3 or 4 gear cr2
 

i have an atomic cr2 and I have a normal 3 gear transmission with the external idler conversion and a 4 gear gearbox for it. The only difference in terms of mechanics is the position of the idler. The motor spins in the same direction using either gearbox but the layshaft spins in different directions dependant on which gearbox I use. The effect on handling is dramatic and as I stated the only real difference in the direction of rotation of the layshaft. A lot of other cr2 owners agree. Opinions please ! If the layshaft spinning in the same direction as the tyres makes the car better why do all other manufacturers use 4 gear.

Steel layshaft and a slipper assembly is a lot of rotating mass, so yes it has more effect than people think, i have already done some work on the S2 Evo with a 3 gear gearbox with spur idler ;)

It will be interesting to see the effect it has on the C4.1 / S2 Evo.

Does anybody know if other makers have tried this.
Also does anybody have the motor plate and idler conversion for sale ?.

With my PSI car the 4 gear tranny was better, but its because the motor was sitting farther back more so then what masses where spinning, other with the same car said it got worse with the 4 gear tranny, I guess it would be best to try the 2.

I'll be very interested to see how that goes.

And Adey, you know my opinion - 3 gear box with external idler gear all the way! Possibly not the 'fastest' on a one lapper but far more stable and consistant... much easier to drive a full race with no mistakes. :thumbsup:

The reason I got rid of my C4.1 and went back to my CR2 was because the C4.1 felt wably and unstable - it reminded me of when I tried the 4 geared box in my CR2 last year and I didn't like it. If Jonathon @ AC makes the new S2 Evo available with a 3 gear box and external idler gear I may be interested at trying it again :woot:

As Jonathan stated its down to the rotating mass of the layshaft and slipper assembly. Makes me wonder about the brass flywheel for the x factory x6. Must of made a huge difference.

I've driven a 3 gear cr2 (adey's) and my own 4 gear x6 squared (on carpet)

I felt that adey's cr2 was a much nicer drive.

Is my understanding correct in thinking that 3 gear mid motor is intended for slightly slippier conditions, and 4 gear for higher grip levels?

It is worth mentioning that with a 3 gear cr2 the motor is spinning in the same direction as the layshaft. That must change things as well.

The opposite, 3 gear mid motor is for more steering when you already have enough rear grip, so high grip situations.

I think arransmith27 had it right - having a 3 geared box and external idler gear should be better on lower grip services which has always been my understanding... and today'a racing has definitely confirmed that.

I went over to Coventry astro track yesterday for a bit of practice / testing with my usual 3 geared box and external idler gear... was well until I reallised that the motor plate I was using had lost all its threads were the gearbox bolts to it and so the motor plate was only being held in place by the slipper assembly.

I was due to race at Silverstone indoor offroad meeting today so last night I tried to fix it - however the only other motor plate I had did not have the hole drilled for the external idler gear so I thought I'd give the 4 geared box another try and leave the external idler gear off.

Got there, felt so so in practice... but horrendous through qualifying. At first I thought it was my tires but after putting brand new tyres on and the car still feeling pants, I decided it must be the gearbox. I managed to 'bodge' the 3 geared box back on the car using the fixing for the idler gear as one of the motor screws - not ideal as I could only use a 20 tooth pinion but ran it in the final qualifying (with extra timing/boost speedo settings to componsate for the smaller pinion) and it was SOOOOOOO much better. Not necassarily faster on a 'one lapper' but so much more stable and easier to drive the full race with little or no errors.

Put it 4th in the B final (only running an 8 car A final so 12th overall) and won the B final with no drama's or errors at all.

I should also add that the track was indoor but on propper astro and very loose dirt - astro was very high grip and the loose dirt was oober slippery which was where the time was one or lost.

I know this is a long winded post but for me its the 3 geared box all the way :thumbsup:

I drilled my own motor plate to make my own. The car hasn't been the same using 4 gear really.

Just makes me wonder as all other cars use 4 gear.

I tried drilling the motor plate at the meeting but the drill must have slid a little whilst drilling cos I was about 1mm away from where it should have been and it didn't fit :thumbdown:

I do wonder about other cars with the 4 geared gearbox's... I reckon thats why I didn't like the C4.1 or the original S2 for that matter - I prefer my cars to feel a little more 'sure footed' like the CR2 does.

I'm very keen to see what the S2 Evo will be like if Jonathon lets me have a go with a 3 geared version with external idler gear.

I am sure the car will be good.

Your conclusions for the 3 Vs 4 gear tranny sound strange to me as I experienced the opposite with the X-6.
The first X-6s were 3-gears cars. 4th gear tranny gave the X-6 loads of rear end under power (as it was supposed to) to the point that it became the car to beat on loose dirt, and also a bit understeery on carpet/astro etc.

I'm with Gayo on this.

Yes true but the motor was spinning the wrong way,which is what the four gear transmission altered , exept the layshaft, the cr2 has everything with a large rotating mass spinning the same way ! Or that's how I understand it

I absolutely agree with Wacker on this and it is why I designed Scorpion with an external idler transmission (standard 3 internal gear gearbox + extra idler / 4th gear between pinion and spur).
I found that it made the car FAR more predictable through surface changes and if conditions changed like a downpour.

With the mass of the slipper / layshaft rotating in the the same direction as the rotor, diff/shafts/wheels their is no conflict in torque reaction in the transmission (the two idlers weigh nothing in comparison) and thus the extra consistency.
You would need to change quite a bit of the setup between an internal 4 gear and an internal 3 gear + external idler set up to get the same feeling under acceleration.

Now that said I am not saying the external idler solution is perfect. There are issues regarding covering the idler to keep debris out and I believe that the internal 4 gear might well generate more overall forward drive (for a given setup otherwise). However if like me consistency is the key to good times then I think its hard to beat an internal 3+external idler.

You need to remember that when we talk about 3 gear trannys it is actual a 4 gear tranny as it use's the external idler, so different to a true 3 gear gearbox.

Your experience's with the x6 using a true 3 gear tranny and a 4 gear are the same as what we found with the S2.

OK, I fully understand what you mean now. Interesting!

Can anyone show a pic of an external idler?

Btw I saw the Rudebits make a weighted prop shaft or something on the DB1, is that to counter the motor rotation effect? (side torque)

Yes, so you don't get torque steer. Maybe that's why DB1 handling seems to be so good (never saw one running yet), the motor doesn't affect front-to-rear balance in any way, on or off-power.

An idler setup :

http://www.oople.com/forums/attachme...5&d=1269016178

Any close up of that? Must be quite a bit of mass added!
http://www.rudebits.co.uk/images/OOP...800x600%5D.jpg
-looks like a serious amout of brass on that axle, very smart! :thumbsup:

They also modify the "front slipper diff half" - what is that about?

Some guys did something very similar a couple of years ago, putting a B4 front on a B44 - it was called the B42. Said to be super quick, but only worked on high grip tracks. Of course they didn't do that fancy counter rotating weight thing though.

Does that brass "flywheel" from X-Factory totally eliminate the effect from the motor rotation. And is that a plus on high grip or not?

Wow, does that really make such a big difference! :wtf:

Yes it makes a big difference, think about how much your slipper & layshaft assembly weighs and how far out the mass is from the center of the shaft!

I think you might well be surprised at how little weight has been added to the RudeBits prop shaft.
I can assure you that the amount that has been used would have been accurately calculated based on a lot of parameters and that Dave wouldn't have just plucked a value out of the air! I am afraid that is all I will be drawn into saying about the DB1 transmission as I mustn't give the game away, ask Tony for the rest ... good luck getting the secrets ;)

I think a few people missed the significance of the external idler, here's the configurations listed with the most rear weight transfer (due to power) at the top.

CR2 3 gear (external idler)
X6 / CR2 4 gear
X6 4 gear + brass fly wheel
X6 3 gear

One theory would be that you would go to the top of the list for low traction conditions to get maximum traction out of corners, but I really think this depends on the track / conditions / rest of setup.

I actually prefer the X6 + flywheel in slippier (wet grass) conditions because it smooths out the car through the corner, even though you actually loose straight line grip, it feels better overall. Maybe a more point and squirt track would still be better without the fly wheel.

how exactly does a 3gear CR2 with external idler differ from any other mid mount 4 gear in regards to rear weight transfer?

with a 3 geared box and external idler gear you have the motor, slipper assembly and layshaft, and diff / wheels rotating in the same direction causing more of a 'kick' to the rear end upon acceleration.

When you have a 4 geared box installed you have the slipper assembly and layshaft rotating in the oposite direction which counter-acts the inertia of the motor - this will reduce the 'kick' to the rear slightly upon acceleration and reduce stability and traction slightly.