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Old 10-17-2006, 11:55 PM   #6496
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Originally Posted by asw7576
Sorry, I think I have to straighten the CG issue vs weight.

The car CG and RC actually remain the same, CG and RC are just imaginary axis where the car is expected to transfer weight on four wheels. When people change to LiPo, only weight is affected. Lighter cars benefit for acceleration, fuel economy, and more top speed.

Are you saying that by decreasing the weight of the battery pack (changing from nimh to Lipo) does not change the CG?

I forgot to also say to try the rubber belts. They last quite a while (not as long as stock) and free the drivetrain noticably.
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Old 10-18-2006, 12:45 AM   #6497
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Originally Posted by Scott Fisher
Are you saying that by decreasing the weight of the battery pack (changing from nimh to Lipo) does not change the CG?

I forgot to also say to try the rubber belts. They last quite a while (not as long as stock) and free the drivetrain noticably.
Of course, the battery location is fixed. The CG of the car is already fixed ( all hardwares like servos, etc are already place below upper deck ). However I'm not sure with load transfer. Sometimes weight is necessary to make grip. Minor adjustment like changing oil weight maybe needed, but I think it is marginal.... hard to tell until you try it.
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Old 10-18-2006, 01:00 AM   #6498
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You are wrong. The CG of the car is not at all fixed. Changing where the weight is placed (top deck to chassis) will definitely alter the CG. Why do you think when we add weight to the car we don't stick it to the body? Its because you make the car more top heavy.... you would be raising the CG.
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Old 10-18-2006, 01:06 AM   #6499
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Anyone use Mugen Seiki pipe ? Any difference with Novarossi Turbo pipe ?
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Old 10-18-2006, 01:17 AM   #6500
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Quote:
Originally Posted by Scott Fisher
You are wrong. The CG of the car is not at all fixed. Changing where the weight is placed (top deck to chassis) will definitely alter the CG. Why do you think when we add weight to the car we don't stick it to the body? Its because you make the car more top heavy.... you would be raising the CG.
You are 100% correct. Lightening stuff below the CG "centreline" actually raises the CG, but there is an overall benefit of less weight.

But I do agree with you about the Lipos for the MTX4 layout is a waste of money. Better to spend it on Ti pivotballs and screws. Once the car is below 1725g you need to be removing weight from high up to replace with the lead on the chassis, and with the Lipos thats not gonna happen. My NiMh pack is 2 1/2 years old and still kicking.
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Old 10-18-2006, 01:19 AM   #6501
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Originally Posted by asw7576
Anyone use Mugen Seiki pipe ? Any difference with Novarossi Turbo pipe ?
If you mean the 2501 pipe then I have this. Very good pipe overall, however there are some better ones starting to come on the market now.

The new Nova pipe is excellent, and on the Sirio motors the World Champ edition pipe is still an excellent match.
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Old 10-18-2006, 01:25 AM   #6502
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Originally Posted by AMGRacer
You are 100% correct. Lightening stuff below the CG "centreline" actually raises the CG, but there is an overall benefit of less weight.

But I do agree with you about the Lipos for the MTX4 layout is a waste of money. Better to spend it on Ti pivotballs and screws. Once the car is below 1725g you need to be removing weight from high up to replace with the lead on the chassis, and with the Lipos thats not gonna happen. My NiMh pack is 2 1/2 years old and still kicking.
i second this thought.

By all means go Lipo if you have the know how. Yes lighten the car as much as you want since it does wonders to power to weight bla bla..

But! when its comes to racing, its gonna be quite a chore to bring it up to race spec weight of 1725g.

The funny thing is with all the Ti stuffs on mine MTX-4, I still have to add a 5g weight in the bumper to be sure that I am legal.
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Old 10-18-2006, 01:33 AM   #6503
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Originally Posted by Arahawak
i second this thought.

By all means go Lipo if you have the know how. Yes lighten the car as much as you want since it does wonders to power to weight bla bla..
I actually avoided Lipo cause it adds another electrical device into the mix which can be damaged by fuel and/or vibration. I prefer direct connection to servo and battery from receiver which reduces the overall chance of an electronics failure.
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Old 10-18-2006, 02:27 AM   #6504
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Originally Posted by AMGRacer
I actually avoided Lipo cause it adds another electrical device into the mix which can be damaged by fuel and/or vibration. I prefer direct connection to servo and battery from receiver which reduces the overall chance of an electronics failure.
Maybe I'm wrong..... maybe I forget where did I read.....

Someone in this forum actually use direct connection from 7.4V LiPo straight to receiver, and he is doing just fine. Infact his servos run supercharged. I'm not sure what brand of his radio equipments...... I think it was Futaba.

Spektrum receivers are rated up to 9V, but most servos are only tested @ 6V. I have to try it myself ( I don't have LiPo yet ). I'm pretty sure high quality servos could handle extra voltage of 1.4V.
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Old 10-18-2006, 02:33 AM   #6505
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Originally Posted by Scott Fisher
Your car will probably be underweight at that point. If you lighten it at the battery, you will have to add weight back to make it race legal. Guess where the best place to add weight is?

Team drivers have been making brass battery trays to add weight at that spot.
looks like i'll be needing to do this. i'm running a lipo. i lowered the tank by about 2.5mm do you think this will counteract the loss of weight from running a lipo Scott? (i think i am able to lower the tank another 1mm, but that's about it as it will start hitting the pulley, unless i deform the tank towards the front to allow a lower hight.

anyway, is this a good enough countermeasure i am doing?
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Old 10-18-2006, 02:42 AM   #6506
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Originally Posted by asw7576
Maybe I'm wrong..... maybe I forget where did I read.....

Someone in this forum actually use direct connection from 7.4V LiPo straight to receiver, and he is doing just fine. Infact his servos run supercharged. I'm not sure what brand of his radio equipments...... I think it was Futaba.

Spektrum receivers are rated up to 9V, but most servos are only tested @ 6V. I have to try it myself ( I don't have LiPo yet ). I'm pretty sure high quality servos could handle extra voltage of 1.4V.
it's best to use the regulator that VXR makes. it is a 5 amp regulator. i mounted mine on some servo posts on the side on the chassis on the pipe side. i sealed the regulator up with silicone, and the batteru ina balloon
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Old 10-18-2006, 02:55 AM   #6507
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Originally Posted by asw7576
Maybe I'm wrong..... maybe I forget where did I read.....

Someone in this forum actually use direct connection from 7.4V LiPo straight to receiver, and he is doing just fine. Infact his servos run supercharged. I'm not sure what brand of his radio equipments...... I think it was Futaba.

Spektrum receivers are rated up to 9V, but most servos are only tested @ 6V. I have to try it myself ( I don't have LiPo yet ). I'm pretty sure high quality servos could handle extra voltage of 1.4V.
Wow they would sure be supercharged at 7.4v. I certainly would not do that to my equipment, but perhaps I am just too poor
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Old 10-18-2006, 03:12 AM   #6508
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Originally Posted by TomB
looks like i'll be needing to do this. i'm running a lipo. i lowered the tank by about 2.5mm do you think this will counteract the loss of weight from running a lipo Scott? (i think i am able to lower the tank another 1mm, but that's about it as it will start hitting the pulley, unless i deform the tank towards the front to allow a lower hight.

anyway, is this a good enough countermeasure i am doing?
Hey, that was very good idea. I use Lipo and I could lower the fuel tank. The mass is going down to replace lighter battery's mass.

Anyway, here some photo if you load your servo too hard. eg. EPA is not correct making it always try to center or to turn. ( This is @ 4.8V )

Fried FET chips


Fried Coreless Motor's brush


Fried plastic housing to hold the pinion gear.
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Old 10-18-2006, 09:59 AM   #6509
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I didn't realize that lightening the car was this complicated. I know that most of the weight of the car is below the radio tray, so wouldn't using ti pivot balls raise the CG? for that matter, wouldn't all of the after market parts raise the cg since they are mostly below the radio tray-ie-pivot ball, 2 speed shaft, 2spd housing

I guess it's all in compromising and adjusting. What are the lightening products that are just not worth purchasing besides the lipo batt?
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Old 10-18-2006, 10:27 AM   #6510
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Quote:
Originally Posted by blanks596
I didn't realize that lightening the car was this complicated. I know that most of the weight of the car is below the radio tray, so wouldn't using ti pivot balls raise the CG? for that matter, wouldn't all of the after market parts raise the cg since they are mostly below the radio tray-ie-pivot ball, 2 speed shaft, 2spd housing
Nope.. the problem is to know how much you can go without changing radically the way some car handles... lowering too much the CG makes the car nervous and less docile on their reactions.

Changing the pivot balls (steel) for some made on Ti isn't bad at all. But the ones to change them if you plan to lower really the CG are the upper ones, leave the steel on the lower side (the weight is where it doesn't hurts, at the lowest possible on the car).

Also... the Ti pivotballs has a dark side that many people doesn't know or will know someday. Are more prone to break rather than the steel ones (Ti is more brittle than steel). Many people can argue that changing all two you leveage the unsuspended masses, but at which price? At the price of a DNF if you manage to whack the boards and the pilloballs break.

Exchanging parts for aftermarket ones sometimes is due you're searching another side, maybe strengtening, maybe lightening, maybe more adjustability, maybe... the last judge are yourself, think if you really need that part and what advantages and what disadvantages you get changing that part (if not, ask the people).

I repeat what I told in the past, the unique part that's really needed for a MTX-4 straight out of the box are the front CVD's no more no less. Adding the Ti screwset you remove a nice quantity of grams on the best place you can do (on the highest part of the car).
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