Lazer zx 'S' ??

[Chris Doughty]

the CoG of the motor is central on the xx4 (left/right)

[terry.sc]

Originally Posted by Cockerill

Which recent 4wd's have the motor behind the rear axle???

Nothing since the PB Ace, which was the first to use vacformed lexan covers to seal the alloy gearbox side plates - nothings new.

Originally Posted by Welshy40

You should take a look at the XX4 and you will see. The motor is not bang in the middle, but on the side, as the gearbox is slightly off centre, so it is not perfectly balanced.

The whole point of Losi using three belts (with the extra power loss) in the XX4 was purely to get the motor CoG bang in the centre of the chassis, that's why the primary gearbox is way off centre.

[Welshy40]

Thats funny, so why is the motor not central then?

It isnt in the centre, but off centre, look at the pics on this site (page 7) when the car was reviewed. The motor isnt centre at all. Its cut into the chassis but the end of the motor is further out. It will only be central if the spur gear and gear box unit is right on the very edge of the chassis (which it isnt).

I have raced against these cars and yes they are fantastic and yes its won a worlds, and is better than the rest being made at the moment for balance but still the motor is not as central on the chassis as the ZX, ZXR, ZXS.

[Northy]

Originally Posted by Welshy40

Thats funny, so why is the motor not central then?

It isnt in the centre, but off centre, look at the pics on this site (page 7) when the car was reviewed. The motor isnt centre at all. Its cut into the chassis but the end of the motor is further out. It will only be central if the spur gear and gear box unit is right on the very edge of the chassis (which it isnt).

I have raced against these cars and yes they are fantastic and yes its won a worlds, and is better than the rest being made at the moment for balance but still the motor is not as central on the chassis as the ZX, ZXR, ZXS.

The weight is not central in a brushed motor! Thick about how much the bell end weights compared to the armature!

EDIT plus you have the weight of the slipper assembly to take into account too, thats why the motor is not central in a 2wd, but the overall weight is!

G

[Lee]

Is it totally necessary to have a perfectly balanced car?

I would have thought not, if you have the motor dead centre then it will pivot around that point mid air, it will do it less so if it is further forwards or back.

Also do you see the current crop of shaft drive cars (BJ4/S4) barrel rolling through the air when on power? I haven`t?

Balance plays a part but dont forget these cars have had 100`s of hours of R&D spent on them, everything is at its optimum (within reason) when the cars are released.

[Lee]

The bj4WE is well balanced!

I have balanced it on my head, no problem!!!

[P_B]

Originally Posted by Lee

Is it totally necessary to have a perfectly balanced car?

Balance plays a part but dont forget these cars have had 100`s of hours of R&D spent on them, everything is at its optimum (within reason) when the cars are released.

Good point, Lee. Let's look at a 'real world' alternative example.

Check the chassis layout of an old original RWD, LHD VW Beetle. The majority of it is longitudinally symmetrical. Fore and aft weiight distribution is less so, however the relatively light magnesium alloy cased engine sits over the rear axle and is largely balanced by the fuel tank and spare wheel over the relatively heavy front axle beam arrangement. Even the starter motor and battery are placed so as to offset the mass of the driver.

If you were to measure the corner weights of this old car as opposed to a modern FWD Golf you'd probably find the old bug is (on paper) much more balanced than its descendent. However, give them equal power to weight ratio, braking ability and identically restricted top speeds then lob them down a track or rally stage and the Golf is likely to show a clean pair of heels to the wheezy old fella.

Why? Because the Golf can take advantage of various design advances in suspension geometry, will enjoy a lower centre of gravity, lower polar moment of inertia and so on. Things evolve, develop and move on, designers will compromise on one aspect to exploit others so whatever looks good on paper to an idealistic and fanatical old duffer simply doesn't translate to reality after a sufficient time has elapsed.

The Lazer was a good car, 'was' being the operative word. Pretty much any compromised modern design, shaft or belt will, given equal circumstances, run rings around it. Just my opinion.

[terry.sc]

Originally Posted by Welshy40

Thats funny, so why is the motor not central then?

It isnt in the centre, but off centre, look at the pics on this site (page 7) when the car was reviewed. The motor isnt centre at all. Its cut into the chassis but the end of the motor is further out. It will only be central if the spur gear and gear box unit is right on the very edge of the chassis (which it isnt).

I have raced against these cars and yes they are fantastic and yes its won a worlds, and is better than the rest being made at the moment for balance but still the motor is not as central on the chassis as the ZX, ZXR, ZXS.

The weight in a motor is in the magnets and the armature, so the weight of the motor in a XX4 is centred, check out every 1/12th chassis and compare.
You are contradicting yourself here James, if the XX4 motor isn't centred then it isn't centred in the Lazer either as the motor in the Lazer also has the endbell further out. The motor is positioned in the same place across the chassis in both cars. The ZX-S spur is no further out from centre than the spur in the XX4.

[Welshy40]

Lee

I have seen videos of the shaft cars jump and they dont look too fantastic at high speed, as the cars lean sideways a bit.

The Lazer is better balanced, as you have the batts in front of the motor so it equals it out when jumping.

So if the companys spend hundreds of hours on these cars then how come they come up with the ZX5 which is definately unbalanced on a jump, videos are on Tupe or whatever its called are showing this. Also why the batts on one side as this is also unbalanced. Mmmm me thinks that they dont always spend a lot on R&D, especially if the drivers they used can drive a brick faster than most of us.

The designs that were used at the 2005 worlds showed a proto type made by losi, (from the touring car) and guess what it made the B. This car was similar to the ZXS with the motor in the same place and the layout pretty much the same, ok the batts were laid out like a 2wd, so slightly different.

They only made the proto a few weeks before the worlds and didnt have much time to set it up yet they made the B so if the design is so old as you say how come it made the B?

Its a pitty the company stopped 4wd designing as if they did make it I could see that winning next time around as it was superb. It was a better balanced car than anything I have seen to date including any Lazer and considering they had no time to set it up properly I kindof think they were on the right path. Maybe Gill Losi may use a similar design now he is with Kyosho. Lets hope as this hobby needs a really good car again.

Terry,

I have studied the picture and have also driven one and yes its a fantastic car but I do disagree with you on the position. Even with the layshaft and spur the weight of that isnt enough to counter balance the motor, the motor is not bang central, just because the end bell isnt much weight as well as the front of the motor the mass of the motor is not dead centre like the ZXS or ZX, ZXR. Yes there is a plate with the spur and slipper, but they are very light, which I would guess so is the Losi's Compare the two cars as you will see that the motor position on the Losi is not as central as the ZXS.

[Lee]

Welshy,

Kyosho didnt build the ZX5 to win the worlds, as a standard car it is not capable. it was built IMO to give them something to sell in the growing 4wd market. Maybe they will release a car which has the quality of a tamiya/BJ4 etc etc.

Now when you saw these shaft cars jumping which way did it roll/lean because the way i see it in the bj4 WE, the motor is on the right, but as it spins it rotates anti clockwise so there fore will counter act the extra weight of the motor?

[stegger]

Did i just hear right LEE, your saying TAMIYA make quality cars (not toy's) that's a first coming from you

[Lee]

must of been a slip of the keys

[Chris Doughty]

I recently switched to shaft 4WD, during testing I setup an experiment to show torque twist.

I suspended the car by its shock towers and had no wheels on it, gunned the throttle and hit the brakes and there was a noticeable twist... this is what I expected.
I then did the same thing again but with wheels and tires on the car, and the only 'twist' and reaction was front/back rotation just like all my previous belt cars. the weight of the wheels completely overpowers the motors reaction.
you can also produce a HUGE amount of 'roll' just using small amounts of steering with the front wheels spinning.

I also can't believe how you can find SO many reasons to loosely compare cars to the ZXS. the Losi JRX-4 or Proto-X only similarity is the location of the motor (central and to the rear of the car) the servo in the car is 'backwards' at the front of the car with the steering assembly over the top, the batteries are 'stick' pack that are bottom loaded. the diffs are mega wide with the belts running very much off-centre and it had super short 80's style wishbones. the Losi proto I believe contained lots of 'new' ideas and its downfall was because of the wide and 'big' diffs compromised the length of the wishbones and the height of outdrives.

another thing. I would certainly prefer the components in my car to have their CoG's used to place them as oposed to having them placed spacially just thinking of them as an evenly balanced objects