Six Speed stuff

[Pennyrick]

Some of us stole a thread that was posted about the 2014 models by talking about six speed transmissions. It is a lively topic so I thought I would start a separate thread on this.

I tried to find out what the ratios are for the current SE 5 (or SM 5) tranny on an RT but was not successful. Does anyone know what the ratios are? I am assuming that the fifth gear is a 1:00 to 1:00 (direct) ratio and that first probably starts down around 3:50 or even 3:70 as it feels pretty low.

Randy and Lamont both mentioned going with a six speed tranny that would bring the ratios closer together and that could provide better performance both for acceleration and fuel economy. I would guess that the top gear would no longer be 1:00 to 1:00 but more like .85 to 1:00. (kind of like an overdrive). I'd really like to see the math that would calculate what the speed would be for 5,000 rpm with that kind of top end gearing. My guess is that it would be close to 100 mph.

A large number of transmission ratios means that the engine can operate within a very narrow range of speeds... and the narrower the range the more the engine can be optimized for engine braking on downhills and curves but I really can't see any other advantage using the engine in its' current design.

The Rotax engine seems to have a useable power-band stretching across at least two to three thousand revolutions per minute. Therefore it seems to me that the engine would have to be altered considerably to make use of six speeds (or seven or eight).

I'm certainly not an engineer but maybe there is a SpyderLover who can shed more light on this topic.

 

[billybovine]

Gear Ratio

Here ya go.

 

[Pennyrick]

Here ya go.

View attachment 73873

Thanks, Billy.

I'm not sure I know what I am looking at here. Any ratios I have seen compare to the final drive figure. What does the second number represent?

 

[reverendg]

Those look like actual tooth counts. Primary drive reduces engine rpm 1.935..... to 1. Divide the tooth counts to figure each individual gear multiplier. Looks like first is close to 4 1/2 to 1 compared to engine rpm, and fifth is still very close to 2:1.

 

[Bob Denman]

The numbers: revisited...
Primary reduction: 1.94

1st gear:2.28
2ns 1.47
3rd 1.37
4th 1.13
5th .96

reverse 2.57
You can multiply the primary reduction, by the secondary reduction of the transmission to come up with a "number"
I'm not sure what it would mean without knowing what sort of differesnt gearsets might fit as alternatives... :dontknow:

 

[StanProff]

The numbers: revisited...
Primary reduction: 1.94

1st gear:2.28
2ns 1.47
3rd 1.37
4th 1.13
5th .96

reverse 2.57
You can multiply the primary reduction, by the secondary reduction of the transmission to come up with a "number"
I'm not sure what it would mean without knowing what sort of differesnt gearsets might fit as alternatives... :dontknow:

O.K. you guys, I'm just an observer here. I missed that day in school for sure :dontknow::banghead::shocked::helpsmilie::gaah::cus:

 

[Bob Denman]

Ummm... pps:
Whatt the gear ratios tell you; is kind of how much turning the Crankshaft has to do, in order to turn the wheel once...
The more it has to turn; the more the gears are providing leverage to make the turning less effort... that's lower gearing.
You're always looking for low-enough gearing to allow for decent acceleration in the lower gears, yet still have room on top for a nice top-end speed.
And all of this has to happen without any horrible huge gaps in between the gearing choices. :shocked:
Now that I'm pretty sure that everybody is asleep; can I go throw up? That explanation HURT! :yikes:

 

[Pennyrick]

Ummm... pps:
Whatt the gear ratios tell you; is kind of how much turning the Crankshaft has to do, in order to turn the wheel once...
The more it has to turn; the more the gears are providing leverage to make the turning less effort... that's lower gearing.
You're always looking for low-enough gearing to allow for decent acceleration in the lower gears, yet still have room on top for a nice top-end speed.
And all of this has to happen without any horrible huge gaps in between the gearing choices. :shocked:
Now that I'm pretty sure that everybody is asleep; can I go throw up? That explanation HURT! :yikes:

Excellent, Bob! To steal Randy's phrase, the class can be dismissed. I wasn't aware that fifth gear already had a bit of overdrive in it since the ratio is less than 1 to 1. With fourth at 1:13 to 1:00 that also explains why I can cruise at 60-65 mph in that gear and not feel that I am overworking the engine. I think the 0-60 time on the RT is somewhere around 4.5 seconds so if we stuck another gear in between third and fourth (where I perceive the biggest gap is), I doubt it would improve the time.

Good work.... what an informative site this is.

 

[Bob Ledford]

Bottom line

The bottom line is it will cost more and most of us will still be in 4th gear most of the time

 

[DrewNJ]

It wouldn't be a "gear in between" type of thing. 6th gear would be an additional drop in revs.
Basically, we all know that we only see 5 forward gears having to sacrifice 6th for reverse. Pretty much the same gearbox behind the Aprilia RSV1000 has these ratios:
1st: 34/15 2.27
2nd: 31/19 1.63
3rd: 26/20 1.30
4th: 24/22 1.091
5th: 24/25 0.96
6th: 23/26 0.88

The 5 forward ratios are pretty close to what we see now and yep, we'd still use 4th the most.

So, the real question is: Who's going to be the one to pull their tranny apart and swap in a 6 forward gear gearset and give up reverse??

 

[DrewNJ]

And just for fun....
Here is the spyder tranny gearset
View attachment 73887

And the Aprilia tranny gearset for comparison
View attachment 73888

 

[NancysToy]

Excellent, Bob! To steal Randy's phrase, the class can be dismissed. I wasn't aware that fifth gear already had a bit of overdrive in it since the ratio is less than 1 to 1. With fourth at 1:13 to 1:00 that also explains why I can cruise at 60-65 mph in that gear and not feel that I am overworking the engine. I think the 0-60 time on the RT is somewhere around 4.5 seconds so if we stuck another gear in between third and fourth (where I perceive the biggest gap is), I doubt it would improve the time.

Good work.... what an informative site this is.

Technically the Spyder 5th may be a tiny bit of an overdrive, but in reality it is no overdrive at all...nor would a sixth gear be one. "Overdrive" implies that the transmission output shaft is rotating faster than the engine crankshaft. With the primary gear reduction on the Spyder and most motorcycle engines, the clutch is driven at less than crank speed. For the Spyder that means that the output shaft in high gear rotates at a bit over half the crankshaft speed, not more than crank speed. That increases available torque, and is necessary to move these machines down the road. Wishing for "overdrive" is a fantasy...one can only wish for a slightly more overdriven high gear, not true overdrive like a car might have.

 

[Bob Denman]

Scotty,
Did I get close to the right explanation? :shocked:

 

[NancysToy]

Scotty,
Did I get close to the right explanation? :shocked:

:thumbup:

 

[Bob Denman]

Thanks! :thumbup: I was in WAY over my head; trying to figure out how to say something that I was barely sure of... :shocked: