old 12-16-2011, 04:02 PM   #58
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agreed. Marcel TCX

apply the schumacher mission belt system to this (using large diameter 40T pulleys that will allow the long belt to wrap everything). now, all those fixtures hanging off the chassis for the side belt go away ...

and honestly, everyone seems obsessed with cramming the weight in widthwise. to do that, it ends up stretching out longitudinally .. and grows the yaw moment accordingly. i think, ideally, the electronics would form a square [ ] with no empty channel in the center for the belt. (reference above thought/design).

at this point, moving things around isn't going to generate a much better car on the track. the current designs are solid from most any dynamic aspect and have proven themselves so. similarly, if we went back to a 414 and it had modern features (nice bulkheads with multiple vertical ball stud locations, diff height adjustments, removable upper halves for diff access/ect) the car would be as good as any today. the high layshaft is insignificant in practicality. people just get caught up in theory and then rest quits making sense.

incidentally, i bought a kx-one some months ago simply because tc is THAT boring right now.
I agree that moving the weight towards the center of the car width-wise does spread it longitudinally...and effects the yaw movement...with regular stick batteries.. but now.. with the new shorty battery packs.. we can pack all the weight on the center line and it be the same length as the current set ups compared to the E4 or the Kyosho Kx-one which stretched the weight out because of regular stick packs.. A few pages back I demonstrated this with the boxs around the components.

I would have to disagree with you about moving the electronics won't effect a car much at this point.. sure maybe this is true with a regular stick pack.. but with short battery packs.. things are changing..and I believe that designs can be better-optimized now with this technology.
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Old 12-16-2011, 04:26 PM   #59
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I would have to disagree with you about moving the electronics won't effect a car much at this point.. sure maybe this is true with a regular stick pack.. but with short battery packs.. things are changing..and I believe that designs can be better-optimized now with this technology.
i don't disagree with that in principal. but getting it to show on the the track will be tough. i applaud your efforts, but i think in the end it's just going to be another way to get it done, not necessarily a better way. 'sall i'm sayin'. especially if you have to find a place to put ballast to account for the weight lost with the shorty pack. then again that's what these mfrs have been selling us for years... 'optimizing'.

again, i'm with you here, but i know that my lust to do things like this stems mostly from boredom and being a nonconformist at heart, not from thinking i'm going to end up with a tangible advantage. it always starts that simple/optimistic .. and as things move forward (as we noted here) you start to consider the (-) tradeoffs to the (+) ones that got you going in the first place. (not altogether different than falling love ... )

keep up the good work. besides, it's all about the process ... not the destination.

good thread. (one of very few)
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Old 12-16-2011, 04:48 PM   #60
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if you are talking about single belt, the Kyosho KX-one would be better than the Kawada SV-10 Sigma.
I have both those cars. The Kawada single belt chassis layout is similar to the Losi XXX-S; battery on one side electronics on the other. The KX-One has the battery and motor centralized. with electronics mounted on pods that hang off on both sides of the battery.

The problem with the KX-One was that there wasn't room for any decent steering gear so it was direct with a servo saver a la 1/12 scale or pan car. Now that there are shorty lipos, that extra space can be used for a steering pivot like the TC6 or slimmer like that on the E4 or even from the Losi JRX.

Honestly, all this talk about drivetrain efficiency really isn't as important as the balance of the car with more centralized mass (ie motor and battery). As said, lipo and brushless have more than enough power to overcome the inefficiency in the drivetrain. Maybe you should reconsider the three belt.

If not then how about old school like the TA-03? 3 gear / belt / 3 gear? Three gear trannies have come a long way since the original MIP tranny for the RC10. The newer ones are lower profile, smaller and lighter.
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