3 Gear v 4 Gear

[Clive Loynes]

I'm just wondering if all this 3 Gear v 4 Gear business isn't just a load of malarkey!

I just did a few sums and by my calculations if you were running a gear ratio around 9:1 then the three gear inertia effect of the rotor would be just 3.9% of that of the rear tyres on their own never mind the rest of the transmission. At 6:1 it is only 2.6%.

Is that really significant? I doubt that I would be able to tell the difference but perhaps the aliens can!

[danDanEFC]

It's new, it must be better!

[madmax]

The 3 gear box isnt new, you have to remember the atomic carbon cr2 and the origonal x6 where 3 gear but where changed to 4 gear.
as our race tracks have changed over the years the cars have had to as well

[tomtom]

Or the RC10GT with 3 gear mid box

I have to say all the 3 gears cars I've seen around a track all looked very planted.

[Volition]

I noticed more punch with the 3gear compared to the 4 gear on my b5m. I have doubts when people speak about the way the motor rotates and it having an inertia effect. I just think the rotating mass is so minimal & the gyroscope effect both together just is minimal.

Personally I use the 3 gear as default. However, if the track is really slippery I'll put the 4 gear in. It softens the punch and adds weight to the rear at the same time. Yeah I could just add weight I suppose, but because I have both I have to use them, don't I.

If getting a new car I would just get a 3-gear, that's it.

[AntH]

Originally Posted by Clive Loynes

I'm just wondering if all this 3 Gear v 4 Gear business isn't just a load of malarkey!

I just did a few sums and by my calculations if you were running a gear ratio around 9:1 then the three gear inertia effect of the rotor would be just 3.9% of that of the rear tyres on their own never mind the rest of the transmission. At 6:1 it is only 2.6%.

Is that really significant? I doubt that I would be able to tell the difference but perhaps the aliens can!

Don't forget that under hard acceleration there is slipper clutch action, so the speed difference between the wheels and the rotor is bigger than the ratio, probably by quite a lot....

[Clive Loynes]

Originally Posted by AntH

Don't forget that under hard acceleration there is slipper clutch action, so the speed difference between the wheels and the rotor is bigger than the ratio, probably by quite a lot....

Ah, now that's true. Still a very small effect but it wouldn't be masked by the rear axle.

I will have to take a look at the slipper and shaft also, as that will always be acting to reduce the motor inertia but as you say, if the slipper is slipping then it will only be the spur gear that has any effect.

[AntH]

Originally Posted by Clive Loynes

Ah, now that's true. Still a very small effect but it wouldn't be masked by the rear axle.

I will have to take a look at the slipper and shaft also, as that will always be acting to reduce the motor inertia but as you say, if the slipper is slipping then it will only be the spur gear that has any effect.

I think the key question is what is the vertical force change over front & rear axle line under acceleration and what is the variation in that with the different configs. of driveline. Post the math, feed the geeks! (me).

[Clive Loynes]

Originally Posted by AntH

I think the key question is what is the vertical force change over front & rear axle line under acceleration and what is the variation in that with the different configs. of driveline. Post the math, feed the geeks! (me).

LOL

That would take a while as it was only a fag-packet calc. I could probably do a Phd on that topic!

The force that appears at either axle is affected by the moment of inertia for the whole buggy, so a shorty pack down the middle will take more shifting than one that is crosswise in the chassis. I've just changed my layout to an in-line configuration and I love it! It tends to jump flatter, no matter what the pillock on the sticks does!

[Volition]

I wonder!

If you setup your car ready to go. Take the wheels off. Put the rear end on a scale. Hit the throttle. Mm mm I think you would need a logging weight scale.

Worth a shot, trying to think of an experiment to measure the difference.

[dwp102]

I think its more about the touch of those who can feel the difference

[danielc3009]

I've tried both 3 and 4 gear in my b5m on a worn grass track and It does make a difference. I found it was easier to get the power down (mid corner) with the 4 gear but once the car was accelerating (corner exit) I didn't notice any difference, if that makes sense