5 Gears for 500 Quid

[corrado]

Centre punch and blob of red paint, I'll do 2 notches in anticipation of the new 6 speed.

[wrecklessrobbie]

I know what i am about to ask is a stupid question...but
What is the benefit of 5 gears over 4?
Is the 5th gear bigger?
As in it gives more revolutions so higher speeds can be achieved with the same rpms.
Or is it just to reduce jumps between gears so that revs and speed can be maintained?

[drunkmunkey6969]

@wrecklessrobbie - To reduce drops in revs between gear changes, which helps to keep the engine in the peak power area.

An engine might drop 2000rpm between changing from 3rd to 4th, and depending on your power curve....that could, for example, mean you go from 20hp and 15ft-lbs torque at 7500rpm in 3rd gear....to say 10hp and 7ft-lbs at 5500rpm in 4th....that’s when you start to struggle between gear-changes on a steep hill or into a strong headwind.

But if you stick another ratio in the middle to bridge the gap, then you would probably shift from 20hp at 7500rpm in 3rd, to say 15-18hp in 4th, same in 5th....thus staying in the power each time.

There are other options, such as close ratio 4-speed boxes and engines built with the correct cylinder/pipe/carb/ignition/final drive combinations....always more than one way to skin a cat. But a cheaper 5-speed box, if strong and reliable, is an attractive option for sure...

[wrecklessrobbie]

Ok
So it reduces power loss between gear changes.
I know its a good thing.
But i cannot help but think i would prefer a 5 gear that gave more top speed for less revs. I presume that would then lessen crankshaft and top end stress.
Or does this actually do that as well.
Or is it a case of the top speed will always be similar to what it is but it makes it easier to get to the top speed.

I presume they are more suited to top end engine spec scooters than standard ish scooters.

[drunkmunkey6969]

The % drop between 3rd and 4th on some close ratio boxes is not too far away from the % drop on 4th to 5th on some 5 speed boxes....so whatever speed your scooter pulls with a 4 speed, will be very close (probably identical) to what it pulls with a 5 speed using the same final drive.

If you want the same speed at lower revs, fit a tour pipe and up-gear....that job (upgearing) may be made easier by the use of a 5-speed box...but you still need to adjust your peak power RPM point using the appropriate pipe.

[Avantone]

I’d be interested in seeing how they all actually compare on the gearing calculator..number of teeth etc? Same or different to Cyclone, MB and the Tino Satchi one that Robbo is selling ?

I've just uploaded a fresh version of the Visualiser with both versions added and some additional tweaks.

[Minority]

I’d be interested in seeing how they all actually compare on the gearing calculator..number of teeth etc? Same or different to Cyclone, MB and the Tino Satchi one that Robbo is selling ?

I've just uploaded a fresh version of the Visualiser with both versions added and some additional tweaks.

Love your work Tony So useful!!!

[drunkmunkey6969]

Love your work Tony So useful!!!

I’ll second that. All the years I was running the dyno I found this an invaluable tool for showing people, who were seeking advice on gearing, what they should be looking for and how different gearing options would work in their machines.

Great bit if kit

[B1kegrim]

Thanks Tony

I’ll enjoy having a play at that

[Lamaddict]

I was in Rayspeed today and they have sold 40 sets since last Tuesday when they were available. Thoroughly tested and good for standard to tuned motors. Ben has written some comprehensive instructions. I’m tempted myself but run a reasonable close, late Pacemaker box.